Modified lithium titanate negative electrode material and preparation method thereof, negative electrode plate, battery and electric device

Abstract

The invention discloses a modified lithium titanate negative electrode material and a preparation method thereof, a negative electrode plate, a battery and an electric device, and belongs to the field of energy and the field of new materials. The preparation method of the modified lithium titanate negative electrode material comprises the following steps: carrying out first reaction on lithium salt and first glacial acetic acid in a first solvent to prepare a lithium acetate solution; zirconium salt and second glacial acetic acid are subjected to first mixing in a second solvent, and a zirconium salt solution is formed; performing second mixing on the lithium acetate solution and the zirconium salt solution to form a lithium-zirconium mixed solution; performing third mixing on the lithium-zirconium mixed solution and a titanium source to form lithium-titanium-zirconium sol; and drying and calcining the lithium-titanium-zirconium sol to form the modified lithium titanate negative electrode material. According to the preparation method, the zirconium element is adopted for doping, meanwhile, a homogeneous phase mixing reaction process is matched, and a high-energy grinding process is not needed, so that uniform mixing of the raw materials on the molecular level can be realized, the high-rate charge-discharge capacity and the first efficiency are improved, and the probability of gas production of the battery is reduced.

Description

Technical Field

[0001] The present application relates to the fields of energy and new materials, and particularly to a modified lithium titanate negative electrode material, a preparation method thereof, a negative electrode sheet, a battery, and an electrical device. Background Art

[0002] With the rapid development of the energy storage and electric vehicle industries, lithium-ion batteries, as the mainstream energy storage devices, have gradually become an indispensable energy source in daily life. The negative electrode material of lithium-ion batteries is crucial for improving their performance. Although traditional graphite negative electrode materials have a relatively high theoretical specific capacity, they have poor high-rate charge-discharge capacity (i.e., high-power discharge performance) and low safety. Especially during high-rate charge-discharge processes, graphite negative electrodes are prone to structural expansion, resulting in a shortened battery cycle life and even a risk of thermal runaway.

[0003] Lithium titanate (Li4Ti5O 12 , LTO), as a candidate negative electrode material, has become a potential material to replace graphite due to its multiple advantages. LTO has very high thermal stability and chemical stability, is not prone to phase changes caused by lithium deintercalation, and is not easily expanded during charge-discharge processes, so it has high safety. In addition, lithium titanate has a long cycle life and a wide working voltage platform, and is suitable for applications with high safety requirements, such as electric vehicles and energy storage systems.

[0004] Although lithium titanate performs excellently in terms of safety, cycle life, etc., its low theoretical specific capacity (about 175 mAh / g) and low conductivity limit its application in fields with high energy density requirements. To improve the electrochemical performance of lithium titanate, researchers have done a lot of work in improving its conductivity, increasing specific capacity, and enhancing high-rate charge-discharge capacity, mainly reflected in the following aspects:

[0005] 1) Doping modification of lithium titanate materials: By doping different elements (such as aluminum, magnesium, cobalt, etc.), the conductivity and structural stability of lithium titanate can be improved. The doping elements can effectively reduce the particle size of lithium titanate particles, improve the transmission efficiency of electrons and ions, and thus increase the high-rate charge-discharge capacity and charge-discharge efficiency of lithium titanate.

[0006] 2) Structure optimization of lithium titanate: By adjusting the synthesis method of lithium titanate (such as high-temperature solid-phase method, hydrothermal method, sol-gel method, etc.), its crystal structure and particle size can be controlled, thereby improving its conductive performance and cycle stability. For example, nanosized lithium titanate can provide a larger specific surface area, increase the diffusion rate of lithium ions, and thus improve the high-rate charge-discharge capacity of the battery.

[0007] 3) Surface coating technology: Aiming at the low conductivity of lithium titanate, researchers have proposed to enhance its conductivity by coating a surface coating, such as coating conductive carbon, metal oxides or conductive polymers, which can effectively improve the electron and ion transport rates, thereby enhancing the high-rate discharge performance of lithium titanate.

[0008] 4) Composite materials of lithium titanate: Combining lithium titanate with other high-energy density materials (such as silicon, silicon carbide, etc.) to form a composite negative electrode material to improve the overall specific capacity and energy density. The composite material can also improve the conductivity and high-rate charge-discharge capacity of lithium titanate, while maintaining its excellent cycle stability and safety.

[0009] There is a method of physically coating lithium titanate with materials such as carbon / carbon nanotubes / silicon (expressed by chemical formula as Li4Ti5O 12 @C or Li4Ti5O 12 @Si). Since the crystal structure properties of the material itself are not changed, after the battery operates for a while, the coating layer breaks and can no longer play a modification role.

[0010] There is a method of carrying out high-energy ball milling of nanoscale titanium dioxide and solid lithium salts such as lithium carbonate for a long time, and then carrying out a long-time high-temperature reaction crystallization to obtain a nanoscale lithium titanate product with a small particle size and a high specific surface area. This method has high raw material costs, high production energy consumption, and the tapped density and compression density of the prepared lithium titanate with a large specific surface area are low. It is difficult to coat the electrode during the production of the battery cell, and the problem of battery gas generation has not been solved.

[0011] There is a method of using a small amount of Zr to dope the lithium titanate electrode material to solve the problem of microcrystal growth and agglomeration caused by high temperature and long-time calcination during the solid-phase synthesis of spinel-type lithium titanate, so as to obtain a Zr-doped lithium titanate electrode material with a high high-rate charge-discharge capacity and a long life. However, in this method, lithium acetate and zirconium salt are used, and water is used as a solvent. Lithium acetate needs to be redissolved in water, and its solubility is limited, and a homogeneous solution system cannot be formed. It needs to be combined with a high-energy grinding process, and the process cost is high. Moreover, zirconium salt is prone to hydrolysis in water, and the system stability and dispersion uniformity are not good, which will inevitably affect the electrochemical performance of the material.

[0012] Therefore, it is necessary to provide a preparation method of a modified lithium titanate negative electrode material that does not require high-energy ball milling and has a simple process. Summary of the Invention

[0013] Based on this, the main purpose of this application is to provide a preparation method of a zirconium-doped modified lithium titanate negative electrode material that does not require high-energy ball milling, has a simple process, and good mixing uniformity. The prepared modified lithium titanate negative electrode material has improved high-rate charge-discharge capacity and first efficiency during use, and can reduce the probability of battery gas generation.

[0014] In the first aspect of the present application, a preparation method of a modified lithium titanate anode material is provided, including the following steps:

[0015] Perform a first reaction with a lithium salt and first glacial acetic acid in a first solvent to prepare a lithium acetate solution;

[0016] Perform a first mixing of a zirconium salt and second glacial acetic acid in a second solvent to form a zirconium salt solution;

[0017] Perform a second mixing of the lithium acetate solution and the zirconium salt solution to form a lithium-zirconium mixed solution;

[0018] Perform a third mixing of the lithium-zirconium mixed solution and a titanium source to form a lithium-titanium-zirconium sol;

[0019] Dry and calcine the lithium-titanium-zirconium sol to form a modified lithium titanate anode material.

[0020] In some embodiments, the lithium salt includes at least one of lithium carbonate, lithium hydroxide, and lithium chloride.

[0021] In some embodiments, the zirconium salt includes at least one of zirconium acetate, zirconium nitrate, and zirconium sulfate;

[0022] and / or, the titanium source includes at least one of anatase titanium dioxide, rutile titanium dioxide, and titanium hydroxide;

[0023] and / or, the first solvent and the second solvent include water.

[0024] In some embodiments, the molar ratio of lithium element in the lithium salt to zirconium element in the zirconium salt is 1:0.003 - 0.03;

[0025] and / or, the molar ratio of zirconium element in the zirconium salt to second glacial acetic acid is 0.1 - 1:1;

[0026] and / or, the mass ratio of the first glacial acetic acid to the first solvent is 1 - 2:1;

[0027] and / or, the mass ratio of the second glacial acetic acid to the second solvent is 1:5 - 15;

[0028] and / or, the molar ratio of lithium element in the lithium salt to the first glacial acetic acid is 1:(0.95 - 1.2);

[0029] and / or, the molar ratio of lithium element in the lithium salt to titanium element in the titanium source is 1:1.2 - 1.3.

[0030] In some embodiments, the temperature of the first reaction is 50 - 70 °C;

[0031] and / or, the temperature of the first mixing is 50 - 70 °C;

[0032] And / or, the drying conditions include: spray drying at 200 - 300 °C;

[0033] And / or, the calcination conditions include: a calcination temperature of 550 - 900 °C; a calcination time of 5 - 15 h.

[0034] In the second aspect of the present application, there is provided a modified lithium titanate anode material prepared by the preparation method described in the first aspect.

[0035] In the third aspect of the present application, there is provided a negative electrode sheet including the modified lithium titanate anode material described in the second aspect.

[0036] In the fourth aspect of the present application, there is provided a battery including the modified lithium titanate anode material described in the second aspect or the negative electrode sheet described in the third aspect.

[0037] In the fifth aspect of the present application, there is provided an electrical device including the modified lithium titanate anode material described in the second aspect, the negative electrode sheet described in the third aspect, or the battery described in the fourth aspect.

[0038] Advantages of the present application:

[0039] 1. In the present application, a lithium salt reacts with glacial acetic acid to be converted into a solution of a soluble lithium salt (lithium acetate solution), and a zirconium salt is dissolved in water in the presence of glacial acetic acid to prepare a zirconium salt solution. Then, the lithium acetate solution and the zirconium salt solution are mixed to obtain a homogeneous lithium-zirconium mixed solution. Then, an insoluble but hydrophilic titanium source is added to prepare a lithium-titanium-zirconium sol. Without the need to cooperate with a high-energy grinding process, uniform mixing of raw materials at the molecular level can be achieved, enabling effective penetration of active components such as lithium and zirconium inside the secondary particles of titanium dioxide. And it can avoid the problems of poor system stability and dispersion uniformity caused by the re-dissolution of lithium acetate in water and the hydrolysis of zirconium salt in water, thereby promoting the doping and coating uniformity of zirconium on lithium titanate. The prepared modified lithium titanate anode material has improved high-rate charge-discharge capacity and first efficiency during use, and can reduce the probability of battery gas generation.

[0040] 2. In the present application, a dopant (zirconium salt) is mixed with a lithium salt and a titanium source in a solution system, and doping and coating can be completed by one calcination in an air atmosphere furnace. The preparation process is simple and the process cost is low. Compared with physical coating methods such as carbon / carbon nanotubes / graphene (after one calcination, a dopant is added and wet-ground to mix the raw materials, and then secondary calcination is carried out, and calcination needs to be carried out in an inert atmosphere), the process flow is greatly simplified, the equipment requirements for kilns and the like are reduced, and the production cost is significantly reduced. Detailed implementation manners

[0041] To make the objectives, technical solutions, and advantages of this application clearer and to have a more thorough and comprehensive understanding of the disclosed content of this application, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments of this application. The described embodiments are only a part of the embodiments of this application, rather than all of the embodiments.

[0042] The following provides a detailed description of the implementation of this application. This embodiment is implemented on the premise of the technical solution of this application, and provides a detailed implementation method and specific operation process. However, the protection scope of this application is not limited to the following embodiments.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0044] Term

[0045] Unless otherwise stated or there is a contradiction, the terms or phrases used herein have the following meanings:

[0046] In this application, when it comes to "multiple", "a variety of", etc., unless otherwise specified, it means greater than 2 or equal to 2 in quantity. For example, "one or more", "at least one" means one or greater than or equal to two.

[0047] In this application, terms such as "further", "especially", etc. are used to describe the purpose and indicate differences in content, but should not be construed as limiting the protection scope of this application.

[0048] In this application, among the technical features described in an open-ended manner, it includes a closed technical solution composed of the listed features, as well as an open technical solution containing the listed features.

[0049] In this application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values within this numerical interval is considered continuous, and it includes the two numerical endpoints of this numerical interval (i.e., the minimum value and the maximum value), as well as each numerical value between these two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within this numerical interval, it includes the two endpoint integers of this numerical range, as well as each integer between the two endpoints, which is equivalent to directly listing each integer. When providing multiple numerical ranges to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein. The "numerical value" in this numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. The "numerical interval" allows for a broad inclusion of numerical interval types such as percentage intervals, ratio intervals, and ratio value intervals.

[0050] In this application, unless otherwise specified, the temperature parameter allows for either isothermal treatment or variation within a certain temperature range. It should be understood that the isothermal treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within ranges such as ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0051] In this application, for units involving data ranges, if a unit is only attached after the right endpoint, it means that the units of the left endpoint and the right endpoint are the same. For example, 2 - 5h means that the units of both the left endpoint "2" and the right endpoint "5" are h (hours).

[0052] As used herein, the term "and / or" includes any and all combinations of one or more of the related listed items.

[0053] In this application, the temperature parameter, unless otherwise specified, allows for either isothermal treatment or treatment within a certain temperature range. The isothermal treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument.

[0054] In the first aspect of this application, there is provided a method for preparing a modified lithium titanate anode material, comprising the following steps:

[0055] Reacting a lithium salt with first glacial acetic acid in a first solvent to prepare a lithium acetate solution;

[0056] Mixing a zirconium salt with second glacial acetic acid in a second solvent to form a zirconium salt solution;

[0057] Mixing the lithium acetate solution with the zirconium salt solution for a second time to form a lithium-zirconium mixed solution;

[0058] Mixing the lithium-zirconium mixed solution with a titanium source for a third time to form a lithium-titanium-zirconium sol;

[0059] Drying and calcining the lithium-titanium-zirconium sol to form a modified lithium titanate anode material.

[0060] It is understandable that the present application uses zirconium element for doping. Zirconium and titanium belong to the same group of elements and have similar chemical properties, but the atomic radius of zirconium is slightly larger. When zirconium atoms replace the lattice positions of titanium atoms in lithium titanate, due to the radius difference, it is difficult for zirconium atoms to replace the titanium atoms inside the lithium titanate crystal, but only form doping on the surface of the lithium titanate crystal. On the one hand, the doping of zirconium atoms causes lattice distortion of lithium titanate, greatly improving the electronic conductivity of lithium titanate (lithium titanate itself has excellent lithium ion diffusion coefficient), providing a basis for the high-rate charge and discharge of lithium titanate; on the other hand, the "zirconium-oxygen bond" chemical coating layer formed on the surface of lithium titanate acts as an isolation protection layer, reducing the contact between the lithium titanate material and the electrolyte, and greatly reducing the probability of battery gas generation.

[0061] Furthermore, in the present application, the lithium salt reacts with glacial acetic acid to be converted into a solution of soluble lithium salt (lithium acetate solution), the zirconium salt is dissolved in water in the presence of glacial acetic acid to prepare a zirconium salt solution, and then the lithium acetate solution and the zirconium salt solution are mixed to obtain a homogeneous lithium-zirconium mixed solution. Then, an insoluble but hydrophilic titanium source is added to prepare a lithium-titanium-zirconium sol. Without the need to cooperate with a high-energy grinding process, uniform mixing of raw materials at the molecular level can be achieved, enabling effective penetration of active components such as lithium and zirconium inside the secondary particles of titanium dioxide. And it can avoid problems such as poor system stability and dispersion uniformity caused by the limited solubility of lithium acetate in water and the hydrolysis of zirconium salt in water, thereby promoting the doping and coating uniformity of zirconium on lithium titanate. The prepared modified lithium titanate negative electrode material has improved high-rate charge and discharge capacity and first efficiency during use, and can reduce the probability of battery gas generation.

[0062] Among them, glacial acetic acid is added when preparing the zirconium salt solution. The acidic environment provided by the ionization of glacial acetic acid in water can make the zirconium salt solution, the lithium-zirconium mixed solution and the lithium-titanium-zirconium sol in an acidic state. On the one hand, it can promote the dissolution of zirconium ions and avoid the hydrolysis reaction of zirconium salt in a neutral environment or with the pH fluctuation of the system to form zirconium hydroxide and hydrate, which will destroy the uniform dispersion of zirconium and cause poor system stability and dispersion uniformity, ensuring the uniform mixing effect of raw materials; on the other hand, glacial acetic acid can react with lithium salts such as lithium carbonate that have not reacted in the lithium acetate solution, improving the mixing uniformity of raw materials, thereby promoting the doping and coating uniformity of zirconium on lithium titanate, increasing the high-rate charge and discharge capacity of the lithium titanate negative electrode material, and reducing the probability of battery gas generation.

[0063] Compared with acetic acid, sulfuric acid and hydrochloric acid corrode the backend equipment more seriously. At the same time, the compounds formed by them are difficult to decompose, easily remain in the lithium titanate negative electrode material, affect its performance, and the decomposition products pollute the environment. While acetic acid is volatile and acetate is easy to decompose, and its decomposition products are only carbon dioxide and water, which is environmentally friendly and pollution-free, and can avoid corrosion of equipment. At the same time, after high-temperature calcination, there is no residue of glacial acetic acid, which will not have an adverse impact on the performance of the modified lithium titanate negative electrode material.

[0064] In a specific example, the lithium salt includes at least one of lithium carbonate, lithium hydroxide and lithium chloride.

[0065] In a specific example, the zirconium salt includes at least one of zirconium acetate, zirconium nitrate and zirconium sulfate.

[0066] In a specific example, the titanium source includes at least one of anatase titanium dioxide, rutile titanium dioxide and titanium hydroxide.

[0067] In a specific example, the first solvent and the second solvent include water, and water is preferably used.

[0068] In a specific example, the molar ratio of the lithium element in the lithium salt to the zirconium element in the zirconium salt is 1:0.003 - 0.03, preferably 1:0.005 - 0.025, more preferably 1:0.01 - 0.02. Specifically, it can be 1:0.003, 1:0.005, 1:0.01, 1:0.015, 1:0.02, 1:0.025, 1:0.03, etc.

[0069] In a specific example, the molar ratio of the zirconium element in the zirconium salt to the second glacial acetic acid is 0.1 - 1:1, preferably 0.1 - 0.85:1, more preferably 0.3 - 0.65:1. Specifically, it can be 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1, 0.55:1, 0.6:1, 0.65:1, 0.7:1, 0.8:1, 0.9:1, 1:1, etc.

[0070] In a specific example, the mass ratio of the first glacial acetic acid to the first solvent is 1 - 2:1, such as 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, etc.

[0071] In a specific example, the mass ratio of the second glacial acetic acid to the second solvent is 1:5 - 15, such as 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, etc.;

[0072] In a specific example, the molar ratio of the lithium element in the lithium salt to the first glacial acetic acid is 1:(0.95 - 1.2), such as 1:0.95, 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.2, etc.

[0073] In a specific example, the molar ratio of the lithium element in the lithium salt to the titanium element in the titanium source is 1:1.2 - 1.3, such as 1:1.2, 1:1.22, 1:1.24, 1:1.25, 1:1.26, 1:1.28, 1:1.3, etc.

[0074] In a specific example, the temperature of the first reaction is 50 - 70 °C, such as 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, etc.

[0075] In a specific example, the temperature of the first mixing is 50 - 70 °C, such as 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, etc.

[0076] In this application, the drying method is not specifically limited and can be drying by baking, spray drying or natural drying. Among them, spray drying is more preferred as it is conducive to obtaining a precursor powder with uniform mixing and good fluidity.

[0077] In a specific example, the drying conditions include: spray drying at 200 - 300 °C, and the specific temperature of spray drying can be 200 °C, 220 °C, 240 °C, 260 °C, 280 °C, 300 °C, etc.

[0078] In a specific example, the calcination conditions include: a calcination temperature of 550 - 900 °C, such as 550 °C, 600 °C, 650 °C, 700 °C, 750 °C, 800 °C, 850 °C, 900 °C, etc.; a calcination time of 5 - 15 h, such as 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, etc.

[0079] In the second aspect of this application, a modified lithium titanate negative electrode material prepared by the preparation method described in the first aspect is provided.

[0080] The modified lithium titanate negative electrode material prepared in this application has improved high-rate charge and discharge capacity and first efficiency during use, and can reduce the probability of battery gas generation.

[0081] In the third aspect of this application, a negative electrode plate is provided, which includes the modified lithium titanate negative electrode material described in the second aspect.

[0082] The negative electrode plate of this application uses a modified lithium titanate negative electrode material, which has improved high-rate charge and discharge capacity and first efficiency during use, and can reduce the probability of battery gas generation.

[0083] In the fourth aspect of this application, a battery is provided, which includes the modified lithium titanate negative electrode material described in the second aspect or the negative electrode plate described in the third aspect.

[0084] The battery of the present application uses a modified lithium titanate negative electrode material, which has improved high-rate charge and discharge capacity and first efficiency, and can reduce the probability of gas generation in the battery.

[0085] The fifth aspect of the present application provides an electrical device, including the modified lithium titanate negative electrode material described in the second aspect, the negative electrode sheet described in the third aspect, or the battery described in the fourth aspect.

[0086] Unless otherwise specified, the raw materials used in the following tests can be routinely purchased from the market.

[0087] Exemplary descriptions of the raw materials used in the examples and comparative examples are as follows:

[0088] Conductive agent: carbon black SUPER-P, purchased from Kelude Chemical Technology (Shanghai) Co., Ltd.;

[0089] Binder: model LA-132, purchased from Chengdu Yindi Le Technology Group Co., Ltd.

[0090] Other raw materials are commercially available.

[0091] The following are specific examples.

[0092] Example 1

[0093] Preparation of the modified lithium titanate negative electrode material:

[0094] 1) Preparation of lithium acetate solution: Add 400 kg of deionized water to a reaction kettle A, heat it to 60 °C, then add 321.3 kg of lithium carbonate (4.35 kmol), stir, and slowly add 522.2 kg of glacial acetic acid (8.7 kmol) to prepare a lithium acetate solution by stirring;

[0095] 2) Preparation of zirconium nitrate solution: Add 200 kg of deionized water to a reaction kettle B, heat it to 60 °C, then add 20 kg of glacial acetic acid (0.271 kmol), and add 17.1 kg of zirconium nitrate trihydrate (0.0435 kmol) to prepare a zirconium nitrate solution;

[0096] 3) Transfer the lithium acetate solution in reaction kettle A into reaction kettle B and mix it with the zirconium nitrate solution to obtain a lithium-zirconium mixed solution; add 864.7 kg of ordinary anatase titanium dioxide (10.83 kmol) to reaction kettle B, and prepare a lithium-titanium-zirconium sol by stirring.

[0097] 4) Spray-dry the lithium-titanium-zirconium sol at 200 °C by a spray dryer, and send the dried powder into a roller hearth kiln for high-temperature reaction at 800 °C in an air atmosphere for 15 h to obtain the modified lithium titanate negative electrode material.

[0098] Example 2

[0099] Except for the addition of 34.1 kg of zirconium nitrate trihydrate (0.087 kmol), the rest is the same as in Example 1.

[0100] Example 3

[0101] Except for the addition of 51.1 kg of zirconium nitrate trihydrate (0.13 kmol), the rest is the same as in Example 1.

[0102] Example 4

[0103] Except for the addition of 68.0 kg of zirconium nitrate trihydrate (0.173 kmol), the rest is the same as in Example 1.

[0104] Example 5

[0105] Except for the addition of 84.9 kg of zirconium nitrate trihydrate (0.216 kmol), the rest is the same as in Example 1

[0106] Example 6

[0107] Except for adding 40 kg of glacial acetic acid (0.542 kmol) when preparing the zirconium nitrate solution, the rest is the same as in Example 3.

[0108] Example 7

[0109] Except for adding 40 kg of glacial acetic acid (0.542 kmol) when preparing the zirconium nitrate solution, the rest is the same as in Example 4.

[0110] Comparative Example 1

[0111] Except for not adding zirconium nitrate trihydrate, the rest is the same as in Example 3.

[0112] Comparative Example 2

[0113] Except for not adding 20 kg of glacial acetic acid when preparing the zirconium nitrate solution, the rest is the same as in Example 3.

[0114] Comparative Example 3

[0115] Except for directly dissolving 8.7 kmol of lithium acetate anhydrous in 400 kg of water when preparing the lithium acetate solution, and not adding 20 kg of glacial acetic acid when preparing the zirconium nitrate solution with the prepared lithium acetate solution, the rest is the same as in Example 3. The specific processes of steps 1) and 2) are as follows:

[0116] 1) Preparation of lithium acetate solution: Add 200 kg of deionized water to the A reactor, heat to 60 °C, and then add 574.11 kg of lithium acetate anhydrous (8.7 kmol), and stir to prepare the lithium acetate solution;

[0117] 2) Preparation of zirconium nitrate solution: Add 200 kg of deionized water to the B reactor, heat to 60 °C, and add 51.1 kg of zirconium nitrate trihydrate (0.13 kmol) to prepare the zirconium nitrate solution.

[0118] Test Example

[0119] Preparation of coin half-cell: Weigh 0.85 g of the modified lithium titanate anode materials of the examples and comparative examples, 0.10 g of SUPER-P, and then add 1 mL of the prepared aqueous binder with a concentration of 5% (w / v) to obtain a negative electrode slurry of 85% wt active material + 10% wt conductive agent + 5% binder (calculated based on the mass percentage of raw materials other than the solvent being 100%). After coating and drying, an electrode sheet is made, which is used as the positive electrode, and a lithium metal sheet is used as the negative electrode to form a coin half-cell.

[0120] 1. Perform performance tests on the modified lithium titanate anode materials and the corresponding coin half-cells prepared in the examples and comparative examples. Among them, the pH of the modified lithium titanate anode material is measured using a Leici PHS-3E model pH meter, and the D50 particle size is measured using a Malvern MS-3000 laser particle size analyzer; the electrochemical performance of the coin half-cell is tested using a Blue Electric test cabinet, and the results are shown in Table 1.

[0121] Table 1 Summary of Performance of Examples and Comparative Examples

[0122]

[0123] As can be seen from Table 1, the coin half-cells prepared in Examples 1-5 of this application all have good rate performance and initial efficiency. Their discharge specific capacity at 10C can reach more than 120 mAh / g, and they can maintain more than 83% of the discharge specific capacity at 0.5C.

[0124] By comparing Examples 1-5, it can be seen that when doping lithium titanate with zirconium, the amount is not the more the better. As the amount of zirconium increases, the rate performance of the coin half-cell first increases and then decreases. When the molar ratio of zirconium element to lithium element is 0.01 - 0.02:1, the performance is better. Its discharge specific capacity at 10C can reach more than 140 mAh / g, and it can maintain more than 87% of the discharge specific capacity at 0.5C.

[0125] By comparing Example 3 and Comparative Example 1, it can be seen that doping lithium titanate with zirconium significantly improves its rate performance and initial efficiency.

[0126] By comparing Example 3 and Comparative Example 2, it can be seen that the addition of glacial acetic acid significantly improves the rate performance and initial efficiency. It can be seen that in the reaction system of this application, it is extremely crucial to configure the zirconium salt solution under acidic conditions.

[0127] Comparing Comparative Examples 2-3, it can be seen that preparing a lithium acetate solution using glacial acetic acid and lithium carbonate has an obvious impact on the rate performance and initial efficiency compared with directly dissolving lithium acetate in water to prepare an aqueous lithium acetate solution. This may be because the solubility of lithium acetate is limited. In Comparative Example 3, directly dissolving lithium acetate in water cannot completely dissolve it, and commercially available lithium acetate has hard agglomerates after processes such as drying. The undissolved lithium acetate cannot be evenly dispersed. In Comparative Example 2, lithium nitrate and acetic acid are used to prepare lithium acetate, and the generated lithium acetate can form a homogeneous system in a supersaturated state. Therefore, good dispersion can be achieved. Thus, Comparative Example 2 has improved performance compared with Comparative Example 3.

[0128] Using commercially available lithium acetate requires more water for dissolution to form a homogeneous system, but too much water will result in too low a solid content in the system, a decrease in the stability of the lithium titanium zirconium sol, and easy stratification, which will in turn affect the performance of the modified lithium titanate anode material.

[0129] 2. Gas generation performance

[0130] The specific test conditions are as follows: The modified lithium titanate anode materials of Examples 2-3 and Comparative Examples 1-3 are respectively prepared into full-cell battery cores, and charged and discharged at a current of 1C for 200 cycles at 60°C, and the bulging situation on their surfaces is observed, and the degree of gas generation is judged according to the bulging situation. Among them, the more serious the bulging, the greater the degree of gas generation. The results are shown in Table 2.

[0131] Table 2 Degree of gas generation

[0132]

[0133] As can be seen from Table 2, after the lithium titanate anode materials prepared in Examples 2-3 are made into full-cell battery cores, the gas generation amount of the battery cores is extremely small, while there are different degrees of gas generation in Comparative Examples 1-3.

[0134] In summary, in this application, zirconium element doping is adopted, and at the same time, it is combined with a homogeneous mixing reaction process. Without a high-energy grinding process, uniform mixing of raw materials at the molecular level can be achieved, thereby improving the high-rate charge and discharge capacity and the initial efficiency, and reducing the probability of battery gas generation.

[0135] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0136] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A method for preparing a modified lithium titanate negative electrode material, characterized in that: The steps include: A lithium acetate solution is prepared by performing a first reaction in a first solvent with a lithium salt and a first glacial acetic acid; first mixing a zirconium salt and a second glacial acetic acid in a second solvent to form a zirconium salt solution; The lithium acetate solution and the zirconium salt solution are mixed for a second time to form a lithium zirconium mixed solution; The lithium zirconium mixed solution is thirdly mixed with a titanium source to form a lithium titanium zirconium sol; The lithium titanium zirconium sol is dried and calcined to form a modified lithium titanate negative electrode material.

2. The preparation method according to claim 1, characterized in that The lithium salt includes at least one of lithium carbonate, lithium hydroxide and lithium chloride.

3. The preparation method according to claim 1 or 2, characterized in that: The zirconium salt includes at least one of zirconium acetate, zirconium nitrate and zirconium sulfate; And / or, the titanium source includes at least one of anatase titanium dioxide, rutile titanium dioxide and titanium hydroxide.

4. The preparation method according to claim 1 or 2, characterized in that: The first solvent and the second solvent include water.

5. The preparation method according to claim 1 or 2, characterized in that: The molar ratio of the lithium element in the lithium salt to the zirconium element in the zirconium salt is 1:0.003-0.03; and / or, the molar ratio of the zirconium element in the zirconium salt to the second glacial acetic acid is 0.1-1:1; And / or, the mass ratio of the first glacial acetic acid to the first solvent is 1-2:1; And / or, the mass ratio of the second glacial acetic acid to the second solvent is 1:5-15.

6. The preparation method according to claim 1 or 2, characterized in that: The temperature of the first reaction is 50-70°C; And / or, the temperature of the first mixing is 50-70°C; And / or, the drying conditions include: spray drying at 200-300°C; And / or, the calcination conditions include: calcination temperature 550-900° C.; calcination time 5-15 h.

7. The modified lithium titanate negative electrode material prepared by the preparation method according to any one of claims 1 to 6.

8. A negative electrode plate, characterized in that: Including the modified lithium titanate negative electrode material as described in claim 7.

9. A battery, characterized in that: It includes the modified lithium titanate negative electrode material according to claim 7 or the negative electrode plate according to claim 8.

10. An electrical device, characterized in that: It comprises the modified lithium titanate negative electrode material according to claim 7, the negative electrode sheet according to claim 8, or the battery according to claim 9.

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