High-voltage system positive electrode material and preparation method thereof

Abstract

The invention discloses a high-voltage system positive electrode material and a preparation method thereof. The preparation method of the high-voltage system positive electrode material comprises the following steps: S1, adding tartaric acid into a solution A containing a lithium source A, a nickel source, a manganese source and water, and heating for reaction to obtain gel; s2, sintering the gel for the first time to obtain a base material; s3, mixing a solution B containing a lithium source B, a lanthanum source, a titanium source and a solvent with the base material, heating for reaction, and separating and precipitating after the reaction is finished to obtain a front material; and S4, carrying out secondary sintering on the preposed material to obtain the high-voltage system positive electrode material. The high-voltage system positive electrode material contains LiNi0. 5Mn1. 5O4 (LNMO), and is coated with Li0. 33La0. 56TiO3, so that the surface ionic conductivity of particles of the LNMO material can be improved, the dissolution of transition metal ions is reduced, and the generation of a stable positive electrode-electrolyte interface (CEI) film is promoted, so that the high-voltage system positive electrode material can maintain an excellent cycle capacity retention rate under high voltage.

Description

Technical Field

[0001] The present invention relates to the field of lithium ion battery positive electrode materials, and in particular to a high voltage system positive electrode material and a preparation method thereof. Background Art

[0002] As a new type of energy storage device, lithium-ion batteries have higher energy density and operating voltage, longer service life and lower environmental pollution than traditional secondary batteries. As the electric vehicle market's demand for lithium-ion batteries' energy density and power density increases, the cobalt-free spinel cathode material LiNi 0.5 Mn 1.5 O4 (LNMO) is considered to be one of the candidates for the next generation of lithium-ion battery cathode materials due to its theoretical energy density of 650 Wh / kg and high output voltage. However, LNMO will experience transition metal dissolution and electrolytic decomposition during high voltage charging and discharging, thereby forming an unstable cathode-electrolyte interphase (CEI), which increases battery impedance and hinders ion transport. The capacity of LNMO decays rapidly at high voltage and high temperature. How to reduce the dissolution of transition metal ions, promote the formation of a stable cathode-electrolyte interface (CEI) film, and enable LNMO to maintain excellent cycle capacity retention at high voltage is still a technical problem that needs to be solved urgently. Summary of the invention

[0003] The purpose of the present invention is to provide a high-voltage system positive electrode material and a preparation method thereof. By preparing the LNMO@LLTO positive electrode material, the surface ionic conductivity of the LNMO material particles can be improved, the dissolution of transition metal ions can be reduced, and the formation of a stable positive electrode-electrolyte interface film (CEI) film can be promoted, so that it can maintain an excellent cycle capacity retention rate under high voltage.

[0004] In a first aspect, the present invention provides a method for preparing a high voltage system positive electrode material, comprising the following steps: S1, adding tartaric acid to a solution A containing a lithium source A, a nickel source, a manganese source and water, heating to react, and obtaining a gel; S2, sintering the gel for the first time to obtain a base material; S3, mixing the solution B containing the lithium source B, the lanthanum source, the titanium source and the solvent with the base material, heating to react, and separating and precipitating after the reaction is completed to obtain the pre-material; S4, sintering the pre-material for a second time to obtain the high voltage system positive electrode material.

[0005] Based on the above technical scheme, the present invention first prepares LNMO material, and then coats LLTO on the surface of the LNMO material to obtain LNMO@LLTO positive electrode material. Due to the coating of LLTO, the positive electrode material of the present invention can maintain excellent cycle capacity retention rate under high voltage, and the cycle performance at high rate and high temperature is better than that of the uncoated LNMO material.

[0006] In the above-mentioned method for preparing the positive electrode material of the high voltage system, as an example, the solution A is composed of a lithium source A, a nickel source, a manganese source and water; The lithium source A is a water-soluble organic lithium salt, preferably one or more of lithium acetate and its hydrate, lithium formate and its hydrate, lithium oxalate and its hydrate, lithium citrate and its hydrate, lithium lactate and its hydrate; The nickel source is a water-soluble organic nickel salt, preferably one or more of nickel acetate and its hydrate, nickel formate and its hydrate, nickel citrate and its hydrate, lithium lactate and its hydrate; The manganese source is a water-soluble organic manganese salt, preferably one or more of manganese acetate and its hydrate, manganese formate and its hydrate, manganese citrate and its hydrate, and manganese lactate and its hydrate; The lithium source A, the nickel source and the manganese source are added according to the metal element molar ratio of Li:Ni:Mn=(1-1.05):0.5:1.5, such as 1:0.5:1.5, 1.01:0.5:1.5, 1.02:0.5:1.5, 1.03:0.5:1.5, 1.04:0.5:1.5, 1.05:0.5:1.5; The molar concentration of lithium ions in the solution A is 2 to 6 mol / L, such as 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, and 6 mol / L.

[0007] In the above-mentioned method for preparing the positive electrode material of the high voltage system, the molar ratio of the tartaric acid to the sum of the metal ions (Li+Ni+Mn) in the solution A is (1.5-2.5):1, such as 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1; The heating temperature in step S1 is 80-95°C, such as 80°C, 85°C, 90°C, 95°C; The reaction in step S1 is carried out under stirring, and the reaction time is 3 to 6 hours, such as 3 hours, 4 hours, 5 hours, or 6 hours.

[0008] In the above-mentioned method for preparing the positive electrode material of the high voltage system, the first sintering is carried out in three stages, and the temperature and holding time of each stage are as follows: The temperature of the first stage is 260-300°C (such as 260°C, 270°C, 280°C, 290°C, 300°C), and the time is 8-12h (such as 8h, 9h, 10h, 11h, 12h); The temperature of the second stage is 400-600°C (such as 400°C, 450°C, 500°C, 550°C, 600°C), and the time is 2-7h (such as 2h, 3h, 4h, 5h, 6h, 7h); The temperature of the third stage is 700-1000°C (such as 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C), and the time is 10-15h (such as 10h, 11h, 12h, 13h, 14h, 15h); The first sintering may be specifically 280°C / 8h~500°C / 5h~900°C / 12h, 260°C / 10h~450°C / 6h~800°C / 15h, 290°C / 12h~550°C / 4h~950°C / 10h, 270°C / 9h~600°C / 6h~1000°C / 10h or 280°C / 9h~400°C / 4h~700°C / 15h; The heating rate of the first sintering is 1-4°C / min, such as 1°C / min, 2°C / min, 3°C / min, 4°C / min; The first sintering atmosphere is air atmosphere; The method in step S2 further comprises the step of crushing the sintered product after the first sintering.

[0009] In the above-mentioned method for preparing the high voltage system positive electrode material, the base material contains LiNi 0.5 Mn 1.5 O4 (LNMO).

[0010] In the above-mentioned method for preparing the positive electrode material of the high voltage system, as an example, the solution B is composed of a lithium source B, a lanthanum source, a titanium source and a solvent; The solvent is ethanol; The lithium source B is an alcohol-soluble lithium salt, preferably one or more of lithium hydroxide, lithium nitrate, lithium chloride, and lithium ethoxide; The lanthanum source is an alcohol-soluble lanthanum salt, preferably one or more of lanthanum nitrate and lanthanum chloride; The titanium source is an alcohol-soluble titanium salt, preferably tetrabutyl titanate (titanium tetra-n-butoxide); The lithium source B, the lanthanum source and the titanium source are added according to a metal element molar ratio of Li:La:Ti=(0.3-0.35):0.56:1, such as 0.3:0.56:1, 0.31:0.56:1, 0.32:0.56:1, 0.33:0.56:1, 0.34:0.56:1, 0.35:0.56:1; The molar concentration of lithium ions in the solution B is 1-4 mol / L, such as 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L.

[0011] In the above-mentioned method for preparing the positive electrode material of the high voltage system, the mass of the Ti element in the solution B is 0.5% to 1% of the mass of the base material, such as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%; The heating temperature in step S3 is 150-200° C., such as 150° C., 160° C., 170° C., 180° C., 190° C., 200° C.; The reaction in step S3 is carried out under stirring, and the reaction time is 12 to 18 hours, such as 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, and 18 hours.

[0012] In the above-mentioned method for preparing the positive electrode material of the high voltage system, the temperature of the second sintering is 450-550°C (such as 450°C, 500°C, 550°C), the time is 2-5h (such as 2h, 3h, 4h, 5h), and the heating rate is 1-4°C / min (such as 1°C / min, 2°C / min, 3°C / min, 4°C / min); The atmosphere of the second sintering is an air atmosphere; The method in step S4 further comprises the step of crushing the sintered product after the second sintering.

[0013] In the above-mentioned method for preparing a high voltage system positive electrode material, the high voltage system positive electrode material comprises Li 0.33 La 0.56 TiO3 coated LiNi 0.5 Mn 1.5 O4 (LNMO@LLTO).

[0014] In a second aspect, the present invention provides a high voltage system positive electrode material prepared by any of the preparation methods described above.

[0015] In a third aspect, the present invention provides a lithium-ion battery, comprising a positive electrode plate, wherein the positive electrode plate comprises the high-voltage system positive electrode material.

[0016] In the above-mentioned lithium-ion battery, as a test example, the lithium-ion battery is a CR2032 button battery; The positive electrode sheet includes a current collector and a positive electrode material on the current collector, the current collector may be a carbon-coated aluminum foil, and the slurry may be composed of a positive electrode material (90wt%), Super P (5wt%) and PVDF (5wt%) (in the form of NMP solution); The lithium-ion battery further includes an electrolyte, which may be a high-voltage electrolyte of 1.0M LiTFSI EC / DMC / FEC (volume ratio 2:7:1); The lithium-ion battery further comprises a negative electrode plate, and the negative electrode plate can be specifically made of lithium metal; The lithium-ion battery further comprises a separator, and the separator may specifically be a PE film.

[0017] The present invention has the following beneficial effects: The high voltage system positive electrode material of the present invention contains LiNi 0.5 Mn 1.5 O4 (LNMO), and coated with Li 0.33 La 0.56 TiO3 can improve the surface ionic conductivity of LNMO material particles, reduce the dissolution of transition metal ions, and promote the formation of a stable cathode-electrolyte interface (CEI) film, which can maintain a good capacity retention rate during cycling at high rates and high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the XRD diagram of the high voltage system positive electrode material prepared in Example 1 of the present invention.

[0019] Figure 2 This is the Raman spectrum of the high voltage system positive electrode material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below in conjunction with specific embodiments, and the examples provided are only for illustrating the present invention, rather than for limiting the scope of the present invention. The examples provided below can be used as a guide for further improvements by those of ordinary skill in the art, and do not constitute a limitation of the present invention in any way.

[0021] The methods used in the following examples, unless otherwise specified, are all conventional methods, carried out according to the techniques or conditions described in the literature in the art or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial sources.

[0022] Example 1. Preparation and characterization of positive electrode materials for high voltage systems Prepare the high voltage system cathode material according to the following steps: 1. Prepare CH3COOLi·2H2O into a 2 mol / L aqueous solution of lithium ions, add Ni(CH3COO)2·4H2O and Mn(CH3COO)2·6H2O (final concentration of nickel ions is 0.98 mol / L, final concentration of manganese ions is 2.94 mol / L) at a molar ratio of Li:Ni:Mn=1.02:0.5:1.5, and stir until completely dissolved to obtain solution A; 2. Add tartaric acid (final concentration of 11.84 mol / L) to solution A obtained in step 1 at a molar ratio of tartaric acid to the sum of metal ions in solution A of 2:1, heat at 90°C and stir for 4 hours to obtain a gel; 3. The gel obtained in step 2 is sintered for the first time in an air atmosphere at 280°C / 8h~500°C / 5h~900°C / 12h (divided into three stages) and a heating rate of 2°C / min. The sintered product is crushed to obtain a base material; 4. Prepare LiNO3 into a 1 mol / L lithium ion ethanol solution, add La(NO3)3 and Ti(C4H9O)4 (the final concentration of lanthanum ion is 1.65 mol / L, and the final concentration of titanium ion is 2.94 mol / L) at a molar ratio of Li:La:Ti=0.34:0.56:1, and stir until completely dissolved to obtain solution B; 5. Solution B is mixed with the base material obtained in step 3 so that the mass of Ti element in solution B accounts for 0.6% of the mass of the base material, stirred and heated at 180°C / 15h, and then separated and precipitated to obtain the pre-material; 6. The pre-material obtained in step 5 is subjected to a second sintering in an air atmosphere at 500°C / 2h and a heating rate of 2°C / min. The sintered product is crushed to obtain the high voltage system positive electrode material.

[0023] The XRD pattern of the obtained high voltage system positive electrode material is shown in Figure 1 , it can be seen that it contains LNMO.

[0024] The Raman spectrum of the obtained high voltage system cathode material is shown in Figure 2 , it can be seen that it contains LLTO (Li 0.33 La 0.56 TiO3).

[0025] Example 2: Preparation of positive electrode materials for high voltage systems Prepare the high voltage system cathode material according to the following steps: 1. Prepare a 3 mol / L aqueous solution of lithium ions with Li2C2O4·4H2O, add Ni(CH3CH(OH)COO)2·2H2O and Mn(CH3COO)2·6H2O (final concentration of nickel ions is 1.5 mol / L, final concentration of manganese ions is 4.5 mol / L) at a molar ratio of Li:Ni:Mn=1:0.5:1.5, and stir until completely dissolved to obtain solution A; 2. Add tartaric acid (final concentration 7.5 mol / L) to solution A obtained in step 1 at a molar ratio of tartaric acid to the sum of metal ions in solution A of 1.5:1, heat to 85°C and stir for 5 hours to obtain a gel; 3. The gel obtained in step 2 is sintered for the first time in an air atmosphere at 260°C / 10h~450°C / 6h~800°C / 15h (divided into three stages) and a heating rate of 4°C / min. The sintered product is crushed to obtain a base material; 4. Prepare LiCl into a 2 mol / L lithium ion ethanol solution, add La(NO3)3 and Ti(C4H9O)4 (the final concentration of lanthanum ion is 3.61 mol / L, and the final concentration of titanium ion is 6.45 mol / L) at a molar ratio of Li:La:Ti=0.31:0.56:1, and stir until completely dissolved to obtain solution B; 5. Solution B is mixed with the base material obtained in step 3 so that the mass of Ti element in solution B accounts for 0.5% of the mass of the base material, stirred and heated at 150°C / 16h, and then separated and precipitated to obtain the pre-material; 6. The pre-processed material obtained in step 5 is subjected to a second sintering in an air atmosphere at 500°C / 3h and a heating rate of 1°C / min. The sintered product is crushed to obtain the high voltage system positive electrode material.

[0026] Example 3: Preparation of positive electrode materials for high voltage systems Prepare the high voltage system cathode material according to the following steps: 1. Prepare HCOOLi·H2O into a 4 mol / L aqueous solution of lithium ions, add Ni(HCOO)2·2H2O and Mn(HCOO)2·2H2O (final concentration of nickel ions is 1.98 mol / L, final concentration of manganese ions is 5.94 mol / L) at a molar ratio of Li:Ni:Mn=1.01:0.5:1.5, and stir until completely dissolved to obtain solution A; 2. Add tartaric acid (final concentration: 25.03 mol / L) to solution A obtained in step 1 at a molar ratio of tartaric acid to the sum of metal ions in solution A of 2.1:1, heat at 95°C and stir for 3 hours to obtain a gel; 3. The gel obtained in step 2 is sintered for the first time in an air atmosphere at 290°C / 12h~550°C / 4h~950°C / 10h (divided into three stages) and a heating rate of 2°C / min. The sintered product is crushed to obtain a base material; 4. Prepare LiOH into a 1 mol / L lithium ion ethanol solution, add LaCl3 and Ti(C4H9O)4 (the final concentration of lanthanum ions is 1.70 mol / L, and the final concentration of titanium ions is 3.03 mol / L) at a molar ratio of Li:La:Ti=0.33:0.56:1, and stir until completely dissolved to obtain solution B; 5. Solution B is mixed with the base material obtained in step 3 according to the mass of Ti element in solution B accounting for 0.8% of the mass of the base material, stirred and heated at 190°C / 14h, and then separated and precipitated to obtain the pre-material; 6. The pre-processed material obtained in step 5 is subjected to a second sintering in an air atmosphere at 450°C / 5h and a heating rate of 3°C / min. The sintered product is crushed to obtain the high voltage system positive electrode material.

[0027] Example 4: Preparation and performance testing of positive electrode materials for high voltage systems Prepare the high voltage system cathode material according to the following steps: 1. Prepare C6H5O7Li3·4H2O into a 3 mol / L aqueous solution of lithium ions, add (C6H5O7)2Ni3·H2O and (C6H5O7)2Mn3·10H2O (final concentration of nickel ions is 1.43 mol / L, final concentration of manganese ions is 4.29 mol / L) at a molar ratio of Li:Ni:Mn=1.05:0.5:1.5, stir until completely dissolved, and obtain solution A; 2. Add tartaric acid (final concentration of 21.8 mol / L) to the solution A obtained in step 1 at a molar ratio of tartaric acid to the sum of metal ions in solution A of 2.5:1, heat at 90°C and stir for 6 hours to obtain a gel; 3. The gel obtained in step 2 is sintered for the first time in an air atmosphere at 270°C / 9h~600°C / 6h~1000°C / 10h (divided into three stages) and a heating rate of 4°C / min. The sintered product is crushed to obtain a base material; 4. Prepare C2H5OLi into a 4 mol / L lithium ion ethanol solution, add LaCl3 and Ti(C4H9O)4 (the final concentration of lanthanum ion is 6.4 mol / L, and the final concentration of titanium ion is 11.43 mol / L) at a molar ratio of Li:La:Ti=0.35:0.56:1, and stir until completely dissolved to obtain solution B; 5. Solution B is mixed with the base material obtained in step 3 according to the mass of Ti element in solution B accounting for 1% of the mass of the base material, stirred and heated at 200°C / 18h, and then separated and precipitated to obtain the pre-material; 6. The pre-material obtained in step 5 is subjected to a second sintering in an air atmosphere at 550°C / 5h and a heating rate of 4°C / min. The sintered product is crushed to obtain the high voltage system positive electrode material.

[0028] Example 5: Preparation of positive electrode materials for high voltage systems Prepare the high voltage system cathode material according to the following steps: 1. Prepare CH3CH(OH)COOLi into a 5 mol / L aqueous solution of lithium ions, add Ni(CH3CH(OH)COO)2·2H2O and Mn(CH3CH(OH)COO)2 (the final concentration of nickel ions is 2.4 mol / L and the final concentration of manganese ions is 7.21 mol / L) at a molar ratio of Li:Ni:Mn=1.04:0.5:1.5, and stir until completely dissolved to obtain solution A; 2. Add tartaric acid (final concentration of 14.61 mol / L) to solution A obtained in step 1 at a molar ratio of tartaric acid to the sum of metal ions in solution A of 2.5:1, heat at 80°C and stir for 4 hours to obtain a gel; 3. The gel obtained in step 2 is sintered for the first time in an air atmosphere at 280°C / 9h~400°C / 4h~700°C / 15h (divided into three stages) and a heating rate of 1°C / min. The sintered product is crushed to obtain a base material; 4. Prepare LiOH into a 1 mol / L lithium ion ethanol solution, add LaCl3 and Ti(C4H9O)4 (the final concentration of lanthanum ions is 1.75 mol / L, and the final concentration of titanium ions is 3.13 mol / L) at a molar ratio of Li:La:Ti=0.32:0.56:1, and stir until completely dissolved to obtain solution B; 5. Solution B is mixed with the base material obtained in step 3 so that the mass of Ti element in solution B accounts for 0.7% of the mass of the base material, stirred and heated at 160°C / 13h, and then separated and precipitated to obtain the pre-material; 6. The pre-processed material obtained in step 5 is subjected to a second sintering in an air atmosphere at 400°C / 2h and a heating rate of 4°C / min. The sintered product is crushed to obtain the high voltage system positive electrode material.

[0029] Comparative Example 1 1. LiOH·H2O and Ni 0.5 Mn 1.5 (OH)4 was uniformly mixed in a molar ratio of 1.01:1; 2. The mixture obtained in step 1 is sintered in an air atmosphere at 900°C / 12h and a heating rate of 2°C / min. The sintered product is crushed to obtain a conventional LNMO high-voltage system positive electrode material.

[0030] Comparative Example 2 Same as Example 1, steps 4 to 6 are omitted, and the specific steps are as follows: 1. Prepare CH3COOLi·2H2O into a 2 mol / L aqueous solution of lithium ions, add Ni(CH3COO)2·4H2O and Mn(CH3COO)2·6H2O (final concentration of nickel ions is 0.98 mol / L, final concentration of manganese ions is 2.94 mol / L) at a molar ratio of Li:Ni:Mn=1.02:0.5:1.5, and stir until completely dissolved to obtain solution A; 2. Add tartaric acid (final concentration of 11.84 mol / L) to solution A obtained in step 1 at a molar ratio of tartaric acid to the sum of metal ions in solution A of 2:1, heat at 90°C and stir for 4 hours to obtain a gel; 3. The gel obtained in step 2 is sintered for the first time in an air atmosphere at 280°C / 8h~500°C / 5h~900°C / 12h (divided into three stages) and a heating rate of 2°C / min. The sintered product is crushed to obtain the LNMO high-voltage system positive electrode material.

[0031] Comparative Example 3 Same as Example 1, only the coating method of LLTO in steps 4 to 6 is changed, and the specific steps are as follows: 1. Prepare CH3COOLi·2H2O into a 2 mol / L aqueous solution of lithium ions, add Ni(CH3COO)2·4H2O and Mn(CH3COO)2·6H2O (final concentration of nickel ions is 0.98 mol / L, final concentration of manganese ions is 2.94 mol / L) at a molar ratio of Li:Ni:Mn=1.02:0.5:1.5, and stir until completely dissolved to obtain solution A; 2. Add tartaric acid (final concentration of 11.84 mol / L) to solution A obtained in step 1 at a molar ratio of tartaric acid to the sum of metal ions in solution A of 2:1, heat at 90°C and stir for 4 hours to obtain a gel; 3. The gel obtained in step 2 is sintered for the first time in an air atmosphere at 280°C / 8h~500°C / 5h~900°C / 12h (divided into three stages) and a heating rate of 2°C / min. The sintered product is crushed to obtain a base material; 4. Prepare LiNO3 into a 1 mol / L lithium ion ethanol solution, add La(NO3)3 and Ti(C4H9O)4 (the final concentration of lanthanum ion is 1.65 mol / L, and the final concentration of titanium ion is 2.94 mol / L) at a molar ratio of Li:La:Ti=0.34:0.56:1, stir until completely dissolved, then heat the solution until completely evaporated, and grind the obtained solid to obtain the coating material; 5. The base material obtained in step 3 and the coating material obtained in step 4 are ball-milled and mixed, and the sintering conditions are 500°C / 2h and the heating rate is 2°C / min. The sintered product is crushed to obtain the LNMO high-voltage system positive electrode material containing LLTO.

[0032] Comparative Example 4 Same as Example 1, except that the tartaric acid in step 2 is replaced with citric acid, the specific steps are as follows: 1. Prepare CH3COOLi·2H2O into a 2 mol / L aqueous solution of lithium ions, add Ni(CH3COO)2·4H2O and Mn(CH3COO)2·6H2O (final concentration of nickel ions is 0.98 mol / L, final concentration of manganese ions is 2.94 mol / L) at a molar ratio of Li:Ni:Mn=1.02:0.5:1.5, and stir until completely dissolved to obtain solution A; 2. Add tartaric acid (final concentration of 11.84 mol / L) to solution A obtained in step 1 at a molar ratio of citric acid to the sum of metal ions in solution A of 2:1, heat at 90°C and stir for 4 hours to obtain a gel; 3. The gel obtained in step 2 is sintered for the first time in an air atmosphere at 280°C / 8h~500°C / 5h~900°C / 12h (divided into three stages) and a heating rate of 2°C / min. The sintered product is crushed to obtain a base material; 4. Prepare LiNO3 into a 1 mol / L lithium ion ethanol solution, add La(NO3)3 and Ti(C4H9O)4 (the final concentration of lanthanum ion is 1.65 mol / L, and the final concentration of titanium ion is 2.94 mol / L) at a molar ratio of Li:La:Ti=0.34:0.56:1, and stir until completely dissolved to obtain solution B; 5. Solution B is mixed with the base material obtained in step 3 so that the mass of Ti element in solution B accounts for 0.6% of the mass of the base material, stirred and heated at 180°C / 15h, and then separated and precipitated to obtain the pre-material; 6. The pre-material obtained in step 5 is subjected to a second sintering in an air atmosphere at 500°C / 2h and a heating rate of 2°C / min. The sintered product is crushed to obtain a high-voltage system positive electrode material.

[0033] Comparative Example 5 Same as Example 1, only the sintering conditions in step 3 are changed, and the specific steps are as follows: 1. Prepare CH3COOLi·2H2O into a 2 mol / L aqueous solution of lithium ions, add Ni(CH3COO)2·4H2O and Mn(CH3COO)2·6H2O (final concentration of nickel ions is 0.98 mol / L, final concentration of manganese ions is 2.94 mol / L) at a molar ratio of Li:Ni:Mn=1.02:0.5:1.5, and stir until completely dissolved to obtain solution A; 2. Add tartaric acid (final concentration of 11.84 mol / L) to solution A obtained in step 1 at a molar ratio of tartaric acid to the sum of metal ions in solution A of 2:1, heat at 90°C and stir for 4 hours to obtain a gel; 3. The gel obtained in step 2 is subjected to the first sintering in an air atmosphere at 850°C / 10h to 600°C / 5h (in two stages) and a heating rate of 2°C / min. The sintered product is crushed to obtain a base material; 4. Prepare LiNO3 into a 1 mol / L lithium ion ethanol solution, add La(NO3)3 and Ti(C4H9O)4 (the final concentration of lanthanum ion is 1.65 mol / L, and the final concentration of titanium ion is 2.94 mol / L) at a molar ratio of Li:La:Ti=0.34:0.56:1, and stir until completely dissolved to obtain solution B; 5. Solution B is mixed with the base material obtained in step 3 so that the mass of Ti element in solution B accounts for 0.6% of the mass of the base material, stirred and heated at 180°C / 15h, and then separated and precipitated to obtain the pre-material; 6. The pre-material obtained in step 5 is subjected to a second sintering in an air atmosphere at 500°C / 2h and a heating rate of 2°C / min. The sintered product is crushed to obtain a high-voltage system positive electrode material.

[0034] A lithium-ion battery was prepared using the high-voltage positive electrode material obtained from Examples 1-5 and Comparative Examples 1-5 above. The high-voltage positive electrode material (90wt%), Super P (5wt%) and PVDF (5wt%) (NMP solution) were mixed evenly, and then slurried, coated on carbon-coated aluminum foil, dried, and rolled to obtain a positive electrode sheet. The positive electrode sheet, separator (PE base film), and negative electrode sheet (lithium metal) were assembled into a CR2032 button battery, and the electrolyte was 1.0M LiTFSI EC / DMC / FEC (volume ratio 2:7:1), and then left to stand for about 4 hours to obtain a high-voltage positive electrode material lithium-ion battery.

[0035] The lithium-ion batteries made of the high-voltage positive electrode materials obtained in Examples 1-5 and Comparative Example 1 were subjected to charge and discharge cycle tests, and the voltage range was 3.0-4.7V vs. Li / Li + , 1C=140mAh / g. The capacity retention results are shown in Table 1.

[0036] Table 1 Comparison of cycle performance of lithium-ion batteries with high voltage cathode materials

[0037] It can be seen from Table 1 that the LNMO@LLTO in Examples 1-5 prepared by the method of the present invention has better cycle performance at high rates and higher temperatures than the LNMO prepared by the traditional solid phase sintering method in Comparative Example 1. From the comparison results of Example 1 and Comparative Example 2, it can be seen that due to the coating of LLTO, the positive electrode material of the present invention can maintain an excellent cycle capacity retention rate at high voltage, and the cycle performance at high rates and higher temperatures is better than that of the uncoated LNMO material. From the comparison results of Example 1 and Comparative Examples 3-5, it can be seen that the LLTO coating method, the type of organic acid and the sintering conditions in the present invention are more conducive to the cycle performance of the positive electrode material.

[0038] The present invention has been described in detail above. For those skilled in the art, without departing from the purpose and scope of the present invention, can implement the present invention in a wider range under equivalent parameters, concentrations and conditions. Although the present invention provides specific embodiments, it should be understood that the present invention can be further improved. In a word, according to the principle of the present invention, the application is intended to include any changes, uses or improvements to the present invention, including departing from the disclosed scope in the application and the changes made with conventional techniques known in the art.

Claims

1. A method for preparing a high voltage system positive electrode material, characterized in that: The steps include: S1, adding tartaric acid to a solution A containing a lithium source A, a nickel source, a manganese source and water, heating to react, and obtaining a gel; S2, sintering the gel for the first time to obtain a base material; S3, mixing the solution B containing the lithium source B, the lanthanum source, the titanium source and the solvent with the base material, heating to react, and separating and precipitating after the reaction is completed to obtain the pre-material; S4, sintering the pre-material for a second time to obtain the high voltage system positive electrode material.

2. The method for preparing a high voltage system positive electrode material according to claim 1, characterized in that: The lithium source A is a water-soluble organic lithium salt, preferably one or more of lithium acetate and its hydrate, lithium formate and its hydrate, lithium oxalate and its hydrate, lithium citrate and its hydrate, lithium lactate and its hydrate; The nickel source is a water-soluble organic nickel salt, preferably one or more of nickel acetate and its hydrate, nickel formate and its hydrate, nickel citrate and its hydrate, lithium lactate and its hydrate; The manganese source is a water-soluble organic manganese salt, preferably one or more of manganese acetate and its hydrate, manganese formate and its hydrate, manganese citrate and its hydrate, and manganese lactate and its hydrate; The lithium source A, the nickel source and the manganese source are added according to the metal element molar ratio of Li:Ni:Mn=(1-1.05):0.5:1.5; The molar concentration of lithium ions in the solution A is 2-6 mol / L.

3. The method for preparing a high voltage system positive electrode material according to claim 1, characterized in that: The molar ratio of the tartaric acid to the sum of the metal ions (Li+Ni+Mn) in the solution A is (1.5-2.5):1; The heating temperature in step S1 is 80-95°C; The reaction in step S1 is carried out under stirring conditions, and the reaction time is 3 to 6 hours.

4. The method for preparing a high voltage system positive electrode material according to claim 1, characterized in that: The first sintering is carried out in three stages, and the temperature and holding time of each stage are as follows: The first stage temperature is 260-300℃ and the time is 8-12h; The second stage temperature is 400-600℃ and the time is 2-7h; The third stage temperature is 700-1000℃ and the time is 10-15h; The heating rate of the first sintering is 1-4°C / min; The first sintering atmosphere is air atmosphere; The method in step S2 further comprises the step of crushing the sintered product after the first sintering.

5. The method for preparing a high voltage system positive electrode material according to claim 1, characterized in that: The solvent is ethanol; The lithium source B is an alcohol-soluble lithium salt, preferably one or more of lithium hydroxide, lithium nitrate, lithium chloride, and lithium ethoxide; The lanthanum source is an alcohol-soluble lanthanum salt, preferably one or more of lanthanum nitrate and lanthanum chloride; The titanium source is an alcohol-soluble titanium salt, preferably tetrabutyl titanate; The lithium source B, the lanthanum source and the titanium source are added according to the metal element molar ratio of Li:La:Ti=(0.3-0.35):0.56:1; The molar concentration of lithium ions in the solution B is 1-4 mol / L.

6. The method for preparing a high voltage system positive electrode material according to claim 1, characterized in that: The mass of the Ti element in the solution B is 0.5% to 1% of the mass of the base material; The heating temperature in step S3 is 150-200°C; The reaction in step S3 is carried out under stirring conditions, and the reaction time is 12 to 18 hours.

7. The method for preparing a high voltage system positive electrode material according to claim 1, characterized in that: The second sintering temperature is 450-550°C, the time is 2-5h, and the heating rate is 1-4°C / min; The atmosphere of the second sintering is an air atmosphere; The method in step S4 further comprises the step of crushing the sintered product after the second sintering.

8. The method for preparing a high voltage cathode material according to claim 1, characterized in that: The high voltage system positive electrode material comprises Li 0.33 La 0.56 TiO3 coated LiNi 0.5 Mn 1.5 O4.

9. A high voltage system positive electrode material, characterized in that: The method is prepared according to any one of claims 1 to 8.

10. A lithium ion battery, characterized in that: It comprises a positive electrode plate, wherein the positive electrode plate comprises the high voltage system positive electrode material according to claim 9.

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