CN105375010A - Preparation method of high compaction density lithium ion cathode material - Google Patents

Abstract

A preparation method of a high compacted density lithium ion positive electrode material of the present invention comprises the following steps: (1) uniformly mixing a boron compound with a precursor material to obtain a pretreated precursor material; (2) mixing the pretreated precursor material The bulk material is fully mixed with the lithium salt to obtain a mixture; (3) the mixture is solid-phase sintered in an oxidative atmosphere, cooled and crushed to obtain the high compacted density lithium ion positive electrode material. In the present invention, by pretreatment of the precursor material, the boron compound is uniformly attached to the precursor, and then mixed with lithium salt and then sintered, so that the doping element boron is uniformly distributed in the product bulk phase to achieve uniform doping. Purpose. The high compacted density lithium ion positive electrode material prepared by the present invention has a tap density ≥ 2.3g/cm ³ , a manufactured compacted density ≥ 3.70g/cm ³ , a gram capacity of 153mAh/g for the first discharge at 1C, and a cycle retention rate of 300 cycles Up to 85% or more.

Description

A kind of preparation method of high compact density lithium ion cathode material

technical field

The invention relates to a preparation method of a battery positive electrode material, in particular to a preparation method of a high compacted density lithium ion positive electrode material.

Background technique

Lithium-ion secondary batteries have the advantages of high specific capacity, high operating voltage, wide operating temperature range, low self-discharge rate, long cycle life, no memory effect, no pollution, light weight, good safety performance, etc., and are widely used in electronic consumption products, electric vehicles and energy storage.

In recent years, with the rapid development of mobile phones and notebooks, various digital products using lithium-ion batteries have been updated and upgraded very quickly, and most of the products tend to be portable and economical; at the same time, in order to protect the ecological environment and ensure national energy security The strategic needs , Electric vehicles have become the focus of new energy vehicle development. With the development of electric vehicles and hybrid vehicles, higher requirements are placed on the energy density of lithium-ion batteries; lithium manganate and lithium iron phosphate currently used in power batteries The low energy density will be gradually replaced by ternary power batteries with higher energy density.

However, the current traditional ternary cathode material has a compaction density of 3.3-3.4g/cm ³ . Compared with lithium cobalt oxide, the compaction density is relatively low, which restricts the material's high energy density (especially the high volume specific energy density requirement). ) applications on lithium-ion batteries. Improving the compaction density of positive electrode materials is an effective way to increase the energy density of batteries.

In the Chinese patent application publication CN101847722A, the compaction density of the material is improved by grinding the micron precursor into a nanoscale, and then sintering at a high temperature to increase the compaction density of the material; but the particles prepared by this method are prone to agglomeration, and the operation is not easy to control . In the Chinese patent application publication CN102509784A, organic additives are added during grinding to suppress particle agglomeration during high-temperature reaction and obtain single crystal particles to increase the compacted density of the material. However, the mixing process of this method is more complicated, and the introduction of organic additives not only increases the cost, but also has certain hidden dangers. In the Chinese patent application publication CN102593442A, trace elements are mixed in the precursor and lithium salt mixing process, and then a high-energy-density positive electrode material is obtained through high-temperature sintering. Into the body phase. And although the maximum compacted density of its material can reach 3.85g/cm3, its 1C discharge specific capacity is only 140mAh/g. In the Chinese patent application publication CN103413931A, a boron-doped lithium ion positive electrode material Li[Li _a Mn _b Co _c Ni _d B _x ]O ₂ was prepared by co-precipitation and sol-gel methods, and hydroxides were prepared by co-precipitation Pre-sintering the precursor, and then mixing the precursor and lithium salt for pre-sintering, adding a certain amount of boron compound, and performing the second sintering to obtain the target product. This method is to mix the precursor and lithium salt for pre-sintering and then add Therefore, a second sintering is required, and the pre-sintered material has initially formed the crystal structure of the target product. On this basis, boron compounds are added, and it is difficult for boron elements to enter the crystal lattice of the product.

Contents of the invention

The technical problem to be solved in the present invention is to overcome the deficiencies of the prior art, to provide a method of low energy consumption and cost-saving high compacted density lithium ion positive electrode material, and the compacted density of the prepared lithium ion positive electrode material is ≥3.70g/ cm ³ , 1C gram capacity ≥153mAh/g.

In order to solve the problems of the technologies described above, the technical solution proposed by the present invention is:

A preparation method of a high compacted density lithium ion positive electrode material, comprising the following steps:

(1) Mixing the boron compound and the precursor material evenly, wherein the precursor material is Ni _x Co _y M _1-xy (OH) ₂ , Ni _x Co _y M _1-xy CO ₃ or Ni _x Co _y M _{1 -xy} O ₂ , where 0.4≤x≤1, 0≤y≤0.4, and 1-xy≥0, M is one or more of Mn, Al, Ti, Mg; the precursor material adopts the conventional technology Method preparation;

(2) fully mixing the mixture obtained in step (1) with the lithium salt to obtain a mixture;

(3) The mixture obtained in step (2) is solid-phase sintered in an oxidizing atmosphere, cooled, and crushed to obtain the lithium ion positive electrode material with high compacted density.

The above-mentioned preparation method, preferably, in the step (1), the mixing process of the boron compound and the precursor material is dry mixing or wet mixing; the dry mixing is to mix the boron compound and the precursor by mechanical ball milling Uniform; the wet mixing is to dissolve the boron compound in the solvent to form a clear solution, and then add the precursor material under the condition of stirring, continue to stir until the mixture is uniform, and finally dry it.

In the above preparation method, preferably, in the dry mixing process, the mechanical ball milling time is 1-10 hours, and the ball-to-material mass ratio (hereinafter referred to as the ball-to-material ratio) is 1:1-10:1.

In the above preparation method, preferably, in the wet mixing process, the mass ratio of the precursor material to the solvent is 1:0.25-1:100; the solvent is selected from one or more of water, ethanol, and acetic acid.

In the above preparation method, preferably, in the wet mixing process, the stirring time after adding the precursor material is 10-1000 min.

In the above preparation method, preferably, the boron compound is selected from one or both of boric acid and boron oxide; the amount of the boron compound added accounts for 0.1wt.% to 10wt.% of the total mass of the precursor material and the boron compound .

In the above preparation method, preferably, in the step (2), the lithium salt is selected from one or more of LiOH, Li ₂ CO ₃ , LiNO ₃ , Li ₂ C ₂ O ₄ .

The above-mentioned preparation method, preferably, the addition of described lithium salt is counted by lithium element, and the molar ratio of Li and Ni _x Co _y M _1-xy (Li and the metal in the precursor) in the precursor material is 1:0.95 ~1:1.2.

The above-mentioned preparation method, preferably, in the step (3), the oxidative atmosphere is air or oxygen; the solid-phase sintering process is divided into two stages of sintering: the temperature is first raised to 500-700°C at a heating rate of 1-10°C/min. ℃, keep warm for 3~10h; then raise the temperature to 701~1000℃, keep warm for 5~25h. Since the eutectic point of the lithium salt and the precursor is at this stage, segmental sintering can ensure that the precursor and the lithium salt can fully react.

In the above preparation method, preferably, the general formula of the obtained high compacted density lithium ion positive electrode material is LiNi _a Co _b M _c B _1-abc O ₂ , wherein 0.4≤a≤1, 0≤b≤0.4, 0≤ c≤0.3, and 1-abc>0, M is one or more of Mn, Al, Ti, Mg; the compacted density of the high compacted density lithium ion cathode material is ≥3.70g/cm ³ .

Compared with the prior art, the present invention has the advantages of:

(1) The preparation method of the present invention pretreats the precursor material, and the boron compound is uniformly attached to the precursor by wet mixing, and then the pretreated precursor is mixed with lithium salt and sintered, so that the doped The element boron is evenly distributed in the bulk phase of the product, so the purpose of uniform doping can be achieved.

(2) In the preparation method of the present invention, the boron compound is fully mixed with the precursor first, and then mixed and sintered with the lithium salt, so that the boron can be evenly doped by one sintering.

(3) The present invention promotes the growth of primary particles through boron doping, forms secondary spherical particles with stable crystal structure, and enhances the electrochemical activity of the material; at the same time, by optimizing the sintering process, the secondary agglomeration of the product is enhanced The mechanical strength of the particles, and ultimately increase the compacted density of the material.

(4) The preparation process of the present invention only needs to use one-time sintering, which is beneficial to reduce energy consumption and save costs compared with the secondary sintering in the prior art.

(5) The high compacted density lithium ion cathode material prepared by the present invention has a tap density ≥ 2.3 g/cm ³ , and a fabricated compact density ≥ 3.70 g/cm ³ . The 1C first discharge gram capacity is above 153mAh/g, and the 300-cycle cycle retention rate is above 85%. It has the advantages of good processability, high compaction density, and stable cycle performance.

Description of drawings

Fig. 1 is a scanning electron microscope image of a high compacted density lithium-ion battery positive electrode material prepared in Example 1 of the present invention.

Fig. 2 is a graph showing charge and discharge curves of a battery made of the positive electrode material of a high compacted density lithium ion battery prepared in Example 1 of the present invention.

detailed description

In order to facilitate the understanding of the present invention, the present invention will be described more fully and in detail below in conjunction with the accompanying drawings and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

Unless otherwise defined, all technical terms used hereinafter have the same meanings as commonly understood by those skilled in the art. The terminology used herein is only for the purpose of describing specific embodiments, and is not intended to limit the protection scope of the present invention.

Unless otherwise specified, the various reagents and raw materials used in the present invention are commercially available products or products that can be prepared by known methods.

Example 1:

A preparation method of a high compacted density lithium-ion battery cathode material of the present invention, comprising the following steps:

(1) Pre-treatment of precursor: mix boric acid with absolute ethanol to form a transparent and clear boric acid-ethanol solution, add precursor powder Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ under stirring to form a suspension, And continue to stir for 1 hour, then put in a water bath at 70° C., and continue to stir until the absolute ethanol is evaporated to dryness, and then dry to obtain a pretreated precursor. In the suspension, boric acid accounts for 0.5 wt.% of the total mass of the precursor and boric acid, and the mass ratio of the precursor to ethanol is 1:0.5.

(2) Ingredients: put the pretreated precursor obtained in step (1) and lithium carbonate in a mixer and mix evenly, and control the molar ratio of Li:(Ni _0.5 Co _0.2 Mn _0.3 ) to 1.08 to obtain a mixture.

(3) Sintering: Divide the mixture obtained in step (2) into two sections for sintering in an air atmosphere, firstly raise the temperature to 650°C at a heating rate of 3°C/min, and keep it for 6 hours; then raise the temperature to 950°C, and keep it for 10 hours , cooling the obtained product with the furnace, crushing and sieving to obtain LiNi _0.5 Co _0.2 Mn _0.295 B _0.005 O ₂ , a positive electrode material for a lithium ion battery with a high compacted density.

The scanning electron microscope image of the high compacted density lithium-ion battery positive electrode material prepared in this example is shown in Figure 1. The particles in the figure are secondary spherical particles formed by the agglomeration of primary particles, and the size of the primary particles is 3-5 μm. The implementation method of this embodiment controls the growth of the single crystal particles, increases the density between the particles, and enhances the mechanical strength of the secondary agglomerated particles.

Stir the high compacted density lithium-ion battery positive electrode material prepared in this example, binder PVDF, solvent NMP and conductive agent evenly to prepare the positive electrode slurry, and apply the positive electrode slurry evenly on both sides of the aluminum foil, and after drying Roll the positive electrode sheet on the electrode sheet roller press to make the positive electrode, and calculate the production compaction density and maximum compaction density of the electrode sheet by measuring the thickness of the electrode sheet. The tap density can reach 2.51g/cm ³ The solid density can reach 3.72g/cm ³ , and the maximum compacted density is 3.92g/cm ³ . The negative electrode slurry made of a certain manufacturer’s negative electrode material is evenly coated on the current collector copper foil, dried and rolled to form a negative electrode; 1.0moL/LLiPF ₆ /EC+DMC (volume ratio 1:1) is used as the electrolyte , Celgard2300 is the diaphragm, assembled into a 523450 square aluminum shell lithium-ion battery, and its electrochemical performance is tested. g, the volume specific energy density reaches 577.7mAh/cm ³ , and the cycle retention rate reaches 89.5% after 300 cycles.

Comparative example 1:

The preparation method of the lithium ion battery cathode material of this comparative example comprises the following steps:

(1) Ingredients: Put the precursor powder Ni _0.5 Co _0.2 Mn _0.3 ( _OH ) ₂ and lithium carbonate in a mixer and mix _them evenly _. material.

(2) Sintering: The mixed material obtained in step (1) adopts the same sintering system as in Example 1, and performs segmental sintering in an air atmosphere. First, the temperature is raised to 650° C. at a heating rate of 3° C./min, and the temperature is kept for 6 hours. ; Then heat up to 950°C and keep warm for 10h. Then, the obtained product was cooled with the furnace and then crushed and sieved to obtain LiNi _0.5 Co _0.2 Mn _0.3 O ₂ anode material for lithium ion battery.

After testing, the tap density of the positive electrode material of the lithium ion battery prepared in Comparative Example 1 is 2.2g/cm ³ , and the compacted density reaches 3.4g/cm ³ . When the positive electrode material is made into a battery, the Within the range, its 1C first discharge gram capacity is 158mAh/g, although its 1C gram capacity is higher than that of Example 1, but its compacted density is lower, so its volume specific energy density (537.2mAh/cm ³ ) is lower than that of Example 1 , after 300 cycles, the cycle retention rate was 84.6%.

Example 2:

A preparation method of a high compacted density lithium-ion battery cathode material of the present invention, comprising the following steps:

(1) Pretreatment of precursors: Mix boric acid with absolute ethanol to form a transparent and clear boric acid-ethanol solution, add precursor powder Ni _0.5 Co _0.2 Mn _0.25 Mg _0.05 CO ₃ under stirring to form a suspension, And continue to stir for 1 hour, then put it in a 70°C water bath, continue to stir until the solvent is evaporated to dryness, and dry to obtain a pretreated precursor. In the suspension, boric acid accounts for 0.5 wt.% of the total mass of the precursor and boric acid, and the mass ratio of the precursor to ethanol is 1:0.5.

(2) Ingredients: the pretreated precursor and lithium carbonate obtained in step (1) are placed in a mixer and mixed evenly, and the molar ratio of Li:(Ni _0.5 Co _0.2 Mn _0.25 Mg _0.05 ) is controlled to be 1.08 to obtain a mixture .

(3) Sintering: The mixture obtained in step (2) is sintered in sections in an air atmosphere, and the temperature is first raised to 650° C. at a heating rate of 3° C./min and kept for 6 hours; then heated to 950° C. and kept for 10 hours. The obtained product is cooled with the furnace, crushed and sieved to obtain LiNi _0.5 Co _0.2 Mn _0.25 Mg _0.045 B _0.005 O ₂ anode material for lithium ion battery with high compacted density.

After testing, the high compacted density lithium-ion battery cathode material prepared in this example has a tap density of 2.56 g/cm ³ and a compact density of 3.75 g/cm ³ . When the positive electrode material is made into a battery, in the range of 2.8-4.2V, its 1C initial discharge gram capacity is 155.9mAh/g, and its volume specific energy density reaches 584.6mAh/cm ³ . After 300 cycles, the cycle retention rate Reached 88.9%.

Example 3:

A preparation method of a high compacted density lithium-ion battery cathode material of the present invention, comprising the following steps:

(1) Pre-treatment of precursor: mix boric acid with deionized water to form a transparent and clear boric acid-water solution, and add ternary precursor powder Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ during the stirring process to form a suspension , and continuously stirred for 1 hour, then placed on an electric furnace, continued to stir until the water evaporated, and then dried to obtain a pretreated ternary precursor material. In the suspension, the percentage of boric acid to the total mass of the ternary precursor material and boric acid is 0.5 wt.%, and the mass ratio of the precursor to water is 1:0.5.

(2) Ingredients: The pretreated ternary precursor and lithium carbonate obtained in step (1) are mixed evenly in a mixer, and the molar ratio of Li:(Ni _0.6 Co _0.2 Mn _0.2 ) is controlled to be 1.10 to obtain a mixture .

(3) Sintering: The mixture obtained in step (2) is sintered in multiple stages in an air atmosphere, and the temperature is first raised to 650°C at a heating rate of 3°C/min, and kept for 6h; then heated to 900°C, kept for 10h, and the The obtained product was cooled with the furnace and then crushed and sieved to obtain LiNi _0.6 Co _0.2 Mn _0.195 B _0.005 O ₂ , a positive electrode material for a lithium-ion battery with a high compacted density.

After testing, the high compacted density lithium-ion battery cathode material prepared in this example has a tap density of 2.43 g/cm ³ and a compact density of 3.70 g/cm ³ . In the range of ~4.2V, its 1C initial discharge gram specific capacity is 163.2mAh/g, and after 300 cycles, its cycle retention rate reaches 87.7%.

Example 4:

A preparation method of a high compacted density lithium-ion battery cathode material of the present invention, comprising the following steps:

(1) Pretreatment of the precursor: Grind the boric acid first, then sieve it with a 200-mesh screen, and then place the sieved boric acid and the ternary precursor material Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ Ball milled in a ball mill for 2 hours, wherein the ball-to-material ratio is 1.2:1, to obtain a pretreated ternary precursor material.

(2) Ingredients: The pretreated ternary precursor material obtained in step (1) and lithium hydroxide are placed in a mixer and mixed evenly, and the molar ratio of Li:(Ni _0.8 Co _0.1 Mn _0.1 ) is controlled to be 1.08 , to obtain the mixture.

(3) Sintering: The mixture obtained in step (2) is sintered in sections in an oxygen atmosphere. First, the temperature is raised to 550° C. at a heating rate of 3° C./min, and the temperature is kept for 6 hours; then the temperature is raised to 780° C., and the temperature is kept for 10 hours. Then the obtained product is cooled with the furnace, crushed and sieved to obtain LiNi _0.8 Co _0.1 Mn _0.095 B _0.005 O ₂ anode material for lithium ion battery with high compacted density.

After testing, the high compacted density lithium-ion battery cathode material prepared in this example has a tap density of 2.40 g/cm ³ and a compact density of 3.70 g/cm ³ . In the range of ~4.2V, its 1C initial discharge gram capacity is 174.6mAh/g, and after 300 cycles, its cycle retention rate reaches 85.7%.

Comparative example 2:

The preparation method of the lithium ion battery cathode material of this comparative example comprises the following steps:

(1) Put the ternary precursor material Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ and lithium hydroxide in a mixer and mix evenly, and control the molar ratio of Li:(Ni _0.8 Co _0.1 Mn _0.1 ) to 1.04, get the mixture;

(2) Place the obtained mixture in an oxygen atmosphere and sinter at 550°C for 6 hours, then place it in a ball mill for 2 hours with boric acid, wherein the ratio of balls to materials is 1.2:1; after the ball milling, place it in an oxygen atmosphere at 780°C After sintering for 10 hours, the resulting product was cooled with the furnace, crushed and sieved to obtain LiNi _0.8 Co _0.1 Mn _0.095 B _0.005 O ₂ , the cathode material for lithium ion batteries.

After testing, the tap density and compaction density of the lithium ion battery positive electrode material prepared in this comparative example can reach 2.33g/cm ³ , and the positive electrode material can reach ^2.8-4.2V when it is made into a battery. , its 1C first discharge gram capacity is 170.0mAh/g. Although its compacted density is not much different from that of Example 4, its 1C discharge capacity is lower than that of Example 4. After 300 cycles, the cycle retention rate is 84%.

Example 5:

A preparation method of a high compacted density lithium-ion battery cathode material of the present invention, comprising the following steps:

(1) Pre-treatment of precursor: mix boron oxide with ethanol to form a transparent and clear boron oxide-ethanol solution, and add ternary precursor powder Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ while stirring to form a suspension , and continued to stir for 1 hour, then placed in a 70°C water bath, and continued to stir until the solvent was evaporated to dryness and dried to obtain a pretreated precursor. In the suspension, boron oxide accounts for 1.0 wt.% of the total mass of the precursor and boron oxide, and the mass ratio of the precursor to ethanol is 1:1.

(2) Ingredients: Put the pretreated precursor obtained in step (1) and lithium carbonate in a mixer and mix evenly, and control the molar ratio of Li:(Ni _0.5 Co _0.2 Mn _0.3 ) to 1.06 to obtain a mixture.

(3) Sintering: The mixture obtained in step (2) is sintered in sections in an air atmosphere, and the temperature is first raised to 650°C at a heating rate of 3°C/min, and kept for 6h; then heated to 970°C, kept for 10h, The resulting product is cooled in a furnace, crushed and sieved to obtain LiNi _0.5 Co _0.2 Mn _0.29 B _0.01 O ₂ , a positive electrode material for a lithium-ion battery with a high compacted density.

After testing, the high compacted density lithium-ion battery cathode material prepared in this example has a tap density of 2.6 g/cm ³ and a compact density of 3.80 g/cm ³ . When the positive electrode material is made into a battery, in the range of 2.8-4.2V, its 1C initial discharge gram capacity is 154.3mAh/g, and its volume specific energy density reaches 586.3mAh/cm ³ . After 300 cycles, the cycle retention rate Reached 88.9%.

Embodiment 6:

A preparation method of a high compacted density lithium-ion battery cathode material of the present invention, comprising the following steps:

(1) Pre-treatment of precursor: mix boron oxide with ethanol to form a transparent and clear boron oxide-ethanol solution, and add ternary precursor powder Ni _0.7 Co _0.15 Mn _0.15 (OH) ₂ while stirring to form a suspension , and continued to stir for 1 hour, then placed in a 70°C water bath, and continued to stir until the solvent was evaporated to dryness and dried to obtain a pretreated precursor. In the suspension, boron oxide accounts for 2.0 wt.% of the total mass of the precursor and boron oxide, and the mass ratio of the precursor to ethanol is 1:1.5.

(2) Ingredients: put the pretreated precursor obtained in step (1) and lithium carbonate in a mixer and mix evenly, and control the molar ratio of Li:(Ni _0.5 Co _0.2 Mn _0.3 ) to 1.04 to obtain a mixture.

(3) Sintering: The mixture obtained in step (2) is sintered in sections in an air atmosphere, and the temperature is first raised to 550° C. at a heating rate of 3° C./min and kept for 6 hours; then heated to 800° C. and kept for 10 hours. The resulting product is cooled in a furnace, crushed and sieved to obtain LiNi _0.7 Co _0.15 Mn _0.13 B _0.02 O ₂ , a positive electrode material for a lithium-ion battery with a high compacted density.

After testing, the high compacted density lithium-ion battery cathode material prepared in this example has a tap density of 2.54 g/cm ³ and a compact density of 3.70 g/cm ³ . When the cathode material is made into a battery, its 1C initial discharge gram capacity is 167.2mAh/g in the range of 2.8-4.2V, and its cycle retention rate reaches 86.2% after 300 cycles.

Claims (10)

1. a preparation method of high compacted density lithium ion cathode material, comprising the following steps: (1) Mix the boron compound and the precursor material uniformly to obtain the pretreated precursor material, wherein the precursor material is Ni _x Co _y M _1-xy (OH) ₂ , Ni _x Co _y M _1-xy CO ₃ or Ni _x Co _y M _1-xy O ₂ , where 0.4≤x≤1, 0≤y≤0.4, and 1-xy≥0, M is one or more of Mn, Al, Ti, Mg; (2) fully mixing the pretreated precursor material obtained in step (1) with the lithium salt to obtain a mixture; (3) The mixture obtained in step (2) is solid-phase sintered in an oxidative atmosphere, cooled, and crushed to obtain the high compacted density lithium ion positive electrode material. 2. the preparation method as claimed in claim 1 is characterized in that, in described step (1), the mixing process of boron compound and precursor material is dry mixing or wet mixing; Described dry mixing is boron The compound and the precursor are uniformly mixed by mechanical ball milling; the wet mixing method is to firstly dissolve the boron compound in the solvent, then add the precursor material under stirring condition, continue stirring until the mixture is uniform, and finally dry it. 3. The preparation method according to claim 2, characterized in that, in the dry mixing process, the mechanical ball milling time is 1-10 hours, and the ball-to-material ratio is 1:1-10:1. 4. The preparation method according to claim 2, wherein, in the wet mixing process, the mass ratio of the precursor material to the solvent is 1:0.25 to 1:100; the solvent is selected from water, ethanol, acetic acid one or more of. 5. The preparation method according to claim 2, characterized in that, in the wet mixing process, the stirring time after adding the precursor material is 10-1000 min. 6. The preparation method according to any one of claims 2 to 5, wherein the boron compound is selected from one or both of boric acid and boron oxide; 0.1wt.%-10wt.% of the total mass of the boron compound. 7. The preparation method according to any one of claims 2-5, characterized in that, in the step (2), the lithium salt is selected from LiOH, Li ₂ CO ₃ , LiNO ₃ , Li ₂ C ₂ O ₄ one or more of. 8. preparation method as claimed in claim 7 is characterized in that, the add-on of described lithium salt is in lithium element, and the mol ratio of Ni _x Co _y M _1-xy in Li and precursor material is 1:0.95 ~1:1.2. 9. The preparation method according to any one of claims 2 to 5, characterized in that, in the step (3), the oxidative atmosphere is air or oxygen; the solid phase sintering process is divided into two stages of sintering: At a heating rate of 10°C/min, first raise the temperature to 500-700°C and keep it for 3-10 hours; then raise the temperature to 701-1000°C and keep it for 5-25 hours. 10. The preparation method according to any one of claims 2 to 5, wherein the general formula of the obtained high compacted density lithium ion positive electrode material is LiNi _a Co _b M _c B _1-abc O ₂ , wherein 0.4 ≤a≤1, 0≤b≤0.4, 0≤c≤0.3, and 1-abc>0, M is one or more of Mn, Al, Ti, Mg; the high compacted density lithium ion positive electrode The compacted density of the material is ≥3.70g/cm ³ .