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

Abstract

The invention relates to an aluminum-doped lithium titanate coated ternary positive electrode material and a preparation method and application thereof, and the preparation method comprises the following steps: adding a metal salt solution, a precipitator solution and a complexing agent solution into a base solution in a parallel flow manner, and carrying out a co-precipitation reaction under a stirring condition; after the coprecipitation reaction is finished, the temperature and the stirring speed are kept unchanged, the aluminum-titanium solution, the precipitant solution and the ammonia water solution are continuously mixed in a parallel flow mode, and a sphere-like hydroxide is obtained after the reaction is finished; solute in the aluminum-titanium solution comprises aluminum salt, titanium salt and hydrogen peroxide; and mixing a lithium source with the sphere-like hydroxide, and sequentially carrying out preheating treatment and heat treatment to obtain the aluminum-doped lithium titanate coated ternary positive electrode material. According to the preparation method, an aluminum-titanium solution is added in a coprecipitation 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.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to a ternary positive electrode material coated with aluminum-doped lithium titanate, and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have the advantages of high operating voltage, long cycle life, and light weight, and are currently widely used in consumer electronics and new energy vehicles. Among them, the positive electrode material is one of the core components of lithium-ion batteries, which limits the energy density, power density, and cycle life of lithium-ion batteries.

[0003] The three elements Ni, Co and Mn in the ternary positive electrode material lithium nickel cobalt manganese oxide work together to combine the advantages of three lithium-ion battery positive electrode materials: LiCoO2, LiNiO2 and LiMnO2. It also has good thermal stability, high energy density and specific capacity, and low raw material cost. However, it has the defects of mixed cations and poor structural stability.

[0004] In order to improve the cycle stability and safety of ternary cathode materials, it is necessary to set a coating layer on the surface of the ternary cathode material to improve corrosion resistance and reduce the side reaction between the material and the electrolyte. However, since the ternary cathode material will produce a certain volume change during the cycle of lithium removal and lithium insertion, after a long cycle, it is easy to cause separation between the coating material and the ternary cathode material, reducing the coating effect.

[0005] Therefore, it is necessary to provide an aluminum-doped lithium titanate-coated ternary positive electrode material capable of improving structural stability, and a preparation method and application thereof. Summary of the invention

[0006] The purpose of the present invention is to provide an aluminum-doped lithium titanate coated ternary positive electrode material and a preparation method and application thereof. The preparation method forms an aluminum-doped lithium titanate precursor by adding an aluminum-titanium solution during a co-precipitation reaction, thereby obtaining an aluminum-doped lithium titanate coated ternary positive electrode material by heat treatment, thereby improving interface stability.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a ternary positive electrode material coated with aluminum-doped lithium titanate, the preparation method comprising the following steps:

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

[0010] (2) After the coprecipitation reaction is completed, keep the temperature and stirring speed unchanged, continue to mix the aluminum-titanium solution and the complexing agent solution in a co-current manner, and obtain spherical hydroxide after the reaction is completed;

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

[0012] (3) Mix the lithium source with the spherical hydroxide, and perform preheating treatment and heat treatment in sequence to obtain the aluminum-doped lithium titanate-coated ternary cathode material.

[0013] The preparation method provided by the present invention forms a lithium titanate precursor doped with aluminum by adding an aluminum-titanium solution during the coprecipitation reaction, and thus obtains an aluminum-doped lithium titanate-coated ternary cathode material through heat treatment, which improves the interfacial stability. After aluminum doping, the conductivity of lithium titanate becomes better, which is more conducive to improving the electrical properties of the material. The introduction of Al-O bond is also beneficial to improving the surface structure stability, and the addition of H2O2 is beneficial to improving the coating uniformity.

[0014] Preferably, 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.

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

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

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

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

[0019] Preferably, the molar concentration of aluminum in the aluminum-titanium solution in 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 ​​within the numerical range not listed are also applicable.

[0020] Preferably, the molar concentration of titanium in the aluminum-titanium solution in 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 other values ​​not listed within the numerical range are also applicable.

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

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

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

[0025] Preferably, the base liquid of the present invention is composed of deionized water, sodium hydroxide and a complexing agent, and the pH value and the concentration of the complexing agent in the base liquid can be adjusted by adjusting the contents of sodium hydroxide and the complexing agent.

[0026] Preferably, the temperature of the base liquid in step (1) is 40-80°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 70°C or 80°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

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

[0028] Preferably, the concentration of the complexing agent in the base solution of step (1) is 0.2-0.5 mol / L, for example, 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 other values ​​not listed within the numerical range are also applicable.

[0029] During the coprecipitation reaction of the present invention, the pH value of the coprecipitation reaction and the concentration of the complexing agent in the system are regulated by adjusting the flow rates of the precipitant solution and the complexing agent solution.

[0030] Preferably, the temperature of the coprecipitation reaction in step (1) is 40-80°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 70°C or 80°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] Preferably, the pH value of the coprecipitation 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 other values ​​not listed within the numerical range are also applicable.

[0032] Preferably, during the coprecipitation reaction in step (1), the concentration of the complexing agent in the system 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 ​​not listed within the numerical range are also applicable.

[0033] Preferably, the coprecipitation reaction time in step (1) is 60-100 h, for example, 60 h, 70 h, 80 h, 90 h or 100 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

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

[0035] In the present invention, the pH value during 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, 9, 9.5, 10 or 10.5, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the reaction time of step (2) is 3-6 h, for example, 3 h, 4 h, 5 h or 6 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

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

[0039] In order to compensate for the ignition loss of the lithium source during subsequent treatment, the molar ratio of the spherical hydroxide to the 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 unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, the temperature of the preheat treatment in step (3) is 480-520°C, for example, 480°C, 490°C, 500°C, 510°C or 520°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] Preferably, the preheating time in step (3) is 4.5-5.5 h, for example, 4.5 h, 4.8 h, 5 h, 5.2 h or 5.5 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] Preferably, the temperature of the heat treatment in step (3) is 700-900°C, for example, 700°C, 750°C, 800°C, 850°C or 900°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] Preferably, the heat treatment time in step (3) is 10-16 h, for example, 10 h, 12 h, 14 h, 15 h or 16 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

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

[0045] (1) adding a metal salt solution, a precipitant solution and a chelating agent solution to a base solution at 40-80° C., a pH value of 11-12 and a chelating agent concentration of 0.2-0.5 mol / L in parallel, stirring at 200-400 rpm, and carrying out a coprecipitation reaction at 40-80° C., a pH value of 10.5-11.5 for 60-100 hours;

[0046] The metal salts in the metal salt solution include nickel salts, cobalt salts and manganese salts, 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;

[0047] (2) After the coprecipitation reaction is completed, keeping the temperature and stirring speed unchanged, continue to mix the aluminum-titanium solution, precipitant solution and complexing agent solution in a co-current manner, and carry out the reaction at 40 - 80 °C, pH value of 9 - 10.5 and stirring speed of 200 - 400 rpm for 3 - 6 h. After the reaction is completed, wash, dry and screen to obtain spherical hydroxide;

[0048] The solutes in the aluminum-titanium solution include aluminum salts, titanium salts 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);

[0049] (3) Mix the lithium source with the spherical hydroxide, preheat at 480 - 520 °C for 4.5 - 5.5 h, and then heat-treat at 700 - 900 °C for 10 - 16 h to obtain the aluminum-doped lithium titanate-coated ternary cathode material.

[0050] In the second aspect, the present invention provides an aluminum-doped lithium titanate-coated ternary cathode material, characterized in that the aluminum-doped lithium titanate-coated ternary cathode material is prepared by the preparation method described in the first aspect.

[0051] In the third aspect, the present invention provides a lithium-ion battery, which includes the aluminum-doped lithium titanate-coated ternary cathode material prepared by the preparation method described in the first aspect, or the aluminum-doped lithium titanate-coated ternary cathode material described in the second aspect.

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

[0053] The preparation method provided by the present invention forms a lithium titanate precursor doped with aluminum by adding an aluminum-titanium solution during the coprecipitation reaction, and thus obtains an aluminum-doped lithium titanate-coated ternary cathode material through heat treatment, improving the interfacial stability. Specific Embodiments

[0054] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0055] Example 1

[0056] This embodiment provides a method for preparing a ternary positive electrode material coated with aluminum-doped lithium titanate, the preparation method comprising the following steps:

[0057] (1) Adding metal salt solution, 2 mol / L sodium hydroxide solution and ammonia water into a bottom liquid at 60°C, pH 11.5 and 0.3 mol / L ammonia concentration in parallel, stirring at 300 rpm, and carrying out coprecipitation reaction for 80 hours under the conditions of 60°C, pH 11 and 0.3 mol / L ammonia concentration in the reactor;

[0058] 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;

[0059] (2) After the coprecipitation reaction is completed, the temperature and stirring speed are kept unchanged, and the aluminum titanium solution, 2 mol / L sodium hydroxide solution and ammonia water are continuously mixed in parallel, and the reaction is carried out for 4 hours at 60° C., pH value of 10 and stirring speed of 300 rpm. After the reaction is completed, the product is washed, dried and sieved to obtain a spherical hydroxide;

[0060] The solutes in the aluminum-titanium solution include 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 quasi-spherical hydroxide are mixed in a molar ratio of 1.08:1, preheated at 500° C. for 5 h, and then heat treated at 800° C. for 12 h to obtain the aluminum-doped lithium titanate-coated ternary positive electrode material.

[0062] Example 2

[0063] This embodiment provides a method for preparing a ternary positive electrode material coated with aluminum-doped lithium titanate, the preparation method comprising the following steps:

[0064] (1) Adding metal salt solution, 2 mol / L sodium hydroxide solution and ammonia water into a bottom liquid at 40°C, pH 11 and 0.2 mol / L ammonia water concentration in parallel, stirring at 200 rpm, and carrying out a coprecipitation reaction for 60 hours under the conditions of 40°C, pH 10.5 and 0.2 mol / L ammonia water concentration in the reactor;

[0065] The metal salt in the metal salt solution includes nickel nitrate, cobalt nitrate and manganese nitrate, 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;

[0066] (2) After the coprecipitation reaction is completed, the temperature and stirring speed are kept unchanged, and the aluminum titanium solution, 2 mol / L sodium hydroxide solution and ammonia water are continuously mixed in parallel, and the reaction is carried out for 3 hours at 40° C., pH 9 and stirring speed 200 rpm. After the reaction is completed, the product is washed, dried and sieved to obtain a spherical 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) Lithium hydroxide and the quasi-spherical hydroxide are mixed in a molar ratio of 1.08:1, preheated at 480° C. for 5.5 h, and then heat treated at 700° C. for 16 h to obtain the aluminum-doped lithium titanate-coated ternary positive electrode material.

[0069] Example 3

[0070] This embodiment provides a method for preparing a ternary positive electrode material coated with aluminum-doped lithium titanate, the preparation method comprising the following steps:

[0071] (1) Adding metal salt solution, 2 mol / L sodium hydroxide solution and ammonia water into a bottom liquid at 80°C, pH 12 and 0.5 mol / L ammonia water concentration in parallel, stirring at 400 rpm, and carrying out a coprecipitation reaction for 100 h under the conditions of 80°C, pH 11.5 and 0.5 mol / L ammonia water concentration in the reactor;

[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 coprecipitation reaction is completed, the temperature and stirring speed are kept unchanged, and the aluminum titanium solution, 2 mol / L sodium hydroxide solution and ammonia water are continuously mixed in parallel, and the reaction is carried out for 6 hours at 80° C., pH value of 10.5 and stirring speed of 400 rpm. After the reaction is completed, the product is washed, dried and sieved to obtain a spherical hydroxide;

[0074] The solute in the aluminum-titanium solution includes 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) Lithium hydroxide and the quasi-spherical hydroxide are mixed in a molar ratio of 1.08:1, preheated at 520° C. for 4.5 h, and then heat treated at 900° C. for 10 h to obtain the aluminum-doped lithium titanate-coated ternary positive electrode material.

[0076] Example 4

[0077] This embodiment provides a method for preparing a ternary positive electrode material coated with aluminum-doped lithium titanate, the preparation method comprising the following steps:

[0078] (1) Adding metal salt solution, 2 mol / L sodium hydroxide solution and ammonia water into a bottom liquid at 60°C, pH 11.5 and 0.3 mol / L ammonia concentration in parallel, stirring at 300 rpm, and carrying out coprecipitation reaction for 80 hours under the conditions of 60°C, pH 11 and 0.3 mol / L ammonia concentration in the reactor;

[0079] 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;

[0080] (2) After the coprecipitation reaction is completed, the temperature and stirring speed are kept unchanged, and the aluminum titanium solution, 2 mol / L sodium hydroxide solution and ammonia water are continuously mixed in parallel, and the reaction is carried out for 4 hours at 60° C., pH value of 10 and stirring speed of 300 rpm. After the reaction is completed, the product is washed, dried and sieved to obtain a spherical hydroxide;

[0081] The solutes in the aluminum-titanium solution include 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;

[0082] (3) Lithium hydroxide and the quasi-spherical hydroxide are mixed in a molar ratio of 1.08:1, and heat treated at 800° C. for 17 h to obtain the aluminum-doped lithium titanate-coated ternary positive electrode material.

[0083] Example 5

[0084] This embodiment provides a method for preparing an aluminum-doped lithium titanate coated ternary positive electrode material, which is the same as that of embodiment 1 except that the amount of the complexing agent solution is adjusted so that the pH value in step (2) is 8.5.

[0085] Example 6

[0086] This embodiment provides a method for preparing a ternary positive electrode material coated with aluminum-doped lithium titanate, which is the same as that of embodiment 1 except that the amount of the complexing agent solution is adjusted so that the pH value in step (2) is 11.

[0087] Example 7

[0088] This embodiment provides a method for preparing an aluminum-doped lithium titanate-coated ternary positive electrode material, which is the same as that of Embodiment 1 except that the molar concentration of aluminum in the aluminum-titanium solution is 0.02 mol / L.

[0089] Example 8

[0090] This embodiment provides a method for preparing an aluminum-doped lithium titanate-coated ternary positive electrode material, which is the same as that of Embodiment 1 except that the molar concentration of aluminum in the aluminum-titanium solution is 0.06 mol / L.

[0091] Example 9

[0092] This embodiment provides a method for preparing an aluminum-doped lithium titanate-coated ternary positive electrode material, which is the same as that of Embodiment 1 except that the molar concentration of titanium in the aluminum-titanium solution is 0.1 mol / L.

[0093] Example 10

[0094] This embodiment provides a method for preparing a ternary positive electrode material coated with aluminum-doped lithium titanate, 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] This comparative example provides a method for preparing a ternary positive electrode material, the preparation method comprising the following steps:

[0097] (1) Adding metal salt solution, 2 mol / L sodium hydroxide solution and ammonia water into a bottom liquid at 60°C, pH 11.5 and 0.3 mol / L ammonia concentration in parallel, stirring at 300 rpm, and carrying out coprecipitation reaction for 80 hours under the conditions of 60°C, pH 11 and 0.3 mol / L ammonia concentration in the reactor;

[0098] 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;

[0099] (2) After the coprecipitation reaction is completed, the temperature and stirring speed are kept unchanged, and the aluminum solution, 2 mol / L sodium hydroxide solution and ammonia water are mixed in parallel, and the reaction is carried out for 4 hours at 60° C., pH value of 10 and stirring speed of 300 rpm. After the reaction is completed, the product is washed, dried and sieved to obtain a hydroxide precursor;

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

[0101] (3) Lithium hydroxide and the hydroxide precursor are mixed in a molar ratio of 1.08:1, preheated at 500° C. for 5 h, and then heat treated at 800° C. for 12 h to obtain a ternary positive electrode material.

[0102] Comparative Example 2

[0103] This comparative example provides a method for preparing a ternary positive electrode material, the preparation method comprising the following steps:

[0104] (1) Adding metal salt solution, 2 mol / L sodium hydroxide solution and ammonia water into a bottom liquid at 60°C, pH 11.5 and 0.3 mol / L ammonia concentration in parallel, stirring at 300 rpm, and carrying out coprecipitation reaction for 80 hours under the conditions of 60°C, pH 11 and 0.3 mol / L ammonia concentration in the reactor;

[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 coprecipitation reaction is completed, the temperature and stirring speed are kept unchanged, and the titanium solution, 2 mol / L sodium hydroxide solution and ammonia water are continuously mixed in parallel, and the reaction is carried out for 4 hours at 60° C., pH value of 10 and stirring speed of 300 rpm. After the reaction is completed, the product is washed, dried and sieved to obtain a hydroxide precursor;

[0107] The solute in the titanium solution includes titanyl sulfate and H2O2, 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 titanium solution is 8:2;

[0108] (3) Lithium hydroxide and the hydroxide precursor are mixed in a molar ratio of 1.08:1, preheated at 500° C. for 5 h, and then heat treated at 800° C. for 12 h to obtain a ternary positive electrode material.

[0109] Comparative Example 3

[0110] This comparative example provides a method for preparing a ternary positive electrode material coated with aluminum-doped lithium titanate, the preparation method comprising the following steps:

[0111] (1) Adding metal salt solution, 2 mol / L sodium hydroxide solution and ammonia water into a bottom liquid at 60°C, pH 11.5 and 0.3 mol / L ammonia concentration in parallel, stirring at 300 rpm, and carrying out coprecipitation reaction for 80 hours under the conditions of 60°C, pH 11 and 0.3 mol / L ammonia concentration in the reactor;

[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 coprecipitation reaction is completed, the temperature and stirring speed are kept unchanged, and the aluminum titanium solution, 2 mol / L sodium hydroxide solution and ammonia water are continuously mixed in parallel, and the reaction is carried out for 4 hours at 60° C., pH value of 10 and stirring speed of 300 rpm. After the reaction is completed, the product is washed, dried and sieved to obtain a hydroxide precursor;

[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 to the aluminum-titanium solution is 8:2;

[0115] (3) Lithium hydroxide and the quasi-spherical hydroxide are mixed in a molar ratio of 1.08:1, preheated at 500° C. for 5 h, and then heat treated at 800° C. for 12 h 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 were mixed in a mass ratio of 80:10:10, NMP (N-methylpyrrolidone) was added, stirred to form a slurry, coated on aluminum foil, and dried to make a positive electrode. The lithium sheet was used as the negative electrode to assemble a CR2025 button battery, and its electrochemical performance was tested at 2.8-4.3V.

[0118] Table 1

[0119]

[0120]

[0121] As can be seen from Table 1, the aluminum-doped lithium titanate-coated ternary positive electrode material provided in the present application has a discharge specific capacity of more than 190.45 mAh / g, and a capacity retention rate of more than 98.21% after 50 cycles at 1C.

[0122] From the comparison between Example 4 and Example 1, it can be seen that when no preheating treatment is performed, the 0.1C discharge specific capacity and the capacity retention rate of 1C cycle 50 cycles are significantly reduced. Therefore, as the preferred technical scheme of the present invention, optimization can improve the 0.1C discharge specific capacity and the capacity retention rate of 1C cycle 50 cycles.

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

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

[0125] From the comparison between Comparative Examples 1-3 and Example 1, it can be seen that the titanium salt, aluminum salt and hydrogen peroxide in the aluminum-titanium solution are indispensable. In order to ensure the electrochemical properties of the obtained positive electrode material, it is necessary 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 invention forms an aluminum-doped lithium titanate precursor by adding an aluminum-titanium solution during the coprecipitation reaction, and then obtains an aluminum-doped lithium titanate-coated ternary positive electrode material through heat treatment, thereby improving the interface stability.

[0127] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing an aluminum-doped lithium titanate coated ternary positive electrode material, characterized in that: The preparation method comprises the following steps: (1) adding a metal salt solution, a precipitant solution and a complexing agent solution into the base liquid in parallel, and performing a coprecipitation reaction under stirring conditions; (2) After the coprecipitation reaction is completed, the temperature and stirring speed are kept constant, and the aluminum-titanium solution and the complexing agent solution are continuously mixed in parallel, and a spherical hydroxide is obtained after the reaction is completed; The solute in the aluminum-titanium solution includes aluminum salt, titanium salt and H2O2; (3) A lithium source is mixed with the quasi-spherical hydroxide, and preheating and heat treatment are performed in sequence to obtain the aluminum-doped lithium titanate coated ternary positive electrode material.

2. The preparation method according to claim 1, characterized in that: The molar concentration of aluminum in the aluminum-titanium solution of step (2) is 0.035-0.05 mol / L; Preferably, the molar concentration of titanium in the aluminum-titanium solution in step (2) is 0.15-0.18 mol / L.

3. The preparation method according to claim 1 or 2, characterized in that: The aluminum salt in the aluminum-titanium solution of step (2) includes aluminum sulfate and / or aluminum nitrate; Preferably, the titanium salt in the aluminum-titanium solution in step (2) comprises titanium sulfate and / or titanyl sulfate; Preferably, the concentration of H2O2 in the aluminum-titanium solution in step (2) is 12-15wt%; Preferably, the flow ratio of the metal salt solution to the aluminum-titanium solution is 8:(1-3.5).

4. The preparation method according to any one of claims 1 to 3, characterized in that The temperature of the base liquid in step (1) is 40-80°C; Preferably, the pH value of the base solution in step (1) is 11-12; Preferably, the concentration of the complexing agent in the base solution in step (1) is 0.2-0.5 mol / L.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The temperature of the coprecipitation reaction in step (1) is 40-80° C. Preferably, the pH value of the coprecipitation reaction in step (1) is 10.5-11.5; Preferably, during the coprecipitation reaction in step (1), the concentration of the complexing agent in the system is 0.1-0.5 mol / L; Preferably, the coprecipitation reaction time in step (1) is 60-100 hours; Preferably, the stirring speed in step (1) is 200-400 rpm.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The pH value of the reaction in step (2) is 9-10.5; Preferably, the reaction time in step (2) is 3-6 hours.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The lithium source in step (3) includes lithium hydroxide and / or lithium carbonate; Preferably, the temperature of the preheating treatment in step (3) is 480-520°C; Preferably, the preheating time in step (3) is 4.5-5.5h; Preferably, the temperature of the heat treatment in step (3) is 700-900°C; Preferably, the heat treatment time in step (3) is 10-16 hours.

8. The preparation method according to claim 1, characterized in that: The preparation method comprises the following steps: (1) adding a metal salt solution, a precipitant solution and a chelating agent solution to a base solution at 40-80° C., a pH value of 11-12 and a chelating agent concentration of 0.2-0.5 mol / L in parallel, stirring at 200-400 rpm, and carrying out a coprecipitation reaction at 40-80° C., a pH value of 10.5-11.5 for 60-100 hours; The metal salts in the metal salt solution include nickel salts, cobalt salts and manganese salts, 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 coprecipitation reaction is completed, keep the temperature and stirring speed unchanged, continue to mix the aluminum-titanium solution and the complexing agent solution in a co-current manner, and react for 3 - 6 h under the conditions of 40 - 80 °C, a pH value of 9 - 10.5 and a stirring speed of 200 - 400 rpm. After the reaction is completed, wash, dry and screen to obtain spherical hydroxide; The solutes in the aluminum-titanium solution include aluminum salts, titanium salts 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) Mix the lithium source with the spherical hydroxide, perform preheating treatment at 480 - 520 °C for 4.5 - 5.5 h, and then perform heat treatment at 700 - 900 °C for 10 - 16 h to obtain the aluminum-doped lithium titanate-coated ternary cathode material.

9. A ternary positive electrode material coated with aluminum-doped lithium titanate, characterized in that: The aluminum-doped lithium titanate-coated ternary cathode material is prepared by the preparation method according to any one of claims 1 - 8.

10. A lithium ion battery, characterized in that: The lithium ion battery includes the aluminum-doped lithium titanate-coated ternary cathode material prepared by the preparation method according to any one of claims 1 - 8, or the aluminum-doped lithium titanate-coated ternary cathode material according to claim 9.

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