Low-water-absorption lithium titanate, preparation method thereof, negative pole piece, lithium battery and electric equipment

Abstract

The invention relates to the field of lithium ion batteries, and discloses low-water-absorption lithium titanate, a preparation method thereof, a negative pole piece, a lithium battery and electric equipment. According to the invention, the specific water-resistant polymer protective layer is added on the surface of the lithium titanate material, so that the adsorption to moisture is reduced, the requirement on the humidity of the environment is reduced, and the lithium titanate battery manufacturing process environment is favorably achieved. The prepared lithium titanate pole piece is coated with the protective film, so that the side reaction between the electrolyte and the pole piece after the battery is manufactured in the later period can be reduced, and the gas production problem of the lithium titanate battery can be relieved. The polymer coated protective film on the surface of the lithium titanate material can form a protective layer similar to an SEI (solid electrolyte interface) film in the subsequent charging and discharging process of the lithium titanate battery, so that the stability of the lithium titanate battery is improved. According to the application of the low-water-absorption lithium titanate, the humidity requirement of the lithium titanate battery manufacturing process can be reduced, the lithium titanate battery manufacturing process achievement rate can be improved, the lithium titanate manufacturing process cost and energy consumption can be reduced, and large-scale manufacturing is easy.

Description

Technical Field

[0001] This application relates to the field of lithium-ion batteries, and more particularly to a low-water-absorption lithium titanate, its preparation method, as well as a negative electrode sheet, a lithium battery, and an electrical device. Background Technology

[0002] Lithium-ion batteries have a wide and deep application in new energy, power tools, and 3C digital products, mainly due to their matching of types, performance and cost. For example, low-cost, high-safety lithium iron phosphate batteries are used in large-scale energy storage, while lithium titanate batteries can be used for frequency regulation energy storage that requires high rate, high safety and long life. High-nickel ternary lithium batteries with high energy density and high rate can be used in power tools, while high-voltage lithium cobalt oxide batteries or silicon-carbon batteries with high volumetric energy density are required in mobile phone applications.

[0003] Currently, most batteries in various applications use non-aqueous electrolytes. During battery manufacturing, environmental humidity must be strictly controlled, especially for material systems that are highly sensitive to water, such as lithium titanate and high-nickel cathode materials. High humidity requirements significantly increase manufacturing costs. Lithium titanate materials are more hygroscopic than conventional graphite and ternary materials, mainly due to the characteristics of titanium oxides and lithium content. For lithium titanate batteries, high moisture content severely affects battery stability, including battery swelling and reduced lifespan. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a low-water-absorbing lithium titanate and a method for preparing the same, so that the low-water-absorbing lithium titanate reduces the adsorption of water and decreases the humidity requirement of the environment. The purpose of this application is to provide a low-water-absorbing lithium titanate and its preparation method, so that the battery prepared by the low-water-absorbing lithium titanate can significantly reduce the amount of gas generated during formation and full-charge high-temperature storage. Another objective of this application is to provide a negative electrode, a lithium-ion battery, and an electrical device based on the aforementioned low-water-absorbing lithium titanate.

[0005] 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 low-water-absorption lithium titanate is provided, comprising lithium titanate and a water-resistant polymer, wherein the water-resistant polymer coats the lithium titanate, and the water-resistant polymer comprises one or more of polycarbonate, polysulfone, polyurethane, polyvinyl butyral, polyvinyl chloride, and ABS resin.

[0006] Optionally, the water-resistant polymer accounts for 0.5-5% of the mass of the lithium titanate.

[0007] Optionally, the lithium titanate includes lithium titanate coated with carbon formed by an adhesive, wherein the adhesive includes one or more of sodium carboxymethyl cellulose, sodium alginate, polyacrylic acid, polyvinylpyrrolidone, and chitosan.

[0008] As a second aspect of this application, a method for preparing low-water-absorbing lithium titanate as described in this application is provided, comprising: S1. Lithium titanate is obtained by sintering lithium titanate precursor material, wherein the lithium titanate precursor material includes a titanium source and a lithium source; S2. The lithium titanate and the water-resistant polymer are evenly dispersed and fully contacted. After spray drying, low water absorption lithium titanate coated with water-resistant polymer is obtained.

[0009] Optionally, the lithium titanate precursor material includes a titanium source, a lithium source, and a glue, wherein the glue includes one or more of sodium carboxymethyl cellulose, sodium alginate, polyacrylic acid, polyvinylpyrrolidone, and chitosan.

[0010] Optionally, the mass of the adhesive accounts for 1.5-6% of the mass of the titanium source.

[0011] Optionally, the titanium source includes one or more of titanium dioxide, titanium hydroxide, and metatitanic acid; the lithium source is one or more of lithium oxalate, lithium carbonate, lithium acetate, lithium hydroxide monohydrate, and lithium nitrate.

[0012] 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 low-water-absorbing lithium titanate, binder and conductive agent described in this application.

[0013] 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.

[0014] 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.

[0015] This application adds a specific water-resistant polymer protective layer to the surface of lithium titanate material, thereby reducing moisture adsorption and lowering the humidity requirement, which is beneficial for achieving the desired environmental conditions in lithium titanate battery manufacturing. The resulting lithium titanate electrode has a protective film coating, which reduces side reactions between the electrolyte and the electrode after battery fabrication, helping to alleviate gas generation issues in lithium titanate batteries. Furthermore, the polymer-coated protective film on the surface of the lithium titanate material can form a SEI-like protective layer during subsequent charge and discharge processes, contributing to improved stability of the lithium titanate battery in subsequent applications. The application of this low-water-absorption lithium titanate reduces the humidity requirements in lithium titanate battery manufacturing, improves the process yield, reduces manufacturing costs and energy consumption, and facilitates large-scale production. Attached Figure Description

[0016] Figure 1 The diagram shown is a process flow chart for the preparation of the low-water-absorption lithium titanate material of this application. Figure 2 The image shown is a SEM image of carbon-coated lithium titanate during the preparation process of low-water-absorption lithium titanate in this application. Figure 3 The image shown is the XRD pattern of carbon-coated lithium titanate during the preparation process of low water absorption lithium titanate in this application; ● represents the peak of LTO (COD1001098). Figure 4 The image shown is a SEM image of the low-water-absorbing lithium titanate of this application. Detailed Implementation

[0017] This application discloses a low-water-absorption lithium titanate, 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 result. 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 of this application. 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.

[0018] 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.

[0019] Modifying the surface of lithium titanate can alter its surface state. A common method is carbon coating, which improves both conductivity and surface stability. However, its application in water absorption has not been discussed. Furthermore, doping the lithium titanate surface with other elements, such as F, Tb, Br, and N, can enhance conductivity and rate performance. However, there are few reports on improving water absorption in unmodified lithium titanate bulk materials. In lithium titanate battery manufacturing, controlling ambient humidity is paramount. Additionally, alkali resistance is required for the PVDF binder to reduce slurry viscosity, which is beneficial for subsequent coating, but there is no significant need for moisture suppression.

[0020] Based on the current status and shortcomings of the existing technology, in the first aspect of this application, a low-water-absorption lithium titanate is provided, comprising lithium titanate and a water-resistant polymer, wherein the water-resistant polymer coats the lithium titanate, and the water-resistant polymer includes one or more of polycarbonate, polysulfone, polyurethane, polyvinyl butyral, polyvinyl chloride, and ABS resin. Research in this application has shown that using specific water-resistant polymers for coating can reduce the water absorption of lithium titanate material and reduce the gas production of lithium titanate batteries, while not affecting the electrical performance of the lithium titanate battery.

[0021] In some embodiments of this application, the water-resistant polymer accounts for 0.5-5% of the mass of the lithium titanate. Too little water-resistant polymer cannot achieve complete coating of the lithium titanate surface, while using too much water-resistant polymer will reduce the electronic conductivity of the active material; in some embodiments of this application, the mass of the water-resistant polymer accounts for 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% of the mass of the lithium titanate, or any value between any two.

[0022] In some embodiments of this application, the lithium titanate includes lithium titanate with carbon coating formed by an adhesive, that is, a water-resistant polymer protective layer is coated on the surface of the lithium titanate material with carbon coating formed by an adhesive. The adhesive includes one or more of sodium carboxymethyl cellulose, sodium alginate, polyacrylic acid, polyvinylpyrrolidone, and chitosan. The introduction of carbon coating formed by an adhesive improves the electronic conductivity of the material on the one hand, and enhances the surface stability of the lithium titanate material by utilizing the specific adhesion and three-dimensional network structure characteristics of the adhesive material. It can also help to further improve the water resistance. Without this carbon coating layer, the conductivity is prone to decrease and the structure of the water-resistant polymer protective layer is unstable.

[0023] In a second aspect of this application, a method for preparing low-water-absorption lithium titanate as described in this application is provided, comprising: S1. Lithium titanate is obtained by sintering lithium titanate precursor material, wherein the lithium titanate precursor material includes a titanium source and a lithium source; S2. The lithium titanate and the water-resistant polymer are evenly dispersed and fully contacted. After spray drying, low water absorption lithium titanate coated with water-resistant polymer is obtained.

[0024] In some embodiments of this application, the lithium titanate precursor material includes a titanium source, a lithium source, and a gel. The gel includes one or more of sodium carboxymethyl cellulose, sodium alginate, polyacrylic acid, polyvinylpyrrolidone, and chitosan. These polymeric gel raw materials possess flowability, adhesion, and film-forming ability, playing a role in thickening and promoting uniform dispersion. Generally, carbon sources such as glucose, graphene, carbon nanotubes, and sucrose do not possess this function. This allows them to form a uniform, dense, and strong pre-connection with the active material particles before carbonization. Moreover, the polymeric gel molecular chains contain abundant functional groups, enabling the formation of strong chemical bonds. Simultaneously, during the carbonization process, glassy carbon or hard carbon structures are formed. These carbons are typically isotropic, exhibiting long-range disorder and short-range order, giving them a certain degree of toughness and better buffering the stress generated by the volume expansion / contraction of the active material during charging and discharging. The carbon coating formed by ordinary carbon sources is mainly due to weak physical adsorption or van der Waals forces, and the interfacial bonding force is relatively weak. The resulting carbon layer may be more brittle and prone to cracking under repeated stress. This makes it difficult to stabilize the surface stability of lithium titanate, and thus also makes it difficult to stabilize the stability of the water-resistant polymer protective layer, resulting in a reduction in the low water absorption effect.

[0025] In some other embodiments of this application, the adhesive accounts for 1.5-6% of the mass of the titanium source. Too little adhesive will not achieve the above-mentioned effects and will not thicken the slurry, affecting the uniformity of dispersion. Too much adhesive will reduce the electronic conductivity of the material or make the slurry too thick, affecting subsequent processing. In some embodiments of this application, the titanium source includes one or more of titanium dioxide (TiO2), titanium hydroxide (Ti(OH)4), and metatitanic acid (also known as hydrated titanium dioxide, TiO(OH)2); the lithium source is one or more of lithium oxalate (Li2C2O4), lithium carbonate (Li2CO3), lithium acetate (CH3COOLi), lithium hydroxide monohydrate (LiOH.H2O), and lithium nitrate (LiNO3). The amounts of the titanium and lithium sources are adjusted up or down according to the stoichiometric ratio of 5:4 for forming lithium titanate, and the adjustment is made appropriately based on factors such as compensating for lithium volatilization, optimizing material properties, and differences in precursors and processes. In other embodiments of this application, Ti(OH)4 is used as the titanium source at a dosage of 3000g, and LiOH.H2O is used as the lithium source at a dosage of 1000g.

[0026] In some embodiments of this application, the preparation of lithium titanate precursor material includes: thoroughly mixing a titanium source, a lithium source, and a binder in deionized water, followed by spray drying to obtain the lithium titanate precursor material. The thorough mixing includes, but is not limited to, one or more of stirring, grinding, ball milling, and ultrasonication.

[0027] In some embodiments of this application, the sintering includes calcination at 500-800°C for 1-5 hours; the sintering process is carried out in a protective gas atmosphere, such as nitrogen or an inert gas atmosphere.

[0028] In some embodiments of this application, the lithium titanate and the water-resistant polymer are uniformly dispersed by adding the water-resistant polymer to a dispersant to disperse the lithium titanate material. The dispersant includes one or more of the following: ethanol, acetone, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), isopropanol, ethyl acetate, propylene carbonate, ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, butyrolactone, dimethyl sulfoxide, chloroform, toluene, xylene, tetrahydrofuran, and acetonitrile. Sufficient contact between the lithium titanate and the water-resistant polymer includes, but is not limited to, grinding, stirring, ball milling, and ultrasonication.

[0029] In a third aspect of this application, a negative electrode sheet is provided, comprising a current collector and a negative electrode material coated on the surface of the current collector; the negative electrode material comprises the low-water-absorbing lithium titanate, binder and conductive agent described in this application, wherein their weight percentages are 90-98%:1-5%:1-5% respectively.

[0030] In some embodiments of this application, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0031] In some embodiments of this application, the adhesive includes at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), sodium carboxymethyl cellulose (CMC), ethylene-vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, ethylene-vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, or fluorinated acrylate resin.

[0032] 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.).

[0033] 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.

[0034] During battery charging and discharging, active ions repeatedly insert and extract between the positive and negative electrode plates. The electrolyte acts as a conductor of ions between the positive and negative electrode plates. The separator, positioned between the positive and negative electrode plates, primarily prevents short circuits between the two electrodes while allowing ions to pass through.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] The following provides a further description of the low-water-absorption lithium titanate, its preparation method, negative electrode sheet, lithium battery, and electrical equipment provided in this application.

[0042] Example 1: According to the material preparation process Figure 1 First, 3000g of titanium source Ti(OH)4 (D50: 3μm) and 9000g of deionized water (dispersant) were added to a pre-dispersion tank. Then, 3000g of CMC adhesive (2% titanium source, i.e., 60g) and 1000g of lithium salt LiOH·H2O were added. Dispersion step 1 was performed at 40Hz for 2 hours. After dispersion, the slurry was transferred to a ball mill, diluted with 5000g of deionized water, and then ball milled at 2000r / min for 20 hours to obtain the ball-milled slurry. The resulting slurry was then transferred to a spray drying tank for spray drying step 3 at an inlet temperature of 500°C and an outlet temperature of 150°C, yielding 3411g of white spray powder. Then, calcination step 4 was performed at a temperature of 650°C for 3 hours under a nitrogen inert atmosphere. After calcination, 2142g of gray calcined powder was obtained. The gray color indicates that the powder surface is coated with carbon, mainly as a result of the high-temperature carbonization of the carbon source CMC adhesive.

[0043] 1100g of calcined powder was coated with a water-resistant polymer. First, 44g of the water-resistant polymer, polyvinyl butyral (PVB), was dissolved in 3300g of isopropanol dispersant and poured into a grinding and dispersing tank. Simultaneously, the calcined powder was added, and then grinding was performed in step 5 at a speed of 3500 r / min for 3 hours. The resulting slurry was then spray-dried in step 6 at an inlet temperature of 300°C and an outlet temperature of 90°C, yielding 1053g of spray-dried powder. This completed the material preparation. The proportion of the water-resistant polymer in the calcined powder was 4%.

[0044] The powder obtained after calcination was examined by SEM, see attached. Figure 2 The primary particle size is mostly between 100-200 nm, with a small number of particles around 400 nm. XRD structural analysis of the calcined powder is shown in the appendix. Figure 3 The graph mainly shows the structure of LTO, indicating that LTO is formed after calcination. There are no obvious carbon peaks, mainly due to the small amount used. The morphology after coating with the water-resistant polymer was further examined; the results are shown in the appendix. Figure 4 The adhesion between nanoparticles is mainly a result of polymer coating, indicating that the water-resistant polymer is coated on the surface of LTO particles.

[0045] Example 2: According to the material preparation process Figure 1 First, 3150g of titanium source Ti(OH)4 (D50: 2μm) and 12600g of deionized water were added to a pre-dispersion tank. Then, 4725g of sodium alginate (3% titanium source, 94.5g) and 1000g of lithium salt LiOH·H2O were added for dispersion step 1, with a stirring speed of 50Hz for 1 hour. After dispersion, the slurry was transferred to a ball mill jar, and 5000g of deionized water was added to dilute the slurry. Then, ball milling step 2 was performed at a speed of 1500r / min for 24 hours to obtain the ball-milled slurry. The obtained slurry was then transferred to a spray loading tank for spray drying step 3, with an inlet temperature of 550°C and an outlet temperature of 180°C, to obtain 3435g of white spray powder. Then, calcination step 4 is performed at a temperature of 700°C for 2.5 hours under a nitrogen inert atmosphere. After calcination, 2200g of gray calcined powder is obtained. The gray color indicates that the powder surface is coated with carbon, mainly due to the high-temperature carbonization of the carbon source, sodium alginate.

[0046] 1500g of calcined powder was coated with a water-resistant polymer. First, 30g of the water-resistant polymer PVB was dissolved in 4500g of dispersant isopropanol, and the solution was poured into a grinding and dispersing tank. Simultaneously, the calcined powder was added, and then grinding was performed in step 5 at a speed of 3000 r / min for 3 hours. The resulting slurry was then spray-dried in step 6 at an inlet temperature of 300°C and an outlet temperature of 90°C, yielding 1438g of spray-dried powder. This completed the material preparation. The proportion of the water-resistant polymer in the calcined powder was 2%.

[0047] Example 3: According to the material preparation process Figure 1First, 2174g of TiO2 (D50: 1.5μm) and 9000g of deionized water (dispersant) were added to a pre-dispersion tank. Then, 4348g of PAA adhesive (2% titanium source, 43.5g) and 1217g of lithium oxalate were added. Dispersion step 1 was performed at 45Hz for 1.5 hours. After dispersion, the slurry was transferred to a ball mill, diluted with 4000g of deionized water, and then ball-milled for 24 hours at 1500r / min to obtain the ball-milled slurry. The resulting slurry was then transferred to a spray drying tank for spray drying step 3 at an inlet temperature of 450°C and an outlet temperature of 160°C, yielding 3090g of white spray powder. Then, calcination step 4 was performed at a temperature of 750°C for 2.5 hours under a nitrogen inert atmosphere. After calcination, 2122g of gray calcined powder was obtained. The gray color indicates that the powder surface is coated with carbon, mainly as a result of the high-temperature carbonization of the carbon source PAA adhesive.

[0048] 1500g of calcined powder was coated with a water-resistant polymer. First, 30g of the water-resistant polymer, polyvinyl chloride (PVC), was dissolved in 4500g of dispersant tetrahydrofuran and poured into a grinding and dispersing tank. Simultaneously, the calcined powder was added, and then grinding step 5 was performed at a speed of 3000 r / min for 3 hours. The resulting slurry was then spray-dried step 6 at an inlet temperature of 250°C and an outlet temperature of 80°C, yielding 1407g of spray-dried powder. This completed the material preparation. The proportion of the water-resistant polymer in the calcined powder was 2%.

[0049] Example 4: The preparation process is the same as in Example 3, except that the proportion of PAA adhesive is reduced to 1%.

[0050] Example 5: The preparation process is the same as in Example 3, except that the proportion of water-resistant polymer is reduced to 1% of the calcined powder.

[0051] Comparative Example 1: Following the method of Example 1, the same titanium and lithium sources were used for calcination in an air atmosphere to obtain white calcined lithium titanate powder.

[0052] Comparative Example 2: The carbon-coated lithium titanate prepared in Example 1 was used without water-resistant polymer surface treatment.

[0053] Comparative Example 3: The preparation process is the same as in Example 1, except that the water-resistant polymer is changed to polytetrafluoroethylene (dissolved in NMP).

[0054] Comparative Example 4: The preparation process is the same as in Example 1, except that the water-resistant polymer is changed to polyimide (dissolved in NMP).

[0055] Experimental example: The negative electrode slurry formulation is LTO:SP:CNT:PVDF = 94:2:1:3. After electrode coating and rolling, the water absorption characteristics of the electrode under high humidity (approximately 40%, while conventional lithium titanate electrodes generally require humidity levels below 20%) were investigated, comparing the water absorption of the lithium titanate electrode in the comparative examples and control examples. Specifically, the electrode was placed in an environment of approximately 40% humidity for 6 hours, and then the moisture content was tested.

[0056] To investigate the stability of the water-resistant polymer lithium titanate material, a full-charge battery fabrication was conducted. The positive electrode used NCM523 material, the separator was a 16μm conventional PE separator, and the electrolyte was commercially available lithium hexafluorophosphate electrolyte. A small pouch battery with a rated capacity of 2Ah, model 3090105, was fabricated. Gas generation during formation and gas generation during full-charge high-temperature storage were investigated to analyze the stability of the negative electrode interface during formation and full-charge high-temperature storage. The formation parameters were: 0.1C constant current charging for 60 min, followed by 0.2C constant current charging for 60 min, then 0.3C charging to 2.5V, and finally 0.2C discharging to 1.5V to complete formation. The full-charge high-temperature storage test method involved charging the battery to 2.8V at 0.2C, then storing it at 60°C for 7 days to investigate gas generation, followed by discharging at room temperature to 1.5V to investigate capacity retention.

[0057] The results are shown in Table 1 below; Table 1

[0058] As shown in Table 1, the LTO with water-resistant polymer coating exhibits significantly lower water absorption than the uncoated LTO. Specifically, the lithium titanate powder in Example 1 has a water absorption rate of 357 ppm. In Comparative Example 2, the carbon-coated lithium titanate electrode shows a significantly higher water absorption rate of 665 ppm, while the uncoated lithium titanate powder in Comparative Example 1 reaches a high of 1061 ppm. This indicates that coating with a water-resistant polymer significantly reduces the adsorption of environmental moisture on the lithium titanate surface. This demonstrates that polymer coating improves the surface stability of the lithium titanate electrode, primarily due to reduced side reactions with the electrolyte. Carbon coating of LTO also improves water absorption compared to uncoated LTO, indicating that carbon coating also reduces surface water absorption, but it is still less effective than coating with a water-resistant polymer.

[0059] Comparative Examples 3 and 4 selected two other water-resistant polymer materials for coating, and the results showed that they could improve the water absorption rate of lithium titanate electrodes. However, there was still a certain gap compared with the results of the water-resistant polymers used in the various embodiments of this application, among which the gap with Example 1 was the most obvious.

[0060] In terms of gas generation during formation, gas generation during full-charge high-temperature storage, and high-temperature stability, LTO with simultaneous carbon coating and water-resistant polymer surface treatment exhibits excellent characteristics. This indicates that the polymer-coated lithium titanate electrode has high interfacial stability, mainly due to the polymer coating acting similarly to an SEI film, preventing direct contact between lithium titanate and the electrolyte and reducing side reactions. Other types of polymers, such as polytetrafluoroethylene in Comparative Example 3 or polyimide in Comparative Example 4, also have good water absorption resistance, but due to the difficulty of lithium-ion diffusion and high impedance, side reactions can occur, resulting in poorer gas generation during formation and high-temperature storage stability. Therefore, to obtain good water resistance and electrochemical performance, it is necessary to simultaneously perform carbon coating pretreatment and select the appropriate water-resistant polymer and its proportion, considering the ionic and electronic conductivity after surface treatment.

[0061] 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 low water absorption lithium titanate characterized by, It includes lithium titanate and a water-resistant polymer, wherein the water-resistant polymer coats the lithium titanate, and the water-resistant polymer includes one or more of polycarbonate, polysulfone, polyurethane, polyvinyl butyral, polyvinyl chloride, and ABS resin.

2. The low water absorption lithium titanate according to claim 1, characterized in that, The mass of the water-resistant polymer accounts for 0.5-5% of the mass of the lithium titanate.

3. The low-water-absorption lithium titanate according to claim 1, characterized in that, The lithium titanate includes lithium titanate coated with carbon by forming an adhesive, wherein the adhesive includes one or more of sodium carboxymethyl cellulose, sodium alginate, polyacrylic acid, polyvinylpyrrolidone, and chitosan.

4. A method for preparing low-water-absorption lithium titanate as described in claim 1, characterized in that, include: S1. Lithium titanate is obtained by sintering lithium titanate precursor material, wherein the lithium titanate precursor material includes a titanium source and a lithium source; S2. The lithium titanate and the water-resistant polymer are evenly dispersed and fully contacted. After spray drying, low water absorption lithium titanate coated with water-resistant polymer is obtained.

5. The preparation method according to claim 4, characterized in that, The lithium titanate precursor material includes a titanium source, a lithium source, and a glue, wherein the glue includes one or more of sodium carboxymethyl cellulose, sodium alginate, polyacrylic acid, polyvinylpyrrolidone, and chitosan.

6. The preparation method according to claim 5, characterized in that, The mass of the adhesive accounts for 1.5-6% of the mass of the titanium source.

7. The preparation method according to claim 4 or 5, characterized in that, The titanium source includes one or more of titanium dioxide, titanium hydroxide, and metatitanic acid; the lithium source is one or more of lithium oxalate, lithium carbonate, lithium acetate, lithium hydroxide monohydrate, and lithium nitrate.

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 low water absorption lithium titanate, binder and conductive agent as described in any one of claims 1-3.

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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