WO2021136243A1 - Modified lithium nickel cobalt aluminate positive electrode material, preparation method therefor and application thereof - Google Patents

Abstract

The present invention relates to the technical field of lithium ion batteries, and disclosed are a modified lithium nickel cobalt aluminate positive electrode material, a preparation method therefor, and an application thereof. The positive electrode material has the following composition as shown in general formula I: Li_1+αNi_xCo_yAl_zM_dG_eP_fO₂ formula I, wherein 0≤α≤0.1, 0.80≤x≤0.99, 0.01≤y≤0.20, 0.01≤z≤0.06, 0≤d≤0.005, 0≤e≤0.004, 0≤f≤0.04; M is at least one selected from among Ca, Sr, Ba, Zr, Y, Ce, Mg, Ti and Mn; G is at least one selected from among Ca, Sr, Ba, Zr, Y, La, Ce, Mg, Ti, B and W; and P is at least one selected from among Ni, Co, Al, Nb, W and Mn; and d, e and f are not 0 at the same time. The positive electrode material has high cycle rate performance and low surface residual Li, and a battery made therefrom has excellent cycle stability, heat stability and safety performance.

Description

Modified nickel cobalt lithium aluminate cathode material and preparation method and application thereof

Cross-references to related applications

This application claims the rights and interests of the Chinese patent application 201911395194.9 filed on December 30, 2019, the content of which is incorporated herein by reference.

Technical field

The invention relates to the technical field of lithium ion batteries, in particular to a modified nickel cobalt lithium aluminate positive electrode material and a preparation method and application thereof.

Background technique

Lithium-ion battery is a kind of green and recyclable energy. It has the advantages of high voltage, high energy density, good cycle performance, high safety, low self-discharge, no memory effect, etc. It is widely used in 3C electronic equipment, space power supply, portable electric Tools, weaponry and other fields; at the same time, lithium-ion batteries have also been widely used in energy storage equipment, electric vehicles, and electric buses.

In recent years, with the rapid rise and promotion of Tesla electric vehicles, various brands of electric vehicles have begun to partially replace fuel vehicles. my country’s 13th Five-Year Plan proposes that the energy density of automotive lithium-ion batteries should reach 300Wh/kg. Japan, the United States, Germany and other countries have also proposed a series of measures to stop the production of fuel vehicles from 2025 to 2030. Lithium-ion batteries will usher in a comprehensive Explosive growth. However, with the promotion of lithium-ion batteries, their safety performance and cruising range have become the focus of widespread attention. How to improve the energy density of lithium-ion batteries while improving their safety performance and cycle performance has become a key issue that needs to be solved urgently.

At present, the ternary material that has been widely used and commercialized is mainly lithium nickel cobalt manganese oxide (Ni:Co:Mn=3:3:3 or 5:2:3), and its energy density is only about 200Wh/kg. Meet the high energy density requirements of new energy vehicles. The most direct and effective way to improve the energy density of ternary materials is to increase the content of nickel in the materials, that is, to increase to more than 80%. Lithium nickel cobalt aluminate (NCA) is the first high-nickel ternary material used in vehicle power batteries. The biggest feature of NCA that distinguishes it from other ternary materials is that aluminum has the effect of stabilizing the crystal structure, which can improve the stability of NCA materials, but it does not have electrochemical activity, which will reduce the specific discharge capacity of the material. In addition, high-nickel NCA materials are more sensitive to the environment, and the surface residual Li is higher, and the gas production and swelling problems during the cycle are more serious. How to reduce the surface residual Li and increase the NCA without affecting the specific discharge capacity of the material The cyclic stability and thermal stability of materials are problems that need to be solved urgently.

Summary of the invention

The purpose of the present invention is to overcome the problems of poor cycle stability and thermal stability of high nickel materials for batteries in the prior art and high residual Li on the surface, and to provide a doped, coated and modified nickel cobalt aluminate Lithium cathode material and preparation method and application thereof. The nickel-cobalt lithium aluminate cathode material has high cycle rate performance and low surface residual Li, and the battery prepared therefrom has good cycle stability, thermal stability and safety performance .

In order to achieve the above objective, the first aspect of the present invention provides a modified nickel cobalt lithium aluminate cathode material, wherein the cathode material has a composition represented by the general formula I:

Li _1+α Ni _x Co _y Al _z M _d G _e P _f O ₂ Formula I,

Among them, 0≤α≤0.1, 0.80≤x≤0.99, 0.01≤y≤0.20, 0.01≤z≤0.06, 0≤d≤0.005, 0≤e≤0.004, 0≤f≤0.04,

M is selected from at least one of Ca, Sr, Ba, Zr, Y, Ce, Mg, Ti, and Mn; G is selected from Ca, Sr, Ba, Zr, Y, La, Ce, Mg, Ti, B, and W P is selected from at least one of Ni, Co, Al, Nb, W, and Mn; wherein, d, e and f are not 0 at the same time.

The second aspect of the present invention provides a method for preparing a modified nickel cobalt lithium aluminate cathode material, wherein the method includes the following steps:

(1) The nickel salt, the cobalt salt and the optional aluminum salt are configured as a mixed salt solution; the compound containing the doping element M, the alkali and the complexing agent are respectively configured as the solution; the mixed salt solution, the lye, The complexing agent solution and the compound solution containing the doping element M are respectively passed into the reaction kettle to perform the first reaction, and the obtained slurry is separated, washed, dried and sieved to obtain the positive electrode material precursor;

(2) Mix the cathode material precursor, lithium source, compound containing doping element G and optional aluminum compound obtained in step (1), and perform the first sintering of the mixed material in an oxygen atmosphere to obtain The first sintering material;

(3) After the first sintering material obtained in step (2) and the first lye Y1 are first stirred and mixed, the coating solution containing P element and the second lye Y2 are added, and after the coating reaction is carried out, continue After the second stirring, filter and dry to obtain the coating material;

(4) In an oxygen atmosphere, the coating material obtained in step (3) is sintered a second time to obtain a second sintered material;

(5) sieving and removing iron from the second sintered material obtained in step (4) to obtain a positive electrode material;

Preferably, the positive electrode material has a composition represented by the general formula I:

Li _1+α Ni _x Co _y Al _z M _d G _e P _f O ₂ Formula I,

Where 0≤α≤0.1, 0.80≤x≤0.99, 0.01≤y≤0.20, 0.01≤z≤0.06, 0≤d≤0.005, 0≤e≤0.004, 0≤f≤0.04,

M is selected from at least one of Ca, Sr, Ba, Zr, Y, Ce, Mg, Ti, and Mn; G is selected from Ca, Sr, Ba, Zr, Y, La, Ce, Mg, Ti, B, and W P is selected from at least one of Ni, Co, Al, Nb, W, and Mn; and d, e, and f are not 0 at the same time.

The third aspect of the present invention provides a modified nickel cobalt lithium aluminate cathode material prepared by the preparation method of the present invention.

The fourth aspect of the present invention provides an application of the modified nickel cobalt lithium aluminate cathode material of the present invention in a lithium ion battery.

Through the above technical solutions, the doped, coated and modified lithium nickel cobalt aluminate cathode material provided by the present invention and the preparation method and application thereof achieve the following beneficial technical effects:

(1) The nickel cobalt lithium aluminate cathode material provided by the present invention has high cycle rate performance and low surface residual Li, and the battery prepared therefrom has good cycle stability, thermal stability and safety performance.

(2) In the preparation method of the nickel-cobalt lithium aluminate cathode material provided by the present invention, the Al element and the doping element can be introduced in the precursor preparation stage or the one-time sintering stage, and can be introduced according to the state of the doped element and the desired The doping effect is adjusted, and the flexibility is higher.

(2) In the method for preparing nickel-cobalt lithium aluminate cathode material provided by the present invention, the high-nickel cathode material is washed and coated in a low-concentration lye at the same time, and the common ion effect of the low-concentration lye can be used in the washing process. While removing the residual Li on the surface, it also inhibits the precipitation of Li in the internal lattice of the material, and can effectively solve the problem of lithium deficiency caused by prolonging the coating time and improving the coating uniformity during high-volume processing, which can simplify the process flow and achieve uniformity Cladding.

(3) In the preparation method of the nickel-cobalt lithium aluminate cathode material provided by the present invention, the first sintered material can be coated with a layer of uniform low-nickel or nickel-free coating material on the surface after the coating reaction treatment. The coating material _{can further react with residual Li on the surface after high temperature secondary sintering under O 2} atmosphere, and the coating layer formed has good Li ion transport characteristics, which can significantly improve the capacity and rate performance of the material.

(4) The raw materials used in the present invention are all common raw materials on the market, with abundant reserves and low prices, and are suitable for large-scale industrial production.

Description of the drawings

Figure 1 is an SEM image of a sample sampled in step S5 in Example 1 when the magnification is 10K;

Figure 2 is a SEM image of the sample sampled in step S5 in Comparative Example 2 when the magnification is 10K;

Fig. 3 is a capacity-rate graph of the positive electrode materials described in Example 1 and Comparative Example 2;

4 is a graph of capacity-cycle times of the positive electrode materials described in Example 1 and Comparative Example 2;

5 is a DSC chart of the positive electrode materials described in Example 3 and Comparative Example 4. FIG.

Detailed ways

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the end values of each range, between the end values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges. These values The scope should be considered as specifically disclosed herein.

The first aspect of the present invention provides a modified nickel cobalt lithium aluminate positive electrode material, wherein the positive electrode material has a composition represented by the general formula I:

Li _1+α Ni _x Co _y Al _z M _d G _e P _f O ₂ Formula I,

Among them, 0≤α≤0.1, 0.80≤x≤0.99, 0.01≤y≤0.20, 0.01≤z≤0.06, 0≤d≤0.005, 0≤e≤0.004, 0≤f≤0.04,

M is selected from at least one of Ca, Sr, Ba, Zr, Y, Ce, Mg, Ti, and Mn; G is selected from Ca, Sr, Ba, Zr, Y, La, Ce, Mg, Ti, B, and W P is selected from at least one of Ni, Co, Al, Nb, W, and Mn; wherein, d, e and f are not 0 at the same time.

In the present invention, doping elements are introduced into the traditional nickel cobalt lithium aluminate positive electrode material, so that the provided nickel cobalt lithium aluminate positive electrode material has a more stable interlayer structure and higher thermal stability, and the doped element It can also increase the electrical conductivity and Li ion migration rate of the material, and improve the cycle stability of the material during the charge and discharge process.

Furthermore, the inventors found that when the M is selected from at least one of Ca, Sr, Ba, Zr, Y, Mg, Ti and Mn, preferably at least one of Ga, Mg, Zr and Mn , The cathode material provided has more excellent performance.

Furthermore, the inventors found that the G is selected from at least one of Sr, Ba, Zr, Y, Ti, B and W, preferably at least one of Zr, Y, Ti, B and Sr. , The cathode material provided has more excellent performance.

Furthermore, the inventors found that when P is selected from at least one of Ni, Co, Al, Nb, W and Mn, preferably at least one of Ni, Co, Nb and Mn, the provided positive electrode The material has more excellent performance.

According to the present invention, furthermore, the M and G are the same, and 0≤d+e≤0.005.

The second aspect of the present invention provides a method for preparing a modified nickel cobalt lithium aluminate cathode material, wherein the method includes the following steps:

(1) The nickel salt, cobalt salt and optional aluminum salt mole ratio x:y:z are configured as a mixed salt solution; the compound containing the doping element M, the alkali and the complexing agent are respectively configured as the solution; The mixed salt solution, lye solution, complexing agent solution, and compound solution containing doping element M are respectively passed into the reaction kettle for the first reaction, and the obtained slurry is separated, washed, dried and sieved to obtain the positive electrode material Precursor;

(2) Mix the cathode material precursor, lithium source, compound containing doping element G and optional aluminum compound obtained in step (1), and perform the first sintering of the mixed material in an oxygen atmosphere to obtain The first sintering material;

(3) After the first sintering material obtained in step (2) and the first lye Y1 are first stirred and mixed, the coating solution containing P element and the second lye Y2 are added, and after the coating reaction is carried out, continue After the second stirring, filter and dry to obtain the coating material;

(4) In an oxygen atmosphere, the coating material obtained in step (3) is sintered a second time to obtain a second sintered material;

(5) Sieving and removing iron from the second sintered material obtained in step (4) to obtain a positive electrode material.

In the present invention, the molar ratio of nickel salt, cobalt salt and aluminum salt in the mixed salt solution is x:y:z.

In the present invention, adding doping elements in step (1) and/or step (2) can significantly improve the stability of the bulk structure of the nickel cobalt lithium aluminate cathode material. At the same time, after the first sintered material obtained in step (2) is washed and coated, the residual Li on the surface of the positive electrode material can be reduced to a certain extent. In the second sintering treatment, the surface of the particles contains P element The coating can react with the residual Li on the surface to further reduce the residual Li content on the surface of the particles, and can form a P-rich and low-Ni coating layer on the surface of the particles, thereby improving the rate performance of the prepared positive electrode material. It makes the battery made by it have good cycle stability and safety performance.

According to the present invention, the positive electrode material has a composition represented by the general formula I:

Li _1+α Ni _x Co _y Al _z M _d G _e P _f O ₂ Formula I,

Where 0≤α≤0.1, 0.80≤x≤0.99, 0.01≤y≤0.20, 0.01≤z≤0.06, 0≤d≤0.005, 0≤e≤0.004, 0≤f≤0.04,

M is selected from at least one of Ca, Sr, Ba, Zr, Y, Ce, Mg, Ti, and Mn; G is selected from Ca, Sr, Ba, Zr, Y, La, Ce, Mg, Ti, B, and W P is selected from at least one of Ni, Co, Al, Nb, W, and Mn; and d, e, and f are not 0 at the same time.

Furthermore, the inventors found that when the M is selected from at least one of Ca, Sr, Ba, Zr, Y, Mg, Ti and Mn, preferably at least one of Ga, Mg, Zr and Mn , The nickel cobalt lithium aluminate cathode material provided by the present invention has more excellent performance.

Furthermore, the inventors found that the G is selected from at least one of Sr, Ba, Zr, Y, Ti, B and W, preferably at least one of Zr, Y, Ti, B and Sr. , The nickel cobalt lithium aluminate cathode material provided by the present invention has more excellent performance.

Furthermore, the inventors found that when the P is selected from at least one of Ni, Co, Al, Nb, W and Mn, preferably at least one of Ni, Co, Nb and Mn, the present invention The provided nickel cobalt lithium aluminate cathode material has more excellent performance.

According to the present invention, preferably, the M and G are the same, and 0≤d+e≤0.005.

According to the present invention, in step (1), the concentrations of the mixed salt solution, the compound solution containing the doping element M, the alkali solution, and the complexing agent solution are 0.5-5 mol/L, 0.05-0.5 mol/L, 1 -11mol/L, 1-15mol/L.

According to the present invention, the concentrations of the mixed salt solution, the compound solution containing the doping element M, the alkali solution, and the complexing agent solution are respectively 1-3 mol/L, 0.1-0.3 mol/L, 2-10 mol/L, 2 -13mol/L.

According to the present invention, the added amount of the complexing agent solution is such that the concentration of the complexing agent in the reaction system is 8-11 g/L.

According to the present invention, in step (1), the nickel salt, cobalt salt, and aluminum salt are respectively at least one of nickel, cobalt, and aluminum sulfate, chloride, nitrate and acetate.

According to the present invention, the alkali is at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide.

According to the present invention, the complexing agent is at least one of salicylic acid, ammonium nitrate, ammonium sulfate, ammonium chloride, ammonia, sulfosalicylic acid and ethylenediaminetetraacetic acid.

According to the present invention, the compound containing the doping element M is at least one of a soluble salt containing the doping element M, oxide nanopowder, hydroxide nanopowder, oxyhydroxide nanopowder and sol.

According to the present invention, the doping element M is at least one of Ca, Sr, Ba, Zr, Y, Ce, Mg, Ti, and Mn.

In the present invention, the inventors discovered that after doping the nickel cobalt lithium aluminate cathode material with the doping elements defined in the present invention, the layered structure can be more complete, the cycle performance and thermal stability of the material can be improved, and the It can effectively avoid the corrosion of the electrolyte to the positive electrode material during the charging and discharging process, and improve the cycle performance.

According to the present invention, the conditions of the first reaction include: the reaction temperature is 30-90°C, preferably 40-70°C; the reaction pH is 9-13.5, preferably 10.6-12.5.

According to the present invention, the drying conditions include: 100-200°C, preferably 120-160°C; and the drying time is 1-10h, preferably 3-6h.

According to the present invention, in step (1), the positive electrode material precursor has a composition represented by the general formula II:

Ni _x1 Co _y1 Al _z1 M _d1 (OH) _2+z1 Formula II

Among them, 0.80≤x1≤0.99, 0.01≤y1≤0.20, 0≤z≤0.06, 0≤d≤0.005.

According to the present invention, in step (2), the lithium source is selected from at least one of lithium hydroxide, lithium carbonate and lithium nitrate.

According to the present invention, the compound containing doping element G is at least one of oxide nanopowder, hydroxide nanopowder and oxyhydroxide nanopowder containing doping element G.

Furthermore, the doping element G is at least one of Ca, Sr, Ba, Zr, Y, La, Ce, Mg, Ti, W, and Mn.

According to the present invention, in step (2), the added amount of the compound containing the doping element G is added according to the molar ratio of G:(Ni+Co+Al+M+G) of 0-0.004.

According to the present invention, in step (2), the added amount of the aluminum compound is added according to the molar ratio of Al:(Ni+Co+Al+M+G) of 0-0.06.

According to the present invention, in step (2), the added amount of the lithium source is added according to the molar ratio of Li:(Ni+Co+Al+M+G) of 1.01-1.10.

According to the present invention, the first sintering conditions include: a sintering temperature of 600-900°C, preferably 650-800°C; and a sintering time of 6-20h, preferably 8-15h.

According to the present invention, the first sintering material has a composition represented by the general formula III:

Li _1+α1 Ni _x2 Co _y2 Al _z2 M _d2 G _e1 O ₂ Formula III

Among them, 0≤α1≤0.1; 0.80≤x2≤0.99, 0.01≤y2≤0.20, 0.01≤z2≤0.06, 0≤d2≤0.005, 0≤e1≤0.004.

According to the present invention, in step (3), the first lye Y1 is selected from NaOH and/or LiOH.

In the present invention, the first lye Y1 is mixed with the first sintering material, and the coating solution containing P element is added to the second lye Y2 for coating reaction. The first lye Y1 can replace the H ₂ O solution at a certain time. To a certain extent, the precipitation of Li in the crystal lattice of the first sintering material is suppressed, and the coating time is prolonged, and the liquid inlet speed of the second lye Y2 and the coating solution is reduced, and the coating uniformity is ensured.

According to the present invention, the concentration of the first lye Y1 is 0.05-1 mol/L.

In the present invention, the inventors found that the use of a lower concentration of lye, specifically, a lye with a concentration of 0.05-1 mol/L as the first lye Y1, can further inhibit the precipitation of Li in the crystal lattice, so that the obtained The positive electrode material has more excellent performance.

Furthermore, the concentration of the first lye Y1 is 0.1-0.6 mol/L.

At the same time, the inventor’s extensive research has shown that when the weight ratio of the first sintering material to the first lye Y1 is 6:2-1:5, the prepared positive electrode material can achieve higher capacity and better performance. Good cycle performance.

Furthermore, the ratio of the amount of the first sintering material to the first lye is 5:2-1:3.

According to the present invention, the first stirring and mixing time is 0.1-8 min, preferably 0.5-5 min.

According to the present invention, the second lye Y2 is selected from at least one of ammonia, NaOH, LiOH and KOH, more preferably NaOH and/or LiOH.

According to the present invention, the concentration of the second lye Y2 is 1-10 mol/L, preferably 2-8 mol/L.

According to the present invention, the coating solution containing P element is at least one of a soluble salt containing P element, oxide nanopowder and sol.

In the present invention, the first sintered material is coated by wet co-precipitation, so that a coating layer containing P element is formed on the surface of the prepared positive electrode material. The coating layer has both ionic and electronic conductivity properties and can Significantly improve the rate performance of the prepared cathode material. At the same time, the coating layer can significantly improve the stability of the positive electrode material, effectively avoid the corrosion of the positive electrode material by the electrolyte, and thereby make the battery prepared therefrom have good cycle stability and safety performance.

Furthermore, the P element is at least one of Ni, Co, Al, Nb, W, and Mn.

According to the present invention, the concentration of the coating solution is 0.1-3 mol/L, preferably 0.5-2 mol/L.

According to the present invention, the added amount of the coating solution containing P element is added according to the molar ratio of P:(Ni+Co+Al+M+G) of 0-0.04.

According to the present invention, the coating reaction time is 4-60 min, preferably 5-30 min.

According to the present invention, the method of adding the coating solution and the second lye Y2 is a peristaltic pump and/or a metering pump.

According to the present invention, the time of the second stirring is 0-15 min, preferably 1-10 min.

According to the present invention, the drying conditions include: the drying temperature is 100-200°C, preferably 120-160°C; the drying time is 1-10h, preferably 2-6h.

According to the present invention, the coating solution containing P element is Co salt and/or Mn salt;

In the present invention, the inventors have found that when the coating solution containing P element is Co salt and/or Mn salt, the coating layer formed by reacting with the second alkali solution Y2 is effective in reducing the surface alkalinity after the second sintering. Impurities, improving electrochemical performance has a better effect. The enrichment of Co on the surface can improve the conductivity of lithium ions and the rate performance, and the enrichment of Mn on the surface can improve the safety of high nickel materials.

According to the present invention, the Co salt is selected from at least one of cobalt sulfate, cobalt nitrate, cobalt carbonate and cobalt fluoride.

According to the present invention, the added amount of the Co salt is added according to the molar ratio of Co: the first sintering material of 0.001-0.03:1.

In the present invention, in order to further improve the rate performance and stability of the positive electrode material, the inventor has studied the amount of Co salt added. The research shows that when the amount of Co salt added is based on the molar ratio of Co: the first sintered material, it is 0.001-0.03. :1 add, the thickness of the coating layer obtained is at the nanometer level, and the residual alkali of the sample after sintering is at a relatively low level. The inventors have discovered that when the coating amount is too large, it is easy to cause the lack of lattice Li; when the coating amount is too small, the performance improvement effect is poor, so the coating amount must be controlled within a certain range.

According to the present invention, the Mn salt is selected from at least one of manganese sulfate, manganese nitrate and manganese chloride.

According to the present invention, the added amount of the Mn salt is added according to the molar ratio of Mn: the first sintered material of 0.001-0.02:1.

In the present invention, in order to further improve the rate performance and stability of the positive electrode material, the inventor has studied the amount of Co salt added. The research shows that when the amount of Mn salt added is 0.001-0.02 according to the molar ratio of Mn to the first sintered material :1 added, the obtained coating layer is more stable, and will not affect the capacity of the positive electrode material.

According to the present invention, in step (4), the second sintering conditions include: the sintering temperature is 200-800°C, preferably 300-700°C; the sintering time is 3-12h, preferably 5-10h.

According to the present invention, the method further includes, before step (2), heat-treating the positive electrode precursor obtained in step (1) to obtain a positive electrode material precursor II.

In the present invention, the inventors found that, before step (2), after heat treatment of the positive electrode material precursor obtained in step (1), the cycle stability and thermal stability of the prepared positive electrode material precursor II can be significantly improved As well as the safety performance, the battery made by it has more excellent performance.

Furthermore, the heat treatment conditions include: when the heat treatment temperature is 300-700°C and the heat treatment time is 2-10 hours, the obtained cathode material precursor II has improved cycle stability, thermal stability and safety performance.

Preferably, the heat treatment temperature is 400-600°C; the heat treatment time is 3-8h.

According to the present invention, the heat treatment is performed in an oxygen and/or air atmosphere.

According to the present invention, the positive electrode material precursor II has a composition represented by the general formula IV:

Ni _x1 Co _y1 Al _z1 M _d1 O _1+z1/2 Formula IV

Among them, 0.80≤x1≤0.99, 0.01≤y1≤0.20, 0≤z1≤0.06, 0≤d1≤0.005.

The third aspect of the present invention provides a modified nickel cobalt lithium aluminate cathode material prepared by the preparation method of the present invention.

The fourth aspect of the present invention provides an application of the modified nickel cobalt lithium aluminate cathode material of the present invention in a lithium ion battery.

Hereinafter, the present invention will be described in detail through examples. In the following embodiments,

Make button batteries as follows:

First, the composite nickel-cobalt-manganese multi-element positive electrode active material for non-aqueous electrolyte secondary batteries, acetylene black and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 95%:2.5%:2.5%, and then coated on aluminum foil and combined The drying process is carried out, and the positive pole piece with a diameter of 12 mm and a thickness of 120 μm is stamped and formed with a pressure of 100 MPa, and then the positive pole piece is placed in a vacuum drying oven at 120° C. for 12 hours.

The negative electrode uses a Li metal sheet with a diameter of 17mm and a thickness of 1mm; the separator uses a polyethylene porous film with a thickness of 25μm; the electrolyte uses 1mol/L LiPF6, ethylene carbonate (EC) and diethyl carbonate (DEC), etc.量mixture.

The positive pole piece, the separator, the negative pole piece and the electrolyte are assembled into a 2025 button cell in an Ar gas glove box with a water content and an oxygen content of less than 5 ppm, and the battery at this time is regarded as an unactivated battery.

The performance evaluation of the produced button battery is defined as follows:

After making the button cell, leave it for 2 hours. After the open-circuit voltage is stable, charge it to the cut-off voltage of 4.3V with the current density of the positive electrode being 0.1C, then charge it at a constant voltage for 30 minutes, and then discharge it to the cut-off voltage of 3.0V at the same current density. Do the same way again, and use the battery at this time as an activated battery.

Battery capacity test: Test the first discharge capacity of the battery with the current density of the positive electrode as 0.1C at 25°C and the voltage range of 3.0-4.3V. The battery capacity is shown in Table 2;

The rate performance test is as follows: use an activated battery, charge at a current density of 0.1C at 25°C, a voltage range of 3.0-4.3V, and use 0.1C, 0.2C, 0.33C, 0.5C, 1C, and 2C current densities. Discharge, test the rate performance of the battery, the rate performance of the battery is shown in Table 3;

The cycle performance test is as follows: using an activated battery, using a current density of 1C at 45°C and a voltage range of 3.0-4.3V, the capacity retention rate of the material is examined for 80 cycles. The cycle performance of the battery is shown in Table 2;

The evaluation of residual alkali and thermal stability of the positive electrode material is defined as follows:

The residual alkali test on the surface is as follows: add 5g sample to 95ml pure water, seal and stir for 5min, then separate solid-liquid, weigh the filtrate and test the content of lithium carbonate and lithium hydroxide by acid-base titration, primary sintering material and positive electrode material Calculated by the content of lithium carbonate and lithium hydroxide, the content of residual alkali on the surface is shown in Table 1;

The thermal stability test is as follows: the thermal decomposition temperature of the positive electrode material is used to characterize the thermal stability of the positive electrode material, and the thermal decomposition temperature of the positive electrode material is tested by the DSC thermal analysis method. The thermal decomposition temperature of the positive electrode material is shown in Table 2;

The surface morphology of the material was characterized by scanning electron microscope (SEM).

Example 1

S1. Dissolve nickel sulfate and cobalt sulfate in a metal molar ratio of 0.95:0.05 to obtain a 2mol/L mixed salt solution, dissolve magnesium nitrate into a magnesium nitrate solution with a concentration of 0.1mol/L, and dissolve calcium nitrate to a concentration of In a 0.1mol/L calcium nitrate solution, sodium hydroxide is dissolved into an alkali solution with a concentration of 8mol/L, and ammonia water is dissolved into a complexing agent solution with a concentration of 6mol/L.

S2. Add the mixed salt solution, magnesium nitrate solution, calcium nitrate solution, alkali solution, and complexing agent solution into the reactor in parallel to react, and the mixed salt solution inlet flow rate is 400mL/h, magnesium nitrate solution, calcium nitrate solution The solution inlet flow rate is 16mL/h, the reaction pH is controlled to 11.5-11.7, the reaction temperature is 60°C, and the ammonia concentration in the reaction system is controlled to 8-11g/L. When the reaction is completed, stop the liquid feeding and keep the reaction liquid The temperature and stirring speed remain unchanged. After stirring for 10 minutes, the Mg and Ca-doped nickel cobalt hydroxide slurry is subjected to solid-liquid separation, washing, heat treatment in an oxygen atmosphere at 500°C for 5 hours, and sieving to obtain spherical Ni _0.9462 Co _0.0498 Mg _0.0020 Ca _0.0020 O oxide precursor.

_{S3. Mix} lithium hydroxide, Ni _0.9462 Co 0.0498 Mg _0.0020 Ca _0.0020 O precursor and alumina in a high-mixer at a molar ratio of 1.05:0.97:0.03, and carry out the mixed materials in an oxygen atmosphere furnace. One roasting, heating rate of 5℃/min, heating to 730℃, roasting for 12h, natural cooling and cooling, you can get Li _1.05 Ni _0.9179 Co _0.0483 Al _0.030 Mg _0.0019 Ca _0.0019 O ₂ .

S4. Configure coating solution: configure the concentration of 2mol/L cobalt sulfate and manganese sulfate solutions, configure 8mol/L NaOH lye Y2 and 0.1mol/L NaOH lye Y1, when coating, Co and the first sintering The molar ratio of the material is 0.01:1, the molar ratio of Mn to the first sintering material is 0.005:1, and the molar ratio of the second lye Y2 to the total moles of the Co solution and the Mn solution is 2:1.

S5. Grind the material obtained by the primary roasting, take the broken material and add it to the 0.1mol/L NaOH solution Y1, keep the mass ratio of the material to 0.1mol/L NaOH lye at 2:1, stir for 3 minutes and use peristalsis The pump simultaneously dripped two solutions of cobalt sulfate and manganese sulfate and 8mol/L lye Y2. The dripping time was 10min. After the dripping, continue to stir for 5min, then filter and dry at 120°C for 5h. Take a sample to characterize the surface morphology of the sample after the coating reaction is shown in Figure 1.

S6. The dried material is subjected to a secondary sintering treatment in an oxygen atmosphere, the heating rate is 3°C/min, the temperature is 700°C, and the time is 8h. The material after the second sintering is sieved to remove iron to obtain the nickel cobalt lithium aluminate cathode material A1: Li _1.035 Ni _0.9043 Co _0.0574 Al _0.0296 M _n0.0049 Mg _0.0019 Ca _0.0019 O ₂ .

Example 2

The positive electrode material was prepared according to the same method as in Example 1, except that in step S1, nickel sulfate, cobalt sulfate, and aluminum sulfate were dissolved in a ratio of 0.92:0.05:0.03 to the metal molar ratio to obtain a 2mol/L mixed salt solution, and finally A spherical Ni _0.9163 Co _0.0498 Al _0.0299 Mg _0.0020 Ca _0.0020 O oxide precursor was obtained.

In step S3, lithium hydroxide and Ni _0.9163 Co _0.0498 Al _0.0299 Mg _0.0020 Ca _0.0020 O precursor were mixed uniformly in a high mixer at a molar ratio of 1.05:1, and finally Li _1.05 Ni _0.9163 Co _0.0498 Al _0.0299 Mg _0.0020 Ca _0.0020 O ₂ .

The other steps are the same as in Example 1, and the cathode material A2 is finally obtained: Li _1.035 Ni _0.9027 Co _0.0589 Al _0.0294 M _n0.0049 Mg _0.0020 Ca _0.0020 O ₂ .

Example 3

The cathode material was prepared according to the method of Example 1, except that: in step S3, lithium hydroxide and Ni _0.9462 Co _0.0498 Mg _0.0020 Ca _0.0020 O precursor, aluminum oxide, and zirconium oxide were prepared according to the molar ratio of 1.05:0.969:0.03:0.001. The ratio is mixed in a high mixer, and Li _1.05 Ni _0.9169 Co _0.0483 Al _0.030 Mg _0.0019 Ca _0.0019 Zr _0.001 O _{2 is} obtained after one sintering.

The other steps are the same as in Example 1, and finally the cathode material A3 is obtained: Li _1.035 Ni _0.9033 Co _0.0574 Al _0.0296 Mg _0.0019 Ca _0.0019 Zr _0.001 Mn _0.0049 O ₂ .

Example 4

The cathode material was prepared according to the method of Example 1, except that: in step S2, the Mg and Ca-doped nickel cobalt hydroxide slurry was subjected to solid-liquid separation and washing, and then dried at 120°C for 5 hours to obtain spherical Ni _0.9462 Co _0.0498 Mg _0.0020 Ca _0.0020 (OH) ₂ hydroxide precursor.

The other steps are the same as in Example 1, and finally the cathode material A4 is obtained: Li _1.035 Ni _0.9043 Co _0.0574 Al _0.0296 M _n0.0049 Mg _0.0019 Ca _0.0019 O ₂ .

Example 5

The cathode material was prepared according to the method of Example 1, except that: in step S1, manganese nitrate was used to replace magnesium nitrate and calcium nitrate, and the concentration of the manganese nitrate solution was 0.2mol/L, and finally spherical Ni _0.9462 Co _0.0498 Mn _0.0040 O was obtained. Oxide precursor.

The other steps are the same as in Example 1, and finally the cathode material A5: Li _1.035 Ni _0.9042 Co _0.0573 Al _0.0296 Mn _0.0089 O _{2 is obtained} .

Example 6

The cathode material was prepared according to the same method as in Example 1, except that: in step S4, the lye Y1 used was a 0.1 mol/L LiOH solution.

The other steps are the same as in Example 1, and finally the cathode material A6: Li _1.035 Ni _0.9043 Co _0.0574 Al _0.0296 M _n0.0049 Mg _0.0019 Ca _0.0019 O _{2 is obtained} .

Example 7

The positive electrode material was prepared according to the same method in Example 5, except that: in step S3, the lithium hydroxide and Ni _0.9462 Co _0.0498 Mn _0.0040 O, alumina, and zirconia precursors were prepared in a molar ratio of 1.05:0.969:0.03:0.001 , Mix well in a high mixer, and finally get Li _1.05 Ni _0.9169 Co _0.0483 Al _0.030 Mn _0.0039 Al _0.003 Zr _0.001 O ₂ .

The other steps are the same as in Example 5, and the cathode material A7 is finally obtained: Li _1.035 Ni _0.9033 Co _0.0589 Al _0.0296 Mn _0.0038 Zr _0.0095 O ₂ .

Example 8

The positive electrode material was prepared according to the same method in Example 1, except that: in step S4, the coating solution was only 2mol/L cobalt sulfate solution, the molar ratio of Co to the first sintering material was 0.015:1, and the second lye The molar ratio of Y2 to the Co solution is 2:1. In step S5, the solution added by the peristaltic pump is a cobalt sulfate solution and an 8 mol/L second lye Y2.

The other steps are the same as in Example 1, and finally the cathode material A8 is obtained: Li _1.035 Ni _0.9043 Co _0.0623 Al _0.0296 Mg _0.0019 Ca _0.0019 O ₂

Comparative example 1

The cathode material was prepared by the same method as in Example 1, except that: in step S5, H ₂ O was used to replace the 0.1 mol/L NaOH solution Y1.

The other steps are the same as in Example 1, and finally the cathode material D1 is obtained: Li _1.035 Ni _0.9043 Co _0.0574 Al _0.0296 M _n0.0049 Mg _0.0019 Ca _0.0019 O ₂ .

Comparative example 2

The cathode material was prepared by the method of Example 1, except that: in step S4, only 0.1 mol/L NaOH lye Y1 was prepared.

In step S5, the material obtained by the primary roasting is pulverized, and the pulverized material is added to the 0.1 mol/L NaOH solution Y1, and the mass ratio of the material to the 0.1 mol/L NaOH lye is maintained at 2:1. After stirring for 15 minutes Then it was filtered, dried at 120°C, and dried for 5 hours, and then sampled. The surface morphology of the test sample is shown in Figure 2.

The other steps are the same as in Example 1, and finally the cathode material D2: Li _1.05 Ni _0.9179 Co _0.0483 Al _0.030 Mg _0.0019 Ca _0.0019 O _{2 is obtained} .

Comparative example 3

The cathode material was prepared according to the method of Example 2, except that: in step S1, the magnesium nitrate solution and the calcium nitrate solution were not added, and finally a spherical Ni _0.92 Co _0.05 Al _0.03 O oxide precursor was obtained. .

The other steps are the same as in Example 1, and finally the cathode material D3: Li _1.035 Ni _0.9064 Co _0.0591 Al _0.0296 M _n0.0049 O _{2 is obtained} .

Comparative example 4

The cathode material was prepared according to the method of Example 1, except that: in step S1, no magnesium nitrate solution and calcium nitrate solution were added, and finally a spherical Ni _0.95 Co _0.05 O oxide precursor was obtained;

Example 1 is consistent with other steps embodiment, the finally obtained positive electrode material prepared positive electrode material _{D4: Li 1.035 Ni 0.9087 Co 0.0577 Al} 0.0296 M n0.0049 O 2.

Table 1

Table 2

table 3

It can be seen from Figure 1 and Figure 2 that in Example 1 and Comparative Example 2, after sampling in step S5, the morphology of the sample can be seen. In Example 1, after the coating treatment, the surface of the sample is uniformly formed. In Comparative Example 2, the surface of the sample is relatively smooth, and the boundary of the primary particles is relatively clear.

It can be seen from Table 2 that the positive electrode material A1 provided in Example 1 has higher capacity and better cycle performance than the positive electrode material D1 provided in Comparative Example 1, indicating that the low concentration of the first lye Y1 helps Reduce the loss of lattice Li and prevent overwashing.

Furthermore, the positive electrode material provided in Example 6 using LiOH solution as the first lye Y1 can not only prevent the loss of lattice Li, but also can further improve the capacity and cycle performance of the positive electrode material.

From Table 1 and Figures 3 and 4, it can be seen that the positive electrode material A1 provided in Example 1 and the positive electrode material D2 provided in Comparative Example 2 have a higher content of residual lithium carbonate and lithium hydroxide on the surface of the positive electrode material. It is low, and the rate and cycle performance of the positive electrode material are significantly improved. The possible reason for this is that during the preparation process of the positive electrode material A1, the primary sintered material is coated, and then a coating layer is formed on the surface of the primary sintered material, and during the secondary sintering process, the coating layer can further interact with the second sintered material. The lithium carbonate and lithium hydroxide in a sintering material react, thereby reducing the content of residual lithium carbonate and lithium hydroxide on the surface of the positive electrode material. The low content of the above alkaline impurities can effectively prevent the jelly problem during homogenization, reduce the difficulty in the use of high nickel materials, and the formed active material coating layer can improve the cycle and rate performance of the positive electrode material.

Furthermore, the positive rate performance of the positive electrode material provided by Example 8 using a single Co element as the coated P element is more excellent, in particular, the rate performance at 1C and 2C.

It can be seen from Table 1 and FIG. 5 that compared with the positive electrode materials provided in Comparative Examples 3-4, the positive electrode materials provided in Examples 1-8 have improved cycle performance and thermal stability. It shows that the introduction of doping elements M and/or G into the positive electrode material can improve the stability of the interlayer structure of the positive electrode material, thereby improving the cycle performance and thermal stability of the positive electrode material.

Furthermore, compared with the positive electrode material provided in Example 5, the positive electrode material provided in Example 7 has better cycle performance, indicating that the simultaneous introduction of doping elements M and G is more effective than the introduction of doping element M alone. In other words, the cycle performance of the positive electrode material can be further improved.

At the same time, compared with Example 5 where the doping element M is manganese, when the doping element M is magnesium and calcium, the cycle performance and thermal stability of the cathode material are more excellent, which further shows that the type of doping element It also has an impact on the thermal stability and cycle performance of the cathode material.

It can be seen from Table 1-3 that the positive electrode material A4 provided in Example 4 and the positive electrode material A1 provided in Example 1 are compared with the positive electrode material A1 provided in Example 1. Because the precursor material has not undergone high-temperature heat treatment, the The reaction activity in the chemical process is worse than that of the corresponding oxide precursor in Example 1, so that the residual lithium carbonate and lithium hydroxide content on the surface of the primary sintered material in Example 4 are higher, which in turn leads to a decrease in the capacity of the positive electrode material.

The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be regarded as the disclosed content of the present invention. All belong to the protection scope of the present invention.

Claims (12)

1. A modified nickel cobalt lithium aluminate positive electrode material, wherein the positive electrode material has a composition represented by the general formula I:

   Li _1+α Ni _x Co _y Al _z M _d G _e P _f O ₂ Formula I,

   Among them, 0≤α≤0.1, 0.80≤x≤0.99, 0.01≤y≤0.20, 0.01≤z≤0.06, 0≤d≤0.005, 0≤e≤0.004, 0≤f≤0.04,

   M is selected from at least one of Ca, Sr, Ba, Zr, Y, Ce, Mg, Ti, and Mn; G is selected from Ca, Sr, Ba, Zr, Y, La, Ce, Mg, Ti, B, and W P is selected from at least one of Ni, Co, Al, Nb, W, and Mn; wherein, d, e and f are not 0 at the same time.
2. The nickel cobalt lithium aluminate cathode material according to claim 1, wherein the M is selected from at least one of Ca, Sr, Ba, Zr, Y, Mg, Ti and Mn, preferably Ga, Mg, Zr And at least one of Mn;

   Preferably, the G is selected from at least one of Sr, Ba, Zr, Y, Ti, B and W, preferably at least one of Zr, Y, Ti, B and Sr;

   Preferably, the P is selected from at least one of Ni, Co, Al, Nb, W and Mn, preferably at least one of Ni, Co, Nb and Mn;

   Preferably, the M and G are the same, and 0≤d+e≤0.005.
3. A method for preparing a modified nickel cobalt lithium aluminate cathode material, wherein the method includes the following steps:

   (1) The nickel salt, the cobalt salt and the optional aluminum salt are configured as a mixed salt solution; the compound containing the doping element M, the alkali and the complexing agent are respectively configured as the solution; the mixed salt solution, the lye, The complexing agent solution and the compound solution containing the doping element M are respectively passed into the reaction kettle to perform the first reaction, and the obtained slurry is separated, washed, dried and sieved to obtain the positive electrode material precursor;

   (2) Mix the cathode material precursor, lithium source, compound containing doping element G and optional aluminum compound obtained in step (1), and perform the first sintering of the mixed material in an oxygen atmosphere to obtain The first sintering material;

   (3) After the first sintering material obtained in step (2) is first stirred and mixed with the first lye Y1, the coating solution containing element P and the second lye Y2 are added to carry out the coating reaction, and then continue to proceed. After the second stirring, filter and dry to obtain the coating material;

   (4) In an oxygen atmosphere, the coating material obtained in step (3) is sintered a second time to obtain a second sintered material;

   (5) sieving and removing iron from the second sintered material obtained in step (4) to obtain a positive electrode material;

   Preferably, the positive electrode material has a composition represented by the general formula I:

   Li _1+α Ni _x Co _y Al _z M _d G _e P _f O ₂ Formula I,

   Where 0≤α≤0.1, 0.80≤x≤0.99, 0.01≤y≤0.20, 0.01≤z≤0.06, 0≤d≤0.005, 0≤e≤0.004, 0≤f≤0.04,

   M is selected from at least one of Ca, Sr, Ba, Zr, Y, Ce, Mg, Ti, and Mn; G is selected from Ca, Sr, Ba, Zr, Y, La, Ce, Mg, Ti, B, and W P is selected from at least one of Ni, Co, Al, Nb, W, and Mn; and d, e, and f are not 0 at the same time.
4. The preparation method according to claim 3, wherein the M is selected from at least one of Ca, Sr, Ba, Zr, Y, Mg, Ti and Mn, preferably at least one of Ga, Mg, Zr and Mn One kind

   Preferably, the G is selected from at least one of Sr, Ba, Zr, Y, Ti, B and W, preferably at least one of Zr, Y, Ti, B and Sr;

   Preferably, the P is selected from at least one of Ni, Co, Al, Nb, W and Mn, preferably at least one of Ni, Co, Nb and Mn;

   Preferably, the M and G are the same, and 0≤d+e≤0.005.
5. The preparation method according to claim 3 or 4, wherein, in step (1), the concentration of the mixed salt solution, the compound solution containing the doping element M, the alkali solution, and the complexing agent solution are respectively 0.5-5 mol/ L, 0.05-0.5mol/L, 1-11mol/L, 1-15mol/L;

   Preferably, the concentrations of the mixed salt solution, the compound solution containing the doping element M, the alkali solution, and the complexing agent solution are respectively 1-3 mol/L, 0.1-0.3 mol/L, 2-10 mol/L, 2- 13mol/L;

   Preferably, the amount of the complexing agent solution added is such that the concentration of the complexing agent in the reaction system is 8-11 g/L;

   In step (1), the nickel salt, cobalt salt, and aluminum salt are respectively at least one of nickel, cobalt, and aluminum sulfate, chloride, nitrate, and acetate;

   Preferably, the alkali is at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide;

   Preferably, the complexing agent is at least one of salicylic acid, ammonium nitrate, ammonium sulfate, ammonium chloride, ammonia, sulfosalicylic acid and ethylenediaminetetraacetic acid;

   Preferably, the compound containing doping element M is at least one of a soluble salt containing doping element M, oxide nanopowder, hydroxide nanopowder, oxyhydroxide nanopowder and sol;

   More preferably, the doping element M is at least one of Ca, Sr, Ba, Zr, Y, Ce, Mg, Ti and Mn;

   Preferably, the conditions of the first reaction include: the reaction temperature is 30-90°C, preferably 40-70°C; the reaction pH is 9-13.5, preferably 10.6-12.5;

   Preferably, the drying conditions include: a drying temperature of 100-200°C, preferably 120-160°C; a drying time of 1-10h, preferably 3-6h;

   In step (1), the positive electrode material precursor has a composition represented by the general formula II:

   Ni _x1 Co _y1 Al _z1 M _d1 (OH) _2+z1 Formula II, where 0.80≤x1≤0.99, 0.01≤y1≤0.20, 0≤z1≤0.06, 0≤d1≤0.005.
6. The preparation method according to any one of claims 3-5, wherein in step (2), the lithium source is selected from at least one of lithium hydroxide, lithium carbonate and lithium nitrate;

   Preferably, the compound containing doping element G is at least one of oxide nanopowder, hydroxide nanopowder and oxyhydroxide nanopowder containing doping element G;

   More preferably, the doping element G is at least one of Ca, Sr, Ba, Zr, Y, La, Ce, Mg, Ti, B and W;

   Preferably, in step (2), the added amount of the compound containing doping element G is added according to a molar ratio of G:(Ni+Co+Al+M+G) of 0-0.004;

   Preferably, in step (2), the added amount of the aluminum compound is added according to the molar ratio of Al:(Ni+Co+Al+M+G) of 0-0.06;

   Preferably, in step (2), the added amount of the lithium source is added according to the molar ratio of Li:(Ni+Co+Al+M+G) of 1.01-1.10;

   Preferably, the first sintering conditions include: a sintering temperature of 600-900°C, preferably 650-800°C; and a sintering time of 6-20h, preferably 8-15h;

   Preferably, the first sintering material has a composition represented by the general formula III:

   Li _1+α1 Ni _x2 Co _y2 Al _z2 M _d2 G _e1 O ₂ Formula III, where 0≤α1≤0.1; 0.80≤x2≤0.99, 0.01≤y2≤0.20, 0.01≤z2≤0.06, 0≤d2≤0.005 , 0≤e1≤0.004.
7. The preparation method according to any one of claims 3-6, wherein in step (3), the first lye Y1 is selected from NaOH and/or LiOH;

   Preferably, the concentration of the first lye Y1 is 0.05-1 mol/L, preferably 0.1-0.6 mol/L;

   Preferably, the weight ratio of the first sintering material to the first lye Y1 is 6:2-1:5, preferably 5:2-1:3;

   Preferably, the first stirring and mixing time is 0.1-8 min, preferably 0.5-5 min;

   Preferably, the second lye Y2 is selected from at least one of ammonia, NaOH, LiOH and KOH, more preferably NaOH and/or LiOH;

   Preferably, the concentration of the second lye Y2 is 1-10 mol/L, preferably 2-8 mol/L;

   Preferably, the coating solution containing P element is at least one of a soluble salt containing P element, oxide nanopowder and sol;

   More preferably, the P element is at least one of Ni, Co, Al, Nb, W and Mn;

   Preferably, the concentration of the coating solution is 0.1-3 mol/L, preferably 0.5-2 mol/L;

   Preferably, the added amount of the coating solution containing P element is added according to the molar ratio of P:(Ni+Co+Al+M+G) of 0-0.04;

   Preferably, the coating reaction time is 4-60 min, preferably 5-30 min;

   Preferably, the method of adding the coating solution and the second lye Y2 is a peristaltic pump and/or a metering pump;

   Preferably, the time of the second stirring is 0-15 min, preferably 1-10 min;

   Preferably, the drying conditions include: a drying temperature of 100-200°C, preferably 120-160°C; and a drying time of 1-10h, preferably 2-6h.
8. The preparation method according to claim 7, wherein the coating solution containing P element is Co salt and/or Mn salt;

   Preferably, the Co salt is selected from at least one of cobalt sulfate, cobalt nitrate, cobalt carbonate and cobalt fluoride; more preferably, the amount of the Co salt added is 0.001 to the molar ratio of Co: the first sintering material. 0.03:1 add;

   Preferably, the Mn salt is selected from at least one of manganese sulfate, manganese nitrate and manganese chloride;

   More preferably, the added amount of the Mn salt is added according to the molar ratio of Mn: the first sintered material of 0.001-0.02:1.
9. The preparation method according to any one of claims 3-8, wherein in step (4), the second sintering conditions include: a sintering temperature of 200-800°C, preferably 300-700°C; and a sintering time It is 3-12h, preferably 5-10h.
10. The preparation method according to any one of claims 3-9, wherein the method further comprises, before step (2), heat-treating the positive electrode precursor obtained in step (1) to obtain positive electrode material precursor II;

    Preferably, the heat treatment conditions include: the heat treatment temperature is 300-700°C, preferably 400-600°C; the heat treatment time is 2-10h, preferably 3-8h;

    Preferably, the heat treatment is performed in an oxygen and/or air atmosphere;

    Preferably, the positive electrode material precursor II has a composition represented by the general formula IV:

    Ni _x1 Co _y1 Al _z1 M _d1 O _1+z1/2 Formula IV, where 0.80≤x1≤0.99, 0.01≤y1≤0.20, 0≤z1≤0.06, 0≤d1≤0.005.
11. A modified nickel cobalt lithium aluminate cathode material prepared by the preparation method of any one of claims 3-10.
12. An application of the modified nickel cobalt lithium aluminate cathode material according to any one of claims 1-2 and 11 in a lithium ion battery.

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