Negative electrode and method for manufacturing the same, and battery

Abstract

This invention discloses a negative electrode, its preparation method, and a battery. The electrode comprises a silicon-oxygen material, a first material, and a binder. The first material includes lithium-intercalated MXene and an elastic polymer electrolyte coating layer covering the surface of the lithium-intercalated MXene. These are bonded together with the binder around the silicon-oxygen material to form a three-dimensional elastic network with ionic conductivity. This network, together with the rigid lithium-intercalated MXene particles dispersed within it, effectively confines and buffers the significant volume expansion of the silicon-oxygen material during cycling, maintaining the integrity and stability of the electrode structure. Simultaneously, the elastic polymer electrolyte itself acts as an ion conductor, providing an additional pathway for the storage and transport of lithium ions within the lithium-intercalated MXene. Furthermore, the lithium-intercalated MXene can also serve as a lithium replenishment material, effectively improving the battery's initial coulombic efficiency.

Description

Technical Field

[0001] This invention relates to the field of lithium battery anode material technology, and in particular to an anode, its preparation method, and a battery. Background Technology

[0002] As the carrier for lithium-ion insertion and extraction, the negative electrode active material directly affects the battery's energy density, initial coulombic efficiency, cycle stability, and safety. Existing negative electrode active materials are mainly graphite materials, which have long cycle life but low theoretical specific capacity, making it impossible to further improve capacity performance. Pure silicon materials have high theoretical capacity, but the volume expansion problem is serious, and commercial use is not yet possible. The specific capacity of silicon-oxygen materials is about 1500~2000mAh / g, and the volume expansion rate is lower than that of pure silicon, making it easier to achieve mass production. However, with the continuous improvement of driving range, energy density, and cycle performance in the energy storage field, more stringent requirements have been placed on the material system of lithium-ion batteries. The volume expansion problem of silicon-oxygen materials still needs to be solved. In addition, silicon-oxygen materials also face the problem of low initial coulombic efficiency (usually 65%-80%) - during the first charge and discharge, silicon dioxide and lithium undergo an irreversible reaction to generate Li2O and Li2SiO3, consuming a large number of lithium ions and causing capacity loss. Summary of the Invention

[0003] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a negative electrode and its preparation method to address the problems of volume expansion, low initial charge-discharge efficiency, and poor capacity and cycle performance of current lithium-ion batteries using silicon-oxygen negative electrode active materials.

[0004] In a first aspect, the present invention provides a negative electrode comprising a silicon oxide material, a first material and a binder, wherein the first material comprises a lithium-intercalated MXene and an elastic polymer electrolyte coating layer covering the surface of the lithium-intercalated MXene.

[0005] In some embodiments, the ratio of the sum of the masses of the first material and the silicon oxide material to the mass of the adhesive is 1:(0.05). 0.1).

[0006] In some embodiments, the mass ratio of the first material to the silicon-oxygen material is (0.1). 0.5): 1.

[0007] In some embodiments, the mass ratio of the lithium-intercalated MXene to the elastic polymer electrolyte coating is 1:(0.05) 0.2).

[0008] In some embodiments, the lithium-intercalated MXene includes at least one of Li3Ti3C2Tx, Li2Ti2CTx, and Li2V2CTx, wherein T is an electronegative surface functional group, and x is the average total number of surface functional groups on each repeating structural unit in the MXene material.

[0009] In some embodiments, the thickness of the elastic polymer electrolyte coating layer is 10 nm. 70nm.

[0010] In some embodiments, the elastic polymer electrolyte includes at least one of polyethylene oxide, polyethylene oxide-polypropylene oxide, poly(p-phenylenebenzodioxazole)-polyethylene oxide, polyethylene oxide-polypropylene carbonate, polydimethylsiloxane-polyethylene glycol, polyvinylidene fluoride-hexafluoropropylene, and polyacrylic acid-polyethylene glycol.

[0011] In some embodiments, the adhesive includes at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, sodium alginate, waterborne polyurethane, polyacrylate, and chitosan-based adhesive.

[0012] In a second aspect, the present invention provides a method for preparing a negative electrode, for preparing a negative electrode as described in any one of the first aspects, the method comprising the following steps:

[0013] Preparation of lithium-intercalated MXene;

[0014] A first material is obtained by coating the lithium intercalation layer with an elastic polymer electrolyte, MXene.

[0015] The first material and the silicon-oxygen material are mixed and a binder is added to obtain a negative electrode slurry;

[0016] The negative electrode is obtained by coating the negative electrode slurry onto the negative electrode current collector and drying it.

[0017] Thirdly, the present invention provides a battery including a positive electrode and a negative electrode as described in any one of the first aspects.

[0018] The above-described embodiments of the present invention have at least one or more of the following beneficial effects:

[0019] This invention provides a negative electrode, its preparation method, and a battery. The negative electrode comprises a silicon-oxygen material, a first material, and a binder. The first material includes lithium-intercalated MXene and an elastic polymer electrolyte coating layer on its surface. A three-dimensional elastic network with ionic conductivity is constructed around the silicon-oxygen material by the binder. This network, together with the rigid lithium-intercalated MXene particles dispersed within it, effectively confines and buffers the significant volume expansion of the silicon-oxygen material during cycling, maintaining the integrity and stability of the electrode structure. Simultaneously, the elastic polymer electrolyte itself acts as an ion conductor, providing an additional pathway for the storage and transport of lithium ions within the lithium-intercalated MXene.

[0020] Meanwhile, lithium-intercalated MXene can also be used as a lithium replenishment material, effectively improving the first coulombic efficiency of the battery.

[0021] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0022] Some embodiments of the present invention are described below. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0023] As described in the background section, silicon-oxygen anode materials have a high theoretical specific capacity and can be used as ideal materials to improve the energy density of lithium-ion batteries. However, they suffer from problems such as low initial coulombic efficiency and poor cycle life.

[0024] To address the aforementioned issues, this invention creatively proposes a negative electrode, its preparation method, and a battery. The negative electrode uses a binder to bond a silicon oxide material and a first material. The first material is an elastic polymer electrolyte coating lithium-intercalated MXene. The first material forms a three-dimensional elastic ion-conducting network around the silicon oxide material, with rigid lithium-intercalated MXene particles dispersed within it. The two work together to effectively confine and buffer the massive volume expansion of the silicon oxide material during cycling, maintaining the integrity and stability of the electrode structure. Simultaneously, the lithium-intercalated MXene can serve as a lithium replenishment material, and the elastic polymer electrolyte itself acts as an ion conductor, providing an additional pathway for the storage and transport of lithium ions within the lithium-intercalated MXene, achieving effective lithium replenishment for the battery and thus effectively improving the battery's initial coulombic efficiency.

[0025] The present invention will be specifically described below through specific embodiments.

[0026] Specifically, embodiments of the present invention provide a negative electrode, comprising a silicon oxide material, a first material and a binder, wherein the first material comprises a lithium-intercalated MXene and an elastic polymer electrolyte coating layer covering the surface of the lithium-intercalated MXene.

[0027] It should be noted that in this application, "lithium-intercalated MXene" refers to the lithium ion intercalation into the interlayer of MXene to form a lithium ion-MXene complex.

[0028] The term "MXene" in this application refers to a class of two-dimensional transition metal carbides, nitrides, or carbonitrides, which consist of several atomic layers and contain functional groups such as -OH and -O on their surface. They exhibit metallic conductivity and can be prepared by etching the precursor MAX phase with hydrofluoric acid to form a multilayer or thin-layer structure. Based on the M element (transition metal), MXenes are classified into titanium-based MXenes, other single transition metal MXenes, ordered dual transition metal MXenes, and solid solution / disordered multi-transition metal MXenes. For example: titanium-based MXenes include, but are not limited to, Ti3C2Tx, Ti2CTx, Ti4N3Tx, etc.; other single transition metals include, but are not limited to, molybdenum-based MXenes (e.g., Mo2CTx), vanadium-based MXenes (e.g., V2CTx), zirconium-based MXenes (e.g., Zr3C2Tx), chromium-based MXenes (e.g., Cr2CTx), tantalum-based MXenes (e.g., Ta4C3Tx), niobium-based MXenes (e.g., Nb2CTx, Nb4C3Tx), etc.; ordered dual transition metal MXenes include, but are not limited to, Mo2TiC2Tx, Mo2Ti2C3Tx, Cr2TiC2Tx, etc.; solid solution / disordered multi-transition metal MXenes include, but are not limited to, (Ti,V)3C2Tx, (Mo,V)4C3Tx, (Cr,V)3C2Tx, etc. Of course, MXenes can also be classified according to the element X into carbide MXenes, nitride MXenes, and carbon-nitride oxide MXenes, and can also be classified according to the number of layers (n value). The general chemical formula for MXenes is written as M. n+1 X n T x T x Represents surface functional groups.

[0029] By embedding lithium ions into the interlayer of MXene, the interlayer spacing of MXene material can be effectively increased, providing a more efficient transport channel for lithium ions. Moreover, the layered structure of lithium-intercalated MXene can store lithium, prevent excessive deposition of metallic lithium, and thus inhibit the growth of lithium dendrites.

[0030] Meanwhile, since the lithium-intercalated MXene has a higher delithiation potential than silicon-oxygen materials, it will preferentially release lithium and can be used as a lithium replenishment material to effectively improve the initial coulombic efficiency of the battery. After the lithium replenishment is completed, the residue still has good conductivity and can be used as a conductive agent and buffer framework to improve the poor conductivity and easy expansion of silicon-oxygen anodes.

[0031] The surface of lithium-intercalated MXene has functional groups such as -OH and -O, which interact with polar groups in the elastic polymer solid electrolyte, further enhancing the structural stability of the first material.

[0032] In some embodiments, the lithium-intercalated MXene includes at least one of Li3Ti3C2Tx, Li2Ti2CTx, and Li2V2CTx. It has good stability, a high effective lithium supplementation capacity, and easier lithium ion extraction, effectively improving the lithium supplementation efficiency. Here, T is a surface functional group with electronegativity, which is a stable functional group formed by passivating the dangling bonds on the two-dimensional carbon / nitride surface after MXene is etched and lithium-intercalated. Common Ts include: -OH, -O, -F, and in some cases, -Cl is also present in small amounts. x is the average total number of surface functional groups on each repeating structural unit in the MXene material. Since the surface etching and lithium intercalation of MXene are heterogeneous reactions, the functional group distribution on the material surface is not absolutely uniform (some sites are grafted with -OH, some are grafted with -O / -F), and it cannot be represented by an integer. Therefore, x is usually a decimal between 0 < x < 4. In the lithium-intercalated MXene, the value of x will be adapted to the lithium intercalation ratio.

[0033] In some preferred embodiments, the lithium-intercalated MXene is Li3Ti3C2Tx. Li3Ti3C2Tx has good stability and conductivity, and the theoretical lithium supplementation capacity can reach about 480 mAh / g, effectively providing the lithium supplementation efficiency of the battery and improving the initial efficiency.

[0034] Moreover, after lithium intercalation, the interlayer spacing expands to more than 1.1 nm, providing a more efficient transmission channel for lithium ions. The larger the interlayer spacing, the smaller the spatial hindrance during the migration of lithium ions between layers, and the faster the migration rate, which can improve the ionic conduction efficiency of the electrode; the gaps in the layered structure are not only the paths for lithium ion transmission but also the sites for lithium ion storage. At the same time, with the weak interaction of hydrogen bond / electrostatic adsorption between -OH, -O and other functional groups on the surface of lithium-intercalated MXene and lithium ions, the effect of lithium supplementation and inhibition of lithium dendrite growth is achieved.

[0035] The chemical formula of the silicon-oxygen material is , where , is a metastable composite of silicon and silicon suboxide, and nanosilicon grains are dispersed in the amorphous matrix. Through the active silicon + buffer matrix structure, a significant improvement in energy density is achieved at an acceptable cost and process complexity.

[0036] In some embodiments, the ratio of the sum of the masses of the first material and the silicon-oxygen material to the mass of the binder is 1:(0.05 0.1), including but not limited to 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.1) or any point value within the above ratio range.

[0037] In some embodiments, the mass ratio of lithium-intercalated MXene to the elastic polymer electrolyte coating is 1:(0.05). 0.2), including but not limited to 1:0.05, 1:0.07, 1:0.1, 1:0.13, 1:0.15, 1:0.17, 1:0.2, or any ratio within the above mass ratio range.

[0038] In some embodiments, the mass ratio of the first material to the silicon-oxygen material is (0.1...). 0.5): 1. Optionally, the mass ratio of the first material to the silicon-oxygen material can be 0.1:1, 0.13:1, 0.2:1, 0.25:1, 0.3:1, 0.37:1, 0.4:1, 0.46:1, 0.5:1, or any ratio within the above mass ratio range.

[0039] In some embodiments, the thickness of the elastic polymer electrolyte coating layer is 10 nm. 70nm, including but not limited to 10nm, 12nm, 20nm, 23nm, 30nm, 34nm, 40nm, 45nm, 50nm, 57nm, 60nm, 68nm, 70nm, or any point value within the above thickness range.

[0040] In some preferred embodiments, the thickness of the elastic polymer electrolyte coating layer is 16.5 nm. 45nm.

[0041] In some embodiments, the elastic polymer electrolyte includes at least one of polyethylene oxide, polyethylene oxide-polypropylene oxide, poly(p-phenylenebenzodioxazole)-polyethylene oxide, polyethylene oxide-polypropylene carbonate, polydimethylsiloxane-polyethylene glycol, polyvinylidene fluoride-hexafluoropropylene, and polyacrylic acid-polyethylene glycol.

[0042] In addition to its elasticity and ion transport capabilities, the aforementioned elastic polymer electrolyte also possesses viscosity. On the one hand, this further enhances the bonding strength with the lithium-intercalated MXene, and on the other hand, it works synergistically with the binder to help suppress the expansion of silicon-oxygen materials.

[0043] In some embodiments, the adhesive includes at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, sodium alginate, waterborne polyurethane, polyacrylate, and chitosan-based adhesive.

[0044] The binder firmly bonds the silicon-oxygen material to the first material. Simultaneously, the binder possesses a certain degree of elasticity or toughness, absorbing expansion stress through its own deformation. Combined with the rigid support of the lithium intercalation layer's MXene and the elastic network of the elastic polymer electrolyte coating layer, it jointly suppresses electrode structure cracking and reduces the loss of active material. Furthermore, the binder exhibits good dispersibility, ensuring the first material is uniformly dispersed within the system, avoiding localized conductive / ion conduction blind zones. The polyacrylic acid and sodium carboxymethyl cellulose have good compatibility with the electrolyte and do not significantly hinder lithium-ion migration within the electrode, thus ensuring battery charge / discharge efficiency.

[0045] This invention also provides a method for preparing a negative electrode, used to prepare a negative electrode as described in any of the above embodiments, comprising the following steps:

[0046] S110, Preparation of lithium-intercalated MXene.

[0047] In some implementations, this step includes:

[0048] MXene, lithium source, and urea are mixed in a preset ratio to obtain a mixture; the mixture is then heated to 400°C under an inert atmosphere. Sintering at 500℃ for 3 hours Lithium-intercalated MXene was obtained in 6 hours.

[0049] A high-temperature solid-state reaction ensures that lithium ions are fully intercalated between MXene layers, forming a stable lithium-intercalated MXene structure. The addition of urea effectively widens the interlayer spacing, facilitating lithium ion intercalation.

[0050] In some embodiments, the lithium source includes at least one of lithium borohydride, lithium aluminum hydride, and lithium carbonate.

[0051] In some implementations, the reaction is preferably carried out in an inert atmosphere, preferably argon (Ar). Sufficient time must be allowed to purge the air from the tubular furnace beforehand to prevent the MXene precursor and product from being oxidized.

[0052] At 400℃ Temperature range of 500℃ and 3h The sintering time of 6 hours has been verified through multiple experiments to ensure that the reaction proceeds fully while avoiding damage to the structure of the lithium-intercalated MXene.

[0053] The lithium-intercalated MXene obtained in this application is a MXene composite material with successful lithium-ion intercalation, expanded interlayer spacing, and surface chemical modification, transforming ordinary MXene into a multifunctional material with high-speed ion channels, structural buffer fulcrums, and internal lithium replenishment warehouses.

[0054] S120, a first material is obtained by coating lithium-intercalated MXene with an elastic polymer electrolyte.

[0055] Specifically, the elastic polymer electrolyte is dissolved in an organic solvent to prepare an elastic polymer electrolyte solution, wherein the concentration of the elastic polymer electrolyte in the solution is 5%. 15 g / L. Add the lithium-intercalated MXene obtained in step S110 to the elastic polymer electrolyte solution and stir for 1 hour. The mixture was obtained after 3 hours and then heated at 60°C. Vacuum dry the mixture at 80℃ for 6 hours The first material was obtained in 12 hours.

[0056] The choice of organic solvent is not limited in this application. It has good solubility in elastic polymer electrolytes and can be easily dried afterward. For example, it can be at least one of acetone and tetrahydrofuran.

[0057] S130. Mix the first material and the silicon oxide material and add a binder to obtain a negative electrode slurry.

[0058] Specifically, the first material is mixed with the silicon oxide material, a binder and an appropriate amount of solvent are added, and the mixture is stirred until homogeneous for 1 hour. 3h.

[0059] In some embodiments, the negative electrode slurry also includes a conductive material. The conductive material may include any conductive material that does not cause a chemical change. Non-limiting examples of conductive materials include at least one of carbon-based materials, metals and their derivatives, conductive polymers, and MXenes; wherein, carbon-based materials include, but are not limited to, natural graphite, artificial graphite, graphene, carbon black, acetylene black, Ketjen black, superconducting carbon black, carbon nanotubes, carbon fibers, etc.; metals and their derivatives include, but are not limited to, metal powders, metal fibers, metal nanowires, etc., and metals include, but are not limited to, copper, nickel, aluminum, silver, etc.; conductive polymers include, but are not limited to, polypyrrole, PEDOT:PSS, polyaniline, etc.

[0060] S140. The negative electrode is obtained by coating the negative electrode slurry onto the negative electrode current collector and drying it.

[0061] Specifically, the thoroughly stirred negative electrode slurry is coated onto the negative electrode current collector. It is understood that the drying temperature and time can be determined based on the boiling point of the solvent in the negative electrode slurry. For example, drying at 60–100°C for 8–16 hours may be used.

[0062] In some embodiments, the negative current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, and combinations thereof.

[0063] Embodiments of the present invention also provide a battery, including a positive electrode and a negative electrode as described above.

[0064] In some embodiments, the positive electrode includes a positive current collector and a positive electrode layer disposed on the positive current collector.

[0065] In some embodiments, the positive electrode layer includes a positive electrode active material, which includes a compound that can reversibly insert and deintercalate lithium ions.

[0066] In some embodiments, the positive electrode active material comprises one or more transition metal cations, such as manganese (Mn), nickel (Ni), cobalt (Co), chromium (Cr), iron (Fe), vanadium (V), and combinations thereof.

[0067] In some embodiments, the positive electrode active material is one of layered oxides, spinel oxides, and polyanionic compounds.

[0068] In some embodiments, the layered oxides (e.g., rock salt layered oxides) include LiCoO2 (LCO) and LiNi. x Mn y Co 1-x-y O2 (where 0 ≤ x ≤ 1 and 0 ≤ y ≤ 1), LiNi 1-x-y Co x Al y O2 (where 0 ≤ x ≤ 1 and 0 ≤ y ≤ 1), LiNi x Mn 1-x O2 (where 0≤x≤1) and xLi2MnO3·(1-x)LiTMO2 (where M is one of Mn, Ni, and Co; 0≤x≤1).

[0069] In some embodiments, the spinel oxide includes LiMn2O4 (LMO) and LiNi. 0.5 Mn 1.5 O4.

[0070] In some embodiments, the polyanionic compound includes a phosphate, such as LiFePO4, LiMnPO4, Li3V2(PO4)3, or LiMn. x Fe 1-x At least one of PO4 (0 < x < 1) and its doped derivatives.

[0071] In some embodiments, the polyanionic compound includes a silicate, which includes Li2FeSiO4.

[0072] In some implementations, the mass of the positive electrode active material accounts for 60% to 95% of the mass of the positive electrode layer.

[0073] In some embodiments, the positive electrode layer also includes a binder. The binder can improve the bonding between the positive electrode active material particles and also improve the bonding between the positive electrode layer and the positive electrode current collector.

[0074] In some embodiments, non-limiting examples of adhesives include polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0075] It is understood that when the positive electrode layer is prepared using a dry method, the binder should include at least a fibrous binder, including but not limited to one or more of polytetrafluoroethylene, polyvinylidene fluoride (PVDF), polyvinylidene fluoride hexafluoropropylene, polypropylene, polyethylene, and polyimide.

[0076] In some embodiments, the binder accounts for 0.1% to 20% of the mass of the positive electrode layer.

[0077] In some embodiments, the positive electrode layer also includes a conductive agent to impart conductivity to the electrode. The conductive agent can include any conductive material, as long as it does not cause a chemical change.

[0078] In some embodiments, the conductive agent includes carbon-based materials, metals and their derivatives, conductive polymers, and MXenes, etc.

[0079] Among them, carbon-based materials include, but are not limited to, natural graphite, artificial graphite, graphene, carbon black, acetylene black, Ketjen black, superconducting carbon black, carbon nanotubes, carbon fibers, etc.

[0080] Metals and their derivatives include, but are not limited to, metal powders, metal fibers, metal nanowires, etc., and metals include, but are not limited to, copper, nickel, aluminum, silver, etc.

[0081] Conductive polymers include, but are not limited to, polypyrrole, PEDOT:PSS, and polyaniline.

[0082] In some embodiments, the conductive agent accounts for 0.1% to 20% of the mass of the positive electrode layer.

[0083] In some embodiments, the positive electrode layer also includes a fast ion conductor to improve the ionic conductivity of the positive electrode layer. This invention does not limit the type of fast ion conductor; it can be an oxide solid electrolyte, a sulfide solid electrolyte, a halide solid electrolyte, a lithium salt, etc.

[0084] In some embodiments, the mass of the fast ion conductor accounts for 1% to 20% of the mass of the positive electrode layer; preferably 5% to 20%.

[0085] In some embodiments, the positive electrode includes a positive current collector, which includes a metallic material capable of conducting electrons, including but not limited to at least one of aluminum, nickel, tin, copper, and stainless steel.

[0086] In some embodiments, the positive current collector includes at least one of aluminum foil, carbon-coated aluminum foil, stainless steel foil, nickel foam, and porous metal.

[0087] In some embodiments, the battery of this application has a separator between the positive and negative electrodes to prevent short circuits. The material and shape of the separator used in the battery of this application are not particularly limited, and can be any technology disclosed in the prior art.

[0088] In some embodiments, the diaphragm comprises a polymer or inorganic material formed from a material stable to the electrolyte of this application.

[0089] In some embodiments, the diaphragm may include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide.

[0090] In some implementations, the battery also includes an electrolyte.

[0091] In some implementations, the electrolyte includes a lithium salt and a solvent.

[0092] In some embodiments, the lithium salt includes, but is not limited to: lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium bis(oxalateborate)borate LiB(C2O4)2 (LiBOB), or lithium difluorooxalateborate LiBF2(C2O4) (LiDFOB).

[0093] In some embodiments, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0094] In some embodiments, the electrolyte also includes additives. These additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance characteristics, such as additives that improve battery overcharge performance, high-temperature performance, and low-temperature performance.

[0095] In some embodiments, the aforementioned additives include 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, propenyl-1,3-sulfonyl lactone, vinyl sulfate, and 4... At least one of the following: methyl vinyl sulfate, propylene sulfate, saturated phosphate compounds and unsaturated phosphate compounds, tris(trimethylsilane) phosphate, tris(trimethylsilane) borate, tris(triethylsilane) borate, succinic acid nitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptanonitrile, octanilide, nonadionitrile, and sebaconitrile.

[0096] In some implementations, the battery includes a solid electrolyte layer.

[0097] In some embodiments, the solid electrolyte layer includes one of an organic solid electrolyte and an inorganic solid electrolyte; the organic solid electrolyte includes a polymer electrolyte, which includes one of a polyoxyethylene electrolyte, a polyvinylidene fluoride electrolyte, a polyacrylonitrile-based electrolyte, and a polymethyl methacrylate (PMMA)-based electrolyte.

[0098] Inorganic solid electrolytes include one or more of the following: oxide solid electrolytes, sulfide solid electrolytes, halide solid electrolytes, hydride solid electrolytes, boride solid electrolytes, and nitride solid electrolytes.

[0099] In some embodiments, the oxide solid electrolyte is composed of oxide solid electrolyte particles, including garnet ceramics, LISICON type oxides, NASICON type oxides, and perovskite type ceramics.

[0100] Garnet ceramics include, but are not limited to, Li 6.5 La 24 Zr 1.75 Te 0.25 O 12 、Li7La 24 Zr2O 12 Li 6.2 Ga 0.24 La 2.95 Rb 0.05 Zr2O 12 Li 6.85 La 2.9 Ca 0.1 Zr 1.75Nb 0.25 O 12 Li 6.25 Al 0.25 La 24 Zr2O 12 Li 6.75 La 24 Zr 1.75 Nb 0.25 O 12 Li 6.75 La 24 Zr 1.75 Nb 0.25 O 12 And their combinations.

[0101] LISICON type oxides include, but are not limited to, Li 14 Zn(GeO4)4, Li 24+x (P 1-x Si x O4 (where 0 < x < 1), Li 24+x Ge x V 1-x O4 (where 0 < x < 1) and their combinations.

[0102] NASICON-type oxides can be produced from LiMM′(PO4). 24 Defined where M and M′ are independently selected from Al, Ge, Ti, Sn, Hf, Zr, and La. NASICON-type oxides include, but are not limited to, Li. 1+x Al x Ge 2-x (PO4) 24 (LAGP) (where 0 ≤ x ≤ 2), Li 1+ x Al x Ti 2-x (PO4) 24 (LATP) (where 0 ≤ x ≤ 2), Li 1+x Y x Zr 2-x (PO4) 24 (LYZP) (where 0≤x≤2), Li 1.24 Al 0.24 Ti 1.7 (PO4) 24 LiTi2(PO4) 24 LiGeTi(PO4) 24 LiGe2(PO4) 24 LiHf2(PO4) 24 And their combinations.

[0103] Perovskite ceramics include, but are not limited to, Li 24.24 La 0.524 TiO 24 LiSr 1.65 Zr 1.24 Ta 1.7 O9、Li 2x-y Sr 1- x Ta y Zr 1-y O 24 (where x = 0.75y and 0.60 < y < 0.75), Li 24 / 8 Sr 7 / 16 Nb 24 / 4 Zr 1 / 4 O 24 Li 24x La (2 / 24-x) TiO 24 (where 0 < x < 0.25) and their combinations.

[0104] In some embodiments, the ionic conductivity of the oxide solid electrolyte is 10. -5 S / cm~10 -1 S / cm.

[0105] In some embodiments, the sulfide solid electrolyte is composed of sulfide solid electrolyte particles, including but not limited to Li2S-P2S5 and Li2S-P2S5-MS. x (where M is Si, Ge, and Sn and 0 ≤ x ≤ 2), Li 24.4 Si 0.4 P 0.6 S4, Li 10 GeP2S 11.7 O 0.24 Li 9.6 P 24 S 12 Li7P 24 S 11 Li9P 24 S9O 24 Li 10.245 Si 1.245 P 1.65 S 12 Li 9.81 Sn 0.81 P 2.19 S 12 Li 10 (Si 0.5 Ge 0.5 P2S 12 Li (Ge 0.5 Sn 0.5 P2S12 Li 10 GeP2S 12 (LGPS), Li6PS5X (where X is Cl, Br, or I), Li7P2S8I, Li 10.245 Ge 1.245 P 1.65 S 12 Li 24.25 Ge 0.25 P 0.75 S4, Li 10 SnP2S 12 Li 10 SiP2S 12 Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.24 , (1-x)P2S5-xLi2S (where 0.5≤x≤0.7) and their combinations.

[0106] In some embodiments, the ionic conductivity of the sulfide solid electrolyte is 10. -7 S / cm ~ 1S / cm.

[0107] In some embodiments, the halide solid electrolyte layer includes halide solid electrolyte particles, and the halide solid electrolyte particles include Li a M b X c N d M includes one or more of the basic metal elements, such as Zr, Hf, In, Sc, Y, La, Ce, Pr, Nb, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. M also includes doped metal elements, used in conjunction with the aforementioned basic metal elements, such as one or more of Nb, Ta, Al, La, Mg, Ca, Ba, and Ag. X includes one or more of F, Cl, Br, and I. N includes one or more of O and S, and satisfies a+mb=c+nd, where m and n are the weighted valences of M and N, respectively, 1≤a≤4, b>0, c>0, and d≥0.

[0108] For example, the halide solid electrolyte particles can be Li₂ZrCl₆, Li₂ZrCl₅F, or Li₂ZrCl₆. 5.5 O 0.25 At least one of Li3InCl6, Li3YCl6, Li2HfCl6, LiInBr4, Li3InBr6, Li3LaI6, Li3LuCl6, and Li3ErCl6.

[0109] In some embodiments, the ionic conductivity of the halide solid electrolyte is 10. -8 S / cm~10 -1 S / cm.

[0110] In some embodiments, the hydride solid electrolyte is composed of hydride solid electrolyte particles, including but not limited to Li 24 AlH6, LiBH4, LiBH4-LiX (where X is one of Cl, Br and I), LiNH2, Li2NH, LiBH4-LiNH2 and combinations thereof.

[0111] In some embodiments, the ionic conductivity of the hydride solid electrolyte is 10. -7 S / cm~10 -2 S / cm.

[0112] In some embodiments, the boride solid electrolyte is composed of borate solid electrolyte particles, including but not limited to Li₂B₄O₇ and Li₂O-(B₂O₃)₂O₃. 24 )-(P2O5) and their combinations.

[0113] In some embodiments, the ionic conductivity of the boride solid electrolyte is 10. -7 S / cm~10 -2 S / cm.

[0114] In some embodiments, the nitride solid electrolyte comprises nitride solid electrolyte particles, including Li 24 N, Li7PN4, LiSi2N 24 LiPON and their combinations.

[0115] In some embodiments, the ionic conductivity of the nitride solid electrolyte is 10. -9 S / cm ~ 1S / cm.

[0116] The present application will be further described in detail below with reference to embodiments. It should be noted that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection claimed in this application.

[0117] Example 1: This example provides a negative electrode, the preparation method of which includes:

[0118] (1) Preparation of Li3Ti3C2Tx: The Ti3C2Tx precursor was mixed with Li2CO3 and urea at a mass ratio of 1:0.22:0.23, placed in a quartz crucible, placed in a tube furnace, and argon gas was introduced to remove air. The temperature was raised to 400℃ and sintered for 6 hours. After natural cooling, Li3Ti3C2Tx was obtained.

[0119] (2) PEO (polyethylene oxide) coating treatment: 10g of PEO was dissolved in 1000mL of acetone to prepare a 10g / L PEO-acetone solution. 10g of the above-prepared Li3Ti3C2Tx was added to the above PEO-acetone solution and stirred for 2h. The mixture was then placed in a vacuum drying oven and vacuum dried at 70℃ for 8h to obtain the first material. The mass ratio of PEO to Li3Ti3C2 was 0.1:1, and the thickness of the PEO coating layer in the first material was 30nm.

[0120] (3) Composite treatment: Mix 5g of the first material with 10g of silicon oxide material, add 0.75g of sodium carboxymethyl cellulose, 0.8g of conductive carbon black and an appropriate amount of deionized water, stir evenly and coat it on copper foil, dry at 80℃ for 12 hours to obtain the negative electrode sheet.

[0121] Example 2: This example provides a negative electrode, the preparation method of which differs from that of Example 1 in that the mass ratio of PEO to Li3Ti3C2Tx is 0.05:1, and the thickness of the PEO coating layer in the first material is 16.5 nm.

[0122] Example 3: This example provides a negative electrode, the preparation method of which differs from that of Example 1 in that the mass ratio of PEO to Li3Ti3C2Tx is 0.2:1, and the thickness of the PEO coating layer in the first material is 45nm.

[0123] Example 4: This example provides a negative electrode, the preparation method of which differs from that of Example 1 in that: the mass ratio of PEO to Li3Ti3C2Tx is 0.1:1, the thickness of the PEO coating layer in the first material is 30nm, and the mass ratio of the first material to the silicon-oxygen material is 0.1:1.

[0124] Example 5: This example provides a negative electrode, the preparation method of which differs from that of Example 1 in that the ratio of the sum of the masses of the first material and the silicon oxide material to the mass of the binder is 1:0.1.

[0125] Example 6: This example provides a negative electrode, the preparation method of which differs from that of Example 1 in that: the mass ratio of PEO to Li3Ti3C2Tx is 0.3:1, the thickness of the PEO coating layer in the first material is 70nm, the mass ratio of the first material to the silicon-oxygen material is 1:1, and the ratio of the sum of the masses of the first material and the silicon-oxygen material to the mass of the binder is 1:0.2.

[0126] Example 7: This example provides a negative electrode, the preparation method of which differs from that of Example 1 in that: PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene) is used to coat Li3Ti3C2Tx, and the thickness of the PVDF-HFP coating layer in the first material is 25nm.

[0127] Comparative Example 1: This comparative example provides a negative electrode in which the first material does not use an elastic polymer electrolyte coating layer to coat Li3Ti3C2Tx, and the ratio of the sum of the masses of the first material and the silicon oxide material to the mass of the binder is 1:0.075.

[0128] The negative electrode sheets prepared in the above embodiments and comparative examples were assembled into button batteries, using lithium metal as the counter electrode and a 1 mol / L LiPF6 EC / DMC / EMC (volume ratio 1:1:1) solution as the electrolyte, and the assembly was carried out in a glove box. The assembled batteries were subjected to constant current charge-discharge tests, with a test voltage range of 0.01-3.0V and a current density of 0.1A / g.

[0129] First Coulomb efficiency test:

[0130] At room temperature (25℃), the prepared battery was charged at a constant current density of 0.1 A / g to the charging cutoff voltage of 3.0 V, and the initial charging capacity was recorded. Then, the battery was discharged at a constant current density of 0.1 A / g to the discharging cutoff voltage of 0.01 V, and the initial discharging capacity was recorded. The initial coulombic efficiency = initial discharging capacity / initial charging capacity. 100%.

[0131] Cyclic capacity retention test:

[0132] ① Place the battery at room temperature of 25℃ and charge it at a constant current density of 0.1A / g until the charging cutoff voltage of 3.0V, then let it stand for 1 hour;

[0133] ② At room temperature of 25℃, discharge at a constant current density of 0.1A / g until the discharge cutoff voltage is 0.01V, and let stand for 1 hour;

[0134] ③Repeated steps ① ②200 cycles, cycle performance = discharge capacity on the 200th cycle / discharge capacity on the first cycle.

[0135] The test results are shown in Table 1:

[0136] Table 1

[0137]

[0138] Referring to the above embodiments and comparative data, it can be seen that adding a first material to the negative electrode can effectively improve the initial coulombic efficiency of the battery and enhance its cycle performance. The likely reason is that by adding the first material, which includes lithium-intercalated MXene and an elastic polymer coating layer, and bonding the first material to the silicon oxide material with an adhesive, a three-dimensional elastic network with ion-conducting function is constructed around the silicon oxide material. The lithium-intercalated MXene, as rigid particles, is dispersed within this network, effectively suppressing the expansion of the silicon oxide material during charge-discharge cycles and improving the battery's cycle performance. Simultaneously, the lithium-intercalated MXene can act as a lithium replenishment material, and the elastic polymer electrolyte coating layer provides channels for lithium-ion transport, effectively achieving lithium replenishment and improving the battery's initial charge-discharge efficiency.

[0139] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0140] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0141] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A negative electrode, characterized in that, The material includes a silicon oxide material, a first material, and a binder. The first material includes a lithium-intercalated MXene and an elastic polymer electrolyte coating layer covering the surface of the lithium-intercalated MXene. The first material is bonded to the silicon-oxygen material using the adhesive, thereby constructing a three-dimensional elastic network with ion-conducting function around the silicon-oxygen material, in which the lithium-intercalated MXene is dispersed as rigid particles.

2. The negative electrode according to claim 1, characterized in that, The ratio of the sum of the masses of the first material and the silicon-oxygen material to the mass of the adhesive is 1:(0.05~0.1).

3. The negative electrode according to claim 1, characterized in that, The mass ratio of the first material to the silicon-oxygen material is (0.1). 0.5):

1.

4. The negative electrode according to claim 1, characterized in that, The mass ratio of the lithium-intercalated MXene to the elastic polymer electrolyte coating is 1:(0.05). 0.2).

5. The negative electrode according to claim 1, characterized in that, The lithium-intercalated MXene includes at least one of Li3Ti3C2Tx, Li2Ti2CTx, and Li2V2CTx, where T is an electronegative surface functional group and x is the average total number of surface functional groups on each repeating structural unit in the MXene material.

6. The negative electrode according to claim 1, characterized in that, The thickness of the elastic polymer electrolyte coating layer is 10 nm. 70nm.

7. The negative electrode according to claim 1, characterized in that, The elastic polymer electrolyte includes at least one of polyethylene oxide, polyethylene oxide-polypropylene oxide, poly(p-phenylenebenzodioxazole)-polyethylene oxide, polyethylene oxide-polypropylene carbonate, polydimethylsiloxane-polyethylene glycol, polyvinylidene fluoride-hexafluoropropylene, and polyacrylic acid-polyethylene glycol.

8. The negative electrode according to claim 1, characterized in that, The adhesive includes at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, sodium alginate, waterborne polyurethane, polyacrylate, and chitosan-based adhesive.

9. A method for preparing a negative electrode, characterized in that, The method for preparing the negative electrode according to any one of claims 1-8 comprises the following steps: Preparation of lithium-intercalated MXene; A first material is obtained by coating the lithium intercalation layer with an elastic polymer electrolyte, MXene. The first material and the silicon-oxygen material are mixed and a binder is added to obtain a negative electrode slurry; The negative electrode is obtained by coating the negative electrode slurry onto the negative electrode current collector and drying it.

10. A battery, comprising a positive electrode, characterized in that, Includes the negative electrode as described in any one of claims 1 to 8.

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