Ternary positive electrode material, preparation method and application thereof

Abstract

The application provides a ternary positive electrode material, a preparation method and application thereof. a Co b Mn 1‑a‑b (OH)2 and lithium hydroxide are mixed and sintered to obtain a base material; 0.7<=a<1, 0<b<0.2; boron trifluoride ether, propylene oxide and trimethylolpropane-polyethylene glycol monomethyl ether are subjected to a first reaction; the first reactants are subjected to a second reaction with a modification liquid, and post-treatment is performed to obtain modified dihydric alcohol; the modification liquid is a mixture of cyclodextrin and alkali solution; a dihydric alcohol inclusion material is obtained by taking a mixture of lambda-MnO2 and lithium source as a core layer and a polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol as a coating layer; the base material is mixed with a first isocyanate, dried to obtain a first solid material, mixed with the dihydric alcohol inclusion material for a first polymerization to obtain a pre-modified ternary positive electrode material, and then mixed with a second isocyanate, dried to obtain a second solid material; the modified dihydric alcohol is subjected to a second polymerization with the second solid material to obtain a ternary positive electrode material. The application can solve the problems of poor low-temperature performance and slow charging and discharging rate of lithium ion batteries.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a ternary positive electrode material, a preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries are widely used in portable devices, electric vehicles and large-scale energy storage fields due to their high energy density, long cycle life and other outstanding advantages. However, lithium ion batteries are sensitive to external temperature, especially at low working temperature, the energy density and power density decrease sharply, which seriously limits their application in cold regions. At the same time, with the rapid expansion of the electric vehicle market, problems related to electric vehicles are becoming more and more prominent, one of the most serious problems is the long charging time, and the demand for fast charging is increasingly urgent.

[0003] The low temperature performance of lithium iron phosphate positive electrode is very poor, and the energy density is low, while the lithium nickel cobalt manganese oxide ternary positive electrode material has high energy density and good low temperature performance and is concerned. Therefore, it is urgent to provide a ternary positive electrode material to solve the problems of lithium deposition and ion solid phase diffusion slowing down of the applied battery at low temperature and high rate, so as to reduce the growth of polarization resistance of the battery, so that the battery has excellent high rate fast charge and discharge performance at low temperature. SUMMARY

[0004] The main purpose of the present application is to provide a ternary positive electrode material, a preparation method and application thereof, so as to solve the problems of poor low temperature performance and slow charge and discharge rate of lithium ion batteries in the prior art.

[0005] In order to achieve the above purpose, according to one aspect of the present application, a preparation method of a ternary positive electrode material is provided, which comprises the following steps: S1, mixing a precursor Ni a Co b Mn 1-a-bThe precursor Ni (OH) 2 is mixed with lithium hydroxide, and then sintering treatment is performed to obtain the base material; wherein 0.7≤a<1, 0<b<0.2; S2, first reaction is performed on boron trifluoride ether, propylene oxide and trimethylolpropane-polyethylene glycol monomethyl ether to obtain a first reactant; second reaction is performed on the modification liquid and the first reactant to obtain a second reactant; solid-liquid separation is performed on the second reactant, and the clear liquid is dried to obtain a modified diol; wherein the modification liquid is a mixture of cyclodextrin and alkali solution; S3, the core layer is mixed with the lithium source mixture, and the polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol is coated on the surface of the core layer to obtain a diol inclusion material; S4, the base material is mixed with the first isocyanate, and after the first drying, a first solid material is obtained; then the first polymerization reaction is performed on the diol inclusion material and the first solid material to obtain a pre-modified ternary positive electrode material; S5, the pre-modified ternary positive electrode material is mixed with the second isocyanate, and after the second drying, a second solid material is obtained; the second polymerization reaction is performed on the modified diol and the second solid material to obtain the ternary positive electrode material.

[0006] Further, step S1 comprises: mixing the precursor Ni a Co b Mn 1-a-b The precursor Ni (OH) 2 is mixed with lithium hydroxide, and then sintering treatment is performed under an oxygen-rich atmosphere, and then crushing and sieving are performed to obtain the base material; wherein the oxygen content of the oxygen-rich atmosphere is ≥93vol%; preferably, the particle size test value of the base material satisfies (D90-D10) / D50≤1.6; preferably, the precursor Ni a Co b Mn 1-a-b The weight ratio of the precursor Ni (OH) 2 to lithium hydroxide is 2.02-2.74:1.

[0007] Further, the sintering treatment comprises a temperature rising stage, a first holding stage, a first temperature decreasing stage, a second holding stage and a second temperature decreasing stage in sequence; wherein preferably, the temperature rising rate of the temperature rising stage is 10-40℃ / h; preferably, the temperature of the first holding stage is 750-900℃, and the time of the first holding stage is 15-20h; preferably, the temperature decreasing rate of the first temperature decreasing stage is 100-200℃ / h; preferably, the temperature of the second holding stage is 400-600℃, and the time of the second holding stage is 5-10h; preferably, the temperature decreasing rate of the second temperature decreasing stage is 10-50℃ / h.

[0008] Further, the weight ratio of the boron trifluoride ether, the propylene oxide and the trimethylolpropane-polyethylene glycol monomethyl ether is 1:2-8:50-200; preferably, the weight ratio of the boron trifluoride ether and the modification liquid is 1:20-50.

[0009] Further, the average molecular weight of trimethylolpropane-polyethylene glycol monomethyl ether is 500-3000.

[0010] Further, the temperature of the first reaction is 40-60°C, and the time is 1-2h; preferably, the temperature of the second reaction is 80-100°C, and the time is 4-8h.

[0011] Further, the modification solution is obtained by mixing cyclodextrin and alkali solution in a weight ratio of 1:3-9; preferably, the mixing temperature is 60-80°C, and the time is 3-6h; preferably, the cyclodextrin is one or more of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin; preferably, the alkali solution is aqueous ammonia and / or aqueous sodium hydroxide solution; more preferably, the mass concentration of the alkali solution is 15-45wt%; preferably, the step of drying the clear solution is: adding anhydrous ethanol to the clear solution, followed by vacuum rotary evaporation concentration, and then vacuum drying at 50-80°C.

[0012] Further, the weight ratio of λ-MnO2 and lithium source is 0.3-0.5:0.1; preferably, the weight ratio of λ-MnO2 and polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol is 0.3-0.5:3-5; more preferably, the average molecular weight of the polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol is 1000-8000; most preferably, the lithium source is lithium perchlorate and / or lithium bis(trifluoromethanesulfonyl)imide.

[0013] Further, λ-MnO2 is prepared by the following method: mixing LiMn2O4 and hydrochloric acid in a molar ratio of LiMn2O4 to HCl of 1:18-24, and then performing delithiation treatment to obtain λ-MnO2; wherein the D50 of LiMn2O4 is 1-5nm; preferably, the delithiation treatment is performed at 30-100°C for 1-10h. +

[0014] Further, the weight ratio of the base material and the first isocyanate is 1:0.3-0.9; preferably, the weight ratio of the first isocyanate and the dihydric alcohol inclusion material is 0.3-0.9:1-1.2; preferably, the first isocyanate is toluene diisocyanate and / or isophorone diisocyanate; preferably, the first drying is performed in a vacuum drying oven, the drying temperature is 40-60°C, and the drying time is 15-30min.

[0015] ​Further, the weight ratio of the second isocyanate and the pre-modified ternary cathode material is 1-3:6; preferably, the weight ratio of the second isocyanate and the modified dihydric alcohol is 1-3:0.5-0.8; preferably, the second isocyanate is L-lysine ethyl ester diisocyanate; preferably, the second drying is performed in a vacuum drying oven, and the drying temperature is 50-80℃, and the drying time is 5-10min.

[0016] Further, the step S3 comprises: ball milling the λ-MnO2 and the lithium source, and then stirring the 1,5-pentanediol and the 1,6-hexanediol polycarbonate diol copolymer at 100-120℃ for 4-6h.

[0017] Further, the temperature of the first polymerization reaction is 110-140℃, and the time is 1-2h; the first polymer layer is obtained on the surface of the base material by the first polymerization reaction, and preferably, the thickness of the first polymer layer is 10-30nm.

[0018] Further, the temperature of the second polymerization reaction is 100-120℃, and the time is 10-20min; preferably, after the modified dihydric alcohol is mixed with the second solid material, spin coating is performed to obtain a wet film, and then the second polymerization reaction is performed; more preferably, the thickness of the wet film is 10-30μm; the second polymer layer is obtained on the surface of the pre-modified ternary cathode material by the second polymerization reaction, and preferably, the thickness of the second polymer layer is 15-40nm.

[0019] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a ternary cathode material prepared by the above-mentioned preparation method is provided.

[0020] According to another aspect of the present application, a lithium ion battery comprising the above-mentioned ternary cathode material is provided.

[0021] By applying the technical solution of the present application, a modified ternary cathode material is prepared. The preparation method first forms a first polymer layer on the surface of the base material by the reaction of the dihydric alcohol inclusion material including the λ-MnO2 and the lithium source and the first isocyanate; and then forms a second polymer layer on the surface of the first polymer layer by the reaction of the modified dihydric alcohol and the second isocyanate; thus, the present application prepares a multi-layer core-shell structure with the base material as the core, the first polymer layer containing a three-dimensional network conductive structure as the intermediate layer, and the second polymer layer with high ductility as the outermost layer.

[0022] In the first polymer layer, the incorporation of lambda-MnO2 and lithium source exacerbates the entanglement of the polycarbonate diol copolymer segment of 1,5-pentanediol and 1,6-hexanediol, thereby increasing the degree of phase separation of the polymer, providing abundant spatial sites for lambda-MnO2, facilitating the effective adsorption of lithium ions by lambda-MnO2, and thereby forming a three-dimensional superconducting network structure that improves the lithium ion solid-phase diffusion speed of the positive electrode material at low temperatures. In addition, the polycarbonate-based polymer synthesized using the polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol has excellent weather resistance and solvent resistance, which can effectively optimize the interface performance, inhibit the interface side reaction, and reduce the deposition speed of lithium at low temperatures.

[0023] In the second polymer layer, the present application designs to graft cyclodextrin onto trimethylolpropane-polyethylene glycol monomethyl ether to form a flexible diol with flexible molecular chains and not easy to entangle, and then through polymerization with a second isocyanate, a modified polymer with regular chain segments and a three-dimensional network structure is obtained. The second polymer layer, as the outermost coating layer of the ternary positive electrode material of the present application, wraps the outer surface of the aforementioned first polymer layer. The high ductility of the second polymer layer effectively inhibits the crystal expansion of the positive electrode material under high-rate charging and discharging environment, stabilizes the crystal structure, and improves the capacity decay problem of the positive electrode material under high-rate charging and discharging.

[0024] By combining the above modification methods, the present application prepares a ternary positive electrode material with a multilayer core-shell structure of matrix material / first polymer layer / second polymer layer, which effectively solves the problems of lithium deposition and low lithium ion solid-phase diffusion efficiency of nickel-cobalt-manganese lithium ternary material at low temperature and high rate, and realizes excellent charging and discharging performance at low temperature and high rate. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their description serve the purpose of explaining the present application, and do not constitute an improper limitation of the present application.

[0026] In the drawings:

[0027] Figure 1 The SEM image of the positive electrode material of Example 1 after electrical performance test is shown.

[0028] Figure 2 The SEM image of the positive electrode material of Comparative Example 1 after electrical performance test is shown. DETAILED DESCRIPTION

[0029] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0030] To solve the problems in the prior art as described above, according to an aspect of the present application, there is provided a preparation method of a ternary positive electrode material, comprising the following steps: S1, mixing a precursor Ni a Co b Mn 1-a-b (OH)2 with lithium hydroxide, and then performing sintering treatment to obtain a base material; wherein 0.7≤a<1, 0<b<0.2; S2, performing a first reaction on boron trifluoride ether, propylene oxide and trimethylolpropane-polyethylene glycol monomethyl ether to obtain a first reactant; performing a second reaction on a modification liquid and the first reactant to obtain a second reactant; performing solid-liquid separation on the second reactant, and then purifying and drying the clear liquid to obtain a modified dihydric alcohol; wherein the modification liquid is a mixture of cyclodextrin and an alkali solution; S3, using a mixture of λ-MnO2 and a lithium source as a core layer, and using a polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol to coat the surface of the core layer to obtain a dihydric alcohol inclusion material; S4, mixing the base material with a first isocyanate, and then performing first drying to obtain a first solid material; then performing a first polymerization reaction on the dihydric alcohol inclusion material and the first solid material to obtain a pre-modified ternary positive electrode material; S5, mixing the pre-modified ternary positive electrode material with a second isocyanate, and then performing second drying to obtain a second solid material; performing a second polymerization reaction on the modified dihydric alcohol and the second solid material to obtain a ternary positive electrode material.

[0031] The preparation method of the present application first utilizes the polymerization reaction of the dihydric alcohol inclusion material and the first isocyanate to form a first polymer layer on the surface of the base material; then utilizes the reaction of the modified dihydric alcohol and the second isocyanate to form a second polymer layer on the surface of the first polymer layer; thus, the present application prepares a multi-layer core-shell structure with the base material as the core, the first polymer layer containing a three-dimensional network conductive structure as the intermediate layer, and the second polymer layer with super ductility as the outermost layer.

[0032] In the first polymer layer, the incorporation of λ-MnO2 and the lithium source intensifies the entanglement of the polycarbonate diol copolymer chain segments of 1,5-pentanediol and 1,6-hexanediol, thereby increasing the phase separation degree of the polymer, and providing abundant space sites for λ-MnO2, which is conducive to the effective adsorption of lithium ions by λ-MnO2, so as to form a three-dimensional superconducting network structure to improve the lithium ion solid-phase diffusion speed of the positive electrode material at low temperature. In addition, the polycarbonate-based polymer synthesized by using the polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol has excellent weather resistance and solvent resistance, which can effectively optimize the interface performance, inhibit the interface side reaction, and reduce the deposition speed of lithium at low temperature.

[0033] In the second polymer layer, the present application designs to graft cyclodextrin onto trimethylolpropane-polyethylene glycol monomethyl ether to form a flexible diol with flexible molecular chain and not easy to entangle, and then through polymerization with a second isocyanate, a modified polymer with regular chain segments and three-dimensional network structure is obtained, which is the outermost coating layer of the ternary positive electrode material of the present application, and is wrapped on the outer surface of the first polymer layer. The second polymer layer with super ductility effectively inhibits the crystal expansion of the positive electrode material under high rate charging and discharging environment, stabilizes the structure of the crystal, and improves the capacity decay problem of the positive electrode material under high rate charging and discharging.

[0034] The above modification means are combined, and the present application prepares a ternary positive electrode material with a multilayer core-shell structure of matrix material / first polymer layer / second polymer layer, which effectively solves the problems of lithium deposition and low lithium ion solid-phase diffusion efficiency of nickel-cobalt-manganese lithium ternary material at low temperature and high rate, and realizes excellent low temperature and high rate charging and discharging performance.

[0035] In order to further improve the effect of coating modification, in a preferred embodiment, step S1 comprises: mixing the precursor Ni a Co b Mn 1-a-b (OH)2 with lithium hydroxide, and then performing sintering treatment in an oxygen-rich atmosphere, and then crushing and sieving to obtain the matrix material; wherein the oxygen content of the oxygen-rich atmosphere is ≥93vol%; preferably, the particle size test value of the matrix material satisfies (D90-D10) / D50≤1.6; preferably, the weight ratio of the precursor Ni a Co b Mn 1-a-b (OH)2 to lithium hydroxide is (2.02-2.74):1. The particle size dispersion degree of the matrix material is preferably controlled to be 1.6 or less, which is more beneficial to the effective and continuous coating of the subsequent coating material, so that the two coating layers can better play their role in improving the low temperature performance.

[0036] In a preferred embodiment, the sintering treatment comprises a heating stage, a first holding stage, a first cooling stage, a second holding stage and a second cooling stage which are sequentially performed; wherein, preferably, the heating rate of the heating stage is 10-40℃ / h; preferably, the temperature of the first holding stage is 750-900℃, and the time of the first holding stage is 15-20h; preferably, the cooling rate of the first cooling stage is 100-200℃ / h; preferably, the temperature of the second holding stage is 400-600℃, and the time of the second holding stage is 5-10h; preferably, the cooling rate of the second cooling stage is 10-50℃ / h. Preferably, the above sintering process is used, which is more beneficial to complete sintering, and the matrix material with narrow particle size distribution can be obtained after crushing and sieving.

[0037] In a preferred embodiment, the weight ratio of boron trifluoride etherate, propylene oxide and dihydric alcohol with side chain structure is 1:(2-8):(50-200); preferably, the weight ratio of boron trifluoride etherate and modifying solution is 1:(20-50). The above-mentioned weight ratio is preferred respectively, which is more conducive to the completion of the reaction.

[0038] In a preferred embodiment, the average molecular weight of trimethylolpropane-polyethylene glycol monomethyl ether is 500-3000. As a typical dihydric alcohol with side chain structure, trimethylolpropane-polyethylene glycol monomethyl ether is very suitable for preparing grafted dihydric alcohol with three-dimensional comb structure, thereby preparing polymer coating layer with super ductility.

[0039] In a preferred embodiment, the temperature of the first reaction is 40-60℃, and the time is 1-2h; preferably, the temperature of the second reaction is 80-100℃, and the time is 4-8h. The above-mentioned conditions are preferred, which is more conducive to the full occurrence of the first reaction and the second reaction, thereby obtaining the first reaction product and the second reaction product.

[0040] In a preferred embodiment, the modifying solution is obtained by mixing cyclodextrin and alkali solution according to the weight ratio of 1:3-9; preferably, the temperature of the reaction is 60-80℃, and the time is 3-6h; preferably, the cyclodextrin is one or more of α-cyclodextrin, β-cyclodextrin and γ-cyclodextrin; preferably, the alkali solution is aqueous ammonia and / or aqueous sodium hydroxide solution; more preferably, the mass concentration of the alkali solution is 15-45wt%; preferably, the step of drying the clear solution is: adding anhydrous ethanol to the clear solution, then vacuum rotary evaporation, and then vacuum drying at 50-80℃. The above-mentioned raw materials and mass concentration are preferred, which is more conducive to the reaction with the second solid material, thereby obtaining the second polymer layer.

[0041] In a preferred embodiment, the weight ratio of λ-MnO2 and lithium source is (0.3-0.5):0.1; preferably, the weight ratio of λ-MnO2 and polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol is (0.3-0.5):(3-5); more preferably, the average molecular weight of the polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol is 1000-8000; most preferably, the lithium source is lithium perchlorate and / or lithium bis(trifluoromethanesulfonyl)imide. The above-mentioned weight ratio of λ-MnO2 and lithium source is preferred, which is more conducive to the adsorption of lithium ions by λ-MnO2. The above-mentioned weight ratio of λ-MnO2 and polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol is preferred, which is more conducive to the good dispersion of λ-MnO2 in the polycarbonate base. The above-mentioned molecular weight of the polycarbonate diol polymer is preferred, which is more conducive to its participation in the subsequent first polymerization reaction, thereby forming the first polymer layer.

[0042] In a preferred embodiment, the λ-MnO2 is prepared by mixing LiMn2O4 and hydrochloric acid in a molar ratio of LiMn2O4 to HCl of 1:(18-24), and then performing a delithiation treatment to obtain the λ-MnO2; wherein the D50 of the LiMn2O4 is 1-5 nm; preferably, the delithiation treatment is performed at 30-100°C for 1-10 h. Preferably, the above method is more advantageous for obtaining the λ-MnO2 with a suitable structure. In actual operation, the delithiation treatment is preferably achieved by magnetic stirring. + In a preferred embodiment, the λ-MnO2 is prepared by mixing LiMn2O4 and hydrochloric acid in a molar ratio of LiMn2O4 to HCl of 1:(18-24), and then performing a delithiation treatment to obtain the λ-MnO2; wherein the D50 of the LiMn2O4 is 1-5 nm; preferably, the delithiation treatment is performed at 30-100°C for 1-10 h. Preferably, the above method is more advantageous for obtaining the λ-MnO2 with a suitable structure. In actual operation, the delithiation treatment is preferably achieved by magnetic stirring.

[0043] In a preferred embodiment, the weight ratio of the base material to the first isocyanate is 1:(0.3-0.9); preferably, the first drying is performed in a vacuum drying oven at a drying temperature of 40-60°C for 15-30 min; preferably, the weight ratio of the first isocyanate to the dihydric alcohol inclusion material is (0.3-0.9):(1-1.2); preferably, the first isocyanate is toluene diisocyanate and / or isophorone diisocyanate. Preferably, the above weight ratios are more advantageous for obtaining the first polyurethane with a suitable molecular weight, and are more advantageous for obtaining the first polymer layer with a suitable coating thickness. Preferably, the above types of first isocyanate are more advantageous for complete reaction and preparation of the first polymer layer.

[0044] In a preferred embodiment, the weight ratio of the second isocyanate to the pre-modified ternary positive electrode material is (1-3):6; preferably, the second drying is performed in a vacuum drying oven at a drying temperature of 50-80°C for 5-10 min; preferably, the weight ratio of the second isocyanate to the modified dihydric alcohol is (1-3):(0.5-0.8); preferably, the second isocyanate is L-lysine ethyl ester diisocyanate. Preferably, the above weight ratios are more advantageous for obtaining the second polymer coating layer with a suitable molecular weight, and are more advantageous for obtaining the second polymer layer with a suitable coating thickness. Preferably, the above types of second isocyanate are more advantageous for synthesizing the polymer coating layer with ultra-high ductility.

[0045] In a preferred embodiment, step S3 comprises: ball milling the λ-MnO2 and the lithium source, and then stirring the mixture with a polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol at 100-120°C for 4-6 h. Preferably, the ball milling is performed first, which is more advantageous for the combination of the lithium source and the λ-MnO2. Preferably, the stirring is performed under the above conditions, which is more advantageous for uniform dispersion of the components in the dihydric alcohol inclusion material.

[0046] In a preferred embodiment, the temperature of the first polymerization reaction is 110-140°C, and the time is 1-2h; the first polymer layer is obtained on the surface of the base material by the first polymerization reaction, and preferably the thickness of the first polymer layer is 10-30nm. The above-mentioned first polymerization reaction conditions are more conducive to achieving good coating effect of the first polymer layer, and are more conducive to the role of improving the low-temperature performance of the lithium ion battery.

[0047] In a preferred embodiment, the temperature of the second polymerization reaction is 100-120°C, and the time is 10-20min; preferably, after mixing the modified dihydric alcohol with the second solid material, spin coating is performed to obtain a wet film for the second polymerization reaction; more preferably, the thickness of the wet film is 10-30pm; the second polymer layer is obtained on the surface of the pre-modified ternary positive electrode material by the second polymerization reaction, and preferably the thickness of the second polymer layer is 15-40nm. The above-mentioned second polymerization reaction conditions are more conducive to achieving good coating effect of the second polymer layer, and are more conducive to the role of stabilizing the crystal structure and improving the capacity decay phenomenon of the positive electrode material under high-rate charge and discharge. Preferably, the use of spin coating is more conducive to the full occurrence of the second polymerization reaction.

[0048] According to another aspect of the present application, a ternary positive electrode material obtained by the above-mentioned preparation method is provided. Due to the characteristics brought by the above-mentioned preparation method, the problem of poor low-temperature performance of the nickel-cobalt-manganese lithium ternary positive electrode material can be effectively overcome, and excellent rate and charge-discharge performance at low temperature can be achieved.

[0049] According to another aspect of the present application, a lithium ion battery comprising the above-mentioned ternary positive electrode material is provided. The lithium ion battery has excellent low-temperature rate and charge-discharge performance.

[0050] The present application will be further described in detail below in combination with specific examples, which cannot be understood as limiting the scope of the present application.

[0051] The following examples and comparative examples are carried out in an oxygen-rich atmosphere, i.e. an atmosphere with an oxygen content of ≥93vol%.

[0052] Example 1

[0053] A preparation procedure of a modified ternary positive electrode material for a lithium ion battery is as follows:

[0054] Preparation of the base material:

[0055] A single-crystal ternary precursor Ni 0.8 Co 0.1 Mn 0.1(OH)2 and lithium hydroxide were mixed and sintered at 750°C for 20 hours under an oxygen-rich atmosphere by heating at 40°C / h and holding at 750°C. Then, the temperature was lowered to 400°C for 10 hours by heating at 100°C / h and held at 750°C / h. Finally, the temperature was lowered to room temperature by 50°C / h. After pulverizing and sieving, a matrix material with D90 of 6.26 μm, D10 of 2.45 μm, and D50 of 4.05 μm was obtained.

[0056] Preparation of modified diols:

[0057] (1) Weigh γ-cyclodextrin and ammonia water at a mass ratio of 1:3 and mechanically stir at 80°C for 4 hours to obtain the modified solution;

[0058] (2) Weigh boron trifluoride ethyl ether, propylene oxide and trimethylolpropane-polyethylene glycol monomethyl ether with a molecular weight of 500, mix them and react at 60°C for 2 hours to obtain the first reactant; then add the modification solution dropwise to the first reactant, continue to heat to 100°C and react for 8 hours to obtain the second reactant; take the supernatant of the second reactant, add anhydrous ethanol to the supernatant, concentrate by vacuum rotary evaporation and then dry under vacuum at 50°C to obtain cyclodextrin-grafted trimethylolpropane-polyethylene glycol monomethyl ether; the mass ratio of boron trifluoride ethyl ether, propylene oxide, trimethylolpropane-polyethylene glycol monomethyl ether and modification solution in the above preparation steps is 1:2:200:20;

[0059] Preparation of diol inclusion compounds:

[0060] (1) According to LiMn2O4 and H + LiMn2O4 with a D50 of 5 nm was mixed with hydrochloric acid at a molar ratio of 1:18 and subjected to magnetic stirring at 30 °C for 2 h to remove lithium, yielding λ-MnO2.

[0061] (2) λ-MnO2 and lithium perchlorate were ball-milled in a ball mill for 2 hours, and then mechanically stirred at 120°C for 6 hours with a polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol with a molecular weight of 1000 to obtain a diol encapsulation material; the mass ratio of λ-MnO2, polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol and lithium perchlorate in the above preparation steps was 0.3:3:0.1.

[0062] Preparation of the first polymer layer:

[0063] The matrix material was immersed in toluene diisocyanate, mechanically stirred, and then dried in a vacuum drying oven at 40°C for 30 min to obtain the first solid material. Then, the diol inclusion material was added to the first solid material, mechanically stirred, and then thermally polymerized at 140°C for 2 h to obtain a pre-modified ternary cathode material with a first polymer coating layer thickness of 10 nm. In the above preparation steps, the mass ratio of matrix material, toluene diisocyanate, and diol inclusion material was 1:0.3:1.2.

[0064] Second polymer layer preparation:

[0065] The pre-modified ternary positive electrode material was immersed again in L-lysine ethyl ester diisocyanate, and after mechanical stirring, was placed in a vacuum drying oven at 80°C for 15 min to obtain a second solid material; then the modified dihydric alcohol was added to the second solid material, and a spin coater was used to spin coat a wet film with a thickness of 30 μm, and after drying at 120°C for 20 min, a modified ternary positive electrode material with a second polymer layer thickness of 15 nm was prepared; in the above preparation steps, the mass ratio of L-lysine ethyl ester diisocyanate, pre-modified ternary positive electrode material, and modified dihydric alcohol was 1:6:0.5.

[0066] Comparative Example 1

[0067] The difference from Example 1 is that the heating rate of the first heating stage is 120°C / h, and after obtaining the base material, no modification is performed.

[0068] Example 2

[0069] A preparation procedure of a modified ternary positive electrode material for a lithium ion battery is as follows:

[0070] Base material preparation:

[0071] A single-crystal ternary precursor Ni 0.7 Co 0.1 Mn 0.2 (OH)2 and lithium hydroxide were weighed according to a mass ratio of 2.36:1, mixed, and then placed in an oxygen-rich atmosphere and heated to 900°C at a rate of 20°C / h, and then sintered for 15 h, then reduced to 600°C at a rate of 100°C / h, and then sintered for 10 h, and then reduced to room temperature at a rate of 10°C / h, and then crushed and sieved to obtain a base material with a D90 of 5.73 μm, a D10 of 2.17 μm, and a D50 of 3.56 μm;

[0072] Modified dihydric alcohol preparation:

[0073] (1) β-cyclodextrin and a sodium hydroxide aqueous solution were weighed according to a mass ratio of 1:9, and a modified solution was prepared by mechanical stirring at 80°C for 3 h;

[0074] (2) Boron trifluoride ether, propylene oxide, and a trimethylolpropane-polyethylene glycol monomethyl ether with a molecular weight of 1000 were mixed and reacted at 40°C for 2 h to obtain a first reactant; then the modified solution was added dropwise to the first reactant, and the temperature was further increased to 80°C, and the reaction was continued for 6 h to obtain a second reactant; the upper clear liquid of the second reactant was taken, anhydrous ethanol was added to the upper clear liquid, and then vacuum rotary evaporation was performed to concentrate, and then vacuum drying was performed at 80°C to obtain a cyclodextrin grafted trimethylolpropane-polyethylene glycol monomethyl ether; in the above preparation steps, the mass ratio of boron trifluoride ether, propylene oxide, trimethylolpropane-polyethylene glycol monomethyl ether, and the modified solution was 1:8:200:40;

[0075] Preparation of the diol inclusion material:

[0076] (1) LiMn204 with a D50 of 1 nm was mixed with hydrochloric acid at a molar ratio of LiMn204 to HCl of 1:24, and after lithium removal by magnetic stirring at 100°C for 10 h, λ-MnO2 was obtained; +

[0077] (2) The λ-MnO2, lithium bis(trifluoromethanesulfonyl)imide, and a polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol with a molecular weight of 5000 were placed in a ball mill and ball milled for 1 h, and then mechanically stirred at 100°C for 4 h to obtain a diol inclusion material; the mass ratio of the λ-MnO2, the polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol, and the lithium bis(trifluoromethanesulfonyl)imide in the above preparation step was 0.5:3:0.1;

[0078] Preparation of the first polymer layer:

[0079] The substrate material was immersed in isophorone diisocyanate, and after mechanical stirring, it was placed in a vacuum drying oven at 60°C for drying for 30 min to obtain a first solid material; then the diol inclusion material was added to the first solid material, and after mechanical stirring, it was subjected to thermal polymerization reaction at 110°C for 2 h to prepare a pre-modified ternary positive electrode material with a first polymer layer thickness of 30 nm; the mass ratio of the substrate material, isophorone diisocyanate, and diol inclusion material in the above preparation step was 1:0.9:1;

[0080] Preparation of the second polymer layer:

[0081] The pre-modified ternary positive electrode material was again immersed in L-lysine ethyl ester diisocyanate, and after mechanical stirring, it was placed in a vacuum drying oven at 60°C for drying for 5 min to obtain a second solid material; then the modified diol was added to the second solid material, and a wet film with a thickness of 10 μm was obtained by spin coating with a spin coater, and after drying at 100°C for 10 min, a modified ternary positive electrode material with a second polymer layer thickness of 40 nm was prepared; the mass ratio of L-lysine ethyl ester diisocyanate, pre-modified ternary positive electrode material, and modified diol in the above preparation step was 3:6:0.8.

[0082] Comparative Example 2

[0083] The difference from Example 2 is that the modified diol was not prepared, and the second polymer layer was also not prepared.

[0084] Example 3

[0085] A preparation procedure of a modified ternary positive electrode material for a lithium ion battery is as follows:

[0086] Preparation of the substrate material:

[0087] ​Take single crystal ternary precursor Ni 0.7 Co 0.1 Mn 0.2 (OH)2 and lithium hydroxide, after mixing, placed in an oxygen-rich atmosphere, heated to 750℃ at 10℃ / h, sintered for 15h, then reduced to 400℃ at 100℃ / h, kept for 5h, then reduced to room temperature at 10℃ / h, crushed and sieved to obtain a matrix material with D90 of 6.92μm, D10 of 1.95μm and D50 of 3.11μm;

[0088] Modification of dihydric alcohol preparation:

[0089] (1) Take α-cyclodextrin and sodium hydroxide solution according to the mass ratio of 1:6, mechanically stir at 65℃ for 4h to prepare a modification solution;

[0090] (2) Take boron trifluoride ether, propylene oxide and trimethylolpropane-polyethylene glycol monomethyl ether with a molecular weight of 500, mix and react at 40℃ for 1h to obtain the first reactant; then add the modification solution dropwise into the first reactant, continue to heat to 80℃, react for 4h to obtain the second reactant; take the supernatant of the second reactant, add anhydrous ethanol to the supernatant, then vacuum rotary evaporate and concentrate, and then vacuum dry at 55℃ to obtain cyclodextrin grafted trimethylolpropane-polyethylene glycol monomethyl ether; the mass ratio of boron trifluoride ether, propylene oxide, trimethylolpropane-polyethylene glycol monomethyl ether and modification solution in the above preparation steps is 1:2:50:20;

[0091] Dihydric alcohol inclusion preparation:

[0092] (1) Mix LiMn2O4 with a D50 of 1nm and hydrochloric acid according to the molar ratio of LiMn2O4 to H + Cl of 1:18, and after delithiation at 80℃ for 4h, obtain λ-MnO2;

[0093] (2) Put λ-MnO2 and lithium bistrifluoromethanesulfonimide into a ball mill and ball mill for 1h, then mechanically stir with polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol with a molecular weight of 1000 at 100℃ for 4h to obtain dihydric alcohol inclusion; the mass ratio of λ-MnO2, polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol, and lithium bistrifluoromethanesulfonimide in the above preparation steps is 0.3:3:0.1;

[0094] First polymer layer preparation:

[0095] The base material is immersed in toluene diisocyanate, dried in a 45℃ vacuum drying oven for 20min after mechanical stirring, to obtain a first solid material; then the diol inclusion material is added to the first solid material, and the first modified ternary positive electrode material with a first coating layer thickness of 20nm is prepared after 1h of thermal polymerization reaction at 110℃; the mass ratio of the base material, toluene diisocyanate and diol inclusion material in the above preparation steps is 1:0.3:1;

[0096] Preparation of the second polymer layer:

[0097] The modified ternary positive electrode material is again immersed in L-lysine ethyl ester diisocyanate, dried in a 70℃ vacuum drying oven for 8min after mechanical stirring, to obtain a second solid material; then the modified diol is added to the second solid material, and the second polymer layer thickness of the modified ternary positive electrode material is 15nm after spin coating with a spin coater to obtain a wet film with a thickness of 10μm and drying at 100℃ for 10min; the mass ratio of L-lysine ethyl ester diisocyanate, modified ternary positive electrode material and modified diol in the above preparation steps is 1:6:0.5.

[0098] Comparative Example 3

[0099] The difference from Example 3 is that no diol inclusion material is prepared, and no second polymer layer is prepared.

[0100] Example 4

[0101] The preparation steps of a modified ternary positive electrode material for a lithium ion battery are as follows:

[0102] Preparation of the base material:

[0103] A single-crystal ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 and lithium hydroxide are weighed in a mass ratio of 2.56:1, mixed, and then heated to 840℃ at a rate of 30℃ / h under an oxygen-rich atmosphere, and sintered for 18h, then reduced to 500℃ at a rate of 160℃ / h, and then reduced to room temperature at a rate of 30℃ / h, and then crushed and sieved to obtain a base material with a D90 of 7.11μm, a D10 of 1.50μm, and a D50 of 4.32μm;

[0104] Preparation of the modified diol:

[0105] (1) α-cyclodextrin and ammonia water are weighed in a mass ratio of 1:4, and a modified solution is prepared by mechanical stirring at 75℃ for 5h;

[0106] (2) The first reactant is obtained by mixing boro-trifluoride ether, propylene oxide and trimethylolpropane-polyethylene glycol monomethyl ether with a molecular weight of 2000 at 45°C for 1.2h; then the modification solution is added dropwise into the first reactant, and the temperature is increased to 90°C for 6h to obtain the second reactant; the upper clear liquid of the second reactant is taken, anhydrous ethanol is added into the upper clear liquid, and then the mixture is concentrated by vacuum rotary evaporation, and dried at 60°C under vacuum to obtain the cyclodextrin grafted trimethylolpropane-polyethylene glycol monomethyl ether; the mass ratio of boro-trifluoride ether, propylene oxide, trimethylolpropane-polyethylene glycol monomethyl ether and modification solution in the above preparation step is 1:6:100:40;

[0107] Preparation of diol inclusion material:

[0108] (1) LiMn2O4 with a D50 of 3nm is mixed with hydrochloric acid at a molar ratio of LiMn2O4 to HCl of 1:22, and then de-lithiated at 40°C by magnetic stirring for 6h to obtain λ-MnO2; +

[0109] (2) λ-MnO2 and lithium perchlorate are placed in a ball mill and ball milled for 1.6h, and then a polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol with a molecular weight of 6000 is added and mechanically stirred at 110°C for 5h to obtain a diol inclusion material; the mass ratio of λ-MnO2, polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol, and lithium perchlorate in the above preparation step is 0.4:3.5:0.1;

[0110] Preparation of first polymer layer:

[0111] The substrate material is immersed in toluene diisocyanate, mechanically stirred, and then dried in a vacuum drying oven at 40°C for 25min to obtain a first solid material; then the diol inclusion material is added into the first solid material, mechanically stirred, and then heat polymerized at 120°C for 1h to obtain a pre-modified ternary positive electrode material with a first polymer layer thickness of 25nm; the mass ratio of substrate material, toluene diisocyanate and diol inclusion material in the above preparation step is 1:0.8:1.1;

[0112] Preparation of second polymer layer:

[0113] The pre-modified ternary positive electrode material is immersed in L-lysine ethyl ester diisocyanate again, mechanically stirred, and then dried in a vacuum drying oven at 80°C for 6min to obtain a second solid material; then the modified diol is added into the second solid material, and a wet film with a thickness of 25μm is obtained by spin coating with a spin coater, and then dried at 110°C for 16min to obtain a modified ternary positive electrode material with a second polymer layer thickness of 15nm; the mass ratio of L-lysine ethyl ester diisocyanate, pre-modified ternary positive electrode material and modified diol in the above preparation step is 2.4:6:0.6. ​

[0114] Example 5

[0115] The preparation steps of the modified ternary positive material for lithium ion batteries are as follows:

[0116] Preparation of the matrix material:

[0117] Take single-crystal ternary precursor Ni 0.7 Co 0.1 Mn 0.2 (OH)2 and lithium hydroxide by mass ratio of 2.74:1, mix them, and then place them in an oxygen-rich atmosphere, heat them to 900 DEG C at a rate of 40 DEG C / h, keep them sintered for 20 h, then reduce them to 600 DEG C at a rate of 200 DEG C / h, keep them for 10 h, then reduce them to room temperature at a rate of 50 DEG C / h, crush them, sieve them, and then obtain a matrix material with D90 of 6.18 μm, D10 of 3.01 μm, and D50 of 4.17 μm;

[0118] Preparation of the modified dihydric alcohol:

[0119] (1) Take γ-cyclodextrin and ammonia water by mass ratio of 1:5, mechanically stir them at 66 DEG C for 4.5 h to prepare a modification solution;

[0120] (2) Mix boron trifluoride ether, propylene oxide, and trimethylolpropane-polyethylene glycol monomethyl ether with a molecular weight of 3000, and then react them at 60 DEG C for 2 h to obtain a first reactant; then drop the modification solution into the first reactant, continue to heat them to 100 DEG C for 8 h to obtain a second reactant; take the supernatant of the second reactant, add anhydrous ethanol to the supernatant, and then concentrate them by vacuum rotary evaporation, and then place them in a vacuum dryer at 72 DEG C to prepare cyclodextrin grafted trimethylolpropane-polyethylene glycol monomethyl ether; in the above preparation steps, the mass ratio of boron trifluoride ether, propylene oxide, trimethylolpropane-polyethylene glycol monomethyl ether, and the modification solution is 1:8:200:50;

[0121] Preparation of the dihydric alcohol inclusion material:

[0122] (1) Mix LiMn2O4 with a D50 of 5 nm and hydrochloric acid according to a molar ratio of LiMn2O4 to H + Cl of 1:24, and then de-lithiate them at 85 DEG C by magnetic stirring for 9 h to obtain λ-MnO2;

[0123] (2) Place λ-MnO2 and lithium perchlorate in a ball mill, and then ball mill them for 2 h, and then mechanically stir them at 120 DEG C for 6 h with polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol with a molecular weight of 8000 to obtain a dihydric alcohol inclusion material; in the above preparation steps, the mass ratio of λ-MnO2, polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol, and lithium perchlorate is 0.5:5:0.1;

[0124] Preparation of the first polymer layer:

[0125] The base material is immersed in isophorone diisocyanate, dried in a vacuum drying oven at 40°C for 24 min after mechanical stirring to obtain a first solid material; the binary alcohol inclusion material is added to the first solid material, and a first polymer layer of a pre-modified ternary positive electrode material with a thickness of 12 nm is prepared after 2 h of thermal polymerization at 140°C with mechanical stirring; the mass ratio of the base material, isophorone diisocyanate, and binary alcohol inclusion material in the above preparation steps is 1:0.9:1.2;

[0126] Second polymer layer preparation:

[0127] The pre-modified ternary positive electrode material is again immersed in L-lysine ethyl ester diisocyanate, dried in a vacuum drying oven at 64°C for 8 min after mechanical stirring to obtain a second solid material; the modified binary alcohol is added to the second solid material, and a second polymer layer of a modified ternary positive electrode material with a thickness of 36 nm is prepared after spin coating with a spin coater to obtain a wet film with a thickness of 30 μm and drying at 120°C for 20 min; the mass ratio of L-lysine ethyl ester diisocyanate, pre-modified ternary positive electrode material, and modified binary alcohol in the above preparation steps is 3:6:0.8.

[0128] Test method:

[0129] 1. Strength and ductility test: The second polymer obtained in the examples and comparative examples is cut into a dumbbell-shaped test film piece with a size of 30 mm x 6 mm after heat treatment at 120°C to form a film, and a CMT6104-intelligent electronic tensile testing machine from Shenzhen Xinsisi Material Testing Co., Ltd. is used for testing at a tensile rate of 200 mm / min.

[0130] 2. Powder resistance test: The ternary positive electrode material prepared in the examples and comparative examples is tested using a four-electrode powder resistance meter.

[0131] 3. Electrical performance test: The positive electrode material obtained in the examples and comparative examples, the conductive agent SP, and the binder PVDF are mixed in a mass ratio of 95:3:2, and NMP is used as the solvent to prepare an electrode piece, which is coated on a carbon-coated aluminum foil, dried at 100°C for 5 h, and compacted on a rolling machine. A lithium metal sheet is used as the negative electrode, a 1M LiPF6 solution is used as the electrolyte, and cellgard2300 is used as the separator. A button cell is assembled with the above positive electrode, and a 50-week charge-discharge test is performed at -30°C, a cutoff voltage of 3.0-4.25V, and a 3C rate.

[0132] 4. Micro-morphology characterization: The positive electrode material obtained in Example 1 and Comparative Example 1 is taken out after the above electrical performance test, washed with dimethyl sulfoxide, and its cross section is taken. The cross section electrode piece is photographed with the same magnification, and the results are shown in Figure 1 and Figure 2 .

[0133] The results of the above tests are shown in Table 1.

[0134] Table 1

[0135]

[0136]

[0137] From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects:

[0138] From the micro-morphology of Figure 1 and Figure 2 It can be seen that after 50 cycles of charge and discharge at -30°C and 3C, the particles of the positive electrode material prepared in Example 1 are complete, the edges are round and there is no damage, while the particles prepared in Comparative Example 1 show obvious pulverization and cracking.

[0139] Comparing the test results of Comparative Examples 1-5 and Comparative Example 1, it can be seen that the capacity retention rate of the modified ternary positive electrode material of the present application at 3C is 96.4-97.1%, and the powder resistance is much lower than that of Comparative Example 1, showing excellent electrical performance at low temperature (-30°C) and high rate.

[0140] Comparing Examples 1-5 and Comparative Example 2, it can be seen that Examples 1-5 have excellent capacity retention rate at low temperature and high rate, which is much higher than 74.3% of Comparative Example 2, which is entirely because the second polymer coating layer coated on the surface of Examples 1-5 has excellent ductility, with a mechanical strength of more than 5 MPa and an elongation at break of more than 1000%, which effectively inhibits the crystal expansion of the positive electrode material at high rate charge and discharge, stabilizes the crystal structure, and improves the capacity decay problem of the positive electrode material at high rate charge and discharge.

[0141] Comparing Examples 1-5 and Comparative Example 3, it can be seen that the three-dimensional superconducting network structure provided by the first polymer coating layer improves the solid-phase diffusion speed of the positive electrode material at low temperature, effectively optimizes the interface performance, reduces the lithium deposition speed at low temperature, and Examples 1-5 have extremely low powder resistivity and capacity retention rate at high rate, which is much higher than that of Comparative Example 3.

[0142] In summary, by coating a first polymer layer / second polymer layer multi-layer structure on the surface of the nickel-cobalt-manganese lithium-based material, the problems of crystal structure collapse caused by crystal expansion of the nickel-cobalt-manganese lithium ternary material, lithium deposition at low temperature and high rate, and low ion solid-phase diffusion are effectively solved, and excellent charge and discharge performance of the battery at low temperature and high rate is achieved.

[0143] The above merely provides the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the scope of the present application.

Claims

1. A method for preparing a ternary cathode material, characterized in that, The method comprises the following steps: S1, mixing precursor Ni a Co b Mn 1-a-b (OH)2 with lithium hydroxide, and then performing sintering treatment to obtain a base material; wherein 0.7≤a<1, 0<b<0.

2. S2, boron trifluoride ether, propylene oxide and trimethylolpropane-polyethylene glycol monomethyl ether are subjected to a first reaction to obtain a first reactant; a modification solution and the first reactant are subjected to a second reaction to obtain a second reactant; the second reactant is subjected to solid-liquid separation and drying of the clear liquid to obtain a modified diol; wherein the modification solution is a mixture of a cyclodextrin and an alkali solution; S3, a mixture of λ-MnO2 and a lithium source is used as a core layer, and a polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol is used to coat the surface of the core layer to obtain a diol inclusion material; S4, the base material is mixed with a first isocyanate, and after first drying, a first solid material is obtained; then the diol inclusion material is subjected to a first polymerization reaction with the first solid material to obtain a pre-modified ternary positive electrode material; S5, the pre-modified ternary positive electrode material is mixed with a second isocyanate, and after second drying, a second solid material is obtained; the modified diol is subjected to a second polymerization reaction with the second solid material to obtain the ternary positive electrode material.

2. The production method according to claim 1, characterized by, The S1 comprises mixing the precursor Ni a Co b Mn 1-a-b (OH)2 with the lithium hydroxide, and then performing a sintering treatment under an oxygen-rich atmosphere, and then crushing and sieving to obtain the base material; wherein the oxygen content of the oxygen-rich atmosphere is ≥ 93 vol%.

3. The preparation method according to claim 2, wherein the particle size test value of the base material satisfies (D90-D10) / D50≤1.6; and the sintering treatment comprises a temperature rising stage, a first holding stage, a first temperature dropping stage, a second holding stage and a second temperature dropping stage in sequence.

5. The preparation method according to claim 4, wherein the temperature rising rate of the temperature rising stage is 10-40℃ / h; the temperature of the first holding stage is 750-900℃, and the time of the first holding stage is 15-20h; the temperature dropping rate of the first temperature dropping stage is 100-200℃ / h; the temperature of the second holding stage is 400-600℃, and the time of the second holding stage is 5-10h; and the temperature dropping rate of the second temperature dropping stage is 10-50℃ / h. said precursor Ni a Co b Mn 1-a-b the weight ratio of said (OH)2to said lithium hydroxide is 2.02 to 2.74:

1.

4. The production method according to claim 1 or 2, characterized by, The weight ratio of the boron trifluoride ether, the propylene oxide and the trimethylolpropane-polyethylene glycol monomethyl ether is 1:2-8:50-200; and the weight ratio of the boron trifluoride ether and the modification solution is 1:20-50. The average molecular weight of the trimethylolpropane-polyethylene glycol monomethyl ether is 500-3000. The temperature of the first reaction is 40-60℃, and the time is 1-2h; and the temperature of the second reaction is 80-100℃, and the time is 4-8h. The modification solution is obtained by mixing the cyclodextrin and the alkali solution according to a weight ratio of 1:3-9; the mixing temperature is 60-80℃, and the time is 3-6h; the cyclodextrin is one or more of α-cyclodextrin, β-cyclodextrin and γ-cyclodextrin; the alkali solution is aqueous ammonia and / or aqueous sodium hydroxide solution; the mass concentration of the alkali solution is 15-45wt%; and the step of drying the clear liquid is vacuum rotary evaporation concentration after adding anhydrous ethanol to the clear liquid, followed by vacuum drying at 50-80℃. ​ ​ ​ 6. The production method according to claim 1 or 2, characterized by, ​ 7. The production method according to claim 1 or 2, characterized by, ​ 8. The production method according to claim 1 or 2, characterized by, ​ 9. The production method according to claim 1 or 2, characterized by, ​ 10. The production method according to claim 1 or 2, characterized by, The weight ratio of the λ-MnO2 and the lithium source is 0.3-0.5:0.1; the weight ratio of the λ-MnO2 and the polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol is 0.3-0.5:3-5; the average molecular weight of the polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol is 1000-8000; and the lithium source is lithium perchlorate and / or lithium bis(trifluoromethanesulfonyl)imide.

11. The production method according to claim 1 or 2, characterized by, The λ-MnO2 is prepared by mixing LiMn2O4 and hydrochloric acid in a molar ratio of LiMn2O4 to H + Cl of 1:18-24, and then performing a delithiation treatment to obtain the λ-MnO2; wherein the D50 of the LiMn2O4 is 1-5 nm.

12. The method of claim 11, wherein, The delithiation treatment is performed at 30-100℃ for 1-10h.

13. The production method according to claim 1 or 2, characterized by, The weight ratio of the base material and the first isocyanate is 1:0.3-0.9; the weight ratio of the first isocyanate and the diol inclusion is 0.3-0.9:1-1.2; the first isocyanate is toluene diisocyanate and / or isophorone diisocyanate; and the first drying is performed in a vacuum drying oven at a drying temperature of 40-60℃ for 15-30min.

14. The production method according to claim 1 or 2, characterized by, The weight ratio of the second isocyanate and the pre-modified ternary cathode material is 1-3:6; the weight ratio of the second isocyanate and the modified diol is 1-3:0.5-0.8; the second isocyanate is L-lysine ethyl ester diisocyanate; and the second drying is performed in a vacuum drying oven at a drying temperature of 50-80℃ for 5-10min.

15. The production method according to claim 1 or 2, characterized by, The S3 comprises: ball milling the λ-MnO2 and the lithium source, and then stirring the λ-MnO2, the lithium source and the polycarbonate diol copolymer of 1,5-pentanediol and 1,6-hexanediol at 100-120℃ for 4-6h.

16. The method of making according to claim 1 or 2, wherein, The temperature of the first polymerization reaction is 110-140℃, and the time is 1-2h; a first polymer layer is obtained on the surface of the base material by the first polymerization reaction, and the thickness of the first polymer layer is 10-30nm.

17. The method of making according to claim 1 or 2, wherein, The temperature of the second polymerization reaction is 100-120℃, and the time is 10-20min.

18. The method of claim 17, wherein, After mixing the modified diol and the second solid, spin coating is performed to obtain a wet film for the second polymerization reaction; the thickness of the wet film is 10-30μm; a second polymer layer is obtained on the surface of the pre-modified ternary cathode material by the second polymerization reaction, and the thickness of the second polymer layer is 15-40nm.

19. A ternary cathode material prepared by the preparation method according to any one of claims 1-18.

20. A lithium-ion battery, characterized by, The ternary cathode material according to claim 19.

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