High-nickel single-crystal ternary positive electrode material as well as preparation method and application thereof

Abstract

The invention discloses a high-nickel single-crystal ternary positive electrode material as well as a preparation method and application thereof, and belongs to the technical field of battery materials. The preparation method of the high-nickel single-crystal ternary positive electrode material comprises the following steps: mixing a ternary precursor with a lithium source, pre-sintering, washing with water, and drying to obtain a dried material; mixing the dried material with a supplementary lithium source and a doping agent, and performing first sintering to obtain a positive electrode base material; and mixing the positive electrode base material with the coating agent, and then carrying out secondary sintering to obtain the high-nickel single-crystal ternary positive electrode material. The washing process is added after pre-sintering, residual alkali of the pre-sintered material is reduced to a lower level, and then a small amount of lithium is supplemented for gradient sintering, so that Li < + > / Ni < 2 + > cation mixing of the material can be reduced, damage to the surface structure of the material caused by washing in the sintering process is repaired, the integrity of the surface structure of the material is improved, doping and coating are combined, and the surface structure of the material is improved. And the high-nickel single-crystal ternary positive electrode material with low residual alkali and long circulation effect is prepared.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of battery materials, in particular to a high-nickel single-crystal ternary positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] High-nickel ternary positive electrode materials gradually become one of the most widely used materials in the field of lithium ion batteries due to high energy density and relatively optimal electrochemical performance. The polycrystalline secondary spherical particles formed by agglomeration of nanoscale primary particles have attracted much attention. However, due to the existence of grain boundaries, the polycrystalline ternary positive electrode material generates local stress in the process of volume shrinkage and expansion, which causes serious lattice distortion and microcracks of the material, hinders the transmission of ions and electrons in the secondary particles, further accelerates the side reaction between the electrolyte and the newly exposed surface of the positive electrode material, and HF corrosion leads to the dissolution of transition metals, consumes the electrolyte and rapidly decays the capacity, and in severe cases, causes the battery to jump, which threatens the service life and safety of the battery.

[0003] The single-crystal positive electrode material is composed of submicron primary particles, and due to the absence of grain boundaries in the polycrystalline positive electrode material, the formation of microcracks is effectively alleviated, and the structural stability and cycle performance of the material are improved. However, the surface of the high-nickel single-crystal ternary positive electrode material often has a high residual alkali after sintering, and the main components of the residual alkali are lithium hydroxide and lithium carbonate mixture. A large amount of residual alkali on the surface of the material not only reacts with PVDF during electrode slurry process, increases the slurry viscosity, causes the slurry to gel, is not conducive to coating, and affects the processing performance of the material, but also reacts with the electrolyte in the cycle process to produce CO2, O2 and other gases, which causes the battery to swell and bulge, affects the service life of the battery and also brings serious safety hazards. Therefore, it is crucial to reduce the residual alkali on the surface of the high-nickel single-crystal ternary positive electrode material.

[0004] The existing technology mainly reduces the content of LiOH in the residual alkali on the surface of the high-nickel single-crystal positive electrode material by adopting various coating strategies, but the content of Li2CO3 in the residual alkali is still high. Water washing is a relatively common and efficient method for reducing Li2CO3 in residual alkali at present, but Li + / H + ion exchange inevitably occurs during water washing, causing Li to precipitate in the surface layer of the material, forming a rock salt phase on the surface of the material, increasing the surface impedance of the material, leading to capacity decay and poor electrochemical performance. Therefore, under the condition of ensuring good electrochemical performance of the high-nickel single-crystal positive electrode material, reducing the content of lithium carbonate in the residual alkali of the high-nickel single-crystal positive electrode material is still a difficult problem faced by the industry.

[0005] In view of this, the application is proposed. SUMMARY

[0006] The application aims to provide a high-nickel single-crystal ternary positive electrode material, a preparation method thereof and an application thereof, so as to solve or improve the above technical problems.

[0007] The application can be implemented as follows:

[0008] In a first aspect, the application provides a preparation method of a high-nickel single-crystal ternary positive electrode material, comprising the following steps: mixing a ternary precursor with a lithium source and then pre-sintering to obtain pre-sintered material; washing and drying the pre-sintered material to obtain dried material; mixing the dried material with a lithium supplement source and a dopant to obtain first mixed material; performing first sintering on the first mixed material to obtain positive electrode base material; mixing the positive electrode base material with a coating agent to obtain second mixed material; and performing second sintering on the second mixed material to obtain the high-nickel single-crystal ternary positive electrode material.

[0009] In an optional embodiment, the mixing of the ternary precursor with the lithium source comprises at least one of the following features:

[0010] Feature 1: the molecular formula of the ternary precursor is Ni x Co y Mn 1-x-y (OH)2, wherein 0.90≤x≤0.97 and 0.02≤y<0.06;

[0011] Feature 2: the median particle size of the ternary precursor is 3μm~4μm;

[0012] Feature 3: the specific surface area of the ternary precursor is 8m 2 / g~15m 2 / g;

[0013] Feature 4: the lithium source comprises at least one of lithium carbonate, lithium hydroxide, lithium nitrate, lithium dihydrogen phosphate and lithium acetate, and preferably comprises lithium hydroxide;

[0014] Feature 5: the molar ratio of Li in the lithium source to the transition metal elements in the ternary precursor is 0.7:1 to 1.03:1, and preferably 0.8:1 to 1.01:1;

[0015] Feature 6: the mixing rotation speed of the ternary precursor and the lithium source is 200rpm~800rpm, the mixing time is 30min~60min, and the mixing temperature is not higher than 50℃.

[0016] In an optional embodiment, the pre-sintering is performed at 450℃~650℃ for 4h~6h.

[0017] In an optional embodiment, the heating rate during the pre-sintering is 2℃ / min~10℃ / min.

[0018] In an optional embodiment, the pre-sintering is performed in an oxygen atmosphere.

[0019] In optional embodiments, the water washing and drying comprise at least one of the following features:

[0020] Feature 7: the temperature of the water used for water washing is 5-12°C;

[0021] Feature 8: the solid-liquid ratio of water washing is 1:2 to 1:0.5, preferably 1:1.2 to 1:0.8;

[0022] Feature 9: the time of water washing is 2-10 min, preferably 2-5 min;

[0023] Feature 10: the water washing is carried out under a protective atmosphere; preferably, the protective atmosphere is a nitrogen atmosphere and / or an argon atmosphere;

[0024] Feature 11: the drying temperature is 100-160°C, and the drying time is 5-10 h.

[0025] In optional embodiments, the mixing of the dried material with the lithium supplement and the dopant comprises at least one of the following features:

[0026] Feature 12: the lithium supplement is supplemented in a molar ratio of lithium metal to transition metal in the first mixture of 1.03:1 to 1.06:1;

[0027] Feature 13: the doping element in the dopant comprises at least one of Zr, Mg, Nb and Ta;

[0028] Feature 14: the amount of the doping element in the dopant is 500-5000 ppm, preferably 1000-4500 ppm, of the dried material;

[0029] Feature 15: the mixing speed of the dried material with the lithium supplement and the dopant is 600-1000 rpm, the mixing time is 30-60 min, and the mixing temperature is not higher than 50°C.

[0030] In optional embodiments, the first sintering is carried out at 780-850°C for 3-6 h, and then the temperature is lowered to 700-760°C for 8-15 h.

[0031] In optional embodiments, the heating rate during the first sintering is 2-10°C / min.

[0032] In optional embodiments, the first sintering is carried out under an oxygen atmosphere.

[0033] In optional embodiments, the mixing of the positive electrode base material with the coating agent comprises at least one of the following features:

[0034] Feature 16: The coating elements in the coating agent include at least one of B and W;

[0035] Feature 17: The amount of the coating elements in the coating agent is 500ppm-3500ppm of the positive electrode matrix material, preferably 1000ppm-2000ppm;

[0036] Feature 18: The mixing speed of the positive electrode matrix material and the coating agent is 600rpm-1000rpm, the mixing time is 15min-35min, and the mixing temperature is not more than 50℃.

[0037] In an optional embodiment, the second sintering is a heat treatment at 280℃-460℃ for 6h-10h.

[0038] In an optional embodiment, the heating rate during the second sintering is 2℃ / min-10℃ / min.

[0039] In an optional embodiment, the second sintering is performed in an oxygen atmosphere and / or an air atmosphere.

[0040] In a second aspect, the present application provides a high-nickel single-crystal ternary positive electrode material prepared by the preparation method of any one of the preceding embodiments.

[0041] In a third aspect, the present application provides a battery comprising the high-nickel single-crystal ternary positive electrode material of the preceding embodiments.

[0042] The beneficial effects of the present application include:

[0043] The present application can reduce the Li + / Ni 2+ cations mixing, repair the damage to the material surface structure caused by the water washing during the sintering process, improve the integrity of the material surface structure, and prepare a high-nickel single-crystal ternary positive electrode material with low residual alkali and long cycle effect by combining doping and coating. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0045] Figure 1 SEM image of the high-nickel single-crystal ternary positive electrode material prepared in Example 1 of the present application;

[0046] Figure 2 The charge-discharge cycle performance chart of the high-nickel single-crystal ternary positive electrode material of Example 1 and the ternary positive electrode material of Comparative Example 1 was prepared after the materials were prepared into a coin cell at 45℃. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. If specific conditions are not specified in the embodiments, the conditions are implemented according to conventional conditions or the conditions recommended by the manufacturer. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0048] The high-nickel single-crystal ternary positive electrode material provided by the present application and the preparation method and application thereof will be described in detail below.

[0049] The present application provides a preparation method of a high-nickel single-crystal ternary positive electrode material, comprising the following steps: mixing a ternary precursor and a lithium source and then pre-sintering to obtain pre-sintered material; washing the pre-sintered material with water and drying to obtain dried material; mixing the dried material with a lithium supplement source and a dopant to obtain first mixed material; first sintering the first mixed material to obtain positive electrode matrix material; mixing the positive electrode matrix material with a coating agent to obtain second mixed material; and second sintering the second mixed material to obtain the high-nickel single-crystal ternary positive electrode material.

[0050] The present application can reduce the Li + / Ni 2+ cations mixed arrangement by increasing the water washing process after pre-sintering, supplementing a small amount of lithium for gradient sintering after reducing the residual alkali of the pre-sintered material to a low level, repairing the damage to the material surface structure caused by water washing during the sintering process, improving the integrity of the material surface structure, and combining doping and coating to prepare a high-nickel single-crystal ternary positive electrode material with low residual alkali and long cycle effect.

[0051] In some optional embodiments, the molecular formula of the ternary precursor is Ni x Co y Mn 1-x-y (OH)2, wherein 0.90≤x≤0.97 and 0.02≤y<0.06.

[0052] The median particle size of the ternary precursor can be 3 μm to 4 μm, such as 3 μm, 3.5 μm or 4 μm, or other values within the range of 3 μm to 4 μm.

[0053] The specific surface area of the ternary precursor can be 8 m 2 / g to 15 m 2 / g, such as 8 m 2 / g, 9 m2 / g, 10 m 2 / g, 11 m 2 / g, 12 m 2 / g, 13 m 2 / g, 14 m 2 / g or 15 m 2 / g, etc., or 8 m 2 / g~15 m 2 / g in the range of 8 m~15 m.

[0054] In some optional embodiments, the lithium source can exemplarily include at least one of lithium carbonate, lithium hydroxide, lithium nitrate, lithium dihydrogen phosphate, and lithium acetate. In some preferable embodiments, the lithium source includes lithium hydroxide.

[0055] In some optional embodiments, the molar ratio of Li in the lithium source to the transition metal element in the ternary precursor can be 0.7:1~1.03:1, such as 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.01:1, 1.02:1, or 1.03:1, etc., or other values in the range of 0.7:1~1.03:1. In some preferable embodiments, the molar ratio of Li in the lithium source to the transition metal element in the ternary precursor is 0.8:1~1.01:1.

[0056] In some optional embodiments, the mixing speed of the ternary precursor and the lithium source can be 200 rpm~800 rpm, such as 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, or 800 rpm, etc., or other values in the range of 200 rpm~800 rpm. The mixing time can be 30 min~60 min, such as 30 min, 40 min, 50 min, or 60 min, etc., or other values in the range of 30 min~60 min. The mixing temperature is not more than 50℃, such as 25℃~45℃.

[0057] In some optional embodiments, the pre-sintering can be performed at a temperature of 450℃~650℃ (such as 450℃, 500℃, 550℃, 600℃, or 650℃, etc.) for 4 h~6 h (such as 4 h, 4.5 h, 5 h, 5.5 h, or 6 h, etc.). The temperature rising rate in the above pre-sintering process can be 2℃ / min~10℃ / min, such as 2℃ / min, 5℃ / min, 8℃ / min, or 10℃ / min, etc. The above pre-sintering process can be performed in an oxygen atmosphere.

[0058] If the temperature of the pre-sintering is lower than 450℃, it is not conducive to the dehydration of the precursor and the lithium source, affecting the loading amount of the primary sintering; if the temperature of the pre-sintering is higher than 650℃, the material is too hard to be clumped, which is not conducive to the subsequent water washing.

[0059] In some alternative embodiments, the temperature of the water used for washing can be between 5°C and 12°C, such as 5°C, 6°C, 7°C, 8°C, 9°C, 10°C, 11°C, or 12°C, or other values ​​within the range of 5°C to 12°C. The water used is preferably deionized water.

[0060] If the temperature of the water used for washing is higher than 12℃, it will not be conducive to the removal of lithium carbonate during the washing process.

[0061] The solid-liquid ratio for water washing can be from 1:2 to 1:0.5, such as 1:2, 1:1.8, 1:1.5, 1:1.2, 1:1, 1:0.8, or 1:0.5, or other values ​​within the range of 1:2 to 1:0.5. In some preferred embodiments, the solid-liquid ratio for water washing is from 1:1.2 to 1:0.8.

[0062] If too much water is used during the washing process, the Li on the material surface will... + Severe precipitation damages the surface structure of the material, increasing the difficulty of subsequent sintering repair and also increasing the amount of lithium source to be added, which is uneconomical. If the amount of water during the washing process is too small, the residual alkali on the material surface is difficult to remove effectively, and the residual alkali in subsequent sintering is difficult to control at a low level.

[0063] The washing time can be from 2 minutes to 10 minutes, such as 2 minutes, 5 minutes, 8 minutes, or 10 minutes, or other values ​​within the range of 2 minutes to 10 minutes. In some preferred embodiments, the washing time is 2 minutes to 5 minutes.

[0064] The above-mentioned water washing process can be carried out under a protective atmosphere, such as a nitrogen atmosphere and / or an argon atmosphere.

[0065] In some alternative embodiments, the drying temperature can be 100℃ to 160℃, such as 100℃, 110℃, 120℃, 130℃, 140℃, 150℃ or 160℃, or other values ​​within the range of 100℃ to 160℃.

[0066] The drying time can be 5h to 10h, such as 5h, 6h, 7h, 8h, 9h or 10h, or it can be 5h to 10h.

[0067] In some optional embodiments, the amount of LiOH in the above-mentioned dried material does not exceed 0.26 wt%, and the amount of Li2CO3 does not exceed 0.32 wt%.

[0068] As described above, the mixture of the precursor and the lithium source is pre-sintered to pre-lithiate and dehydrate, and then the pre-sintered material is washed with water, which greatly reduces the residual alkali on the surface of the pre-sintered material, and also reduces the content of impurity elements such as Na and S brought by the precursor, the lithium source and other raw materials, which is beneficial to the crystallization growth of the material in the subsequent formal sintering process and improves the crystallinity of the material.

[0069] In some optional embodiments, the lithium source can be supplemented at a molar ratio of lithium metal to transition metal in the first mixture of 1.03:1 to 1.06:1 (such as 1.03:1, 1.04:1, 1.05:1 or 1.06:1, etc.).

[0070] The doping elements in the dopant can exemplarily include at least one of Zr, Mg, Nb and Ta. Among them, Zr can be exemplarily provided by ZrO2, Mg can be exemplarily provided by Mg(OH)2, Nb can be exemplarily provided by Nb2O5, and Ta can be exemplarily provided by Ta2O5.

[0071] The amount of the doping elements in the dopant can be 500 ppm to 5000 ppm of the dry material, such as 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm or 5000 ppm, etc., or other values within the range of 500 ppm to 5000 ppm. In some preferred embodiments, the amount of the doping elements in the dopant is 1000 ppm to 4500 ppm of the dry material.

[0072] In some optional embodiments, the mixing speed of the dry material with the supplemental lithium source and the dopant can be 600 rpm to 1000 rpm, such as 600 rpm, 700 rpm, 800 rpm, 900 rpm or 1000 rpm, etc., or other values within the range of 600 rpm to 1000 rpm. The mixing time can be 30 min to 60 min, such as 30 min, 40 min, 50 min or 60 min, etc., or other values within the range of 30 min to 60 min. The mixing temperature is not more than 50°C, such as 20°C to 45°C.

[0073] In some optional embodiments, the first sintering can be performed at a temperature of 780°C to 850°C (such as 780°C, 800°C, 820°C or 850°C, etc.) for 3 h to 6 h (such as 3 h, 4 h, 5 h or 6 h, etc.), and then cooled to a temperature of 700°C to 760°C (such as 700°C, 710°C, 720°C, 730°C, 740°C, 750°C or 760°C, etc.) for 8 h to 15 h (such as 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h or 15 h, etc.).

[0074] The heating rate in the first sintering process can be 2-10℃ / min, such as 2℃ / min, 5℃ / min, 8℃ / min or 10℃ / min, etc. The first sintering process can be carried out in an oxygen atmosphere.

[0075] In some alternative embodiments, the amount of LiOH in the positive electrode matrix material is not more than 0.29wt%, and the amount of Li2CO3 is not more than 0.4wt%.

[0076] In some alternative embodiments, the coating element in the coating agent can exemplarily include at least one of B and W. B can be provided by boric acid, and W can be provided by tungstic acid.

[0077] The present application can form a coating layer of lithium borate, lithium tungstate, etc. by using boric acid and / or tungstic acid to coat the surface of the positive electrode matrix material. These coating layers can not only reduce the corrosion of HF on the positive electrode matrix material and reduce the dissolution of transition metals, but also effectively reduce the side reaction between the electrode material and the electrolyte. The coating agent will also react with the residual alkali on the surface of the material to generate fast ion conductors such as lithium borate and lithium tungstate during sintering, further reducing the residual alkali and improving the lithium ion conduction performance of the material surface, thereby improving the rate performance and cycle performance of the positive electrode material.

[0078] The amount of coating element in the coating agent can be 500-3500ppm of the positive electrode matrix material, such as 500ppm, 1000ppm, 1500ppm, 2000ppm, 2500ppm, 3000ppm or 3500ppm, etc. It can also be other values within the range of 500-3500ppm. In some preferred embodiments, the amount of coating element in the coating agent is 1000-2000ppm of the positive electrode matrix material.

[0079] In some alternative embodiments, the mixing speed of the positive electrode matrix material and the coating agent is 600-1000rpm, such as 600rpm, 700rpm, 800rpm, 900rpm or 1000rpm, etc. It can also be other values within the range of 600-1000rpm. The mixing time can be 15-35min, such as 15min, 20min, 25min, 30min or 35min, etc. It can also be other values within the range of 15-35min. The mixing temperature is not more than 50℃, such as 20-45℃.

[0080] In some alternative embodiments, the second sintering can be performed at 280-460°C (e.g., 280°C, 300°C, 350°C, 380°C, 400°C, 420°C, 450°C or 460°C, etc.) for 6-10 hours (e.g., 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, etc.).

[0081] If the temperature of the second sintering is lower than 280°C, the melting and diffusion of boric acid is insufficient, the coating layer is uneven and not dense, and the effect is not good. If the temperature of the second sintering is higher than 460°C, the volatility of B2O3 is enhanced, which can lead to loss of the coating layer.

[0082] The heating rate during the second sintering described above can be 2-10°C / min, such as 2°C / min, 5°C / min, 8°C / min or 10°C / min, etc. The second sintering described above can be performed in an oxygen atmosphere and / or an air atmosphere.

[0083] In some alternative embodiments, the amount of LiOH in the high-nickel single-crystal ternary positive electrode material described above is not more than 0.29wt%, and the amount of Li2CO3 is not more than 0.4wt%.

[0084] The pre-sintered material after washing is subjected to gradient sintering in the present application. First, the pre-sintered material after washing is reacted with the second added lithium source (i.e., the lithium supplement) at a high temperature for a short time, so as to promote the rapid fusion and growth of the primary particles. Then, the crystal continues to grow at a medium temperature lower than the high temperature for a long time. The gradient sintering not only reduces the exposure time of the material at a high temperature, but also effectively reduces the formation of Ni 2+ . The long-time preservation at a lower temperature promotes the re-oxidation of Ni 2+ , thereby reducing the Li + / Ni 2+ cationic disordering of the material. Moreover, the gradient sintering process can also repair the damage to the surface structure of the material caused by the washing process of the pre-sintered material, improve the integrity of the surface structure of the material, and improve the capacity of the material. In addition, the doping agent nano-zirconium oxide, magnesium hydroxide, etc. is added during the gradient sintering, the doping elements replace the lithium sites or transition metal sites of the material, which can stabilize the crystal structure during the charging and discharging process, increase the oxygen vacancy formation energy, and inhibit the generation of micro-cracks, thereby improving the cycle stability and thermal stability of the material.

[0085] As described above, the preparation method of the high-nickel single-crystal ternary positive electrode material provided by the present application can significantly reduce the surface residual alkali of the high-nickel single-crystal ternary positive electrode material without affecting or even improving the electrochemical performance of the material. The main method is to reduce the residual alkali of the material by using the washing process and surface modification, and to reduce the Li + / Ni 2+The cations are mixed and arranged, the structural stability of the material is improved, and thus the capacity and cycle performance of the material are improved.

[0086] Correspondingly, the application further provides a high-nickel single-crystal ternary positive electrode material prepared by the above preparation method.

[0087] The molecular formula of the high-nickel single-crystal ternary positive electrode material is LiNi x Co y Mn 1-x-y O2, wherein 0.90≤x≤0.97 and 0.02≤y<0.06.

[0088] In some optional embodiments, the average size of the primary particles of the high-nickel single-crystal ternary positive electrode material is about 1.8 μm.

[0089] In addition, the application further provides a battery comprising the high-nickel single-crystal ternary positive electrode material.

[0090] The features and performances of the application are further described in detail below in combination with embodiments.

[0091] Embodiment 1

[0092] The embodiment provides a high-nickel single-crystal ternary positive electrode material, and a preparation method thereof comprises the following steps:

[0093] S1: mixing a ternary precursor and a lithium source in a high-speed mixer, then loading into a sagger and placing in a box furnace for pre-sintering, cooling, and dispersing by a high-speed mixer to obtain pre-sintered material.

[0094] The ternary precursor has a median particle size of 3.0 μm, a specific surface area of 11 m 2 / g, and a Ni 0.93 Co 0.04 Mn 0.03 (OH)2; the lithium source is battery-grade lithium hydroxide; the molar ratio of Li in the lithium source to transition metal elements (Ni+Co+Mn) in the ternary precursor is 1.0:1. The rotation speed of the high-speed mixer is 300 rpm, the mixing time is 45 min, and the mixing temperature is 25℃-45℃. The pre-sintering is performed under an oxygen atmosphere at 550℃ for 6 h, and the temperature rising rate during the pre-sintering is 3℃ / min.

[0095] S2: washing and drying the pre-sintered material to obtain dried material.

[0096] The pre-sintered material is washed with 10℃ deionized water at a solid-liquid ratio of 1 mg:1 mL, the washing is stirred for 3 min, then pressure filtration is performed, and vacuum drying is performed under a nitrogen atmosphere, the drying temperature is 150℃, and the drying time is 10 h.

[0097] S3: mixing the dried material with a lithium supplement and a dopant to obtain a first mixture.

[0098] The nanoscale zirconium oxide and the magnesium hydroxide, each in a mass percentage of 2500ppm and 1000ppm of the dried material, were weighed as dopants; the required battery-grade lithium hydroxide was calculated and weighed as a lithium supplement according to a lithium-to-transition metal (Ni+Co+Mn) molar ratio of 1.05:1 in the first mixture; the lithium supplement and the dopants were sequentially added to the dried material, and a high-speed mixer was used to mix them uniformly at a speed of 1000rpm for 30min at a temperature of 20-45℃ to obtain the first mixture.

[0099] S4: performing first sintering on the first mixture to obtain a positive electrode matrix material.

[0100] The first mixture was loaded into a sagger and placed in a box furnace, and was first heated to 820℃ at a rate of 3℃ / min under an oxygen atmosphere, and then cooled to 730℃, sintered for 12h, and then cooled, crushed, rolled, and crushed to obtain the positive electrode matrix material.

[0101] S5: mixing the positive electrode matrix material with a coating agent to obtain a second mixture.

[0102] The boric acid, in a mass percentage of 1500ppm of the positive electrode matrix material, was weighed as a coating agent, added to the positive electrode matrix material, and mixed uniformly using a high-speed mixer at a speed of 900rpm for 30min at a temperature of 20-45℃ to obtain the second mixture.

[0103] S6: performing second sintering on the second mixture to obtain a high-nickel single-crystal ternary positive electrode material.

[0104] The second mixture was loaded into a sagger and placed in a box furnace, and was heated to 300℃ at a rate of 3℃ / min under an oxygen atmosphere, sintered for 10h, and then cooled, sieved, and obtained as the high-nickel single-crystal ternary positive electrode material.

[0105] Example 2

[0106] The difference between this example and Example 1 is that the solid-liquid ratio of the water washing is 1mg:0.8mL.

[0107] Example 3

[0108] The difference between this example and Example 1 is that the molar ratio of Li in the lithium source to the transition metal elements in the ternary precursor is 0.8:1.

[0109] Example 4

[0110] The difference between the embodiment and embodiment 1 is that the molar ratio of Li in the lithium source to transition metal elements in the ternary precursor is 1.02:1.

[0111] Embodiment 5

[0112] The difference between the embodiment and embodiment 1 is that the dopant is 2500 ppm of nano-sized zirconium oxide and 500 ppm of niobium oxide.

[0113] Embodiment 6

[0114] The difference between the embodiment and embodiment 1 is that the coating agent is 1500 ppm of boric acid and 500 ppm of tungstic acid.

[0115] Embodiment 7

[0116] The embodiment provides a high-nickel single-crystal ternary positive electrode material, and a preparation method thereof.

[0117] S1: The ternary precursor and the lithium source are mixed in a high-speed mixer, and then loaded into a sagger and placed in a box furnace for pre-sintering, cooling, and dispersion by a high-speed mixer to obtain pre-sintered material.

[0118] The ternary precursor has a median particle size of 3.5 μm, a specific surface area of 8 m 2 / g, and the lithium source is battery-grade lithium acetate. 0.97 Co 0.02 Mn 0.01 (OH)2; the lithium source is battery-grade lithium acetate; the molar ratio of Li in the lithium source to transition metal elements (Ni+Co+Mn) in the ternary precursor is 0.7:1. The rotation speed of the high-speed mixer is 200 rpm, the mixing time is 60 min, and the mixing temperature is 25℃-45℃. The pre-sintering is performed under an oxygen atmosphere at 450℃ for 5 h, and the temperature rising rate during the pre-sintering is 2℃ / min.

[0119] S2: The pre-sintered material is washed with water and dried to obtain dried material.

[0120] The pre-sintered material is washed with 5℃ deionized water at a solid-liquid ratio of 1 mg:2 mL, stirred for 10 min, filtered under pressure, and dried in a vacuum atmosphere under the protection of nitrogen, with a drying temperature of 100℃ and a drying time of 8 h.

[0121] S3: The dried material is mixed with a lithium supplement and a dopant to obtain first mixed material.

[0122] Take 1500 ppm of the dry material as zirconium oxide nanoparticles and 500 ppm of the dry material as diniobium pentoxide as dopants, respectively, in terms of mass percentage; then, according to the molar ratio of lithium to transition metals (Ni+Co+Mn) in the first mixture being 1.03:1, calculate and take the required lithium hydroxide as a supplement lithium source; add the supplement lithium source and the dopants to the dry material in turn, mix uniformly using a high-speed mixer, the speed of the high-speed mixer being 600 rpm, the mixing time being 60 min, and the mixing temperature being 20-45℃, to obtain the first mixture.

[0123] S4: Perform first sintering on the first mixture to obtain the positive electrode matrix material.

[0124] Put the first mixture into a sagger and place it in a box furnace, first heat it to 780℃ at a rate of 2℃ / min in an oxygen atmosphere, keep it sintered for 6h, then cool it to 700℃, keep it sintered for 15h, then cool it down, crush it, roll it, and crush it to obtain the positive electrode matrix material.

[0125] S5: Mix the positive electrode matrix material with the coating agent to obtain the second mixture.

[0126] Take 1000 ppm of tungstic acid as the coating agent based on the mass of the positive electrode matrix material, add it to the positive electrode matrix material, mix uniformly using a high-speed mixer, the speed of the high-speed mixer being 600 rpm, the mixing time being 35 min, and the mixing temperature being 20-45℃, to obtain the second mixture.

[0127] S6: Perform second sintering on the second mixture to obtain the high-nickel single-crystal ternary positive electrode material.

[0128] Put the second mixture into a sagger and place it in a box furnace, heat it to 280℃ at a rate of 2℃ / min in an oxygen atmosphere, keep it sintered for 10h, then cool it down, sieve it, to obtain the high-nickel single-crystal ternary positive electrode material.

[0129] Example 8

[0130] The present embodiment provides a high-nickel single-crystal ternary positive electrode material, and a preparation method thereof.

[0131] S1: Mix the ternary precursor and the lithium source in a high-speed mixer, then put it into a sagger and place it in a box furnace for pre-sintering, cool it down, disperse it using a high-speed mixer, to obtain the pre-sintered material.

[0132] The ternary precursor has a median particle size of 4.0 μm and a specific surface area of 15 m 2 / g. 0.90 Co 0.05 Mn 0.05The lithium source is battery-grade lithium dihydrogen phosphate, and the molar ratio of Li in the lithium source to the transition metal elements (Ni+Co+Mn) in the ternary precursor is 1.03:1. The high-speed mixer rotates at 800 rpm, the mixing time is 30 min, and the mixing temperature is 25-45°C. The pre-sintering is performed under an oxygen atmosphere at 650°C for 4 h, and the temperature rising rate during the pre-sintering is 10°C / min.

[0133] S2: The pre-sintered material is washed with water and dried to obtain a dried material.

[0134] The pre-sintered material is washed with 12°C deionized water at a solid-liquid ratio of 1 mg:0.5 mL, the washing and stirring are performed for 2 min, then the material is pressed and filtered, and vacuum drying is performed under a nitrogen atmosphere, the drying temperature is 160°C, and the drying time is 5 h.

[0135] S3: The dried material is mixed with a lithium supplement and a dopant to obtain a first mixed material.

[0136] The zirconium oxide nanoparticles and the tantalum pentoxide are respectively taken as the dopants, accounting for 2500 ppm and 500 ppm of the dried material by mass percentage; the required battery-grade lithium hydroxide is calculated and taken as the lithium supplement according to the molar ratio of lithium to transition metal (Ni+Co+Mn) in the first mixed material, which is 1.06:1; the lithium supplement and the dopants are sequentially added to the dried material, and the high-speed mixer is used for uniform mixing, the high-speed mixer rotates at 1000 rpm, the mixing time is 30 min, and the mixing temperature is 20-45°C, to obtain the first mixed material.

[0137] S4: The first mixed material is subjected to first sintering to obtain a positive electrode matrix material.

[0138] The first mixed material is loaded into a sagger and placed in a box furnace, the temperature is first raised to 850°C at a rate of 10°C / min under an oxygen atmosphere, the temperature is then lowered to 760°C after sintering for 3 h, the temperature is sintered for 8 h, and then the temperature is lowered and cooled, the sagger is broken, the rollers are rolled, and the material is crushed to obtain the positive electrode matrix material.

[0139] S5: The positive electrode matrix material is mixed with a coating agent to obtain a second mixed material.

[0140] The boric acid and the tungstic acid are taken as the coating agents, accounting for 500 ppm and 2500 ppm of the mass of the positive electrode matrix material, and are added to the positive electrode matrix material, the high-speed mixer is used for uniform mixing, the high-speed mixer rotates at 1000 rpm, the mixing time is 15 min, and the mixing temperature is 20-45°C, to obtain the second mixed material.

[0141] S6: The second mixed material is subjected to second sintering to obtain a high-nickel single-crystal ternary positive electrode material.

[0142] The second mixture was loaded into a sagger and placed in a box furnace. Under air atmosphere, the temperature was raised to 460°C at a rate of 10°C / min, and sintered at that temperature for 6 hours. Then, the mixture was cooled and sieved to obtain a high-nickel single-crystal ternary cathode material.

[0143] Comparative Example 1

[0144] The difference between this comparative example and Example 1 is that the pre-calcined material is not washed with water.

[0145] Comparative Example 2

[0146] The difference between this comparative example and Example 1 is that the solid-liquid ratio of the water wash is 2 mg: 1 mL.

[0147] Comparative Example 3

[0148] The difference between this comparative example and Example 1 is that the solid-liquid ratio of the water wash is 1 mg: 3 mL.

[0149] Comparative Example 4

[0150] The difference between this comparative example and Example 1 is that the first sintering is only a single-stage sintering, specifically, it is a warm sintering for 12 hours after the temperature is raised to 820°C.

[0151] Comparative Example 5

[0152] The difference between this comparative example and Example 1 is that no coating agent was used.

[0153] Comparative Example 6

[0154] The difference between this comparative example and Example 1 is that no pre-sintering was performed.

[0155] Comparative Example 7

[0156] The difference between this comparative example and Example 1 is that no dopant was used.

[0157] Comparative Example 8

[0158] The difference between this comparative example and Example 1 is that the coating agent is 300 ppm titanium dioxide and 200 ppm magnesium oxide.

[0159] Experimental Example 1

[0160] The structure of the high-nickel single-crystal ternary cathode material prepared in Example 1 was observed, and the results are as follows: Figure 1 As shown, by Figure 1 It can be seen that the average size of the primary particles of this high-nickel single-crystal ternary cathode material is about 1.8 μm.

[0161] Experimental Example 2

[0162] (1) The dry material, positive electrode matrix material and high-nickel single-crystal ternary positive electrode material of Examples 1-8 and Comparative Examples 1-8 were tested for residual alkali by potential titration, and the results of residual alkali are shown in Table 1.

[0163] Table 1 Process material and product residual alkali results

[0164]

[0165] As can be seen from Table 1, compared with Comparative Example 1, the residual alkali of the high-nickel single-crystal ternary positive electrode material prepared in each of the examples of the present application is significantly improved, and the LiOH and Li2CO3 of the high-nickel single-crystal ternary positive electrode material in Example 1 are both reduced to a low level, indicating that the method of pre-sintering material washing combined with surface coating effectively reduces the surface residual alkali of the high-nickel single-crystal ternary positive electrode material, which is beneficial to improve the electrical properties of the material and improve the processing performance.

[0166] (2) The high-nickel single-crystal ternary positive electrode materials prepared in Examples 1-8 and Comparative Examples 1-8 were used as battery positive electrode materials to make button cells for electrochemical performance testing.

[0167] The preparation method is as follows:

[0168] a. Each high-nickel single-crystal positive electrode material was stirred according to the ratio of positive electrode material powder: conductive agent (SP): adhesive (PVDF) = 90:5:5 to form a uniformly dispersed positive electrode slurry, and the slurry was coated, punched, and vacuum dried; lithium metal was used as the negative electrode material of the counter electrode, and a microporous polypropylene film was used as the battery separator; 1:1 volume ratio of ethylene carbonate (EC) / dimethyl carbonate (DMC), 1 mol / L LiPF6 as the electrolyte, assembled into a 2032 type button cell in a glove box filled with dry and high-purity argon and left for 8 h;

[0169] b. The button cell after standing was charged and discharged at 0.1C rate current at ambient temperature 25℃, 3.0V-4.3V to test the electrochemical performance, and the first discharge efficiency was calculated, i.e. first efficiency = first discharge specific capacity / first charge specific capacity x 100%.

[0170] c. The cycle performance test was carried out at 45℃, 3.0V-4.3V with 1C charge / 1C discharge, and the capacity retention rate after 50 cycles was calculated, the formula is as follows: capacity retention rate = 50th discharge specific capacity / first discharge specific capacity x 100%.

[0171] The test results are shown in Table 2 and Figure 2 .

[0172] Table 2 Electrochemical performance test results

[0173]

[0174]

[0175] From Table 2, compared with Comparative Example 1, the high-nickel single-crystal ternary positive electrode material prepared by each embodiment of the present application has obvious improvement in the initial efficiency, discharge specific capacity and high-temperature cycle stability of the battery after further preparation into a battery. It is shown that the method provided by the present application can effectively improve the initial efficiency of the material and improve the charge-discharge performance of the material; at the same time, the material also exhibits good cycle performance at high temperature 45℃ and 1C rate. It can be found by comparing Comparative Example 1 with Comparative Examples 1, 4 and 5 that, after water washing of the pre-sintered material, the pre-sintered material is subjected to gradient sintering by high temperature for a short time and then by medium temperature for a long time, combined with the addition of lithium source and dopant, the layered structure of the positive electrode matrix material is obviously improved, and after coating with boric acid, the discharge capacity and cycle of the material are greatly improved.

[0176] The reasons for the effects achieved by the above embodiments are as follows. First, the combination of the addition of secondary lithium source and gradient sintering effectively repairs the lithium-poor rock salt phase on the surface of the material after water washing, and the addition of nano-zirconium oxide, magnesium hydroxide and other dopants stabilizes the crystal structure, increases the oxygen vacancy formation energy and inhibits the generation of micro-cracks, thereby improving the discharge capacity and cycle stability of the material. In addition, the reaction of boric acid, tungstic acid and residual lithium of the matrix material forms a fast ion conductor coating layer, which further reduces the surface residual alkali and reduces the corrosion of HF on the material, reduces the transition metal dissolution, effectively reduces the side reaction between the electrode material and the electrolyte, and makes the high-nickel single-crystal ternary positive electrode material obtained by Example 1 of the present application have very excellent electrochemical performance.

[0177] In summary, by adding a water washing process after pre-sintering, reducing the residual alkali of the pre-sintered material to a low level and then adding a small amount of lithium for gradient sintering, the present application not only reduces the Li + / Ni 2+ cation mixing, but also repairs the damage to the surface layer structure of the material caused by water washing during the sintering process, improves the integrity of the surface layer structure of the material, and combines doping and coating to prepare a high-nickel single-crystal ternary positive electrode material with low residual alkali and long cycle effect.

[0178] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a high-nickel single-crystal ternary cathode material, characterized in that, Includes the following steps: The ternary precursor is mixed with a lithium source and then pre-sintered to obtain a pre-sintered material; The pre-calcined material is washed with water and dried to obtain a dried material; The dried material is mixed with a supplementary lithium source and a dopant to obtain a first mixture; the first mixture is sintered for the first time to obtain a cathode substrate material; the cathode substrate material is mixed with a coating agent to obtain a second mixture; the second mixture is sintered for the second time to obtain a high-nickel single-crystal ternary cathode material.

2. The preparation method according to claim 1, characterized in that, The ternary precursor mixed with the lithium source includes at least one of the following characteristics: Feature 1: The molecular formula of the ternary precursor is Ni x Co y Mn 1-x-y (OH)2, where 0.90≤x≤0.97, 0.02≤y<0.06; Feature 2: The median particle size of the ternary precursor is 3 μm to 4 μm; Feature 3: The specific surface area of ​​the ternary precursor is 8m². 2 / g~15m 2 / g; Feature 4: The lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate, lithium dihydrogen phosphate, and lithium acetate, preferably lithium hydroxide; Feature 5: The molar ratio of Li in the lithium source to the transition metal element in the ternary precursor is 0.7:1 to 1.03:1, preferably 0.8:1 to 1.01:1; Feature 6: The mixing speed of the ternary precursor and the lithium source is 200 rpm to 800 rpm, the mixing time is 30 min to 60 min, and the mixing temperature does not exceed 50℃.

3. The preparation method according to claim 1, characterized in that, Pre-sintering is carried out at 450℃~650℃ for 4h~6h; Preferably, the heating rate during the pre-sintering process is 2℃ / min to 10℃ / min; Preferably, the pre-sintering is carried out in an oxygen atmosphere.

4. The preparation method according to claim 1, characterized in that, Washing and drying include at least one of the following characteristics: Feature 7: The temperature of the water used for washing is 5℃~12℃; Feature 8: The solid-liquid ratio of the water wash is 1:2 to 1:0.5, preferably 1:1.2 to 1:0.8; Feature 9: The washing time is 2 min to 10 min, preferably 2 min to 5 min; feature 10: The water washing is carried out under a protective atmosphere; preferably, the protective atmosphere is a nitrogen atmosphere and / or an argon atmosphere; Feature 11: Drying temperature is 100℃~160℃, and drying time is 5h~10h.

5. The preparation method according to claim 1, characterized in that, The mixture of the dried material with the supplementary lithium source and the dopant includes at least one of the following characteristics: Feature 12: The supplementary lithium source is added according to a molar ratio of lithium metal to transition metal in the first mixture of 1.03:1 to 1.06:1; Feature 13: The doping element in the dopant includes at least one of Zr, Mg, Nb and Ta; Feature 14: The amount of dopant element in the dopant is 500ppm to 5000ppm of the dried material, preferably 1000ppm to 4500ppm; Feature 15: The mixing speed of the dried material, the supplementary lithium source, and the dopant is 600 rpm to 1000 rpm, the mixing time is 30 min to 60 min, and the mixing temperature does not exceed 50°C.

6. The preparation method according to claim 1, characterized in that, The first sintering is to hold at 780℃~850℃ for 3h~6h, and then cool down to 700℃~760℃ and hold for 8h~15h. Preferably, the heating rate during the first sintering process is 2℃ / min to 10℃ / min; Preferably, the first sintering is carried out in an oxygen atmosphere.

7. The preparation method according to claim 1, characterized in that, The mixture of the positive electrode matrix material and the coating agent includes at least one of the following characteristics: Feature 16: The coating element in the coating agent includes at least one of B and W; Feature 17: The amount of coating elements in the coating agent is 500ppm to 3500ppm of the positive electrode matrix material, preferably 1000ppm to 2000ppm; Feature 18: The mixing speed of the positive electrode substrate material and the coating agent is 600 rpm to 1000 rpm, the mixing time is 15 min to 35 min, and the mixing temperature does not exceed 50℃.

8. The preparation method according to claim 1, characterized in that, The second sintering is a heat treatment at 280℃~460℃ for 6h~10h; Preferably, the heating rate during the second sintering process is 2℃ / min to 10℃ / min; Preferably, the second sintering is carried out in an oxygen atmosphere and / or an air atmosphere.

9. A high-nickel single-crystal ternary cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

10. A battery, characterized in that, Including the high-nickel single-crystal ternary cathode material as described in claim 9.

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