CN100495775C - Lithium ion secondary battery cathode material zirconium, phosphorus doped lithium cobalt oxide and preparation method thereof - Google Patents

Abstract

This invention relates to LiCoO2 doped with Zr and P, positive material of Li ionic secondary cells and its preparation method characterizing that the chemical formula is: LiZrxCo(1-x-y)PyO2, in which, it is a laminated structure, and x=0.001-0.003, y=0.02-06, the preparation steps are as folow: 1, mixing Co3O4, CoCO3 or CoC2O4 with Li2CO3 or LiOH in the atomic ratio of Li and Co(0.9801.05) :1.00, 2, baking it for 6-24h under 600-1000deg.C, 3, crushing LiCoO2 to particles of 6-15mum, 4, mixing the LiCoO2 and water 1-3times weight into pulp, 5, adding ZrNO3 and phosphate at the same time, 6, spraying and drying it, 7, baking it for 4-12h under 600-1000deg.C, 8, crushing the doped LiCoO2 to particles of 6-15mum.

Description

Lithium ion secondary battery cathode material zirconium, phosphorus doped lithium cobalt oxide and preparation method thereof

technical field

The invention relates to the field of positive electrode materials for lithium ion secondary batteries, in particular to zirconium and phosphorus-doped lithium cobalt oxide, a positive electrode material for lithium ion secondary batteries, and a preparation method thereof.

Background technique

With the rapid development of modern information technology, portable electronic products such as mobile phones, notebook computers and digital cameras have increasingly strong demand for cost-effective batteries. Due to the advantages of high energy density and no memory effect, lithium-ion secondary batteries have been widely used in the field of portable electrical appliances. However, since most of the current commercial lithium-ion batteries use pure lithium cobalt oxide without doping, the surface structure is unstable, which makes the lithium-ion battery decay quickly, the cycle performance is poor, and the surface structure is prone to damage during the cycle. , causing the internal resistance of the battery to increase. In the case of severe charging and discharging or short circuit, the accumulated heat will increase the temperature of the battery. When it reaches about 200 ° C, the positive electrode material will react with the electrolyte to release oxygen, which will increase the pressure and cause the battery to explode; Thereby affecting the cycle performance and safety of lithium-ion batteries. Therefore, the research and development of lithium-ion secondary batteries with good cycle performance and high safety has been paid more and more attention, and the positive electrode material has become the focus of the industry as a key material for improving battery cycle performance and safety.

Contents of the invention

The main purpose of the present invention is to provide a lithium-ion secondary battery positive electrode material zirconium and phosphorus-doped lithium cobaltate with stable structure and good charge-discharge cycle performance and a preparation method thereof. The positive electrode material has a layered structure, and its preparation method is mainly to form a stable zirconium phosphate doped layer on the surface of lithium cobalt oxide by doping zirconium and phosphorus elements to improve the structural stability of the lithium cobalt oxide material surface and reduce cobalt. The dissolution of lithium oxide in the electrolyte improves the cycle performance and safety performance.

The concrete technical scheme that the present invention solves its technical problem adopts is:

A lithium ion secondary battery positive electrode material zirconium, phosphorus doped lithium cobalt oxide, characterized in that its chemical formula is: LiZr _x Co _(1-xy) P _y O ₂ , wherein x = 0.01 ~ 0.03, y = 0.02 ~ 0.06, with layered structure.

The preparation method of the above-mentioned lithium-ion secondary battery positive electrode material zirconium, phosphorus-doped lithium cobaltate is characterized in that it comprises the following steps:

1). Mix tricobalt tetroxide or cobalt carbonate or cobalt oxalate and lithium carbonate or lithium hydroxide according to the atomic ratio of lithium and cobalt (0.98～1.05): 1.00;

2). Put the mixed raw materials into a roasting furnace, and roast them in an air atmosphere. The roasting temperature is 800-1000°C, and the roasting time is 6-24 hours;

3). Grinding the calcined lithium cobaltate product, the average particle size _D50 of the powder is 6-15um;

4). Put the lithium cobaltate powder into a reaction kettle, add water and stir to form a slurry, the weight of the water is 1 to 3 times the weight of the lithium cobaltate powder. While stirring the slurry, add a zirconium nitrate solution with a concentration of 1 to 2 mol/L and a soluble phosphate solution with a concentration of 1 to 2 mol/L, and the atomic ratio of Zr, P and Co is: Zr/P/Co=x /y/(1-x-y), where x=0.01～0.03, y=0.02～0.06, uniformly coat zirconium and phosphorus on the surface of lithium cobaltate by liquid phase precipitation, the temperature of the reaction kettle is 10～50℃, nitric acid The addition of zirconium and phosphate solutions per hour is 1% to 5% of the volume of the slurry in the reactor, and the linear speed of the outermost side of the stirring paddle is 2 to 5m/s;

5). The slurry obtained in step 4) is spray-dried in a spray dryer, and the powder particle size _D50 after drying is 10-50um;

6). Put the spray-dried powdered material into a roasting furnace, and roast it in an air atmosphere at a roasting temperature of 600-1000° C. for 4-12 hours to obtain zirconium and phosphorus-doped lithium cobaltate. The chemical formula is: LiZr _x Co _(1-xy) P _y O ₂ where x = 0.01 ~ 0.03, y = 0.02 ~ 0.06, with a layered structure;

7). Grinding the zirconium and phosphorus-doped lithium cobaltate obtained after calcination, the average particle size D ₅₀ of the powder is 6-15um.

The soluble phosphate is ammonium phosphate, diammonium hydrogen phosphate or ammonium dihydrogen phosphate.

The beneficial effects of the present invention are: the lithium ion secondary battery positive electrode material provided by the present invention is based on the existing secondary battery positive electrode material pure cobalt oxide lithium, doping with zirconium and phosphorus to form zirconium and phosphorus doped cobalt acid Lithium, the preparation method adopted is to first synthesize lithium cobalt oxide, and then uniformly dope zirconium and phosphorus elements on its surface through liquid phase precipitation and spray drying. Uniformity can ensure that the crystal grains of lithium cobalt oxide are not damaged during the doping process, so as to achieve uniform doping on the entire particle surface; and because the positive electrode material is doped with zirconium and phosphorus elements at the same time, the cobalt oxide A stable zirconium phosphate doped layer is formed on the lithium surface layer to improve the structural stability of the lithium cobaltate material surface and reduce the dissolution of lithium cobaltate in the electrolyte, thereby improving the cycle performance and safety performance of the lithium-ion battery.

Description of drawings

Fig. 1 is the SEM of the cathode material prepared in embodiment 4 under an electron microscope;

Fig. 2 is the phase XRD of the cathode material prepared in Example 4.

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

Detailed ways

Example 1

A lithium ion secondary battery cathode material zirconium, phosphorus doped lithium cobalt oxide, its chemical formula is:

LiZr _x Co _(1-xy) P _y O ₂ , where x=0.02, y=0.04, has a layered structure.

The preparation method of the above-mentioned lithium ion secondary battery cathode material zirconium, phosphorus doped lithium cobalt oxide comprises the following steps:

1). According to the atomic ratio of lithium and cobalt 1.03:1.00, 2000.0 grams of cobalt carbonate and 687.6 grams of lithium hydroxide are mixed uniformly;

2). Put the mixed raw materials into a roasting furnace, and roast them in an air atmosphere. The roasting temperature is 900°C, and the roasting time is 12 hours;

3). Grinding the calcined lithium cobalt oxide, the average particle size _D50 of the powder is 10-12um;

4). Put 1000.0 grams of lithium cobaltate powder into the reaction kettle, add 2000.0 grams of water and stir to form a slurry. While stirring the slurry, add 0.217 L of zirconium nitrate solution with a concentration of 1 mol/L and a concentration of 2 mol through a peristaltic pump /L diammonium hydrogen phosphate solution 0.217L, the atomic ratio of Zr, P, and Co is: Zr/P/Co=0.02/0.04/0.94, uniformly coat zirconium and phosphorus on the surface of lithium cobaltate by liquid phase precipitation , the temperature of the reaction kettle is 40°C, the addition amount of zirconium nitrate and diammonium hydrogen phosphate solution per hour is 50mL/h respectively, and the outermost linear speed of the stirring blade is 3m/s;

5). The slurry obtained in step 4) is spray-dried in a spray dryer, and the powder particle size _D50 after drying is 10-50um;

6). Put the spray-dried powdered material into a roasting furnace and roast it in an air atmosphere at a roasting temperature of 900°C for 8 hours to obtain zirconium and phosphorus-doped lithium cobaltate, whose chemical formula is: LiZr _0.02 Co _0.94 P _0.04 O ₂ , with layered structure;

7). Grinding the zirconium and phosphorus-doped lithium cobalt oxide obtained after roasting to obtain a product with an average particle size _D50 of 10-13um.

Example 2

A lithium ion secondary battery cathode material zirconium, phosphorus doped lithium cobalt oxide, its chemical formula is:

LiZr _x Co _(1-xy) P _y O ₂ where x = 0.01, y = 0.02, has a layered structure.

The preparation method of the above-mentioned lithium ion secondary battery cathode material zirconium, phosphorus doped lithium cobalt oxide comprises the following steps:

1). By lithium, cobalt atomic ratio 1.02:1.00, 1000.0 grams of cobalt tetroxide and 470.1 grams of lithium carbonate are mixed uniformly;

2). Put the mixed raw materials into a roasting furnace and roast in an air atmosphere at a roasting temperature of 800°C and a roasting time of 24 hours;

3). Grinding the calcined lithium cobalt oxide, the average particle size _D50 of the powder is 6-8um;

4). Put 1,000.0 grams of lithium cobaltate powder into the reaction kettle, add 1,000.0 grams of water and stir to form a slurry. While stirring the slurry, add 0.105 L of zirconium nitrate solution with a concentration of 1 mol/L and a concentration of 2 mol through a peristaltic pump /L of ammonium dihydrogen phosphate solution 0.105L, the atomic ratio of Zr, P, and Co is: Zr/P/Co=0.01/0.02/0.97, uniformly coat zirconium and phosphorus on the surface of lithium cobaltate by liquid phase precipitation , the temperature of the reaction kettle is 20°C, the addition amount of zirconium nitrate and ammonium dihydrogen phosphate solution per hour is 20mL/h, and the outermost linear speed of the stirring blade is 2m/s;

5). The slurry obtained in step 4) is spray-dried in a spray dryer, and the powder particle size _D50 after drying is 10-50um;

6). Put the spray-dried powdered material into a roasting furnace and roast it in an air atmosphere. The roasting temperature is 600°C for 12 hours to obtain zirconium and phosphorus doped lithium cobalt oxide. Its chemical formula is: LiZr _0.01 Co _0.97 P _0.02 O ₂ , with layered structure;

7). Grinding the zirconium and phosphorus doped lithium cobaltate obtained after calcination to obtain a product with an average particle size (D ₅₀ ) of 6-8 um.

Example 3

A lithium ion secondary battery cathode material zirconium, phosphorus doped lithium cobalt oxide, its chemical formula is:

LiZr _x Co _(1-xy) PyO ₂ , where x=0.03, y=0.06, has a layered structure.

The preparation method of the above-mentioned lithium ion secondary battery cathode material zirconium, phosphorus doped lithium cobalt oxide comprises the following steps:

1). By lithium, cobalt atomic ratio 0.98:1.00, 1000.0 grams of cobalt tetroxide and 451.6 grams of lithium carbonate are mixed uniformly;

2). Put the mixed raw materials into a roasting furnace, and roast in an air atmosphere, the roasting temperature is 1000°C, and the roasting time is 6 hours;

3). Grinding the calcined lithium cobalt oxide, the average particle size _D50 of the powder is 13-15um;

4). Put 1,000.0 grams of lithium cobaltate powder into the reaction kettle, add 3,000.0 grams of water and stir to form a slurry. While stirring the slurry, add 0.337 L of zirconium nitrate solution with a concentration of 1 mol/L and a concentration of 2 mol through a peristaltic pump /L of ammonium phosphate solution 0.337L, the atomic ratio of Zr, P, and Co is: Zr/P/Co=0.03/0.06/0.91, uniformly coat zirconium and phosphorus on the surface of lithium cobaltate by liquid phase precipitation, and react The temperature of the kettle is 50°C, the addition amount of zirconium nitrate and ammonium phosphate solution per hour is 200mL/h, and the outermost linear speed of the stirring blade is 5m/s;

5). The slurry obtained in step 4) is spray-dried in a spray dryer, and the powder particle size _D50 after drying is 10-50um;

6). Put the spray-dried powdered material into a roasting furnace and roast it in an air atmosphere. The roasting temperature is 1000°C for 4 hours to obtain zirconium and phosphorus doped lithium cobaltate. Its chemical formula is: LiZr _0.03 Co _0.91 P _0.06 O ₂ , with layered structure;

7). Grinding the zirconium and phosphorus doped lithium cobaltate obtained after calcination to obtain a product with an average particle size (D ₅₀ ) of 13-15 um.

Example 4

A zirconium and phosphorus doped lithium cobaltate lithium ion secondary battery cathode material, the chemical formula is: LiZr _x Co _(1-xy) P _y O ₂ , where x=0.01, y=0.03, and has a layered structure.

The preparation method of the above-mentioned lithium ion secondary battery cathode material zirconium, phosphorus doped lithium cobalt oxide comprises the following steps:

1). By lithium, cobalt atomic ratio 1.05:1.00, 1000.0 grams of cobalt tetroxide and 483.9 grams of lithium carbonate are mixed uniformly;

2). Put the mixed raw materials into a roasting furnace, and roast them in an air atmosphere. The roasting temperature is 900°C, and the roasting time is 12 hours;

3). Grinding the calcined lithium cobalt oxide, the average particle size _D50 of the powder is 10-12um;

4). Put 1000.0 grams of lithium cobaltate powder into the reaction kettle, add 3000.0 grams of water and stir to form a slurry. While stirring the slurry, add 0.105 L of zirconium nitrate solution with a concentration of 1 mol/L and a concentration of 2 mol through a peristaltic pump /L of ammonium phosphate solution 0.341L, the atomic ratio of Zr, P, and Co is: Zr/P/Co=0.01/0.03/0.96, uniformly coat zirconium and phosphorus on the surface of lithium cobaltate by liquid phase precipitation, and react The temperature of the kettle is 30°C, the addition amount of zirconium nitrate and ammonium phosphate solution per hour is 100mL/h, and the outermost linear speed of the stirring blade is 3m/s;

5). The slurry obtained in step 4) is spray-dried in a spray dryer, and the powder particle size _D50 after drying is 10-50um;

6). Put the spray-dried powdered material into a roasting furnace and roast it in an air atmosphere at a roasting temperature of 950°C for 8 hours to obtain zirconium and phosphorus-doped lithium cobaltate, whose chemical formula is: LiZr _0.01 Co _0.96 P _0.03 O ₂ , with layered structure;

7). Grinding the zirconium and phosphorus-doped lithium cobalt oxide obtained after roasting to obtain a product with an average particle size _D50 of 10-13um.

Figure 1 is the SEM of the positive electrode material prepared in this example under an electron microscope. It can be seen from the figure that a layer of fine powder adheres to the surface of lithium cobaltate particles after doping, and is rich in zirconium and phosphorus elements after energy spectrum analysis.

Figure 2 is the phase XRD of the positive electrode material prepared in this example. It can be seen from the figure that the phase is pure lithium cobaltate phase, and the layered structure of the main body of lithium cobaltate is not damaged after doping.

Example 5

A lithium ion secondary battery cathode material zirconium, phosphorus doped lithium cobalt oxide, its chemical formula is:

LiZr _x Co _(1-xy) P _y O ₂ , where x=0.02, y=0.06, has a layered structure.

The preparation method of the above-mentioned lithium ion secondary battery cathode material zirconium, phosphorus doped lithium cobalt oxide comprises the following steps:

1). According to the atomic ratio of lithium and cobalt of 1.05:1.00, 2000.0 grams of cobalt oxalate and 482.9 grams of lithium hydroxide are mixed evenly;

2). Put the mixed raw materials into a roasting furnace and roast in an air atmosphere at a roasting temperature of 800°C and a roasting time of 22 hours;

3). Grinding the calcined lithium cobalt oxide, the average particle size _D50 of the powder is 10-12um;

4). Put 1000.0 grams of lithium cobaltate powder into the reaction kettle, add 2000.0 grams of water and stir to form a slurry. While stirring the slurry, add 0.221 L of zirconium nitrate solution with a concentration of 1 mol/L and a concentration of 2 mol through a peristaltic pump /L of ammonium phosphate solution 0.663L, the atomic ratio of Zr, P, and Co is: Zr/P/Co=0.02/0.06/0.92, uniformly coat zirconium and phosphorus on the surface of lithium cobaltate by liquid phase precipitation, and react The temperature of the kettle is 45°C, the amount of zirconium nitrate and ammonium phosphate solution added per hour is 80mL/h, and the outermost linear speed of the stirring blade is 3m/s;

5). The slurry obtained in step 4) is spray-dried in a spray dryer, and the powder particle size _D50 after drying is 10-50um;

6). Put the spray-dried powdered material into a roasting furnace and roast it in an air atmosphere at a roasting temperature of 900°C for 8 hours to obtain zirconium and phosphorus-doped lithium cobaltate, whose chemical formula is: LiZr _0.02 Co _0.92 P _0.06 O ₂ , with layered structure;

7). Grinding the zirconium and phosphorus-doped lithium cobalt oxide obtained after roasting to obtain a product with an average particle size _D50 of 10-13um.

comparative example

1). By lithium, cobalt atomic ratio is 1.02:1.00 1000 grams of tricobalt tetroxide and 469.8 grams of lithium carbonate are mixed uniformly;

2). Put the mixed raw materials into a roasting furnace and roast them in an air atmosphere at a roasting temperature of 900°C for 12 hours to obtain lithium cobaltate;

3). Grinding the lithium cobaltate obtained after roasting to obtain a product with an average particle size _D50 of 10-13um.

The raw materials used in the above embodiments of the present invention, such as tricobalt tetroxide, cobalt carbonate, cobalt oxalate, lithium carbonate, zirconium nitrate, lithium hydroxide, diammonium hydrogen phosphate, ammonium phosphate and ammonium dihydrogen phosphate are commercially available conventional chemical raw materials, The equipment used is also commercially available conventional equipment.

Table 1 Cycle performance test table lists the electrical performance test results of lithium cobaltate lithium ion secondary battery anode material prepared by the above-mentioned examples and comparative examples. Lithium-ion button battery positive electrode material composition: 90% positive electrode active material + 5% conductive carbon black + 5% PVDF; battery negative pole is pure lithium; electrolyte is 1:1 (EC+DEC) of 1molLiPF ₆ ; diaphragm is Cellgard2400 Microporous membrane. The voltage range is 3.0-4.3V, and the charge and discharge rate is 0.2C. The charging and discharging equipment used is the blue electric charging and discharging instrument.

It can be seen from the data in Table 1 that although the initial discharge capacity of ordinary lithium cobalt oxide is slightly higher, the discharge capacity after 20 cycles is already lower than that of doped lithium cobalt oxide, which shows that zirconium and phosphorus doped lithium cobalt oxide are in the process of cycling. The stability of the middle structure is better, and the zirconium phosphate on the surface after doping plays a role in stabilizing the structure.

Table 1 Cycle performance test table

Claims (2)

1. A preparation method for a lithium ion secondary battery positive electrode material, the chemical formula of the lithium ion secondary battery positive electrode material is: LiZr _x Co _(1-xy) P _y O ₂ , wherein x=0.01～0.03, y =0.02～0.06, has layered structure; It is characterized in that comprising the following steps: 1) Mix tricobalt tetroxide or cobalt carbonate or cobalt oxalate and lithium carbonate or lithium hydroxide according to the atomic ratio of lithium and cobalt (0.98～1.05): 1.00; 2) Put the mixed raw materials into a roasting furnace, and roast in an air atmosphere, the roasting temperature is 800-1000°C, and the roasting time is 6-24 hours; 3) Pulverizing the calcined lithium cobalt oxide, the average particle size _D50 of the powder is 6-15um; 4) Put the lithium cobaltate powder into the reaction kettle, add water and stir to form a slurry, the weight of the water is 1 to 3 times the weight of the lithium cobaltate powder, and add nitric acid with a concentration of 1 to 2mol/L while stirring the slurry Zirconium solution and concentration are the soluble phosphate solution of 1～2mol/L, Zr, P, the atomic ratio of Co is: Zr/P/Co=x/y/(1-x-y), wherein x=0.01～0.03, y=0.02～0.06, uniformly coat zirconium and phosphorus elements on the surface of lithium cobaltate by liquid phase precipitation, the temperature of the reactor is 10～50℃, and the addition amount of zirconium nitrate and phosphate solution per hour is respectively the material in the reactor 1% to 5% of the slurry volume, the outermost linear velocity of the stirring paddle is 2 to 5m/s; 5) The slurry obtained in step 4) is spray-dried in a spray dryer, and the powder particle size _D50 after drying is 10-50um; 6) Put the spray-dried powdered material into a roasting furnace, and roast it in an air atmosphere at a roasting temperature of 600-1000°C for 4-12 hours to obtain zirconium and phosphorus-doped lithium cobaltate, which has the chemical formula It is: LiZr _x Co _(1-xy) P _y O ₂ , where x=0.01～0.03, y=0.02～0.06, having a layered structure; 7) The zirconium and phosphorus-doped lithium cobaltate obtained after calcination are pulverized, and the average particle size D ₅₀ of the powder is 6-15 um. 2. The preparation method of zirconium and phosphorous-doped lithium cobaltate, the anode material of lithium ion secondary battery according to claim 1, characterized in that said soluble phosphate is ammonium phosphate, diammonium hydrogen phosphate or diammonium phosphate hydrogen ammonia.

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