Titanium-carbon double-coated lithium titanate material, preparation method thereof, negative electrode sheet, lithium battery and electric device

Abstract

The application relates to the field of lithium ion batteries, and discloses a titanium-carbon double-coated lithium titanate material, a preparation method of the titanium-carbon double-coated lithium titanate material, a negative electrode sheet, a lithium battery and an electric device. In the application, fibrous titanium dioxide and carbon materials such as carbon nanotubes are used to modify lithium titanate particles, thereby forming a titanium-carbon double-coated lithium titanate secondary particle material. The fibrous titanium dioxide and the carbon nanotubes coexist in the coating layer and are mutually synergistic, thereby improving the defects of electron transmission and ion transmission of the lithium titanate particles. The existence of the carbon nanotubes and the carbon materials helps to establish a good electron transmission channel and improve electron conductivity. The fibrous titanium dioxide establishes a stable mechanical skeleton and a lithium ion transmission channel. The interweaving of the two materials can effectively prevent the swelling phenomenon of the battery prepared in the later stage, and has better conductivity and ion transmission efficiency, and the later rate can be significantly improved.

Description

Technical Field

[0001] This application relates to the field of lithium-ion batteries, and in particular to a titanium-carbon double-coated lithium titanate material and its preparation method, as well as a negative electrode sheet, a lithium battery, and electrical equipment. Background Technology

[0002] As an anode material, lithium titanate (LTO) has always attracted widespread attention. LTO materials have advantages that other anode materials do not possess: (1) It has a high coulombic efficiency (>94%) and its first discharge specific capacity at 1C rate is close to the theoretical capacity of 175mAh / g; (2) It has a very stable voltage plateau, which is around 1.55V during charging and discharging (vs. Li+ / Li), and its electrochemical performance is stable; (3) The structure is stable and there is no change in the structure during the charging and discharging process, which is called "zero strain". It has a long cycle life and high stability. Compared with carbon materials, lithium ions have better diffusion in LTO. (4) The charging and discharging voltage is generally set at 1 to 3 V (or 1 to 2.5 V), which is compatible with commercial electrolytes, safe to use, and does not easily form SEI film; (5) The titanium source for synthesizing LTO is abundant in nature, inexpensive and environmentally friendly.

[0003] Therefore, LTO, as a novel anode material, possesses significant advantages not found in other anode materials, attracting increasing attention from researchers. In particular, LTO exhibits a stable charge-discharge platform and zero-strain structural performance during charge and discharge, greatly improving the safety performance of lithium-ion batteries and providing excellent cycle stability, thus ensuring its potential as a power source anode material in future electric vehicles. However, the poor conductivity and low diffusion coefficient of LTO anode materials directly affect their high-rate performance, severely hindering their practical application. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a titanium-carbon double-coated lithium titanate material and its preparation method, so that the lithium titanate material can significantly improve the discharge capacity retention rate of the battery at high rates.

[0005] Another objective of this application is to provide a negative electrode, a lithium-ion battery, and an electrical device based on the aforementioned titanium-carbon double-coated lithium titanate material.

[0006] In order to solve the above-mentioned technical problems / achieve the above-mentioned objectives, or at least partially solve the above-mentioned technical problems / achieve the above-mentioned objectives, as a first aspect of this application, a titanium-carbon dual-coated lithium titanate material is provided, comprising a core and a coating layer, wherein the core comprises lithium titanate and the coating layer comprises fibrous titanium dioxide and carbon material.

[0007] Optionally, the carbon material includes carbon nanotubes.

[0008] As a second aspect of this application, a method for preparing the titanium-carbon dual-coated lithium titanate material described in this application is provided, comprising: Provides primary lithium titanate granules; The lithium titanate primary particles, fibrous titanium dioxide and carbon material precursor are brought into full contact to obtain a sintering precursor. The sintering precursor is sintered in a protective gas atmosphere to obtain the titanium-carbon double-coated lithium titanate material.

[0009] Optionally, the fibrous titanium dioxide is prepared by the following method: K2CO3 and TiO2 react at high temperature to produce fibrous potassium titanate, which is then subjected to ion exchange through acid washing to obtain the fibrous titanium dioxide.

[0010] Further optionally, the high temperature includes 800-1200°C.

[0011] Optionally, the carbon material precursor includes carbon nanotubes.

[0012] Optionally, the sintering includes sintering at 600-900℃ for 2-6 hours.

[0013] As a third aspect of this application, a negative electrode sheet is provided, including a current collector and a negative electrode material coated on the surface of the current collector; the negative electrode material includes the titanium-carbon double-coated lithium titanate material, binder and conductive agent described in this application.

[0014] As a fourth aspect of this application, a lithium-ion battery is provided, including a positive electrode, a negative electrode as described in this application, a separator, and an electrolyte.

[0015] As a fifth aspect of this application, an electrical device is provided, including the lithium-ion battery described in this application, wherein the lithium-ion battery provides electrical energy to the electrical device or serves as an energy storage unit for the electrical device.

[0016] This application modifies lithium titanate particles using fibrous titanium dioxide and carbon nanotubes, forming a titanium-carbon double-coated secondary lithium titanate particle material. The fibrous titanium dioxide and carbon nanotubes present in the coating layer synergistically improve the electron and ion transport defects of the lithium titanate particles. The presence of carbon nanotubes and other carbon materials helps establish good electron transport channels and improve electronic conductivity, while the fibrous titanium dioxide establishes a stable mechanical framework and lithium-ion transport channels. The interweaving of these two materials not only effectively prevents gas expansion during later battery fabrication but also provides better conductivity and ion transport efficiency, resulting in a significant improvement in rate capability. Attached Figure Description

[0017] Figure 1 The XRD patterns of Example 1 and Comparative Example 1 are shown below; Figure 2 The figures shown are discharge rate curves for the embodiments and comparative examples. Detailed Implementation

[0018] This application discloses a titanium-carbon double-coated lithium titanate material and its preparation method, as well as a negative electrode sheet, lithium battery, and electrical equipment. Those skilled in the art can refer to the content of this application and appropriately modify the process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this application. The products, processes, and applications described in this application have been described through preferred embodiments. Those skilled in the art can obviously modify or appropriately change and combine the preparation methods described herein without departing from the content, spirit, and scope of this application to realize and apply the technology of this application. Obviously, the described embodiments are only some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are within the scope of protection of this application.

[0019] It should be noted that, in this document, relational terms such as "first" and "second," "step 1" and "step 2," and "(1)" and "(2)" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Moreover, the embodiments and features described in this application can be combined with each other without conflict.

[0020] Sodium lithium titanate possesses high theoretical specific capacity, excellent structural stability, and safety. However, its two major bottlenecks at high rates are slow electron conduction and slow ion diffusion, resulting in poor capacity retention at high rates (e.g., 10C). To address this deficiency in lithium titanate materials, in the first aspect of this application, a titanium-carbon double-coated lithium titanate secondary particle material is provided by modifying primary lithium titanate particles. This material includes a core and a coating layer, wherein the core comprises lithium titanate, and the coating layer comprises fibrous titanium dioxide and carbon materials.

[0021] At high rates (e.g., 10C), the current increases dramatically. Traditional LTO electrodes, relying on point-contact conductive agent networks, cannot rapidly transfer electrons, leading to a surge in polarization and a sharp drop in capacity. Simultaneously, lithium-ion diffusion in solid-state materials is a slow process; at high rates, lithium ions do not have enough time to penetrate deep into the particles, with only the surface participating in the reaction, resulting in insufficient capacity. This application incorporates fibrous titanium dioxide for modification. On one hand, it acts as a framework, providing mechanical support for the final lithium titanate secondary particles, effectively suppressing the agglomeration, pulverization, and breakage of secondary particles during cycling and electrode rolling. On the other hand, the fibrous titanium dioxide provides interfacial channels for lithium-ion migration, and the interwoven network structure prevents the dense stacking of LTO particles, ensuring sufficient electrolyte wetting and creating a low-resistance path for ion transport, thus contributing to improved rate performance. If granular titanium dioxide is used, a particle stacking effect is highly likely, not only providing limited mechanical support but also occupying space and hindering ion conduction.

[0022] Simultaneously, this application also incorporates a carbon precursor combined with fibrous titanium dioxide to modify the primary lithium titanate particles. After sintering, the carbon precursor forms a continuous or discontinuous carbon layer, which interweaves with the fibrous titanium dioxide and coats the LTO primary particles, further improving the particle's mechanical structure and forming a three-dimensional conductive network to enhance electron transport rate. The synergistic effect of these two materials simultaneously addresses the two major issues of "electron transport efficiency" and "ion transport efficiency" in LTO materials, while also improving its structural stability.

[0023] In some embodiments of this application, the carbon material refers to a continuous or discontinuous structural material mainly composed of carbon elements, constructed on the surface or in the bulk phase of an active material through physical or chemical methods, and designed to improve the electrochemical performance of the electrode. It can be a carbon material (mainly amorphous carbon material) formed by sintering and carbonizing a carbon material precursor (e.g., organic carbon sources such as glucose, sucrose, and pitch), or it can be a highly ordered carbon material that has already undergone carbon transformation (e.g., carbon nanotubes).

[0024] In other embodiments of this application, the carbon material includes carbon nanotubes. The carbon nanotubes are tubular structures composed of 10-20 layers of graphene, prepared by chemical vapor deposition, with a particle size distribution of 15-20 nm and a specific surface area of ​​approximately 200 m². 2 / g. Using carbon nanotubes allows for the construction of a three-dimensional conductive network on the surface of LTO primary particles, which is more conducive to high-speed electron transfer. Furthermore, carbon nanotubes, in conjunction with fibrous titanium dioxide, form a three-dimensional framework, ensuring the structural integrity of the electrode during long-term high-rate cycling, which is fundamental to improved capacity retention. Compared to directly using carbon nanotubes, carbon materials formed by sintering and carbonizing organic carbon sources such as glucose, while exhibiting relatively better interfacial stability, rely on point contacts between particles for electron conduction. This leads to more severe polarization at high rates and more significant capacity decay. Moreover, the dense carbon layer and lower porosity slow down lithium-ion diffusion, which is also detrimental to high-rate performance.

[0025] In a second aspect of this application, a method for preparing the titanium-carbon double-coated lithium titanate material is also provided, comprising: Provides primary lithium titanate granules; The lithium titanate primary particles, fibrous titanium dioxide and carbon material precursor are brought into full contact to obtain a sintering precursor. The sintering precursor is sintered in a protective gas atmosphere to obtain the titanium-carbon double-coated lithium titanate material.

[0026] In some embodiments of this application, the primary lithium titanate particles can be prepared by the following method: Weigh out two raw materials according to the molar ratio of lithium source and titanium source for lithium titanate. The molar ratio is usually between 1:0.8 and 1:0.88. Mix the lithium source and titanium source thoroughly in deionized water. If necessary, a dispersant can be added. Then, ball mill the two raw materials to ensure full contact. Spray dry to form a precursor for lithium titanate sintering. Then, sinter in air at 600-800℃ for 1-5 hours to obtain primary lithium titanate particles.

[0027] In some embodiments of this application, the lithium source includes, but is not limited to, TiO2 and / or metatitanic acid, and the titanium source includes, but is not limited to, any one or more of LiOH·H2O and lithium carbonate.

[0028] In some embodiments of this application, the fibrous titanium dioxide is prepared by the following method: K2CO3 and TiO2 react at high temperature to produce fibrous potassium titanate, which is then subjected to ion exchange through acid washing to obtain the fibrous titanium dioxide.

[0029] In other embodiments of this application, the K2CO3 and TiO2 are first thoroughly mixed by ball milling, dried, calcined at high temperature, then rapidly cooled to room temperature, and finally acid-washed with dilute hydrochloric acid. The preferred mass ratio of K2CO3 to TiO2 is 1:1.73.

[0030] In some other embodiments of this application, the high temperature includes 800-1200°C, such as 800°C, 900°C, 1000°C, 1100°C, 1200°C or any value between the two, and the reaction (calcination) time at the high temperature is 10-15h, such as 10h, 12h, 15h or any value between the two.

[0031] In some embodiments of this application, the carbon material precursors include, but are not limited to, glucose, sucrose, pitch, and carbon nanotubes. Although organic carbon source precursors such as glucose have slightly lower performance than carbon nanotubes at high rates, they still have better rate performance and interface stability than lithium titanate materials themselves.

[0032] In some embodiments of this application, the lithium titanate primary particles, fibrous titanium dioxide, and carbon material precursor are brought into full contact by methods including but not limited to ball milling, grinding, and stirring. After full contact, they can be spray-dried or conventionally dried to form a sintering precursor. In other embodiments of this application, the molar ratio of the fibrous titanium dioxide to the titanium source in the lithium titanate primary particles is 1:500-1:200, for example, 1:500, 1:400, 1:300, 1:200, or any value between the two; the mass of the carbon material precursor is 3-6% of the mass of the lithium titanate primary particles, for example, 3%, 4%, 5%, 6%, or any value between the two.

[0033] In some embodiments of this application, the protective gas includes, but is not limited to, nitrogen and inert gas; the sintering includes sintering at 600-900°C for 2-6 hours; for example, sintering at 600°C, 700°C, 800°C or 900°C for 2 hours, 3 hours, 4 hours, 5 hours or 6 hours.

[0034] In a third aspect of this application, a negative electrode sheet is provided, including a current collector and a negative electrode material coated on the surface of the current collector; the negative electrode material includes the titanium-carbon double-coated lithium titanate material described in this application, a binder and a conductive agent, wherein their weight percentages are 80-99%:0.5-10%:0.5-10%, more preferably 90-98%:1-5%:1-5%.

[0035] In some embodiments of this application, the conductive agent may be selected from some conventional conductive agents in the art, including but not limited to superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene or carbon nanofibers.

[0036] In some embodiments of this application, the adhesive may be selected from some conventional adhesives in the art, including but not limited to polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), etc.

[0037] In some embodiments of this application, the current collector may be a metal foil or a composite current collector. For example, copper foil, aluminum foil, etc., may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0038] In some embodiments of this application, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the titanium-carbon double-coated lithium titanate material, conductive agent, binder and any other components in a solvent (e.g., N-methylpyrrolidone), to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0039] In a fourth aspect of this application, a lithium-ion battery is provided, including a positive electrode, a negative electrode as described in this application, a separator, and an electrolyte. Typically, the battery includes a positive electrode and a negative electrode, with the separator disposed between the positive and negative electrodes. The positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process. The lithium-ion battery may include an outer packaging. This outer packaging can be used to encapsulate the aforementioned electrode assembly and electrolyte. In some other embodiments of this application, the outer packaging of the lithium-ion battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the lithium-ion battery can also be a soft pack, such as a pouch. In some other embodiments of this application, the battery can be assembled into a battery module, and the number of batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0040] In some embodiments of this application, the positive electrode sheet can be prepared by referring to the preparation method of the negative electrode sheet. The components of the preparation include positive electrode active material, conductive agent, binder and current collector. The selection of the components can be conventional in the art. The conductive agent, binder and so on can also be selected with reference to the components of the negative electrode sheet, which will not be described in detail here.

[0041] In some embodiments of this application, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1O2 (also known as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 At least one of O2 or its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate or lithium manganese iron phosphate and carbon composites.

[0042] This application does not impose specific limitations on the type of electrolyte, which can be selected according to requirements. For example, the electrolyte can be liquid, gel, or all-solid. In some embodiments of this application, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent. In other embodiments of this application, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, or lithium tetrafluorooxalate phosphate. In other embodiments of this application, the solvent may include at least one selected from ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, ethylene glycol dimethyl ether, methyl ethyl sulfone, or diethyl sulfone.

[0043] In some embodiments of this application, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0044] In a fifth aspect of this application, an electrical device is provided, including the lithium-ion battery described in this application. The lithium-ion battery provides electrical energy to the electrical device and can also be used as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0045] In the comparative experiments provided in this application, unless otherwise specified, all experimental conditions and materials are kept consistent to ensure comparability. Unless otherwise specified, all experimental materials and reagents used in the examples are commercially available.

[0046] The following provides a further description of the titanium-carbon double-coated lithium titanate material, its preparation method, negative electrode sheet, lithium battery, and electrical equipment provided in this application.

[0047] Example 1: 1) Wet premixing Lithium and titanium sources (Li to Ti molar ratio of 1:0.8-1:0.88, using lithium titanate and titanium dioxide) were added to deionized water and mixed thoroughly. Then, a dispersant was added and mixed thoroughly to obtain a homogeneous mixture. The mixture was stirred at a speed of not less than 2000 rpm for 120 minutes.

[0048] 2) One-time ball milling After filling the ball mill with 0.2mm-0.4mm zirconium balls, add slurry for ball milling, with an effective grinding power of 0.5kWh-6kWh. After ball milling the material for 1 hour, the effective power value decreases by 0.1kWh-0.2kWh.

[0049] 3) Spray drying The ball-milled solution is transferred to a spray drying tank. The inlet air temperature of the spray drying tower is 220℃-360℃, and the outlet air temperature is 85℃-115℃. The powder obtained after spraying is the desired powder.

[0050] 4) Calcination The spray-dried material was filled into an alumina crucible and then placed in a muffle furnace for sintering in air. The sintering temperature was 700℃ and the sintering time was 4 hours.

[0051] 5) Secondary ball milling The calcined LTO, fibrous titanium dioxide, carbon nanotubes, and deionized water were added to a ball mill and milled for 3-4 hours. The molar ratio of the fibrous titanium dioxide to the titanium source in step 1 was 1:300. The mass of the carbon nanotubes was 5% of the mass of the calcined lithium titanate.

[0052] The preparation method of fibrous titanium dioxide is as follows: The raw materials for synthesizing titanium dioxide fibers are TiO2 and K2CO3 in a mass ratio of 1.73:1, ball-milled at 1 kWh / kg. The fibers are dried in an oven at 85℃, calcined in a muffle furnace at 1000℃ for 12 hours, and then rapidly cooled to room temperature. After acid washing with 10% dilute hydrochloric acid, the fibers are washed with water until neutral, and then dried to obtain fibrous titanium dioxide.

[0053] 6) Spray drying After ball milling, the solution is transferred to a spray drying tank. The inlet air temperature of the spray drying tower is 180℃-360℃, and the outlet air temperature is 85℃-150℃. The powder obtained after spraying is the desired powder.

[0054] 7) Sintering The spray-dried material was filled into an alumina crucible and then placed in a muffle furnace for sintering in a nitrogen atmosphere. The sintering temperature was 800℃ and the sintering time was 4 hours.

[0055] 8) Sieving The sintered product was sieved. XRD pattern is shown below. Figure 1 The XRD pattern of the sample corresponds one-to-one with the peak positions of the lithium titanate standard card, indicating that the sample is pure-phase lithium titanate.

[0056] Example 2: The preparation process is the same as in Example 1, except that in step 5), carbon nanotubes are replaced with glucose.

[0057] Comparative Example 1: The LTO was prepared using the same process as in Example 1, except that only step 4 was performed to obtain LTO after one calcination.

[0058] Comparative Example 2: The process is the same as in Example 1, except that in step 5), commercially available nano-sized particulate titanium dioxide is used instead of fibrous titanium dioxide.

[0059] Comparative Example 3: The preparation process is the same as in Example 1, except that only carbon nanotubes are used in step 5).

[0060] Comparative Example 4: The process is the same as in Example 1, except that only fibrous titanium dioxide is used in step 5).

[0061] Experimental example: (1) Comparison of particle size of materials from different processes The results are shown in Table 1 below; Table 1 Comparison of particle size of materials from different processes

[0062] According to the results in Table 1, the particle size of the sample in Example 1, which simultaneously added fibrous titanium dioxide and carbon nanotubes, was reduced and was the smallest among all groups.

[0063] (2) Comparison of different process materials with specific surface area and sintered specific capacity The results are shown in Table 2 below; Table 2 Comparison of Sintering Specific Surface Area and Material Composition for Different Processes and Materials

[0064] According to the results in Table 2, the sample in Example 1, which simultaneously added fibrous titanium dioxide and carbon nanotubes, showed the greatest increase in specific capacity among all groups.

[0065] (3) Comparison of battery rate performance of different process materials Weigh out the lithium titanate materials, super pll conductive carbon black, and PVDF in a mass ratio of 9:0.5:0.5 and ball-mill them until homogeneous. Then, coat the mixture onto an aluminum foil current collector to form a thin film. After drying at 80°C, cut it into electrode sheets with a diameter of 14 mm. Using a lithium metal sheet as the negative electrode and the electrode sheet prepared in the above steps as the positive electrode, add a separator, electrolyte, and nickel foam to assemble a CR2025 type laboratory coin cell.

[0066] See results Figure 2 The corresponding data is shown in Table 3; Table 3 Discharge data for each group at different rates

[0067] Depend on Figure 2 As shown in Table 3, the rate performance of the sample in Example 1, which simultaneously added fibrous titanium dioxide and carbon nanotubes, was significantly improved, showing the best effect among all groups. However, the rate performance of LTO single-calcined particles deteriorated as the rate of increase gradually increased. The rate performance of the groups using fibrous titanium dioxide and carbon nanotubes alone, as well as those using nano-sized granular titanium dioxide, was between that of LTO single-calcined particles and the samples in the examples of this application.

[0068] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A titanium-carbon double-coated lithium titanate material, characterized in that, It includes a core and a coating layer, the core comprising lithium titanate and the coating layer comprising fibrous titanium dioxide and carbon materials.

2. The lithium titanate material according to claim 1, characterized in that, The carbon material includes carbon nanotubes.

3. The preparation method of the titanium-carbon double-coated lithium titanate material according to claim 1, characterized in that, include: Provides primary lithium titanate granules; The lithium titanate primary particles, fibrous titanium dioxide and carbon material precursor are brought into full contact to obtain a sintering precursor. The sintering precursor is sintered in a protective gas atmosphere to obtain the titanium-carbon double-coated lithium titanate material.

4. The preparation method according to claim 3, characterized in that, The fibrous titanium dioxide was prepared according to the following method: K2CO3 and TiO2 react at high temperature to produce fibrous potassium titanate, which is then subjected to ion exchange through acid washing to obtain the fibrous titanium dioxide.

5. The preparation method according to claim 4, characterized in that, The high temperature range includes 800-1200℃.

6. The preparation method according to claim 3, characterized in that, The carbon material precursor includes carbon nanotubes.

7. The preparation method according to claim 3, characterized in that, The sintering process includes sintering at 600-900℃ for 2-6 hours.

8. A negative electrode sheet, characterized in that, It includes a current collector and a negative electrode material coated on the surface of the current collector; the negative electrode material includes the titanium-carbon double-coated lithium titanate material as described in any one of claims 1-2, a binder, and a conductive agent.

9. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode as described in claim 8, a separator, and an electrolyte.

10. An electrical appliance, characterized in that, The lithium-ion battery as described in claim 9 is used to provide electrical energy to the electrical device or to serve as an energy storage unit for the electrical device.

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