Preparation method of negative active material, negative plate and battery
MXene@polyaniline composite materials were prepared by ball milling and hydrothermal treatment, which solved the problem of low specific capacitance of MXene anode materials and achieved high capacitance and stable battery performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- EVE POWER CO LTD
- Filing Date
- 2025-12-30
- Publication Date
- 2026-05-15
AI Technical Summary
The existing MXene anode material has low specific capacitance and poor stability, resulting in a low electrolyte ion insertion and extraction rate, which affects battery performance.
By ball milling a mixture of MXene and polyaniline, followed by hydrothermal reduction, a composite material MXene@polyaniline is formed. Polyaniline is loaded in the MXene interlayer and generates oxygen vacancies on the surface, which improves the electrochemical stability and capacitance of the material.
It significantly improved the capacitance and cycle stability of MXene@polyaniline composite material, achieved a fast charging capability of 554F g-1, and enhanced the reversible specific capacity and cycle performance of the battery.
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Abstract
Description
Technical Field
[0001] This application relates to the field of battery technology, specifically to a method for preparing a negative electrode active material, a negative electrode sheet, and a battery. Background Technology
[0002] MXene is a novel lithium-ion battery anode material, and its application as an energy storage material has reached a certain level. Generally, MXene is obtained by chemical liquid-phase etching of MAX materials, resulting in a stacked multi-layered structure. A common subsequent step is to use dimethyl sulfoxide (DMSO) as an intercalating agent to further ultrasonically exfoliate the MXene into a few-layer or single-layered sheet structure. However, the intercalation capacity of a single intercalating agent is limited, leading to low yield and the resulting single-layered structure being prone to re-stabilization, resulting in poor stability and reduced electrolyte ion insertion / extraction rates between MXene layers, thus causing a low specific capacitance. Summary of the Invention
[0003] This application provides a method for preparing a negative electrode active material, a negative electrode sheet, and a battery, aiming to solve the technical problem of low specific capacitance of MXene.
[0004] This application provides a method for preparing a negative electrode active material, including: A first mixture comprising MXene and polyaniline is ball-milled to load the polyaniline onto the MXene to obtain a composite material MXene@polyaniline; The MXene@polyaniline was subjected to hydrothermal reduction treatment to generate oxygen vacancies on the surface of the MXene, thereby obtaining a negative electrode active material.
[0005] In the preparation method of the negative electrode active material provided in this application embodiment, through ball milling, polyaniline can enter the interlayer of MXene, preventing the stacking of MXene nanosheets and improving the capacitance of the single material; the presence of polyaniline in the interlayer of MXene makes the molecular chains of polyaniline less prone to aggregation during charge and discharge, effectively preventing the volume expansion of the pseudocapacitive material (polyaniline), and improving the electrochemical stability of the MXene@polyaniline composite material; and the hydrothermal reduction treatment can generate oxygen vacancies on the MXene surface, forming an electron-rich structure. Oxygen vacancies can lower the electron transport energy barrier and improve surface reaction kinetics, while the electron-rich state can enhance the interfacial charge storage capacity, resulting in a significant increase in specific capacitance compared to untreated MXene, reaching 30 A g. -1 554 F g under the conditions -1 Its fast charging capability.
[0006] Optionally, in some embodiments of this application, the first mixture further includes a ball milling aid, which comprises a protic acid solution.
[0007] Protic acid, as a ball milling aid, can promote the composite of MXene and polyaniline, and improve the reversible specific capacity of the single material. In addition, the polyaniline doped with protic acid is positively charged in the protic acid solution, which can promote the adsorption of polyaniline on the negatively charged MXene (containing functional groups such as -OH and -F) interlayer or surface due to electrostatic force, further intercalation and increasing the interlayer spacing of MXene.
[0008] Optionally, in some embodiments of this application, the protic acid solution includes hydrochloric acid.
[0009] Optionally, in some embodiments of this application, the mass ratio of MXene to the protic acid solution is 1:(4~6).
[0010] Optionally, in some embodiments of this application, the concentration of the protic acid solution is 0.1 mol / L to 6 mol / L.
[0011] Optionally, in some embodiments of this application, urea is added during the hydrothermal reduction treatment of the MXene@polyaniline to intercalate the MXene.
[0012] During the hydrothermal reaction, urea (CO(NH2)2) readily decomposes under high temperature and pressure to generate ammonia, which further promotes the formation of oxygen vacancies on the MXene surface. Furthermore, during the hydrothermal reaction, urea molecules intercalate between the MXene layers, enabling reversible stretching and contraction of the interlayer spacing during charging and discharging, releasing an additional pseudo-capacitive effect and improving the material's cycle stability.
[0013] Optionally, in some embodiments of this application, the mass ratio of urea to MXene@polyaniline is 1:(3~4).
[0014] Optionally, in some embodiments of this application, the hydrothermal temperature of the hydrothermal reduction treatment is 80°C to 150°C.
[0015] Optionally, in some embodiments of this application, the hydrothermal reduction treatment time is 8h to 15h.
[0016] Optionally, in some embodiments of this application, the first mixture further includes milling media, which includes zirconia balls.
[0017] Optionally, in some embodiments of this application, the ball milling speed of the ball milling process is 250 rpm / min to 350 rpm / min.
[0018] Optionally, in some embodiments of this application, the ball milling time is 8h to 15h.
[0019] Optionally, in some embodiments of this application, the polyaniline in the MXene@polyaniline is loaded between the layers of the MXene.
[0020] Optionally, in some embodiments of this application, the mass ratio of MXene to polyaniline in the first mixture is (3~4):1.
[0021] Optionally, in some embodiments of this application, the MXene includes at least one of Ti2CTx, Ti3C2Tx, and Ti4C3Tx, where Tx represents a functional group, and the functional group includes at least one of -OH, -F, and =O.
[0022] Optionally, in some embodiments of this application, the MXene is a multi-layered structure.
[0023] Accordingly, this application also provides a negative electrode sheet, the negative electrode sheet comprising a negative electrode film layer, the negative electrode film layer comprising a negative electrode active material obtained by the preparation method of the negative electrode active material.
[0024] Optionally, in some embodiments of this application, the negative electrode film layer further includes a conductive agent and a binder.
[0025] Optionally, in some embodiments of this application, the negative electrode sheet further includes a negative electrode current collector, and the negative electrode film layer is disposed on the negative electrode current collector.
[0026] In addition, this application also provides a battery, the battery including the negative electrode. Detailed Implementation
[0027] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0028] This application provides a method for preparing a negative electrode active material, a negative electrode sheet, and a battery. These are described in detail below. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative and do not impose numerical requirements or establish an order. Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.
[0029] Some embodiments of this application provide a battery, and an electrical device includes the battery. A battery refers to a device that can convert chemical energy into electrical energy. The battery can have different forms, such as, but not limited to, a battery cell, a battery module, and a battery pack. Typically, battery modules and battery packs each independently include multiple battery cells connected in series or parallel.
[0030] Some embodiments of this application provide a single battery cell. A single battery cell (also called a battery cell) is the basic unit for converting chemical energy into electrical energy. Optionally, the single battery cell is a secondary battery, such as a lithium-ion battery, thus enabling the interconversion of chemical energy and electrical energy.
[0031] In some embodiments of this application, the battery cell includes a housing with a receiving cavity and an electrode assembly disposed within the receiving cavity, the housing serving to protect the electrode assembly. In a common embodiment, the housing includes a shell body and a cover, the cover being disposed on the shell body, the shell body and the cover together defining the receiving cavity. The housing can be made of a metal material with good mechanical strength. As an example, the housing can be a steel shell or an aluminum shell. In another embodiment, a flexible aluminum-plastic film can be used as the housing, resulting in a pouch battery. Pouch batteries have advantages such as lightweight, high energy density, good safety, and flexible shape design.
[0032] To facilitate the transmission of circuits and data between the electrode assembly inside the cavity and the external circuitry outside the cavity, terminals are provided on the cover, which are connected to the electrode assembly. The external circuitry can supply power to the electrode assembly through the terminals, thus charging the individual battery cells; conversely, the electrode assembly can also supply power to the external circuitry through the terminals, thus discharging the individual battery cells.
[0033] In some embodiments of this application, the electrode assembly includes a positive electrode and a negative electrode disposed opposite to each other. The electrode assembly can be configured as a wound structure or a stacked structure.
[0034] In some embodiments of this application, the electrode assembly further includes a separator disposed between the positive and negative electrode plates to prevent short circuits caused by contact between the positive and negative electrode plates. The separator may be selected from one or more of polyolefin separators, non-woven fabric separators, ceramic-coated separators, and composite separators. As an example, a polyolefin separator includes at least one of polyethylene (PE) membranes and polypropylene (PP) membranes. The separator may be a dry-process separator or a wet-process separator, and this is not limited thereto.
[0035] In some embodiments of this application, the battery cell further includes an electrolyte used to wet the electrode assembly. The electrolyte provides ion channels during the charging and discharging process of the battery cell, enabling charge transfer between the positive and negative electrodes, thereby completing energy storage and release. The electrolyte mainly includes a non-aqueous organic solvent and an electrolyte salt. Taking a lithium-ion battery as an example, the electrolyte salt includes lithium salts, which may include at least one of lithium hexafluorophosphate (LiPF6), lithium perchlorate, lithium bis(oxalato)borate (LiBOB), lithium difluorooxalato)borate (LiODFB), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium bis(fluorosulfonyl)imide (LiFSI); the non-aqueous organic solvent includes at least one of carbonate solvents, carboxylic acid ester solvents, and ether solvents. Optionally, the electrolyte also includes functional additives. Functional additives are generally diverse and have different functions. As examples, functional additives include membrane additives, overcharge protection additives, flame retardant additives, high and low temperature additives, conductive additives, and additives for controlling water and HF content, etc. The film additive includes at least one of vinylene carbonate (VC) and fluoroethylene carbonate (FEC). The flame retardant additive includes at least one of organophosphorus compounds, organofluorine compounds, and haloalkyl phosphates.
[0036] In some embodiments of this application, the electrode assembly further includes a solid electrolyte membrane disposed between the positive and negative electrode plates. The solid electrolyte membrane can also prevent the positive and negative electrode plates from conducting. Optionally, the solid electrolyte membrane includes at least one of oxide solid electrolyte, sulfide solid electrolyte, and polymer solid electrolyte. If the solid electrolyte membrane can completely replace the electrolyte and separator in a single battery cell, then the battery cell is an all-solid-state battery. Of course, in other embodiments, the battery cell can also be a semi-solid-state battery or a liquid battery.
[0037] In some embodiments of this application, the electrode assembly further includes tabs. Specifically, the tabs include a positive tab and a negative tab, wherein the positive tab is connected to a positive electrode plate, for example, by welding, and the negative tab is connected to a negative electrode plate, for example, by welding. A terminal post is connected to the tabs of the electrode assembly, for example, by welding. The terminal post also includes a positive terminal post and a negative terminal post, wherein the positive terminal post is connected to the positive tab, and the negative terminal post is connected to the negative tab.
[0038] In some embodiments of this application, the positive electrode sheet includes a positive electrode film layer comprising a positive electrode active material. Optionally, the positive electrode active material includes at least one selected from lithium iron phosphate, lithium manganese iron phosphate, lithium nickel manganese oxide, lithium cobalt oxide, lithium-rich manganese-based oxide, and lithium manganese oxide. Further, the positive electrode film layer also includes a conductive agent and a binder. In the positive electrode sheet, the conductive agent includes at least one selected from carbon black, graphite, carbon nanotubes (CNTs), graphene, and carbon fibers, and the binder includes polyvinylidene fluoride (PVDF). In some embodiments, the positive electrode sheet is a self-supporting structure, comprising only the positive electrode film layer without a positive electrode current collector. In other embodiments, the positive electrode sheet also includes a positive electrode current collector, with the positive electrode film layer disposed on the positive electrode current collector. As an example, the positive electrode current collector includes aluminum foil.
[0039] Some embodiments of this application also provide a negative electrode sheet, which includes a negative electrode film layer containing a negative electrode active material.
[0040] In some embodiments of this application, the negative electrode film layer further includes a conductive agent and a binder. In the negative electrode sheet, the conductive agent includes at least one selected from acetylene black, Ketjen black, carbon nanotubes (CNTs), graphene, and vapor-grown carbon fiber (VGCF), and the binder includes at least one selected from carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and polyacrylic acid (PAA). In some embodiments, the negative electrode sheet is a self-supporting structure, comprising only the negative electrode film layer without a negative electrode current collector. In other embodiments, the negative electrode sheet further includes a negative electrode current collector, with the negative electrode film layer disposed on the negative electrode current collector. As an example, the negative electrode current collector includes copper foil.
[0041] Some embodiments of this application also provide a method for preparing a negative electrode active material, including: S1. A first mixture comprising MXene and polyaniline is ball-milled to load polyaniline onto MXene to obtain a composite material MXene@polyaniline; S2. Perform hydrothermal reduction treatment on MXene@polyaniline to generate oxygen vacancies on the surface of MXene, thereby obtaining the negative electrode active material.
[0042] MXenes are a class of two-dimensional inorganic compounds. The general formula for MXenes is M. n+1 X n Tx, where M is selected from transition metals such as Ti, V, Cr, Mo, etc.; X is carbon or nitrogen; and Tx is a surface functional group such as OH, F, and O. MXene is obtained by deriving MXene from M... n+1 AX n MXenes are prepared by selectively etching the A layer in the MAX phase, where M is a transition metal and A is mainly composed of group IIIA or IVA elements (i.e., group 13 or 14). A common strategy for preparing MXenes is top-down etching starting from the MAX phase. Typically, MA bonds are considered metallic, while MX bonds exhibit multiple ionic characteristics, being both metallic and covalent. Therefore, MA bonds can be selectively etched instead of MX bonds.
[0043] As an example, MXene includes at least one of Ti2CTx, Ti3C2Tx, and Ti4C3Tx, where Tx represents a functional group, including at least one of -OH, -F, and =O. Taking Ti3C2Tx as an example, Ti3C2Tx can be obtained by selectively etching the Al layer in Ti3AlC2.
[0044] MXenes can exist in both multilayer and single-layer structures. During preparation, MXenes typically exist in a multilayer form; for example, Ti3C2Tx has an accordion-like multilayer structure. This multilayer structure is connected by van der Waals forces, resulting in a large interlayer spacing and a high specific surface area. However, through further processing, such as ultrasonic exfoliation or ball milling, multilayer MXenes can be transformed into single-layer or few-layer nanosheets. Multilayer MXene structures include multiple stacked MXene nanosheets.
[0045] MXenes typically exhibit excellent electrical conductivity. For example, Ti3C2Tx nanosheets possess conductivity as high as 4600 Scm. -1 It has excellent electrical conductivity.
[0046] Polyaniline (PANI) is a conductive polymer material. Polyaniline is loaded onto MXene through ball milling. In the MXene@polyaniline composite, polyaniline is loaded on the surface of MXene and / or between the layers of MXene; specifically, when MXene is a monolayer structure, polyaniline is loaded on the surface of MXene; when MXene is a multilayer structure, polyaniline can be loaded on the surface of MXene and intercalated between the layers of MXene. When polyaniline is intercalated between the layers of MXene, it can increase the interlayer spacing of MXene. The interlayer spacing of MXene refers to the distance between two adjacent MXene nanosheets.
[0047] MXene@polyaniline is reduced via a hydrothermal method. During this process, some oxygen atoms on the MXene surface are desorbed or reduced under high temperature and pressure, creating oxygen vacancies. Optionally, hydrogen (H2) or ammonia (NH3) gases are introduced into the hydrothermal reactor during the process. The hydrogen atoms in these gases tend to replace oxygen atoms on the MXene surface, causing them to detach from the crystal lattice and form oxygen vacancies. Taking Ti3C2Tx as an example, the generation of numerous oxygen vacancies on the Ti3C2Tx surface can activate the surface C-Ti-O functional groups. Using this composite material in the negative electrode of a lithium-ion battery can improve the reversible specific capacity of the single material and enhance its cycle stability.
[0048] In summary, in the preparation method of the negative electrode active material provided in this application embodiment, through ball milling, polyaniline can enter the interlayer of MXene, preventing the stacking of MXene nanosheets and improving the capacitance of the single material; the presence of polyaniline in the interlayer of MXene makes it difficult for the molecular chains of polyaniline to aggregate during charging and discharging, effectively preventing the volume expansion of the pseudocapacitive material (polyaniline) and improving the electrochemical stability of the MXene@polyaniline composite material; and the hydrothermal reduction treatment can generate oxygen vacancies on the MXene surface, forming an electron-rich structure. Oxygen vacancies can lower the electron transport energy barrier and improve surface reaction kinetics, while the electron-rich state can enhance the interfacial charge storage capacity, resulting in a significantly higher specific capacitance compared to untreated MXene, and reaching 30 Ag. -1 554 F g under the conditions -1 Its fast charging capability.
[0049] The method for preparing the negative electrode active material provided in this application involves preparing the composite material MXene@polyaniline by ball milling and mixing, and then treating MXene@polyaniline by hydrothermal method to improve the reversible specific capacity of the composite material (i.e., the negative electrode active material) and enhance the cycle stability of the negative electrode active material.
[0050] In some embodiments of this application, the first mixture further includes a ball milling aid, which comprises a protic acid solution.
[0051] A protic acid is a substance that can donate a proton (H). + Protonic acids are substances that are acidic or non-protic. Common protonic acids include sulfuric acid and hydrochloric acid. As an example, a protonic acid solution includes hydrochloric acid. The solvent in a protonic acid solution is usually water. Optionally, the concentration of the protonic acid solution is 0.1 mol / L to 6 mol / L. As an example, the protonic acid solution is hydrochloric acid, and the concentration of hydrochloric acid is 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, or 6 mol / L.
[0052] Understandably, the first mixture also includes a protic acid solution as a ball milling aid, which can wet MXene and polyaniline, thus enabling wet ball milling. Optionally, the amount of protic acid solution used may cover MXene and polyaniline.
[0053] Protic acid, as a ball milling aid, can promote the composite of MXene and polyaniline, and improve the reversible specific capacity of the single material. In addition, the polyaniline doped with protic acid is positively charged in the protic acid solution, which can promote the adsorption of polyaniline on the negatively charged MXene (containing functional groups such as -OH and -F) interlayer or surface due to electrostatic force, further intercalation and increasing the interlayer spacing of MXene.
[0054] In some embodiments of this application, the mass ratio of MXene to protic acid solution is 1:(4~6). By controlling the amount of protic acid solution to be greater than that of MXene, MXene is better wetted by the protic acid solution, thereby promoting the interlayer intercalation of protic acid-doped polyaniline in MXene. As examples, the mass ratio of MXene to protic acid solution is 1:4.0, 1:4.5, 1:5.0, 1:5.5, or 1:6.0.
[0055] In some embodiments of this application, the first mixture further includes milling media, which comprises zirconia balls. The average particle size of the zirconia balls is 4 mm to 6 mm, for example, 4 mm, 5 mm, or 6 mm.
[0056] In some embodiments of this application, the mass ratio of MXene to polyaniline in the first mixture is (3~4):1. As examples, the mass ratio of MXene to polyaniline is 3.0, 3.2, 3.4, 3.6, 3.8, or 4.0. A mass ratio of MXene to polyaniline greater than 4 or less than 3 will affect the intercalation effect of MXene.
[0057] In some embodiments of this application, the ball milling speed is 250 rpm / min to 350 rpm / min. As examples, the ball milling speed is 250 rpm / min, 270 rpm / min, 290 rpm / min, 310 rpm / min, 330 rpm / min, or 350 rpm / min.
[0058] In some embodiments of this application, the ball milling time is 8h to 15h. As examples, the ball milling time is 8h, 9h, 10h, 11h, 12h, 13h, 14h or 15h.
[0059] In some embodiments of this application, urea is added during the hydrothermal reduction treatment of MXene@polyaniline to intercalate MXene.
[0060] During the hydrothermal reaction, urea (CO(NH2)2) readily decomposes under high temperature and pressure to generate ammonia, which further promotes the formation of oxygen vacancies on the MXene surface. Furthermore, during the hydrothermal reaction, urea molecules intercalate between the MXene layers, enabling reversible stretching and contraction of the interlayer spacing during charging and discharging, releasing an additional pseudo-capacitive effect and improving the material's cycle stability.
[0061] In some embodiments of this application, the mass ratio of urea to the composite material MXene@polyaniline is 1:(3~4). As examples, the mass ratio of urea to MXene@polyaniline is 1:3.0, 1:3.2, 1:3.4, 1:3.6, 1:3.8, or 1:4.0. A mass ratio of MXene@polyaniline to urea greater than 4 or less than 3 will affect the number of oxygen vacancies formed on the MXene surface and the effectiveness of MXene intercalation.
[0062] In some embodiments of this application, the hydrothermal temperature for the hydrothermal reduction treatment is 80°C to 150°C. As examples, the hydrothermal temperature is 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C.
[0063] In some embodiments of this application, the hydrothermal reduction treatment time is 8h to 15h. As examples, the hydrothermal time is 8h, 9h, 10h, 11h, 12h, 13h, 14h or 15h.
[0064] The following description is based on specific embodiments.
[0065] Preparation Example 1 This preparation example provides a negative electrode active material, the preparation method of which includes: S01, MXene preparation: The raw material MAX was etched with hydrofluoric acid solution. MAX powder was weighed according to the ratio of m(MAX):m(hydrofluoric acid) = 1:10 and slowly added to a 40wt% hydrofluoric acid solution until it was completely submerged. The mixture was stirred at room temperature for 24 hours. After the reaction was completed, the supernatant was washed by centrifugation with deionized water until the pH of the supernatant was neutral. The successfully etched MXene was obtained by freeze-drying and denoted as M1.
[0066] S02, Preparation of polyaniline: At room temperature, a certain amount of aniline was added to a 1 mol / L hydrochloric acid solution and stirred in an ice bath (0±2℃) until a uniform dispersion (dispersion concentration of 15 mg / mL) was formed; then, an equal volume of 1 mol / L hydrochloric acid solution containing ammonium persulfate was added at a uniform rate, with a mass ratio of m(ammonium persulfate):m(aniline) = 2.94:1. Polyaniline was prepared by low-temperature stirring and polymerization in an ice bath at 0±2℃ for 4 h. The precipitate was collected by vacuum filtration and dried in a vacuum oven at 50℃ for 8 h. The treated polyaniline was recorded as sample M2.
[0067] S03. Ball milling and mixing: Weigh MXene and polyaniline samples according to m(M1):m(M2)=3.5:1 and pour them into a ball mill jar. Add hydrochloric acid as a ball milling aid and zirconia balls (5mm in diameter) as the ball milling medium. The mass ratio of MXene to hydrochloric acid is 1:5 and the concentration of hydrochloric acid is 1mol / L. Wet ball mill at 300rpm / min for 12h. After filtration, washing and drying with deionized water, the composite material MXene@polyaniline is obtained and denoted as M3.
[0068] S04. Hydrothermal reduction treatment: Weigh the MXene@polyaniline composite sample and urea according to m(M3):m(urea)=3.5:1, put them into a hydrothermal reactor, use ethanol as solvent, the mass ratio of MXene@polyaniline composite to ethanol is 1:10, react at 120°C for 12 hours, after filtration, washing and drying with deionized water, MXene@polyaniline material with a large number of oxygen vacancies on the surface (i.e. negative electrode active material) is obtained, which is denoted as M4.
[0069] Preparation Example 2 This preparation example provides a negative electrode active material. The preparation method of this negative electrode active material can be found in Preparation Example 1, except that in step S03, hydrochloric acid is replaced with sulfuric acid.
[0070] Preparation Example 3 This preparation example provides a negative electrode active material. The preparation method of this negative electrode active material is described in Preparation Example 1, except that hydrochloric acid is omitted in step S03.
[0071] Preparation Example 4 This preparation example provides a negative electrode active material. The preparation method of this negative electrode active material is described in Preparation Example 1, except that urea is omitted in step S04.
[0072] Example 1 This embodiment provides a battery, the preparation process of which is as follows: Sample M4 provided in Preparation Example 1 is mixed with Super P and PVDF in a mass ratio of 8:1:1 with NMP solvent to prepare an electrode slurry with a solid content of 50wt%. The slurry is then uniformly coated on copper foil and placed in a vacuum drying oven to dry at 100°C for 12 hours. The electrode sheet with a diameter of 12 mm is prepared using a slicing machine and then assembled into a lithium half-cell in a vacuum glove box filled with argon gas.
[0073] Example 2 This embodiment provides a battery. The preparation process of this battery can be found in Example 1, except that sample M4 provided in Preparation Example 2 is used instead of sample M4 provided in Preparation Example 1.
[0074] Example 3 This embodiment provides a battery. The preparation process of this battery is described in Example 1, except that sample M4 provided in Preparation Example 3 is used instead of sample M4 provided in Preparation Example 1.
[0075] Example 4 This embodiment provides a battery. The preparation process of this battery can be found in Example 1, except that sample M4 provided in Preparation Example 4 is used instead of sample M4 provided in Preparation Example 1.
[0076] Comparative Example 1 This comparative example provides a battery, the preparation process of which can be found in Example 1, except that sample M1 provided in Preparation Example 1 is used instead of sample M4 provided in Preparation Example 1.
[0077] Comparative Example 2 This comparative example provides a battery, the preparation process of which can be found in Example 1, except that sample M3 provided in Preparation Example 1 is used instead of sample M4 provided in Preparation Example 1.
[0078] Performance testing: The lithium half-cells provided in each embodiment and comparative example were placed in an electrochemical workstation and subjected to a 0.1C rate charge-discharge cycle test. The test results are shown in Table 1.
[0079] Table 1
[0080] Results analysis: Compared with Comparative Example 1, Comparative Example 2 showed an increase of 41.5 mAh / g in initial discharge specific capacity and a 2.8% increase in capacity retention. Compared with Comparative Example 2, Example 1 showed an increase of 66 mAh / g in initial discharge specific capacity and an 8.5% increase in capacity retention. This indicates that loading polyaniline onto MXene to obtain MXene@polyaniline allows polyaniline to enter the MXene interlayer, preventing the stacking of MXene nanosheets and significantly improving the battery's specific capacity. Furthermore, hydrothermal reduction treatment of MXene@polyaniline generates oxygen vacancies on the MXene surface, which not only significantly improves the battery's specific capacity but also significantly improves its cycle performance.
[0081] Compared with Example 3, Example 1 showed a decrease in initial discharge specific capacity of 26.2 mAh / g and a decrease in capacity retention of 5.7%; Example 2 showed a decrease in initial discharge specific capacity of 31.6 mAh / g and a decrease in capacity retention of 6.7%. This indicates that protic acids, especially protic acid salts, as ball milling aids can promote the composite of MXene and polyaniline, thereby improving the reversible specific capacity of the material. In addition, the protic acid-doped polyaniline is positively charged in solution and adsorbs onto the negatively charged MXene interlayers and surface due to electrostatic forces, further intercalating and increasing the MXene interlayer spacing, thus improving the cycle performance of the battery.
[0082] Compared with Example 4, Example 1 showed that the initial discharge specific capacity of the battery decreased by 46.4 mAh / g and the capacity retention rate decreased by 8.3%. This indicates that the intercalation of urea molecules can enable MXene to achieve reversible stretching and contraction of interlayer spacing during charge and discharge, release additional pseudo-capacitance effect, and improve the cycle stability of the material.
[0083] The preparation method of the negative electrode active material, the negative electrode sheet and the battery provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principle and implementation of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of this application. Therefore, the content of this specification should not be construed as a limitation of this application.
Claims
1. A method for preparing a negative electrode active material, characterized in that, include: A first mixture comprising MXene and polyaniline is ball-milled to load the polyaniline onto the MXene to obtain a composite material MXene@polyaniline; The MXene@polyaniline was subjected to hydrothermal reduction treatment to generate oxygen vacancies on the surface of the MXene, thereby obtaining a negative electrode active material.
2. The method for preparing the negative electrode active material according to claim 1, characterized in that, The first mixture also includes a ball milling aid, which comprises a protic acid solution.
3. The method for preparing the negative electrode active material according to claim 2, characterized in that, The protic acid solution includes hydrochloric acid; and / or, The mass ratio of MXene to the protic acid solution is 1:(4~6); and / or, The concentration of the protic acid solution is 0.1 mol / L to 6 mol / L.
4. The method for preparing the negative electrode active material according to any one of claims 1 to 3, characterized in that, Urea is added during the hydrothermal reduction treatment of MXene@polyaniline, and the urea is used to intercalate the MXene.
5. The method for preparing the negative electrode active material according to claim 4, characterized in that, The mass ratio of urea to MXene@polyaniline is 1:(3~4); and / or, The hydrothermal reduction treatment is performed at a temperature of 80℃~150℃; and / or, The hydrothermal reduction treatment takes 8 to 15 hours.
6. The method for preparing the negative electrode active material according to any one of claims 1 to 5, characterized in that, The first mixture further includes milling media, said milling media comprising zirconia balls; and / or, The ball milling speed for the ball milling process is 250 rpm / min to 350 rpm / min; and / or, The ball milling time for the ball milling process is 8h to 15h.
7. The method for preparing the negative electrode active material according to any one of claims 1 to 5, characterized in that, In the MXene@polyaniline, the polyaniline is loaded between the layers of the MXene; and / or, In the first mixture, the mass ratio of MXene to polyaniline is (3~4):1; and / or, The MXene comprises at least one of Ti2CTx, Ti3C2Tx, and Ti4C3Tx, where Tx represents a functional group, and the functional group comprises at least one of -OH, -F, and =O; and / or, The MXene has a multi-layered structure.
8. A negative electrode sheet, characterized in that, It includes a negative electrode film layer, wherein the negative electrode film layer comprises a negative electrode active material prepared by the method for preparing a negative electrode active material as described in any one of claims 1 to 7.
9. The negative electrode sheet according to claim 8, characterized in that, The negative electrode film layer further includes a conductive agent and a binder; and / or, The negative electrode sheet also includes a negative electrode current collector, and the negative electrode film layer is disposed on the negative electrode current collector.
10. A battery, characterized in that, Includes the negative electrode sheet as described in claim 8 or 9.