Aluminum-doped lithium titanate-coated ternary positive electrode material, preparation method and application thereof

Abstract

The application relates to an aluminum-doped lithium titanate-coated ternary positive electrode material and a preparation method and application thereof. The preparation method comprises the following steps: adding metal salt solution, precipitant solution and complexing agent solution into a bottom liquid in parallel flow, and performing a coprecipitation reaction under stirring conditions; after the coprecipitation reaction is completed, the temperature and stirring speed are kept unchanged, aluminum-titanium solution, precipitant solution and ammonia solution are continuously mixed in parallel flow, and a spherical hydroxide is obtained after the reaction is completed; solutes in the aluminum-titanium solution include aluminum salt, titanium salt and hydrogen peroxide; a lithium source is mixed with the spherical hydroxide, and preheating treatment and heat treatment are sequentially performed to obtain the aluminum-doped lithium titanate-coated ternary positive electrode material. The preparation method adds the aluminum-titanium solution in the coprecipitation reaction process, forms an aluminum-doped lithium titanate precursor, and thus the aluminum-doped lithium titanate-coated ternary positive electrode material is obtained through heat treatment, and the interface stability is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery materials, and particularly relates to a lithium titanate coated with aluminum and a preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries have the advantages of high working voltage, long cycle life, light weight, etc., and have been widely used in consumer electronics and new energy vehicle fields. Among them, the positive electrode material is one of the core components of the lithium ion battery, which limits the energy density, power density and cycle life of the lithium ion battery.

[0003] The three elements of Ni, Co and Mn in the ternary positive electrode material lithium nickel cobalt manganese oxide synergistically cooperate, and the advantages of LiCoO2, LiNiO2 and LiMnO2 three lithium ion battery positive electrode materials are integrated, and the thermal stability is good, the energy density and specific capacity are high, and the raw material cost is low. However, there are defects of cationic disordering and poor structural stability.

[0004] In order to improve the cycle stability and safety of the ternary positive electrode material, a coating layer needs to be arranged on the surface of the ternary positive electrode material to improve the corrosion resistance and reduce the side reaction between the material and the electrolyte. However, due to the volume change of the ternary positive electrode material during the delithiation and lithium intercalation cycle, the separation between the coating material and the ternary positive electrode material is easy to occur after a long cycle, which reduces the coating effect.

[0005] Therefore, it is necessary to provide a lithium titanate coated with aluminum and a preparation method and application thereof which can improve the structural stability. SUMMARY

[0006] The present application aims to provide a lithium titanate coated with aluminum and a preparation method and application thereof, which improves the interface stability by adding an aluminum titanium solution during the coprecipitation reaction to form an aluminum-doped lithium titanate precursor, and then obtaining the lithium titanate coated with aluminum by heat treatment.

[0007] To achieve the purpose of the present application, the following technical solutions are adopted:

[0008] In a first aspect, the present application provides a preparation method of a lithium titanate coated with aluminum, which comprises the following steps:

[0009] (1) adding metal salt solution, precipitant solution and complexing agent solution into the bottom liquid in parallel, and performing coprecipitation reaction under stirring condition;

[0010] (2) After the co-precipitation reaction is completed, the temperature and stirring speed are kept unchanged, the aluminum-titanium solution and the complexing agent solution are continuously mixed in parallel flow, and the spherical-like hydroxide is obtained after the reaction is completed;

[0011] The solutes in the aluminum-titanium solution include aluminum salt, titanium salt and H2O2;

[0012] (3) The lithium source is mixed with the spherical-like hydroxide, and preheating treatment and heat treatment are sequentially performed to obtain the aluminum-doped lithium titanate coated ternary positive electrode material.

[0013] The preparation method provided by the application adds the aluminum-titanium solution in the co-precipitation reaction process, forms an aluminum-doped lithium titanate precursor, and then obtains the aluminum-doped lithium titanate coated ternary positive electrode material through heat treatment, thereby improving the interface stability. After aluminum doping, the lithium titanate has better conductivity, which is more conducive to improving the electrical properties of the material. The introduction of Al-O bonds is also conducive to improving the surface structure stability. The addition of H2O2 is conducive to improving the uniformity of the coating.

[0014] Preferably, the metal salt in the metal salt solution includes nickel salt, cobalt salt and manganese salt, and the molar ratio of nickel, cobalt and manganese satisfies x:y:(1-x-y), wherein 0.2≤x≤0.9 and 0<y≤0.33; and the total concentration of nickel, cobalt and manganese is 2-4 mol / L.

[0015] Illustratively, the nickel salt includes any one or a combination of at least two of nickel nitrate, nickel sulfate or nickel chloride, and typical but non-limiting combinations include a combination of nickel nitrate and nickel sulfate, a combination of nickel sulfate and nickel chloride, a combination of nickel nitrate and nickel chloride, or a combination of nickel nitrate, nickel sulfate and nickel chloride.

[0016] Illustratively, the cobalt salt includes any one or a combination of at least two of cobalt nitrate, cobalt sulfate or cobalt chloride, and typical but non-limiting combinations include a combination of cobalt nitrate and cobalt sulfate, a combination of cobalt sulfate and cobalt chloride, a combination of cobalt nitrate and cobalt chloride, or a combination of cobalt nitrate, cobalt sulfate and cobalt chloride.

[0017] Illustratively, the manganese salt includes any one or a combination of at least two of manganese nitrate, manganese sulfate or manganese chloride, and typical but non-limiting combinations include a combination of manganese nitrate and manganese sulfate, a combination of manganese sulfate and manganese chloride, a combination of manganese nitrate and manganese chloride, or a combination of manganese nitrate, manganese sulfate and manganese chloride.

[0018] Preferably, the complexing agent in the complexing agent solution includes any one or a combination of at least two of ammonia, citric acid or sodium citrate, and typical but non-limiting combinations include a combination of ammonia and citric acid, a combination of citric acid and sodium citrate, a combination of ammonia and sodium citrate, or a combination of ammonia, citric acid and sodium citrate.

[0019] Preferably, the molar concentration of aluminum in the aluminum-titanium solution of step (2) is 0.035-0.05 mol / L, for example, it can be 0.035 mol / L, 0.04 mol / L, 0.045 mol / L or 0.05 mol / L, but is not limited to the listed values, and the remaining values in the range are also applicable.

[0020] Preferably, the molar concentration of titanium in the aluminum-titanium solution of step (2) is 0.15-0.18 mol / L, for example, it can be 0.15 mol / L, 0.16 mol / L, 0.17 mol / L or 0.18 mol / L, but is not limited to the listed values, and the remaining values in the range are also applicable.

[0021] Preferably, the aluminum salt in the aluminum-titanium solution of step (2) comprises aluminum sulfate and / or aluminum nitrate.

[0022] Preferably, the titanium salt in the aluminum-titanium solution of step (2) comprises titanium sulfate and / or titanyl sulfate.

[0023] Preferably, the concentration of H2O2 in the aluminum-titanium solution of step (2) is 12-15 wt%, for example, it can be 12 wt%, 13 wt%, 14 wt% or 15 wt%, but is not limited to the listed values, and the remaining values in the range are also applicable.

[0024] Preferably, the flow ratio of the metal salt solution to the aluminum-titanium solution is 8:(1-3.5), for example, it can be 8:1, 8:1.5, 8:2, 8:2.5, 8:3 or 8:3.5, but is not limited to the listed values, and the remaining values in the range are also applicable.

[0025] Preferably, the base solution of the present application is composed of deionized water, sodium hydroxide and a complexing agent, and by adjusting the content of sodium hydroxide and the complexing agent, the pH value and the concentration of the complexing agent in the base solution are adjusted.

[0026] Preferably, the temperature of the base solution of step (1) is 40-80℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃, 70℃ or 80℃, but is not limited to the listed values, and the remaining values in the range are also applicable.

[0027] Preferably, the pH value of the base solution of step (1) is 11-12, for example, it can be 11, 11.5 or 12, but is not limited to the listed values, and the remaining values in the range are also applicable.

[0028] Preferably, the concentration of the complexing agent in the bottom solution in step (1) is 0.2-0.5 mol / L, for example, it can be 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, but is not limited to the listed values, and the remaining values in the value range are also applicable.

[0029] In the co-precipitation reaction of the present application, the pH value of the co-precipitation reaction and the concentration of the complexing agent in the system are adjusted by adjusting the flow rate of the precipitant solution and the complexing agent solution.

[0030] Preferably, the temperature of the co-precipitation reaction in step (1) is 40-80℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃, 70℃ or 80℃, but is not limited to the listed values, and the remaining values in the value range are also applicable.

[0031] Preferably, the pH value of the co-precipitation reaction in step (1) is 10.5-11.5, for example, it can be 10.5, 11 or 11.5, but is not limited to the listed values, and the remaining values in the value range are also applicable.

[0032] Preferably, the concentration of the complexing agent in the system during the co-precipitation reaction in step (1) is 0.1-0.5 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, but is not limited to the listed values, and the remaining values in the value range are also applicable.

[0033] Preferably, the time of the co-precipitation reaction in step (1) is 60-100 h, for example, it can be 60 h, 70 h, 80 h, 90 h or 100 h, but is not limited to the listed values, and the remaining values in the value range are also applicable.

[0034] Preferably, the stirring speed in step (1) is 200-400 rpm, for example, it can be 200 rpm, 250 rpm, 300 rpm, 350 rpm or 400 rpm, but is not limited to the listed values, and the remaining values in the value range are also applicable.

[0035] In the present application, the pH value of the reaction in step (2) is adjusted by adjusting the flow rate of the complexing agent solution.

[0036] Preferably, the pH value of the reaction in step (2) is 9-10.5, for example, it can be 9, 9.5, 10 or 10.5, but is not limited to the listed values, and the remaining values in the value range are also applicable.

[0037] Preferably, the reaction time of step (2) is 3-6h, for example, it can be 3h, 4h, 5h or 6h, but is not limited to the listed values, and the remaining values in the value range are also applicable.

[0038] Preferably, the lithium source of step (3) includes lithium hydroxide and / or lithium carbonate.

[0039] In order to compensate for the loss on ignition of the lithium source in subsequent processing, the molar ratio of the spheroid-like hydroxide to Li in the lithium source is 1:(1.05-1.1), for example, it can be 1:1.05, 1:1.06, 1:1.08, 1:1.09 or 1:1.1, but is not limited to the listed values, and the remaining values in the value range are also applicable.

[0040] Preferably, the temperature of the pre-heating treatment of step (3) is 480-520℃, for example, it can be 480℃, 490℃, 500℃, 510℃ or 520℃, but is not limited to the listed values, and the remaining values in the value range are also applicable.

[0041] Preferably, the time of the pre-heating treatment of step (3) is 4.5-5.5h, for example, it can be 4.5h, 4.8h, 5h, 5.2h or 5.5h, but is not limited to the listed values, and the remaining values in the value range are also applicable.

[0042] Preferably, the temperature of the heat treatment of step (3) is 700-900℃, for example, it can be 700℃, 750℃, 800℃, 850℃ or 900℃, but is not limited to the listed values, and the remaining values in the value range are also applicable.

[0043] Preferably, the time of the heat treatment of step (3) is 10-16h, for example, it can be 10h, 12h, 14h, 15h or 16h, but is not limited to the listed values, and the remaining values in the value range are also applicable.

[0044] As a preferred technical solution of the preparation method of the first aspect of the present application, the preparation method comprises the following steps:

[0045] (1) Under the conditions of 40-80℃, pH value of 11-12 and complexing agent concentration of 0.2-0.5mol / L, the metal salt solution, the precipitant solution and the complexing agent solution are added in parallel flow, and the co-precipitation reaction is carried out under the conditions of 40-80℃ and pH value of 10.5-11.5 for 60-100h under the stirring condition of 200-400rpm;

[0046] The metal salt in the metal salt solution comprises nickel salt, cobalt salt and manganese salt, and the molar ratio of nickel, cobalt and manganese satisfies x:y:(1-x-y), wherein 0.2≤x≤0.9, 0<y≤0.33; and the total concentration of nickel, cobalt and manganese is 2-4 mol / L;

[0047] (2) After the co-precipitation reaction is completed, the temperature and stirring speed are kept unchanged, the aluminum-titanium solution, the precipitant solution and the complexing agent solution continue to be mixed in parallel flow, and the reaction is carried out at 40-80℃, pH 9-10.5 and a stirring speed of 200-400 rpm for 3-6 h; after the reaction is completed, the product is washed, dried and sieved to obtain the spherical-like hydroxide;

[0048] The solutes in the aluminum-titanium solution comprise aluminum salt, titanium salt and H2O2, the molar concentration of aluminum is 0.035-0.05 mol / L, the molar concentration of titanium is 0.15-0.18 mol / L, and the concentration of H2O2 is 12-15 wt%; the flow ratio of the metal salt solution to the aluminum-titanium solution is 8:(1-3.5);

[0049] (3) The lithium source is mixed with the spherical-like hydroxide, preheated at 480-520℃ for 4.5-5.5 h, and then heat-treated at 700-900℃ for 10-16 h to obtain the aluminum-doped lithium titanate coated ternary positive electrode material.

[0050] In a second aspect, the application provides an aluminum-doped lithium titanate coated ternary positive electrode material, which is prepared by the preparation method in the first aspect.

[0051] In a third aspect, the application provides a lithium ion battery comprising the aluminum-doped lithium titanate coated ternary positive electrode material prepared by the preparation method in the first aspect or the aluminum-doped lithium titanate coated ternary positive electrode material in the second aspect.

[0052] Compared with the prior art, the application has the following beneficial effects:

[0053] The preparation method provided by the application adds the aluminum-titanium solution in the co-precipitation reaction process to form an aluminum-doped lithium titanate precursor, so that the aluminum-doped lithium titanate coated ternary positive electrode material is obtained through heat treatment, and the interface stability is improved. DETAILED DESCRIPTION

[0054] The technical solutions of the application are further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the application and should not be regarded as specific limitations on the application.

[0055] Example 1

[0056] The embodiment provides a preparation method of an aluminum-doped lithium titanate coated ternary positive electrode material, and the preparation method comprises the following steps:

[0057] (1) in a bottom solution with a temperature of 60 DEG C, a pH value of 11.5 and an ammonia water concentration of 0.3 mol / L, metal salt solution, 2 mol / L sodium hydroxide solution and ammonia water are added in parallel flow, and the stirring speed is 300 rpm, so that the co-precipitation reaction is carried out under the conditions that the temperature in the reaction kettle is 60 DEG C, the pH value is 11 and the ammonia water concentration is 0.3 mol / L for 80 h;

[0058] The metal salt in the metal salt solution comprises nickel sulfate, cobalt sulfate and manganese sulfate, the molar ratio of nickel, cobalt and manganese satisfies 8:1:1, and the total concentration of nickel, cobalt and manganese is 2 mol / L;

[0059] (2) after the co-precipitation reaction is completed, the temperature and the stirring speed are kept unchanged, the aluminum-titanium solution, 2 mol / L sodium hydroxide solution and ammonia water are continuously mixed in parallel flow, and the reaction is carried out under the conditions that the temperature is 60 DEG C, the pH value is 10 and the stirring speed is 300 rpm for 4 h, and then the spherical hydroxide is obtained through washing, drying and sieving;

[0060] The solutes in the aluminum-titanium solution comprise aluminum sulfate, titanyl sulfate and H2O2, the molar concentration of aluminum is 0.04 mol / L, the molar concentration of titanium is 0.16 mol / L, and the concentration of H2O2 is 14 wt%; the flow ratio of the metal salt solution to the aluminum-titanium solution is 8:2;

[0061] (3) lithium hydroxide and the spherical hydroxide are mixed according to a molar ratio of 1.08:1, preheated at 500 DEG C for 5 h, and then heat-treated at 800 DEG C for 12 h, so that the aluminum-doped lithium titanate coated ternary positive electrode material is obtained.

[0062] Embodiment 2

[0063] The embodiment provides a preparation method of an aluminum-doped lithium titanate coated ternary positive electrode material, and the preparation method comprises the following steps:

[0064] (1) in a bottom solution with a temperature of 40 DEG C, a pH value of 11 and an ammonia water concentration of 0.2 mol / L, metal salt solution, 2 mol / L sodium hydroxide solution and ammonia water are added in parallel flow, and the stirring speed is 200 rpm, so that the co-precipitation reaction is carried out under the conditions that the temperature in the reaction kettle is 40 DEG C, the pH value is 10.5 and the ammonia water concentration is 0.2 mol / L for 60 h;

[0065] The metal salt in the metal salt solution comprises nickel sulfate, cobalt sulfate and manganese sulfate, the molar ratio of nickel, cobalt and manganese satisfies 8:1:1, and the total concentration of nickel, cobalt and manganese is 2 mol / L;

[0066] (2) after the co-precipitation reaction is completed, the temperature and stirring speed are kept unchanged, the aluminum-titanium solution, 2 mol / L sodium hydroxide solution and ammonia water are continuously mixed in parallel flow, and the reaction is carried out at 40℃, pH 9 and a stirring speed of 200 rpm for 3 h, and after the reaction is completed, the product is washed, dried and sieved to obtain the spherical-like hydroxide;

[0067] The solutes in the aluminum-titanium solution include aluminum sulfate, titanium sulfate and H2O2, the molar concentration of aluminum is 0.035 mol / L, the molar concentration of titanium is 0.15 mol / L, and the concentration of H2O2 is 12 wt%; the flow ratio of the metal salt solution to the aluminum-titanium solution is 8:1;

[0068] (3) the lithium hydroxide and the spherical-like hydroxide are mixed in a molar ratio of 1.08:1, preheated at 480℃ for 5.5 h, and then heat-treated at 700℃ for 16 h to obtain the aluminum-doped lithium titanate coated ternary positive electrode material.

[0069] Example 3

[0070] The present embodiment provides a preparation method of an aluminum-doped lithium titanate coated ternary positive electrode material, which comprises the following steps:

[0071] (1) the metal salt solution, 2 mol / L sodium hydroxide solution and ammonia water are added in parallel flow in a bottom solution at 80℃, pH 12 and ammonia water concentration 0.5 mol / L, and the co-precipitation reaction is carried out in the reaction kettle at 80℃, pH 11.5 and ammonia water concentration 0.5 mol / L under the condition of stirring at 400 rpm for 100 h;

[0072] The metal salt in the metal salt solution includes nickel chloride, cobalt chloride and manganese chloride, the molar ratio of nickel, cobalt and manganese satisfies 8:1:1, and the total concentration of nickel, cobalt and manganese is 4 mol / L;

[0073] (2) after the co-precipitation reaction is completed, the temperature and stirring speed are kept unchanged, the aluminum-titanium solution, 2 mol / L sodium hydroxide solution and ammonia water are continuously mixed in parallel flow, and the reaction is carried out at 80℃, pH 10.5 and a stirring speed of 400 rpm for 6 h, and after the reaction is completed, the product is washed, dried and sieved to obtain the spherical-like hydroxide;

[0074] The solutes in the aluminum-titanium solution include aluminum chloride, titanyl sulfate and H2O2, the molar concentration of aluminum is 0.05 mol / L, the molar concentration of titanium is 0.18 mol / L, and the concentration of H2O2 is 15 wt%; the flow ratio of the metal salt solution to the aluminum-titanium solution is 8:3.5;

[0075] (3) mixing lithium hydroxide with the spherical-like hydroxide in a molar ratio of 1.08:1, pre-treating at 520℃ for 4.5h, and then heat-treating at 900℃ for 10h to obtain the lithium aluminated titanate coated ternary positive electrode material.

[0076] Example 4

[0077] The present example provides a preparation method of the lithium aluminated titanate coated ternary positive electrode material, which comprises the following steps:

[0078] (1) under the conditions of 60℃, pH value of 11.5, and ammonia water concentration of 0.3mol / L, metal salt solution, 2mol / L sodium hydroxide solution and ammonia water are added in parallel flow, and the co-precipitation reaction is carried out under the conditions of 60℃, pH value of 11, and ammonia water concentration of 0.3mol / L in the reaction kettle with stirring at 300rpm for 80h;

[0079] The metal salt in the metal salt solution comprises nickel sulfate, cobalt sulfate and manganese sulfate, the molar ratio of nickel, cobalt and manganese satisfies 8:1:1, and the total concentration of nickel, cobalt and manganese is 2mol / L;

[0080] (2) after the co-precipitation reaction is completed, the temperature and stirring speed are kept unchanged, aluminum-titanium solution, 2mol / L sodium hydroxide solution and ammonia water are continuously added in parallel flow, and the reaction is carried out under the conditions of 60℃, pH value of 10, and stirring speed of 300rpm for 4h, and then the spherical-like hydroxide is obtained after washing, drying and sieving;

[0081] The solutes in the aluminum-titanium solution include aluminum sulfate, titanyl sulfate and H2O2, the molar concentration of aluminum is 0.04mol / L, the molar concentration of titanium is 0.16mol / L, and the concentration of H2O2 is 14wt%; the flow ratio of the metal salt solution and the aluminum-titanium solution is 8:2;

[0082] (3) mixing lithium hydroxide with the spherical-like hydroxide in a molar ratio of 1.08:1, heat-treating at 800℃ for 17h to obtain the lithium aluminated titanate coated ternary positive electrode material.

[0083] Example 5

[0084] The present example provides a preparation method of the lithium aluminated titanate coated ternary positive electrode material, which is the same as that of Example 1 except that the amount of the complexing agent solution is adjusted, and the pH value in step (2) is 8.5.

[0085] Example 6

[0086] The present example provides a preparation method of the lithium aluminated titanate coated ternary positive electrode material, which is the same as that of Example 1 except that the amount of the complexing agent solution is adjusted, and the pH value in step (2) is 11.

[0087] Example 7

[0088] The present example provides a preparation method of the lithium aluminum-doped titanate coated ternary positive electrode material, which is the same as that of Example 1 except that the molar concentration of aluminum in the aluminum-titanium solution is 0.02 mol / L.

[0089] Example 8

[0090] The present example provides a preparation method of the lithium aluminum-doped titanate coated ternary positive electrode material, which is the same as that of Example 1 except that the molar concentration of aluminum in the aluminum-titanium solution is 0.06 mol / L.

[0091] Example 9

[0092] The present example provides a preparation method of the lithium aluminum-doped titanate coated ternary positive electrode material, which is the same as that of Example 1 except that the molar concentration of titanium in the aluminum-titanium solution is 0.1 mol / L.

[0093] Example 10

[0094] The present example provides a preparation method of the lithium aluminum-doped titanate coated ternary positive electrode material, which is the same as that of Example 1 except that the molar concentration of titanium in the aluminum-titanium solution is 0.25 mol / L.

[0095] Comparative Example 1

[0096] The present comparative example provides a preparation method of a ternary positive electrode material, which comprises the following steps:

[0097] (1) Under the conditions of 60℃, pH value of 11.5, and ammonia concentration of 0.3 mol / L, the metal salt solution, 2 mol / L sodium hydroxide solution, and ammonia are added in parallel flow in the bottom liquid, and the co-precipitation reaction is carried out under the conditions of 60℃, pH value of 11, and ammonia concentration of 0.3 mol / L in the reaction kettle at a stirring speed of 300 rpm for 80 h;

[0098] The metal salt in the metal salt solution comprises nickel sulfate, cobalt sulfate, and manganese sulfate, the molar ratio of nickel, cobalt, and manganese satisfies 8:1:1, and the total concentration of nickel, cobalt, and manganese is 2 mol / L;

[0099] (2) After the co-precipitation reaction is completed, the temperature and stirring speed are kept unchanged, the aluminum solution, 2 mol / L sodium hydroxide solution, and ammonia are continuously added in parallel flow, and the reaction is carried out under the conditions of 60℃, pH value of 10, and stirring speed of 300 rpm for 4 h. After the reaction is completed, the hydroxide precursor is obtained by washing, drying, and sieving.

[0100] The solutes in the aluminum solution include aluminum sulfate and H2O2, the molar concentration of aluminum is 0.04 mol / L, and the concentration of H2O2 is 14 wt%; the flow rate ratio of the metal salt solution to the aluminum solution is 8:2;

[0101] (3) mixing lithium hydroxide and the hydroxide precursor according to a molar ratio of 1.08:1, preheating at 500 DEG C for 5h, and then heat treating at 800 DEG C for 12h to obtain the ternary positive electrode material.

[0102] Comparative Example 2

[0103] The present comparative example provides a preparation method of a ternary positive electrode material, which comprises the following steps:

[0104] (1) under the conditions of 60 DEG C, pH value of 11.5, and ammonia water concentration of 0.3 mol / L, the metal salt solution, 2 mol / L sodium hydroxide solution and ammonia water are added in parallel flow in the bottom liquid, and the co-precipitation reaction is carried out under the conditions of 60 DEG C, pH value of 11, and ammonia water concentration of 0.3 mol / L in the reaction kettle with stirring at 300 rpm for 80h;

[0105] The metal salt in the metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate, the molar ratio of nickel, cobalt and manganese satisfies 8:1:1, and the total concentration of nickel, cobalt and manganese is 2 mol / L;

[0106] (2) after the co-precipitation reaction is completed, the temperature and stirring speed are kept unchanged, the titanium solution, 2 mol / L sodium hydroxide solution and ammonia water are continuously added in parallel flow, and the reaction is carried out under the conditions of 60 DEG C, pH value of 10 and stirring speed of 300 rpm for 4h, and then the hydroxide precursor is obtained after washing, drying and sieving;

[0107] The solutes in the titanium solution include titanyl sulfate and H2O2, the molar concentration of titanium is 0.16 mol / L, and the concentration of H2O2 is 14 wt%; the flow rate ratio of the metal salt solution to the titanium solution is 8:2;

[0108] (3) mixing lithium hydroxide and the hydroxide precursor according to a molar ratio of 1.08:1, preheating at 500 DEG C for 5h, and then heat treating at 800 DEG C for 12h to obtain the ternary positive electrode material.

[0109] Comparative Example 3

[0110] The present comparative example provides a preparation method of an aluminum-doped lithium titanate coated ternary positive electrode material, which comprises the following steps:

[0111] (1) 60℃, pH value is 11.5 and ammonia concentration is 0.3 mol / L, and the metal salt solution, 2 mol / L sodium hydroxide solution and ammonia are added in parallel flow, and the stirring speed is 300 rpm, so that the temperature in the reaction kettle is 60℃, the pH value is 11, the ammonia concentration is 0.3 mol / L, and the co-precipitation reaction is carried out for 80h under the condition of 60℃, pH value is 11 and ammonia concentration is 0.3 mol / L;

[0112] The metal salt in the metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate, the molar ratio of nickel, cobalt and manganese satisfies 8:1:1, and the total concentration of nickel, cobalt and manganese is 2 mol / L;

[0113] (2) After the co-precipitation reaction is completed, the temperature and stirring speed are kept unchanged, and the aluminum-titanium solution, 2 mol / L sodium hydroxide solution and ammonia are continuously mixed in parallel flow, and the reaction is carried out at 60℃, pH value is 10 and stirring speed is 300 rpm for 4h, and after the reaction is completed, the hydroxide precursor is obtained after washing, drying and sieving;

[0114] The solute in the aluminum-titanium solution includes aluminum sulfate and titanyl sulfate, the molar concentration of aluminum is 0.04 mol / L, and the molar concentration of titanium is 0.16 mol / L; the flow ratio of the metal salt solution and the aluminum-titanium solution is 8:2;

[0115] (3) Lithium hydroxide and the spherical hydroxide are mixed according to a molar ratio of 1.08:1, preheated at 500℃ for 5h, and then heat-treated at 800℃ for 12h to obtain the aluminum-doped lithium titanate coated ternary positive electrode material.

[0116] Performance characterization

[0117] The positive electrode material, polyvinylidene fluoride and acetylene black are mixed according to a mass ratio of 80:10:10, NMP (N-methyl pyrrolidone) is added, stirred to form a slurry, coated on an aluminum foil, and dried to form a positive electrode. Lithium sheet is used as a negative electrode, and a CR2025 button cell is assembled, and its electrochemical performance is detected at 2.8-4.3V.

[0118] Table 1

[0119]

[0120]

[0121] As shown in Table 1, the aluminum-doped lithium titanate coated ternary positive electrode material provided by the application has a discharge specific capacity of 190.45 mAh / g or more, and the capacity retention rate after 50 cycles of 1C is 98.21% or more.

[0122] From the comparison of Example 4 and Example 1, it can be seen that when no pre-treatment is performed, the 0.1C discharge specific capacity and the capacity retention rate after 50 cycles at 1C are both significantly reduced, and therefore, as a preferred technical solution of the present application, it is preferred to be able to improve the 0.1C discharge specific capacity and the capacity retention rate after 50 cycles at 1C.

[0123] From the comparison of Example 5, Example 6 and Example 1, it can be seen that controlling the pH value of the aluminum-titanium solution during the reaction to be in the range of 9-10.5 can ensure the electrochemical performance of the obtained positive electrode material.

[0124] From the comparison of Example 7-10 and Example 1, it can be seen that controlling the appropriate molar concentration of aluminum and the molar concentration of titanium in the aluminum-titanium solution is conducive to ensuring the electrochemical performance of the obtained positive electrode material; as a preferred technical solution of the present application, it is required that the molar concentration of aluminum in the aluminum-titanium solution is 0.035-0.05 mol / L, and the molar concentration of titanium is 0.15-0.18 mol / L.

[0125] And from the comparison of Comparative Examples 1-3 and Example 1, it can be seen that the titanium salt, the aluminum salt and the hydrogen peroxide in the aluminum-titanium solution are indispensable, and in order to ensure the electrochemical performance of the obtained positive electrode material, it is required to ensure that the aluminum-titanium solution contains aluminum salt, titanium salt and H2O2 at the same time.

[0126] In summary, the preparation method provided by the present application adds an aluminum-titanium solution during the co-precipitation reaction process, forming an aluminum-doped lithium titanate precursor, so that an aluminum-doped lithium titanate coated ternary positive electrode material is obtained through heat treatment, and the interface stability is improved.

[0127] The above only describes specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application, which can be easily thought of by any person skilled in the art, falls within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a ternary cathode material coated with lithium aluminum titanate, characterized in that, The preparation method comprises the following steps: (1) A metal salt solution, a precipitating agent solution and a complexing agent solution are added in parallel into the bottom liquid, and a coprecipitation reaction is carried out under stirring conditions; (2) After the coprecipitation reaction ends, the temperature and the stirring speed are kept unchanged, and the aluminum-titanium solution and the complexing agent solution are continuously added in parallel and mixed. After the reaction ends, a spherical hydroxide is obtained; The solutes in the aluminum-titanium solution include an aluminum salt, a titanium salt and H₂O₂; In the aluminum-titanium solution, the molar concentration of aluminum is 0.035 - 0.05 mol / L, the molar concentration of titanium is 0.15 - 0.18 mol / L, and the concentration of H₂O₂ is 12 - 15 wt%; The pH value of the reaction is 9 - 10.5; (3) A lithium source is mixed with the spherical hydroxide, and preheating treatment and heat treatment are carried out in sequence to obtain the aluminum- and titanium-doped lithium titanate-coated ternary cathode material.

2. The preparation method according to claim 1, characterized in that, The aluminum salt in the aluminum-titanium solution in step (2) includes aluminum sulfate and / or aluminum nitrate.

3. The preparation method according to claim 1, characterized in that, The titanium salt in the aluminum-titanium solution in step (2) includes titanium sulfate and / or titanyl sulfate.

4. The preparation method according to claim 1, characterized in that, The flow rate ratio of the metal salt solution to the aluminum-titanium solution is 8:(1 - 3.5).

5. The preparation method according to claim 1, characterized in that, The temperature of the bottom liquid in step (1) is 40 - 80°C.

6. The preparation method according to claim 1, characterized in that, The pH value of the bottom liquid in step (1) is 11 - 12.

7. The preparation method according to claim 1, characterized in that, The concentration of the complexing agent in the bottom liquid in step (1) is 0.2 - 0.5 mol / L.

8. The preparation method according to claim 1, characterized in that, The temperature of the coprecipitation reaction in step (1) is 40 - 80°C.

9. The preparation method according to claim 1, characterized in that, The pH value of the coprecipitation reaction in step (1) is 10.5 - 11.

5.

10. The preparation method according to claim 1, characterized in that, During the coprecipitation reaction in step (1), the concentration of the complexing agent in the system is 0.1 - 0.5 mol / L.

11. The preparation method according to claim 1, characterized in that, The time of the coprecipitation reaction in step (1) is 60 - 100 h.

12. The preparation method according to claim 1, characterized in that, The stirring speed in step (1) is 200 - 400 rpm.

13. The preparation method according to claim 1, characterized in that, The reaction time in step (2) is 3 - 6 h.

14. The preparation method according to claim 1, characterized in that, The lithium source in step (3) includes lithium hydroxide and / or lithium carbonate.

15. The preparation method according to claim 1, characterized in that, The temperature of the preheating treatment in step (3) is 480 - 520°C.

16. The preparation method according to claim 1, characterized in that, The time of the preheating treatment in step (3) is 4.5 - 5.5 h.

17. The preparation method according to claim 1, characterized in that, The temperature of the heat treatment in step (3) is 700 - 900°C.

18. The preparation method according to claim 1, characterized in that, 19. The preparation method according to claim 1, characterized in that, The time of the heat treatment in step (3) is 10 - 16 h. The preparation method comprises the following steps: (1) In a bottom liquid at 40 - 80°C with a pH value of 11 - 12 and a complexing agent concentration of 0.2 - 0.5 mol / L, a metal salt solution, a precipitating agent solution and a complexing agent solution are added in parallel, and under the stirring condition of 200 - 400 rpm, a coprecipitation reaction is carried out for 60 - 100 h at 40 - 80°C and a pH value of 10.5 - 11.5; The metal salts in the metal salt solution include nickel salt, cobalt salt and manganese salt, and the molar ratio of nickel, cobalt and manganese satisfies x:y:(1 - x - y), where 0.2 ≤ x ≤ 0.9 and 0 < y ≤ 0.33; and the total concentration of nickel, cobalt and manganese is 2 - 4 mol / L; (2) After the co-precipitation reaction is completed, keep the temperature and stirring speed constant, continue to mix the aluminum-titanium solution and the complexing agent solution in parallel, and carry out the reaction for 3-6 hours at 40-80℃, pH value of 9-10.5 and stirring speed of 200-400rpm. After the reaction is completed, wash, dry and sieve to obtain spherical hydroxide. The solutes in the aluminum-titanium solution include aluminum salt, titanium salt, and H2O2. The molar concentration of aluminum is 0.035-0.05 mol / L, the molar concentration of titanium is 0.15-0.18 mol / L, and the concentration of H2O2 is 12-15 wt%. The flow rate ratio of the metal salt solution to the aluminum-titanium solution is 8:(1-3.5). (3) The lithium source is mixed with the spherical hydroxide, preheated at 480-520℃ for 4.5-5.5h, and then heat-treated at 700-900℃ for 10-16h to obtain the aluminum-doped lithium titanate coated ternary cathode material.

20. A lithium aluminum titanate-coated ternary cathode material, characterized in that, The lithium aluminum titanate-coated ternary cathode material is prepared by the preparation method described in any one of claims 1-19.

21. A lithium-ion battery, characterized in that, The lithium-ion battery includes the ternary cathode material coated with lithium aluminum titanate prepared by any one of the preparation methods of claims 1-19, or the ternary cathode material coated with lithium aluminum titanate as described in claim 20.

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