CN115832249A - High-nickel ternary positive electrode material with fast lithium ion conductor as coating layer and preparation method and application thereof - Google Patents

Abstract

The invention provides a high-nickel ternary positive electrode material with a lithium fast ion conductor as a coating layer and its preparation method and application. The chemical formula of the lithium fast ion conductor is: Li ₄ MP ₂ O ₉ ; wherein, M is Ti or V; the crystal structure of the lithium fast ion conductor is: PO ₄ tetrahedron and MO ₆ octahedron share vertices connected to form a one-dimensional chain structure, Li ions are distributed between chains and chains, and freely diffuse in at least 3 directions; The positive electrode material has a core-shell structure, including an inner core and a cladding layer; the material of the inner core includes nickel cobalt lithium manganese oxide positive electrode material. The ternary positive electrode material provided by the present invention uses lithium fast ion conductors as the coating layer, which enriches the diffusion path of lithium ions, improves lithium ion content and ion conductivity, and reduces the impedance of lithium fast ion conductors as the coating layer of positive electrode materials. , and then realize the rapid charge and discharge and high temperature cycle performance of lithium-ion batteries.

Description

A kind of high-nickel ternary positive electrode material with lithium fast ion conductor as coating layer and its preparation Method and Application

technical field

The invention belongs to the technical field of lithium ion batteries, and relates to a high-nickel ternary positive electrode material, in particular to a high-nickel ternary positive electrode material with a lithium fast ion conductor as a coating layer and a preparation method and application thereof.

Background technique

In recent years, high-nickel and ultra-high-nickel cathode materials have been the focus of future development because of their higher specific capacity. However, as the nickel content increases, so do the attendant problems. Firstly, Li ⁺ /Ni ²⁺ mixes intensified, and the cycle performance deteriorates; secondly, strong oxidizing Ni ⁴⁺ ions are formed during charging and discharging, which will have a strong side reaction with the electrolyte, which will lead to battery failure; in addition, safety The performance will be deteriorated, because the residual Li ₂ O and LiOH on the surface of the material will react with CO ₂ and H ₂ O in the air to form Li ₂ CO ₃ and other lithium salts, which will be decomposed to produce CO ₂ at a high charging potential, resulting in Safety issues such as pouch battery bulge.

In order to solve the above problems, those skilled in the art usually coat the surface of the positive electrode material, that is, build a protective barrier on the surface, so as to avoid the direct contact between the active material and the electrolyte to cause corrosion, and inhibit the dissolution of transition metals, thereby significantly improving the surface structure. stability. So far, many different types of surface coating materials have been reported in the field, such as oxides, fluorides, phosphates, lithium ion conductors, and electronic conductors.

Lithium fast ion conductors have both high ionic conductivity and excellent thermal stability, which can significantly improve the conductivity of materials and reduce internal resistance, so as to achieve fast charge and discharge and high temperature cycle performance of lithium ion batteries. Therefore, the coating modification of fast lithium ion conductors is of great significance to the improvement of the performance of lithium ion battery cathode materials. However, currently reported cladding materials for lithium fast ion conductors include lithium metaaluminate, lithium niobate, lithium titanate, lithium borate, lithium metaborate, lithium zirconate, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, titanium phosphate Lithium aluminum, lithium germanium aluminum phosphate, etc., but their crystal structures are all three-dimensional framework structure or two-dimensional layered structure, the lithium ion diffusion path is single, the ion conductivity is low, and the gram capacity and rate performance of the positive electrode material cannot be fully utilized.

CN 103466588A discloses a preparation method of NASICON type lithium fast ion conductor, comprising: adding tetrabutyl titanate into citric acid solution and stirring evenly, adding lithium nitrate, aluminum nitrate and diammonium hydrogen phosphate citric acid solution, stirring Evenly add ethylene glycol, stir after rising to a certain temperature to make it gel completely; the gel is dried to obtain a xerogel, and the xerogel is ground and calcined to obtain a precursor powder; after grinding the precursor powder to a fine powder , and isostatically pressed on a tablet machine to obtain a NASICON type lithium fast ion conductor electrolyte sheet. However, the crystal structure of the NASICON-type lithium fast ion conductor obtained by the invention is a three-dimensional framework structure formed by interconnecting the corners of the MO ₆ octahedron and the AO ₄ tetrahedron, which has low lithium ion content and insufficient lithium ion diffusion channels. And the problem of low ionic conductivity, there is still a lot of room for improvement.

It can be seen from this that how to provide a high-nickel ternary positive electrode material with a lithium fast ion conductor as a coating layer, further enrich the diffusion path of lithium ions, increase the lithium ion content and ion conductivity, and reduce the lithium fast ion conductor as a positive electrode material. The impedance of the coating, and then realizing the rapid charge and discharge and high temperature cycle performance of the lithium-ion battery, has become an urgent problem to be solved by those skilled in the art.

Contents of the invention

The object of the present invention is to provide a high-nickel ternary positive electrode material with a lithium fast ion conductor as a coating layer and its preparation method and application. The ternary positive electrode material uses a lithium fast ion conductor as a coating layer to enrich lithium ions. The diffusion path improves the lithium ion content and ion conductivity, reduces the impedance of the lithium fast ion conductor as the coating layer of the positive electrode material, and then realizes the rapid charge and discharge and high temperature cycle performance of the lithium ion battery.

To achieve this purpose of the invention, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a lithium fast ion conductor as a positive electrode material for a coating layer, the chemical formula of the lithium fast ion conductor is: Li ₄ MP ₂ O ₉ ; wherein, M is Ti or V.

The crystal structure of the lithium fast ion conductor is: PO ₄ tetrahedra and MO ₆ octahedrons share vertices to form a one-dimensional chain structure, Li ions are distributed between chains and can freely diffuse in at least three directions.

The positive electrode material has a core-shell structure, including an inner core and a cladding layer.

The material of the inner core includes nickel cobalt lithium manganese oxide positive electrode material.

The positive electrode material provided by the present invention uses lithium fast ion conductors as the coating layer, wherein the lithium fast ion conductors present a one-dimensional chain structure on the crystal structure, and free lithium ions can freely diffuse in multiple directions in three-dimensional space, further The diffusion path of lithium ions is enriched, the content of lithium ions and ion conductivity are increased, and the impedance of its coating layer as a positive electrode material is reduced, thereby realizing the rapid charge and discharge and high temperature cycle performance of lithium ion batteries.

In addition, the present invention coats the lithium fast ion conductor with high ion conductivity on the positive electrode material of lithium nickel cobalt manganese oxide, which reduces the contact area between the electrolyte and the positive electrode material, thereby inhibiting the side reactions between the electrode materials and improving the battery life. cycle stability.

Preferably, the common vertices of the MO ₆ octahedra are connected sequentially, and each PO ₄ tetrahedron is independently connected to the common vertices of two adjacent MO ₆ octahedra.

Preferably, the mass ratio of the cladding layer to the inner core is 0.1-0.3wt%, for example, it can be 0.1wt%, 0.12wt%, 0.14wt%, 0.16wt%, 0.18wt%, 0.2wt%, 0.22wt%, 0.24wt%, 0.26wt%, 0.28wt% or 0.3wt%, but not limited to the listed values, other unlisted values within the range of values are also applicable.

In a second aspect, the present invention provides a method for preparing the positive electrode material as described in the first aspect, the preparation method comprising the following steps:

(1) preparation of lithium fast ion conductor;

(2) Preparation of nickel cobalt lithium manganese oxide positive electrode material;

(3) Mix lithium fast ion conductors, nano-carbon particles, and nickel-cobalt lithium manganese oxide positive electrode materials for fusion coating, and obtain lithium fast ion conductors as the positive electrode materials for the coating layer after annealing;

Wherein, steps (1) and (2) are in no particular order.

Preferably, the preparation method of lithium fast ion conductor described in step (1) comprises the following steps:

(1.1) Mix titanium source or vanadium source, lithium source, phosphorus source, templating agent, organic solvent and deionized water according to the stoichiometric ratio for hydrothermal synthesis to obtain Li ₄ MP ₂ O ₉ crystals;

(1.2) The Li ₄ MP ₂ O ₉ crystals obtained in step (1.1) were washed, dried and ground in sequence to obtain the Li ₄ MP ₂ O ₉ lithium fast ion conductor.

The present invention combines a series of post-treatment processes to prepare Li ₄ MP ₂ O ₉ lithium fast ion conductors on the basis of hydrothermal synthesis. The raw materials are simple and easy to obtain, the preparation process is simple, the preparation efficiency is improved, and the preparation cost is reduced. Facilitate large-scale promotion and application.

Preferably, the titanium source in step (1.1) includes titanium dioxide.

Preferably, the vanadium source in step (1.1) includes vanadium trioxide.

Preferably, the lithium source in step (1.1) includes lithium chloride.

Preferably, the phosphorus source in step (1.1) includes a phosphoric acid solution, and the concentration of the phosphoric acid solution is 80-90wt%, such as 80wt%, 81wt%, 82wt%, 83wt%, 84wt%, 85wt%, 86wt% %, 87wt%, 88wt%, 89wt% or 90wt%, but not limited to the listed values, other unlisted values within the range of values are also applicable.

Preferably, the templating agent in step (1.1) includes any one or a combination of at least two of ethylenediamine, triethylamine, tetraethylenepentamine or pentaethylenetetramine, typical but non-limiting combinations include ethyl A combination of diamine and tetraethylenepentamine, a combination of ethylenediamine and pentaethylenetetramine, a combination of triethylamine and tetraethylenepentamine, or a combination of triethylamine and pentaethylenetetramine, more preferably ethylenediamine combination with pentaethylenetetramine, or triethylamine with tetraethylenepentamine.

Preferably, the organic solvent in step (1.1) includes sec-butanol.

Preferably, the mixing method described in step (1.1) includes: first adding titanium source or vanadium source, lithium source into deionized water, then adding organic solvent and templating agent in sequence, and finally adding phosphoric acid solution and stirring evenly.

Preferably, the temperature of the hydrothermal synthesis in step (1.1) is 210-220°C, such as 210°C, 211°C, 212°C, 213°C, 214°C, 215°C, 216°C, 217°C, 218°C, 219°C or 220°C, but not limited to the listed values, other unlisted values within this range are also applicable.

Preferably, the hydrothermal synthesis time in step (1.1) is 36-48h, for example, it can be 36h, 38h, 40h, 42h, 44h, 46h or 48h, but it is not limited to the listed values, other values within the range Values not listed also apply.

Preferably, the washing in step (1.2) is performed with deionized water until the Li ₄ MP ₂ O ₉ crystals are clear and free of impurities.

Preferably, suction filtration is also included between washing and drying in step (1.2).

Preferably, the drying in step (1.2) is carried out in an oven, and the set temperature of the oven is 80-120°C, such as 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C , 115°C or 120°C, but not limited to the listed values, other unlisted values within this range are also applicable.

Preferably, the step (1.2) grinds until the Li ₄ MP ₂ O ₉ lithium fast ion conductor satisfies D50≤0.1 μm, for example, D50=0.01 μm, 0.02 μm, 0.03 μm, 0.04 μm, 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm or 0.1 μm, but not limited to the listed values, other unlisted values within this range are also applicable.

In the present invention, the D50 specifically refers to the particle size corresponding to when the cumulative particle size distribution percentage of the lithium fast ion conductor reaches 50%, and its physical meaning is that particles with a particle size larger than it account for 50%, and particles smaller than it also account for 50 %.

Preferably, the preparation method of the nickel-cobalt lithium manganese oxide cathode material in step (2) includes dry sintering and crushing and sieving.

Preferably, the temperature of the annealing treatment in step (3) is 250-350°C, such as 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C °C or 350 °C, but not limited to the listed values, other unlisted values within this range are also applicable.

As a preferred technical solution of the second aspect of the present invention, the preparation method includes the following steps:

(1) Prepare lithium fast ion conductor, specifically:

(1.1) Add titanium dioxide or vanadium trioxide and lithium chloride to deionized water according to the stoichiometric ratio, then add sec-butanol and templating agent successively, and finally add a phosphoric acid solution with a concentration of 80-90wt% and stir evenly, at 210 Perform hydrothermal synthesis at -220°C for 36-48 hours to obtain Li ₄ MP ₂ O ₉ crystals; the template includes any one of ethylenediamine, triethylamine, tetraethylenepentamine or pentaethylenetetramine or at least a combination of the two;

(1.2) Wash the Li ₄ MP ₂ O ₉ crystals obtained in step (1.1) until they are clear and free of impurities, filter with suction, dry at 80-120°C, and grind until D50≤0.1 μm to obtain Li ₄ MP ₂ O ₉ Lithium fast ion conductor.

(2) The nickel-cobalt lithium manganese oxide positive electrode material is prepared by successive dry sintering and crushing and sieving;

(3) Mix lithium fast ion conductors, nano-carbon particles, and nickel-cobalt lithium manganese oxide positive electrode materials for fusion coating, and obtain lithium fast ion conductors as the positive electrode materials of the coating layer after annealing at 250-350°C;

Wherein, steps (1) and (2) are in no particular order.

In a third aspect, the present invention provides an application of the cathode material as described in the first aspect in lithium-ion batteries.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The cathode material provided by the present invention uses lithium fast ion conductors as the coating layer, wherein the lithium fast ion conductors present a one-dimensional chain structure on the crystal structure, and free lithium ions can freely move in multiple directions in three-dimensional space. Diffusion further enriches the diffusion path of lithium ions, increases the content of lithium ions and ion conductivity, reduces the impedance of its coating layer as a positive electrode material, and then realizes the rapid charge and discharge and high temperature cycle performance of lithium ion batteries;

(2) In the present invention, the lithium fast ion conductor with high ion conductivity is coated on the nickel-cobalt lithium manganese oxide positive electrode material, which reduces the contact area between the electrolyte and the positive electrode material, thereby suppressing the side reactions between the electrode materials and improving the The cycle stability of the battery.

Description of drawings

Fig. 1 is the lithium fast ion conductor crystal structure schematic diagram provided by the present invention;

Fig. 2 is the change diagram of the capacity retention rate of the lithium-ion battery made by using the high-nickel positive electrode material obtained in Application Example 3-4 and Comparative Application Example 1-2 after 50 cycles;

Fig. 3 is the rate performance diagram of the lithium-ion battery made by using the high-nickel positive electrode material obtained in Application Example 3-4 and Comparative Application Example 1-2;

Fig. 4 is the rate performance figure of the lithium ion battery that utilizes application examples 1, 3, 5 and comparative application example 1 obtained high-nickel cathode material to make;

Fig. 5 is a graph of the rate performance of lithium-ion batteries made of the high-nickel cathode materials obtained in Application Examples 2, 4, 6 and Comparative Application Example 1.

Among them: 1-PO ₄ tetrahedron; 2-MO ₆ octahedron (M is Ti or V); 3-Li ion.

Detailed ways

The technical solutions of the present invention will be further described below through specific embodiments. It should be clear to those skilled in the art that the embodiments are only for helping to understand the present invention, and should not be regarded as specific limitations on the present invention.

Example 1

This implementation provides a lithium fast ion conductor and a preparation method thereof, the preparation method comprising the following steps:

(1) First add titanium dioxide (22.80g) and lithium chloride (33.95g) into a 500mL polytetrafluoroethylene liner filled with 50mL deionized water, then add sec-butanol (100mL) and triethylamine (50mL ) and tetraethylenepentamine (150mL), and finally add phosphoric acid solution (25mL) with a concentration of 85wt% to the lining, and stir evenly with a glass rod; package the polytetrafluoroethylene lining in a stainless steel sleeve, and place it at 215°C Stand the reaction in an oven for 48 hours for hydrothermal synthesis. After the reaction, take out the reactor and cool to room temperature to obtain Li ₄ TiP ₂ O ₉ crystals;

(2) Wash the Li ₄ TiP ₂ O ₉ crystals obtained in step (1) successively with deionized water until they are clear and free of impurities, then filter them with suction, and dry them in an oven at 100°C for 6 hours to obtain Li ₄ TiP ₂ O ₉ crystals grains; grind the obtained grains to D50≤0.1 μm to obtain Li ₄ TiP ₂ O ₉ lithium fast ion conductor.

The crystal structure of the Li ₄ TiP ₂ O ₉ lithium fast ion conductor obtained in this example is shown in Figure 1. The PO ₄ tetrahedron 1 and the TiO ₆ octahedron 2 share vertices connected to form a one-dimensional chain structure, specifically: TiO ₆ octahedron The 2 common vertices are connected sequentially, and each PO ₄ tetrahedron 1 is independently connected to two adjacent TiO ₆ octahedral 2 common vertices, and free Li ions 3 can freely diffuse in multiple directions in three-dimensional space.

Example 2

This implementation provides a lithium fast ion conductor and a preparation method thereof, the preparation method comprising the following steps:

(1) First add vanadium trioxide (21.38g) and lithium chloride (33.95g) into a 500mL polytetrafluoroethylene liner filled with 50mL deionized water, then add sec-butanol (100mL) and triethyl alcohol in sequence. amine (50mL) and tetraethylenepentamine (150mL), and finally add phosphoric acid solution (25mL) with a concentration of 85wt% to the lining, and stir evenly with a glass rod; encapsulate the polytetrafluoroethylene lining in a stainless steel sleeve, place Put it in an oven at 215°C for 48 hours to carry out hydrothermal synthesis. After the reaction, take out the reactor and cool to room temperature to obtain Li ₄ VP ₂ O ₉ crystals;

(2) The Li ₄ VP ₂ O ₉ crystals obtained in step (1) were washed with deionized water until they were clear and free of impurities, suction filtered, and dried in an oven at 100°C for 6 hours to obtain Li ₄ VP ₂ O ₉ crystals grains; grind the obtained grains to D50≤0.1 μm to obtain Li ₄ VP ₂ O ₉ lithium fast ion conductor.

The crystal structure of the Li ₄ VP ₂ O ₉ lithium fast ion conductor obtained in this example is shown in Figure 1. PO ₄ tetrahedron 1 and VO ₆ octahedron 2 share vertices connected to form a one-dimensional chain structure, specifically: VO ₆ octahedron The 2 common vertices are connected sequentially, and each PO ₄ tetrahedron 1 is independently connected to the common vertices of two adjacent VO ₆ octahedron 2, and free Li ions 3 can freely diffuse in multiple directions in three-dimensional space.

Example 3

This implementation provides a lithium fast ion conductor and a preparation method thereof, the preparation method comprising the following steps:

(1) First add titanium dioxide (22.80g) and lithium chloride (33.95g) into a 500mL polytetrafluoroethylene liner filled with 50mL deionized water, then add sec-butanol (100mL), ethylenediamine (50mL ) and pentaethylenetetramine (150mL), and finally add phosphoric acid solution (25mL) with a concentration of 80wt% to the lining, and stir evenly with a glass rod; package the polytetrafluoroethylene lining in a stainless steel sleeve, and place it at 210°C Stand the reaction in an oven for 48 hours for hydrothermal synthesis. After the reaction, take out the reactor and cool to room temperature to obtain Li ₄ TiP ₂ O ₉ crystals;

(2) Wash the Li ₄ TiP ₂ O ₉ crystals obtained in step (1) successively with deionized water until they are clear and free of impurities, then filter them with suction, and dry them in an oven at 80°C for 8 hours to obtain Li ₄ TiP ₂ O ₉ crystals grains; grind the obtained grains to D50≤0.1 μm to obtain Li ₄ TiP ₂ O ₉ lithium fast ion conductor.

The crystal structure of the Li ₄ TiP ₂ O ₉ lithium fast ion conductor obtained in this example is shown in Figure 1. The PO ₄ tetrahedron 1 and the TiO ₆ octahedron 2 share vertices connected to form a one-dimensional chain structure, specifically: TiO ₆ octahedron The 2 common vertices are connected sequentially, and each PO ₄ tetrahedron 1 is independently connected to two adjacent TiO ₆ octahedral 2 common vertices, and free Li ions 3 can freely diffuse in multiple directions in three-dimensional space.

Example 4

This implementation provides a lithium fast ion conductor and a preparation method thereof, the preparation method comprising the following steps:

(1) First add vanadium trioxide (21.38g) and lithium chloride (33.95g) into a 500mL polytetrafluoroethylene liner filled with 50mL deionized water, then add sec-butanol (100mL), ethylene dichloride in sequence amine (50mL) and pentaethylenetetramine (150mL), and finally add phosphoric acid solution (25mL) with a concentration of 90wt% to the lining, and stir evenly with a glass rod; encapsulate the polytetrafluoroethylene lining in a stainless steel sleeve, place Stand the reaction in an oven at 220°C for 36 hours for hydrothermal synthesis. After the reaction, take out the reactor and cool to room temperature to obtain Li ₄ VP ₂ O ₉ crystals;

(2) The Li ₄ VP ₂ O ₉ crystals obtained in step (1) were washed with deionized water in sequence until they were clear and free of impurities, suction filtered, and dried in an oven at 120°C for 4 hours to obtain Li ₄ VP ₂ O ₉ crystals grains; grind the obtained grains to D50≤0.1 μm to obtain Li ₄ VP ₂ O ₉ lithium fast ion conductor.

The crystal structure of the Li ₄ VP ₂ O ₉ lithium fast ion conductor obtained in this example is shown in Figure 1. PO ₄ tetrahedron 1 and VO ₆ octahedron 2 share vertices connected to form a one-dimensional chain structure, specifically: VO ₆ octahedron The 2 common vertices are connected sequentially, and each PO ₄ tetrahedron 1 is independently connected to the common vertices of two adjacent VO ₆ octahedron 2, and free Li ions 3 can freely diffuse in multiple directions in three-dimensional space.

Application example 1

This application example provides a lithium fast ion conductor obtained in Example 1 as a positive electrode material for a coating layer and a preparation method thereof, the preparation method comprising the following steps:

(1) Mix 5 kg of Ni _0.83 Co _0.05 Mn _0.12 (OH) ₂ ternary precursor and 2.35 kg of lithium hydroxide in a high-mixer, and then carry out the process at 800°C under an oxygen atmosphere (5m ³ /h) Dry sintering for 12 hours, and finally crushed and sieved to obtain a high-nickel cathode material;

(2) the gained lithium fast ion conductor (5.88g) of embodiment 1, ultra-fine nano-carbon particle (5g) and step (1) gained high-nickel positive electrode material (500g) are added in the high-speed mixer and carry out dry mixing, Put the mixed raw materials into the fusion coating machine. Under the action of blade shear force, the interface between the positive electrode material and the coating material achieves a fusion effect; the coated positive electrode material is annealed at a low temperature (300 ° C), and finally Li ₄ TiP ₂ O ₉ coated high-nickel cathode material NCM-0.1wt% Li ₄ TiP ₂ O ₉ .

Application example 2

This application example provides a lithium fast ion conductor obtained in Example 2 as a positive electrode material for a coating layer and a preparation method thereof, and the preparation method includes the following steps:

(1) Mix 5 kg of Ni _0.83 Co _0.05 Mn _0.12 (OH) ₂ ternary precursor and 2.35 kg of lithium hydroxide in a high-mixer, and then carry out the process at 800°C under an oxygen atmosphere (5m ³ /h) Dry sintering for 12 hours, and finally crushed and sieved to obtain a high-nickel cathode material;

(2) the gained lithium fast ion conductor (5.94g) of embodiment 2, ultra-fine nano-carbon particle (5g) and step (1) gained high-nickel positive electrode material (500g) are added in the high-speed mixer and carry out dry mixing, Put the mixed raw materials into the fusion coating machine. Under the action of blade shear force, the interface between the positive electrode material and the coating material achieves a fusion effect; the coated positive electrode material is annealed at a low temperature (300 ° C), and finally Li ₄ VP ₂ O ₉ coated high-nickel cathode material NCM-0.1wt% Li ₄ VP ₂ O ₉ .

Application example 3

This application example provides a lithium fast ion conductor obtained in Example 1 as a positive electrode material for a coating layer and a preparation method thereof, the preparation method comprising the following steps:

(1) Mix 5 kg of Ni _0.83 Co _0.05 Mn _0.12 (OH) ₂ ternary precursor and 2.35 kg of lithium hydroxide in a high-mixer, and then carry out the process at 800°C under an oxygen atmosphere (5m ³ /h) Dry sintering for 12 hours, and finally crushed and sieved to obtain a high-nickel cathode material;

(2) the gained lithium fast ion conductor (11.76g) of embodiment 1, ultra-fine nano-carbon particle (5g) and step (1) gained high-nickel positive electrode material (500g) are added in the high-speed mixer and carry out dry mixing, Put the mixed raw materials into the fusion coating machine. Under the action of blade shear force, the interface between the positive electrode material and the coating material achieves a fusion effect; the coated positive electrode material is annealed at a low temperature (300 ° C), and finally Li ₄ TiP ₂ O ₉ coated high-nickel cathode material NCM-0.2wt% Li ₄ TiP ₂ O ₉ .

Application example 4

This application example provides a lithium fast ion conductor obtained in Example 2 as a positive electrode material for a coating layer and a preparation method thereof, and the preparation method includes the following steps:

(1) Mix 5 kg of Ni _0.83 Co _0.05 Mn _0.12 (OH) ₂ ternary precursor and 2.35 kg of lithium hydroxide in a high-mixer, and then carry out the process at 800°C under an oxygen atmosphere (5m ³ /h) Dry sintering for 12 hours, and finally crushed and sieved to obtain a high-nickel cathode material;

(2) the gained lithium fast ion conductor (11.88g) of embodiment 2, ultra-fine nano-carbon particle (5g) and step (1) gained high-nickel positive electrode material (500g) are added in the high-speed mixer and carry out dry mixing, Put the mixed raw materials into the fusion coating machine. Under the action of blade shear force, the interface between the positive electrode material and the coating material achieves a fusion effect; the coated positive electrode material is annealed at a low temperature (300 ° C), and finally Li ₄ VP ₂ O ₉ coated high-nickel cathode material NCM-0.2wt% Li ₄ VP ₂ O ₉ .

Application example 5

This application example provides a lithium fast ion conductor obtained in Example 1 as a positive electrode material for a coating layer and a preparation method thereof, the preparation method comprising the following steps:

(1) Mix 5 kg of Ni _0.83 Co _0.05 Mn _0.12 (OH) ₂ ternary precursor and 2.35 kg of lithium hydroxide in a high-mixer, and then carry out the process at 800°C under an oxygen atmosphere (5m ³ /h) Dry sintering for 12 hours, and finally crushed and sieved to obtain a high-nickel cathode material;

(2) the gained lithium fast ion conductor (17.64g) of embodiment 1, ultrafine nano-carbon particle (5g) and step (1) gained high-nickel positive electrode material (500g) are added in the high-speed mixer and carry out dry mixing, Put the mixed raw materials into the fusion coating machine. Under the action of blade shear force, the interface between the positive electrode material and the coating material achieves a fusion effect; the coated positive electrode material is annealed at a low temperature (300 ° C), and finally Li ₄ TiP ₂ O ₉ coated high-nickel cathode material NCM-0.3wt% Li ₄ TiP ₂ O ₉ .

Application example 6

This application example provides a lithium fast ion conductor obtained in Example 2 as a positive electrode material for a coating layer and a preparation method thereof, and the preparation method includes the following steps:

(1) Mix 5 kg of Ni _0.83 Co _0.05 Mn _0.12 (OH) ₂ ternary precursor and 2.35 kg of lithium hydroxide in a high-mixer, and then carry out the process at 800°C under an oxygen atmosphere (5m ³ /h) Dry sintering for 12 hours, and finally crushed and sieved to obtain a high-nickel cathode material;

(2) the obtained lithium fast ion conductor (17.82g) of embodiment 2, ultrafine nano-carbon particles (5g) and step (1) gained high-nickel positive electrode material (500g) are added in the high-speed mixer and carry out dry mixing, Put the mixed raw materials into the fusion coating machine. Under the action of blade shear force, the interface between the positive electrode material and the coating material achieves a fusion effect; the coated positive electrode material is annealed at a low temperature (300 ° C), and finally Li ₄ VP ₂ O ₉ coated high-nickel cathode material NCM-0.3wt% Li ₄ VP ₂ O ₉ .

Comparative application example 1

This comparative application example provides a positive electrode material and a preparation method thereof. The preparation method is as follows: 5 kg of Ni _0.83 Co _0.05 Mn _0.12 (OH) ₂ ternary precursor and 2.35 kg of lithium hydroxide are prepared in a high-mixer After mixing, dry sintering was carried out at 800° C. under an oxygen atmosphere (5 m ³ /h) for 12 hours, and finally crushed and sieved to obtain NCM, a high-nickel cathode material.

Comparative application example 2

This comparative application example provides a kind of _LiAlO as the positive electrode material of coating layer and preparation method thereof, and described preparation method comprises the following steps:

(1) Mix 5 kg of Ni _0.83 Co _0.05 Mn _0.12 (OH) ₂ ternary precursor and 2.35 kg of lithium hydroxide in a high-mixer, and then carry out the process at 800°C under an oxygen atmosphere (5m ³ /h) Dry sintering for 12 hours, and finally crushed and sieved to obtain a high-nickel cathode material;

(2) LiAlO ₂ powder (2.44g), ultra-fine carbon nano-particles (5g) and step (1) gained high-nickel positive electrode material (500g) are added in the high-speed mixer and carry out dry mixing, and after mixing The raw materials are put into the fusion coating machine, and under the action of blade shear force, the interface between the positive electrode material and the coating material achieves a fusion effect; the coated positive electrode material is annealed at low temperature (300 ° C), and finally the LiAlO ₂ coated high Nickel cathode material NCM-0.2wt% LiAlO ₂ .

Using the high-nickel positive electrode materials obtained in Application Examples 1-6 and Comparative Application Examples 1-2 to independently prepare lithium-ion batteries, and the preparation method specifically includes the following steps:

(1) Preparation of positive electrode sheet: Weigh the positive electrode material, polyvinylidene fluoride (PVDF) and conductive carbon (SuperP) respectively according to the mass ratio of 85:5:10, and then use a magnetic stirrer to stir a certain amount of 1-methyl- 2-Pyrrolidone (NMP) and PVDF are uniformly dissolved, then add the positive electrode material and conductive carbon and stir together; the mixed slurry is fully stirred evenly by a magnetic stirrer, and the aluminum foil collector is cleaned with absolute ethanol and the slurry is applied to ensure The smearing thickness is uniform without air bubbles; the smeared slurry is placed in a blast drying oven with a set temperature of 70 ° C for 10 hours; the dried positive electrode sheet is cut into a disc with a diameter of about 12 mm by a slicer, and then The pole pieces were weighed one by one, placed in a vacuum drying oven at 100°C for 10 hours, and finally moved to a glove box to prepare for battery assembly.

(2) Assemble the battery: In a vacuum glove box under the protection of argon, the positive electrode material prepared above, the high-voltage resistant electrolyte of LiPF ₆ +EC/DEC (volume ratio 1:1), Celgard2400 diaphragm and metal lithium The sheet-to-electrodes are assembled into a button battery, and finally the battery is sealed by MSK-110 button battery sealing machine, and the 2025 button half battery is obtained; the battery is taken out of the glove box, and the related test can be carried out after standing for about 10 hours.

Fig. 2 is a graph showing the change in capacity retention rate of lithium-ion batteries made by using the high-nickel cathode materials obtained in Application Example 3-4 and Comparative Application Example 1-2 after 50 cycles.

It can be seen from Figure 2 that after application examples 3 and 4 use Li ₄ MP ₂ O ₉ fast ion conductor to coat nickel-cobalt lithium manganese oxide, the 0.5C/50 cycle capacity retention rate of the battery prepared by the positive electrode material is significantly improved, and the highest It can reach 98.4%, which is about 3 percentage points higher than that of comparative application example 1; compared with comparative application example 2, the capacity retention rate of application examples 3 and 4 is slightly lower in the first 30 cycles, but after 30 cycles, application examples 3 and 4 The capacity retention rate is more advantageous.

It can be seen that the present _invention uniformly coats nickel-cobalt lithium manganese oxide through _{the Li4MP2O9} fast ion conductor, hinders the direct contact between the electrolyte and nickel-cobalt lithium manganese oxide, reduces the frequency of side reactions, and improves the The cycle stability of the battery.

Fig. 3 is a graph of the rate performance of lithium-ion batteries prepared by using the high-nickel cathode materials obtained in Application Example 3-4 and Comparative Application Example 1-2.

It can be seen from Figure 3 that the present invention uniformly coats nickel-cobalt lithium manganese oxide through the Li ₄ MP ₂ O ₉ fast ion conductor, which reduces the interface impedance and improves the rate performance of the battery. It can be seen from the performance test that the application example 3 and 4 After coating nickel-cobalt lithium manganate with Li ₄ MP ₂ O ₉ fast ion conductor, when the battery prepared by this positive electrode material is discharged at 0.5C and 1C rates, the discharge capacity is slightly higher than that of Comparative Application Examples 1 and 2; continue When the discharge rate is increased to 2C and 4C, the advantages of application examples 3 and 4 can be clearly brought into play.

Fig. 4 is a graph of the rate performance of lithium-ion batteries made of the high-nickel cathode materials obtained in Application Examples 1, 3, 5 and Comparative Application Example 1.

It can be seen from Figure 4 that the present invention evenly coats nickel-cobalt lithium manganese oxide through the Li ₄ TiP ₂ O ₉ fast ion conductor, which reduces the interface impedance and improves the rate performance of the battery. It can be seen from the performance test that the application example 1, 3 and 5 use Li ₄ TiP ₂ O ₉ fast ion conductor to coat nickel-cobalt-lithium manganese oxide, when the battery prepared by this positive electrode material is discharged at 0.5C and 1C rate, the discharge capacity is slightly higher than that of Comparative Application Example 1; continue to increase When the discharge rate reaches 2C and 4C, the advantages of application examples 1, 3 and 5 are more obvious. Compared with application examples 1, 3 and 5, application example 3 (coated with 0.2% Li ₄ TiP ₂ O ₉ ) has the best rate performance, followed by application example 1 (coated with 0.1% Li ₄ TiP ₂ O ₉ ) , application example 5 (coating 0.3% Li ₄ TiP ₂ O ₉ ) Again, it can be seen that the amount of coated Li ₄ TiP ₂ O ₉ fast ion conductor has an important influence on the rate performance of the nickel cobalt lithium manganate cathode material, If it is too high or too low, the rate performance will decrease, so 0.2% Li ₄ TiP ₂ O ₉ is preferred for coating in the present invention.

Fig. 5 is a graph of the rate performance of lithium-ion batteries made of the high-nickel cathode materials obtained in Application Examples 2, 4, 6 and Comparative Application Example 1.

It can be seen from Figure 5 that the present invention evenly coats nickel-cobalt lithium manganese oxide through the Li ₄ VP ₂ O ₉ fast ion conductor, which reduces the interface impedance and improves the rate performance of the battery. It can be seen from the performance test that the application example 2, 4 and 6 use Li ₄ VP ₂ O ₉ fast ion conductor to coat nickel cobalt lithium manganese oxide, when the battery prepared by this positive electrode material is discharged at 0.5C and 1C rate, the discharge capacity is slightly higher than that of comparative application example 1; continue to increase When the discharge rate reaches 2C and 4C, the advantages of application examples 2, 4 and 6 are more obvious. Compared with application examples 2, 4 and 6, application example 4 (coated with 0.2% Li ₄ VP ₂ O ₉ ) has the best rate performance, followed by application example 2 (coated with 0.1% Li ₄ VP ₂ O ₉ ) , application example 6 (coated with 0.3% Li ₄ VP ₂ O ₉ ) Again, it can be seen that the amount of coated Li ₄ VP ₂ O ₉ fast ion conductor has an important influence on the rate performance of the nickel cobalt lithium manganese oxide cathode material, If it is too high or too low, the rate performance will decrease, so 0.2% Li ₄ VP ₂ O ₉ is preferred for coating in the present invention.

It can be seen that the positive electrode material provided by the present invention uses lithium fast ion conductors as the cladding layer, and the lithium fast ion conductors are in a one-dimensional chain structure on the crystal structure, and free lithium ions can move in multiple directions in three-dimensional space. Free diffusion further enriches the diffusion path of lithium ions, increases the content of lithium ions and ion conductivity, reduces the impedance of its coating layer as a positive electrode material, and then realizes the rapid charge and discharge and high temperature cycle performance of lithium ion batteries.

In addition, the present invention combines a series of post-treatment processes to prepare Li4MP2O9 lithium fast ion conductors on the basis of hydrothermal synthesis. The raw materials are simple and easy to obtain, the preparation process is simple, the preparation efficiency is improved, and the preparation cost is reduced at the same time, which is beneficial to large-scale Promote apps.

Further, the present invention coats the lithium fast ion conductor with high ionic conductivity on the nickel-cobalt lithium manganese oxide positive electrode material, which reduces the contact area between the electrolyte and the positive electrode material, thereby suppressing the side reactions between the electrode materials and improving the The cycle stability of the battery.

The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, and those skilled in the art should understand that any person skilled in the art should be aware of any disclosure in the present invention Within the technical scope, easily conceivable changes or substitutions all fall within the scope of protection and disclosure of the present invention.

Claims (10)

1. A lithium fast ion conductor as the positive electrode material of the coating layer, characterized in that, the chemical formula of the lithium fast ion conductor is: Li ₄ MP ₂ O ₉ ; Wherein, M is Ti or V; The crystal structure of the lithium fast ion conductor is: PO ₄ tetrahedra and MO ₆ octahedron share vertices to form a one-dimensional chain structure, Li ions are distributed between chains and freely diffuse in at least 3 directions; The positive electrode material is a core-shell structure, including an inner core and a cladding layer; The material of the inner core includes nickel cobalt lithium manganese oxide positive electrode material. 2. The positive electrode material according to claim 1, wherein the MO ₆ octahedrons are connected in sequence with common vertices, and each 1 PO ₄ tetrahedron is independently connected to two adjacent MO ₆ octahedrons. Common vertex connections. 3. The positive electrode material according to claim 1 or 2, characterized in that, the mass ratio of the cladding layer to the inner core is 0.1-0.3 wt%. 4. A method for preparing the positive electrode material according to any one of claims 1-3, wherein the method for preparing comprises the following steps: (1) preparation of lithium fast ion conductor; (2) preparation of nickel cobalt lithium manganese oxide positive electrode material; (3) Mix lithium fast ion conductors, nano-carbon particles, and nickel-cobalt lithium manganese oxide positive electrode materials for fusion coating, and obtain lithium fast ion conductors as the positive electrode materials for the coating layer after annealing; Wherein, steps (1) and (2) are in no particular order. 5. preparation method according to claim 4, is characterized in that, the preparation method of step (1) described lithium fast ion conductor comprises the following steps: (1.1) Mix titanium source or vanadium source, lithium source, phosphorus source, templating agent, organic solvent and deionized water according to the stoichiometric ratio for hydrothermal synthesis to obtain Li ₄ MP ₂ O ₉ crystals; (1.2) The Li ₄ MP ₂ O ₉ crystals obtained in step (1.1) were washed, dried and ground in sequence to obtain the Li ₄ MP ₂ O ₉ lithium fast ion conductor. 6. The preparation method according to claim 5, characterized in that, the titanium source described in step (1.1) comprises titanium dioxide; Preferably, the vanadium source described in step (1.1) comprises vanadium trioxide; Preferably, the lithium source described in step (1.1) includes lithium chloride; Preferably, the phosphorus source in step (1.1) includes phosphoric acid solution, and the concentration of the phosphoric acid solution is 80-90wt%; Preferably, the templating agent in step (1.1) includes any one or a combination of at least two of ethylenediamine, triethylamine, tetraethylenepentamine or pentaethylenetetramine; Preferably, the organic solvent in step (1.1) includes sec-butanol. 7. according to the described preparation method of claim 5 or 6, it is characterized in that, the method for mixing described in step (1.1) comprises: earlier adding titanium source or vanadium source, lithium source into deionized water, then adding organic solvent and Templating agent, finally add phosphoric acid solution and stir evenly; Preferably, the temperature of the hydrothermal synthesis in step (1.1) is 210-220°C; Preferably, the hydrothermal synthesis time of step (1.1) is 36-48h. 8. The preparation method according to any one of claims 5-7, characterized in that, the washing in step (1.2) is performed _{with deionized} water until _Li4MP2O9 crystals are clear and free of impurities; Preferably, suction filtration is also included between the washing and drying in step (1.2); Preferably, the drying in step (1.2) is carried out in an oven, and the set temperature of the oven is 80-120°C; Preferably, the step (1.2) grinds until the Li ₄ MP ₂ O ₉ lithium fast ion conductor satisfies D50≤0.1 μm. 9. The preparation method according to any one of claims 4-8, characterized in that, the preparation method of the nickel-cobalt lithium manganese oxide positive electrode material described in step (2) comprises dry sintering and crushing and sieving; Preferably, the temperature of the annealing treatment in step (3) is 250-350°C. 10. An application of the cathode material according to any one of claims 1-3 in lithium ion batteries.

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