Negative current collector, preparation method thereof and all-solid-state battery

Abstract

The invention provides a negative electrode current collector, a preparation method thereof and an all-solid-state battery. The negative electrode current collector comprises a substrate layer, a first coating and a second coating which are sequentially stacked, the first coating comprises a composite material with a first metal and MXene carbide, and the second coating comprises a second compound; wherein the first metal comprises at least one of silver, gold, tin, zinc, lead or bismuth; the general formula of the MXene carbide is Mn + 1CnTx, M comprises at least one of titanium, vanadium, niobium, molybdenum, tantalum, chromium, zirconium, hafnium, scandium or tungsten, n is equal to 1-3, and Tx comprises at least one of-OH,-O or-F; the second compound comprises at least one of aluminum oxide, magnesium oxide, lithium fluoride, magnesium fluoride, calcium fluoride or boron nitride. The negative electrode current collector, the preparation method thereof and the all-solid-state battery provided by the invention are simple in structure, convenient to manufacture and high in stability, and can improve the battery performance and prolong the service life.

Description

Negative electrode current collector and its preparation method, all-solid-state battery Technical Field

[0001] This disclosure relates to the field of battery technology, and in particular to a negative electrode current collector and its preparation method, and an all-solid-state battery. Background Technology

[0002] All-solid-state lithium batteries are widely considered a key direction for the development of next-generation battery technology due to their high safety, high energy density, and long cycle life. Among all-solid-state battery systems, anode-free batteries have attracted significant attention due to their potential for even higher energy density. Traditional lithium-ion batteries require pre-fabricated lithium sources as anode materials, which not only increases battery cost but also reduces energy density. Anode-free batteries, on the other hand, eliminate the need for pre-fabricated anode active materials by allowing lithium ions to be extracted from the positive electrode and deposited on the surface of the negative electrode current collector during the first charge.

[0003] However, current electrodeless batteries also face severe technical challenges. The interface between lithium metal and the electrolyte is unstable, easily forming a high-resistivity interface layer, which affects battery performance and lifespan. Therefore, there is an urgent need for a battery with better performance and longer lifespan. Summary of the Invention

[0004] In view of this, the purpose of this disclosure is to provide a negative electrode current collector and its preparation method, and a battery to solve the above-mentioned technical problems.

[0005] A first aspect of this disclosure provides a negative electrode current collector, comprising a substrate layer, a first coating, and a second coating sequentially stacked; the first coating comprises a composite material having a first metal and an MXene carbide, and the second coating comprises a second compound; wherein the first metal comprises at least one selected from silver, gold, tin, zinc, lead, or bismuth; and the MXene carbide has the general formula M n+1 C n T x M includes at least one of titanium, vanadium, niobium, molybdenum, tantalum, chromium, zirconium, hafnium, scandium, or tungsten, n=1~3, T x The first compound includes at least one of -OH, -O, or -F; the second compound includes at least one of aluminum oxide, magnesium oxide, lithium fluoride, magnesium fluoride, calcium fluoride, or boron nitride.

[0006] In some embodiments, the mass fraction of the composite material is greater than or equal to 90% based on the total mass of the first coating.

[0007] In some embodiments, the mass ratio of the MXene carbide to the first metal is 1:1 to 100:1.

[0008] In some embodiments, the mass ratio of the MXene carbide to the first metal is 40:1 to 60:1.

[0009] In some embodiments, the MXene carbide has a layered structure, and at least a portion of the first metal is incorporated into the interior of the layered structure to form the composite material.

[0010] In some embodiments, the thickness ratio of the first coating to the second coating is 1:1 to 100:1; and / or the thickness of the first coating is 500 nm to 5000 nm, and the thickness of the second coating is 50 nm to 1000 nm.

[0011] A second aspect of this disclosure provides a method for preparing a negative electrode current collector, comprising: preparing a first negative electrode slurry and a second negative electrode slurry, wherein the first negative electrode slurry comprises a composite material having a first metal and an MXene carbide, and the second negative electrode slurry comprises a second compound, wherein the first metal comprises at least one selected from silver, gold, tin, zinc, lead, or bismuth; and the general formula of the MXene carbide is M n+1 C n T x M includes at least one of titanium, vanadium, niobium, molybdenum, tantalum, chromium, zirconium, hafnium, scandium, or tungsten, n=1~3, T x The first negative electrode slurry is coated on the substrate layer and dried to form a first coating; the second negative electrode slurry is coated on the side of the first coating away from the substrate layer and dried to form a second coating, thereby obtaining the negative electrode current collector.

[0012] In some embodiments, the method for preparing the composite material includes: preparing a dispersion containing MXene carbide and a solution containing a first metal salt; adding the solution to the dispersion, adding a reducing agent to react, and then filtering and drying to obtain a composite material having a first metal and MXene carbide.

[0013] In some embodiments, the first metal salt comprises at least one of silver nitrate, tetrachloroauric acid, stannous chloride, zinc sulfate, lead nitrate, or bismuth nitrate; and / or the concentration of the solution is from 0.01 mol / L to 0.1 mol / L; and / or the reducing agent comprises at least one of sodium borohydride, ascorbic acid, sodium citrate, or hydrazine hydrate; and / or the molar ratio of the reducing agent to the first metal salt is from 3:1 to 20:1.

[0014] A third aspect of this disclosure provides an all-solid-state battery, comprising: a positive electrode, a negative current collector, and an electrolyte, wherein the negative current collector is the negative current collector described in the first aspect above.

[0015] As can be seen from the above, this disclosure provides a negative electrode current collector and its preparation method, as well as an all-solid-state battery. The negative electrode current collector includes a substrate layer, a first coating layer, and a second coating layer sequentially stacked. The first coating layer includes a composite material having a first metal and an MXene carbide, and the second coating layer includes a second compound. The first metal includes at least one of silver, gold, tin, zinc, lead, or bismuth. The general formula of the MXene carbide is M... n+1 C n T x M includes at least one of titanium, vanadium, niobium, molybdenum, tantalum, chromium, zirconium, hafnium, scandium, or tungsten, n=1~3, T x The first coating comprises at least one of -OH, -O, or -F; the second compound comprises at least one of aluminum oxide, magnesium oxide, lithium fluoride, magnesium fluoride, calcium fluoride, or boron nitride. By incorporating MXene carbide in the first coating, its two-dimensional layered structure can serve as a stable framework or confined space for lithium deposition, improving the reversibility of deposition / stripping. Simultaneously, the synergistic effect of the MXene carbide and the first metal lowers the lithium nucleation energy barrier, promotes uniform lithium deposition, and effectively inhibits the formation and growth of lithium dendrites. By incorporating the second compound in the second coating, the longitudinal growth of lithium dendrites can be restricted, and the contact between the electrolyte in the battery and the first coating can be isolated, reducing the occurrence of side reactions. The synergistic effect of the first and second coatings has been tested and shows a significant improvement in the battery's initial coulombic efficiency, cycle stability, and rate performance, while also suppressing the risk of internal short circuits and enhancing battery safety. This negative electrode current collector and its preparation method, along with the all-solid-state battery, have a simple structure, are easy to manufacture, and exhibit strong stability, thus improving battery performance and lifespan. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments.

[0017] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this disclosure should have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure pertains.

[0018] In this disclosure, the term "range" is used to define a range in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~130 and 70~120 are listed for a specific parameter, it is expected that ranges of 60~120 and 70~130 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this disclosure, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12.

[0019] Unless otherwise specified, all embodiments and optional embodiments of this disclosure can be combined to form new technical solutions.

[0020] Unless otherwise specified, all technical features and optional technical features of this disclosure can be combined to form new technical solutions.

[0021] Unless otherwise specified, the terms "comprising" and "including" as used in this disclosure can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0022] Unless otherwise specified, the term "or" is inclusive in this disclosure. For example, the phrase "A or B" means "A, B, or both A and B".

[0023] Terminology Explanation: MXene compounds are novel two-dimensional materials composed of metal carbides, nitrides, or carbonitrides. Generally, MXene materials can be represented by the general formula M... n+1 X n T x The symbol indicates that "M" represents a metallic element, mainly transition metals such as chromium, molybdenum, manganese, iron, cobalt, copper, aluminum, silver, nickel, palladium, platinum, and ruthenium; "X" represents carbon and nitrogen; and "T" represents... x"" represents the functional groups on the material surface, such as -F, -O, -OH, etc.; n represents the number of layers, n=1, 2, 3. MXene materials have excellent flexibility, good electronic conductivity, and excellent mechanical properties.

[0024] Currently, in electrodeless batteries, the exposed surface of the negative electrode current collector typically has low affinity for lithium ions and uneven surface energy, leading to uneven nucleation and growth of lithium metal during deposition. Specifically, lithium ions have few and unevenly distributed nucleation sites on the exposed current collector surface, causing lithium metal to preferentially grow rapidly in certain areas, forming lithium dendrites. This can easily lead to short circuits, affecting interface stability and safety. During deposition and stripping, lithium metal can undergo side reactions with the current collector surface or the resulting interface layer, forming irreversible "dead lithium," resulting in the loss of active lithium with each cycle, reducing the battery's cycle coulombic efficiency and overall capacity retention. Significant volume changes occur during lithium metal deposition and stripping. On the exposed current collector surface, these changes can easily lead to deterioration of the contact between the lithium layer and the current collector, and between the lithium layer and the electrolyte, increasing interface resistance and interfacial mechanical stress, thus affecting battery power performance and cycle life.

[0025] In view of this, the present disclosure provides a negative electrode current collector, a method for preparing the same, and a battery. The negative electrode current collector includes a base layer, a first coating, and a second coating sequentially stacked. The first coating includes a composite material containing a first metal and MXene carbide, and the second coating includes a second compound. By providing a lithium-loving first coating with metal doping, the nucleation overpotential of lithium is reduced, guiding lithium ions to uniformly nucleate and deposit on the surface of the current collector, thus avoiding excessive local current density. By providing a lithium-repellent second coating, as a physical and electrochemical barrier, the longitudinal growth of lithium dendrites is restricted, and the contact between the solid electrolyte and the first coating is isolated, reducing the occurrence of side reactions. Through the above-mentioned synergistic effect of the two layers, the initial coulombic efficiency, cycle stability, and rate performance of the electrodeless all-solid-state battery are significantly improved, and the risk of internal short circuits is suppressed, thereby enhancing the intrinsic safety of the battery.

[0026] To make the technical solutions of this disclosure clearer and easier to understand, the negative electrode current collector, its preparation method, and the battery provided in this disclosure will be described in detail below with reference to specific embodiments.

[0027] Negative current collector In a first aspect, embodiments of this disclosure provide a negative electrode current collector, comprising a substrate layer, a first coating layer, and a second coating layer sequentially stacked; the first coating layer comprises a composite material having a first metal and an MXene carbide, and the second coating layer comprises a second compound; wherein the first metal comprises at least one selected from silver, gold, tin, zinc, lead, or bismuth; and the MXene carbide has the general formula M n+1 C n Tx M includes at least one of titanium, vanadium, niobium, molybdenum, tantalum, chromium, zirconium, hafnium, scandium, or tungsten, n=1~3, T x The first compound includes at least one of -OH, -O, or -F; the second compound includes at least one of aluminum oxide, magnesium oxide, lithium fluoride, magnesium fluoride, calcium fluoride, or boron nitride.

[0028] The negative electrode current collector includes a base layer, a first coating, and a second coating, disposed layer by layer from the inside out. Optionally, the base layer includes at least one of copper foil, nickel foil, stainless steel foil, or carbon paper. Exemplarily, the base layer is copper foil.

[0029] The first coating comprises a composite material having a first metal and an MXene carbide. The first metal is a lithium-philic metal, and optionally includes at least one of silver (Ag), gold (Au), tin (Sn), zinc (Zn), lead (Pb), or bismuth (Bi). Exemplarily, the first metal is silver and tin. The general formula of the MXene carbide is M. n+1 C n T x Optionally, M includes at least one of titanium (Ti), vanadium (V), niobium (Nb), molybdenum (Mo), tantalum (Ta), chromium (Cr), zirconium (Zr), hafnium (Hf), scandium (Sc), or tungsten (W). Exemplarily, M is chromium. Optionally, n = 1, 2, or 3. Exemplarily, n = 1. Optionally, T x Includes at least one of -OH, -O, or -F. For example, T x It is -F.

[0030] The first coating may or may not include a conductive agent and a binder. Optionally, the conductive agent is at least one of conductive carbon black, conductive graphite, carbon fiber, or carbon nanotubes. For example, the conductive agent is carbon fiber. Optionally, the binder is at least one of styrene-butadiene rubber latex, polyacrylic acid, lithium polyacrylate (PAALi), or polyacrylonitrile. For example, the binder is lithium polyacrylate.

[0031] The second coating includes a second compound. The second compound is a lithium-averse compound, and optionally, the second compound includes at least one selected from aluminum oxide (Al₂O₃), magnesium oxide (MgO), lithium fluoride (LiF), magnesium fluoride (MgF₂), calcium fluoride (CaF₂), or boron nitride (BN). Exemplarily, the second compound is aluminum oxide and magnesium oxide.

[0032] The second coating may or may not include an adhesive. Optionally, the adhesive is at least one selected from styrene-butadiene rubber latex, polyacrylic acid, lithium polyacrylate, or polyacrylonitrile. For example, the adhesive is lithium polyacrylate.

[0033] By incorporating MXene carbides in the first coating, their two-dimensional layered structure can serve as a stable framework or confined space for lithium deposition, improving the reversibility of deposition / stripping. Simultaneously, the synergistic effect of the MXene carbides and the first metal lowers the lithium nucleation energy barrier, promotes uniform lithium deposition, and effectively suppresses the formation and growth of lithium dendrites.

[0034] By incorporating a second compound into the second coating, the longitudinal growth of lithium dendrites can be restricted, and the contact between the electrolyte in the battery and the first coating can be isolated, reducing the occurrence of side reactions. The first and second coatings work synergistically to significantly improve the battery's initial coulombic efficiency, cycle stability, and rate performance, while suppressing the risk of internal short circuits and enhancing battery safety. Testing showed that the fabricated battery retained more than 90% of its capacity after 200 cycles at room temperature at 1C rate, with an initial coulombic efficiency greater than 80% and a critical current density greater than 8 mA / cm². 2 Fast charging capacity retention rate is greater than 80%.

[0035] This negative electrode current collector has a simple structure, is easy to manufacture, and has strong stability, which can improve battery performance and lifespan.

[0036] In some embodiments, the mass fraction of the composite material is greater than or equal to 90% based on the total mass of the first coating.

[0037] Optionally, the composite material accounts for 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% of the mass of the first coating to ensure the lithium metal deposition effect.

[0038] In some embodiments, the mass ratio of the MXene carbide to the first metal is 1:1 to 100:1.

[0039] Optionally, the mass ratio of MXene carbide to the first metal can be 1:1, 5:1, 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, or 100:1, etc., which, after testing, ensures battery performance. Excessive use of the first metal is avoided, as it disrupts the MXene carbide structure and reduces the continuity of ion / electron transport channels. Insufficient first metal is also avoided, as it can lead to lithium deposition concentrated in areas with high surface energy barriers, causing uneven local current density distribution.

[0040] In some embodiments, the mass ratio of the MXene carbide to the first metal is 40:1 to 60:1.

[0041] Optionally, the mass ratio of MXene carbide to the first metal is 40:1, 50:1, or 60:1, which, according to testing, can further improve battery performance and achieve better first coulombic efficiency, cycle stability, and rate performance.

[0042] In some embodiments, the MXene carbide has a layered structure, and at least a portion of the first metal is incorporated into the interior of the layered structure to form the composite material.

[0043] MXene carbides are two-dimensional, ordered layered structures that can serve as a stable framework or confined space for lithium deposition. A first metal can be at least partially incorporated into the layered structure through salt reduction, working synergistically with MXene carbides to lower the lithium nucleation energy barrier, promote uniform lithium deposition, and thus inhibit the formation and growth of lithium dendrites.

[0044] In some embodiments, the thickness ratio of the first coating to the second coating is 1:1 to 100:1; and / or the thickness of the first coating is 500 nm to 5000 nm, and the thickness of the second coating is 50 nm to 1000 nm.

[0045] Optionally, the thickness ratio of the first coating to the second coating can be 1:1, 5:1, 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, or 100:1, etc. Testing has ensured battery performance.

[0046] The thickness of the first coating is, for example, 500 nm, 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm. This avoids a first coating that is too thin, making it difficult to form a continuous lithiophilic surface. It also avoids a first coating that is too thick, as this would lengthen the lateral diffusion path of lithium ions, leading to uneven local current density distribution.

[0047] The thickness of the second coating is, for example, 50 nm, 100 nm, 250 nm, 500 nm, or 1 μm. This is to avoid the second coating being too thin, which could be pierced by lithium dendrites, and also to avoid the second coating being too thick, which would increase the lithium-ion migration barrier, leading to increased polarization and deterioration of rate performance.

[0048] Preparation methods of composite materials A second aspect of this disclosure provides a method for preparing a composite material, comprising: firstly, preparing a dispersion comprising MXene carbides.

[0049] The MXene carbide was dispersed in deionized water by ultrasonication to obtain a dispersion.

[0050] MXene carbides can be prepared in advance, for example, by preparing M... n+1 AlC nThe precursor powder was immersed in an etching solution and magnetically stirred, then centrifuged and washed until the pH of the supernatant was greater than 6. Layered MXene carbides were obtained by freeze drying.

[0051] Optionally, the etching solution is hydrofluoric acid (HF) or a mixed solution of ammonium fluoride and hydrochloric acid. The etching temperature is controlled at 10℃~30℃, the magnetic stirring time is 1h~24h, the centrifugation speed is 1000rpm~5000rpm, the centrifugation time is 1min~10min, the freeze-drying temperature is -60℃~-20℃, and the freeze-drying time is 24h~48h.

[0052] Next, a solution containing the first metal salt is prepared.

[0053] Optionally, the first metal salt includes at least one of silver nitrate (AgNO3), tetrachloroauric acid (HAuCl4), stannous chloride (SnCl2), zinc sulfate (ZnSO4), lead nitrate (Pb(NO3)2), or bismuth nitrate (Bi(NO3)3). For example, the first metal salt is silver nitrate.

[0054] The first metal salt is dissolved in deionized water to obtain a solution with a concentration of 0.01 mol / L to 0.1 mol / L. For example, the solution concentration may be 0.01 mol / L, 0.05 mol / L, or 0.1 mol / L.

[0055] Finally, the solution is added to the dispersion, and after the reducing agent is added and the reaction is carried out, the mixture is filtered and dried to obtain a composite material containing the first metal and MXene carbide.

[0056] A solution containing the first metal salt was slowly added dropwise to a dispersion containing MXene carbide. A reducing agent was added to carry out a water bath reaction. After the reaction was completed, the precipitate was collected by filtration. The precipitate was then washed by centrifugation with deionized water and vacuum dried to obtain the composite material.

[0057] Optionally, the reducing agent includes at least one of sodium borohydride, ascorbic acid, sodium citrate, or hydrazine hydrate. Exemplarily, the reducing agent is sodium borohydride. Optionally, the molar ratio of the reducing agent to the first metal salt is 3:1 to 20:1, such as 3:1, 5:1, 10:1, 15:1, or 20:1. Optionally, the water bath temperature is 0℃ to 80℃, the water bath reaction time is 1h to 3h, the centrifugation speed is 1000rpm to 5000rpm, and the centrifugation time is 1min to 10min.

[0058] Preparation method of negative electrode current collectorA third aspect of this disclosure provides a method for preparing a negative electrode current collector, comprising: firstly, preparing a first negative electrode slurry and a second negative electrode slurry, wherein the first negative electrode slurry comprises a composite material having a first metal and MXene carbide, and the second negative electrode slurry comprises a second compound.

[0059] A first negative electrode slurry for forming the first coating and a second negative electrode slurry for forming the second coating are prepared according to a preset ratio. For example, 98 wt% of the composite material and 2 wt% of lithium polyacrylate are thoroughly stirred in an aqueous solution to obtain the first negative electrode slurry, and 98 wt% of the second compound and 2 wt% of lithium polyacrylate are thoroughly stirred in an aqueous solution to obtain the second negative electrode slurry.

[0060] Then, the first negative electrode slurry is coated onto the substrate layer and dried to form the first coating.

[0061] A first negative electrode slurry is coated onto the substrate layer, and the first negative electrode slurry is dried at 30℃~120℃ to form a first coating.

[0062] Finally, the second negative electrode slurry is coated on the side of the first coating away from the substrate layer, and after drying, a second coating is formed to obtain the negative electrode current collector.

[0063] A second negative electrode slurry is coated on the first coating, and the second negative electrode slurry is dried at 30℃~120℃ to form the second coating.

[0064] The negative electrode current collector prepared by this method includes two functional coatings, which can improve battery performance and lifespan.

[0065] Battery A fourth aspect of this disclosure provides an all-solid-state battery, comprising: a positive electrode, a negative current collector, and an electrolyte, wherein the negative current collector is the negative current collector described in the first aspect above.

[0066] The electrolyte is, for example, a solid electrolyte. Optionally, the solid electrolyte includes at least one of sulfide electrolytes, halide electrolytes, or oxide electrolytes.

[0067] The positive electrode sheet includes a positive current collector and an active layer. The active layer includes a positive active material, a solid electrolyte, a conductive agent, or a binder. Optionally, the positive active material includes at least one of lithium nickel cobalt manganese oxide (NCM), lithium nickel oxide (LNO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium cobalt oxide (LCO), or lithium nickel cobalt aluminum oxide (NCA). The positive current collector is, for example, aluminum foil, the conductive agent is, for example, carbon fiber, and the binder is, for example, hydrogenated nitrile butadiene rubber. A method for preparing the positive electrode sheet is, for example, to thoroughly mix the positive active material, solid electrolyte, carbon fiber, and hydrogenated nitrile butadiene rubber in a xylene solvent system at a mass ratio of 70:25:2:3, coat the mixture onto an aluminum foil, dry it, and cold press it to obtain the positive electrode sheet.

[0068] The negative electrode current collector is the same as the negative electrode current collector described in the first aspect above, and will not be repeated here.

[0069] This battery is an all-solid-state lithium-ion battery. The assembly method involves, for example, cold-pressing a solid electrolyte at 300 MPa to obtain a 200 μm solid electrolyte membrane. The aforementioned positive electrode and negative current collector are then placed at both ends of the solid electrolyte membrane and pressed and sealed to obtain the all-solid-state lithium-ion battery. The assembly process is completed in a glove box with an inert atmosphere.

[0070] This all-solid-state battery boasts high stability, excellent performance, and a long lifespan.

[0071] Example The following describes embodiments of this disclosure. The embodiments described below are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0072] The all-solid-state lithium-ion battery of Embodiment 1 of this disclosure is prepared by the following specific method: Preparation of composite materials 1 g of Mo3AlC2 phase precursor powder was immersed in HF etching solution and magnetically stirred at 25 °C for 12 h. After adding deionized water, the mixture was repeatedly centrifuged and washed until the pH of the supernatant was >6. Then, layered Mo3C2T was obtained by freeze-drying at -50 °C for 30 h. x Among them, T x It can include -OH, -O, or -F. In other words, Mo3C2T x -OH, -O and -F can all be present.

[0073] 0.5 g of layered Mo3C2T x The dispersion was obtained by ultrasonic dispersion in deionized water for 30 minutes.

[0074] Dissolve 0.01 g of AgNO3 in deionized water to obtain a solution with a concentration of 0.05 mol / L.

[0075] AgNO3 solution was slowly added dropwise to Mo3C2T x Sodium borohydride, in amounts four times the molar ratio of AgNO3, was added to the dispersion. After reacting at 30°C for 3 h, the precipitate was centrifuged, washed, and dried under vacuum at 80°C to obtain a product containing Ag and Mo3C2T. x Composite materials.

[0076] Preparation of negative electrode current collector 0.49g of composite material and 0.1g of PAALi were thoroughly stirred in an aqueous solution to obtain a first negative electrode slurry. The first negative electrode slurry was coated onto a copper foil substrate and dried at 60°C to form a first coating with a thickness of 3μm.

[0077] A second negative electrode slurry was obtained by thoroughly mixing 0.49 g LiF and 0.1 g PAALi in an aqueous solution. This second negative electrode slurry was then coated onto the first coating layer and dried at 60°C to form a second coating layer with a thickness of 100 nm. This resulted in a negative electrode current collector with a dual-layer functional coating.

[0078] Battery manufacturing LiNi 0.8 Co 0.1 Mn 0.1 O2, solid electrolyte Li6PS5Cl, carbon fiber, and hydrogenated nitrile rubber were thoroughly mixed in a xylene solvent system at a mass ratio of 70:25:2:3. The mixture was then coated onto aluminum foil, dried, and cold-pressed to obtain a positive electrode sheet. This positive electrode sheet was then cut into circular pieces with a diameter of 10 mm. The areal capacity of this positive electrode sheet is 4 mAh / cm². 2 .

[0079] The negative electrode current collector is cut into a circular piece with a diameter of 10mm.

[0080] 50 mg of Li6PS5Cl electrolyte material was cold-pressed at 360 MPa to prepare an electrolyte membrane with a thickness of 300 μm and a diameter of 10 mm.

[0081] The positive electrode and negative current collector are placed on both ends of the electrolyte membrane in sequence and then pressed and sealed to obtain an all-solid-state lithium-ion battery.

[0082] All-solid-state lithium-ion batteries using different negative electrode current collectors were prepared based on the preparation method of Example 1. The specific structural composition of the negative electrode current collectors used in each battery example and comparative example is shown in Table 1. Among them, the negative electrode current collector of Comparative Example 1 did not have a second coating, the negative electrode current collector of Comparative Example 2 did not have a first coating, and the negative electrode current collector of Comparative Example 3 did not have a first coating or a second coating.

[0083] In the first coating of Comparative Example 4, Ag and Mo3C2T x No composite material was formed; instead, a first coating was formed by physical mixing followed by slurry preparation, coating, and drying. Specifically, 0.5g of Mo3C2T was used. x The mixture was ball-milled with 0.0635g Ag powder at 100rpm to obtain a mixed powder. 0.49g of the mixed powder and 0.1g of PAALi were thoroughly stirred in an aqueous solution to obtain a first negative electrode slurry. The first negative electrode slurry was coated onto a copper foil and dried at 60℃ to form a first coating with a thickness of 3μm.

[0084] Table 1. Structural composition of the negative electrode current collector used in different groups of embodiments and comparative examples.

[0085] The specific performance test methods for the all-solid-state lithium-ion batteries of each embodiment and comparative example are as follows: (1) Measure the battery capacity retention rate after 200 cycles at 25°C. At 25°C, the all-solid-state lithium-ion batteries assembled above are activated at a rate of 0.05C for 2 cycles within a working voltage range of 2.5V to 4.3V, and then charged and discharged. The charge and discharge rate is 1C / 1C (1C rated current density is 4mA / cm). 2 Record the discharge capacity of the battery in the first cycle after activation, which is the first cycle 1C discharge capacity C0. After 200 full charge and discharge cycles, record the discharge capacity C1 in the 200th cycle. Calculate the capacity retention rate (%) after 200 cycles = (C1 / C0) × 100%.

[0086] (2) Measurement of initial coulombic efficiency and critical current density at 25°C: At 25°C, the assembled all-solid-state lithium-ion battery was charged from a low current density of 0.1 mA / cm² within a working voltage range of 2.5V to 4.3V. 2 Start at 0.1 mA / cm 2 The charging current density is gradually increased, and three cycles are performed at each current density. The discharge current density is fixed at 0.1 mA / cm² per cycle. 2 Record the coulombic efficiency and overpotential changes for each charge-discharge cycle. The coulombic efficiency during the first charge-discharge cycle is called the initial coulombic efficiency. During multiple charge-discharge cycles, the current density at which the coulombic efficiency significantly decreases or the overpotential rapidly increases is considered the critical current density.

[0087] (3) Measure the rate performance of the battery at 25°C. At 25°C, the assembled all-solid-state lithium-ion battery was tested at a working voltage of 2.5~4.3V with a current density of 0.05C (1C rated current density is 4mA / cm). 2 Activate the battery at the specified rate for 2 cycles. Charge the solid-state battery in constant current / constant voltage mode at a constant rate of 0.33C; after resting for 5 minutes, discharge the battery to the lower limit of the operating cutoff voltage at a constant rate of 0.33C; repeat the above steps for three charge-discharge cycles, and record the discharge capacity C in the third cycle. 0.33 Charge the solid-state battery at a constant current and constant voltage (DCV) of 0.33C; after resting for 5 minutes, discharge the battery to the lower limit of the operating cutoff voltage at a constant current of 0.5C; repeat this charge-discharge cycle three times. Charge the solid-state battery at a constant current and constant voltage (DCV) of 0.33C; after resting for 5 minutes, discharge the battery to the lower limit of the operating cutoff voltage at a constant current of 1C; repeat this charge-discharge cycle three times. Charge the solid-state battery at a constant current and constant voltage (DCV) of 0.33C; after resting for 15 minutes, discharge the battery to the lower limit of the operating cutoff voltage at a constant current of 2C; repeat this charge-discharge cycle three times, and record the discharge capacity C2 in the third cycle. Calculate the fast-charging capacity retention rate (%) = (C2 / CV). 0.33 ) × 100%.

[0088] The test results of the all-solid-state lithium-ion batteries in each embodiment and comparative example are shown in Table 2.

[0089] Table 2. Performance test results of secondary lithium-ion batteries in different groups of examples and comparative examples.

[0090] Comparing Examples 1-16 with Comparative Examples 1-3, the importance of the double-layer coating is fully demonstrated. By setting a double-layer coating (Examples 1-16), a synergistic effect can be achieved, significantly improving the battery's initial coulombic efficiency, cycle stability, and rate performance, while suppressing the risk of internal short circuits and enhancing battery safety. Without a lithiophilic first coating on the negative electrode current collector (Comparative Example 2), lithium deposition points become more concentrated and random, forming larger and more destructive dendrites, and the entire negative electrode interface exhibits huge resistance, leading to a sharp decline in battery rate performance. Without a lithiophobic second coating on the negative electrode current collector (Comparative Example 1), as lithium continues to deposit, the volume expands dramatically, and the deposited lithium still grows in a three-dimensional manner, forming loose, dendritic lithium. Without both the first and second coatings on the negative electrode current collector (Comparative Example 3), during continuous charge and discharge, lithium deposition and extraction are irreversible, forming a large number of "dead lithium" cells that have lost electrical contact, leading to rapid consumption of active lithium and electrolyte, and a rapid decline in battery capacity.

[0091] Comparing Example 3 and Comparative Example 4, it is evident that the composite of MXene carbide and the first metal produces a synergistic effect. In Comparative Example 4, Ti3C2T... x The physical mixing with Ag has limited effect on lithium deposition. However, Example 3, by preparing a product with Ti3C2T... x Composite materials with Ag, incorporating the first metallic Ag into Ti3C2T x The layered structure significantly reduces the lithium nucleation energy barrier, promotes uniform lithium deposition, and effectively inhibits the formation and growth of lithium dendrites.

[0092] Comparing Examples 3, 8, 9, and 16-18, it can be seen that increasing the content of the first metal atom improves the uniformity of lithium deposition, increases the continuity of ion / electron transport channels, and makes the current density distribution more uniform. However, further increasing the content of the first metal atom, as in Example 8, may affect the two-dimensional ordered arrangement of the MXene carbide, thereby impacting battery performance. When the mass ratio of MXene carbide to the first metal is 40:1 to 60:1, excellent initial coulombic efficiency, cycle stability, and rate performance can be obtained.

[0093] Comparing Examples 3, 10, and 11, it can be seen that as the thickness of the first coating increases, a continuous lithiophilic surface can be formed, preventing lithium from preferentially nucleating at copper foil defects to form coarse grains or dendrites, thus ensuring battery performance. However, as the thickness of the first coating continues to increase, as in Example 11, it may lengthen the lateral diffusion path of lithium ions, reduce lithium deposition uniformity, and affect the current density distribution.

[0094] Examples 3, 14, and 15 demonstrate that increasing the thickness of the second coating can limit the longitudinal growth of lithium dendrites and reduce the risk of short circuits. However, further increases in the thickness of the second coating, such as in Example 15, can increase the lithium-ion migration barrier, potentially leading to increased polarization and affecting rate performance.

[0095] Comparing Examples 3, 12, and 13, it can be seen that the second coatings using different second compounds can all restrict the longitudinal growth of lithium dendrites and isolate the solid electrolyte layer from the first coating. Comparing Examples 1-4, it can be seen that the first coatings using different MXene carbides can all serve as a stable framework or confined space for lithium deposition. Comparing Examples 3, 5-7, it can be seen that the first coatings using different first metals can all guide the uniform nucleation and deposition of lithium ions on the current collector surface.

[0096] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of this disclosure (including the claims) is limited to these examples; within the framework of this disclosure, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the embodiments of this disclosure as described above, which are not provided in detail for the sake of brevity.

[0097] This disclosure is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A negative electrode current collector, characterized in that, The system comprises a base layer, a first coating, and a second coating, which are sequentially stacked. The first coating comprises a composite material having a first metal and an MXene carbide, and the second coating comprises a second compound. The first metal comprises at least one of silver, gold, tin, zinc, lead, or bismuth. The MXene carbide has the general formula M. n+1 C n T x M includes at least one of titanium, vanadium, niobium, molybdenum, tantalum, chromium, zirconium, hafnium, scandium, or tungsten, n=1~3, T x The first compound includes at least one of -OH, -O, or -F; the second compound includes at least one of aluminum oxide, magnesium oxide, lithium fluoride, magnesium fluoride, calcium fluoride, or boron nitride.

2. The negative electrode current collector according to claim 1, characterized in that, Based on the total mass of the first coating, the mass fraction of the composite material is greater than or equal to 90%.

3. The negative electrode current collector according to claim 1, characterized in that, The mass ratio of the MXene carbide to the first metal is from 1:1 to 100:

1.

4. The negative electrode current collector according to claim 3, characterized in that, The mass ratio of the MXene carbide to the first metal is 40:1 to 60:

1.

5. The negative electrode current collector according to claim 1, characterized in that, The MXene carbide has a layered structure, and at least a portion of the first metal is incorporated into the interior of the layered structure to form the composite material.

6. The negative electrode current collector according to claim 1, characterized in that, The thickness ratio of the first coating to the second coating is 1:1 to 100:1; and / or the thickness of the first coating is 500 nm to 5000 nm, and the thickness of the second coating is 50 nm to 1000 nm.

7. A method for preparing a negative electrode current collector, characterized in that, include: A first negative electrode slurry and a second negative electrode slurry are prepared, wherein the first negative electrode slurry comprises a composite material having a first metal and an MXene carbide, and the second negative electrode slurry comprises a second compound; the first metal comprises at least one selected from silver, gold, tin, zinc, lead, or bismuth; and the MXene carbide has the general formula M. n+1 C n T x M includes at least one of titanium, vanadium, niobium, molybdenum, tantalum, chromium, zirconium, hafnium, scandium, or tungsten, n=1~3, T x The first negative electrode slurry is coated on the substrate layer and dried to form a first coating; the second negative electrode slurry is coated on the side of the first coating away from the substrate layer and dried to form a second coating, thereby obtaining the negative electrode current collector.

8. The method for preparing the negative electrode current collector according to claim 7, characterized in that, The method for preparing the composite material includes: preparing a dispersion containing MXene carbide and a solution containing a first metal salt; adding the solution to the dispersion, adding a reducing agent to react, filtering and drying to obtain a composite material containing the first metal and MXene carbide.

9. The method for preparing the negative electrode current collector according to claim 8, characterized in that, The first metal salt includes at least one of silver nitrate, tetrachloroauric acid, stannous chloride, zinc sulfate, lead nitrate, or bismuth nitrate; and / or the concentration of the solution is from 0.01 mol / L to 0.1 mol / L; and / or the reducing agent includes at least one of sodium borohydride, ascorbic acid, sodium citrate, or hydrazine hydrate; and / or the molar ratio of the reducing agent to the first metal salt is from 3:1 to 20:

1.

10. An all-solid-state battery, characterized in that, include: A positive electrode, a negative current collector, and an electrolyte, wherein the negative current collector is the negative current collector as described in any one of claims 1-6.

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