Preparation methods of lithium titanate materials, lithium titanate materials and their applications

Abstract

This application discloses a method for preparing lithium titanate material, the lithium titanate material itself, and its applications. The preparation method includes the following steps: using a lithium titanate electrode sheet as the raw material, placing the lithium titanate electrode sheet in an alkaline solution to dissolve the electrode current collector in the alkaline solution, thereby obtaining a first mixture containing lithium titanate; performing solid-liquid separation on the first mixture to obtain a solid second mixture containing lithium titanate; and calcining the second mixture and a lithium source in an oxygen-containing atmosphere to obtain the lithium titanate material. This method effectively recovers and utilizes the lithium titanate from the lithium titanate electrode sheet. The entire preparation method has the advantages of simple process, low equipment requirements, easy control of process conditions, low cost, and safety and environmental protection. The obtained lithium titanate material can be used to prepare lithium titanate batteries.

Description

Technical Field

[0001] This application relates to the field of water electrolysis technology, specifically to a method for preparing lithium titanate material, the lithium titanate material, and its applications. Background Technology

[0002] Lithium titanate is a "zero-strain" material with excellent electrochemical performance, cycle life, and safety, making it suitable for use as an anode material in lithium-ion batteries. The main methods for preparing lithium titanate are the traditional solid-state reaction method and the sol-gel method. The traditional solid-state reaction method involves mixing and grinding a lithium source (e.g., lithium carbonate, lithium hydroxide) and a titanium source (e.g., titanium dioxide) in a specific ratio to obtain a homogeneous mixture, followed by high-temperature calcination to obtain the lithium titanate material. This method suffers from high energy consumption and difficulty in controlling product quality. The sol-gel method involves mixing a titanium source, a lithium source, and an organic complexing agent to obtain a sol-gel precursor, followed by aging and sintering to obtain the lithium titanate material. Due to the involvement of an organic complexing agent in the synthesis process, the preparation cost is relatively high.

[0003] Both the traditional solid-state reaction method and the sol-gel method for preparing lithium titanate materials suffer from high production costs, resulting in expensive lithium titanate. Furthermore, the manufacturing and use of lithium titanate batteries generate a large quantity of waste lithium titanate electrodes. Currently, there are no effective methods for recycling these waste electrodes, preventing the efficient recovery and reuse of lithium titanate and leading to its waste.

[0004] Therefore, it is of great significance to find a way to prepare lithium titanate from waste lithium titanate electrodes in order to achieve the recycling of lithium titanate. Summary of the Invention

[0005] This application provides a method for preparing lithium titanate material, lithium titanate material and its application, which uses waste lithium titanate electrode sheets as raw materials to prepare lithium titanate, thereby realizing the recycling of lithium titanate.

[0006] The technical solution of this application is as follows:

[0007] In a first aspect, this application provides a method for preparing lithium titanate material, comprising the following steps:

[0008] A lithium titanate electrode sheet is provided, the lithium titanate electrode sheet comprising an electrode current collector and a first coating coated on the electrode current collector, the first coating being made of lithium titanate. The lithium titanate electrode sheet is placed in an alkaline solution, and the electrode current collector is dissolved in the alkaline solution to obtain a first mixture containing the lithium titanate.

[0009] The first mixture is subjected to solid-liquid separation to obtain a solid second mixture, the second mixture comprising the lithium titanate; and

[0010] The second mixture and a lithium source are calcined in an oxygen-containing atmosphere to obtain lithium titanate material.

[0011] Optionally, the pH of the alkaline solution is not less than 10; and / or

[0012] The solute in the alkaline solution is selected from one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide; and / or

[0013] The solvent for the alkaline solution is water.

[0014] Optionally, in the step of solid-liquid separation of the first mixture, the solid-liquid separation includes one or more of the following: vacuum filtration, centrifugation, reverse osmosis, membrane filtration, nanofiltration, ultrafiltration, microfiltration, and gravity sedimentation.

[0015] Optionally, after the step of solid-liquid separation of the first mixture and before the step of obtaining the solid second mixture, the preparation method further includes the steps of: collecting the first solid obtained by the solid-liquid separation, washing the first solid with water once or multiple times, and then drying it to obtain the second solid; the second mixture is the second solid;

[0016] Alternatively, after the step of solid-liquid separation of the first mixture and before the step of obtaining the solid second mixture, the preparation method further includes the steps of: collecting the first solid obtained by the solid-liquid separation, crushing the first solid to obtain a third solid of 50 mesh to 300 mesh; the second mixture is the third solid;

[0017] Alternatively, after the step of solid-liquid separation of the first mixture and before the step of obtaining the solid second mixture, the preparation method further includes the steps of: collecting the first solid obtained by the solid-liquid separation, washing the first solid with water once or multiple times, and then drying it to obtain the second solid; crushing the second solid to obtain a fourth solid of 50 mesh to 300 mesh; and the second mixture being the fourth solid.

[0018] Optionally, the lithium source is selected from one or more lithium hydroxides and lithium salts; and / or

[0019] In the step of calcining the second mixture and the lithium source, the molar ratio of titanium in the second mixture to lithium in the lithium source is 1:(0.83-0.89).

[0020] Optionally, the calcination treatment is carried out under a pressure of 0.2 MPa to 0.6 MPa; and / or

[0021] The calcination treatment temperature is 550℃~760℃; and / or

[0022] The mass of the second mixture is 100g to 300g, and the calcination time is 1h to 4h.

[0023] Secondly, this application also provides a lithium titanate material, prepared by any of the preparation methods described in the first aspect.

[0024] Optionally, the lithium titanate material has a spherical structure; and / or

[0025] The lithium titanate material has an initial charge capacity of 150.0 mAh / g to 170.0 mAh / g under 1C coin charge conditions, and / or the lithium titanate material has an initial discharge capacity of 150.0 mAh / g to 170.0 mAh / g under 1C coin charge conditions, and / or the lithium titanate material has an initial charge-discharge efficiency greater than 99% under 1C coin charge conditions.

[0026] Thirdly, this application also provides the application of the preparation method according to any one of the first aspects, or the lithium titanate material according to any one of the second aspects, in the preparation of lithium titanate batteries.

[0027] Fourthly, this application also provides a lithium titanate battery, the lithium titanate battery including a lithium titanate negative electrode sheet, the lithium titanate negative electrode sheet including a negative electrode current collector and a second coating coated on the negative electrode current collector, the material of the second coating including lithium titanate material prepared by any of the preparation methods in the first aspect, or lithium titanate material as described in any of the second aspects.

[0028] This application provides a method for preparing lithium titanate material, the lithium titanate material itself, and its applications, which have the following technical advantages:

[0029] In the preparation method of the lithium titanate material, lithium titanate electrode sheets are used as raw materials to prepare lithium titanate material. The lithium titanate electrode sheets can be, for example, waste electrode sheets. First, the lithium titanate electrode sheets are placed in an alkaline solution, so that the electrode current collector is dissolved in the alkaline solution, thereby separating the lithium titanate from the electrode current collector. Then, high-capacity lithium titanate material is prepared through solid-liquid separation, lithium replenishment and calcination treatment and other processes. The lithium titanate in the lithium titanate electrode sheets is effectively recycled and utilized. Moreover, the structure of lithium titanate in the lithium titanate electrode sheets is not destroyed during the recycling process. The entire preparation method has the advantages of simple process, low equipment requirements, easy control of process conditions, low cost and safety and environmental protection.

[0030] The lithium titanate material exhibits an initial charge capacity of 168.7 mAh / g and an initial discharge capacity of 168 mAh / g under 1C conditions, with an initial charge-discharge efficiency of 99.87%, thus enabling its use in the fabrication of lithium titanate batteries. Attached Figure Description

[0031] The technical solution and other beneficial effects of this application will become apparent from the following detailed description of specific embodiments in conjunction with the accompanying drawings.

[0032] Figure 1 A schematic flowchart illustrating a method for preparing lithium titanate material according to an embodiment of this application;

[0033] Figure 2 The X-ray diffraction pattern of the lithium titanate material prepared in Example 1 is shown below.

[0034] Figure 3 This is a scanning electron microscope image of the lithium titanate material prepared in Example 1. Detailed Implementation

[0035] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art, and the materials or reagents used in the embodiments and comparative examples of this application are commercially available. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0037] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of embodiments. Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0038] In the description of this application, the term "comprising" means "including but not limited to".

[0039] The terms “multiple,” “multiple times,” or similar expressions refer to two or more times, such as two, three, four, five, six, etc.

[0040] The term "and / or" encompasses any one of two or more of the listed items, as well as any and all combinations of the listed items. These combinations include any two listed items, any number of listed items, or a combination of all listed items. For example, "A and / or B" includes three parallel solutions: A, B, and A+B. Similarly, the technical solution "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (i.e., all connected by "logical OR"), any and all combinations of A, B, C, and D, including combinations of any two or three of A, B, C, and D, and combinations of all four of A, B, C, and D (i.e., all connected by "logical AND").

[0041] This application provides a method for preparing lithium titanate material, such as... Figure 1 As shown, it includes the following steps:

[0042] S1. Provide a lithium titanate electrode sheet, the lithium titanate electrode sheet includes an electrode current collector and a first coating coated on the electrode current collector, the material of the first coating includes lithium titanate, and place the lithium titanate electrode sheet in an alkaline solution to dissolve the electrode current collector in the alkaline solution to obtain a first mixture containing the lithium titanate.

[0043] S2. Perform solid-liquid separation on the first mixture to obtain a solid second mixture, the second mixture containing the lithium titanate;

[0044] S3. Under an oxygen-containing atmosphere, the second mixture and the lithium source are calcined to obtain lithium titanate material.

[0045] In the above-mentioned method for preparing lithium titanate materials, lithium titanate electrodes are used as raw materials. For example, the lithium titanate electrodes can be waste electrodes. First, the lithium titanate electrodes are placed in an alkaline solution, so that the electrode current collector dissolves in the alkaline solution, thereby separating the lithium titanate from the electrode current collector. Then, high-capacity lithium titanate materials are prepared through solid-liquid separation, lithium replenishment and calcination, etc., which effectively recovers and utilizes the lithium titanate in the lithium titanate electrodes. Moreover, the structure of lithium titanate in the lithium titanate electrodes is not destroyed during the recovery and utilization process. The entire preparation method has the advantages of simple process, low equipment requirements, easy control of process conditions, low cost, and safety and environmental protection.

[0046] Specifically, in step S1, the lithium titanate electrode sheet can be obtained from discarded batteries or cells through processes such as self-discharge and disassembly. The electrode current collector material is, for example, aluminum foil. In the step of placing the lithium titanate electrode sheet in an alkaline solution, the electrode current collector in the lithium titanate electrode sheet dissolves due to a chemical reaction with the alkaline solution. The metal elements (e.g., aluminum) in the electrode current collector enter the solution in ionic form, while the lithium titanate in the lithium titanate electrode sheet does not react chemically with the alkaline solution, thus keeping the lithium titanate in the lithium titanate electrode sheet in a solid state.

[0047] To facilitate rapid dissolution of the electrode current collector in the alkaline solution, in some embodiments of this application, the pH of the alkaline solution is not less than 10. The pH of the alkaline solution can be, for example, 10, 11, 12, 13, 14, or any value between two of the aforementioned values. The solute in the alkaline solution is, for example, selected from one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide. The solvent in the alkaline solution is, for example, water, and the concentration of the solute in the alkaline solution is, for example, 0.1 mol / L to 6 mol / L.

[0048] It should be noted that the alkaline solution cannot be replaced with an acidic solution. The reason is that while the electrode current collector can react chemically with acid to dissolve, the acid will also react chemically with the lithium titanate in the lithium titanate electrode, thus destroying the original structure of the lithium titanate. Only lithium salts (such as lithium carbonate) and titanium salts (such as titanium dioxide, metatitanic acid, etc.) can be recovered, and then lithium titanate is chemically synthesized using the recovered lithium and titanium salts, making the process cumbersome and complex, and increasing costs. Furthermore, the solvent in the alkaline solution can be water or a polar organic solvent, such as alcohols with 1 to 10 carbon atoms, but water is preferred for the following reasons: First, organic solvents are difficult to remove, resulting in poor purity of the prepared lithium titanate material or increasing the difficulty of purification processes; second, organic solvents are expensive, increasing preparation costs; third, organic solvents have an odor, and some are flammable and explosive, which is detrimental to safety and the environment.

[0049] In some embodiments of this application, the step of placing the lithium titanate electrode sheet in an alkaline solution to dissolve the electrode current collector is carried out in a reactor equipped with a stirring paddle, and the material is stirred throughout the dissolution process of the electrode current collector. To further promote the rapid dissolution of the electrode current collector in the alkaline solution, the lithium titanate electrode sheet can be cut into blocks and then placed in a reactor containing an alkaline solution.

[0050] In step S2, the purpose of solid-liquid separation of the first mixture is to extract solid lithium titanate. Solid-liquid separation includes, but is not limited to, one or more of the following: vacuum filtration, centrifugation, reverse osmosis, membrane filtration, nanofiltration, ultrafiltration, microfiltration, and gravity sedimentation. For example, the solid-liquid separation is vacuum filtration.

[0051] To improve the purity of the recovered lithium titanate, in some embodiments of this application, for step S2, after the solid-liquid separation of the first mixture and before obtaining the solid second mixture, the method for preparing the lithium titanate material further includes the steps of: collecting the first solid obtained by the solid-liquid separation, washing the first solid with water once or multiple times, and then drying it to obtain the second solid; the second solid is the second mixture. The purpose of the water washing is to remove soluble impurity ions, which include, but are not limited to, Na+. + Mg 2+ SO4 2- and PO4 3- It should be noted that the drying process includes, but is not limited to, heating, vacuum drying, etc. For example, the drying process can be: placing the material obtained after water washing in a forced-air drying oven for heating and drying.

[0052] As an alternative implementation, in order to improve the purity of the recovered lithium titanate material, in some other embodiments of this application, for step S3, after the step of solid-liquid separation of the first mixture and before obtaining the solid second mixture, the method for preparing the lithium titanate material further includes the steps of: collecting the first solid obtained by the solid-liquid separation, crushing the first solid to obtain a third solid of 50 mesh to 300 mesh; the third solid is the second mixture.

[0053] As an alternative implementation, in order to improve the purity of the recovered lithium titanate material, in some other embodiments of this application, for step S3, after the step of solid-liquid separation of the first mixture and before obtaining the solid second mixture, the method for preparing the lithium titanate material further includes the steps of: collecting the first solid obtained by solid-liquid separation, washing the first solid with water once or multiple times, and then drying it to obtain the second solid; crushing the second solid to obtain a fourth solid of 50 mesh to 300 mesh; the fourth solid is the second mixture.

[0054] The coating material based on lithium titanate electrode sheets typically also includes conductive carbon black and a binder (such as polyvinylidene fluoride). For example, the coating material consists of 90% lithium titanate, 5% conductive carbon black, and 5% polyvinylidene fluoride by mass percentage. The conductive carbon black reacts chemically with oxygen at high temperatures, and the binder is easily removed at high temperatures. Therefore, the solid obtained in step S2 needs to be calcined to effectively remove the conductive carbon black and binder, thereby improving the purity of the recovered lithium titanate.

[0055] In step S3, the purpose of calcining the second mixture and the lithium source is twofold: firstly, to supplement lithium elements to improve the capacity of the resulting lithium titanate material; and secondly, to simultaneously supplement lithium elements and remove impurities (conductive carbon black and binder), requiring only one calcination treatment, thus effectively simplifying the preparation process. The calcination treatment is carried out in an oxygen-containing atmosphere, which can be either an oxygen atmosphere or an air atmosphere.

[0056] The lithium source is selected from one or more of lithium hydroxide and lithium salts, wherein the lithium salts include, but are not limited to, one or more of lithium carbonate, lithium nitrate, lithium sulfate, lithium phosphate, lithium acetate and lithium halide.

[0057] In order to further improve the purity and electrochemical performance of the prepared lithium titanate material, in some embodiments of this application, the molar ratio of titanium in the solid to lithium in the lithium source in the second mixture is 1:(0.83 to 0.89), for example, it can be 1:0.83, 1:0.84, 1:0.85, 1:0.86, 1:0.87, 1:0.88, 1:0.89 or any value between the two aforementioned values.

[0058] In order to further improve the removal rate of impurities (conductive carbon black and binder) and maintain the spherical structure of lithium titanate, in some embodiments of this application, the calcination treatment is carried out at a pressure of 0.2 MPa to 0.6 MPa, for example, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa and any two of the aforementioned values ​​for the time.

[0059] In order to further improve the removal rate of impurities (conductive carbon black and binder) and reduce the caking rate of the resulting lithium titanate material, in some embodiments of this application, the calcination temperature is 550°C to 760°C, for example, 550°C, 600°C, 650°C, 700°C, 760°C and any two of the aforementioned values.

[0060] In order to further improve the removal rate of impurities (conductive carbon black and binder) and reduce the caking rate of the obtained lithium titanate material, in some embodiments of this application, the mass of the second mixture is 100g to 300g, for example, it can be 100g, 200g, 300g and any two of the aforementioned values; the calcination time is 1h to 4h, for example, it can be 1h, 2h, 3h, 4h and any two of the aforementioned values.

[0061] In order to improve the size uniformity of the obtained lithium titanate material, in some embodiments of this application, after the calcination treatment step S3 and before the step of obtaining lithium titanate material, the method for preparing lithium titanate material further includes the step of: screening the material obtained after calcination treatment with a sieve, wherein the mesh size of the sieve is, for example, 200 mesh, and the material passing through the sieve is the obtained lithium titanate material.

[0062] This application also provides a lithium titanate material, which is prepared by any of the preparation methods described above.

[0063] Specifically, the lithium titanate material has a spherical structure. In some embodiments of this application, the lithium titanate material has a charging capacity of 150.0 mAh / g to 170.0 mAh / g under 1C coin charge conditions, and / or a discharging capacity of 150.0 mAh / g to 170.0 mAh / g under 1C coin charge conditions, and / or a charge / discharge efficiency of greater than 99% under 1C coin charge conditions.

[0064] This application also provides a method for preparing any of the lithium titanate materials described above, or the application of any of the lithium titanate materials described above in lithium titanate batteries. Specifically, the lithium titanate material prepared by any of the methods described above, or any of the lithium titanate materials described above, is used to prepare the negative electrode sheet of a lithium titanate battery.

[0065] This application embodiment also provides a lithium titanate battery, the lithium titanate battery including a lithium titanate negative electrode sheet, the lithium titanate negative electrode sheet including a negative electrode current collector and a second coating coated on the negative electrode current collector, the material of the second coating including lithium titanate material prepared by any of the preparation methods described above or any of the lithium titanate materials described above, and the material of the negative electrode current collector is, for example, aluminum foil.

[0066] The technical solutions and effects of this application will be described in detail below through specific embodiments. The following embodiments are only some embodiments of this application and are not intended to limit this application.

[0067] Example 1

[0068] This embodiment provides a method for preparing lithium titanate material, the lithium titanate material itself, and its applications. The method for preparing the lithium titanate material uses waste lithium titanate negative electrode sheets as raw materials. The waste lithium titanate negative electrode sheets include a negative electrode current collector and a first coating coated on the negative electrode current collector. The negative electrode current collector is made of aluminum foil. The first coating, calculated by mass percentage, consists of 90% lithium titanate, 5% conductive carbon black, and 5% polyvinylidene fluoride.

[0069] The preparation method of the lithium titanate material includes the following steps:

[0070] S1.1 Take 1 kg of lithium titanate negative electrode sheet, cut the lithium titanate negative electrode sheet into multiple cubes with a length of 10 cm × 10 cm, place the multiple cubes into a glass reactor containing 10 L of sodium hydroxide aqueous solution (the concentration of sodium hydroxide is 0.1 mol / L), turn on the stirring, the stirring speed is 500 r / min, stir the reaction until the negative electrode current collector is completely dissolved, and obtain the first mixture containing lithium titanate;

[0071] S1.2. The first mixture obtained in step S1.1 is filtered to obtain a first filter cake; then, the first filter cake is dispersed in deionized water for a first water washing treatment, and then filtered to remove water to obtain a second filter cake; next, the second filter cake is dispersed in deionized water for a second water washing treatment, and then filtered to remove water to obtain a third filter cake; subsequently, the third filter cake is dispersed in deionized water for a third water washing treatment, and then the material obtained after the third water washing treatment is placed in a forced-air drying oven and dried at a temperature of 120°C to obtain a solid.

[0072] S1.3. The solid obtained in step S1.2 is crushed using a high-speed crusher, and the crushed material is then passed through a 200-mesh sieve. The material passing through the sieve is collected. The material passing through the sieve is the second mixture.

[0073] S1.4. The second mixture is mixed with lithium carbonate to obtain a mixture, wherein the molar ratio of titanium to lithium in the mixture is 1:0.87. 200g of the mixture is weighed into a crucible, and the crucible containing the mixture is placed in a high-temperature atmosphere furnace. The mixture is calcined under compressed air (pressure 0.4MPa) at a temperature of 700℃ for 2 hours. The calcined material is then passed through a 200-mesh sieve. X-ray diffraction analysis is performed on the material passing through the sieve. Figure 2 As shown, the material passing through the sieve has good lithium titanate diffraction peaks and no obvious impurity peaks, indicating that the material passing through the sieve is the lithium titanate material obtained in the preparation.

[0074] The morphology of the prepared lithium titanate material was observed using a scanning electron microscope (SEM), such as... Figure 3 As shown, the prepared lithium titanate material maintains a spherical structure, which indicates that lithium titanate in the lithium titanate electrode was effectively recycled, and the structure of lithium titanate in the lithium titanate electrode was not destroyed during the recycling process.

[0075] CR2016 coin cells were prepared using the prepared lithium titanate material. After standing for 8 hours and the open circuit voltage stabilized, a charge-discharge test was conducted with the current density relative to the negative electrode set to 1C. The charging cutoff voltage was 2.7V, and after standing for 1 minute, the discharging cutoff voltage was 1.5V. The initial charge capacity and initial discharge capacity were recorded, and the initial charge-discharge efficiency was calculated. The initial discharge efficiency is the ratio of the initial discharge capacity to the initial charge capacity.

[0076] A total of five parallel samples were tested, and the test results are shown in Table 1 below:

[0077] Table 1. Performance overview of the lithium titanate material prepared in this embodiment under 1C coin cell conditions.

[0078]

[0079] As shown in Table 1, the lithium titanate material prepared in this embodiment has a first charge capacity greater than 166 mAh / g, a first discharge capacity greater than 166 mAh / g, and a first charge-discharge efficiency greater than 99.2% under 1C coin cell conditions. This indicates that the lithium titanate material prepared in this embodiment has good charge-discharge performance and can be used to prepare lithium titanate batteries.

[0080] Example 2

[0081] This embodiment provides a method for preparing lithium titanate material, lithium titanate material and its application. Compared with the preparation method of lithium titanate material in Example 1, the only difference in the preparation method of lithium titanate material in this embodiment is that the calcination temperature in step S1.4 is replaced with "550℃".

[0082] CR2016 coin cells were prepared using the prepared lithium titanate material. After standing for 8 hours and the open circuit voltage stabilized, the current density relative to the negative electrode was set to 1C for charge and discharge tests. The charging cutoff voltage was 2.7V, and after standing for 1 minute, the discharge cutoff voltage was 1.5V. The first charge capacity and the first discharge capacity were recorded, and the first charge and discharge efficiency was calculated.

[0083] A total of five parallel samples were tested, and the test results are shown in Table 2 below:

[0084] Table 2. Performance overview of the lithium titanate material prepared in this embodiment under 1C coin cell conditions.

[0085]

[0086]

[0087] As shown in Table 2, the lithium titanate material prepared in this embodiment exhibits an initial charge capacity of 153.8 mAh / g to 157.6 mAh / g and an initial discharge capacity of 153.6 mAh / g to 156.8 mAh / g under 1C coin charge conditions, with an initial charge-discharge efficiency greater than 99.1%. This indicates that the lithium titanate material prepared in this embodiment has good charge-discharge performance. The charge-discharge performance of the lithium titanate material prepared in this embodiment is slightly worse than that of the lithium titanate material prepared in Example 1. This may be because the calcination temperature was lower, resulting in residual conductive carbon black in the prepared lithium titanate material.

[0088] Example 3

[0089] This embodiment provides a method for preparing lithium titanate material, lithium titanate material and its application. Compared with the method for preparing lithium titanate material in Example 1, the only difference in the method for preparing lithium titanate material in this embodiment is that the calcination temperature in step S1.4 is replaced with "760℃".

[0090] CR2016 coin cells were prepared using the prepared lithium titanate material. After standing for 8 hours and the open circuit voltage stabilized, the current density relative to the negative electrode was set to 1C for charge and discharge tests. The charging cutoff voltage was 2.7V, and after standing for 1 minute, the discharge cutoff voltage was 1.5V. The first charge capacity and the first discharge capacity were recorded, and the first charge and discharge efficiency was calculated.

[0091] A total of five parallel samples were tested, and the test results are shown in Table 3 below:

[0092] Table 3. Performance overview of the lithium titanate material prepared in this embodiment under 1C coin cell conditions.

[0093]

[0094] As shown in Table 3, the lithium titanate material prepared in this embodiment exhibits an initial charge capacity of 160.7 mAh / g to 162.8 mAh / g and an initial discharge capacity of 159.2 mAh / g to 161.1 mAh / g under 1C coin cell conditions, with an initial charge / discharge efficiency greater than 99%, indicating that the lithium titanate material prepared in this embodiment has good charge / discharge performance. The charge / discharge performance of the lithium titanate material prepared in this embodiment is slightly lower than that of the lithium titanate material prepared in Example 1. This may be because the calcination temperature was higher, resulting in a "caking" phenomenon in the prepared lithium titanate material.

[0095] Example 4

[0096] This embodiment provides a method for preparing lithium titanate material, lithium titanate material and its application. Compared with the method for preparing lithium titanate material in Embodiment 1, the only difference in the method for preparing lithium titanate material in this embodiment is that the molar ratio of titanium element to lithium element in the material in step S1.4 is replaced with "1:0.8".

[0097] CR2016 coin cells were prepared using the prepared lithium titanate material. After standing for 8 hours and the open circuit voltage stabilized, the current density relative to the negative electrode was set to 1C for charge and discharge tests. The charging cutoff voltage was 2.7V, and after standing for 1 minute, the discharge cutoff voltage was 1.5V. The first charge capacity and the first discharge capacity were recorded, and the first charge and discharge efficiency was calculated.

[0098] A total of five parallel samples were tested, and the test results are shown in Table 4 below:

[0099] Table 4. Performance overview of the lithium titanate material prepared in this embodiment under 1C coin cell conditions.

[0100]

[0101] As shown in Table 4, the lithium titanate material prepared in this embodiment exhibits an initial charge capacity of 156.8 mAh / g to 158.6 mAh / g and an initial discharge capacity of 156.1 mAh / g to 157.6 mAh / g under 1C coin charge conditions, with an initial charge-discharge efficiency greater than 99.18%. The charge-discharge performance of the lithium titanate material prepared in this embodiment is slightly worse than that of the lithium titanate material prepared in Example 1. Due to the smaller amount of lithium source added, trace amounts of titanium dioxide are present in the prepared lithium titanate material, resulting in a slightly lower purity compared to the lithium titanate material prepared in Example 1.

[0102] Example 5

[0103] This embodiment provides a method for preparing lithium titanate material, lithium titanate material and its application. Compared with the method for preparing lithium titanate material in Embodiment 1, the only difference in the method for preparing lithium titanate material in this embodiment is that the molar ratio of titanium element in the material to lithium element in the lithium carbonate in step S1.4 is replaced with "1:0.9".

[0104] CR2016 coin cells were prepared using the prepared lithium titanate material. After standing for 8 hours and the open circuit voltage stabilized, the current density relative to the negative electrode was set to 1C for charge and discharge tests. The charging cutoff voltage was 2.7V, and after standing for 1 minute, the discharge cutoff voltage was 1.5V. The first charge capacity and the first discharge capacity were recorded, and the first charge and discharge efficiency was calculated.

[0105] A total of five parallel samples were tested, and the test results are shown in Table 5 below:

[0106] Table 5. Performance overview of the lithium titanate material prepared in this embodiment under 1C coin cell conditions.

[0107]

[0108] As shown in Table 5, the lithium titanate material prepared in this embodiment exhibits an initial charge capacity of 153.4 mAh / g to 157.6 mAh / g and an initial discharge capacity of 153.1 mAh / g to 156.8 mAh / g under 1C coin charge conditions, with an initial charge-discharge efficiency greater than 99.16%. The charge-discharge performance of the lithium titanate material prepared in this embodiment is slightly worse than that of the lithium titanate material prepared in Example 1. Due to the higher amount of lithium source added, trace amounts of metalithium titanate are present in the prepared lithium titanate material, resulting in a slight decrease in the electrochemical performance of the lithium titanate material prepared in this embodiment compared to that prepared in Example 1.

[0109] The preparation method, materials, and applications of lithium titanate provided in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing lithium titanate material, characterized in that, The lithium titanate material is used to prepare lithium titanate batteries. The lithium titanate material has a spherical structure. The preparation method of the lithium titanate material includes the following steps: A lithium titanate electrode sheet is provided, the lithium titanate electrode sheet comprising an electrode current collector and a first coating coated on the electrode current collector, the first coating being made of lithium titanate. The lithium titanate electrode sheet is placed in an alkaline solution, and the electrode current collector is dissolved in the alkaline solution to obtain a first mixture containing the lithium titanate. The first mixture is subjected to solid-liquid separation to obtain a solid second mixture, the second mixture comprising the lithium titanate; and The second mixture and a lithium source are calcined in an oxygen-containing atmosphere to obtain lithium titanate material; In the step of calcining the second mixture and the lithium source, the molar ratio of titanium in the second mixture to lithium in the lithium source is 1:(0.83-0.89); the calcination is carried out at a pressure of 0.2 MPa to 0.6 MPa.

2. The preparation method according to claim 1, characterized in that, The pH of the alkaline solution is not less than 10; and / or The solute in the alkaline solution is selected from one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide; and / or The solvent for the alkaline solution is water.

3. The preparation method according to claim 1, characterized in that, In the step of solid-liquid separation of the first mixture, the solid-liquid separation includes one or more of the following: vacuum filtration, centrifugation, reverse osmosis, membrane filtration, nanofiltration, ultrafiltration, microfiltration, and gravity sedimentation.

4. The preparation method according to claim 1, characterized in that, After the step of performing solid-liquid separation on the first mixture and before the step of obtaining the solid second mixture, the preparation method further includes the steps of: collecting the first solid obtained by the solid-liquid separation, washing the first solid with water once or multiple times, and then drying it to obtain the second solid; the second mixture is the second solid; Alternatively, after the step of solid-liquid separation of the first mixture and before the step of obtaining the solid second mixture, the preparation method further includes the steps of: collecting the first solid obtained by the solid-liquid separation, crushing the first solid to obtain a third solid of 50 mesh to 300 mesh; the second mixture is the third solid; Alternatively, after the step of solid-liquid separation of the first mixture and before the step of obtaining the solid second mixture, the preparation method further includes the steps of: collecting the first solid obtained by the solid-liquid separation, washing the first solid with water once or multiple times, and then drying it to obtain the second solid; crushing the second solid to obtain a fourth solid of 50 mesh to 300 mesh; and the second mixture being the fourth solid.

5. The preparation method according to claim 1, characterized in that, The lithium source is selected from one or more lithium hydroxides and lithium salts.

6. The preparation method according to claim 1, characterized in that, The calcination treatment temperature is 550℃~760℃; and / or The mass of the second mixture is 100g to 300g, and the calcination time is 1h to 4h.

7. A lithium titanate material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 6.

8. A lithium titanate battery, characterized in that, The lithium titanate battery includes a lithium titanate negative electrode sheet, the lithium titanate negative electrode sheet includes a negative electrode current collector and a second coating coated on the negative electrode current collector, the material of the second coating including lithium titanate material prepared by the preparation method according to any one of claims 1 to 6.

9. The lithium titanate battery according to claim 8, characterized in that, The lithium titanate battery has an initial charge capacity of 150.0 mAh / g to 170.0 mAh / g under 1C coin charge conditions, an initial discharge capacity of 150.0 mAh / g to 170.0 mAh / g under 1C coin charge conditions, and an initial charge / discharge efficiency of greater than 99% under 1C coin charge conditions.

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