Preparation method of Ta / Se double-coated nickel-cobalt-manganese ternary lithium ion battery positive electrode material

Abstract

The application discloses a preparation method of Ta / Se double-coated nickel-cobalt-manganese ternary lithium ion battery positive electrode material. The method comprises the following steps: mixing a F-containing compound, a nickel-cobalt-manganese composite precursor and a lithium source, and firing at three different temperature stages to obtain a doped matrix; then mixing and firing with a Ta source to obtain Ta-coated positive electrode material, and mixing with deionized water, and drying; then mixing and firing with a Se source to obtain Ta / Se double-coated nickel-cobalt-manganese ternary lithium ion battery positive electrode material. A small amount of F ion doping is adopted in the positive electrode material to improve the rate, cycle performance and structural stability. Ta / Se co-coating can inhibit the decomposition of electrolyte and the corrosion of by-products on the positive electrode material, improve the structural stability of the material, accelerate the diffusion of Li + in the battery cycle process, reduce the swelling and consumption of lithium ions, and improve the rate and cycle performance of high-nickel materials.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a lithium-ion battery cathode material, and more specifically to a method for modifying a lithium-ion battery cathode material. Background Technology

[0002] Ternary layered lithium-ion battery cathode materials are widely used in the new energy vehicle field due to their relatively low cost, superior reversible energy density, and rate performance. However, increasing the Ni content in the material can compromise its structural stability. This leads to the formation of highly active Ni during charging. 4+ The reaction with the electrolyte produces a NiO rock salt phase, severely damaging the structure of the layered material and causing the cathode material structure to collapse. This, in turn, induces the dissolution of transition metal ions, phase transitions, and lattice oxygen evolution, posing a significant threat to the material's cycle life and safety. To address these issues, CN201610416709.9 proposes doping lithium nickel cobalt manganese oxide with small amounts of aluminum and fluorine. Al doping can prevent NiO from reacting with the electrolyte. 2+ Replace Li + F doping partially replaces O to improve the structural stability of the cathode material and enhance the reversible insertion / extraction capability of lithium ions, thus improving the material's cycle performance. However, without a coating layer, the doping process alone cannot effectively prevent side reactions between the electrolyte and the cathode material during cycling, failing to guarantee the structural stability of the cathode material during cycling. CN201811596823.X employs Si / Al co-coating. Al coating effectively prevents F anion diffusion, reduces impedance, and inhibits electrolyte decomposition on the coating layer. Si coating improves the material's rate performance. The similar volume of aluminum and silicon ions allows for the formation of a uniform and dense coating layer, thereby improving both the material's cycle stability and rate performance. However, Si / Al co-coating is performed after water washing, which only effectively suppresses side reactions with the electrolyte but cannot effectively address changes in the cathode material's surface or structural failures during the washing process. Summary of the Invention

[0003] This invention provides a method for preparing Ta / Se double-coated nickel-cobalt-manganese ternary lithium-ion battery cathode material. The method improves rate performance, cycle performance, and stability through doping and coating.

[0004] A method for preparing a Ta / Se dual-coated nickel-cobalt-manganese ternary lithium-ion battery cathode material includes the following steps:

[0005] (1) The F-containing compound, the nickel-cobalt-manganese composite precursor (NCM precursor), and the lithium source were added to a high-speed mixer and thoroughly mixed. The mixture was then calcined at three different temperature ranges to obtain the doped matrix.

[0006] (2) the doped substrate and a Ta source are added into a high-speed mixer for mixing and calcination to obtain a Ta-coated positive electrode material, which is then added into deionized water for stirring to obtain uniformity, and drying;

[0007] (3) the product obtained in step (2) and a Se source are added into a high-speed mixer for mixing and calcination to obtain a Ta / Se double-coated nickel-cobalt-manganese ternary lithium ion battery positive electrode material.

[0008] The nickel-cobalt-manganese composite precursor in the application is Ni x Co y Mn 1-x-y (OH)2, wherein 0.5≤x<1, 0.3≤y, 0<y≤0.3.

[0009] The molar amount of F in the application is 0.001%-0.5% of the sum of the molar amounts of nickel, cobalt and manganese elements.

[0010] The F-containing compound in the application is one or more of AlF3, MgF2 and SiF4.

[0011] The amount of lithium source in the application is 0.9-1.1 times of the sum of the molar amounts of nickel, cobalt and manganese elements in terms of Li element.

[0012] The lithium source in the application comprises one or more of lithium hydroxide, lithium carbonate, lithium nitrate and lithium acetate.

[0013] In step (1) of the application, the three different temperature sections for calcination comprise: calcination temperature 1 is 300-500℃, calcination time is 1-4h; calcination temperature 2 is 400-600℃, calcination time is 1-4h; calcination temperature 3 is 700-900℃, calcination time is 8-15h.

[0014] In step (2) of the application, the Ta source is one or more of tantalum tantalate, oxide, boride and nitride of tantalum, and suitable examples include but are not limited to one or more of LiTaO3, Ta2O5, BTa and TaN.

[0015] The coating amount of Ta element in the application is 1000-3000ppm based on the doped substrate obtained in step (1).

[0016] In step (2) of the application, the calcination temperature is 600-800℃, and the calcination time is 6-12h.

[0017] The Se source in the application is one or more of selenium oxide and selenium fluoride, and suitable examples include but are not limited to SeO2 and / or SeF6.

[0018] The coating amount of Se element is 1000-3000 ppm, based on the doped matrix obtained in step (1).

[0019] In step (3) of the present application, the calcination temperature is 200-500 DEG C, and the calcination time is 6-12 h.

[0020] Preferably, the doped matrix obtained in step (1) of the present application has a composition of LiNi x Co y Mn 1-x-y O2, wherein 0.5≤x<1, 0

[0021] The positive electrode material of the present application uses a small amount of F ion doping to improve the rate, cycle performance and structural stability. Because F ion has very strong electronegativity, it can inhibit the overflow of O ion and stabilize the structural stability of the material, and can play a role of skeleton. At the same time, F ion can reduce the driving force of carbonate dehydrogenation on the surface of the oxide, thereby effectively inhibiting the decomposition of the solvent in the electrolyte. The high-nickel positive electrode material maintains the stability of the structure during the cycle process.

[0022] The present application adopts three-stage sintering in the one-time sintering process; during the sintering process of the positive electrode material, lithium salt is decomposed into Li2O, which diffuses from the surface of the nickel-cobalt-manganese metal oxide to the inside and reacts to form a ternary positive electrode material; but part of the Li2O will be retained on the surface of the metal oxide during the diffusion process, and will react with H2O and CO2 in the air to form LiOH and Li2CO3 and remain on the surface of the positive electrode material. When the battery is stored, especially under high temperature conditions, it is easy to react with the electrolyte, and under the corrosion of HF, Co and Ni ions are dissolved, which reduces the cycle life and storage life; from the experimental results, it is found that three-stage sintering can effectively promote more Li2O to enter the inside of the metal oxide particles and react, so that the residual Li2O on the surface is reduced, and the content of LiOH and Li2CO3 on the surface of the positive electrode material is relatively low compared with two-stage sintering, so that the sintered positive electrode material has better processing and storage performance.

[0023] Ta / Se co-coating can inhibit the decomposition of electrolyte and the corrosion of by-products on the positive electrode material, and improve the structural stability of the material; during the cycle process of the battery, it can also accelerate the diffusion of Li + , reduce the swelling and consumption of lithium ions, and improve the rate and cycle performance of high-nickel materials.

[0024] Double-layer coating can more effectively utilize the excellent electrical conductivity of Ta and Se and inhibit the side reaction of the interface with the electrolyte, thereby improving the cycle and rate performance of the material.

[0025] Compared with conventional double-layer coating, the advantages of the coating layer coated with one layer of tantalum before water washing are:

[0026] High nickel positive electrode material surface residual alkali is relatively high, generally by washing to reduce residual alkali; but the positive electrode material surface without coating layer protection will lead to the material surface Li ion excessive dissolution caused by partial surface lithium deficiency, then the corresponding layer structure will lose too much Li ion and begin to transform into NiOOH phase. The chemical properties of NiOOH phase are not stable enough, and it is easy to be further decomposed into inactive rock salt phase NiO by heat, at the same time, it will release part of oxygen in the crystal lattice, metal ion dissolution, and layer structure collapse, which will deteriorate the performance of the positive electrode material. The chemical reaction equations of lithium ion migration and NiOOH thermal decomposition are as follows:

[0027] LiNiO2+H2O---NiOOH+LiOH

[0028] NiOOH---NiO2(rock salt phase)+O2

[0029] The coating layer of a layer of tantalum coated before washing can effectively inhibit the formation of rock salt phase NiO, so that the structure of the positive electrode material is more stable, and the long-term cycle performance is greatly improved.

[0030] The conventional double-layer coating is co-coated after washing, which can only effectively inhibit the side reaction with electrolyte, and cannot effectively solve the change of the positive electrode material surface and the failure of the structure in the washing process. Coating a layer of coating before washing can effectively alleviate this phenomenon. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a comparison chart of cycle retention rate curves of Example 1 and Comparative Example 1 at 1C.

[0032] Figure 2 is a comparison chart of rate performance curves of Example 1 and Comparative Example 1 at different rates.

[0033] Figure 3 is a comparison chart of lithium ion diffusion curves of Example 1 and Comparative Example 1 during charging.

[0034] Figure 4 is a comparison chart of cycle retention rate curves of Example 1 and Comparative Example 2 at 1C.

[0035] Figure 5 is a comparison chart of cycle retention rate curves of Example 1 and Comparative Example 3 at 1C. DETAILED DESCRIPTION

[0036] The following examples will further illustrate the method provided by the present application, but the present application is not limited to the listed examples, and any other known changes within the scope of the claims of the present application should also be included.

[0037] Example 1

[0038] 1) Take 100g of Ni 0.83 Co 0.12 Mn 0.05 (OH)2 precursor, 0.2% doping amount of AlF3(0.061g) is mixed uniformly, and lithium hydroxide and the precursor powder are added to a high mixing device according to a molar ratio Li / (Ni+Co+Mn)=1.02:1. After low-temperature sintering at 500°C for 240 min in an oxygen atmosphere (oxygen concentration is greater than 97%), after sintering at 600°C for 240 min, high-temperature sintering at 810°C for 720 min, and holding at 600°C for 120 min, and natural cooling to 100°C, a F-doped primary sintered positive electrode material is obtained.

[0039] 2) After mixing LiTaO3(0.13g) with 100g of the F-doped primary sintered positive electrode material in a high mixing device, secondary sintering at 600°C for 10h in an oxygen atmosphere, and natural cooling to 100°C, a Ta-coated lithium ion battery positive electrode material (i.e., a secondary sintered positive electrode material) is obtained.

[0040] 3) After adding 100g of the secondary sintered positive electrode material to 10°C, 50g of deionized water, stirring for 10 min, filtering and washing, dynamic drying for 60 min in a rotary evaporator, and drying for 480 min in a vacuum drying oven at 120°C, SeO2(0.141g) is mixed with the dried sample in a high mixing device, and secondary sintering at 350°C for 10h in an oxygen atmosphere, and natural cooling to 100°C, a F-doped Ta / Se double-coated lithium ion battery positive electrode material is obtained.

[0041] 4) A button cell is prepared and its performance is tested. The F-doped Ta / Se double-coated lithium ion battery positive electrode material LiNi 0.83 Co 0.12 Mn 0.05 O2 is mixed uniformly with conductive agent acetylene black and binder PVDF according to a mass ratio of 90:5:5, 1-methyl-2-pyrrolidone is added in a mass ratio of 20:1 with PVDF, ball milling for 1 hour to prepare a slurry, uniformly coating on an aluminum sheet, drying, and pressing to prepare a positive electrode sheet. A 2032 button cell is assembled with a lithium metal sheet as a negative electrode, and an Siken test system is used for electrical performance testing (charge and discharge voltage is 2.75-4.3V). The results show that the F-doped Ta / Se double-coated lithium ion battery positive electrode material has a first discharge capacity of 209mAh / g at a rate of 0.2C, a first efficiency of 90.1%, a capacity retention rate of 99.5% after 50 cycles at a rate of 1C, and a rate retention rate of 91.4% at a rate of 2C.

[0042] Comparative Example 1

[0043] 1) Take 100g of Ni0.83 Co 0.12 Mn 0.05 (OH)2 precursor, 0.2% doping amount of AlF3(0.061g) was mixed uniformly, and lithium hydroxide and the precursor powder were added into a high-mixing device according to a molar ratio of Li / (Ni+Co+Mn) = 1.02:1. After low-temperature sintering at 500°C for 240 min in an oxygen atmosphere (oxygen concentration greater than 97%), high-temperature sintering at 810°C for 720 min after sintering at 600°C for 240 min, and natural cooling to 100°C after holding at 600°C for 120 min, a F-doped primary sintered positive electrode material was obtained.

[0044] 2) 100g of the F-doped primary sintered positive electrode material was added into 10°C, 50g of deionized water and stirred for 10 min, filtered and washed, and dried in a rotary evaporator for 60 min and in a vacuum drying oven at 120°C for 480 min. After mixing SeO2(0.141g) with the dried sample in a high-mixing device, secondary sintering was performed at 350°C for 10h in an oxygen atmosphere, and the sample was naturally cooled to 100°C to obtain a F-doped Se-coated lithium ion battery positive electrode material.

[0045] 3) A button cell was prepared and the electrical performance was tested. The F-doped Se-coated lithium ion battery positive electrode material LiNi 0.83 Co 0.12 Mn 0.05 O2, conductive agent acetylene black, and binder PVDF were mixed uniformly according to a mass ratio of 90:5:5, 1-methyl-2-pyrrolidone was added in a mass ratio of 20:1 with respect to PVDF, and ball milling was performed for 1h to prepare a slurry, which was uniformly coated on an aluminum sheet, dried, and pressed to prepare a positive electrode sheet. A 2032 button cell was assembled with a lithium metal sheet as a negative electrode, and the electrical performance was tested using a Siken test system (charge-discharge voltage was 2.75-4.3V). The results showed that the doped and coated positive electrode material had a first discharge capacity of 203mAh / g at a rate of 0.2C, a first efficiency of 87.5%, a capacity retention rate of 91.6% after 50 cycles at a rate of 1C, and a rate retention rate of 89.7% at a rate of 2C.

[0046] Comparative Example 2

[0047] 1) 100g of Ni 0.83 Co 0.12 Mn 0.05The F-doped primary sintered cathode material is obtained by mixing the (OH)2precursor, 0.2% doping amount of AlF3(0.061 g) uniformly, adding lithium hydroxide and the precursor powder in a molar ratio of Li / (Ni+Co+Mn) = 1.02:1 into a high-mixing device, sintering at 500°C for 240 min in an oxygen atmosphere (oxygen concentration greater than 97%), sintering at 600°C for 240 min, sintering at 810°C for 720 min, cooling to 600°C for 120 min, and naturally cooling to 100°C.

[0048] 2) After mixing LiTaO3(0.13 g) and 100 g of the F-doped primary sintered cathode material in a high-mixing device, the Ta-coated lithium ion battery cathode material (i.e., the secondary sintered cathode material) is obtained by secondary sintering at 600°C for 10 h in an oxygen atmosphere and naturally cooling to 100°C.

[0049] 3) After adding 100 g of the secondary sintered cathode material into 10°C deionized water (50 g), stirring for 10 min, filtering and washing, dynamic drying for 60 min in a rotary evaporator, and drying for 480 min in a vacuum drying oven at 120°C, the F-doped Ta-coated lithium ion battery cathode material is obtained by secondary sintering at 350°C for 10 h in an oxygen atmosphere and naturally cooling to 100°C.

[0050] 4) A button cell is prepared and the electrical performance is tested. The F-doped Ta-coated lithium ion battery cathode material LiNi 0.83 Co 0.12 Mn 0.05 O2 is mixed with conductive agent acetylene black and binder PVDF in a mass ratio of 90:5:5, ball-milled for 1 h with 1-methyl-2-pyrrolidone in a mass ratio of 20:1 to prepare a slurry, uniformly coated on an aluminum sheet, dried and pressed into a cathode sheet. A 2032 button cell is assembled with a lithium metal sheet as the negative electrode, and the electrical performance is tested using a Siken test system (charge-discharge voltage is 2.75-4.3 V). The results show that the doped and coated cathode material has a first discharge capacity of 207 mAh / g at a rate of 0.2C, a first efficiency of 89.2%, and a capacity retention rate of 92.6% after 50 cycles at a rate of 1C.

[0051] Comparative Example 3

[0052] 1) 100 g of Ni 0.83 Co 0.12 Mn 0.05The F-doped Ta / Se double-coated lithium ion battery cathode material is obtained by mixing the F-doped primary sintered cathode material with SeO2 (0.141 g) in a high-mixing device under an oxygen atmosphere at 350 °C for 10 h and naturally cooling to 100 °C.

[0053] 2) The Ta-coated lithium ion battery cathode material (i.e., the secondary sintered cathode material) is obtained by mixing LiTaO3 (0.13 g) with 100 g of the F-doped primary sintered cathode material in a high-mixing device under an oxygen atmosphere at 600 °C for 10 h and naturally cooling to 100 °C.

[0054] 3) The F-doped Ta / Se double-coated lithium ion battery cathode material is obtained by mixing SeO2 (0.141 g) with the secondary sintered cathode material in a high-mixing device under an oxygen atmosphere at 350 °C for 10 h and naturally cooling to 100 °C.

[0055] 4) A button cell is prepared and its performance is tested. The F-doped Ta / Se double-coated lithium ion battery cathode material LiNi 0.83 Co 0.12 Mn 0.05 O2 is mixed with the conductive agent acetylene black and the binder PVDF in a mass ratio of 90:5:5, and 1-methyl-2-pyrrolidone is added in a mass ratio of 20:1 to the PVDF and ball-milled for 1 h to prepare a slurry, which is uniformly coated on an aluminum sheet, dried, and pressed to prepare a cathode sheet. A 2032 button cell is assembled with a lithium metal sheet as the anode, and the electrical performance is tested using a Siken test system (the charge and discharge voltage is 2.75-4.3 V). The results show that the F-doped Ta / Se double-coated lithium ion battery cathode material has a first discharge capacity of 205 mAh / g at a rate of 0.2 C, a first efficiency of 88.4%, and a capacity retention rate of 97.4% after 50 cycles at a rate of 1 C.

[0056] Example 2

[0057] 1) 100 g of Ni 0.88 Co 0.09 Mn 0.03The F-doped Ta / Se double-coated lithium ion battery cathode material was obtained by mixing LiOH and the precursor powder in a molar ratio of Li / (Ni+Co+Mn) = 1.02:1 in a high-mixing device, mixing the (OH)2 precursor and 0.2% doping amount of AlF3 (0.061 g) uniformly, and then sintering at 500°C for 240 min in an oxygen atmosphere (oxygen concentration greater than 97%), sintering at 600°C for 240 min, sintering at 790°C for 720 min, cooling to 600°C for 120 min, and then naturally cooling to 100°C.

[0058] 2) The Ta-coated lithium ion battery cathode material (i.e., the secondary sintered cathode material) was obtained by mixing LiTaO3 (0.13 g) and 100 g of the F-doped primary sintered cathode material in a high-mixing device, sintering at 600°C for 10 h in an oxygen atmosphere, and then naturally cooling to 100°C.

[0059] 3) The F-doped Ta / Se double-coated lithium ion battery cathode material was obtained by mixing SeO2 (0.141 g) and the dried sample in a high-mixing device, sintering at 350°C for 10 h in an oxygen atmosphere, and then naturally cooling to 100°C.

[0060] 4) A button cell was prepared and its performance was tested. The F-doped Ta / Se double-coated lithium ion battery cathode material LiNi 0.88 Co 0.09 Mn 0.03 O2 was mixed with conductive agent acetylene black and binder PVDF in a mass ratio of 90:5:5, ball-milled with 1-methyl-2-pyrrolidone in a mass ratio of 20:1 for 1 h to prepare a slurry, uniformly coated on an aluminum sheet, dried and pressed to prepare a cathode sheet. A 2032 button cell was assembled with a lithium metal sheet as the anode, and the electrical performance was tested by using a Siken test system (charge-discharge voltage was 2.75-4.3 V). The results showed that the F-doped Ta / Se double-coated lithium ion battery cathode material had a first discharge capacity of 217 mAh / g at a rate of 0.2C, a first efficiency of 90.5%, and a capacity retention rate of 98.8% after 50 cycles at a rate of 1C.

[0061] Comparative Example 4:

[0062] 1) 100 g of Ni 0.88 Co 0.09 Mn 0.03The F-doped primary sintered cathode material is obtained by mixing the (OH)2precursor, 0.2% doping amount of AlF3(0.061 g) uniformly, adding lithium hydroxide and the precursor powder in a molar ratio of Li / (Ni+Co+Mn) = 1.02:1 into a high-mixing device, sintering at 500°C for 240 min in an oxygen atmosphere (oxygen concentration greater than 97%), sintering at 600°C for 240 min, sintering at 790°C for 720 min, cooling to 600°C for 120 min, and naturally cooling to 100°C.

[0063] 2) After mixing LiTaO3(0.13 g) and 100 g of the F-doped primary sintered cathode material in a high-mixing device, the Ta-coated lithium ion battery cathode material (i.e., the secondary sintered cathode material) is obtained by secondary sintering at 600°C for 10 h in an oxygen atmosphere and naturally cooling to 100°C.

[0064] 3) After adding 100 g of the secondary sintered cathode material to 10°C, 50 g of deionized water, stirring for 10 min, filtering and washing, dynamic drying for 60 min in a rotary evaporator, and drying for 480 min in a vacuum drying oven at 120°C, the F-doped Ta-coated lithium ion battery cathode material is obtained by secondary sintering at 350°C for 10 h in an oxygen atmosphere and naturally cooling to 100°C.

[0065] 4) A button cell is prepared and the electrical performance is tested. The F-doped Ta-coated lithium ion battery cathode material LiNi 0.88 Co 0.09 Mn 0.03 O2 is mixed with conductive agent acetylene black and binder PVDF in a mass ratio of 90:5:5, ball-milled for 1 h with 1-methyl-2-pyrrolidone in a mass ratio of 20:1 to prepare a slurry, uniformly coated on an aluminum sheet, dried and pressed to prepare a cathode sheet. A 2032 button cell is assembled with a lithium metal sheet as the negative electrode, and the electrical performance is tested using a Siken test system (charge-discharge voltage is 2.75-4.3 V). The results show that the doped and coated cathode material has a first discharge capacity of 212 mAh / g at a rate of 0.2C, a first efficiency of 89.4%, and a capacity retention rate of 93.5% after 50 cycles at a rate of 1C.

[0066] Example 3

[0067] 1) 100 g of Ni 0.80 Co 0.10 Mn 0.10The F-doped Ta / Se double-coated lithium ion battery cathode material was obtained by mixing LiOH and the precursor powder in a molar ratio of Li / (Ni+Co+Mn) = 1.02:1 in a high-mixing device, mixing the (OH)2 precursor and 0.2% doping amount of AlF3 (0.061 g) uniformly, and then sintering at 500°C for 240 min in an oxygen atmosphere (oxygen concentration greater than 97%), sintering at 600°C for 240 min, sintering at 850°C for 720 min, cooling to 600°C for 120 min, and then naturally cooling to 100°C.

[0068] 2) The Ta-coated lithium ion battery cathode material (i.e., the secondary sintered cathode material) was obtained by mixing LiTaO3 (0.13 g) and 100 g of the F-doped primary sintered cathode material in a high-mixing device, and then sintering at 600°C for 10 h in an oxygen atmosphere, and naturally cooling to 100°C.

[0069] 3) The F-doped Ta / Se double-coated lithium ion battery cathode material was obtained by mixing SeO2 (0.141 g) and the dried sample in a high-mixing device, and then sintering at 350°C for 10 h in an oxygen atmosphere, and naturally cooling to 100°C.

[0070] 4) A button cell was prepared and the electrical performance was tested. The F-doped Ta / Se double-coated lithium ion battery cathode material LiNi 0.80 Co 0.10 Mn 0.10 O2 was mixed with conductive agent acetylene black and binder PVDF in a mass ratio of 90:5:5, and then 1-methyl-2-pyrrolidone was added in a mass ratio of 20:1 to the PVDF, and the mixture was ball-milled for 1 h to prepare a slurry, which was uniformly coated on an aluminum sheet, dried, and pressed to prepare a cathode sheet. A 2032 button cell was assembled with a lithium metal sheet as the anode, and the electrical performance was tested by using a Siken test system (charge-discharge voltage was 2.75-4.3 V). The results showed that the F-doped Ta / Se double-coated lithium ion battery cathode material had a first discharge capacity of 203 mAh / g at a rate of 0.2C, a first efficiency of 89.9%, and a capacity retention rate of 98.8% after 50 cycles at a rate of 1C.

[0071] Comparative Example 5

[0072] 1) LiOH and 100 g of the F-doped primary sintered cathode material were mixed in a molar ratio of Li / (Ni+Co+Mn) = 1.02:1 in a high-mixing device, and then sintered at 500°C for 240 min in an oxygen atmosphere (oxygen concentration greater than 97%), sintered at 600°C for 240 min, sintered at 850°C for 720 min, cooled to 600°C for 120 min, and then naturally cooled to 100°C. 0.80 Co 0.10 Mn 0.10The (OH)2 precursor powder is added to a high-mixing device in a molar ratio of Li / (Ni+Co+Mn) = 1.02:1, sintered at a low temperature of 500°C for 240 min in an oxygen atmosphere (oxygen concentration greater than 97%), sintered at 600°C for 240 min, and then sintered at a high temperature of 850°C for 720 min, and then cooled to 600°C for 120 min, and then naturally cooled to 100°C to obtain a doped primary sintered positive electrode material.

[0073] 2) After mixing LiTaO3 (0.13 g) with 100 g of the doped primary sintered positive electrode material in a high-mixing device, the mixture is sintered at a secondary sintering temperature of 600°C for 10 h in an oxygen atmosphere, and then naturally cooled to 100°C to obtain a Ta-coated lithium ion battery positive electrode material (i.e., a secondary sintered positive electrode material).

[0074] 3) 100 g of the secondary sintered positive electrode material is added to 10°C deionized water (50 g) and stirred for 10 min, filtered and washed, and then dried in a rotary evaporator for 60 min, and then dried in a vacuum drying oven at 120°C for 480 min, and then mixed SeO2 (0.141 g) with the dried sample in a high-mixing device, and then sintered at a secondary sintering temperature of 350°C for 10 h in an oxygen atmosphere, and then naturally cooled to 100°C to obtain a F-doped Ta / Se double-coated lithium ion battery positive electrode material.

[0075] 4) A button cell is prepared and the electrical performance is tested. The F-doped Ta / Se double-coated lithium ion battery positive electrode material LiNi 0.80 Co 0.10 Mn 0.10 O2 is mixed with conductive agent acetylene black and binder PVDF in a mass ratio of 90:5:5, and then ball-milled with 1-methyl-2-pyrrolidone in a mass ratio of 20:1 for 1 h to prepare a slurry, which is uniformly coated on an aluminum sheet, dried, and pressed to form a positive electrode sheet. A 2032 button cell is assembled with a lithium metal sheet as the negative electrode, and the electrical performance is tested using a Siken test system (charge-discharge voltage is 2.75-4.3 V). The results show that the F-doped Ta / Se double-coated lithium ion positive electrode material has a first discharge capacity of 199.1 mAh / g at a rate of 0.2C, a first efficiency of 87.4%, and a capacity retention rate of 92.3% after 50 cycles at a rate of 1C.

[0076] The comparison chart of the retention rate curves of Example 1 and Comparative Example 1 at a rate of 1C is as follows: Figure 1 It can be seen that the cycle retention rate of the co-coated positive electrode material is significantly improved compared to the positive electrode material without Ta coating, direct water washing, and Se coating.

[0077] The comparison chart of the rate performance curves of Example 1 and Comparative Example 1 at different rates is as follows: Figure 2It can be seen that the rate performance of the positive electrode material after co-coating is obviously improved compared with that of the positive electrode material directly washed and dried after Se coating without Ta coating.

[0078] The comparison chart of lithium ion diffusion curves of the charged lithium ion of example 1 and comparative example 1 is as follows Figure 3 It can be seen that the lithium ion diffusion coefficient of the positive electrode material after co-coating is higher than that of the positive electrode material directly washed and dried after Se coating without Ta coating.

[0079] The comparison chart of the retention rate curves of example 1 and comparative example 2 at 1C is as follows Figure 4 It can be seen that the cycle retention rate of the positive electrode material after co-coating is obviously improved compared with that of the positive electrode material directly washed and dried after Se coating without Ta coating.

[0080] The comparison chart of the cycle retention rate curves of example 1 and comparative example 3 at 1C is as follows Figure 5 It can be seen that the three-stage sintering can improve the cycle performance of the positive electrode material and improve the stability of the crystal structure.

[0081] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing Ta / Se double-coated nickel-cobalt-manganese ternary lithium-ion battery cathode material, comprising the following steps: (1) adding a F-containing compound, a nickel-cobalt-manganese composite precursor, and a lithium source into a high-speed mixer for mixing, and firing at three different temperature stages to obtain a doped matrix; (2) adding the doped matrix and a Ta source into the high-speed mixer for mixing and firing to obtain a Ta-coated cathode material, and then adding the Ta-coated cathode material into deionized water for stirring and drying; (3) adding the product obtained in step (2) and a Se source into the high-speed mixer for mixing and firing to obtain a Ta / Se double-coated nickel-cobalt-manganese ternary lithium-ion battery cathode material. The molar amount of F is 0.001%-0.5% of the sum of the molar amounts of nickel, cobalt, and manganese. The F-containing compound is one or more of AlF3, MgF2, and SiF4. The amount of the lithium source is 0.9-1.1 times the sum of the molar amounts of nickel, cobalt, and manganese in terms of Li element; and / or, the lithium source comprises one or more of lithium hydroxide, lithium carbonate, lithium nitrate, and lithium acetate.

2. The method of claim 1, wherein, The nickel cobalt manganese composite precursor is Ni x Co y Mn 1-x-y (OH)2, wherein 0.5≤x<1, 0 3. The method of claim 1, wherein, In step (1), the three different temperature stages of firing comprise: firing temperature 1 is 300℃-500℃, and the firing time is 1-4h; firing temperature 2 is 400-600℃, and the firing time is 1-4h; and firing temperature 3 is 700-900℃, and the firing time is 8-15h.

4. The method of claim 1, wherein, In step (2), the Ta source is one or more of a tantalum salt, an oxide, a boride, and a nitride of tantalum; and / or, the coating amount of Ta element is 1000-3000ppm based on the doped matrix obtained in step (1).

5. The method of claim 1, wherein, In step (2), the firing temperature is 600℃-800℃, and the firing time is 6h-12h.

6. The method of claim 1, wherein, The Se source is one or more of selenium oxide and selenium fluoride; and / or, the coating amount of Se element is 1000-3000ppm based on the doped matrix obtained in step (1).

7. The method of claim 1, wherein, In step (3), the firing temperature is 200℃-500℃, and the firing time is 6h-12h.

8. The method of claim 1, wherein, ​ 9. The method of claim 1, wherein, ​ 10. The method of claim 1, wherein, ​

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