Titanium-based negative electrode material, preparation method thereof, negative electrode plate, lithium battery and electric equipment

Abstract

The invention relates to the field of lithium ion batteries, and discloses a titanium-based negative electrode material and a preparation method thereof, a negative electrode plate, a lithium battery and electric equipment. The titanium-based negative electrode material disclosed by the invention comprises Na2Li2Ti6O14 serving as a first phase and anatase type titanium dioxide serving as a second phase. The anatase type titanium dioxide is added on the basis of sodium lithium titanate to serve as a second phase, more phase interfaces are obtained through introduction of the titanium dioxide phase in the composite material, additional lithium storage sites are provided, great help is provided for improving the capacity performance of the material, and the problem that the specific capacity of the material is low is solved; in addition, the problem of poor conductivity of titanium dioxide can be solved by further adding a coating carbon layer, and the coulombic efficiency of the material is further improved. The titanium-based composite material is simple in synthesis method, low in cost, safe and harmless to the environment and more suitable for industrial popularization.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion batteries, in particular to a titanium-based negative electrode material, a preparation method thereof, a negative electrode sheet, a lithium battery and an electric device. BACKGROUND

[0002] In recent years, MLi2Ti6O 14 (M=Ba, Pb, Sr, 2Na) titanium-based negative electrode materials have gradually attracted attention. Among them, sodium lithium titanate (Na2Li2Ti6O 14 ) as a possible application value of lithium ion battery negative electrode material has the advantages of relatively low discharge platform, relatively high ionic conductivity, relatively high theoretical specific capacity, and no solid electrolyte film formed during charging and discharging, etc. Therefore, the lithium ion battery assembled with a suitable positive electrode material can obtain a lithium ion battery with high output voltage, high rate capacity, good cycle performance, long service life and safety, and is expected to meet the power demand of electric vehicles. Moreover, the raw material sodium source material required by this material is cheap and abundant, which greatly reduces the cost of the material. However, the problem limiting the application of sodium lithium titanate (Na2Li2Ti6O 14 ) is that its actual capacity is low, which is manifested as low specific capacity during charging and discharging. SUMMARY

[0003] Therefore, the purpose of the present application is to provide a titanium-based negative electrode material and a preparation method thereof, so that the charging and discharging specific capacity of the titanium-based negative electrode material is significantly improved. Another purpose of the present application is to provide a negative electrode sheet, a lithium ion battery and an electric device based on the above-mentioned titanium-based negative electrode material.

[0004] In order to solve the above technical problems / achieve the above purposes or at least partially solve the above technical problems / achieve the above purposes, as a first aspect of the present application, a titanium-based negative electrode material is provided, which comprises Na2Li2Ti6O 14 as a first phase and anatase titanium dioxide as a second phase.

[0005] Optionally, the mass ratio of Na2Li2Ti6O 14 and anatase titanium dioxide is (320-360):(40-80).

[0006] Further optionally, it further comprises a carbon coating layer, and the carbon coating layer coats the first phase and the second phase.

[0007] As a second aspect of the present application, a preparation method of the titanium-based negative electrode material is provided, which comprises: S1. Sodium source, lithium source and first titanium source are weighed according to the atomic ratio of sodium lithium titanate, mixed thoroughly, and then calcined to obtain Na2Li2Ti6O 14 ; S2. The Na2Li2Ti6O 14 is mixed with a second titanium source, and then sintered in a protective gas atmosphere to obtain the titanium-based negative electrode material; the second titanium source includes anatase titanium dioxide.

[0008] Optionally, S1 includes: Sodium source, lithium source and first titanium source are weighed according to the atomic ratio of sodium lithium titanate, mixed thoroughly, and then first calcined to obtain Na2Li2Ti6O 14 primary particles, and then the Na2Li2Ti6O 14 primary particles are second calcined at a temperature not higher than the first calcination temperature to obtain Na2Li2Ti6O 14 secondary particles.

[0009] Further optionally, the first calcination temperature is 800-1000℃, and the second calcination temperature is 600-800℃.

[0010] Further optionally, S2 further includes: A carbon source is added and mixed with the Na2Li2Ti6O 14 and the second titanium source.

[0011] As a third aspect of the present 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-based negative electrode material described in the present application, a binder and a conductive agent.

[0012] As a fourth aspect of the present application, a lithium ion battery is provided, including a positive electrode sheet, a negative electrode sheet described in the present application, and a separator and an electrolyte.

[0013] As a fifth aspect of the present application, an electrical device is provided, including the lithium ion battery described in the present application, which provides electrical energy for the electrical device or serves as an energy storage unit of the electrical device.

[0014] The present application adds anatase titanium dioxide as a second phase on the basis of sodium lithium titanate, and the introduction of anatase titanium dioxide phase in the composite material provides more phase interfaces and additional lithium storage sites, which greatly helps to improve the capacity performance of the material and solves the problem of low specific capacity of the material. In addition, the poor conductivity of titanium dioxide can be further solved by adding a carbon coating layer, thereby improving the coulombic efficiency of the material. The synthesis method of the titanium-based composite material of the present application is relatively simple, low in cost, safe to the environment, and more suitable for industrialization. Attached Figure Description

[0015] Figure 1 The diagram shown is a process flow chart for the preparation of the titanium-based anode material of this application; where NLTO represents sodium lithium titanate. Figure 2 The image shown is the XRD pattern of the titanium-based anode material of Example 2 of this application; Figure 3 The image shown is the XRD pattern of the titanium-based anode material of Example 3 of this application. Detailed Implementation

[0016] This application discloses a titanium-based anode material and its preparation method, as well as anode sheets, lithium batteries, and electrical devices. 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 is particularly important to note 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.

[0017] 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.

[0018] Sodium lithium titanate has a high theoretical specific capacity (281.6 mAh / g), excellent structural stability and safety, but its slow ion diffusion ability prevents it from achieving its theoretical performance in practical applications. In actual lithium-ion battery tests, its reversible capacity is usually far lower than its theoretical capacity.

[0019] In view of the current status and shortcomings of the prior art, in the first aspect of this application, a titanium-based anode material is provided, comprising Na2Li2Ti6O as the first phase. 14 Anatase titanium dioxide, as the second phase, has a smaller particle size and adheres to the surface of sodium lithium titanate. At the interface, these two substances with different crystal structures generate numerous lattice mismatches and defects for lattice matching, the most common and important of which are oxygen vacancies. Oxygen vacancies are not only an effective way to improve electronic conductivity but can also serve as a new lithium storage active site. Lithium ions can undergo adsorption / desorption reactions with oxygen vacancies or store charge by filling unsaturated bonds surrounding the vacancies. This surface / interface-based pseudocapacitive behavior provides additional capacity beyond bulk intercalation reactions, directly contributing to the increase in overall specific capacity.

[0020] Insufficient anatase titanium dioxide will result in insufficient lithium storage sites, limiting the improvement of the specific capacity of lithium batteries. While the specific capacity of lithium batteries can be further improved by gradually increasing the amount of titanium dioxide, excessive titanium dioxide will crowd out the proportion of the first phase, sodium lithium titanate. Therefore, in some embodiments of this application, the Na2Li2Ti6O... 14 The mass ratio of anatase titanium dioxide to titanium dioxide is chosen to be within a relatively suitable range of (320-360): (40-80).

[0021] As the amount of titanium dioxide gradually increases, the specific capacity of lithium batteries will be further improved. However, this application found that the coulombic efficiency of lithium batteries will decrease. Therefore, this application further improves the titanium-based anode material by adding a carbon coating layer, which coats the first phase and the second phase.

[0022] In a second aspect of this application, a method for preparing the titanium-based anode material described in this application is also provided, comprising: S1. Weigh out the sodium source, lithium source, and first titanium source according to the atomic ratio of lithium titanate, mix thoroughly, and then calcine to obtain Na2Li2Ti6O. 14 ; S2. The Na₂Li₂Ti₆O₅ 14 After being thoroughly mixed with a second titanium source, the mixture is then sintered in a protective gas atmosphere to obtain the titanium-based anode material; the second titanium source includes anatase titanium dioxide.

[0023] In some embodiments of this application, S1 includes: According to the atomic ratio of sodium titanate, the sodium source, lithium source, and first titanium source were weighed and thoroughly mixed, and then subjected to a first calcination to obtain Na₂Li₂Ti₆O. 14 One particle, then Na2Li2Ti6O14 The particles are then subjected to a second calcination at a temperature not exceeding that of the first calcination to obtain Na₂Li₂Ti₆O. 14 Secondary sintering. Secondary sintering can increase the tap density of the material and improve its rate performance. However, it is necessary to ensure that the temperature of the second sintering is not higher than that of the first sintering. If the temperature of the second sintering is higher than that of the first sintering, it will easily lead to the caking of the material.

[0024] In some embodiments of this application, the temperature of the first calcination is 800-1000℃, such as 800℃, 850℃, 900℃, 950℃, 1000℃, or any value between two of these. The temperature of the second calcination is 600-800℃, such as 600℃, 650℃, 700℃, 750℃, 800℃, or any value between two of these. The holding time for the first and second calcinations is independently selected from 1-5 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or any value between two of these.

[0025] In some embodiments of this application, the first titanium source includes one or more of titanium hydroxide (Ti(OH)4), titanium tetrachloride, tetrabutyl titanate, and metatitanic acid; the lithium source includes one or more of lithium hydroxide monohydrate (LiOH.H2O), lithium carbonate, and lithium acetate; and the sodium source includes one or more of sodium carbonate, sodium hydroxide, and sodium acetate.

[0026] In some embodiments of this application, in order to stabilize the coulombic efficiency of the lithium battery, S2 further includes: Adding a carbon source to the aforementioned Na2Li2Ti6O 14 The second titanium source is thoroughly mixed.

[0027] In some embodiments of this application, the carbon source is used in an amount of 3-5% of the total mass of the raw materials, including one or more of glucose, sucrose, citric acid, and polyethylene glycol. A second titanium source and Na₂Li₂Ti₆O₅ are also used. 14 The mass ratio is (40-80):(320-360), and the second titanium source includes anatase titanium dioxide.

[0028] In some embodiments of this application, the sintering temperature in S2 is 380-420°C, and the holding time is 1-5h, for example, 1h, 2h, 3h, 4h, 5h or any value between the two; too low a temperature is not conducive to carbonization of the carbon source, while too high a temperature will generate rutile titanium dioxide, affecting the performance of the material.

[0029] In some embodiments of this application, the thorough mixing includes, but is not limited to, thoroughly stirring the materials in a solvent, thoroughly mixing the materials by grinding, thoroughly mixing by ultrasound, etc. The solvent typically includes water, or a suitable organic solvent selected based on the polarity of the raw materials. The thoroughly mixed materials can be dried by spray drying or other methods before calcination and sintering. In other embodiments of this application, the process parameters for spray drying include: Inlet temperature 260℃±3℃, outlet temperature 106℃-115℃, pressure 0.30Mpa, air flow rate 4.8-5.6L / h, feed rate 25-32rpm.

[0030] In some embodiments of this application, each material is typically sieved, for example, through a 200-mesh sieve, before proceeding to the next step, in order to ensure that the powder is within a suitable particle size range.

[0031] 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-based negative electrode 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%.

[0032] 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.

[0033] In some embodiments of this application, the adhesive may be selected from some adhesives known 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.

[0034] 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.).

[0035] 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.

[0036] 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.

[0037] 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.

[0038] In some embodiments of this application, the positive electrode, the negative electrode, and the separator can be fabricated into an electrode assembly by a winding process or a stacking process.

[0039] In some embodiments of this application, the lithium-ion battery may include an outer packaging. This outer packaging can be used to encapsulate the aforementioned electrode components and electrolyte. In other embodiments of this application, the outer packaging of the lithium-ion battery may be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging of the lithium-ion battery may also be a soft pack, such as a pouch.

[0040] 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.

[0041] 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.

[0042] The following provides a further description of a titanium-based anode material, its preparation method, anode sheet, lithium battery, and electrical equipment provided in this application.

[0043] Example 1: Weigh 5923.72 mL of deionized water and add it to the mixing tank, adjusting the speed to 1000 rpm. Weigh 203.17 g of sodium carbonate (Na2CO3) and 162.61 g of lithium hydroxide (LiOH.H2O) and add them to the mixing tank. After the sodium carbonate (Na2CO3) and lithium hydroxide (LiOH.H2O) dissolve, add 1115.15 g of titanium hydroxide (Ti(OH)4) and stir for 18 h. Adjust the inlet temperature of the spray dryer to 260℃±3℃, the outlet temperature to 106℃-112℃, the pressure to 0.3 MPa, and the gas flow rate to 4.8-5.2 L / min. After the outlet temperature stabilizes, start feeding at a feed rate of 34 rpm. Calcinate the spray-dried material at 900℃ for 4 h, and then sieve the calcined material through a 200-mesh sieve.

[0044] Weigh 1600 mL of deionized water and add it to a mixing tank, adjusting the speed to 1000 rpm. Weigh 400 g of NLTO-900 and add it to the mixing tank, stirring for 4 hours. Add the uniformly mixed slurry to a ball mill jar, set the ball mill speed to 3000 rpm, and ball mill the slurry. Spray dry the slurry, adjusting the inlet temperature to 260℃±3℃, the outlet temperature to 108℃-115℃, the pressure to 0.30 MPa, and the air flow rate to 5.2-5.6 m³ / h. After the outlet temperature stabilizes, feed the material at a rate of 25-32 rpm. Calcinate the spray-dried material at 700℃ in air for 4 hours. After cooling to room temperature, sieve the calcined material through a 200-mesh sieve.

[0045] 1600 mL of deionized water was added to a mixing tank, and the mixing speed was adjusted to 1000 rpm. 360 g of NLTO-700 and 40 g of anatase titanium dioxide were also added to the mixing tank, and the mixture was stirred for 6 hours. The stirred slurry was then spray-dried, with the inlet temperature adjusted to 260℃±3℃, the outlet temperature to 106℃-112℃, the pressure to 0.3 MPa, and the air flow rate to 4.8-5.2 L / min. After the outlet temperature stabilized, the material was fed at a rate of 25-32 rpm. The spray-dried material was then calcined at 400℃ for 4 hours. The calcined material was then sieved through a 200-mesh sieve to obtain the NLTO-TO titanium-based composite material.

[0046] Example 2: Based on the process in Example 1, the masses of sodium lithium titanate NTLO-700 and the second titanium source anatase titanium dioxide were adjusted to 320g and 80g, respectively.

[0047] XRD analysis was performed on the powder obtained after calcination, see attached figure. Figure 2 As can be seen from the XRD pattern of the NLTO-TO titanium-based composite material, the synthesized pure-phase NLTO anode material corresponds one-to-one with the standard card. A small peak near 25° corresponds to the peak on the standard card for titanium dioxide.

[0048] Example 3: Based on the process in Example 2, an additional 16g of carbon source glucose was added and sintered with sodium lithium titanate NTLO-700 and a second titanium source anatase titanium dioxide. The process flow diagram is shown below. Figure 1 .

[0049] XRD analysis was performed on the powder obtained after calcination, see attached figure. Figure 3 As can be seen from the figure, the XRD pattern of the NLTO-TO titanium-based composite material shows the synthesized pure-phase NLTO anode material, which corresponds one-to-one with the standard card. There is a small peak near 25°, corresponding to the peak on the titanium dioxide standard card. After carbon coating, the carbon peak does not show a peak shape in the XRD, unlike the XRD pattern of Example 2 without carbon coating. Figure 1 To.

[0050] Comparative Example 1: Only the NLTO-700 prepared in Example 1 was used.

[0051] Comparative Example 2: The process is the same as in Example 3, except that a second sintering is not performed to prepare NLTO-700, but instead NLTO-900 prepared by the first calcination is used directly.

[0052] Comparative Example 3: The process is the same as in Example 3, except that the amount of anatase titanium dioxide added is 20g and NLTO-700 is 380g when the materials are compounded, while other parameters remain unchanged.

[0053] Comparative Example 4: The process is the same as in Example 3, except that the amount of anatase titanium dioxide added is 100g and NLTO-700 is 300g when the materials are compounded, while other parameters remain unchanged.

[0054] Experimental example: Half-cell fabrication and testing: The samples obtained from the examples and comparative examples were assembled into CR2025 coin-shaped half-cells, using pure lithium foil as the counter electrode. A mixture of active material, carbon black, and polyvinylidene fluoride (PVDF) in a weight ratio of 8:1:1 was weighed and uniformly dissolved in N-methyl-2-pyrrolidone (NMP). The slurry was then adhered to a copper foil current collector and vacuum dried at 110°C for 12 h. The dried foil was then cut into circular electrode sheets with a diameter of 14 mm, which were used as cathodes. Half-cells were assembled in an argon-filled glove box. The oxygen and moisture content in the glove box was below 0.1 ppm. The electrolyte was a 1 mol L⁻¹ LiPF₆ solution dissolved in a 1:1:1 (v / v / v) mixture of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC). Celgard 2400 film was used as a separator. The prepared half-cell was placed on the Xinwei test cabinet for electrochemical performance testing, with a test voltage range of 0.5-3.0V.

[0055] The results are shown in Table 1 below; Table 1

[0056] As can be seen from the results in Table 1, Comparative Example 1 contains only Na₂Li₂Ti₆O₂. 14 The initial charge and discharge capacities of the materials did not exceed 115 mAh / g, which is significantly lower than the performance of the titanium-based anode material in the embodiments of this application; Comparative Example 2 prepared Na2Li2Ti6O by sintering at 900℃ only once. 14 The phenomenon that its first charge and discharge specific capacity is lower indicates that the tap density of the first sintered lithium sodium titanate is lower, and there is a significant difference in specific capacity. In the titanium-based anode material of this application, the specific capacity gradually increases with the increase of titanium dioxide content, but the coulombic efficiency gradually decreases. However, this is improved after carbon coating, and the capacity is further increased.

[0057] Comparative Examples 3 and 4 are experimental groups where the mass ratio of sodium lithium titanate and anatase titanium dioxide was changed. In Comparative Example 3, the proportion of titanium dioxide was too small, and the improvement effect was not as good as that of the Example. In Comparative Example 4, the proportion of titanium dioxide was too high. Although it also had a high charge-discharge specific capacity, the coulombic efficiency was further reduced.

[0058] 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-based negative electrode material, characterized by, comprising as a first phase Na2Li2Ti6O 14 and as a second phase anatase titanium dioxide.

2. The titanium-based anode material of claim 1, wherein, The mass ratio of the Na2Li2Ti6O 14 and the anatase titanium dioxide is (320-360):(40-80).

3. The titanium-based anode material of claim 1 or 2, wherein, Further comprising a carbon coating layer, the carbon coating layer coating the first phase and the second phase.

4. The method of producing a titanium-based negative electrode material according to claim 1, characterized by, Comprising: S1. The sodium source, lithium source and first titanium source are weighed according to the atomic ratio of sodium titanate, fully mixed, and then calcined to obtain Na2Li2Ti6O 14 ; S2. The Na2Li2Ti6O 14 After being mixed with the second titanium source, the mixture is sintered in a protective gas atmosphere to obtain the titanium-based negative electrode material; the second titanium source comprises anatase titanium dioxide.

5. The preparation method according to claim 4, characterized in that, S1 comprises: The sodium source, the lithium source and the first titanium source are weighed according to the atomic ratio of sodium titanate, fully mixed, then first calcined to obtain Na2Li2Ti6O 14 primary particles, and then the Na2Li2Ti6O 14 primary particles are second calcined at a temperature not higher than that of the first calcination to obtain Na2Li2Ti6O 14 secondary particles.

6. The preparation method according to claim 5, characterized in that, The temperature of the first calcination is 800-1000℃, and the temperature of the second calcination is 600-800℃.

7. The method of any one of claims 4-6, wherein the method further comprises, S2 further comprises: adding a carbon source and the Na2Li2Ti6O 14 and a second titanium source are mixed thoroughly.

8. A negative electrode sheet characterized by comprising: Comprising a current collector, and a negative electrode material coated on the surface of the current collector; the negative electrode material comprising the titanium-based negative electrode material according to any one of claims 1-3, a binder, and a conductive agent.

9. A lithium-ion battery, characterized by Comprising a positive electrode sheet, the negative electrode sheet according to claim 8, a separator, and an electrolyte.

10. An electric device, characterized by The lithium ion battery according to claim 9 provides electric energy for the electric device or serves as an energy storage unit of the electric device.

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