Cathode Material for a Lithium Ion Battery and Preparation Method and Application Thereof

Abstract

The cathode material of the invention has a porous structure, wherein the pore volume of mesoporous with pore diameter of 2-20 nm accounts for 90% or more of the total pore volume. As compared with conventional lithium-ion battery cathode material, the lithium-ion battery cathode material of the present invention contains mainly mesopores, and the pore size of mesopores is mostly in the range of 2-20 nm.

Claims

1. A lithium-ion battery cathode material, wherein the cathode material has a porous structure, wherein pore volume of all mesopores with a pore size of 2-20 nm accounts for 90% or more of total volume of all pores.

2. The lithium-ion battery cathode material of claim 1, wherein pore volume of pores with a pore size of 3-20 nm accounts for 60% or more of total pore volume of all mesopores.

3. The lithium-ion battery cathode material of claim 1, wherein the cathode material has a specific surface area of 0.25-1.5 m.sup.2/g.

4. The lithium-ion battery cathode material of claim 1, characterized in that particle size of D.sub.V50 particles of the cathode material is 2.00-6.00 μm.

5. The lithium-ion battery cathode material of claim 1, characterized in that total free lithium content of the cathode material is less than 2000 ppm.

6. The lithium-ion battery cathode material of claim 1, characterized in that the cathode material contains lithium element, nickel element and manganese element and the content of the nickel element in the cathode material is greater than that of the manganese element.

7. The lithium-ion battery cathode material of claim 1, characterized in that the cathode material contains elements as defined in a chemical formula 1; the chemical formula 1 is: Li.sub.1+aNi.sub.xMn.sub.yCo.sub.zA.sub.mO.sub.2, where 0≤a≤0.25, 0.5<x≤0.97, 0<y≤0.42, 0≤z≤0.09, 0≤m≤0.03, wherein A is selected from any one or two or more elements of Mn, Co, Al, Zr, Y, Rb, Cs, W, Ce, Mo, Ba, Ti, Mg, Ta, Nb, Ca, V, Sc, Sr and B, or from phosphorus-containing compounds containing at least one element of Ti, Al, Mg, Zr, La and Li.

8. The lithium-ion battery cathode material of claim 1, characterized in that the lithium-ion battery cathode material is prepared by the preparation method comprises steps of mixing raw materials, then sintering at least twice and crushing at least twice.

9. The lithium-ion battery cathode material of claim 8, characterized in that the first sintering temperature is 750-980° C., and the constant temperature time is 8-40 hours; the second sintering temperature is 650-920° C., and the constant temperature time is 5-20 hours.

10. The lithium-ion battery cathode material of claim 9, characterized in that the sintering atmosphere is air, oxygen or mixed gas of air and oxygen.

11. The lithium-ion battery cathode material of claim 8, characterized in that the preparation method of the lithium-ion battery cathode material further comprises the following steps: (1) mixing crushed products with a metal A source, and (2) sintering and crushing a mixture in step (1).

12. The lithium-ion battery cathode material of claim 11, characterized in that the sintering temperature in step (2) is 300-780° C., the constant temperature time is 3-14 hours.

13. The lithium-ion battery cathode material of claim 12, characterized in that the sintering atmosphere is air, oxygen or mixed gas of air and oxygen.

14. The lithium-ion battery cathode material of claim 8, characterized in that the Li source is lithium-containing oxide, lithium-containing fluoride or lithium-containing salt.

15. The lithium-ion battery cathode material of claim 14, characterized in that the Li source is selected from one or more than two of lithium hydroxide anhydrous, lithium hydroxide monohydrate, lithium carbonate, lithium nitrate, lithium acetate and lithium fluoride.

16. A positive electrode of a lithium-ion battery comprising a current collector and a cathode material loaded on the current collector, wherein the cathode material is the lithium-ion battery cathode material of claim 1.

17. A lithium-ion battery comprising a positive electrode, a negative electrode and a lithium salt-containing electrolyte, wherein the positive electrode is the positive electrode of claim 16.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 is a curve chart of the pore size distribution of a lithium-ion battery cathode material prepared in one example 1.

[0035] FIG. 2 is a curve chart of the pore size distribution of a lithium-ion battery cathode material prepared in one example 2.

[0036] FIG. 3 is a curve chart of the pore size distribution of a lithium-ion battery cathode material prepared in one example 6.

[0037] FIG. 4 is a curve chart of the pore size distribution of a lithium-ion battery cathode material prepared in one example 7.

DETAILED DESCRIPTION OF THE INVENTION

[0038] For the purpose of achieving the objectives, technical solution and technical effect of examples of the present invention and complete description will be made to the technical solutions of the examples of the present invention. The following described examples are merely a part of examples of the present invention and not all the examples. Based on the examples of the present invention, all other examples obtained by a person of ordinary skill in the art without involving any inventive effort all fall within the scope of the present invention.

[0039] In the description of the present invention, the pore size distribution refers to the change of proportion of pore volume of different pore sizes in the total pore volume with the pore size.

[0040] In the description of the present invention, mesopores refer to pores with a pore size of 2-50 nm, that is, pores with a pore size of 2 nm or more to 50 nm or less, micropores are pores with a pore size of less than 2 nm, and macropores are pores with a pore size of more than 50 nm.

[0041] In order to better understand above technical solution, the technical solution of the present invention is further detailed.

[0042] The present invention provides a lithium-ion battery cathode material which has a porous structure, wherein

[0043] a pore volume of mesopores with a pore size of 2-20 nm accounts for 90% or more of a pore volume of total pores.

[0044] In a preferred embodiment of the present invention, a pore volume of pores with a pore size of 3-20 nm accounts for 60% or more of a total mesopore volume of the mesopores.

[0045] In a preferred embodiment of the present invention, a pore volume of pores with a pore size of 5-19 nm accounts for 40% or more of a total pore volume of the mesopores.

[0046] In another preferred embodiment of the present invention, the specific surface area of the cathode material is 0.25-1.5 m.sup.2/g, preferably, the D.sub.V50 particle size of the cathode material is 2.00-6.00 μm, and further preferably, the total free lithium content of the cathode material is less than 2000 ppm.

[0047] In another preferred embodiment of the present invention, the cathode material contains lithium, nickel and manganese, and the content of the nickel in the cathode material is greater than that of the manganese.

[0048] In another preferred embodiment of the present invention, the cathode material contains elements shown in a chemical formula 1;

[0049] the chemical formula 1 is Li.sub.1+aNi.sub.xMn.sub.yCo.sub.zA.sub.mO.sub.2, where 0≤a≤0.25, 0.5<x≤0.97, 0<y≤0.42, 0≤z≤0.09, 0≤m≤0.03,

[0050] and A is selected from any one or two or more elements of Mn, Co, Al, Zr, Y, Rb, Cs, W, Ce, Mo, Ba, Ti, Mg, Ta, Nb, Ca, V, Sc, Sr and B, or from phosphorus-containing compounds containing at least one element of Ti, Al, Mg, Zr, La and Li.

[0051] The present invention further provides a preparation method of the lithium-ion battery cathode material. The preparation method comprises steps of mixing raw materials, then sintering at least twice and crushing at least twice.

[0052] The first sintering temperature is 750-980° C., and the sintering time is 8-40 hours; the second sintering temperature is 650-920° C., and the sintering time is 5-20 hours; and preferably, the sintering atmosphere is air, oxygen or mixed gas of air and oxygen.

[0053] In a preferred embodiment of the present invention, the preparation method of the above-mentioned lithium-ion battery cathode material further comprises the following steps:

[0054] (1) mixing crushed products with a metal A source;

[0055] (2) sintering and crushing a mixture in step (1).

[0056] The sintering temperature in step (2) is 300-780° C., and the sintering time is 3-14 hours; and further preferably, the sintering atmosphere is air, oxygen or mixed gas of air and oxygen.

[0057] In a preferred embodiment of the present invention, according to the above-mentioned preparation method, the Li source is lithium-containing oxide, lithium-containing fluoride or lithium-containing salt, and preferably, the Li source is selected from one or more than two of lithium hydroxide anhydrous, lithium hydroxide monohydrate, lithium carbonate, lithium nitrate, lithium acetate and lithium fluoride.

[0058] The present invention also provides a lithium-ion battery cathode material prepared by the above-mentioned preparation method.

[0059] In another preferred embodiment of the present invention, the lithium-ion battery cathode material of the present invention, which is prepared by the preparation method comprising steps of mixing raw materials, then sintering at least twice and crushing at least twice.

[0060] Preferably, the first sintering temperature is 750-980° C., and the sintering time is 8-40 hours; the second sintering temperature is 650-920° C., and the sintering time is 5-20 hours.

[0061] Preferably, the preparation method of the above-mentioned lithium-ion battery cathode material further comprises the following steps:

[0062] (1) mixing crushed products with a metal A source;

[0063] (2) sintering and crushing a mixture in step (1).

[0064] Preferably, the sintering temperature in step (2) is 300-780° C., and the sintering time is 3-14 hours.

[0065] The present invention further provides a lithium-ion battery positive electrode which comprises a current collector and a cathode material loaded on the current collector.

[0066] The cathode material is the above-mentioned lithium-ion battery cathode material.

[0067] The present invention further provides a lithium-ion battery, which is characterized by comprising a positive electrode, a negative electrode and a lithium salt-containing electrolyte. The positive electrode is the above-mentioned lithium-ion battery positive electrode.

[0068] The lithium-ion battery of the present invention further comprises a diaphragm and an aluminum-plastic film. Specifically, the electrode comprises a positive electrode and a negative electrode. The positive electrode is made of a positive electrode current collector, a positive active material coated on the positive electrode current collector, a binder, a conductive improver and the like; and the positive active material is the above-mentioned lithium-ion cathode material. The negative electrode is made of a current collector, a negative active material coated on the current collector, a binder, a conductive improver and the like. The diaphragm is a PP/PE film commonly used in this industry, and is used for separating the positive electrode from the negative electrode; and the aluminum-plastic film is a container of the positive electrode, the negative electrode, the diaphragm and the electrolyte.

[0069] The binder includes polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, poly(1,1-difluoroethylene), polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy resin, nylon, the like, and combinations thereof, and is used for improving the adhesion characteristics between positive active material particles and between the positive active material particles and the current collector.

[0070] The conductive improver includes one or more than two of a carbon-based material, a metal-based material and a conductive polymer. The carbon-based material is one or more than two of natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack or carbon fibers, the metal-based material is metal powder or metal fibers of copper, nickel, aluminum or silver, and the conductive polymer is a polyphenylene derivative.

[0071] The present invention further provides an application of the above-mentioned lithium-ion battery cathode material, or the above-mentioned lithium-ion battery positive electrode, or the above-mentioned lithium-ion battery in the fields of digital batteries, power batteries or energy storage batteries.

[0072] The technical effects of the present invention are further illustrated by the following specific examples.

[0073] Information of reagents and equipment used in the following examples is shown in Table 1 and Table 2.

TABLE-US-00001 TABLE 1 Information of reagents used in Examples Name of reagents Grade Model Manufacturer nanometer ceramic grade — Xuancheng Jingrui New Materials zirconium oxide (Anhui) Co., Ltd. nanometer titanium ceramic grade — Xuancheng Jingrui New Materials dioxide (Anhui) Co., Ltd. tungsten oxide ceramic grade — Xuancheng Jingrui New Materials (Anhui) Co., Ltd. nanometer ceramic grade — Xuancheng Jingrui New Materials magnesium oxide (Anhui) Co., Ltd. nanometer ceramic grade — Xuancheng Jingrui New Materials aluminum oxide (Anhui) Co., Ltd. rubidium carbonate ceramic grade — Xuancheng Jingrui New Materials (Anhui) Co., Ltd. nanometer niobium ceramic grade — Xuancheng Jingrui New Materials oxide (Anhui) Co., Ltd. strontium titanate ceramic grade — Xuancheng Jingrui New Materials (Anhui) Co., Ltd. barium titanate ceramic grade — Xuancheng Jingrui New Materials (Anhui) Co., Ltd. nanometer cerium ceramic grade — Xuancheng Jcingrui New Materials oxide Co., Ltd. of Anhui boric oxide reagent grade — Nanjing Chemical Reagent Plant nanometer yttrium ceramic grade — Xuancheng Jingrui New Materials oxide (Anhui) Co., Ltd. aluminum nitrate battery grade 99.50% Dalian First Organic Chemical Co., nonahydrate Ltd. tetrabutyl titanate reagent grade 99.80% Nanjing Chemical Reagent Plant zirconium n- reagent grade 99.80% Nanjing Chemical Reagent Plant Butoxide cerium carbonate reagent grade  96.0% Zibo Ruibokang Rare Earth Material Co., Ltd. lithium hydroxide battery grade 99.5 wt % Yahua Lithium Technology (Sichuan) anhydrous Co., Ltd. lithium hydroxide battery grade 56.0 wt % Jiangxi Ganfeng Lithium Group Co., monohydrate Ltd. lithium carbonate battery grade 56.0 wt % Jiangxi Ganfeng Lithium Group Co., Ltd. lithium nitrate battery grade 99.5 wt % Shanghai Oujin Industrial Co., Ltd. lithium acetate battery grade 99.5 wt % Sichuan State Lithium Materials Co., Ltd. high-purity oxgen industrial Purity: 99.9% Guizhou Yagang Gas Co., Ltd. grade conductive carbon battery grade Super P Li TIMCAL black N- battery grade Content: 99.5% Nanjing Jinlong Chemical Co., Ltd. methylpyrrolidone polyvinylidene battery grade Solef 6020 SOLVAY Chemical Co., Ltd. Of fluoride America aluminum foil battery grade Thickness: Aluminum Company of America  16 μm electronic adhesive electronic Green width: Minnesota Mining and Manufacturing tape grade  10 mm Company lithium piece electronic Diameter Φ: Shanghai Shimyu Metal Materials grade 20 mm; purity: Co., Ltd. greater than or equal to 99.9% electrolyte electronic LIB301, Shenzhen Capchem Technology Co., grade propylene Ltd. carbonate (PC): ethylene carbonate (EC): diethyl carbonate (DEC) = 1:1:1 (volume ratio), lithium salt LiPF6 concentration: 1 mol/L diaphragm — PP/PE/PP Celgard Company of America three-layer material, Celgard M825, thickness:  16 μm aluminum-plastic industrial total thickness: Dai Nippon Printing Co., Ltd film grade 160 μm

TABLE-US-00002 TABLE 2 Information of equipment used in Examples Name of equipment Model Manufacturer laser particle size analyzer MSU-2000 Malvern Panalytical Ltd micromeritics automatic surface area TriStarII3020 Micromeritics Instruments and porosity analyzer Corporation inductively coupled plasma optical iCAP-7400 Thermo Electron Corporation emission spectrometer High constant temperature formation LIP-3AHB06 Zhejiang HangKe Technology system Incorporated Company High-efficiency vacuum drying oven KP-BAK-03E- Kerui Mechnical and Electrical 02 Limited Airflow pulverizer MX-50 YiXing Juneng Ultra Fine Grinding Equipment Co., Ltd. Roller kiln 36m Huayou New Energy Kiln Equipment Co., Ltd.

Example 1

[0074] Material mixing: select a 200 L plow mixer, start stirring, add 46.11 kg of lithium hydroxide monohydrate, 0.256 kg of nanometer titanium dioxide and 100.0 kg of nickel manganese hydroxide precursor Ni.sub.0.68Mn.sub.0.32(OH).sub.2 (battery grade, purchased from Guangdong Jiana Energy Technology Co., Ltd.), and stir for 2 hours for later use;

[0075] first sintering: adopt a 36 m roller kiln, set the sintering temperature at 930° C., introduce the mixed gas of air and oxygen (the oxygen content is 60%, the gas flow rate is 8 L/min), load mixed materials into the roller kiln for first sintering, keep the temperature constant for 20 hours, cool the materials to a room temperature, and pulverize the materials with an air pulverizer to obtain primary sintered semi-finished products;

[0076] secondary sintering: adopt a 36 m roller kiln, set the sintering temperature at 800° C., introduce the mixed gas of air and oxygen (the oxygen content is 60%, the gas flow rate is 8 L/min), load the obtained primary sintered semi-finished products into the 36 m roller kiln for secondary sintering, keep the temperature constant for 8 hours, cool the materials to a room temperature, pulverize the materials with an air pulverizer, and then demagnetize to obtain secondary sintered semi-finished products;

[0077] secondary mixing: put the secondary sintered semi-finished products into a fusion machine, start stirring, and then add 0.248 kg of nanometer titanium dioxide, and mix for 30 minutes; and

[0078] third sintering: adopt a 36 m roller kiln, set the sintering temperature at 750° C., introduce the mixed gas of air and oxygen (the oxygen content is 60%, the gas flow rate is 8 L/min), load the secondary mixed materials into the 36 m roller kiln for third sintering, keep the temperature constant for 6 hours, cool the materials to a room temperature, pulverize the materials with an air pulverizer, demagnetize, and sieve to obtain the cathode material.

[0079] The chemical formula of the above cathode material obtained after digestion with dilute hydrochloric acid and ICP detection is LiNi.sub.0.68Mn.sub.0.32Ti.sub.0.0063O.sub.2.

Example 2

[0080] Material mixing: select a 200 L plow mixer, start stirring, add 45.87 kg of lithium hydroxide monohydrate and 100 kg of nickel manganese cobalt hydroxide precursor Ni.sub.0.65Co.sub.0.1Mn.sub.0.25(OH).sub.2 (battery grade, purchased from Guizhou Zhongwei Zhengyuan New Material Co., Ltd.), and stir for 2 hours for later use;

[0081] first sintering: adopt a 36 m roller kiln, set the sintering temperature at 940° C., introduce the mixed gas of air and oxygen (the oxygen content is 55%, the gas flow rate is 6 L/min), load mixed materials into the roller kiln for first sintering, keep the temperature constant for 13 hours, cool the materials to a room temperature, and pulverize the materials with an air pulverizer to obtain primary sintered semi-finished products;

[0082] secondary sintering: adopt a 36 m roller kiln, set the sintering temperature at 850° C., introduce the mixed gas of air and oxygen (the oxygen content is 55%, the gas flow rate is 6 L/min), load the obtained primary sintered semi-finished products into the 36 m roller kiln for secondary sintering, keep the temperature constant for 14 hours, cool the materials to a room temperature, pulverize the materials with an air pulverizer, and then demagnetize to obtain secondary sintered semi-finished products;

[0083] secondary mixing: put the secondary sintered semi-finished products into a fusion machine, start stirring, and then add 4.43 kg of strontium carbonate into the 36 m roller kiln, and mix for 30 minutes; and

[0084] third sintering: adopt a 36 m roller kiln, set the sintering temperature at 780° C., introduce the mixed gas of air and oxygen (the oxygen content is 55%, the gas flow rate is 6 L/min), load the secondary mixed materials into the 36 m roller kiln for third sintering, keep the temperature constant for 7 hours, cool the materials to a room temperature, pulverize the materials with an air pulverizer, demagnetize, and sieve to obtain the cathode material.

[0085] The chemical formula of the above cathode material obtained after digestion with dilute hydrochloric acid and ICP detection is LiNi.sub.0.65Co.sub.0.1Mn.sub.0.25Sr.sub.0.03O.sub.2.

Example 3

[0086] Material mixing: select a 200 L plow mixer, start stirring, add 29.8 kg of lithium hydroxide, anhydrous, 0.377 kg of aluminum oxide and 100 kg of nickel manganese hydroxide precursor Ni.sub.0.97Mn.sub.0.03(OH).sub.2 (battery grade, purchased from Guangdong Jiana Energy Technology Co., Ltd.), and stir for 2 hours for later use;

[0087] first sintering: adopt a 36 m roller kiln, set the sintering temperature at 750° C., introduce oxygen (the gas flow rate is 10 L/min), load mixed materials into the roller kiln for first sintering, keep the temperature constant for 40 hours, cool the materials to a room temperature, and pulverize the materials with an air pulverizer to obtain primary sintered semi-finished products;

[0088] secondary sintering: adopt a 36 m roller kiln, set the sintering temperature at 650° C., introduce oxygen (the gas flow rate is 10 L/min), load the obtained primary sintered semi-finished products into the 36 m roller kiln for secondary sintering, keep the temperature constant for 5 hours, cool the materials to a room temperature, pulverize the materials with an air pulverizer, and then demagnetize to obtain secondary sintered semi-finished products;

[0089] secondary mixing: put the secondary sintered semi-finished products into a mixing tank, start stirring, add 200 kg of deionized water and 0.614 kg of zirconium n-butoxide solution, mix for 50 minutes, and filter to obtain filter cakes; and

[0090] third sintering: adopt a 36 m roller kiln, set the sintering temperature at 550° C., introduce oxygen (the oxygen flow rate is 10 L/min), load the secondary mixed filter cakes into the 36 m roller kiln for third sintering, keep the temperature constant for 4 hours, cool the materials to a room temperature, pulverize the materials with an air pulverizer, demagnetize, and sieve to obtain the cathode material.

[0091] The chemical formula of the above cathode material obtained after digestion with dilute hydrochloric acid and ICP detection is Li.sub.1.15Ni.sub.0.97Mn.sub.0.03Al.sub.0.0037Zr.sub.0.0016O.sub.2.

Example 4

[0092] Material mixing: select a 200 L plow mixer, start stirring, add 51.97 kg of lithium hydroxide monohydrate, 0.244 kg of boric oxide and 100 kg of nickel manganese cobalt hydroxide precursor Ni.sub.0.79Co.sub.0.07Mn.sub.0.15(OH).sub.2 (battery grade, purchased from Jingmen Genlinmei New Material Co., Ltd.), and stir for 2 hours for later use;

[0093] first sintering: adopt a 36 m roller kiln, set the sintering temperature at 880° C., introduce oxygen (the gas flow rate is 8 L/min), load mixed materials into the roller kiln for first sintering, keep the temperature constant for 25 hours, cool the materials to a room temperature, and pulverize the materials with an air pulverizer to obtain primary sintered semi-finished products;

[0094] secondary sintering: adopt a 36 m roller kiln, set the sintering temperature at 800° C., introduce oxygen (the gas flow rate is 8 L/min), load the obtained primary sintered semi-finished products into the 36 m roller kiln for secondary sintering, keep the temperature constant for 6 hours, cool the materials to a room temperature, pulverize the materials with an air pulverizer, and then demagnetize to obtain secondary sintered semi-finished products;

[0095] secondary mixing: put the secondary sintered semi-finished products into a fusion machine, start stirring, add 0.104 kg of boric oxide, and mix for 40 minutes; and

[0096] third sintering: adopt a 36 m roller kiln, set the sintering temperature at 500° C., introduce oxygen (the gas flow rate is 8 L/min), load the secondary mixed materials into the 36 m roller kiln for third sintering, keep the temperature constant for 8 hours, cool the materials to a room temperature, pulverize the materials with an air pulverizer, demagnetize, and sieve to obtain the cathode material Li.sub.1.14Ni.sub.0.79Co.sub.0.07Mn.sub.0.15B.sub.0.01O.sub.2.

[0097] The chemical formula of the above cathode material obtained after digestion with dilute hydrochloric acid and ICP detection is Li.sub.1.14Ni.sub.0.77Co.sub.0.07Mn.sub.0.15B.sub.0.01O.sub.2.

Example 5

[0098] Material mixing: select a 200 L plow mixer, start stirring, add 48.46 kg of lithium hydroxide monohydrate and 100 kg of nickel manganese cobalt hydroxide precursor Ni.sub.0.79Co.sub.0.02Mn.sub.0.19(OH).sub.2 (battery grade, purchased from Guangdong Jiana Energy Technology Co., Ltd.), and stir for 2 hours for later use;

[0099] first sintering: adopt a 36 m roller kiln, set the sintering temperature at 860° C., introduce oxygen (the gas flow rate is 7 L/min), load mixed materials into the roller kiln for first sintering, keep the temperature constant for 25 hours, cool the materials to a room temperature, and pulverize the materials with an air pulverizer to obtain primary sintered semi-finished products;

[0100] secondary sintering: adopt a 36 m roller kiln, set the sintering temperature at 780° C., introduce oxygen (the gas flow rate is 7 L/min), load the obtained primary sintered semi-finished products into the 36 m roller kiln for secondary sintering, keep the temperature constant for 7 hours, cool the materials to a room temperature, pulverize the materials with an air pulverizer, and then demagnetize to obtain secondary sintered semi-finished products;

[0101] secondary mixing: put the secondary sintered semi-finished products into a mixing tank, start stirring, add 80 kg of deionized water, stir for 30 minutes, then add a solution containing phosphorus and a solution containing aluminum simultaneously (weigh 0.23 kg of aluminum sulfate and dissolve the aluminum sulfate in 2 kg of deionized water, and then weigh 0.165 kg of ammonium dihydrogen phosphate and dissolve ammonium dihydrogen phosphate in 5 kg of deionized water), mix for 40 minutes, and filter to obtain filter cakes; and

[0102] third sintering: adopt a 36 m roller kiln, set the sintering temperature at 300° C., introduce air (the air flow rate is 15 L/min), load the secondary mixed filter cakes into the 36 m roller kiln for third sintering, keep the temperature constant for 14 hours, cool the materials to a room temperature, pulverize the materials with an air pulverizer, demagnetize, and sieve to obtain the cathode material.

[0103] The chemical formula of the above cathode material obtained after digestion with dilute hydrochloric acid and ICP detection is Li.sub.1.06Ni.sub.0.79Co.sub.0.02Mn.sub.0.19Al.sub.0.0013P.sub.0.0013O.sub.2.

Example 6

[0104] Material mixing: select a 200 L plow mixer, start stirring, add 43.24 kg of lithium carbonate and 100 kg of nickel manganese cobalt hydroxide precursor Ni.sub.0.62Co.sub.0.03Mn.sub.0.35(OH).sub.2 (battery grade, purchased from Guangdong Jiana Energy Technology Co., Ltd.), and stir for 2 hours for later use;

[0105] first sintering: adopt a 36 m roller kiln, set the sintering temperature at 970° C., introduce air (the air flow rate is 15 L/min), load mixed materials into the roller kiln for first sintering, keep the temperature constant for 8 hours, cool the materials to a room temperature, and pulverize the materials with an air pulverizer to obtain primary sintered semi-finished products; and

[0106] secondary sintering: adopt a 36 m roller kiln, set the sintering temperature at 910° C., introduce air (the air flow rate is 15 L/min), load the obtained primary sintered semi-finished products into the 36 m roller kiln for secondary sintering, keep the temperature constant for 20 hours, cool the materials to a room temperature, pulverize the materials with an air pulverizer, and then demagnetize to obtain the cathode material.

[0107] The chemical formula of the above cathode material obtained after digestion with dilute hydrochloric acid and ICP detection is Li.sub.1.08Ni.sub.0.62Co.sub.0.03Mn.sub.0.35O.sub.2.

Example 7

[0108] Material mixing: select a 200 L plow mixer, start stirring, add 43.24 kg of lithium carbonate and 100 kg of nickel manganese cobalt hydroxide precursor Ni.sub.0.62Co.sub.0.03Mn.sub.0.35(OH).sub.2 (battery grade, purchased from Guangdong Jiana Energy Technology Co., Ltd.), and stir for 2 hours for later use; and

[0109] first sintering: adopt a 36 m roller kiln, set the sintering temperature at 970° C., introduce air (the air flow rate is 15 L/min), load mixed materials into the roller kiln for first sintering, keep the temperature constant for 8 hours, cool the materials to a room temperature, and sieve to obtain the cathode material.

[0110] The chemical formula of the above cathode material obtained after digestion with dilute hydrochloric acid and ICP detection is Li.sub.1.08Ni.sub.0.62Co.sub.0.03Mn.sub.0.35O.sub.2.

Example 8

[0111] Material mixing: select a 200 L plow mixer, start stirring, add 46.96 kg of lithium hydroxide monohydrate, 0.256 kg of nanometer titanium dioxide and 100.0 kg of nickel manganese hydroxide precursor Ni.sub.0.4Mn.sub.0.6(OH).sub.2 (battery grade, purchased from Guangdong Jiana Energy Technology Co., Ltd.), and stir for 2 hours for later use;

[0112] first sintering: adopt a 36 m roller kiln, set the sintering temperature at 930° C., introduce the mixed gas of air and oxygen (the oxygen content is 60%, the gas flow rate is 8 L/min), load mixed materials into the roller kiln for first sintering, keep the temperature constant for 20 hours, cool the materials to a room temperature, and pulverize the materials with an air pulverizer to obtain primary sintered semi-finished products;

[0113] secondary sintering: adopt a 36 m roller kiln, set the sintering temperature at 800° C., introduce the mixed gas of air and oxygen (the oxygen content is 60%, the gas flow rate is 8 L/min), load the obtained primary sintered semi-finished products into the 36 m roller kiln for secondary sintering, keep the temperature constant for 8 hours, cool the materials to a room temperature, pulverize the materials with an air pulverizer, and then demagnetize to obtain secondary sintered semi-finished products;

[0114] secondary mixing: put the secondary sintered semi-finished products into a fusion machine, start stirring, and then add 0.248 kg of nanometer titanium dioxide, and mix for 30 minutes; and

[0115] third sintering: adopt a 36 m roller kiln, set the sintering temperature at 750° C., introduce the mixed gas of air and oxygen (the oxygen content is 60%, the gas flow rate is 8 L/min), load the secondary mixed materials into the 36 m roller kiln for third sintering, keep the temperature constant for 6 hours, cool the materials to a room temperature, pulverize the materials with an air pulverizer, demagnetize, and sieve to obtain the cathode material.

[0116] The chemical formula of the above cathode material obtained after digestion with dilute hydrochloric acid and ICP detection is LiNi.sub.0.4Mn.sub.0.6Ti.sub.0.0063O.sub.2.

[0117] Experiment 1

[0118] The pore size distribution curve, specific surface area, particle size and total free lithium content of Examples 1-8 are measured according to the following method.

[0119] (1) Determination Method of Pore Size Distribution Curve

[0120] A desorption side isotherm is measured by a Micromeritics automatic surface area and porosity analyzer (TriStarII3020), and then the pore size distribution curve with pore diameters as abscissas and pore volume percentages (percentage of the pore volume of mesopores with different pore sizes in the pore volume of total mesopores) as ordinates is obtained by using the desorption side isotherm and calculating with a BJH method. As shown in FIGS. 1-4, the test results of proportion of the mesopores with the pore sizes of 2-20 nm (proportion of the pore volume of the mesopores with the pore sizes of 2-20 in the pore volume of total pores), proportion of the pores with the pore sizes of 3-20 nm (proportion of the pore volume of the pores with the pore sizes of 3-20 in the pore volume of total mesopores), and proportion of the pores with the pore sizes of 5-19 nm (proportion of the pore volume of the pores with the pore sizes of 5-19 in the pore volume of total mesopores) are shown in Table 3.

[0121] (2) Determination Method of Specific Surface Area

[0122] The specific surface area of the present invention is determined by referring to a gravimetric method in GB/T 19587-2004 gas adsorption using the BET Method, and is determined by the Micromeritics automatic surface area and porosity analyzer (TriStarII3020). The test results are shown in Table 3.

[0123] (3) Determination Method of Particle Size

[0124] The particle size of the present invention is measured by referring to a GB/T19077-2016 particle size analysis and laser diffraction method and using a Malvern, Master Size 2000 laser particle size analyzer. The test results are shown in Table 3.

[0125] (4) Determination Method of Total Free Lithium Content

[0126] Accurately weigh 30 g±0.01 g of sample, put the sample into a 250 ml conical flask, put in a magnetic stirrer, and add 100 ml of deionized water; put the conical flask on the magnetic stirrer, turn on the stirrer, and stir for 30 min; filter a mixed solution by shaped filter paper and a funnel; transfer 50 ml of filtrate with a 50 ml pipette, put in a 100 ml beaker, and put in magneton; put the beaker on the magnetic stirrer, and add 2 drops of phenolphthalein indicator; titrate with 0.05 mol/L of hydrochloric acid standard titration solution until the color of the solution changes from red to colorless, and record the volume V.sub.1 (end point 1) of 0.05 mol/L of hydrochloric acid standard titration solution; add 2 drops of methyl red indicator, and the indicator color changes from colorless to yellow; titrate with 0.05 mol/L of hydrochloric acid standard titration solution until the color of the solution changes from yellow to orange; put and heat the beaker on a heating furnace until the solution boils (the color of the solution changes from orange to yellow); take down the beaker, and cool to a room temperature; and then place the beaker on the magnetic stirrer, titrate with 0.05 mol/L hydrochloric acid standard titration solution until the color of the solution changes from yellow to red, and record the volume V.sub.2 (end point 2) of 0.05 mol/L of hydrochloric acid standard titration solution. The total free lithium content is calculated according to the following formula.

[0127] The test results are shown in Table 3.

Total free lithium content=V.sub.2×0.05×6.94×2×100%/(m×1000)

[0128] Total free lithium content—the unit is weight percentage (%);

[0129] m—sample weight, g;

[0130] V.sub.2—second titration end point, ml;

[0131] 6.94—atomic weight of lithium

TABLE-US-00003 TABLE 3 Test results of performance parameters of cathode materials prepared in Examples 1-8 Percentage of Percentage of Percentage of pores with pores with pores with Specific Total free particle particle particle surface lithium Particle sizes of sizes of sizes of area, content size, 2-20 nm 3-20 nm 5-19 nm m.sup.2/g (ppm) μm Example 1 94.92% 83.56% 59.92% 0.67 380 4.3 Example 2 96.48% 87.71% 67.07% 0.53 894 5.2 Example 3 95.93% 80.48%   57% 1.5 850 2.8 Example 4 94.98% 82.43%  57.8% 0.97 1076 3.5 Example 5 94.82% 80.79% 58.86% 1.2 1158 2.8 Example 6 95.69% 86.4% 60.23% 0.48 820 5.6 Example 7 23.8% 9.93%  7.18% 0.32 1328 10.52 Example 8 33.6% 13.31% 10.69% 0.25 280 9.6

[0132] Experiment 2

[0133] Preparation and performance evaluation of lithium-ion battery

[0134] A 454261 soft package battery is prepared according to the following method.

[0135] Preparation of the positive electrode: add the cathode material of the present invention, the conductive carbon black (S.P), and the polyvinylidene fluoride (PVDF) serving as the binder into the N-methylpyrrolidone (NMP) (a weight ratio of the cathode material to the NMP is 2.1:1) according to a weight ratio of 94:3:3, fully mix, stir to form uniform slurry, coat on an aluminum foil current collector, dry and press into a pole piece.

[0136] Preparation of a negative electrode: add the negative electrode artificial graphite, the conductive carbon black (S.P), the carboxymethyl cellulose (CMC) and the binder (SBR) into enough pure water according to a weight ratio of 95:1:1:3, mix, stir to form uniform slurry, coat on the copper foil current collector, dry and press into a pole pieces. The diaphragm is a PP/PE composite film material. Tabs are spot-welded on the pressed positive and negative pole pieces; the pressed positive and negative pole pieces with the tabs are inserted into the diaphragm, are wound on a winding machine, and then are put into a soft package fixture for sealing of tops and sides; afterwards, the pressed positive and negative pole pieces with the tabs are baked in the oven; 9 g of electrolyte is injected in an environment with a relative humidity less than 1.5%; and the electrolyte is a mixed solvent with a mass ratio of EC:DEC:DMC=1:1:1, is 1M of lithium hexafluorophosphate, and is injected, and after formation for 48 hours, vacuumizing and sealing are performed. The model of a battery cell is 454261.

[0137] Battery performances are tested on a Hangke battery tester according to the following method.

[0138] 1) Capacity Test

[0139] Connect the prepared soft package battery with a test rack, and start the test procedure. Setting steps: set the test temperature at 25° C., stand for 4 hours, charge at constant current and constant voltage for 4 hours (such as ⅓C, charge to 4.2V), pause, stand, discharge at a constant current (such as ⅓C, end at 3.0V), and pause; stand for 4 hours, charge at constant current and constant voltage for 4 hours (such as ⅓C, charge to 4.3V), pause, stand, discharge at a constant current (such as 1C, end at 3.0V), and pause; and repeat the previous steps to obtain capacity data under different voltage conditions.

[0140] 2) Cycle Test

[0141] Connect the battery subjected to the above capacity test to the test rack, and start the test procedure. Setting steps: set the test temperature at 45° C., stand for 4 hours, charge at a constant current for 4 hours (such as 1C, charge to 4.2V or 1C, charge to 4.3V), charge at a constant voltage (such as 4.2V for 2 hours or 4.3V for 2 hours), stand for 5 minutes, and discharge at a constant current for 4 hours (such as 1C, end at 3.0V), and stand for 5 minutes; and repeat the previous step of constant-current charging, and carry out the cycle test to obtain the capacity retention rate of different cycles under different voltage conditions.

[0142] 3) Cyclic DCR Growth Test:

[0143] In the step 2) of the cycle test, add a step of constant-current discharge for 30 seconds before the constant-current discharge (the voltage difference within 30 seconds is recorded, and then the DCR is obtained by dividing the voltage by the current), and the rest is unchanged. Repeat the previous step of constant-current charge, and carry out the cycle test to obtain the growth rate of DCR in different cycles (divide a difference value between the DCR after the cycle and the DCR after the first cycle by the DCR after the first cycle).

[0144] Test results are as shown in Table 4.

TABLE-US-00004 TABLE 4 Test results of cycle performance Capacity Capacity DCR growth retention retention rate (4.2 V, Capacity rate (4.2 V, Capacity rate (4.3 V, 45° C., Cathode (4.2 V, 45° C., (4.3 V, 45° C., after 200 material ⅓ C) 200 cycles) ⅓ C) 200 cycles) cycles) BA-S1 Example 1 162.9 99.3% 180.6 95.2% 16.67% BA-S2 Example 2 166.8 98.2% 183.2 92.7% 10.87% BA-S3 Example 3 205.0 99.3% 211.6 55.3% 28.26% BA-S4 Example 4 188.6 94.9% 195.0 92.1% 29.03% BA-S5 Example 5 183.0 94.7% 192.4 91.8% 29.41% BA-S6 Example 6 155.0 93.5% 172.8 90.6% 35.96% BA-S7 Example 7 148.0 90.3% 160 55% (100 cycles) 62.92% BA-S8 Example 8 120.0 / / / / Note: the capacity of Example 8 is measured at 4.4 V, ⅓ C.

[0145] As can be seen from Table 3 and FIGS. 1-4, the lithium-ion battery cathode materials prepared in examples 1-6 mainly contain mesopores, the pore sizes of the mesopores are mainly in the range of 2-20 nm, the pore volume of the mesopores in the range of 2-20 nm accounts for more than 90% of the total pore volume, the pore volume of the pores in the range of 3-20 nm accounts for more than 80% of the total pore volume of the mesopores, and the pore volume of the pores in the range of 5-19 nm accounts for more than 57% of the total pore volume of the mesopores; the lithium-ion battery cathode materials prepared in Examples 1-6 have a relatively large specific surface area of 0.48-1.5 m.sup.2/g and a relatively small particle size of 2.8-5.6 μm; the cathode materials prepared in Examples 7 and 8 mainly contain mesopores and macropores, the mesopores in the range of 2-20 nm are relatively few, and the pore volume of the mesopores in the range of 2-20 nm accounts for less than 40% of the total pore volume; and the lithium-ion battery cathode materials prepared in examples 7 and 8 have a relatively small specific surface area of 0.25-0.32 m.sup.2/g and a relatively large particle size of 9.6-10.52 μm.

[0146] As can be seen from Table 4, compared with the lithium-ion battery cathode material of example 7, the lithium-ion battery cathode materials provided by Examples 1-6 have the advantages that the capacity is increased, the cycle performance improves, obviously improves especially at a high voltage, and the growth rate of cyclic DCR is obviously reduced; in Example 7, as the material has more large pores, the material easily cracks during the cycle, therefore, the cycle performance is relatively poor, the material is not suitable for a high voltage, after 100 cycles at 4.3V, the capacity retention rate is only 55%, and the cyclic DCR increases greatly; compared with the material of Example 1, the material of Example 8 has the advantages that the capacity cannot be developed at a low voltage as the manganese content is higher than the nickel content, the capacity can barely be developed at a high voltage, but the capacity is too low to meet the requirement of energy density.

[0147] To sum up, the lithium-ion battery cathode material provided by the present invention has mesopores, the pore size of which is mainly in the range of 2-20 nm and accounts for more than 90%, and these mesopores provide more shorter paths for lithium ion migration, so that the lithium-ion battery cathode material provided by the present invention has higher capacity; at the same time, during the charge and discharge process of the lithium-ion battery, the cathode material is not easy to crack, and thus, the capacity attenuation of the lithium-ion battery cathode material in the cycle process is prevented.

[0148] The above examples are merely preferred examples of the present invention and are not intended to limit the present invention. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention are intended to be included within the protection scope of the present invention.