CN109888207B

CN109888207B - High-nickel low-free-lithium ion ternary positive electrode material and preparation method and application thereof

Info

Publication number: CN109888207B
Application number: CN201910074681.9A
Authority: CN
Inventors: 赵孝连; 徐健; 杨亮亮; 闵婷婷; 农廷峰
Original assignee: Guizhou Gaodian Technology Co ltd; Gaodian Shenzhen Technology Co ltd
Current assignee: Guizhou Gaodian Technology Co ltd; Gaodian Shenzhen Technology Co ltd
Priority date: 2019-01-25
Filing date: 2019-01-25
Publication date: 2022-05-17
Anticipated expiration: 2039-01-25
Also published as: CN109888207A

Abstract

The invention relates to a lithium ion ternary cathode material with high nickel content and low free lithium content, and a preparation method and application thereof. The chemical formula of the anode material is LiNi_xCo_yMn_(1‑x‑y)M_αO₂The element Mn can be replaced by the element Al, and the replacement proportion is 0-100%, wherein: x is 0.6-0.9, y is 0.01-0.2, and x + y is less than 1; m is a doping element selected from Al, Mg and/or Zr, and alpha is more than or equal to 0 and less than 0.08; the positive electrode material comprises primary particles and secondary particles formed by agglomeration of the primary particles, wherein the mass percentage of the primary particles is 80.0-99.5%, the average length-diameter ratio of the positive electrode material is 1.5-3.0, and the content of free lithium ions in the positive electrode material is lower than 0.16 wt%. The cathode material disclosed by the invention is high in Ni content, low in free lithium content, high in primary particle content and good in safety performance, and can be applied to a high-voltage and long-cycle system. The method for preparing the cathode material omits the traditional precursor precipitation preparation process, is more favorable for stable and uniform dispersion and in-situ synthesis of the doping elements, is economical and feasible, has wide applicability and better application prospect.

Description

High-nickel low-free-lithium ion ternary positive electrode material and preparation method and application thereof

Technical Field

The invention relates to the technical field of lithium ion batteries, mainly relates to the field of lithium ion battery anode materials, and particularly relates to a preparation method and application of a high-nickel ternary anode material mainly comprising primary particles.

Background

In recent years, with the rise of smart phones and smart cars, requirements on power energy density and safety of mobile equipment are higher and higher. Currently, common positive electrode materials of lithium ion batteries mainly include lithium cobaltate, lithium manganate, lithium nickel manganese cobalt and lithium iron phosphate. Among them, lithium cobaltate is improved from lithium nickelate material with poor early safety, and is mainly used in small mobile terminals in 3C field because of limited cobalt storage capacity in spite of high weight energy density. Lithium manganate and lithium iron phosphate materials have low energy density and tend to be gradually replaced by high nickel materials with low cobalt content, such as nickel cobalt lithium manganate. The nickel-cobalt binary and nickel-cobalt-manganese ternary materials are usually layered rock salt structure materials, wherein Ni, Co and Mn are adjacent elements in the same period, the content of nickel and manganese elements can be high or low, and manganese can be completely replaced by aluminum elements, so that the nickel-cobalt binary and nickel-cobalt-manganese ternary materials can be mixed in any proportion to form a solid solution, the layered structure is kept unchanged, the nickel-cobalt binary and nickel-manganese ternary materials have good structural complementarity, the advantages of lithium cobaltate, lithium nickelate and lithium manganate are better combined, the respective defects are made up, and the nickel-cobalt binary and nickel-manganese ternary materials have the characteristics of high specific capacity, lower cost, stable cycle performance, better safety performance and the like, and are considered as ideal choices of next-generation lithium ion battery anode materials. The nickel-cobalt-manganese ternary material with the molar content of nickel in the structural formula of more than 0.5 is generally called a high-nickel ternary material.

Research shows that the requirements of sintering and processing conditions are more strict along with the increase of nickel content when the high-nickel ternary material is prepared. Generally, the higher the nickel content is, the more important the moisture and atmosphere control of the production environment is, and the main influence is that the dislocation mixed arrangement of nickel/lithium elements occurs in the sintering process, and the nickel reacts with the moisture absorbed by the material powder in the storage process of the high-nickel ternary material to cause Ni²⁺To Ni³⁺Thereby causing deterioration of the structure of the material and further affecting the capacity exertion and the first efficiency of the positive electrode material. In addition, the higher the nickel content of the material is, the larger the conductivity change of the high-nickel ternary material body in the charge-discharge process is, so that the lithium removal/insertion of the material is difficult, and the material body has stress in the long-term circulation processAnd secondary particles in the material are pulverized or broken finally, and the generated new interface has catalytic activity on electrolyte, so that the attenuation of the electrochemical performance of the lithium ion battery is further aggravated.

The preparation of the cathode material is a high-temperature physical diffusion process, lithium oxide existing on the surface of a precursor of the cathode material is gradually migrated and diffused to a macroscopic scale precursor phase in a plasma state through high temperature and atmosphere, and a lithium-embeddable material with a certain crystal structure is generated in an oxygen atmosphere. Since the lithium source on the surface layer is also a particle, the uneven distribution of the contact surface of the lithium source and the precursor during the diffusion process may form local unevenness of the lithium source. When the particle size of the precursor material is too large, the conditions of difficult diffusion and inconsistent crystal particle growth also exist, and the performance of the lithium ion battery is weakened.

At present, the gas generation problem of the high-nickel ternary material in the use process cannot be solved, and the high-nickel ternary material can only be used for cylindrical steel shell batteries such as 18650 type and 21700 type cylindrical batteries, so that the application of the high-nickel ternary material in vacuum-sealed flexible packages and square batteries is limited. Therefore, the problems of distribution and diffusion of lithium source, dopant and the like on the surface of the precursor material need to be solved. Corresponding methods and applications have been proposed in a number of publications and patent documents.

Patent CN201410482634.5 discloses a preparation method of spherical lithium nickel cobalt manganese oxide. Performing solid-liquid separation on the precursor material, washing with pure water, and drying at 45 ℃/6h to obtain spherical nickel-cobalt-manganese mixed carbonate; and then carrying out preheating treatment (6 ℃/min is increased to 480 ℃/8h) on the obtained mixed carbonate to obtain an oxide, and taking metered lithium hydroxide and pure water according to a mass ratio of 1: 1.8, mixing, and ball-milling in a ball mill for 2 hours to prepare lithium salt slurry and the precursor oxide subjected to preheating treatment according to the molar ratio of Li: (Ni + Co + Mn) ═ 1.3: 2 stirring and mixing for 40 min; and then carrying out heat treatment on the obtained product (heating from room temperature to 480 ℃ at the heating rate of 3 ℃/min, preserving the heat for 4h, then heating to 850 ℃/15h at the heating rate of 3 ℃/min), and naturally cooling to obtain the spherical nickel cobalt lithium manganate material.

Patent CN201310693296.5 discloses a method for preparing nickel cobalt lithium manganate as a high voltage lithium battery cathode material. Nickel cobalt manganese hydroxide and lithium salt according to Li: (Ni + Co + Mn) ═ 1.05 to 1.10: 1, adding the mixture into a ball milling tank for ball milling for 2-6h to uniformly mix the mixture; putting the mixed product into a crucible and putting the crucible into a sintering furnace, heating to 900-; according to Mg: x, Zr: 3-x, wherein x is more than or equal to 1 and less than or equal to 2, adding magnesium acetate and zirconium acetate into deionized water to prepare a mixed solution with 2-5mol/L of total metal ions, and mixing according to the molar ratio of (Mg + Zr): adding the (Ni + Co + Mn) into a water phase system of single crystal or quasi-single crystal nickel cobalt lithium manganate according to the molar ratio of 0.002-0.006, stirring for 0.5-2.0h, dynamically drying at the temperature of 100-.

Patents CN201610253176.7 and CN201610253178.6 disclose a preparation method of a layered lithium nickel cobalt manganese oxide positive electrode material. Solid Mn (NO) is added according to stoichiometric ratio₃)₂、CoCO₃、Ni(NO₃)₂·6H₂O and Li₂CO₃The mixture is put into the inner cavity of the rotary drum; the rotating roller throws out the mixture from the inner cavity under the action of centrifugal force and then throws the mixture into the inner cavity of the roller again to obtain a uniformly mixed mixture; adding a dispersing agent into the uniformly mixed mixture for ball milling; then placing the slurry subjected to ball milling in a drying oven for drying to obtain a precursor; pre-burning the precursor in a resistance furnace; and (3) grinding after pre-burning, and roasting the ground material in a rotary roasting furnace/resistance furnace to obtain the nickel cobalt lithium manganate material of the invention.

Patent CN201710652580.6 discloses a single crystal ternary cathode material, a preparation method thereof and a lithium ion battery, comprising the following steps: preparing a mixture solution from a lithium source, a nickel source, a cobalt source, a manganese source and a complexing agent; performing complex crystallization treatment on the mixture solution to obtain a precursor of the single crystal ternary cathode material; sintering the precursor; wherein the sintering treatment process comprises the following steps of firstly heating to 300-500 ℃ at a speed of 1-5 ℃/min, preserving heat for 2-10h, then heating to 600-1000 ℃ at a speed of 1-20 ℃/min, and preserving heat for 10-20 h. The grain diameter of the single crystal ternary anode material is 1-9 mu m

Patent CN201110314584.6 discloses a preparation method of a ternary cathode material of a lithium ion battery, wherein the general formula of the ternary cathode material is Li_mNi_1-x-y-zMn_xCo_yM_zO₂M is more than or equal to 0.98 and less than or equal to 1.10, x is more than 0 and less than or equal to 0.3, y is more than 0 and less than or equal to 0.5, z is more than or equal to 0 and less than or equal to 0.1, M represents one or more elements in Mg, Ti, Zr and Al, a nickel-cobalt-manganese three-element intermediate, a lithium source and an M source are weighed according to the molar ratio of the elements shown in the general formula of the ternary cathode material, water-soluble carbon chain organic additives with the mass being 2-5 percent of the total mass of the nickel-cobalt-manganese three-element intermediate, the lithium source and the M source are added, ball milling and mixing are carried out for 1-4h, grinding is carried out in a colloid mill for 1-8h, then vacuum drying is carried out at the temperature of 80-120 ℃, and tabletting and forming is carried out; then placing the formed material into a ceramic bowl, heating to 850-; dissolving soluble salt of metal element M 'in solvent, and then crushing the semi-finished product of the anode material according to the ratio of M': (Ni + Co + Mn + M) ═ 0.05: 1, adjusting the pH value to be between 9 and 11, stirring for 1 to 2 hours at the temperature of between 20 and 60 ℃, filtering, washing, drying, and then carrying out heat preservation for 1 to 10 hours at the temperature of between 400 and 700 ℃ to obtain the coated single crystal ternary cathode material.

Patent CN201210351698.2 discloses a method for preparing a spherical lithium nickel cobalt composite oxide cathode material, which comprises the following steps: (1) lithium source, nickel source, cobalt source and doping element M source are mixed according to the proportion of element Li: ni: co: m ═ x: (1-y-z): y: z, adding a grinding medium solvent, carrying out ball milling mixing treatment, carrying out spray granulation on the obtained slurry to obtain lithium nickel cobalt precursor powder, placing the obtained lithium nickel cobalt precursor powder in a calcining furnace for sintering, wherein the sintering atmosphere is oxygen atmosphere, the sintering temperature is controlled at 700 DEG and 900 ℃/5-30h, and finally carrying out crushing and grading to obtain the lithium nickel cobalt precursor powder with the chemical composition conforming to the general formula Li_xNi_(1-y-z)Co_yM_zO₂The spherical lithium nickel cobalt composite oxide cathode material is characterized in that: m is selected from at least one of Al, Mg and Mn, x is more than or equal to 1.0 and less than or equal to 1.1, y is more than or equal to 0.1 and less than or equal to 0.4, and z is more than or equal to 0 and less than or equal to 0.3.

Patent applicationCN201610443127.X discloses a doped micron-grade single-crystal ternary cathode material with chemical formula LiNi_xCo_yMn_zM_1-x-y-zO_2-nF_n(ii) a Wherein, 0<x<1，0<y<1， 0<z<1，0<n<0.5, M is more than one of Al, Mg or Ti. Particle size (D) of doped micron-sized single crystal ternary cathode material_v50) 1 to 8 μm. Adding the ternary precursor into a ball milling tank, and carrying out ball milling and crushing for 1-6 h at the speed of 100-600 r/min; then adding the lithium salt, the compound containing M and the fluoride into a ball milling tank, and ball milling and mixing for 1-6 hours at the speed of 100-600 r/min to obtain a uniformly mixed mixture; and then placing the mixture in an oxygen atmosphere, heating to 800-1200 ℃/10-20 h at a heating rate of 0.1-5 ℃/min, and then cooling to normal temperature at a cooling rate of 0.1-5 ℃/min to obtain the doped micron-grade single crystal ternary cathode material.

The methods for preparing the nickel-cobalt-manganese ternary cathode material and the single crystal ternary cathode material in the patent publications are complex.

Disclosure of Invention

The technical problem solved by the invention is as follows: firstly, the structural stability and safety of the conventional high-nickel ternary cathode material with a secondary particle structure need to be improved in the using process, and the prepared lithium ion battery has the defects of poor safety, narrow application range and the like due to high content of free lithium and non-uniform crystal growth caused by non-uniform diffusion of lithium, so that a simple and feasible process method for developing a high-nickel ternary cathode material mainly based on a primary small particle structure is urgently needed. Secondly, when the high-nickel ternary cathode material is prepared by the existing method, the process for preparing the precursor causes serious environmental pollution, and the investment for treatment and recovery is large.

The technical scheme disclosed by the existing document is different from the in-situ generation method in the invention, the precursor preparation is difficult, the pollution is serious, the subsequent process can not meet the requirement of the preparation process of the high-nickel ternary primary particles on the atmosphere, when the oxidation atmosphere can not meet the requirement, for example, enough oxygen is not introduced, the valence of nickel is in a non-structure valence divalent state, divalent nickel ions are easy to be mixed with a lithium ion layer, and the reduction of active lithium and the instability of the structure are caused.

In order to solve the technical problems, the basic element (Ni, Co and Mn) salts are physically mixed and then added with a small amount of acid substances for in-situ reaction to further strengthen the mixing uniformity, so that the mixed materials are mixed more uniformly; and the high-nickel ternary cathode material with excellent electrochemical performance is obtained by presintering and roasting, so that the process of precursor synthesis is saved, and the performance of preparing the cathode material is further improved.

After analyzing the preparation process of the nickel-cobalt cathode material, the inventor finds that the high-nickel ternary cathode material has insufficient element diffusion due to low synthesis temperature, and further causes poor structural stability; in addition, in a high nickel system, due to the fact that the relative content of nickel is high and the content of Co and Mn elements is correspondingly low, the total element concentration in a prepared solution is low when a precursor is prepared, and therefore the defects that the precursor is difficult to settle and the consumption of deionized water is high exist.

Meanwhile, the raw materials are pretreated at the raw material stage, so that high-nickel ternary cathode material products with different nickel-cobalt element ratios can be conveniently prepared, a multi-element solid solution cathode material can be synchronously generated, and the compatible flexible production of the cathode materials with different element ratios is favorably realized.

The invention also finds that a uniform dopant can be formed by adding the doping modification element in the raw material stage, so that the purpose of improving the electrochemical performance and the safety performance of the prepared lithium ion battery is achieved.

Specifically, aiming at the defects of the prior art, the invention provides the following technical scheme:

1. the chemical formula of the anode material of the lithium ion battery is LiNi_xCo_yMn_(1-x-y)M_αO₂The element Mn can be replaced by the element Al, and the replacement proportion is 0-100%, wherein: x is 0.6-0.9, y is 0.01-0.2, and x + y is less than 1; m is a doping element selected from Al, Mg and/or Zr, and alpha is more than or equal to 0 and less than 0.08; the positive electrode material comprises primary particles and secondary particles formed by agglomeration of the primary particles, wherein the mass percentage of the primary particles is 80.0-99.5%, the average length-diameter ratio of the positive electrode material is 1.5-3.0, and the content of free lithium ions in the positive electrode material is lower than 0.16 wt%.

2. The positive electrode material according to paragraph 1, wherein x is 0.7 to 0.9, and y is 0.01 to 0.2; preferably, x is 0.8 to 0.9 and y is 0.01 to 0.15.

3. The positive electrode material according to paragraph 1 or 2, wherein the mass percentage of the primary particles is 90.0 to 99.5%, preferably, the mass percentage of the primary particles is 92.0 to 99.5%; further preferably, the mass percentage of the primary particles is 95.0-99.5%;

it is further preferred that the average aspect ratio of the positive electrode material is 1.5 to 2.8; it is further preferable that the aspect ratio of the positive electrode material is 1.8 to 2.2;

more preferably, the positive electrode material has an average particle diameter D_v50-7 μm, more preferably 2-7 μm, and still more preferably 3-6.5 μm.

4. The cathode material according to any of paragraphs 1-3, wherein the cathode material contains a free lithium ion content of less than 0.10 wt%, preferably less than 0.06 wt%, further preferably less than 0.05 wt%, further preferably 0.012-0.046 wt%.

5. The cathode material according to any one of paragraphs 1-4, wherein the specific surface area of the cathode material is 0.5-1.2m²Per g, preferably 0.5 to 1m²Per g, more preferably 0.5 to 0.6m²/g。

6. A preparation method of the positive electrode material (including any one of the positive electrode materials) comprises the following steps: mixing a lithium source and a pollution-free precursor, and then performing a sintering process and a crushing process to obtain the lithium-ion battery;

wherein the non-pollution precursor contains Ni_xCo_yMn_(1-x-y)M_αR, salts, oxides and/or hydroxides containing the structural elements nickel, cobalt or manganese, and salts, hydroxides and/or oxides containing the doping elements aluminum, magnesium or zirconium;

the structural formula Ni_xCo_yMn_(1-x-y)M_αIn R:

m is a doping element selected from Al, Mg and/or Zr;

x is 0.6-0.9, y is 0.01-0.2, x + y is less than 1, and alpha is more than or equal to 0 and less than 0.08; preferably, x is 0.7 to 0.9, and y is 0.01 to 0.2; further preferably, x is 0.8 to 0.9, and y is 0.01 to 0.15;

r is organic acid radical ion; preferably, R is selected from the acid ions of formic acid, acetic acid, isooctanoic acid and/or adipic acid, preferably acetate ions.

7. The production method according to paragraph 6, wherein the non-contaminating precursor is an amorphous powder-like precursor; preferably, the precursor particle diameter D is_v500.1 to 5 μm, preferably 0.15 to 3 μm.

8. The production method according to paragraph 6 or 7, wherein the contamination-free precursor is produced by:

according to the molar ratio of nickel: cobalt: manganese ═ (0.6-0.9): (0.01-0.02): (0.2-0.4) mixing carbonate, sulfate, oxide and/or hydroxide containing nickel, cobalt or manganese, preferably carbonate and/or hydroxide to obtain a mixture containing nickel, cobalt and manganese, adding an organic acid and a salt, hydroxide and/or oxide containing doping elements of aluminum, magnesium or zirconium, dispersing the mixture with the mixture, and drying to obtain the pollution-free precursor;

preferably, the organic acid is selected from formic acid, acetic acid, isooctanoic acid, citric acid and/or adipic acid, preferably acetic acid;

more preferably, the amount of the organic acid added is 40 to 500% by mass, still more preferably 40 to 80% by mass, of the active ingredient of the positive electrode material.

9. The production method according to any one of paragraphs 6 to 8, wherein the lithium source and the non-contaminating precursor satisfy a molar ratio of Li: (Ni + Co + Mn) ═ 1.0 to 1.1: 1.

10. the production method of any one of paragraphs 6 to 9, wherein the lithium source is one or more selected from lithium hydroxide monohydrate, lithium oxalate, lithium carbonate, lithium nitrate, lithium acetate, lithium fluoride, lithium chloride, lithium tert-butoxide, or lithium citrate, preferably lithium hydroxide monohydrate or lithium carbonate.

11. The production method according to any one of paragraphs 6 to 10, wherein the apparatus for mixing the lithium source with the non-contaminating precursor is selected from a kneader, a high-speed disperser, and/or a ribbon blender; preferably, the mixing time is from 0.2 to 10 hours, preferably from 0.5 to 4 hours.

12. The method of any of paragraphs 6-11, wherein the sintering step is performed using equipment selected from a vented muffle or a vented roller kiln;

preferably, the gas introduced in the sintering process is oxygen-enriched air; it is further preferred that the oxygen content of the oxygen-enriched air is from 30 to 97% by volume, preferably from 90 to 97% by volume, and it is further preferred that the atmosphere flow rate is from 200Nm to 700Nm³Further preferably 300-³/h；

More preferably, the sintering temperature is 800-980 ℃, and still more preferably, the sintering temperature is 830-890 ℃;

it is further preferred that the sintering time is 2 to 20 hours, and it is further preferred that the sintering time is 4 to 10 hours.

13. The production method according to any one of paragraphs 6 to 12, wherein the pulverization step employs air vortex pulverization, preferably pulverization with an ambient relative humidity of 12% or less, preferably 2% or less.

14. A lithium ion battery anode material is prepared by any one of the preparation methods.

15. A lithium ion battery comprises any one of the positive electrode materials.

16. The lithium ion battery is applied to the field of energy sources, preferably electric vehicles, mobile power supplies and energy storage power stations.

17. A pollution-free precursor, wherein the structural formula of the pollution-free precursor is Ni_xCo_yMn_(1-x-y)M_αR and M are selected from Al, Mg and/or Zr, wherein: x is 0.6-0.9, y is 0.01-0.2, x + y is less than 1, 0 ≦ α is less than 0.08, and R is an organic acid radical ion, preferably, wherein x is 0.7-0.9, and y is 0.01-0.2; further preferably, x is 0.8 to 0.9 and y is 0.01 to 0.15.

18. The non-contaminating precursor of paragraph 17, wherein the non-contaminating precursor is an amorphous powdered precursor; preferably, the precursor particle diameter D_v500.1 to 5 μm, preferably 0.15 to 3 μm.

19. Contamination-free precursor according to any one of claims 17-18, wherein R is selected from the group consisting of acid ions, preferably acetate ions, of formic acid, acetic acid, isooctanoic acid and/or adipic acid.

20. The preparation method of the pollution-free precursor comprises the following steps: according to the molar ratio of nickel: cobalt: manganese ═ (0.6-0.9): (0.01-0.02): (0.2-0.4) mixing carbonate, sulfate, oxide and/or hydroxide containing nickel, cobalt or manganese, preferably carbonate and/or hydroxide to obtain mixture containing nickel, cobalt and manganese, adding organic acid solution to disperse with the mixture, and drying to obtain the pollution-free precursor;

it is further preferred that the solvent in the organic acid solution is selected from water or an alcohol selected from alcohols having no more than 4 carbon atoms, preferably ethanol, propanol and/or isopropanol;

more preferably, the amount of the organic acid solution added is 40 to 500% by mass, still more preferably 40 to 80% by mass, of the active ingredient of the positive electrode material.

21. A production method according to paragraph 20, wherein the temperature of the dispersion is 60 to 90 ℃, preferably 60 to 75 ℃; it is further preferred that the dispersion rate is from 30 to 200rpm, preferably the dispersion time is from 0.5 to 300min, preferably from 0.2 to 240 min.

22. The production method according to any one of paragraphs 20 to 21, wherein the drying step comprises solvent desorption and/or solvent recovery at elevated temperature, and preferably the drying step employs equipment selected from a group consisting of an air blowing box, a jacketed kneader and/or a rotary kiln; it is further preferable that the medium for the heating device in the drying step is nitrogen gas, water vapor or heat transfer oil, it is further preferable that the drying temperature is 60 to 150 ℃, it is preferably 60 to 120 ℃, it is further preferable that the drying time is 2 to 20 hours, it is preferably 4 to 20 hours, and it is further preferable that the protective atmosphere is nitrogen gas in a volume ratio of 99.5% or more.

23. The precursor is applied to the preparation of the cathode material.

The invention has the advantages that:

1. the content of free lithium of the low-nickel product is easy to reduce at present, but the content of free lithium of the high-nickel product is difficult to reduce, even does not reduce and rise reversely, but the positive electrode material of the invention has high Ni content and low free lithium content, thus having better safety performance, and the high-nickel positive electrode material of the invention has high primary particle content, and can be applied to a high-voltage and long-cycle system.

2. The invention adopts the organic acid salt ternary precursor to prepare the anode material, and the process is more environment-friendly.

3. According to the invention, the initial salt raw materials respectively containing Ni, Co and Mn elements and the adulterant are mixed and directly sintered into the anode material for the lithium ion battery, so that the problems of difficult preparation of the hydroxide precursor of the high-nickel ternary anode material, incomplete sintering caused by low sintering temperature of the high-nickel ternary anode material, uneven doping elements and the like are solved, and the structural stability of the high-nickel ternary anode material, the electrochemical performance of the high-nickel ternary anode material and the safety performance of the lithium ion battery are facilitated.

4. The preparation method can arbitrarily adjust the proportion of the initial salt raw materials respectively containing Ni, Co and Mn elements to control the proportion of Ni, Co and Mn in the final ternary cathode material, and avoids the problem that the proportion of Ni, Co and Mn in the prepared final ternary cathode material is also fixed due to the fixed proportion of Ni, Co and Mn in the conventional ternary precursor.

Drawings

FIG. 1 shows a high nickel ternary material (screened with a 325 mesh screen) prepared in example 3 at a magnification of 3000.

FIG. 2 is a high nickel ternary material (325 mesh screen) prepared in comparative example 3 at 3000 times magnification.

FIG. 3 is a high nickel ternary material (325 mesh screen) prepared according to example 5, at 3000 times magnification.

FIG. 4 is a high nickel ternary material (325 mesh screen) prepared in comparative example 1 at 3000 times magnification.

Fig. 5 shows the precursor prepared in example 3, at 3000 x magnification.

FIG. 6 shows a commercial precursor used in comparative example 3, at 1000-fold magnification.

FIG. 7 is a 1C/6V overcharge curve for the lithium ion battery prepared in comparative example 1.

FIG. 8 is a 1C/6V overcharge curve for the lithium ion battery prepared in example 5.

Detailed Description

In view of the problems that the structure of the high-nickel ternary cathode material for the lithium ion battery is incomplete due to low sintering temperature, so that the prepared lithium ion battery has poor electrochemical performance and safety performance and the like, the invention provides the method for preparing the high-nickel ternary cathode material with a more complete structure. The preparation method has simple process and flexible material adjustment and conversion of the production line, simultaneously reduces the preparation process of the precursor precipitation of the anode material, and can combine the doping processes together, thereby preparing the material with good uniformity, complete crystal structure and low content of free lithium, being beneficial to improving the electrochemical performance of the lithium battery and expanding the commercial application of the lithium battery.

The anode material of the invention has high content of primary particles, mainly applies the 'lithium fusion' effect (namely lithium is a substance for reducing the melting point at high temperature), and is formed by sintering and fusing primary particle precursors with smaller structures into large primary particles. The term "primary particles" used in the present invention refers to particles that are not agglomerated or are deeply agglomerated by a small number of smaller particles, and the term "secondary particles" refers to particle aggregates that are agglomerated or combined by a large number (for example, more than 20) of primary particles, and the primary particles in the secondary particles have distinct boundaries as an agglomerate structure as can be seen from scanning electron microscope images.

In a preferred embodiment, the invention provides a method for preparing a high-nickel ternary cathode material, which comprises the steps of adding element salt, oxide or hydroxide, doping element salt and an acidic solution in a material mixing stage, namely, dissolving/reacting, immersing and diffusing the doping element into a synthesis raw material body, improving the dispersion performance of the doping element and the body material, and synchronously synthesizing the high-nickel ternary cathode material in a post sintering process at one time.

Wherein, the above element salt, oxide or hydroxide refers to the carbonate, sulfate, oxide and hydroxide of the structural elements such as cobalt, nickel, aluminum, manganese and the like for preparing the anode material. Typically cobalt carbonate, cobalt sulfate, nickel carbonate, manganese sulfate, etc.

The acidic solution is a solution prepared from an organic acid and a solvent, wherein the organic acid can be at least one of formic acid, acetic acid, adipic acid, isooctanoic acid and citric acid (preferably acetic acid), and can be prepared into a solution with a certain concentration with deionized water, absolute ethyl alcohol or isopropanol and the like.

Preferably, the addition amount of the acidic solution is 40-500 wt% based on the content of the effective substances; preferably 40-80 wt%.

Preferably, in the doping process, the target dopant is one or more of oxides, salts, or oxygen oxides with certain particle sizes, such as aluminum, magnesium, and zirconium.

Preferably, in the above process for preparing the cathode material, the lithium source is one or more of lithium hydroxide, lithium oxalate, lithium carbonate, lithium nitrate, lithium acetate, lithium fluoride, lithium chloride, lithium tert-butoxide, lithium citrate, etc., and the purity is industrial grade or battery grade.

Preferably, in the high-nickel-doped ternary cathode material, the cathode material is a layered cathode material with a structural formula containing nickel and cobalt as structural elements, the nickel content is greater than or equal to 0.6 by mole fraction, or the nickel content is greater than 50% by mass, and the manganese element can be partially or completely replaced by aluminum element.

The mass content of the nickel in the cathode material can be obtained by ICP detection.

Preferably, the preparation process of the nickel-cobalt cathode material comprises the following steps.

a) And (4) batching. Firstly, weighing and adding element salt, oxide or hydroxide, a lithium source and doping element salt into a dispersing device for mixing, then adding a solvent and an acidic substance into the mixture, stirring and dispersing uniformly, and then drying the slurry uniformly dispersed in the initial step in vacuum or normal pressure to prepare fluffy dry powder.

b) And (5) sintering. Placing the powder prepared in the step a) into a muffle furnace in an oxygen-introduced ceramic bowl, heating to 800-; preferably, the temperature is raised to 600-800 ℃ at a rate of 5-15 ℃/min for 1-4h, and then the above treatment is carried out.

c) And (4) crushing. Crushing the material prepared in the step b) by a crusher, and optionally sintering and crushing for the second time to obtain the material of the invention.

The high-nickel ternary cathode material can be applied to manufacturing lithium ion secondary batteries and can be further applied to mobile power supplies and energy storage power stations.

The following description will explain the positive electrode material of the present invention, its preparation method and application by specific examples.

The reagents and instrument sources used in the following examples are shown in tables 1 and 2.

TABLE 1 information on reagents used in examples of the present invention

Table 2 information on devices used in the examples of the present invention

Example 1

27kg of cobalt carbonate monohydrate (technical grade, purity 99 wt%), 29.0kg of cobalt acetate tetrahydrate (technical grade, purity 99.0 wt%), 115.3kg of nickel acetate hexahydrate (technical grade, purity 99.5%), 17.0kg of manganese sulfate monohydrate, 20.22kg of manganese acetate (technical grade, purity 99.5%) powder, 0.015kg of nano magnesium oxide (ceramic grade, purity 99.5%) and 0.045kg of magnesium carbonate (ceramic grade, purity 99.7%) were weighed and added into a kneader. Then 200.0kg of industrial acetic acid (industrial grade, purity 99.5%, the addition amount is 200% of the active component mass of the theoretically prepared anode material) and 50kg of deionized water are slowly added into a container to prepare about 30% of acetic acid aqueous solution, and then the acetic acid aqueous solution is slowly added into a kneader under the stirring state, and the reaction temperature of the solution is controlled to be 55 +/-5 ℃. The dripping time is 4h, the mixture is aged for 30h under the stirring state after the dripping is finished, and a pipeline demagnetizer is additionally arranged on a pumping pipeline of the plate-and-frame filter press for demagnetizing (the magnetic field intensity is 11000GS) until the impurity content is in a qualified range.

And taking out the filter cake, drying the filter cake by using a vacuum dryer (the temperature is 60 ℃/20h), and sieving the filter cake by using a 325-mesh stainless steel sieve (the diameter of a sieve pore is 45 mu m) to obtain an NCM622 type precursor (undersize product), wherein the magnetic substance content of the precursor is 121 ppb. The NCM622 type precursor is detected by an electron microscope (SEM), the average length-diameter ratio of the precursor is 1.7, most of powder is in a needle-shaped long strip structure, and a small amount of powder is in an amorphous shape.

The NCM622 type precursor was mixed with 43.3kg of battery grade lithium hydroxide monohydrate (battery grade, 99.5 wt%) in a high mixing machine using a 24m vented roller kiln. Setting the temperature of the heating zone to 980 deg.C, introducing oxygen-enriched air (oxygen content volume ratio of 30%, gas input amount of 700 Nm)³And/h) filling the paste material into a ceramic bowl for sintering, wherein the sintering time is 4h, isolating the material from air, cooling to normal temperature, weighing the weight of the material, and counting the loss on ignition (the ratio of the mass of the sintered powder to the mass of the powder before sintering) to be 42.6%. Then crushing by using a vortex crushing machine, and controlling the humidity of the ambient air to be less than or equal to 2% during crushing to obtain the cathode material.

About 200g of the anode material powder sample is classified by a classifying vibrating screen, and the object under the 800-mesh (aperture 15 μm) screen is found to be primary particles by observation of a microscope. Through statistics, the ratio of the weight of the material passing through the 800-mesh sieve to the total weight of the sample is 80.0%, that is, the weight content of the primary particles in the cathode material prepared in this embodiment is as high as 80%. The particle size (D) of the positive electrode material prepared in this example was measured by a laser particle size analyzer_v50) 1.0 μm; the average length-diameter ratio of the particles is 1.5 by observation and statistics of an electron microscope image, so that the morphology and the structure of the prepared cathode material are similar to those of the prepared precursor, and the length-diameter ratios of the anode material and the precursor are not greatly changed. According to the detection method in example 6, the total free lithium content of the cathode material prepared in this example was 0.1502%. The specific surface area of the cathode material prepared in the example is 1.2m detected by a specific surface area meter²(ii) in terms of/g. The results of the quantitative analysis of the elements of the cathode material by ICP are shown in Table 3, and calculatedThe structural formula of the positive electrode material is as follows: li_0.97Ni_0.6Co_0.2Mn_0.2Mg_0.001O₂。

Table 3 elemental characterization results for positive electrode materials described in example 1

Element(s)	Li	Co	Ni	Mn	Al	Ca	Mg
								Mass ratio of	6.75	11.79	35.21	11.00	0.0198	0.0020	0.0024
Atomic weight	6.94	58.93	58.69	54.94	26.98	40.00	24.00
								Number of moles	0.968	0.20	0.60	0.20	0.0007	0.00005	0.001
Element(s)	Na	P	S	Ti	Y	Zn	Zr
								Mass ratio of	0.0037	0.0047	0.0547	0.0398	0.0210	0.0000	0.0023
Atomic weight	23.00	30.97	32.00	40.00	88.91	65.41	91.22
								Number of moles	0.00016	0.00015	0.00171	0.0001	0.0002	0.00000	0.00003

Example 2

19.45kg of cobalt carbonate (technical grade, purity 99 wt%), 199.6kg of nickel sulfate hexahydrate (technical grade, purity 99.0 wt%), 18.8kg of manganese carbonate powder (technical grade, purity 99.0 wt%) were weighed into a kneader, 0.033kg of zirconium oxide (ceramic grade, purity 99.5 wt%) was slowly added 500.0kg of industrial adipic acid (technical grade, purity 99.5 wt%, added amount of 500% of the mass of active ingredient of the theoretically prepared cathode material), and the reaction temperature of the solution was controlled at 55 ℃. + -. 5 ℃. The dropping time is 4h, 0.92kg of zirconium nitrate pentahydrate (industrial grade, 95 wt%) powder and 0.33kg of nano-zirconia (ceramic grade, purity 99.5 wt%) powder are added after the addition is finished and aged for 30h under the stirring state, the mixture is pumped into a high-speed centrifuge by a diaphragm pump for centrifugal separation, and a pipeline demagnetizer is additionally arranged on a pumping pipeline to demagnetize (the magnetic field intensity is 11000GS) until the impurity content is in a qualified range.

And taking out the filter cake, drying by using a vacuum dryer (the temperature is 60 ℃/20h), and sieving by using a 325-mesh stainless steel screen to obtain the NCM71515 type precursor, wherein the magnetic substance content of the precursor is 49 ppb. When the NCM71515 type precursor is detected by an electron microscope (SEM), the length-diameter ratio is 2.6, the precursor has a hammer-like structure, and the precursor may be a crystal after the product is dried and is in an amorphous shape in a small amount.

The NCM71515 type precursor described above was mixed with 42.0kg of technical grade lithium carbonate (battery grade, 99.8 wt%) in a high speed mixer using a 24m vented roller kiln. Setting the temperature of the heating zone to 980 deg.C, introducing oxygen-enriched air (oxygen content volume ratio is 90%, gas input is 200 Nm)³And/h) filling the paste material into a ceramic bowl for sintering, wherein the sintering time is 2h, isolating the material from air, cooling to normal temperature, weighing the weight of the material, and counting the loss on ignition (the ratio of the mass of sintering powder to the mass of powder before sintering) to be 44.6%. Then crushing by a vortex crusher, and controlling the humidity of the ambient air to be less than or equal to 2% during crushing to obtain the cathode material.

The particle size (D) of the cathode material prepared in this example was measured_v50) 5.7 μm, wherein the weight ratio of the primary particles was 99.5%, the average aspect ratio of the particles was 2.8, the total free lithium content was 0.0202%, and the specific surface area was 0.67m²(ii) in terms of/g. The ICP is used for carrying out quantitative analysis on elements of the anode material, and then the structural formula of the anode material is obtained through calculation: li_1.04Ni_0.70Co_0.15Mn_0.15Zr_0.05O₂。

Example 3

30.88kg of cobalt sulfate heptahydrate (technical grade, purity 98 wt%), 104.6kg of nickel carbonate (technical grade, purity 99.0 wt%) and 16.7kg of manganese sulfate monohydrate (technical grade, purity 99.5 wt%) were weighed out and added into a kneader. Then 80.0kg of industrial isooctanoic acid (industrial grade, purity 99.5%, the addition amount is 80% of the active component mass of the theoretically prepared anode material) and 70kg of deionized water are slowly added into a container to prepare about 83% of acetic acid aqueous solution, and then the acetic acid aqueous solution is slowly added into a kneader under the stirring state, and the reaction temperature of the solution is controlled at 55 +/-5 ℃. The dripping time is 4h, after the dripping is finished, 0.09kg of nano magnesia (ceramic grade, purity 99.5 wt%) powder and 1.05kg of nano zirconia (ceramic grade, purity 99.5 wt%) are added, the mixture is aged for 30h under the stirring state, the mixture is pumped into a high-speed centrifuge by a diaphragm pump for centrifugal separation, and a pipeline demagnetizer is additionally arranged on a pumping pipeline for demagnetization (magnetic field intensity: 9000GS) until the impurity content is in a qualified range.

And taking out the centrifugal solid, drying by using a vacuum drier (the temperature is 60 ℃/20h), and sieving by using a 325-mesh stainless steel sieve to obtain an NCM811 type precursor, wherein the magnetic substance content of the precursor is 45 ppb. Through the observation of a scanning electron microscope, as can be seen from fig. 5, the precursor prepared by the method is an NCM811 type precursor detected by an electron microscope SEM, the average length-diameter ratio is 1.5, and the powder is in a needle-like or sheet-like or amorphous structure.

The NCM811 type precursor was mixed with 56.8kg of battery grade lithium acetate (battery grade, 99.5 wt%) in a high speed mixer using a 24m vented roller kiln. Setting temperature of the heating zone as 890 deg.C, and introducing oxygen-enriched air (oxygen content volume ratio of 95%, gas input amount of 300 Nm)³H) loading the paste material into a ceramic bowl for primary sintering for 2h, isolating the material from air, cooling to normal temperature to obtain a semi-finished product of the lithium nickel cobalt manganese oxide cathode material, further loading the semi-finished product into the bowl for sintering, setting the temperature of an elevated temperature zone to be 830 ℃, and introducing oxygen-enriched air (the volume ratio of oxygen content is 95%, and the gas input is 350 Nm)³The sintering time is 15 h; and (3) cooling after sintering, weighing the weight of the materials in and out, counting the loss on ignition rate (the ratio of the mass of the sintered powder to the mass of the powder before sintering) twice to be 45.3 percent in total, crushing by using a vortex flow crusher, introducing protective nitrogen (the moisture is less than or equal to 6ppm) during crushing, and controlling the humidity of ambient air to be less than or equal to 2 percent to obtain the cathode material.

The particle size (D) of the material is determined_v50) 3.5 μm, wherein the weight ratio of primary particles is 96.5%, the average aspect ratio of the particles is 1.8, the total free lithium content is 0.0551%, and the specific surface area is 0.55m²(ii) in terms of/g. The ICP is used for carrying out quantitative analysis on elements of the anode material, and then the structural formula is calculated: li_1.03Ni_0.81Co_0.1Mn_0.09Zr_0.008O₂。

Example 4

15.88kg of cobalt sulfate heptahydrate (industrial grade, purity 98 wt%), 260.96kg of nickel sulfate hexahydrate (industrial grade, purity 99.0 wt%), 6.7kg of manganese carbonate (industrial grade, purity 99.0 wt%) powder were weighed into a kneader, and 40.0kg of industrial formic acid (industrial grade, purity 99.5%, addition amount thereof is 40% of the mass of the active ingredient of the theoretically produced positive electrode material) was slowly added while controlling the reaction temperature of the solution at 55 ℃. + -. 5 ℃. The dripping time is 4h, 1.27kg of nano magnesium hydroxide (ceramic grade, purity 99.6 wt%) powder is added after the dripping is finished and is aged for 30h under the stirring state, then the mixture is pumped into a centrifugal machine by a diaphragm pump for centrifugal separation, and a pipeline demagnetizer is additionally arranged on a pumping pipeline for demagnetizing (magnetic field intensity: 10000GS) until the impurity content is in a qualified range.

And taking out the centrifugal solid, drying by using a vacuum drier (the temperature is 60 ℃/20h), and sieving by using a 325-mesh stainless steel sieve to obtain an NCM955 type precursor, wherein the magnetic substance content of the precursor is 83 ppb. When the precursor of NCM955 type was examined by a microscope SEM, it had an average aspect ratio of 1.5 and a small amount of amorphous form.

The NCM955 precursor is mixed with 47.9kg of battery grade lithium hydroxide monohydrate (battery grade, purity 99.5 wt%) in a high-speed mixer, and a 24m roller kiln is adopted for ventilation. Setting the temperature of the heating zone at 850 deg.C, and introducing oxygen-enriched air (oxygen content volume ratio is 90%, gas input is 350 Nm)³And h) putting the pasty material into a ceramic bowl for sintering, wherein the sintering time is 10h, isolating the material from air, cooling to normal temperature, weighing the weight of the material in and out, and counting the loss on ignition (the ratio of the mass of sintered powder to the mass of powder before sintering) to be 48.1%. Then crushing by using a vortex crushing machine, and controlling the humidity of the ambient air to be less than or equal to 2% during crushing to obtain the cathode material.

The particle size (D) of the material is determined_v50) 6.2 μm, wherein the weight ratio of primary particles is 92.6%, the average aspect ratio of the particles is 1.6, the total free lithium content is 0.0458%, and the specific surface area is 0.56m²(ii) in terms of/g. The ICP is used for carrying out quantitative analysis on elements of the anode material, and the structural formula of the material is calculated as follows: li_1.03Ni_0.9Co_0.05Mn_0.05Mg_0.02O₂。

Example 5

88.45kg of cobalt carbonate monohydrate (industrial grade, purity 99 wt%), 231.58kg of nickel sulfate hexahydrate (industrial grade, purity 99.0 wt%), 2.25kg of aluminum hydroxide (ceramic grade, purity 99.5 wt%) and 3.35kg of aluminum chloride (industrial grade, purity 98.0 wt%) are weighed and added into a kneader, 60.0kg of industrial acetic acid (industrial grade, purity 99.5%, the addition amount is 60% of the mass of the active component of the anode material prepared theoretically) is slowly added, and the reaction temperature of the solution is controlled to be 55 +/-5 ℃. The dripping time is 4h, after the dripping is finished, 1.46kg of nano zirconium dioxide (ceramic grade, purity 99.5 wt%) powder is added, the mixture is aged for 30h under the stirring state, the mixture is pumped into a container by a diaphragm pump and stands still, and a pipeline demagnetizer is additionally arranged on a pumping pipeline to demagnetize (magnetic field strength: 9000GS) until the impurity content is in a qualified range.

And drying the precursor material which is kept standing and precipitated by a blast oven (120 ℃/4 h). And sieving the precursor by a 325-mesh stainless steel screen to obtain an NCA type precursor, wherein the magnetic substance content of the precursor is 42 ppb. The NCA type precursor is detected by an electron microscope SEM, the average length-diameter ratio is 1.9, and a small amount of the NCA type precursor is amorphous.

The NCA-type precursor was mixed with 47.9kg of battery-grade lithium hydroxide monohydrate (battery grade, 99.5 wt%), and 10kg of isopropanol (technical grade, purity 98%) in a high-speed mixer, using a 24m vented roller kiln. Setting the temperature of the heating zone at 850 deg.C, introducing oxygen-enriched air (oxygen content volume ratio of 97%, gas input amount of 350 Nm)³And h) putting the paste material into a ceramic bowl for sintering, wherein the sintering time is 7h, isolating the material from air, cooling to normal temperature, weighing the weight of the material in and out, and counting the loss on ignition rate to be 43.2%. Then crushing by using a vortex crushing machine, and controlling the humidity of the ambient air to be less than or equal to 2% during crushing to obtain the anode material.

The particle size (D) of the material is determined_v50) 3.8 μm, wherein the weight ratio of the primary particles is 93.1%, the average length-diameter ratio of the particles is 2.0, and the length-diameter ratio is slightly increased compared with that of the precursor. The total free lithium content is 0.0120%, the specific surface area is 0.93m²(ii) in terms of/g. The ICP is used for carrying out quantitative analysis on elements of the anode material, and the structural formula of the material is calculated as follows: li_1.04Ni_0.80Co_0.15Al_0.05Zr_0.012O₂。

Comparative example 1

Mixing a commercial precursor Ni_0.80Co_0.15Al_0.05(OH)₂(Dv 50: 8.3 μm) about 102kg was charged into a high-speed mixer, and 47.9kg of battery-grade lithium hydroxide monohydrate was further added and mixed in the high-speed mixer to prepare a high-nickel ternary positive electrode material under the same preparation conditions as in example 5.

The particle size (D) of the material is determined_v50) 8.9 μm, wherein the primary particles were 3.5% by weight, and since a large number of the primary particles were agglomerated into spherical secondary particles, the average aspect ratio of the particles of the positive electrode material was 1.0, the total free lithium content was 0.2485%, and the specific surface area was 1.52m²(ii) in terms of/g. The structural formula of the material obtained by calculating after the element quantitative analysis of the anode material by ICP is as follows: li_1.04Ni_0.80Co_0.15Al_0.05O₂。

Comparative example 2

Mixing a commercial precursor Ni_0.80Co_0.15Al_0.05(OH)₂(D_v50: 9.3 μm) about 103kg was charged into a high-speed mixer, and 41.9kg of battery grade lithium carbonate was further added and mixed in the high-speed mixer to prepare a high-nickel ternary positive electrode material under the same preparation conditions as in example 5.

The particle size (D) of the material was determined_v50) 9.5 μm, wherein the primary particles were contained in an amount of 10.3% by weight, and a large amount of the primary particles were agglomerated into spherical secondary particles, so that the average aspect ratio of the particulate matter of the positive electrode material was 1.0, the content of free lithium was 0.1894%, and the specific surface area was 1.35m²(ii) in terms of/g. The ICP is used for carrying out quantitative analysis on elements of the anode material, and the structural formula of the material is calculated as follows: li_1.04Ni_0.80Co_0.15Al_0.05O₂。

Comparative example 3

The commercial precursor Ni_0.81Co_0.1Mn_0.09(OH)₂(D_v50: 12.3 μm) about 103kg was added to a high speed mixer and the above-mentioned dried material was mixed with 56.8kg of battery grade lithium acetate in a high speed mixer as in the examples3 preparing the high-nickel ternary cathode material under the same preparation conditions.

Fig. 6 is a scanning electron micrograph of a commercially available precursor, which shows that the commercially available precursor has a large particle size and is spherical secondary particles formed by agglomeration of small particles in appearance, and fig. 4 is a scanning electron micrograph of a positive electrode material prepared in this comparative example, which shows the spherical secondary particles formed by agglomeration of small particles in appearance. The particle size (D) of the material is determined_v50) 13.0 μm in which the primary particles were 5.5% by weight, and the average aspect ratio of the particulate matter of the positive electrode material was 1.1, the free lithium content was 0.1207% and the specific surface area was 1.32m because a large amount of the primary particles were agglomerated into spherical secondary particles²(ii) in terms of/g. The ICP is used for carrying out quantitative analysis on elements of the anode material, and the structural formula of the material is calculated as follows: li_1.03Ni_0.81Co_0.09Mn_0.09O₂。

Example 6

The positive electrode material prepared in the above example was subjected to the following characterization:

1. free lithium and pH value

The free lithium content and pH of the invention were measured by leaching titration using about 50g each of example 5, comparative example 1, and comparative example 2. The specific operation is as follows: 50g of positive electrode powder (code m, unit g) is taken, 100g of deionized water is added, stirring is carried out for 30min on a magnetic stirrer, then filter paper is used for filtration, 50ml of liquid is weighed by a pipette tube (50ml), and the liquid is placed into a 100ml beaker with the magnetic stirrer. The beaker was placed on an auto titrator lined with white round filter paper and 2 drops of phenolphthalein indicator (0.1g/L absolute ethanol solution) were added dropwise, typically at this time the solution was pink.

Titration was started with hydrochloric acid standard liquid (0.049mol/L, code C, unit mol/L) and when the solution changed from red to colorless, the volume V of hydrochloric acid solution consumed was recorded₁(unit: ml). 2 drops of methyl red (0.1g/L absolute ethanol solution) indicator were added dropwise to the solution, and titration of the hydrochloric acid solution was continued until the color of the solution changed from yellow to orange.

Taking out the beaker, boiling and heating to evaporate carbon dioxide generated in the solution, and cooling the solutionAnd returns to yellow. Taking down the beaker, cooling to room temperature (23 +/-2 ℃), continuing to titrate the solution, and recording the volume V of the hydrochloric acid standard solution when the solution changes from yellow to light red₂(unit: ml). The calculation formula of the leaching solution converted into the content of free lithium carbonate and lithium hydroxide in the cathode material is as follows.

Li₂CO₃(wt％)＝(V₂-V₁)*C*73.886*2*100/1000/m

LiOH(wt％)＝[V₂-2*(V₂-V₁)]*C*23.946*2*100/1000/m

Li⁺(wt％)＝V₂*C*6.94*2*100/m/1000

Reference GB/T9724-2007, 45g of deionized water is added into 5g of samples in the examples, the samples are stirred and stirred for 30min by clean magnetic force, then the samples are kept still for 90min and filtered by filter paper, the clear filtrate is taken, the pH value of the filtrate is detected by a pH meter under the condition of 23 +/-2 ℃, the pH value of the powder in the examples is obtained, and the results of the free lithium and the pH value of the above examples and comparative proportion are shown in Table 4.

Table 4 examples free lithium content and pH test results

As can be seen from table 4, the free lithium and pH values of the materials prepared in comparative examples 1 and 2 are both relatively high and much higher than the detection result of the high-nickel ternary cathode material prepared in example 5, and generally, the synthesis temperature of the high-nickel ternary material is relatively low, in this case, lithium in the raw material may be enriched on the surface of the material body without completing the diffusion reaction, which can also be confirmed from the electron microscope that the high-nickel ternary primary particles are relatively small. Generally, a lithium ion battery prepared from a material with high free lithium generates a large amount of gas in the formation process, and a lithium battery prepared from a ternary material with high nickel still generates gas after formation, so that the lithium battery can not be applied to a square lithium battery with soft package in vacuum package, and therefore, the application scene of the material can be enlarged by reducing the free lithium of the ternary material with high nickel through a new process, and the method is significant.

2. Full cell preparation and performance evaluation

The positive electrode material powders prepared in example 5 and comparative example 1 were used as positive electrode active materials respectively to prepare power batteries with a capacity of about 4.8-5.3Ah according to the 21700 cylindrical battery design, and the cylindrical batteries were designed with the same capacity margin as the standard (i.e. the volume occupied by the active materials in the cylindrical batteries is about 96% of the total closed effective volume of the cylindrical batteries). The full cell is manufactured and mainly used for inspecting high-voltage circulation and safety effects. The variety evaluated to be suitable is a 21700 steel shell battery with a winding structure, and the diameter of the manufactured battery is 21mm, and the height of the manufactured battery is 70 mm.

The positive pole piece is prepared by preparing slurry, coating, cold pressing, slitting and the like, the content of the effective positive active substance in the pole piece is 97.5 percent, and the average coating weight of the pole piece is 0.0260g/cm³The coating width of the pole piece is 62mm, and the total area of the active substances of the pole piece is 937.4cm²The thickness of the aluminum foil substrate is 13 μm, and the compacted density of the electrode plate is 3.3g/cm in terms of active material³。

The preparation method of the negative plate generally comprises the steps of preparing slurry, coating, cold pressing, slitting and the like. When the artificial graphite is adopted as the negative active material, the content of the prepared effective negative active material (artificial graphite) of the pole piece is 96.0 percent, and the coating weight of the pole piece is 0.0164g/cm²The coating width of the pole piece is 63.5mm, and the total area of the active substances of the pole piece is 1009.65cm²The thickness of the copper foil base material is 9 mu m, and the compacted density of the pole piece is 1.65g/cm calculated by active substances³。

The method comprises the steps of sequentially winding a positive plate welded with an aluminum tab, an isolation film (a PP/PE/PP composite isolation film processed by nano aluminum oxide and having the thickness of 16 mu m), a negative plate welded with a nickel tab and the like to prepare a cylindrical bare cell, sleeving the tab on an insulating ring, putting the tab into a shell, welding the nickel tab at the bottom of a cylinder by laser welding, then preparing the bare cell with a groove by coiling, drying, cooling, injecting liquid, sequentially welding protective members such as CID, PTC and Vent on the tab, packaging, standing, performing high-temperature formation (formation voltage of 0-4.2V, charging of 0.1C and discharging of 0.2C and temperature of 45 +/-2 ℃) by using an LIP-10AHB06 type high-temperature formation machine, performing capacity measurement test (test voltage of 3.0-4.2V, 0.2C and 0.5C), and selecting qualified cells for subsequent performance evaluation.

The lithium battery prepared in example 5, comparative example 1 was prepared according to the requirements of 4.9.3 of GB/T18287-2000, at ambient temperature: 20 ℃ ± 5 ℃, relative humidity: 45% -75%, atmospheric pressure: and (3) randomly drawing 2 cells from the cell to be tested under 86 kPa-106 kPa, welding a nickel strap (specification of the nickel strap: 45 x 2 x 0.1mm) on the cell core, leading out the positive electrode and the negative electrode, numbering, testing and recording the internal resistance, voltage and thickness of the cell core. The battery core is arranged in the protection box, a test lead is connected, the battery core is discharged at 1C, the lower limit voltage is 3.0V, the battery core is charged at 1C6V after the discharge is finished, when the voltage at the end of the battery core reaches the charging limit voltage, the battery core is converted into constant voltage charging, and the constant voltage charging lasts for about 6 hours until the charging current is reduced to be close to 0A. The results of table 5 and the test curves of fig. 7 and 8 were obtained by recording the leakage, smoke, fire, explosion, etc. of the cell during the test, fig. 7 is the overcharge curve of the lithium ion battery prepared in comparative example 1, and fig. 8 is the overcharge curve of the lithium ion battery prepared in example 5. As can be seen from fig. 8 and table 5, the temperature of the lithium battery increased by about 150 ℃ during the overcharge of the lithium ion battery prepared in example 5, and the lithium battery did not catch fire even though smoke occurred, in the case of charging the lithium battery with a capacity of approximately 6 times, indicating that the interface stability was good; it can be seen from fig. 7 and table 5 that the lithium battery of comparative example 1 has severe thermal runaway in about 120min (about 2 times capacity), the temperature rises to about 800 ℃, and the lithium battery is directly ignited and burned, which indicates that the stability of the interface is poor, and the thermal runaway phenomenon occurs locally in the overcharge process, which may be caused by the generation of a new phase interface in the structure of the high nickel material of the secondary particles, or by the large specific surface area of the material, and further intensive research is required.

TABLE 5 example 1C/6V overcharge test results

In summary, the high-nickel ternary cathode material provided by the invention forms a relatively stable lithium ion battery interface phase depending on optimization of a synthesis process (for example, by using the amorphous uniform precursor of the invention as a reaction raw material) and some characteristics (such as a small specific surface area) possibly possessed by the structure of the high-nickel ternary cathode material, and can prevent powder particles from directly contacting with an electrolyte in a later use process of the cathode material, so that the high-nickel ternary cathode material is favorably used in a high-voltage and long-cycle system, and the safety performance of a lithium battery is improved. The preparation method is economical and feasible, simple to operate, obvious in effect and good in application prospect.

While specific embodiments of the invention have been described with reference to the above examples, it will be understood by those skilled in the art that the foregoing examples are for purposes of illustration only and are not intended to limit the scope of the invention, which is to be construed as limited to the specific embodiments disclosed herein, and that various modifications, changes, or substitutions may be made without departing from the spirit of the invention.

Claims

1. The lithium ion battery positive electrode material is characterized in that the chemical formula of the positive electrode material is LiNi_xCo_yMn_(1-x-y)M_αO₂The element Mn can be replaced by the element Al, and the replacement proportion is 0-100%, wherein: x =0.6-0.9, y =0.01-0.2, x + y < 1; m is a doping element selected from Al, Mg and/or Zr, and alpha is more than or equal to 0 and less than 0.08; the positive electrode material comprises primary particles and secondary particles formed by agglomeration of the primary particles, wherein the mass percentage of the primary particles is 80.0-99.5%, the average length-diameter ratio of the positive electrode material is 1.5-3.0, and the content of free lithium ions in the positive electrode material is lower than 0.16 wt%;

the preparation method of the lithium ion battery anode material comprises the following steps: mixing a lithium source and a pollution-free precursor, and then performing a sintering process and a crushing process to obtain the lithium-ion battery; the pollution-free precursor contains Ni_xCo_yMn_(1-x-y)M_αA compound of R; the R is an organic acid radical ion, and is selected from acid radical ions of formic acid, acetic acid, isooctanoic acid and/or adipic acid; the non-pollution isThe dye precursor is prepared by the following steps: according to the molar ratio of nickel: cobalt: manganese = (0.6-0.9): (0.01-0.02): (0.2-0.4) mixing carbonate, sulfate, oxide and/or hydroxide containing nickel, cobalt or manganese to obtain a mixture containing nickel, cobalt and manganese, adding an organic acid and a salt, hydroxide and/or oxide containing a doping element aluminum, magnesium or zirconium, dispersing the mixture with the mixture, and drying to obtain the pollution-free precursor.

2. The positive electrode material according to claim 1, wherein x =0.7-0.9 and y = 0.01-0.2.

3. The positive electrode material according to claim 1, wherein x =0.8-0.9 and y = 0.01-0.15.

4. The positive electrode material according to claim 1, wherein the mass percentage of the primary particles is 90.0 to 99.5%.

5. The positive electrode material according to claim 1, wherein the mass percentage of the primary particles is 92.0 to 99.5%.

6. The positive electrode material according to claim 1, wherein the mass percentage of the primary particles is 95.0 to 99.5%.

7. The positive electrode material according to claim 1, wherein the positive electrode material has an average aspect ratio of 1.5 to 2.8.

8. The positive electrode material according to claim 4, wherein the positive electrode material has an average aspect ratio of 1.5 to 2.8.

9. The positive electrode material according to claim 1, wherein the aspect ratio of the positive electrode material is 1.8 to 2.2.

10. The positive electrode material according to claim 1, wherein the average particle diameter of the positive electrode material is D_v50=1-7μm。

11. The positive electrode material according to claim 4, wherein the average particle diameter of the positive electrode material is D_v50=1-7μm。

12. The positive electrode material according to claim 7, wherein the average particle diameter of the positive electrode material is D_v50=1-7μm。

13. The positive electrode material according to claim 1, wherein the average particle diameter of the positive electrode material is D_v50=2-7μm。

14. The positive electrode material according to claim 1, wherein the average particle diameter of the positive electrode material is D_v50=3-6.5μm。

15. The positive electrode material according to claim 1, wherein the positive electrode material contains free lithium ions in an amount of less than 0.10 wt%.

16. The positive electrode material according to claim 4, wherein the positive electrode material contains less than 0.10 wt% of free lithium ions.

17. The positive electrode material according to claim 7, wherein the positive electrode material contains free lithium ions in an amount of less than 0.10 wt%.

18. The positive electrode material according to claim 10, wherein the positive electrode material contains free lithium ions in an amount of less than 0.10 wt%.

19. The positive electrode material according to claim 1, wherein the positive electrode material contains free lithium ions in an amount of less than 0.06 wt%.

20. The positive electrode material according to claim 1, wherein the positive electrode material contains free lithium ions in an amount of less than 0.05 wt%.

21. The positive electrode material according to claim 1, wherein the positive electrode material contains free lithium ions in an amount of 0.012 to 0.046 wt%.

22. The positive electrode material according to claim 1, wherein the specific surface area of the positive electrode material is 0.5 to 1.2m²/g。

23. The positive electrode material according to claim 1, wherein the specific surface area of the positive electrode material is 0.5 to 1m²/g。

24. The positive electrode material according to claim 1, wherein the specific surface area of the positive electrode material is 0.5 to 0.6m²/g。

25. A method for preparing the positive electrode material of any one of claims 2 to 24, wherein the positive electrode material has a chemical formula of LiNi_xCo_yMn_(1-x-y)M_αO₂The element Mn can be replaced by the element Al, and the replacement proportion is 0-100%, wherein: x =0.6-0.9, y =0.01-0.2, x + y < 1; m is a doping element selected from Al, Mg and/or Zr, and alpha is more than or equal to 0 and less than 0.08; the positive electrode material comprises primary particles and secondary particles formed by agglomeration of the primary particles, wherein the mass percentage of the primary particles is 80.0-99.5%, the average length-diameter ratio of the positive electrode material is 1.5-3.0, and the content of free lithium ions in the positive electrode material is lower than 0.16 wt%;

the preparation method of the cathode material comprises the following steps: mixing a lithium source and a pollution-free precursor, and then performing a sintering process and a crushing process to obtain the lithium-ion battery; the pollution-free precursor contains Ni_xCo_yMn_(1-x-y)M_αA compound of R; the R is an organic acid radical ion, and is selected from acid radical ions of formic acid, acetic acid, isooctanoic acid and/or adipic acid; the pollution-free precursor is prepared by the following steps: according to the molar ratio of nickel: cobalt: manganese = (0.6-0.9): (0.01-0.02): (0.2-0.4) mixing carbonate, sulfate, oxide and/or hydroxide containing nickel, cobalt or manganese to obtain a mixture containing nickel, cobalt and manganese, adding an organic acid and a salt, hydroxide and/or oxide containing a doping element aluminum, magnesium or zirconium, dispersing the mixture with the mixture, and drying to obtain the pollution-free precursor.

26. The method of claim 25, wherein the non-contaminating precursors have an average aspect ratio of 1.5-2.6.

27. The production method according to claim 25, wherein the organic acid is added in an amount of 40 to 500% by mass based on the active ingredient of the positive electrode material.

28. The production method according to claim 26, wherein the organic acid is added in an amount of 40 to 500% by mass based on the active ingredient of the positive electrode material.

29. The production method according to claim 25, wherein the organic acid is added in an amount of 40 to 80% by mass of the active ingredient of the positive electrode material.

30. The method of claim 25, wherein the lithium source and the non-contaminating precursor satisfy a molar ratio of Li: (Ni + Co + Mn) = (1.0-1.1): 1.

31. the method of claim 26, wherein the molar ratio of lithium source to non-contaminating precursor is Li: (Ni + Co + Mn) = (1.0-1.1): 1.

32. the method of claim 27, wherein the molar ratio of lithium source to non-contaminating precursor, Li: (Ni + Co + Mn) = (1.0-1.1): 1.

33. the production method according to claim 25, wherein the lithium source is one or more selected from lithium hydroxide monohydrate, lithium oxalate, lithium carbonate, lithium nitrate, lithium acetate, lithium fluoride, lithium chloride, lithium tert-butoxide, and lithium citrate.

34. The production method according to claim 26, wherein the lithium source is one or more selected from lithium hydroxide monohydrate, lithium oxalate, lithium carbonate, lithium nitrate, lithium acetate, lithium fluoride, lithium chloride, lithium tert-butoxide, and lithium citrate.

35. The production method according to claim 27, wherein the lithium source is one or more selected from lithium hydroxide monohydrate, lithium oxalate, lithium carbonate, lithium nitrate, lithium acetate, lithium fluoride, lithium chloride, lithium tert-butoxide, and lithium citrate.

36. The method of claim 30, wherein the lithium source is selected from lithium hydroxide monohydrate or lithium carbonate.

37. The method according to claim 25, wherein the gas introduced in the sintering step is oxygen-enriched air.

38. The method of claim 37, wherein the oxygen-enriched air has an oxygen content of 30-97% by volume.

39. The method of claim 37, wherein the oxygen-enriched air has an oxygen content of 90-97% by volume.

40. The method as claimed in claim 37, wherein the flow rate of the atmosphere is 200-700Nm³/h。

41. The method as claimed in claim 37, wherein the flow rate of the atmosphere is 300-350Nm³/h。

42. The method as claimed in claim 25, wherein the sintering temperature is 800-.

43. The method as claimed in claim 26, wherein the sintering temperature is 800-.

44. The method as claimed in claim 27, wherein the sintering temperature is 800-.

45. The method as claimed in claim 30, wherein the sintering temperature is 800-.

46. The method as claimed in claim 33, wherein the sintering temperature is 800-.

47. The method as claimed in claim 37, wherein the sintering temperature is 800-.

48. The method as claimed in claim 25, wherein the sintering temperature is 830-890 ℃.

49. The method of claim 25, wherein the sintering time is 2-20 hours.

50. The method of claim 42, wherein the sintering time is 4-10 hours.

51. The production method according to any one of claims 25 to 50, wherein the pulverization process employs air-vortex pulverization.

52. A lithium ion battery positive electrode material prepared by the preparation method of any one of claims 26 to 51.

53. A lithium ion battery comprising the positive electrode material according to any one of claims 1 to 24 or the positive electrode material according to claim 52.

54. Use of the positive electrode material of any one of claims 1 to 24 or the positive electrode material of claim 52 in the field of energy.

55. The use of the lithium ion battery of claim 53 in the field of energy.

56. Use of the positive electrode material of any one of claims 1 to 24 or the positive electrode material of claim 52 in the field of electric vehicles, mobile power sources, energy storage power stations.

57. The use of the lithium ion battery of claim 53 in the field of electric vehicles, portable power sources, and energy storage power stations.