CN116314831A - A kind of ternary positive electrode active material and its positive electrode sheet and battery - Google Patents

Abstract

The invention provides a ternary positive electrode active material, a positive electrode plate containing the ternary positive electrode active material and a battery. The cross section of the positive electrode active material particle is a shallow surface layer in the area from the outermost layer to 0-100 nm in the center direction, the shallow surface layer is doped with a metal element M, and the ionic radius of the metal element M is larger than Ni ³⁺ Is a radius of ions of (2); the content of the metal element M on the surface of the outermost layer of the particle is defined as A1, the content of the metal element M at 40nm of the cross section of the particle from the outermost layer to the center direction is defined as A2, and the A1 and the A2 satisfy the following conditions: A2/A1 > 0.7. The ternary positive electrode active material provided by the invention is prepared by doping ions in a shallow surface layerThe metal element M with larger diameter and the content ratio of the metal element M at the doping depth of 40nm of the positive electrode active material particles to the outermost surface of the particles satisfy a certain range, so that the structural stability, capacity and electrochemical performance of the ternary positive electrode active material can be improved.

Description

A ternary positive electrode active material and a positive electrode sheet and a battery containing the same

technical field

The invention relates to the technical field of lithium ion batteries, in particular to a ternary positive electrode active material, a positive electrode sheet and a battery containing the same.

Background technique

Lithium-ion batteries have the advantages of high working voltage, high energy density, long cycle life, no memory effect, small size, light weight, and no environmental pollution. They are widely used in mobile phones, notebook computers, portable electric tools, electronic instruments, and weapons and equipment. etc. It also has a good application prospect in electric vehicles, and has become the focus of research and development all over the world. Lithium-ion batteries are mainly composed of four parts: positive electrode sheet, negative electrode sheet, separator and electrolyte. Among them, the positive electrode active material is one of the important components of the positive electrode sheet and plays a vital role in the electrochemical performance of lithium-ion batteries. .

During the charging process of a lithium-ion battery, lithium ions are extracted from the positive electrode and inserted into the negative electrode, and the process of discharging is just the opposite. Lithium-ion batteries often experience an increase in the transport impedance of lithium ions in the positive electrode active material after many cycles of charging and discharging, and, because the ionic radius of Ni ²⁺ is closer to Li ⁺ , in lithium-ion batteries During the discharge process, when a large amount of Li ⁺ is released from the positive electrode active material, Ni ²⁺ will be affected by external factors and will occupy the position of Li ⁺ in the lattice of the positive electrode active material, resulting in ion dislocation, resulting in Li ⁺ /Ni ^{2 +} Mixing, resulting in changes in the lattice structure in the positive electrode active material, which reduces the ability of the positive electrode active material to deintercalate lithium. The above phenomenon will significantly reduce the structural stability and electrochemical performance of the positive electrode active material.

Contents of the invention

In order to reduce the transmission impedance of lithium ions in the positive electrode active material and improve the mixed arrangement of Li ⁺ /Ni ²⁺ , and improve the structural stability and electrochemical performance of the positive electrode active material, the invention provides a ternary positive electrode active material containing Its positive electrode sheet and battery.

According to the first aspect of the present invention, there is provided a ternary positive electrode active material, the chemical formula is LiNi _x Co _y Mn _{1-x- y} O ₂ (0<x<1, 0<y<1, 0<x+y <1), the cross-section of the ternary positive electrode active material particles is the shallow surface layer from the outermost layer to the center direction of 0~100nm, the shallow surface layer is doped with metal element M, and the ionic radius of metal element M is larger than that of Ni ³⁺ Ionic radius; the content of metal element M on the outermost surface of the particle is defined as A1, and the content of metal element M in the cross-section of the particle from the outermost layer to the center is defined as A2. A1 and A2 satisfy: A2/A1 >0.7.

The ionic radius of the metal element M doped in the shallow surface layer of the ternary positive electrode active material provided by the present invention is greater than the ionic radius of Ni ³⁺ , on the one hand, it can increase the layer spacing of the ternary positive electrode active material, and reduce the lithium ion in the three The transmission impedance in the ternary positive electrode active material ensures the rapid transmission of lithium ions in the ternary positive electrode active material, enhances the extraction and insertion of lithium ions, and improves the capacity and electrochemical performance of the ternary positive electrode active material. On the other hand, the ionic radius The larger metal element M has a strong affinity with oxygen, which can strengthen the molecular bonding orbital and the strength of the TM-O bond by occupying the transition metal position, and can play a good supporting role in the lattice of the ternary positive electrode active material. , inhibit the loss of lattice oxygen in the ternary cathode active material, reduce the generation of oxygen vacancies, and at the same time inhibit the Li ⁺ /Ni ²⁺ mixed arrangement in the ternary cathode active material, thereby improving the structural stability of the ternary cathode active material In addition, the content of the metal element M doped in the shallow surface layer of the ternary positive electrode active material provided by the present invention gradually decreases from the outermost surface of the positive electrode active material particle to the center direction, and the ionic radius of the metal element M is greater than The ionic radius of Ni ³⁺ , and the content A2 of the metal element M doped at the depth of 40nm and the content A1 of the metal element M on the outermost surface satisfy the relationship A2/A1>0.7, which can effectively suppress the ternary The H2-H3 irreversible phase transition in the serious phase transition region near 40nm in the cathode active material during the cycle further improves the structural stability and electrochemical performance of the shallow surface layer of the ternary cathode active material and improves the cycle effect of the ternary cathode active material .

According to a second aspect of the present invention, there is provided a positive electrode sheet, which includes the above-mentioned ternary positive electrode active material.

Applying the ternary positive electrode active material provided by the invention to the positive electrode sheet enables the positive electrode sheet to have good structural stability and simultaneously improves the electrochemical performance of the positive electrode sheet.

According to a third aspect of the present invention, a battery is provided, which comprises the above-mentioned ternary positive electrode active material.

Applying the ternary cathode active material provided by the invention to a battery enables the battery to have good high-temperature cycle performance and high initial gram capacity at the same time.

Description of drawings

FIG. 1 is a schematic structural view of the ternary cathode active material provided in Example 1 of the present invention.

FIG. 2 is a schematic structural view of the ternary cathode active material provided by Example 2 of the present invention.

FIG. 3 is a schematic structural view of the ternary positive electrode active material provided by Example 3 of the present invention.

FIG. 4 is a schematic structural view of the ternary cathode active material provided by Example 4 of the present invention.

FIG. 5 is a schematic structural view of the ternary positive electrode active material provided by Example 5 of the present invention.

FIG. 6 is a schematic structural view of the ternary positive electrode active material provided by Example 6 of the present invention.

FIG. 7 is a schematic structural view of the ternary cathode active material provided by Example 7 of the present invention.

Fig. 8 is a schematic structural view of the ternary positive electrode active material provided by Example 8 of the present invention.

9 is a schematic structural view of the ternary cathode active material provided in Comparative Example 1 of the present invention.

FIG. 10 is a schematic structural view of the ternary cathode active material provided in Comparative Example 3 of the present invention.

FIG. 11 is a schematic structural view of the ternary cathode active material provided in Comparative Example 4 of the present invention.

Detailed ways

In order to reduce the transmission impedance of lithium ions in the positive electrode active material and improve the mixed arrangement of Li ⁺ /Ni ²⁺ , and improve the structural stability and electrochemical performance of the positive electrode active material, the invention provides a ternary positive electrode active material containing Its positive electrode sheet and battery.

According to the first aspect of the present invention, there is provided a ternary positive electrode active material, the chemical formula is LiNi _x Co _y Mn _{1-x- y} O ₂ (0<x<1, 0<y<1, 0<x+y <1), the cross-section of the ternary positive electrode active material particles is the shallow surface layer from the outermost layer to the center direction of 0~500nm, the shallow surface layer is doped with metal element M, and the ionic radius of metal element M is larger than that of Ni ³⁺ Ionic radius; the content of metal element M on the outermost surface of the particle is defined as A1, and the content of metal element M in the cross-section of the particle from the outermost layer to the center is defined as A2. A1 and A2 satisfy: A2/A1 >0.7.

The ionic radius of the metal element M doped in the shallow surface layer of the ternary positive electrode active material provided by the present invention is greater than the ionic radius of Ni ³⁺ , on the one hand, it can increase the layer spacing of the ternary positive electrode active material, and reduce the lithium ion in the three The transmission impedance in the ternary positive electrode active material ensures the rapid transmission of lithium ions in the ternary positive electrode active material, enhances the extraction and insertion of lithium ions, and improves the capacity and electrochemical performance of the ternary positive electrode active material. On the other hand, the ionic radius The larger metal element M has a strong affinity with oxygen, which can strengthen the molecular bonding orbital and the strength of the TM-O bond by occupying the transition metal position, and can play a good supporting role in the lattice of the ternary positive electrode active material. , inhibit the loss of lattice oxygen in the ternary cathode active material, reduce the generation of oxygen vacancies, and at the same time inhibit the Li ⁺ /Ni ²⁺ mixed arrangement in the ternary cathode active material, thereby improving the structural stability of the ternary cathode active material In addition, the content of the metal element M doped in the shallow surface layer of the ternary positive electrode active material provided by the present invention gradually decreases from the outermost surface of the positive electrode active material particle to the center direction, and the ionic radius of the metal element M is greater than The ionic radius of Ni ³⁺ , and the content A2 of the metal element M doped at the depth of 40nm and the content A1 of the metal element M on the outermost surface satisfy the relationship A2/A1>0.7, which can effectively suppress the ternary The H2-H3 irreversible phase transition in the serious phase transition region near 40nm in the cathode active material during the cycle further improves the structural stability and electrochemical performance of the shallow surface layer of the ternary cathode active material and improves the cycle effect of the ternary cathode active material .

Preferably, the content of the metal element M in the cross-section of the particle at 60 nm from the outermost layer to the center is defined as A3, and the A1 and A3 satisfy A3/A1>0.6.

Preferably, the content of the metal element M in the cross-section of the particle at 100 nm from the outermost layer to the center is defined as A4, A1 and A4 satisfy, and A4/A1>0.4.

The ionic radius of the metal element M doped in the shallow surface layer of the ternary positive electrode active material provided by the invention is greater than the ionic radius of Ni ³⁺ , and the content A2 of the metal element M doped at a depth of 40nm is the same as that of the outermost metal element The content A1 of M satisfies A2/A1>0.7, the content A4 of the metal element M doped at a depth of 100nm, and the content A1 of the outermost metal element M satisfy A2/A1>0.4, meeting the above three conditions can guarantee three The shallow surface layer of the ternary positive electrode active material is doped with metal element M at 0-100nm, which can further improve the structural stability of the shallow surface layer of the ternary positive electrode active material and reduce the risk of irreversible phase transition during the cycle of the ternary positive electrode active material. It can also further suppress Li ⁺ /Ni ^{2 +} mixing in the ternary positive electrode active material, so that the extraction and insertion speed of lithium ions can be further increased, thereby making the electrochemical performance of the ternary positive electrode active material more excellent.

Preferably, the metal element M is selected from at least one of niobium, titanium, tantalum, tin, and lanthanide metal elements.

Preferably, the mass content of the metal element M in the ternary positive electrode active material is 1000-2000 ppm.

By limiting the mass content of the metal element M doped in the shallow surface layer in the ternary positive electrode active material to between 1000 and 2000 ppm, it can be ensured that the metal element has a certain doping depth and doping in the shallow surface layer of the ternary positive electrode active material. The heterogeneity of the ternary positive electrode active material is higher, and the structural stability of the ternary positive electrode active material is higher. The application of the ternary positive electrode active material in the battery can endow the battery with good cycle performance. If the mass content of the metal element M in the ternary positive electrode active material is less than 1000ppm, the doping depth and doping uniformity of the metal element M will be reduced, so that the cycle performance of the battery containing the positive electrode active material will decline; if If the mass content of the metal element M in the ternary positive electrode active material is greater than 2000ppm, the phenomenon of excessive doping of the metal element M will occur, which will destroy the ordered structure of the ternary positive electrode active material, making the ternary positive electrode active material Performance drops significantly.

Preferably, the particle diameter D50 of the ternary positive electrode active material is 2-5 μm.

Preferably, the specific surface area of the ternary positive electrode active material is 0.3-1.3 m ² /g.

Preferably, the preparation method of the above-mentioned ternary positive electrode active material is as follows:

S1. Utilize nickel salt, cobalt salt, manganese salt to prepare soluble salt solution;

S2. After mixing the soluble salt solution with NaOH and NH ₃ ·H ₂ O, a coprecipitation reaction is carried out to obtain a precursor;

S3. Sintering after mixing the precursor and LiOH to obtain a primary sintered material;

S4. The primary sintered material is mixed with the material containing the metal element M and then sintered to obtain a ternary positive electrode active material.

Preferably, in S1, calculated according to the amount of substances, Ni:Co:Mn=92:5:3.

Preferably, in S3, calculated according to the amount of substance, M _Li : _Mtotal =1.05, wherein, _Mtotal represents the sum of the amount of substances of Ni, Co, and Mn elements in the precursor, and M _Li represents the amount of the Li element in LiOH amount of substance.

Preferably, in S3, the sintering temperature is 740-760° C., and the sintering time is 11-13 hours.

Preferably, in S4, the sintering temperature is 700-800° C., and the sintering time is 9-11 hours.

According to a second aspect of the present invention, there is provided a positive electrode sheet, which includes the above-mentioned ternary positive electrode active material.

Applying the ternary positive electrode active material provided by the invention to the positive electrode sheet enables the positive electrode sheet to have good structural stability and simultaneously improves the electrochemical performance of the positive electrode sheet.

According to a third aspect of the present invention, a battery is provided, which comprises the above-mentioned ternary positive electrode active material.

Applying the ternary cathode active material provided by the invention to a battery enables the battery to have good high-temperature cycle performance and high initial gram capacity at the same time.

The technical features in the technical solutions provided by the present invention will be further clearly and completely described below in conjunction with specific implementation methods. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts belong to the protection scope of the present invention.

Example 1

A kind of ternary cathode active material, its structure is as shown in Figure 1, and preparation method is as follows:

S1. Dissolve nickel salt (NiSO ₄ ·6H ₂ O), cobalt salt (CoSO ₄ ·7H ₂ O), manganese salt (MnSO ₄ ·H ₂ O) in deionized water, and mix well to prepare a soluble salt solution;

In S1, the feeding amount of nickel salt, cobalt salt, and manganese salt is as follows, calculated according to the amount of substance, Ni:Co:Mn=92:5:3;

S2. Co-flow the soluble salt solution, NaOH solution, and NH ₃ ·H ₂ O complexing agent solution, then transfer to a continuous stirred tank reactor, feed oxygen with a purity of 99.5%, and start the continuous stirred tank reaction The stirring device of the reactor, the temperature of the continuous stirred tank reactor is controlled at 50 ° C, and the pH value of the reaction system is continuously monitored during the reaction process, and the pH value of the reaction system is adjusted to 12.1. After coprecipitation reaction, the precursor is prepared [N ₉₂ Co ₅ Mn ₃ ](OH ₂ );

S3. Put the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) and LiOH into the mixer and mix evenly to prepare the mixture, then put the mixture in the sintering furnace, adjust the heating rate to 2°C/min, Sintering at 400°C for 4 hours in an oxygen atmosphere, and then sintering at 750°C for 12 hours to obtain a primary sintered material;

In S3, _the dosage _of the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) _and LiOH is as follows _. The sum of the quantities is M _total , and the amount of the Li element in LiOH is M _Li , calculated according to the amount of matter, M _Li : M _total = 1.05;

S4. Put the primary sintered material and La(NO ₃ ) ₃ into the mixer for mixing, then put them into the sintering furnace, adjust the heating rate at 2°C/min, sinter at 400°C for 4 hours in an oxygen atmosphere, and then sinter at 800°C Sinter at ℃ for 10 hours, cool naturally to room temperature, and obtain the ternary positive electrode active material of this embodiment after crushing and screening, its particle size D50=3.60 μm, and its shallow surface layer is doped with La;

In S4, the amount of La(NO ₃ ) ₃ added was 2000 ppm.

Example 2

A kind of ternary cathode active material, its structure is as shown in Figure 2, and preparation method is as follows:

S1. Dissolve nickel salt (NiSO ₄ ·6H ₂ O), cobalt salt (CoSO ₄ ·7H ₂ O), manganese salt (MnSO ₄ ·H ₂ O) in deionized water, and mix well to prepare a soluble salt solution;

In S1, the feeding amount of nickel salt, cobalt salt, and manganese salt is as follows, calculated according to the amount of substance, Ni:Co:Mn=92:5:3;

S2. Co-flow the soluble salt solution, NaOH solution, and NH ₃ ·H ₂ O complexing agent solution, then transfer to a continuous stirred tank reactor, feed oxygen with a purity of 99.5%, and start the continuous stirred tank reaction The stirring device of the reactor, the temperature of the continuous stirred tank reactor is controlled at 50 ° C, and the pH value of the reaction system is continuously monitored during the reaction process, and the pH value of the reaction system is adjusted to 12.1. After coprecipitation reaction, the precursor is prepared [N ₉₂ Co ₅ Mn ₃ ](OH ₂ );

S3. Put the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) and LiOH into the mixer and mix evenly to prepare the mixture, then put the mixture in the sintering furnace, adjust the heating rate to 2°C/min, Sintering at 400°C for 4 hours in an oxygen atmosphere, and then sintering at 750°C for 12 hours to obtain a primary sintered material;

In S3, _the dosage _of the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) _and LiOH is as follows _. The sum of the quantities is M _total , and the amount of the Li element in LiOH is M _Li , calculated according to the amount of matter, M _Li : M _total = 1.05;

S4. Put the primary sintered material and La(NO ₃ ) ₃ into the mixer for mixing, then put them into the sintering furnace, adjust the heating rate at 2°C/min, sinter at 400°C for 4 hours in an oxygen atmosphere, and then sinter at 780°C Sinter at ℃ for 10 hours, cool naturally to room temperature, and obtain the ternary positive electrode active material of this embodiment after crushing and screening, its particle size D50=3.57 μm, and its shallow surface layer is doped with La;

In S4, the amount of La(NO ₃ ) ₃ added was 1500 ppm.

Example 3

A kind of ternary cathode active material, its structure is as shown in Figure 3, and preparation method is as follows:

S1. Dissolve nickel salt (NiSO ₄ ·6H ₂ O), cobalt salt (CoSO ₄ ·7H ₂ O), manganese salt (MnSO ₄ ·H ₂ O) in deionized water, and mix well to prepare a soluble salt solution;

In S1, the feeding amount of nickel salt, cobalt salt, and manganese salt is as follows, calculated according to the amount of substance, Ni:Co:Mn=92:5:3;

S2. Co-flow the soluble salt solution, NaOH solution, and NH ₃ ·H ₂ O complexing agent solution, then transfer to a continuous stirred tank reactor, feed oxygen with a purity of 99.5%, and start the continuous stirred tank reaction The stirring device of the reactor, the temperature of the continuous stirred tank reactor is controlled at 50 ° C, and the pH value of the reaction system is continuously monitored during the reaction process, and the pH value of the reaction system is adjusted to 12.1. After coprecipitation reaction, the precursor is prepared [N ₉₂ Co ₅ Mn ₃ ](OH ₂ );

S3. Put the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) and LiOH into the mixer and mix evenly to prepare the mixture, then put the mixture in the sintering furnace, adjust the heating rate to 2°C/min, Sintering at 400°C for 4 hours in an oxygen atmosphere, and then sintering at 750°C for 12 hours to obtain a primary sintered material;

In S3, _the dosage _of the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) _and LiOH is as follows _. The sum of the quantities is M _total , and the amount of the Li element in LiOH is M _Li , calculated according to the amount of matter, M _Li : M _total = 1.05;

S4. Put the primary sintered material and La(NO ₃ ) ₃ into the mixer for mixing, then put them into the sintering furnace, adjust the heating rate at 2°C/min, sinter at 400°C for 4 hours in an oxygen atmosphere, and then sinter at 760°C Sinter at ℃ for 10 hours, cool naturally to room temperature, and obtain the ternary positive electrode active material of this embodiment after crushing and screening, its particle size D50=3.62 μm, and its shallow surface layer is doped with La;

In S4, the amount of La(NO ₃ ) ₃ added was 1000 ppm.

Example 4

A kind of ternary cathode active material, its structure is as shown in Figure 4, and preparation method is as follows:

S1. Dissolve nickel salt (NiSO ₄ ·6H ₂ O), cobalt salt (CoSO ₄ ·7H ₂ O), manganese salt (MnSO ₄ ·H ₂ O) in deionized water, and mix well to prepare a soluble salt solution;

In S1, the feeding amount of nickel salt, cobalt salt, and manganese salt is as follows, calculated according to the amount of substance, Ni:Co:Mn=92:5:3;

S2. Co-flow the soluble salt solution, NaOH solution, and NH ₃ ·H ₂ O complexing agent solution, then transfer to a continuous stirred tank reactor, feed oxygen with a purity of 99.5%, and start the continuous stirred tank reaction The stirring device of the reactor, the temperature of the continuous stirred tank reactor is controlled at 50 ° C, and the pH value of the reaction system is continuously monitored during the reaction process, and the pH value of the reaction system is adjusted to 12.1. After coprecipitation reaction, the precursor is prepared [N ₉₂ Co ₅ Mn ₃ ](OH ₂ );

S3. Put the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) and LiOH into the mixer and mix evenly to prepare the mixture, then put the mixture in the sintering furnace, adjust the heating rate to 2°C/min, Sintering at 400°C for 4 hours in an oxygen atmosphere, and then sintering at 750°C for 12 hours to obtain a primary sintered material;

In S3, _the dosage _of the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) _and LiOH is as follows _. The sum of the quantities is M _total , and the amount of the Li element in LiOH is M _Li , calculated according to the amount of matter, M _Li : M _total = 1.05;

S4. Add the primary sintered material and La(NO ₃ ) ₃ into the mixer for mixing, then put them into the sintering furnace, adjust the heating rate at 2°C/min, sinter at 400°C for 4 hours in an oxygen atmosphere, and then sinter at 720°C Sinter at ℃ for 10 hours, cool naturally to room temperature, and obtain the ternary positive electrode active material of this embodiment after crushing and screening, its particle size D50=3.59 μm, and its shallow surface layer is doped with La;

In S4, the amount of La(NO ₃ ) ₃ added was 1000 ppm.

Example 5

A kind of ternary cathode active material, its structure is shown in Figure 5, and preparation method is as follows:

S1. Dissolve nickel salt (NiSO ₄ ·6H ₂ O), cobalt salt (CoSO ₄ ·7H ₂ O), manganese salt (MnSO ₄ ·H ₂ O) in deionized water, and mix well to prepare a soluble salt solution;

In S1, the feeding amount of nickel salt, cobalt salt, and manganese salt is as follows, calculated according to the amount of substance, Ni:Co:Mn=92:5:3;

S2. Co-flow the soluble salt solution, NaOH solution, and NH ₃ ·H ₂ O complexing agent solution, then transfer to a continuous stirred tank reactor, feed oxygen with a purity of 99.5%, and start the continuous stirred tank reaction The stirring device of the reactor, the temperature of the continuous stirred tank reactor is controlled at 50 ° C, and the pH value of the reaction system is continuously monitored during the reaction process, and the pH value of the reaction system is adjusted to 12.1. After coprecipitation reaction, the precursor is prepared [N ₉₂ Co ₅ Mn ₃ ](OH ₂ );

S3. Put the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) and LiOH into the mixer and mix evenly to prepare the mixture, then put the mixture in the sintering furnace, adjust the heating rate to 2°C/min, Sintering at 400°C for 4 hours in an oxygen atmosphere, and then sintering at 750°C for 12 hours to obtain a primary sintered material;

In S3, _the dosage _of the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) _and LiOH is as follows _. The sum of the quantities is M _total , and the amount of the Li element in LiOH is M _Li , calculated according to the amount of matter, M _Li : M _total = 1.05;

S4. Put the primary sintered material and Ta ₂ O ₅ into the mixer for mixing, then put them into the sintering furnace, adjust the heating rate at 2°C/min, sinter at 400°C for 4 hours in an oxygen atmosphere, and then sinter at 760°C Sinter for 10 hours, cool naturally to room temperature, and obtain the ternary positive electrode active material of this embodiment after crushing and screening, its particle size D50=3.61 μm, and its shallow surface layer is doped with Ta;

In S4, the addition amount of _Ta2O5 is _1000ppm .

Example 6

A kind of ternary cathode active material, its structure is shown in Figure 6, and preparation method is as follows:

S1. Dissolve nickel salt (NiSO ₄ ·6H ₂ O), cobalt salt (CoSO ₄ ·7H ₂ O), manganese salt (MnSO ₄ ·H ₂ O) in deionized water, and mix well to prepare a soluble salt solution;

In S1, the feeding amount of nickel salt, cobalt salt, and manganese salt is as follows, calculated according to the amount of substance, Ni:Co:Mn=92:5:3;

S2. Co-flow the soluble salt solution, NaOH solution, and NH ₃ ·H ₂ O complexing agent solution, then transfer to a continuous stirred tank reactor, feed oxygen with a purity of 99.5%, and start the continuous stirred tank reaction The stirring device of the reactor, the temperature of the continuous stirred tank reactor is controlled at 50 ° C, and the pH value of the reaction system is continuously monitored during the reaction process, and the pH value of the reaction system is adjusted to 12.1. After coprecipitation reaction, the precursor is prepared [N ₉₂ Co ₅ Mn ₃ ](OH ₂ );

S3. Put the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) and LiOH into the mixer and mix evenly to prepare the mixture, then put the mixture in the sintering furnace, adjust the heating rate to 2°C/min, Sintering at 400°C for 4 hours in an oxygen atmosphere, and then sintering at 750°C for 12 hours to obtain a primary sintered material;

In S3, the sum of the amounts of Ni, Co, and Mn elements in the precursor [N ₉₂ Co ₅ Mn ₃ ] (OH ₂ ) is M _total , and the amount of Li elements in LiOH is M _Li , according to Calculation of the amount of substance, M _Li : M _total = 1.05;

S4. Add the primary sintered material and Ce(NO ₃ ) ₃ to the mixer for mixing, then put them into the sintering furnace, adjust the heating rate at 2°C/min, sinter at 400°C for 4 hours in an oxygen atmosphere, and then sinter at 760°C Sintering at ℃ for 10 hours, cooling naturally to room temperature, crushing and screening to obtain the ternary positive electrode active material of this example, its particle size D50=3.62 μm, and its shallow surface layer is doped with Ce;

In S4, the amount of Ce(NO ₃ ) ₃ added was 1000 ppm.

Example 7

A kind of ternary cathode active material, its structure is shown in Figure 7, and preparation method is as follows:

S1. Dissolve nickel salt (NiSO ₄ ·6H ₂ O), cobalt salt (CoSO ₄ ·7H ₂ O), manganese salt (MnSO ₄ ·H ₂ O) in deionized water, and mix well to prepare a soluble salt solution;

In S1, the feeding amount of nickel salt, cobalt salt, and manganese salt is as follows, calculated according to the amount of substance, Ni:Co:Mn=92:5:3;

S2. Co-flow the soluble salt solution, NaOH solution, and NH ₃ ·H ₂ O complexing agent solution, then transfer to a continuous stirred tank reactor, feed oxygen with a purity of 99.5%, and start the continuous stirred tank reaction The stirring device of the reactor, the temperature of the continuous stirred tank reactor is controlled at 50 ° C, and the pH value of the reaction system is continuously monitored during the reaction process, and the pH value of the reaction system is adjusted to 12.1. After coprecipitation reaction, the precursor is prepared [N ₉₂ Co ₅ Mn ₃ ](OH ₂ );

S3. Put the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) and LiOH into the mixer and mix evenly to prepare the mixture, then put the mixture in the sintering furnace, adjust the heating rate to 2°C/min, Sintering at 400°C for 4 hours in an oxygen atmosphere, and then sintering at 750°C for 12 hours to obtain a primary sintered material;

In S3, _the dosage _of the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) _and LiOH is as follows _. The sum of the quantities is M _total , and the amount of the Li element in LiOH is M _Li , calculated according to the amount of matter, M _Li : M _total = 1.05;

S4. Put the primary sintered material, La(NO ₃ ) ₃ , and TiO ₂ into the mixer for mixing, then put them into the sintering furnace, adjust the heating rate at 2°C/min, and sinter at 400°C for 4 hours in an oxygen atmosphere. Then sinter at 760° C. for 10 hours, cool naturally to room temperature, and obtain the ternary positive electrode active material of this embodiment after crushing and screening, its particle size D50=3.62 μm, and its shallow surface layer is doped with La and Ti;

In S4, the added amount of La(NO ₃ ) ₃ was 1000 ppm, and the added amount of TiO ₂ was 500 ppm.

Example 8

A ternary positive electrode active material, the structure of which is shown in Figure 8, and the preparation method is as follows:

S1. Dissolve nickel salt (NiSO ₄ ·6H ₂ O), cobalt salt (CoSO ₄ ·7H ₂ O), manganese salt (MnSO ₄ ·H ₂ O) in deionized water, and mix well to prepare a soluble salt solution;

In S1, the feeding amount of nickel salt, cobalt salt, and manganese salt is as follows, calculated according to the amount of substance, Ni:Co:Mn=92:5:3;

S2. Co-flow the soluble salt solution, NaOH solution, and NH ₃ ·H ₂ O complexing agent solution, then transfer to a continuous stirred tank reactor, feed oxygen with a purity of 99.5%, and start the continuous stirred tank reaction The stirring device of the reactor, the temperature of the continuous stirred tank reactor is controlled at 50 ° C, and the pH value of the reaction system is continuously monitored during the reaction process, and the pH value of the reaction system is adjusted to 12.1. After coprecipitation reaction, the precursor is prepared [N ₉₂ Co ₅ Mn ₃ ](OH ₂ );

S3. Put the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) and LiOH into the mixer and mix evenly to prepare the mixture, then put the mixture in the sintering furnace, adjust the heating rate to 2°C/min, Sintering at 400°C for 4 hours in an oxygen atmosphere, and then sintering at 750°C for 12 hours to obtain a primary sintered material;

In S3, _the dosage _of the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) _and LiOH is as follows _. The sum of the quantities is M _total , and the amount of the Li element in LiOH is M _Li , calculated according to the amount of matter, M _Li : M _total = 1.05;

S4. Add La(NO ₃ ) ₃ into absolute ethanol and place it in a 60°C water bath and continue to stir until La(NO ₃ ) ₃ is completely dissolved, then add a sintered material to it, stir evenly to obtain a mixed solution, and then add The mixed solution was dried in a blast oven at 120°C for 24 hours to obtain a mixture, and then the completely dried mixture was put into a sintering furnace, and the heating rate was adjusted to 2°C/min, and sintered at 400°C under an oxygen atmosphere for 4 hours. hours, then sintered at 760°C for 10 hours, and obtained the ternary positive electrode active material of the present embodiment through crushing and screening, its particle size D50=3.61 μm, and its shallow surface layer was doped with La;

In S4, the amount of La(NO ₃ ) ₃ added was 1000 ppm.

Example 9

A ternary positive electrode active material, the preparation method of which is as follows:

S1. Dissolve nickel salt (NiSO ₄ ·6H ₂ O), cobalt salt (CoSO ₄ ·7H ₂ O), manganese salt (MnSO ₄ ·H ₂ O) in deionized water, and mix well to prepare a soluble salt solution;

In S1, the feeding amount of nickel salt, cobalt salt, and manganese salt is as follows, calculated according to the amount of substance, Ni:Co:Mn=92:5:3;

S2. Co-flow the soluble salt solution, NaOH solution, and NH ₃ ·H ₂ O complexing agent solution, then transfer to a continuous stirred tank reactor, feed oxygen with a purity of 99.5%, and start the continuous stirred tank reaction The stirring device of the reactor, the temperature of the continuous stirred tank reactor is controlled at 50 ° C, and the pH value of the reaction system is continuously monitored during the reaction process, and the pH value of the reaction system is adjusted to 12.1. After coprecipitation reaction, the precursor is prepared [N ₉₂ Co ₅ Mn ₃ ](OH ₂ );

S3. Put the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) and LiOH into the mixer and mix evenly to prepare the mixture, then put the mixture in the sintering furnace, adjust the heating rate to 2°C/min, Sintering at 400°C for 4 hours in an oxygen atmosphere, and then sintering at 750°C for 12 hours to obtain a primary sintered material;

In S3, _the dosage _of the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) _and LiOH is as follows _. The sum of the quantities is M _total , and the amount of the Li element in LiOH is M _Li , calculated according to the amount of matter, M _Li : M _total = 1.05;

S4. Put the primary sintered material and La(NO ₃ ) ₃ into the mixer for mixing, then put them into the sintering furnace, adjust the heating rate at 2°C/min, sinter at 400°C for 4 hours in an oxygen atmosphere, and then sinter at 760°C After sintering at ℃ for 5 hours, the temperature was lowered to 600 ℃ and the temperature was continued for 5 hours, cooled naturally to room temperature, and the ternary positive electrode active material of this embodiment was obtained after crushing and screening, its particle size D50=3.59 μm, and its shallow surface layer was doped with La;

In S4, the amount of La(NO ₃ ) ₃ added was 1000 ppm.

Example 10

A ternary positive electrode active material, the preparation method of which is as follows:

S1. Dissolve nickel salt (NiSO ₄ ·6H ₂ O), cobalt salt (CoSO ₄ ·7H ₂ O), manganese salt (MnSO ₄ ·H ₂ O) in deionized water, and mix well to prepare a soluble salt solution;

In S1, the feeding amount of nickel salt, cobalt salt, and manganese salt is as follows, calculated according to the amount of substance, Ni:Co:Mn=92:5:3;

S2. Co-flow the soluble salt solution, NaOH solution, and NH ₃ ·H ₂ O complexing agent solution, then transfer to a continuous stirred tank reactor, feed oxygen with a purity of 99.5%, and start the continuous stirred tank reaction The stirring device of the reactor, the temperature of the continuous stirred tank reactor is controlled at 50 ° C, and the pH value of the reaction system is continuously monitored during the reaction process, and the pH value of the reaction system is adjusted to 12.1. After coprecipitation reaction, the precursor is prepared [N ₉₂ Co ₅ Mn ₃ ](OH ₂ );

S3. Put the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) and LiOH into the mixer and mix evenly to prepare the mixture, then put the mixture in the sintering furnace, adjust the heating rate to 2°C/min, Sintering at 400°C for 4 hours in an oxygen atmosphere, and then sintering at 750°C for 12 hours to obtain a primary sintered material;

In S3, _the dosage _of the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) _and LiOH is as follows _. The sum of the quantities is M _total , and the amount of the Li element in LiOH is M _Li , calculated according to the amount of matter, M _Li : M _total = 1.05;

S4. Put the primary sintered material and La(NO ₃ ) ₃ into the mixer for mixing, then put them into the sintering furnace, adjust the heating rate at 2°C/min, sinter at 400°C for 4 hours in an oxygen atmosphere, and then sinter at 760°C After sintering at ℃ for 8 hours, lower the temperature to 700 ℃ and continue to keep warm for 2 hours, cool naturally to room temperature, and obtain the ternary positive electrode active material of this embodiment after crushing and screening, its particle size D50=3.60 μm, and its shallow surface layer is doped with La;

In S4, the amount of La(NO ₃ ) ₃ added was 1000 ppm.

Comparative example 1

A ternary positive electrode active material, the structure of which is shown in Figure 9, and the preparation method is as follows:

S1. Dissolve nickel salt (NiSO ₄ ·6H ₂ O), cobalt salt (CoSO ₄ ·7H ₂ O), manganese salt (MnSO ₄ ·H ₂ O) in deionized water, and mix well to prepare a soluble salt solution;

In S1, the feeding amount of nickel salt, cobalt salt, and manganese salt is as follows, calculated according to the amount of substance, Ni:Co:Mn=92:5:3;

S2. Co-flow the soluble salt solution, NaOH solution, and NH ₃ ·H ₂ O complexing agent solution, then transfer to a continuous stirred tank reactor, feed oxygen with a purity of 99.5%, and start the continuous stirred tank reaction The stirring device of the reactor, the temperature of the continuous stirred tank reactor is controlled at 50 ° C, and the pH value of the reaction system is continuously monitored during the reaction process, and the pH value of the reaction system is adjusted to 12.1. After coprecipitation reaction, the precursor is prepared [N ₉₂ Co ₅ Mn ₃ ](OH ₂ );

S3. Put the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) and LiOH into the mixer and mix evenly to prepare the mixture, then put the mixture in the sintering furnace, adjust the heating rate to 2°C/min, Sintering at 400°C for 4 hours in an oxygen atmosphere, and then sintering at 750°C for 12 hours to obtain a primary sintered material;

In S3, _the dosage _of the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) _and LiOH is as follows _. The sum of the quantities is M _total , and the amount of the Li element in LiOH is M _Li , calculated according to the amount of matter, M _Li : M _total = 1.05;

S4. Put the primary sintered material and La(NO ₃ ) ₃ into the mixer for mixing, then put them into the sintering furnace, adjust the heating rate at 2°C/min, sinter at 400°C for 4 hours in an oxygen atmosphere, and then sinter at 700°C Sinter at ℃ for 10 hours, cool naturally to room temperature, and obtain the ternary positive electrode active material of this embodiment after crushing and screening, its particle size D50=3.60 μm, and its shallow surface layer is doped with La;

In S4, the amount of La(NO ₃ ) ₃ added was 500 ppm.

Comparative example 2

A ternary positive electrode active material, the preparation method of which is as follows:

S1. Dissolve nickel salt (NiSO ₄ ·6H ₂ O), cobalt salt (CoSO ₄ ·7H ₂ O), manganese salt (MnSO ₄ ·H ₂ O) in deionized water, and mix well to prepare a soluble salt solution;

In S1, the feeding amount of nickel salt, cobalt salt, and manganese salt is as follows, calculated according to the amount of substance, Ni:Co:Mn=92:5:3;

S2. Co-flow the soluble salt solution, NaOH solution, and NH ₃ ·H ₂ O complexing agent solution, then transfer to a continuous stirred tank reactor, feed oxygen with a purity of 99.5%, and start the continuous stirred tank reaction The stirring device of the reactor, the temperature of the continuous stirred tank reactor is controlled at 50 ° C, and the pH value of the reaction system is continuously monitored during the reaction process, and the pH value of the reaction system is adjusted to 12.1. After coprecipitation reaction, the precursor is prepared [N ₉₂ Co ₅ Mn ₃ ](OH ₂ );

S3. Put the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) and LiOH into the mixer and mix evenly to prepare the mixture, then put the mixture in the sintering furnace, adjust the heating rate to 2°C/min, Sintering at 400°C for 4 hours in an oxygen atmosphere, and then sintering at 750°C for 12 hours to obtain a primary sintered material;

In S3, _the dosage _of the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) _and LiOH is as follows _. The sum of the quantities is M _total , and the amount of the Li element in LiOH is M _Li , calculated according to the amount of matter, M _Li : M _total = 1.05;

S4. Add the primary sintered material and La(NO ₃ ) ₃ into the mixer for mixing, then put them into the sintering furnace, adjust the heating rate at 2°C/min, sinter at 400°C for 4 hours in an oxygen atmosphere, and then sinter at 840°C Sinter at ℃ for 10 hours, cool naturally to room temperature, and obtain the ternary positive electrode active material of this embodiment after crushing and screening, its particle size D50=3.62 μm, and its shallow surface layer is doped with La;

In S4, the amount of La(NO ₃ ) ₃ added was 3000 ppm.

Comparative example 3

A kind of ternary cathode active material, its structure is shown in Figure 10, and preparation method is as follows:

S1. Dissolve nickel salt (NiSO ₄ ·6H ₂ O), cobalt salt (CoSO ₄ ·7H ₂ O), manganese salt (MnSO ₄ ·H ₂ O) in deionized water, and mix well to prepare a soluble salt solution;

In S1, the feeding amount of nickel salt, cobalt salt, and manganese salt is as follows, calculated according to the amount of substance, Ni:Co:Mn=92:5:3;

S2. Co-flow the soluble salt solution, NaOH solution, and NH ₃ ·H ₂ O complexing agent solution, then transfer to a continuous stirred tank reactor, feed oxygen with a purity of 99.5%, and start the continuous stirred tank reaction The stirring device of the reactor, the temperature of the continuous stirred tank reactor is controlled at 50 ° C, and the pH value of the reaction system is continuously monitored during the reaction process, and the pH value of the reaction system is adjusted to 12.1. After coprecipitation reaction, the precursor is prepared [N ₉₂ Co ₅ Mn ₃ ](OH ₂ );

S3. Put the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) and LiOH into the mixer and mix evenly to prepare the mixture, then put the mixture in the sintering furnace, adjust the heating rate to 2°C/min, Sintering at 400°C for 4 hours in an oxygen atmosphere, and then sintering at 750°C for 12 hours to obtain a primary sintered material;

In S3, _the dosage _of the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) _and LiOH is as follows _. The sum of the quantities is _Mtotal , and the quantity of Li elements is M _Li , calculated according to the quantity of substances, M _Li : _Mtotal =1.05;

S4. Put the primary sintered material and Al ₂ O ₃ into the mixer for mixing, then put them into the sintering furnace, adjust the heating rate at 2°C/min, sinter at 400°C for 4 hours in an oxygen atmosphere, and then sinter at 670°C Sinter for 10 hours, cool naturally to room temperature, and obtain the ternary positive electrode active material of this embodiment after crushing and screening, its particle size D50=3.59 μm, and its shallow surface layer is doped with Al;

In S4, the addition amount of Al ₂ O ₃ is 1000 ppm.

Comparative example 4

A ternary positive electrode active material, the structure of which is shown in Figure 11, and the preparation method is as follows:

S1. Dissolve nickel salt (NiSO ₄ ·6H ₂ O), cobalt salt (CoSO ₄ ·7H ₂ O), manganese salt (MnSO ₄ ·H ₂ O) in deionized water, and mix well to prepare a soluble salt solution;

In S1, the feeding amount of nickel salt, cobalt salt, and manganese salt is as follows, calculated according to the amount of substance, Ni:Co:Mn=92:5:3;

S2. Co-flow the soluble salt solution, NaOH solution, and NH ₃ ·H ₂ O complexing agent solution, then transfer to a continuous stirred tank reactor, feed oxygen with a purity of 99.5%, and start the continuous stirred tank reaction The stirring device of the reactor, the temperature of the continuous stirred tank reactor is controlled at 50 ° C, and the pH value of the reaction system is continuously monitored during the reaction process, and the pH value of the reaction system is adjusted to 12.1. After coprecipitation reaction, the precursor is prepared [N ₉₂ Co ₅ Mn ₃ ](OH ₂ );

S3. Put the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) and LiOH into the mixer and mix evenly to prepare the mixture, then put the mixture in the sintering furnace, adjust the heating rate to 2°C/min, Sintering at 400°C for 4 hours in an oxygen atmosphere, and then sintering at 750°C for 12 hours to obtain a primary sintered material;

In S3, _the dosage _of the precursor [N ₉₂ Co ₅ Mn ₃ ](OH ₂ ) _and LiOH is as follows _. The sum of the quantities is M _total , and the amount of the Li element in LiOH is M _Li , calculated according to the amount of matter, M _Li : M _total = 1.05;

S4. Put the primary sintered material and H ₃ BO ₃ into the mixer for mixing, then put them into the sintering furnace, adjust the heating rate at 2°C/min, sinter at 400°C for 4 hours in an oxygen atmosphere, and then sinter at 700°C Sinter for 10 hours, cool naturally to room temperature, and obtain the ternary positive electrode active material of this embodiment after crushing and screening, its particle size D50=3.58 μm, and its bulk phase is doped with B;

In S4, the addition amount of H ₃ BO ₃ is 1000 ppm.

test case

1. Participants

In this test example, the ternary positive electrode active materials prepared in Examples 1-10 and Comparative Examples 1-4 were used as test subjects, and related performance tests were carried out.

2. Test content

(1) Element content

In the ternary positive electrode active materials prepared in Examples 1 to 10 and Comparative Examples 1 to 4, the content (A1) of the metal element M in the outermost surface of the cross section of the ternary positive electrode active material particle The peak area of the outermost surface indicates that the content (A2) of the metal element M in the cross section of the ternary positive electrode active material particle at 40nm from the outermost layer to the center is expressed by the peak area of the metal element M at 40nm, and the metal element The content of M in the cross-section of the ternary positive electrode active material particle from the outermost layer to the center at 60nm (A3) is represented by the peak area of the metal element M at 60nm, and the metal element M is in the cross-section of the ternary positive electrode active material particle The content (A4) at 100 nm from the outermost layer to the center is represented by the peak area of the metal element M at 100 nm.

X-ray photoelectron spectroscopy (XPS) was used to characterize the element content of the ternary positive electrode active material, and the doped metal element M was etched on the outermost surface of the ternary positive electrode active material particles and etched at 40nm, 60nm, and 100nm. The signal was collected, and the original XPS data was subjected to peak fitting processing (error χ ² <1), and the peak area was calculated. By calculating the proportion of the peak area of the metal element M doped after etching to the peak area of the metal element M doped on the outermost surface, it can reflect the doping depth and content change of the metal element M. The specific operation steps are as follows :

①Sample preparation process: The ternary positive electrode active material, conductive agent acetylene black, and binder PVDF prepared in Examples 1-10 and Comparative Examples 1-4 were added to the solvent methyl alcohol at a mass ratio of 98:1:1. In pyrrolidone (NMP), the positive electrode slurry was prepared;

②Apply the positive electrode slurry evenly on the aluminum foil of the positive electrode current collector. After rolling, slicing and other processes, the positive electrode sheet is obtained, and the electrode sheet is cut into a sheet shape not larger than 1cm*1xm, and then the sample is clamped on the sample holder Above, use Thermo Fisher X-ray photoelectron spectroscopy in an ultra-vacuum environment to collect signals on the surface of the pole piece;

③ During the signal acquisition process, use soft X-rays with characteristic wavelengths (commonly used ray sources Mg Kα-1253.6eV or Al Kα-1486.6 eV) to irradiate the surface of the sample and interact with surface atoms. When the photon energy is greater than the combination of extranuclear electrons When the energy is high, the electrons in the inner layer can be excited out. This kind of electrons is called photoelectrons. The energy of these photoelectrons is highly characteristic. The chemical state of the surface elements of the sample can be obtained by detecting the kinetic energy of photoelectrons and the number of photoelectrons by the detector. and content, to complete the signal acquisition process;

④ In the XPS analysis room (under high vacuum conditions), use an argon ion gun to strip the sample surface by argon ion sputtering, control the appropriate sputtering intensity and sputtering time, etch the sample surface to a certain depth, and then perform spectrum analysis (In order to obtain an accurate sputtering depth, the sputtering rate is generally calibrated with a standard substance with a thickness similar to or the same as that of the sample to be measured, so that the sputtering depth corresponding to the element distribution after calibration can be calculated according to the sputtering time), and here select the etching The depth is 40nm, 60nm and 100nm, and complete the signal acquisition process.

(2) Electrical performance test

Batteries were prepared by using the ternary cathode active materials prepared in Examples 1-10 and Comparative Examples 1-4, and the electrical properties of the batteries were tested.

①Capacity performance test: 25°C, voltage range is set to 2.75~4.3V, charge and discharge the prepared battery at a rate of 0.33C, record the charge and discharge capacity of the first cycle, and calculate the gram capacity according to the weight of the pole piece.

②Cycle performance test: at 45°C, the voltage range is set to 2.75~4.3V, the prepared battery is charged and discharged at a rate of 0.33C, and the full charge and discharge cycle test is carried out. The cycle is 500 cycles, and the capacity retention rate is recorded.

Follow the steps below to prepare the battery:

S1. Preparation of positive electrode sheet

The ternary positive electrode active material, conductive agent acetylene black, and binder PVDF prepared in Examples 1 to 10 and Comparative Examples 1 to 4 were mixed in a mass ratio of 98:1:1, and the solvent methylpyrrolidone (NMP ), stirred under the action of a vacuum mixer until the system is uniform, and the positive electrode slurry is obtained; the positive electrode slurry is evenly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, transferred to an oven to continue drying, and then cooled Pressing and slitting to obtain the positive pole piece;

S2. Preparation of negative electrode sheet

Mix negative electrode active material graphite or mixtures of graphite and other active materials in different mass ratios, conductive agent acetylene black, thickener CMC, and binder SBR in a mass ratio of 96.4:1:1.2:1.4, add solvent for deionization water, stirred under the action of a vacuum mixer until the system is uniform, and the negative electrode slurry is obtained. The negative electrode slurry is evenly coated on both surfaces of the negative electrode current collector copper foil, and after drying at room temperature, transfer to an oven to continue drying, and then pass Cold pressing and slitting to obtain the negative pole piece;

S3. Assemble the battery

Stack the above-mentioned positive electrode, separator, and negative electrode in order, so that the separator is between the positive and negative electrodes to play the role of isolation, and then wind the bare cell, and put the bare cell in the outer packaging In the shell, after drying, inject the electrolyte (the electrolyte is prepared by mixing ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate according to the volume ratio of 1:1:1 and then adding LiPF ₆ to obtain a concentration of 1mol/L), and after vacuum Encapsulation, standing, formation, constant volume and other processes to produce batteries.

3. Experimental results

Table 1 Relevant parameters of ternary cathode active materials and battery performance test results

Note: "--" in Comparative Example 1 means that no doping element was identified in the cross-section of the ternary positive electrode active material particles from the outermost layer to the center direction of 100nm; "--" in Comparative Example 4 means that in the ternary No doping element was identified on the outermost surface of the cross-section of the positive electrode active material particle.

The relevant parameters of the ternary positive electrode active materials prepared in Examples 1-10 and Comparative Examples 1-4 and the performance test results of the batteries are shown in Table 1.

In the ternary positive electrode active material provided by Comparative Example 1, the mass content of La element is 500ppm, and the sintering temperature of the second stage is 700°C, while in the ternary positive electrode active material provided by Comparative Example 2, the mass content of La element is 3000ppm , the sintering temperature in the second stage is 840°C, and the A1/A2 values of the ternary positive electrode active materials finally prepared in Comparative Example 1 and Comparative Example 2 are all <0.7; the ternary positive electrode active materials provided in Comparative Example 3 are doped with The element is Al, and the element doped in the ternary positive electrode active material provided by Comparative Example 4 is B, and the ionic radii of Al and B are all smaller than the ionic radius of Ni ³⁺ , and the ternary positive electrode active material provided by Comparative Example 4 is prepared When the sintering temperature of the second stage of the process is 700°C, the doping element B will diffuse from the surface to the bulk phase, resulting in less content of elements doped on the surface, so it is not identified on the outermost surface of the cross-section of the positive electrode active material particle to doping elements.

Compared with the batteries using the positive electrode active materials provided in Comparative Examples 1 to 4, the gram capacity of the batteries provided by the positive electrode active materials provided in Examples 1 to 10 and the capacity retention rate after 500 cycles are higher, and the reasons for the above differences are : the shallow surface layer of the ternary positive electrode active material that embodiment 1～10 provides is doped with metal element M, and its ionic radius is greater than the ionic radius of Ni ³⁺ , on the one hand, can increase the interlayer spacing of ternary positive electrode active material, reduce The transmission impedance of lithium ions in the ternary positive electrode active material ensures the rapid transmission of lithium ions in the ternary positive electrode active material, enhances the extraction and insertion of lithium ions, and improves the capacity and electrochemical performance of the ternary positive electrode active material. On the one hand, the metal element M with a larger ionic radius has a strong affinity with oxygen, which can strengthen the molecular bonding orbital and the strength of the TM-O bond by occupying the transition metal position, and can play a role in the lattice of the ternary positive electrode active material. Good supporting effect, inhibiting the loss of lattice oxygen in the ternary positive electrode active material, reducing the generation of oxygen vacancies, and at the same time inhibiting the mixing of Li ⁺ /Ni ²⁺ in the ternary positive electrode active material, thereby improving the performance of the ternary positive electrode active material structural stability, and the content A1 of the metal element M on the surface of the outermost layer of the positive electrode active material particle and the content A2 of the metal element M in the cross section of the positive electrode active material particle from the outermost layer to the center direction 40nm meet A2/A1 The relationship >0.7, on the one hand, can effectively suppress the irreversible phase transition of H2-H3 in the serious phase transition region near 40nm in the ternary cathode active material during cycling, and further improve the structural stability of the shallow surface layer of the ternary cathode active material The performance and electrochemical performance of the battery are improved, and the cycle effect of the ternary positive electrode active material is improved. When the positive electrode active material provided in Examples 1 to 10 is applied to the battery, the gram capacity of the battery and the capacity retention rate after 500 cycles are higher.

Among the ternary positive electrode active materials provided in Examples 1 to 10, when the ternary positive electrode active material provided in Example 10 is sintered in the second stage, it is first sintered at 760°C for 8 hours and then lowered to 600°C for 2 hours. , the finally prepared ternary positive electrode active material satisfies the two relational expressions of A2/A1>0.7 and A3/A1>0.6, but does not satisfy the relational expression of A4/A1>0.4, and the positive electrode active material is applied to the battery , the capacity retention rate of the battery cycle of 500 cycles is reduced; while the ternary positive electrode active material provided in Example 9 is sintered in the second stage, it is first sintered at 760°C for 5 hours and then cooled to 600°C for 5 hours. The finally prepared ternary positive electrode active material satisfies the relational expression of A2/A1>0.7, but does not satisfy the two relational expressions of A2/A1>0.7 and A3/A1>0.6, and the positive electrode active material is applied to the battery, The capacity retention rate of the battery after 500 cycles is lower than that of Example 10. The reason for the above results is: in the preparation process of the ternary positive electrode active material, the high temperature holding time was reduced during the second stage sintering, so that the doping depth of the doping element in the ternary positive electrode active material was not deep enough, resulting in the doping The content of the element is reduced, and the three relational expressions of A2/A1>0.7, A3/A1>0.6, and A4/A1>0.4 cannot be satisfied at the same time, which leads to the cycle performance of the battery containing the positive electrode active material provided by Examples 9-10. has declined.

The above embodiments are only used to illustrate the technical solutions of the present invention rather than limiting the protection scope of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be carried out Modifications or equivalent replacements, but these modifications or replacements are within the protection scope of the present invention.

Claims (9)

1. A ternary positive electrode active material with a chemical formula of LiNi _x Co _y Mn _1-xy O ₂ (0<x<1, 0<y<1, 0<x+y<1), characterized in that: The cross-section of the ternary positive electrode active material particle is the shallow surface layer from the outermost layer to the central direction of 0~100nm, and the shallow surface layer is doped with metal element M, and the ionic radius of the metal element M is larger than that of Ni ³⁺ ions radius; The content of the metal element M on the outermost surface of the particle is defined as A1, and the content of the metal element M in the cross section of the particle at 40 nm from the outermost layer to the center is defined as A2, and the A1 , The A2 satisfies: A2/A1>0.7. 2. ternary positive electrode active material as claimed in claim 1, is characterized in that: The content of the metal element M in the cross-section of the particle at 60 nm from the outermost layer to the center is defined as A3, and the A1 and A3 satisfy: A3/A1>0.6. 3. ternary positive electrode active material as claimed in claim 2, is characterized in that: The content of the metal element M in the cross-section of the particle at 100 nm from the outermost layer to the center is defined as A4, and the A1 and A4 satisfy: A4/A1>0.4. 4 . The ternary positive electrode active material according to claim 1 , wherein the metal element M is selected from at least one of niobium, titanium, tantalum, tin, and lanthanide metal elements. 5 . The ternary positive electrode active material according to claim 1 , wherein the mass content of the metal element M in the ternary positive electrode active material is 1000-2000 ppm. 6 . The ternary cathode active material according to claim 1 , wherein the particle size D50 of the ternary cathode active material is 2-5 μm. 7 . The ternary cathode active material according to claim 1 , wherein the specific surface area of the ternary cathode active material is 0.3˜1.3 m ² /g. 8. A positive electrode sheet, characterized in that it comprises the ternary positive electrode active material according to any one of claims 1-7. 9. A battery, characterized in that it comprises the ternary positive electrode active material according to any one of claims 1-7.

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