Battery cell, method for producing the same, battery device, electric device, and energy storage device

Abstract

The application relates to the field of batteries, and provides a battery monomer, a preparation method of the battery monomer, a battery device, a power utilization device and an energy storage device. The preparation method of the battery monomer comprises the following steps: providing an electrode core assembly, wherein the electrode core assembly is formed by stacking or winding a positive electrode sheet, a diaphragm and a negative electrode sheet; providing a shell, and placing the electrode core assembly in the shell; providing an electrolyte, and injecting the electrolyte into the shell; and performing a formation step. The positive electrode sheet comprises a positive electrode active component, and the positive electrode active component comprises a modified MXene material. The modified MXene material comprises an MXene matrix and an Al2O3 / AlF3 gradient coating layer coated outside the MXene matrix. At least the electrochemical stability, the cycle life and the safety performance can be significantly improved on the basis of maintaining high conductivity of the material.

Description

Technical Field

[0001] This application relates to the field of batteries, and in particular to a battery cell and its preparation method, a battery device, an electrical device, and an energy storage device. Background Technology

[0002] With the accelerating global energy transition and the increasing demand for energy storage technologies, developing advanced energy storage devices with high energy density and long lifespan has become an important direction for technological development. While traditional lithium-ion batteries have achieved great success in consumer electronics and electric vehicles, improving their energy density is facing fundamental challenges at the material level.

[0003] Against this backdrop, breakthroughs in cathode materials, as core components determining battery energy density and operating voltage, are of great significance. Traditional cathode materials are primarily based on the redox reactions of transition metal oxides, through the interaction of Li... + Energy storage is achieved through insertion / extraction of materials, but the potential for capacity improvement is limited by the theoretical limits of transition metal valence state changes. Furthermore, to achieve higher energy density, cathode materials need to operate at higher voltages, which places more stringent demands on their electrochemical stability. Summary of the Invention

[0004] This application provides a battery cell and its preparation method, battery device, power consumption device and energy storage device, which at least helps to achieve high capacity of battery cells and is suitable for long-term energy storage fields, such as energy storage systems that can operate continuously for 4h to 8h at rated power.

[0005] In a first aspect, this application provides a method for preparing a battery cell, comprising:

[0006] A battery cell assembly is provided, the battery cell assembly being formed by stacking or winding positive electrode sheets, separators and negative electrode sheets;

[0007] A housing is provided to house the battery cell assembly within the housing;

[0008] Provide electrolyte and inject the electrolyte into the housing;

[0009] Perform the formation step;

[0010] The positive electrode includes a positive electrode active component, which includes a modified MXene material. The modified MXene material includes an MXene matrix and an Al2O3 / AlF3 gradient coating layer covering the MXene matrix.

[0011] Optionally, the general formula of the MXene matrix is ​​Ti3C2T. x T xThe matrix comprises at least one of -OH, -O, and -F, and has 5 to 50 layers, specifically 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50 layers, with an average lateral dimension of 0.5 μm to 10 μm, specifically 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, and 8 μm. The sizes are 5μm, 9μm, 9.5μm, and 10μm, wherein the molar fraction of the -F functional group is 20%~60%, specifically 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, and 60%; the molar fraction of the -OH functional group is 15%~50%, specifically 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%; and the molar fraction of the -O functional group is 10%~40%, specifically 10%, 15%, 20%, 25%, 30%, 35%, and 40%.

[0012] Optionally, the preparation method of the modified MXene material includes:

[0013] Preparation of MXene matrix materials;

[0014] The MXene matrix material is coated with an Al2O3 / AlF3 gradient to form an Al2O3 / AlF3 gradient coating layer.

[0015] Optionally, the preparation method of the MXene matrix material includes:

[0016] Ti3AlC2 powder was pretreated to remove moisture and organic impurities, and then reacted with an aqueous hydrofluoric acid solution to obtain Ti3C2T. x MXene;

[0017] The Ti3C2T x MXene was post-treated in a hydrogen fluoride vapor atmosphere to obtain the precursor;

[0018] The precursor is dispersed in a tetrabutylammonium aqueous solution of a first concentration, and preliminary intercalation is performed at a first temperature to obtain a first intercalation product;

[0019] The first intercalation product was further intercalated in a tetrabutylammonium aqueous solution of the second concentration at a second temperature to obtain the MXene matrix material;

[0020] The first concentration is less than the second concentration, and the first temperature is less than the second temperature.

[0021] Optionally, the hydrofluoric acid aqueous solution has a mass fraction of 30% to 50%, specifically 30%, 35%, 40%, 45%, or 50%.

[0022] Optionally, the first concentration is 0.2 mol / L to 0.3 mol / L, specifically 0.2 mol / L, 0.21 mol / L, 0.22 mol / L, 0.23 mol / L, 0.24 mol / L, 0.25 mol / L, 0.26 mol / L, 0.27 mol / L, 0.28 mol / L, 0.29 mol / L, or 0.3 mol / L, and the second concentration is 0.7 mol / L to 0.8 mol / L, specifically 0.7 mol / L, 0.71 mol / L, 0.72 mol / L, 0.73 mol / L, 0.74 mol / L, 0.75 mol / L, 0.76 mol / L, 0.77 mol / L, 0.78 mol / L, 0.79 mol / L, or 0.8 mol / L.

[0023] Optionally, the first temperature is 60℃~70℃, specifically 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, 66℃, 67℃, 68℃, 69℃, or 70℃, and the second temperature is 65℃~75℃, specifically 65℃, 66℃, 67℃, 68℃, 69℃, 70℃, 71℃, 72℃, 73℃, 74℃, or 75℃.

[0024] Optionally, the gradient wrapping method includes:

[0025] The MXene matrix material was atomically deposited using a first deposition solution at a third temperature to form an Al2O3 inner layer.

[0026] On the surface of the inner Al2O3 layer, atomic layer deposition is performed using a third deposition solution at a fourth temperature to form an AlF3 transition layer.

[0027] On the surface of the AlF3 transition layer, atomic layer deposition is performed using a second deposition solution at a fourth temperature to form an AlF3 outer layer;

[0028] The first deposition solution is a mixture of trimethylaluminum and water, the second deposition solution is a mixture of hydrogen fluoride-pyridine complex, and the third deposition solution is a mixture of the first deposition solution and the second deposition solution; the third temperature is greater than the fourth temperature.

[0029] Optionally, the third temperature is 100℃~120℃, specifically 100℃, 101℃, 103℃, 105℃, 108℃, 110℃, 112℃, 115℃, 117℃, or 120℃, and the fourth temperature is 80℃~100℃, specifically 80℃, 82℃, 85℃, 88℃, 90℃, 92℃, 95℃, 97℃, or 100℃.

[0030] Optionally, the thickness of the Al2O3 inner layer is 0.8nm~1.2nm, specifically 0.8nm, 0.9nm, 1.0nm, 1.1nm, or 1.2nm; the thickness of the transition layer is 0.8nm~1.0nm, specifically 0.8nm, 0.9nm, or 1.0nm; and the thickness of the AlF3 outer layer is 1.0nm~1.8nm, specifically 1.0nm, 1.1nm, 1.2nm, 1.3nm, 1.4nm, 1.5nm, 1.6nm, 1.7nm, or 1.8nm.

[0031] Optionally, the positive electrode active ingredient also includes Li2MnO3 as a synergistic additive.

[0032] Optionally, the average particle size of the Li2MnO3 synergistic additive is 10nm~20nm, specifically 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 17nm, or 18nm, and the specific surface area is 80m². 2 / g~150m 2 / g, specifically 80m 2 / g、90m 2 / g, 100m 2 / g、110m 2 / g, 120m 2 / g, 130m 2 / g, 140m 2 / g, 150m 2 / g.

[0033] Optionally, the preparation method of the Li2MnO3 synergistic additive includes:

[0034] Manganese sulfate and lithium hydroxide were dissolved in deionized water in stoichiometric ratio, and after co-precipitation under alkaline conditions, they were calcined at 500℃~600℃ to obtain the Li2MnO3 synergistic additive.

[0035] Secondly, this application provides a single battery cell, comprising:

[0036] A battery cell assembly, wherein the battery cell assembly is formed by stacking or winding a positive electrode sheet, a separator and a negative electrode sheet;

[0037] The housing, in which the battery cell assembly is located;

[0038] An electrolyte is provided, located within the housing, and the battery cell assembly is immersed in the electrolyte.

[0039] The positive electrode includes a positive electrode active component, which includes a modified MXene material. The modified MXene material includes an MXene matrix and an Al2O3 / AlF3 gradient coating layer covering the MXene matrix.

[0040] Thirdly, this application provides a battery device, including a battery cell obtained by the method described above for preparing a battery cell, or a battery cell as described above, wherein the battery device includes one or more of a battery module, a battery pack, and an energy storage battery.

[0041] Fourthly, this application provides an electrical device, which includes a battery device as described above, the battery device being used to provide electrical energy.

[0042] Fifthly, this application provides an energy storage device, which includes a battery device as described above, the battery device being used to store electrical energy.

[0043] The energy storage device includes a battery pack, which includes multiple batteries, an energy management system (EMS), a battery management system (BMS), and an energy storage converter (PCS). The electrical devices include vehicles, household appliances, electric motors, medical equipment, scientific instruments, and power grids.

[0044] The technical solution provided in this application has at least the following advantages:

[0045] Based on the principles of two-dimensional materials electrochemistry and interface engineering, this application proposes a systematic engineering design scheme for anion-intercalated MXene cathode materials. The core of this scheme lies in achieving precise control of the electrode / electrolyte interface through multi-level structural design and functional synergy, thereby constructing a high-voltage cathode material system with excellent comprehensive performance.

[0046] This application adopts a design philosophy of "prioritizing structural stability and enhancing functional synergy." Targeting the structural evolution of MXene materials during electrochemical cycling, precise interlayer spacing control and dynamic stability management ensure the material maintains structural integrity during long-term cycling. Through the synergistic design of multifunctional components, each component not only fulfills its own function but also forms an organic functional complementarity with other components, achieving overall optimization of system performance.

[0047] The implementation path of the technical solution includes the synergistic integration of three key technical modules: the interlayer engineering module optimizes the surface properties of MXene through HF vapor treatment and achieves precise control of the interlayer spacing by using stepwise tetrabutylammonium intercalation, providing a suitable structural basis for anion intercalation; the interface engineering module adopts the gradient functional design concept to construct an Al2O3 / AlF3 composite coating layer, with the inner layer providing chemical stability and the outer layer providing ionic conductivity, achieving optimized configuration of functions through component gradient; the synergistic enhancement module introduces Li2MnO3 nanoparticles as a multifunctional additive, taking into account both lithium source compensation and interface stability enhancement, forming a synergistic effect with the MXene matrix.

[0048] Through the systematic integration of the aforementioned technical approaches, this application expands upon traditional energy storage mechanisms and resolves key technological bottlenecks. Compared to the single-point breakthrough approach of existing technologies, the systematic design of this application significantly improves electrochemical stability, cycle life, and safety performance while maintaining the high conductivity of materials, providing a complete technical solution for the engineering application of high-voltage cathode materials. It also facilitates the realization of high-capacity battery cells, making it suitable for long-term energy storage applications, such as energy storage systems that can operate continuously for 4 to 8 hours at rated power. Attached Figure Description

[0049] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the drawings in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this application or in the conventional art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 The flowchart corresponds to the method for preparing a single battery cell provided in the embodiments of this application. Detailed Implementation

[0051] As can be seen from the background technology, the existing technologies used to solve the stability problem of high-voltage cathode materials mainly include the following representative solutions:

[0052] Traditional cathode material surface coating technology uses oxide materials such as Al2O3, TiO2, and ZrO2 to form a protective layer on the surface of cathode particles through sol-gel methods or atomic layer deposition. The basic principle of this technology is to utilize the chemical inertness and ion selectivity of oxides to suppress direct contact between the cathode material and the electrolyte, reducing interfacial side reactions under high voltage. Typical coating thicknesses range from 2 nm to 10 nm, and the selection of coating materials primarily considers their electrochemical stability and lithium-ion conductivity.

[0053] MXenes, as a new class of two-dimensional transition metal carbides and nitrides, possess unique properties such as excellent conductivity, rich surface chemistry, and tunable interlayer structure, offering new possibilities for breaking through traditional energy storage mechanisms. However, current research on MXenes mainly focuses on anode applications, while their energy storage mechanisms and engineering applications as cathode materials are still in the exploratory stage. In particular, key technical issues such as how to achieve long-term stable operation of MXene materials under high-voltage environments, how to construct effective ion transport channels, and how to solve the problem of low initial efficiency have become significant bottlenecks restricting their practical application.

[0054] Based on the aforementioned technological needs and challenges, exploring MXene cathode material systems based on novel energy storage mechanisms is of significant scientific importance and application value for promoting the development of next-generation high-performance energy storage devices.

[0055] Interlayer spacing modulation technology for MXene materials is mainly achieved through intercalation agent treatment. Commonly used intercalation agents include organic molecules and ionic compounds. The intercalation process usually takes place in solution, where the intercalation agent enters the MXene interlayer through van der Waals forces or electrostatic interactions, expanding the interlayer spacing from the original approximately 1.0 nm to 1.2 nm to varying degrees. Intercalated MXenes exhibit a larger specific surface area and more active sites.

[0056] Dual-ion battery technology operates based on the synergistic storage mechanism of anions and cations. During charging, anions are embedded into the layered structure of the positive electrode material, while cations are embedded into the negative electrode material; the process is reversed during discharge. Theoretically, this system can achieve high operating voltages, but it places high demands on the structural stability of the electrode materials and the electrochemical window of the electrolyte.

[0057] Lithium source additive technology uses pre-lithiated materials to compensate for irreversible capacity loss during the first charge. These additives decompose and release Li during the first charge. + Combined with the formation process of the SEI film on the negative electrode, it improves the initial coulombic efficiency of the battery. The selection of additives needs to consider their decomposition potential, the degree of side reactions, and compatibility with other components.

[0058] Existing technologies still have significant limitations in solving key technical problems related to high-voltage cathode materials, mainly in the following aspects:

[0059] First, while traditional surface coating technology can improve the electrochemical stability of cathode materials to some extent, it faces a fundamental contradiction between coating thickness and ion conductivity. If the coating is too thin, it is difficult to effectively isolate the electrode from direct contact with the electrolyte, failing to adequately suppress oxidative decomposition reactions under high voltage; conversely, if the coating is too thick, it significantly increases ion transport impedance, leading to deterioration in rate performance and low-temperature performance. Single-component coating materials cannot simultaneously meet the dual requirements of chemical stability and ion conductivity, and traditional uniform coating structures cannot achieve optimized functional configuration.

[0060] Secondly, existing MXene interlayer spacing control technologies primarily focus on static interlayer spacing expansion, lacking a systematic consideration of structural stability during dynamic cycling. While intercalating agents can expand the interlayer spacing, they are prone to irreversible structural changes during electrochemical cycling, leading to interlayer collapse, loss of active sites, and disruption of the conductive network. Particularly under high-voltage conditions, intercalating agents may undergo oxidative decomposition, further exacerbating structural instability. Current technologies lack a deep understanding of the structural evolution during cycling and effective control methods.

[0061] Furthermore, although there have been recent reports of conceptual studies on MXene materials for dual-ion energy storage, existing research is mostly at the basic verification stage, lacking systematic engineering design and optimization. In particular, how to achieve efficient and reversible anion insertion while maintaining the high conductivity of MXene, how to balance key performance indicators such as capacity, rate performance, and cycle life, and how to achieve long-term structural stability control remain unsolved technical challenges.

[0062] Furthermore, existing lithium source additive technologies are primarily designed for traditional lithium-ion battery systems, and their applicability and mechanism of action in dual-ion batteries remain unclear. Simple physical mixing methods are insufficient to achieve deep synergy between additives and the host material, and technical challenges remain regarding additive dispersion uniformity, reactivity, and control of side reactions. Particularly in novel electrode material systems such as MXene, the mechanism of action of traditional additives may change, requiring re-evaluation and optimization.

[0063] Finally, existing technologies often employ single strategies to address specific problems, lacking a systematic and collaborative design approach. For example, surface coating primarily focuses on stability, interlayer modulation mainly on capacity, and lithium source compensation primarily on initial efficiency. These techniques lack organic integration and functional complementarity. In complex electrochemical environments, the effectiveness of a single technique is often limited; a synergistic effect of multiple techniques is required to achieve a significant improvement in overall performance.

[0064] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0065] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0066] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0067] In the description of the embodiments of this application, when a component "includes" another component, other components are not excluded unless otherwise stated, and other components may be further included. Furthermore, when a component such as a layer, film, region, or plate is referred to as being "on / located" on another component, it can be "directly on" the other component (i.e., located on the surface of the other component with no other components between them), or another component may be present therein. Moreover, when a component such as a layer, film, region, or plate is "directly located" on another component, or when a component such as a layer, film, region, or plate is located on the surface of another component, it indicates that no other components are located therein.

[0068] The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "part" is also intended to include the plural form unless the context clearly indicates otherwise. Components include layers, films, regions, or plates, etc.

[0069] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0070] In a first aspect, this application provides a method for preparing a battery cell, comprising:

[0071] S1. Provide a battery cell assembly, wherein the battery cell assembly is formed by stacking or winding a positive electrode sheet, a separator and a negative electrode sheet;

[0072] S2. Provide a housing and place the battery cell assembly inside the housing;

[0073] S3. Provide electrolyte and inject the electrolyte into the casing;

[0074] S4. Perform the formation step;

[0075] The positive electrode includes a positive electrode active component, which includes a modified MXene material. The modified MXene material includes an MXene matrix and an Al2O3 / AlF3 gradient coating layer covering the MXene matrix.

[0076] Based on the principles of two-dimensional materials electrochemistry and interface engineering, this application proposes a systematic engineering design scheme for anion-intercalated MXene cathode materials. The core of this scheme lies in achieving precise control of the electrode / electrolyte interface through multi-level structural design and functional synergy, thereby constructing a high-voltage cathode material system with excellent comprehensive performance.

[0077] This application adopts a design philosophy of "prioritizing structural stability and enhancing functional synergy." Targeting the structural evolution of MXene materials during electrochemical cycling, precise interlayer spacing control and dynamic stability management ensure the material maintains structural integrity during long-term cycling. Through the synergistic design of multifunctional components, each component not only fulfills its own function but also forms an organic functional complementarity with other components, achieving overall optimization of system performance.

[0078] The implementation path of the technical solution includes the synergistic integration of three key technical modules: the interlayer engineering module optimizes the surface properties of MXene through HF vapor treatment and achieves precise control of the interlayer spacing by using stepwise tetrabutylammonium intercalation, providing a suitable structural basis for anion intercalation; the interface engineering module adopts the gradient functional design concept to construct an Al2O3 / AlF3 composite coating layer, with the inner layer providing chemical stability and the outer layer providing ionic conductivity, achieving optimized configuration of functions through component gradient; the synergistic enhancement module introduces Li2MnO3 nanoparticles as a multifunctional additive, taking into account both lithium source compensation and interface stability enhancement, forming a synergistic effect with the MXene matrix.

[0079] Through the systematic integration of the aforementioned technical approaches, this application expands upon traditional energy storage mechanisms and resolves key technological bottlenecks. Compared to the single-point breakthrough approach of existing technologies, the systematic design of this application significantly improves electrochemical stability, cycle life, and safety performance while maintaining the high conductivity of materials, providing a complete technical solution for the engineering application of high-voltage cathode materials. It also facilitates the realization of high-capacity battery cells, making it suitable for long-term energy storage applications, such as energy storage systems that can operate continuously for 4 to 8 hours at rated power.

[0080] Optionally, the general formula of the MXene matrix is ​​Ti3C2T. x T x The MXene matrix comprises at least one of -OH, -O, and -F, and has 5 to 50 layers with an average lateral dimension of 0.5 μm to 10 μm. The molar fraction of -F functional groups is 20% to 60%, the molar fraction of -OH functional groups is 15% to 50%, and the molar fraction of -O functional groups is 10% to 40%.

[0081] Optionally, the preparation method of the modified MXene material includes:

[0082] Preparation of MXene matrix materials;

[0083] The MXene matrix material is coated with an Al2O3 / AlF3 gradient to form an Al2O3 / AlF3 gradient coating layer.

[0084] Optionally, the thickness of the Al2O3 / AlF3 gradient coating layer is 2nm~3nm.

[0085] Optionally, the preparation method of the MXene matrix material includes:

[0086] Ti3AlC2 powder was pretreated to remove moisture and organic impurities, and then reacted with an aqueous hydrofluoric acid solution to obtain Ti3C2T. x MXene;

[0087] The Ti3C2T x MXene was post-treated in a hydrogen fluoride vapor atmosphere to obtain the precursor;

[0088] The precursor is dispersed in a tetrabutylammonium aqueous solution of a first concentration, and preliminary intercalation is performed at a first temperature to obtain a first intercalation product;

[0089] The first intercalation product was further intercalated in a tetrabutylammonium aqueous solution of the second concentration at a second temperature to obtain the MXene matrix material;

[0090] The first concentration is less than the second concentration, and the first temperature is less than the second temperature.

[0091] After intercalation, the interlayer spacing of MXene increased from the initial 1.0nm~1.2nm to 1.8nm~2.2nm, providing a structural basis for the intercalation of large-sized anions.

[0092] Optionally, the hydrogen fluoride vapor treatment conditions are: temperature 35°C~45°C, time 2h~3h, and relative humidity controlled at 40%~70%. This treatment helps optimize the distribution of surface functional groups and remove residual Al. 3+ Ions and aluminum fluorine compounds.

[0093] Optionally, the hydrofluoric acid aqueous solution has a mass fraction of 30% to 50%.

[0094] Optionally, the first concentration is 0.2 mol / L to 0.3 mol / L, and the second concentration is 0.7 mol / L to 0.8 mol / L.

[0095] Optionally, the first temperature is 60℃~70℃, and the second temperature is 65℃~75℃.

[0096] The selection of the first concentration and the first temperature ensures the uniform dispersion of the intercalating agent, while the selection of the second concentration and the second temperature enables the full expansion of the interlayer spacing.

[0097] Optionally, the gradient wrapping method includes:

[0098] The MXene matrix material was atomically deposited using the first deposition solution at the third temperature to form an Al2O3 inner layer, with the thickness increasing by approximately 0.1 nm per ALD cycle.

[0099] On the surface of the inner Al2O3 layer, atomic layer deposition is performed using a third deposition solution at a fourth temperature to form an AlF3 transition layer.

[0100] On the surface of the AlF3 transition layer, atomic layer deposition is performed using a second deposition solution at a fourth temperature to form an AlF3 outer layer, with the thickness increasing by approximately 0.08 nm to 0.12 nm per cycle.

[0101] The first deposition solution is a mixture of trimethylaluminum and water, the second deposition solution is a mixture of hydrogen fluoride-pyridine complex, and the third deposition solution is a mixture of the first deposition solution and the second deposition solution; the third temperature is greater than the fourth temperature.

[0102] The deposition process is carried out in a low-humidity environment, with the relative humidity controlled below 5% to avoid oxidative degradation of MXene.

[0103] Optionally, the third temperature is 100℃~120℃, and the fourth temperature is 80℃~100℃.

[0104] Optionally, the thickness of the Al2O3 inner layer is 0.8nm~1.2nm, the thickness of the transition layer is 0.8nm~1.0nm, and the thickness of the AlF3 outer layer is 1.0nm~1.8nm.

[0105] Optionally, from the MXene surface outwards, the molar ratio of Al2O3 to AlF3 gradually changes from 1:1 to 1:3, achieving a continuous gradient transition of components by adjusting the ALD cycling parameters. This gradient design allows the inner Al2O3 layer to provide chemical stability and mechanical support, while the outer AlF3 layer provides ionic conductivity and electrolyte compatibility.

[0106] More specifically, the preparation method of modified MXene materials includes the following steps:

[0107] Step 1: Pretreatment of MAX phase precursor

[0108] Ti3AlC2 powder was heated in a muffle furnace at 400°C for 2 hours to remove surface-adsorbed moisture and organic impurities. After cooling to room temperature, it was passed through a 200-mesh sieve to remove large particles, yielding pretreated Ti3AlC2 powder.

[0109] Step 2: Selective etching to prepare MXene

[0110] In a polytetrafluoroethylene reactor, pretreated Ti3AlC2 powder was slowly added to a 40% HF aqueous solution, and the mixture was magnetically stirred at room temperature for 24 hours. The reaction progress was observed periodically during the process; changes in solution color indicated that the reaction was proceeding normally.

[0111] After the reaction was complete, the supernatant was repeatedly washed with deionized water until the pH reached 6-7, and the product was collected by centrifugation. The obtained Ti3C2T x MXene was dried in a vacuum drying oven at 60°C for 12 hours.

[0112] Step 3: HF Steam Post-treatment

[0113] The initially prepared Ti3C2T x MXene was placed in a sealed polytetrafluoroethylene container with an appropriate amount of dilute HF solution at the bottom. The container was then placed in a constant temperature oven at (40±2)°C for 3 hours to further optimize the functional group distribution on the MXene surface using HF vapor.

[0114] After treatment, nitrogen gas is used to purge the residual HF vapor, and then deionized water is used to gently wash away the HF molecules adsorbed on the surface, avoiding excessive washing that may affect the treatment effect.

[0115] Step 4: Stepwise tetrabutylammonium intercalation treatment

[0116] Step 1: Treat Ti3C2T with HF vapor x MXene was dispersed in a low-concentration TBAOH aqueous solution (0.25 mol / L) and magnetically stirred at 65°C for 10 h to ensure uniform dispersion and initial intercalation of the intercalating agent.

[0117] Step 2: Based on Step 1, adjust the TBAOH concentration to 0.75 mol / L and continue treatment at 70°C for 12 hours to fully expand the interlayer spacing. After intercalation, the interlayer spacing increased from approximately 1.1 nm to approximately 2.0 nm.

[0118] After intercalation, excess TBAOH was removed by centrifugation and washing, followed by alternating washing with ethanol and deionized water, and finally drying in a vacuum drying oven at 60°C for 10 hours.

[0119] Step 5: ALD equipment pretreatment

[0120] Intercalated Ti3C2T x The material was loaded into the ALD reaction chamber and pretreated under vacuum at 110°C and low humidity for 30 minutes to remove adsorbed moisture and organic matter from the surface. The humidity in the reaction chamber was controlled below 5% to ensure a suitable deposition environment.

[0121] Step 6: Al2O3 inner layer deposition

[0122] Trimethylaluminum and H2O were used as precursors for Al2O3 deposition at 110°C. A single ALD cycle consisted of a standard sequence of trimethylaluminum pulse, nitrogen purging, H2O pulse, and nitrogen purging. The Al2O3 layer thickness was controlled to be 0.8 nm–1.2 nm by adjusting the number of cycles.

[0123] Step 7: Construction of Gradient Transition Layer

[0124] A gradient transition layer was formed by gradually introducing AlF3 components onto an Al2O3 base. Trimethylaluminum and HF-pyridine complex were used as precursors, and the deposition temperature was lowered to 90°C. By adjusting the cycling ratio of different precursors, a gradient transition of the Al2O3:AlF3 molar ratio from 1:1 to 1:3 was achieved from the inside out. The thickness of the gradient transition layer was controlled between 0.8 nm and 1.0 nm.

[0125] Step 8: AlF3 outer layer deposition

[0126] Based on the gradient transition layer, an AlF3 outer layer was deposited using pure trimethylaluminum / HF-pyridine cyclic deposition. The deposition temperature was 90°C, and the number of cycles was controlled to form an AlF3 outer layer with a thickness of 1.0 nm to 1.8 nm.

[0127] Optionally, the positive electrode active ingredient also includes Li2MnO3 as a synergistic additive.

[0128] The introduction of Li2MnO3 has a dual function: during the first charge, it decomposes and releases Li in the potential range of 4.5V~4.8V. + This process compensates for irreversible lithium loss during SEI film formation and improves initial coulombic efficiency. The Mn-based active sites formed after decomposition synergistically interact with the MXene matrix, enhancing structural stability under high voltage. To control side reactions under high voltage, the content and particle size of Li2MnO3 need to be precisely controlled to avoid excessive oxygen release and metal ion dissolution.

[0129] Optionally, the Li2MnO3 synergistic additive has an average particle size of 10nm~20nm and a specific surface area of ​​80m². 2 / g~150m 2 / g.

[0130] Optionally, the content of the Li2MnO3 synergistic additive is 5wt%~10wt%, which is the content of the Li2MnO3 synergistic additive in the positive electrode active ingredient.

[0131] Optionally, the preparation method of the Li2MnO3 synergistic additive includes:

[0132] Manganese sulfate and lithium hydroxide were dissolved in deionized water in stoichiometric ratio, and after co-precipitation under alkaline conditions, they were calcined at 500℃~600℃ to obtain the Li2MnO3 synergistic additive.

[0133] More specifically, the preparation and composite process of Li2MnO3 includes:

[0134] Step 9: Preparation of Li2MnO3 nanoparticles

[0135] Li₂MnO₃ nanoparticles were prepared by a co-precipitation method. MnSO₄·H₂O and LiOH·H₂O were dissolved in deionized water at a molar ratio of 2:1. The Li salt solution was then added dropwise to the Mn salt solution under vigorous stirring, with the pH value controlled between 11 and 12.

[0136] During the reaction, a precipitate gradually formed, and stirring was continued for 2 hours to ensure complete reaction. The precipitate was filtered and washed until neutral, dried in an 80°C oven for 8 hours, and then calcined in a muffle furnace at 550°C for 8 hours at a heating rate of 2°C / min to obtain Li₂MnO₃ nanoparticles.

[0137] Step 10: Preparation of composite materials

[0138] The coated Ti3C2Tx The material and Li2MnO3 nanoparticles were mechanically combined in a ball mill jar at a weight ratio of (90~95):(5~10). The ball milling conditions were: 200 rpm, 2 h, and a ball-to-material ratio of 10:1. By controlling the ball milling parameters, uniform dispersion of Li2MnO3 was ensured, and damage to the MXene sheets caused by over-milling was avoided.

[0139] The ball-milled composite material was treated in a vacuum drying oven at 120°C for 4 hours to remove the moisture introduced during the ball milling process, resulting in the final dual-ion co-intercalated MXene cathode material.

[0140] When assembling the battery, conventional lithium-ion battery assembly processes can be used, and the specific steps are as follows:

[0141] A positive electrode slurry is prepared by mixing the positive active material with a conductive agent and a binder in a certain proportion. This slurry is then coated onto an aluminum foil current collector and processed through drying and compaction to form the positive electrode sheet. The negative electrode sheet uses graphite as the negative electrode material and is coated onto a copper foil current collector.

[0142] The positive electrode, separator, and negative electrode are stacked or wound in sequence to form a battery cell, which is then installed in a battery casing. Electrolyte is injected in a glove box environment, and after encapsulation, a formation process is performed. The formation conditions are: constant current charging at 0.1C to the upper limit voltage, then constant voltage charging to a current of 0.05C, and then constant current discharging at 0.1C to the lower limit voltage. This process is repeated several times to complete the initialization.

[0143] Secondly, this application provides a single battery cell, comprising:

[0144] A battery cell assembly, wherein the battery cell assembly is formed by stacking or winding a positive electrode sheet, a separator and a negative electrode sheet;

[0145] The housing, in which the battery cell assembly is located;

[0146] An electrolyte is provided, located within the housing, and the battery cell assembly is immersed in the electrolyte.

[0147] The positive electrode includes a positive electrode active component, which includes a modified MXene material. The modified MXene material includes an MXene matrix and an Al2O3 / AlF3 gradient coating layer covering the MXene matrix.

[0148] Optionally, the electrolyte is a high-voltage dual-ion battery electrolyte system, including but not limited to: a carbonate electrolyte system based on high-concentration LiPF6, with a lithium salt concentration of not less than 2 mol / L, supporting PF6. - Anion intercalation; electrolyte systems based on ionic liquids, such as EMIm-TFSI or PYR13-TFSI, support TFSI.- Intercalation of anions.

[0149] The selection of the electrolyte needs to consider its compatibility with the AlF3 coating layer and its impact on the decomposition behavior of Li2MnO3. The selected electrolyte system has a wide electrochemical window (>5V), can withstand high-voltage operating environments, and maintains good interfacial stability with the MXene surface-modified layer.

[0150] Optionally, the positive electrode sheet is prepared using a slurry coating process. The positive electrode slurry composition includes two formulation routes:

[0151] Formulation Route A: 92wt%~95wt% modified MXene material, 2wt%~3wt% conductive agent, 3wt%~5wt% PVDF binder, NMP solvent;

[0152] Formulation route B: 92wt%~95wt% modified MXene material, 2wt%~3wt% conductive agent, 3wt%~5wt% aqueous binder (PAA or CMC), and deionized water as solvent.

[0153] In the slurry preparation process, the modified MXene material and conductive agent are first dispersed uniformly in the corresponding solvent for 2-4 hours; then, the binder is added and mixing continues for 1-2 hours to ensure the uniformity and stability of the slurry. The coated electrode sheets are dried at 80°C-120°C and compacted under a pressure of 10-20 MPa, with the compaction density controlled at 2.0 g / cm³. 3 ~3.0g / cm 3 .

[0154] The anode material can be selected from various materials such as graphite, hard carbon, and soft carbon. For example, graphite anode can be used to achieve good electrochemical matching. The ratio of positive to negative electrode active capacity is controlled at more than 3:1 to ensure the electrochemical balance of the system.

[0155] The diaphragm can be made of polypropylene, polyethylene, ceramic-coated membranes, etc., such as a PP / PE / PP three-layer composite diaphragm with a thickness of 16μm~25μm.

[0156] Thirdly, this application provides a battery device, including a battery cell obtained by the method described above for preparing a battery cell, or a battery cell as described above, wherein the battery device includes one or more of a battery module, a battery pack, and an energy storage battery.

[0157] Fourthly, this application provides an electrical device, which includes a battery device as described above, the battery device being used to provide electrical energy.

[0158] Fifthly, this application provides an energy storage device, which includes a battery device as described above, the battery device being used to store electrical energy.

[0159] The energy storage device includes a battery pack, which includes multiple batteries, an energy management system (EMS), a battery management system (BMS), and an energy storage converter (PCS). The electrical devices include vehicles, household appliances, electric motors, medical equipment, scientific instruments, and power grids.

[0160] This application achieves long-term stability of the material structure through precise control of process parameters. Key control indicators include: interlayer spacing change rate not exceeding 15% during cycling, surface coating integrity retention rate not less than 80%, and MXene sheet peeling rate not exceeding 5%.

[0161] Structural stability is achieved through the following technical means: optimizing HF processing parameters to avoid structural defects caused by excessive etching; adopting a step-by-step intercalation process to prevent structural instability caused by excessive expansion of interlayer spacing; adopting a gradient coating design to reduce interfacial stress between the coating layer and the substrate; and controlling the particle size and dispersibility of Li2MnO3 to avoid local stress concentration.

[0162] This application also represents a breakthrough in systematic engineering design concepts: current technologies often employ single strategies to solve specific problems, while this application, based on the principle of "prioritizing structural stability and enhancing functional synergy," achieves a collaborative solution to multiple technical challenges through the systematic integration of three major technical modules: inter-layer engineering, interface engineering, and synergy enhancement. This avoids performance balance issues that may arise from single-point optimization. Specifically, this is reflected in the following:

[0163] (1) Innovation in quantitative structural stability control: Unlike existing technologies that lack a systematic understanding of the evolution of MXene structures, this application establishes for the first time a quantitative control standard of ≤15% interlayer spacing change rate during cycling. Through precise process parameter design, the structural stability can be controlled and adjusted, laying a technical foundation for the engineering application of MXene-based electrode materials.

[0164] (2) Breakthrough in the design of gradient functional coating layer: Traditional surface coating uses a single component for uniform coating, which presents a contradiction between stability and conductivity. This application innovatively proposes an Al2O3 / AlF3 gradient coating design, in which the inner Al2O3 layer provides chemical stability and the outer AlF3 layer provides ionic conductivity. The optimized configuration of functions is achieved through the component gradient (1:1~1:3), which breaks through the performance bottleneck of traditional coating technology.

[0165] (3) Technological optimization of stepwise intercalation process: Existing intercalation technologies mostly adopt single-step processing, which can easily lead to uneven intercalation or structural damage. This application adopts a stepwise tetrabutylammonium intercalation process, which achieves precise control of interlayer spacing in the range of 1.8nm~2.2nm through a combination of low-concentration pretreatment and high-concentration deep treatment, ensuring intercalation uniformity and structural integrity.

[0166] (4) Mechanism innovation of multifunctional synergistic additives: Existing lithium source additives are mainly designed for traditional lithium-ion batteries. This application introduces Li2MnO3 into the dual-ion battery system. Through precise control of particle size (10nm~20nm) and content (5wt%~10wt%), the dual functions of lithium source compensation and interface stability enhancement are achieved. At the same time, the risk of side reactions under high voltage is controlled through process optimization.

[0167] (5) Synergistic realization of high conductivity and high stability: Traditional cathode materials face the trade-off between conductivity and stability. This application utilizes the intrinsic high conductivity of MXene and significantly improves stability while maintaining conductivity through surface modification, thus achieving synergistic optimization of high energy density and long cycle life.

[0168] (6) Design advantages of adaptability to multiple electrolyte systems: Existing dual-ion battery cathode materials are usually designed for specific electrolyte systems. This application achieves good adaptability to high-concentration carbonate systems and ionic liquid systems through reasonable interface design, which improves the versatility and application flexibility of the technical solution.

[0169] (7) Precise control strategy of process parameters: This application establishes a complete process parameter control system from HF steam treatment, step intercalation, gradient ALD coating to composite material preparation. Each process step has a clear range of parameters such as temperature, time, and concentration, which ensures the reproducibility and industrial feasibility of the technical solution.

[0170] To verify the technical feasibility and comprehensive electrochemical performance advantages of the proposed dual-ion co-intercalated layered modified MXene cathode material system, this application designed a series of examples and comparative examples to systematically explore the effects of key technical elements such as precise control of interlayer spacing, Al2O3 / AlF3 gradient functional coating layer design, Li2MnO3 nanoparticle synergistic additive, and stepwise tetrabutylammonium intercalation process on the first charge-discharge performance, cycle stability, rate performance, interfacial impedance, and temperature adaptability of the cathode material. The following details the material selection, cathode material preparation, battery assembly, and performance testing methods.

[0171] The experimental design followed the principle of single-factor variable control and was divided into three levels: the core innovation verification group (Example 1 and Comparative Examples 1 to 6) clarified the independent contribution and necessity of each innovation by peeling away key technical features one by one; the process window verification group (Examples 2 to 9) determined the effective process range of each parameter by systematically adjusting parameters such as interlayer spacing, coating thickness, Li2MnO3 content and gradient transition mode; and the application expansion verification group (Examples 10 to 12) verified the adaptability and versatility of the technical solution under different electrolyte systems, binder routes and electrode formulations.

[0172] The materials used in the following embodiments and comparative examples are as follows:

[0173] The MXene precursor material was Ti3AlC2MAX phase powder (particle size not greater than 38 μm, purity not less than 98%), and the selective etching was performed using 40 wt% hydrofluoric acid (HF) aqueous solution of analytical grade. Interlayer spacing was controlled using tetrabutylammonium hydroxide (TBAOH) aqueous solution, with the concentration adjusted within the range of 0.25 mol / L to 1.0 mol / L according to the experimental design.

[0174] The materials used to prepare the gradient coating layers include: the Al2O3 layer precursor uses trimethylaluminum (TMA) and deionized water; the AlF3 layer precursor uses trimethylaluminum and HF-pyridine complex. All ALD precursors have a purity of at least 99%.

[0175] The Li2MnO3 nanoparticles were prepared using manganese sulfate monohydrate (MnSO4·H2O, analytical grade) and lithium hydroxide monohydrate (LiOH·H2O, battery grade, purity not less than 99%).

[0176] The positive electrode slurry preparation materials include: conductive agent using conductive carbon black Super P (specific surface area 60m²). 2 / g~70m 2 / g); the PVDF binder route uses polyvinylidene fluoride (PVDF, number average molecular weight approximately 1 million), and the solvent is N-methyl-2-pyrrolidone (NMP, water content less than 50ppm); the water-based binder route uses polyacrylic acid (PAA, number average molecular weight approximately 450,000), and the solvent is deionized water.

[0177] The negative electrode uses artificial graphite negative electrode material (capacity not less than 350mAh / g), with an active material content of 96wt% and a binder CMC / SBR composite system content of 4wt%, coated on a copper foil current collector with a thickness of 8 micrometers. The separator uses a PP / PE / PP three-layer composite separator with a thickness of 20μm.

[0178] Two electrolyte systems are used: the carbonate system is 2.5 mol / L LiPF6 dissolved in a mixed solvent of ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate (EC / DMC / EMC, volume ratio 1:1:1); the ionic liquid system is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt (EMIm-TFSI, purity not less than 99.5%), combined with 0.5 mol / L LiTFSI lithium salt.

[0179] All the chemical reagents mentioned above are analytical grade or battery-grade materials, and are commercially available. All operations involving water- and oxygen-sensitive materials were performed in an argon-atmospheric glove box, where the water and oxygen content was controlled to be below 0.1 ppm.

[0180] Preparation of MXene cathode material:

[0181] Ti3C2T x The MXene matrix was prepared according to the aforementioned process flow. Ti3AlC2 powder was pretreated in a muffle furnace at 400℃ for 2 hours, cooled, and then passed through a 200-mesh sieve. In a polytetrafluoroethylene reactor, the pretreated powder was slowly added to a 40wt% HF aqueous solution, and the reaction was carried out with magnetic stirring at room temperature for 24 hours. After the reaction, the supernatant was repeatedly washed with deionized water until the pH reached 6-7. The product was collected by centrifugation and dried in a vacuum drying oven at 60℃ for 12 hours to obtain the initial Ti3C2T. x MXene.

[0182] HF steam post-treatment will be applied to Ti3C2T x MXene was placed in a sealed polytetrafluoroethylene container with a suitable amount of dilute HF solution at the bottom, and treated in a constant temperature oven at (40±2)℃ for 3 hours to optimize the surface functional group distribution using HF vapor. After treatment, residual HF vapor was removed by purging with nitrogen.

[0183] The stepwise TBAOH intercalation treatment was carried out according to the design parameters of each embodiment and comparative example. Taking Example 1 as an example, the first step was to disperse MXene after HF vapor treatment in a 0.25 mol / L TBAOH aqueous solution and magnetically stir at 65°C for 10 h to complete the initial intercalation; the second step was to adjust the TBAOH concentration to 0.75 mol / L and continue treatment at 70°C for 12 h to achieve sufficient expansion of the interlayer spacing. After intercalation, the interlayer spacing increased from about 1.1 nm to about 2.0 nm. Excess TBAOH was removed by alternate washing with ethanol and deionized water, and the mixture was dried in a vacuum drying oven at 60°C for 10 h. Comparative Example 5 used single-step intercalation (direct treatment with 0.75 mol / L TBAOH), Comparative Example 6 only underwent HF vapor treatment without TBAOH intercalation, and Comparative Example 1 used raw Ti3C2T. x MXene, without any modification.

[0184] The Al2O3 / AlF3 gradient coating was constructed using atomic layer deposition (ALD). Intercalated MXene material was loaded into the ALD reaction chamber and pretreated under vacuum at 110°C and low humidity (below 5%) for 30 min. First, using TMA / H2O as a precursor pair, an inner Al2O3 layer was deposited at 110°C, with the thickness increasing by approximately 0.1 nm per ALD cycle. Subsequently, a gradient transition layer was formed by gradually introducing TMA / HF-pyridine cycles, with the deposition temperature reduced to 90°C. The Al2O3 to AlF3 molar ratio was adjusted from 1:1 to 1:3 by varying the precursor cycle ratios. Finally, an outer AlF3 layer was deposited using pure TMA / HF-pyridine cycles. The total coating thickness was adjusted within the range of 2.0 nm to 3.0 nm according to the experimental design. Comparative Example 2 did not undergo coating treatment, while Comparative Example 3 used uniform Al2O3 coating (same total thickness, no gradient design).

[0185] Li₂MnO₃ nanoparticles were prepared by a co-precipitation method. According to the stoichiometric ratio of Li₂MnO₃, LiOH·H₂O and MnSO₄·H₂O were dissolved separately in deionized water at a Li:Mn molar ratio of 2:1. The Mn salt solution was slowly added dropwise to the Li salt solution under vigorous stirring, controlling the pH between 11 and 12. After stirring for 2 hours, the mixture was filtered and washed until neutral, dried at 80℃ for 8 hours, and then calcined in a muffle furnace at 550℃ for 8 hours (heating rate 2℃ / min) to obtain Li₂MnO₃ nanoparticles with an average particle size of approximately 15 nm. The coated MXene material and Li₂MnO₃ were mechanically compounded in a ball mill jar at the designed mass ratio (200 rpm, 2 hours, ball-to-material ratio 10:1). After ball milling, the mixture was vacuum dried at 120℃ for 4 hours to obtain the final cathode material. Comparative Example 4 did not add Li₂MnO₃.

[0186] The specific process parameters for each embodiment and comparative example are detailed in Tables 1-1 to 1-3.

[0187] In this application, the battery adopts a 3Ah to 5Ah stacked soft-pack structure. The above-mentioned positive electrode material, conductive agent, and binder are mixed at a designed weight ratio (93:2.5:4.5 in Examples 1 to 11, and 94:2:4 in Example 12) to prepare a positive electrode slurry, which is then coated onto an aluminum foil current collector with a thickness of 15μm. The areal density of the positive electrode sheet is controlled at (15±0.5) mg / cm². 2 After drying at 80℃ to 120℃, it is compacted under a pressure of 10MPa to 15MPa, with the compaction density controlled at 2.2g / cm³. 3 Up to 2.8 g / cm 3 .

[0188] The positive electrode, PP / PE / PP separator, and graphite negative electrode are stacked sequentially to form a stacked structure, and then encapsulated with an aluminum-plastic film. The assembled battery is dried in an 80°C vacuum oven for 24 hours to ensure the internal moisture content is below 50 ppm. The appropriate electrolyte (carbonate system or ionic liquid system, selected according to the example design) is injected into a glove box, and after encapsulation, a formation process is performed. Formation employs a low-current stepped charging strategy: the first cycle is constant current charging at 0.05C to the upper limit voltage of 4.8V, followed by constant voltage charging until the current cutoff is 0.01C, and then constant current discharging at 0.05C to the lower limit voltage of 2.0V. This process is repeated three times to complete initialization. The charge / discharge voltage window is uniformly set to 2.0V~4.8V.

[0189] To systematically evaluate the overall performance of the MXene cathode material of this application and verify the effectiveness of various technological innovations, the following uniform performance tests were performed on all embodiments and comparative examples. All data are based on the average value of tests on 3 to 5 parallel samples, with a typical error range of ±5% to ±10%. Specific test items are as follows:

[0190] (1) 0.1C First Charge-Discharge Test

[0191] At 25°C, the electrode was charged at a constant current of 0.1C to the upper limit voltage of 4.8V, then charged at a constant voltage until the current cutoff was 0.01C, and finally discharged at a constant current of 0.1C to the lower limit voltage of 2.0V. The initial discharge specific capacity (mAh / g) was recorded and calculated based on the mass of the positive electrode active material. The initial coulombic efficiency (ICE) was calculated using the formula ICE = (initial discharge capacity / initial charge capacity) × 100%. Simultaneously, the average discharge voltage (V) of the discharge curve was recorded, obtained by dividing the discharge energy (mWh) by the discharge capacity (mAh), i.e., V0. avg= Integral of discharge energy divided by integral of discharge capacity. This index quantitatively reflects the voltage range distribution of the capacity source.

[0192] (2) 25℃ room temperature cycling capacity retention test

[0193] At 25℃, the circuit was charged at a constant current of 1C to the upper limit voltage of 4.8V, then charged at a constant voltage until the current cutoff was 0.05C, and finally discharged at a constant current of 1C to the lower limit voltage of 2.0V. The discharge capacity was recorded at the 200th and 500th cycles, respectively. The capacity retention rate was calculated as (discharge capacity at the nth cycle / discharge capacity at the 1st cycle) × 100%. The capacity retention rate over 500 cycles indirectly reflects whether the interlayer spacing change rate during cycling meets the design target of no more than 15%.

[0194] (3) 45℃ high temperature cycling capacity retention test

[0195] Cyclic tests were conducted at 45°C using the same charge-discharge regime as at 25°C. The discharge capacity was recorded at the 100th and 200th cycles, and the capacity retention rate was calculated. Interfacial side reactions accelerate under high-temperature conditions; this test can more sensitively reflect the protective effect of the coating layer on the high-voltage interface of the cathode material.

[0196] (4) Ratio performance test

[0197] At 25℃, a fixed charging regime of 0.2C constant current and constant voltage charging to 4.8V (0.05C cutoff) was used. The discharge rates were set to 0.2C and 2C, respectively, and each rate was cycled 5 times to obtain a stable value. Using the 0.2C discharge capacity as a baseline (100%), the 2C / 0.2C capacity retention ratio (%) was calculated.

[0198] (5) DCIR internal resistance test

[0199] The battery was adjusted to 50% SOC, and a 2C discharge pulse was applied at 25°C for 10 seconds. The voltage difference before and after the pulse was recorded. DCIR = voltage difference / discharge current, in mΩ. Tests were performed once before cycling (on the 5th cycle after formation) and once after cycling (after 200 cycles at room temperature). This method directly outputs a single value from the device, eliminating the need for equivalent circuit fitting.

[0200] (6) 60℃ high temperature storage test

[0201] At 25°C, the battery was charged at a constant current of 0.5C to the upper limit voltage of 4.8V, then charged at a constant voltage until the current cutoff was 0.05C, and then discharged at a constant current of 0.5C to the lower limit voltage of 2.0V. The discharge capacity was recorded as the initial capacity C1. The battery was then fully charged again to 100% SOC using the same procedure and stored in a 60°C high-temperature chamber for 30 days. After storage, the battery was left at 25°C for at least 2 hours to restore thermal equilibrium, and then discharged at a constant current of 0.5C to 2.0V. The capacity C2 was recorded, and the capacity retention rate was calculated as (C2 / C1) × 100%. Subsequently, three standard charge-discharge cycles were performed at 25°C, and the third discharge capacity C3 was recorded. The capacity recovery rate was calculated as (C3 / C1) × 100%.

[0202] (7) -10℃ low temperature discharge test

[0203] The battery was fully charged at 25℃ using a constant current and constant voltage (0.5C) to 4.8V (0.05C cutoff). It was then transferred to a -10℃ environment and left to stand for 4 hours to reach thermal equilibrium. It was then discharged at a constant current of 0.5C to 2.0V, and the low-temperature discharge capacity was recorded. Low-temperature capacity retention rate = (-10℃ discharge capacity / 25℃ discharge capacity) × 100%.

[0204] (8) Electrolyte system compatibility test

[0205] Example 10 uses the EMIm-TFSI ionic liquid electrolyte system. By repeating the relevant indicators of tests 1) to 4) above, a horizontal comparison is made with Example 1 (carbonate system) to verify the versatility of the MXene cathode material in different anion systems.

[0206] The above testing methods aim to comprehensively evaluate the overall electrochemical performance of each embodiment and comparative example, and verify the effectiveness and necessity of key technological innovations such as interlayer spacing control, gradient coating, synergistic addition of Li2MnO3, and stepwise intercalation process through performance differences.

[0207] Through the above-mentioned systematic experimental design and standardized preparation and testing procedures, the contribution of the various technological innovations of this application to the comprehensive performance of MXene cathode materials can be accurately evaluated, providing reliable experimental basis for the engineering application of dual-ion co-intercalated MXene cathode technology.

[0208] The test results of all embodiments and comparative examples are analyzed and discussed, as shown in Tables 2-1 and 2-2, and specifically include the following parts:

[0209] (1) Effect of interlayer spacing regulation on anion intercalation capacity

[0210] As can be seen from the performance data table, the interlayer spacing control technology has a decisive impact on the discharge specific capacity of MXene cathode materials. Example 1 (interlayer spacing 2.0 nm) achieved an initial discharge specific capacity of 138 mAh / g, an initial coulombic efficiency of 87.5%, and an average discharge voltage of 4.25 V. In contrast, the unmodified raw MXene Comparative Example 1 (interlayer spacing 1.0 nm~1.2 nm) had an initial discharge specific capacity of only 52 mAh / g, an initial coulombic efficiency of 58.5%, and an average discharge voltage of 3.55 V. Example 1 shows an approximately 165% improvement in discharge specific capacity compared to Comparative Example 1. This significant difference indicates that increasing the interlayer spacing from approximately 1.0 nm to 2.0 nm can improve the PF6... - The insertion and extraction of anions (approximately 0.508 nm in diameter) provide ample structural space, which is a prerequisite for achieving high capacity. Comparative Example 6 only underwent HF vapor treatment without TBAOH intercalation, and the interlayer spacing was only increased to 1.3 nm, with a discharge specific capacity of 68 mAh / g. Although this is an improvement compared to Comparative Example 1, it is still far lower than Example 1, further confirming that TBAOH intercalation to increase the interlayer spacing is a necessary condition for obtaining high capacity.

[0211] Further information can be extracted from the comparison of average discharge voltages. The average discharge voltage of Example 1, 4.25V, is significantly higher than that of Comparative Example 1 (3.55V) and Comparative Example 6 (3.85V). According to the electrochemical principles of dual-ion batteries, the potential for anion insertion into the positive electrode is typically higher than 4.0V (vs. Li / Li). + The pseudocapacitive energy storage on the MXene surface mainly occurs in the lower voltage range. The high average discharge voltage of Example 1 is consistent with the electrochemical characteristics of anion phase intercalation, indicating that its capacity is mainly distributed in the high voltage range; the low average voltage of Comparative Example 1 is consistent with the energy storage characteristics dominated by surface adsorption / desorption. This difference in voltage distribution supports the judgment that the anion intercalation energy storage mechanism proposed in this application participates in the capacity contribution of Example 1, but the complete mechanism confirmation still needs to be further verified by in-situ structural characterization methods (such as in-situ XRD or XPS).

[0212] Data from the process window validation group revealed a trade-off between capacity and stability in the interlayer spacing parameter. Example 2 (1.8 nm) exhibited a discharge specific capacity of 118 mAh / g, lower than Example 1's 138 mAh / g, but its 500-cycle capacity retention reached 87.5%, slightly higher than Example 1's 86.2%. While the smaller interlayer spacing limited the amount of anion intercalation per cycle, it resulted in less structural strain during cycling, which is beneficial for long-term stability. Example 3 (2.2 nm) showed the opposite trend: the capacity reached a maximum of 148 mAh / g, but the 500-cycle retention decreased to 82.2%, and the 45°C / 200-cycle retention also decreased from 82.8% in Example 1 to 78.5%. While a larger interlayer spacing provided more space for intercalation, the interlayer bonding was correspondingly weakened, making irreversible structural changes more likely to occur during repeated anion intercalation-deintercalation processes. The complete parameter scanning series consisting of Examples 2, 1, and 3 confirms the rationality of setting the preferred interlayer spacing range of 1.8nm to 2.2nm in this application, with 2.0nm in Example 1 being the optimal value for overall performance.

[0213] (2) Necessity and functional verification of gradient coating layer design

[0214] The comparative data between Comparative Example 2 (uncoated) and Example 1 strongly demonstrate the necessity of surface coating treatment. The difference in initial capacity between the two is limited (Comparative Example 2: 132 mAh / g, Example 1: 138 mAh / g), indicating that the coating layer has a relatively small impact on the initial embedding capacity. However, under long-term cycling and high-temperature conditions, the difference widens dramatically. The capacity retention rate of Comparative Example 2 at 25°C / 500 cycles is only 68.2%, 18 percentage points lower than 86.2% of Example 1; the capacity retention rate at 45°C / 200 cycles drops to 60.2%, significantly lower than 82.8% of Example 1. In the 60°C storage test, the storage retention rate and storage recovery rate of Comparative Example 2 are 75.8% and 82.5%, respectively, while those of Example 1 are 91.2% and 95.5%. DCIR data provides more direct interface information: In Comparative Example 2, the DCIR was 52 mΩ before cycling and increased to 95 mΩ after cycling, an increase of 83%; in Example 1, the DCIR was 45 mΩ before cycling and only increased to 58 mΩ after cycling, an increase of 29%. The sharp increase in impedance during cycling in Comparative Example 2 indicates that, without surface protection, the MXene cathode faces severe interfacial oxidation side reactions in a high-voltage environment of 4.8V, and electrolyte decomposition products continuously accumulate on the electrode surface. The introduction of the coating layer effectively blocks direct contact between the electrode and the electrolyte, which is indispensable for the long-term stable operation of the material.

[0215] Based on the confirmation of the necessity of coating, a comparison between Comparative Example 3 (uniform Al2O3 coating) and Example 1 (gradient coating) reveals the technical advantages of gradient design. Comparative Example 3 and Example 1 have the same total coating thickness of 2.5 nm, but there are significant differences in kinetic-related indicators: the 2C / 0.2C rate retention ratio of Comparative Example 3 is 58.5%, which is 14 percentage points lower than the 72.5% of Example 1; the low-temperature capacity retention at -10℃ is 48.5%, which is 13.5 percentage points lower than the 62.0% of Example 1. The technical root of this difference lies in the difference in ion conductivity characteristics between Al2O3 and AlF3. Al2O3 has excellent chemical inertness and electrochemical stability, but low ion conductivity; when used as a uniform coating layer, it becomes a bottleneck for ion transport under high rate and low-temperature conditions. AlF3 has significantly better ion conductivity than Al2O3, but its chemical stability is relatively weaker. The gradient design of this application places Al2O3 on the inner side near the MXene matrix as a chemical barrier and AlF3 on the outer side as an ion conduction channel. The molar ratio of Al2O3 to AlF3 gradually changes from 1:1 to 1:3 from the inside out. This functional spatial partitioning achieves synergistic optimization of chemical stability and ion conductivity. Comparative Example 3 showed a 72.5% retention rate at 45°C / 200 cycles, 10.3 percentage points lower than Example 1's 82.8%, indicating that the gradient design also provides superior interface protection under high-temperature acceleration conditions. The DCIR of Comparative Example 3 before cycling was 62 mΩ, higher than Example 1's 45 mΩ, reflecting the higher ion transport impedance of the uniform Al2O3 layer. After cycling, it increased to 82 mΩ, an increase of 32%, close to Example 1's 29%, but the initial impedance disadvantage remained. The gradient coating, by placing the highly conductive AlF3 layer on the outer side in direct contact with the electrolyte, effectively reduced the initial interface impedance, while the inner Al2O3 layer controlled the impedance growth during long-term cycling.

[0216] The verification of the coating thickness window further clarified the parameter boundaries. Example 4 (coating thickness 2.0 nm) showed a first-cycle capacity of 140 mAh / g, similar to Example 1, and a rate performance of 75.2%, even slightly higher than Example 1's 72.5%, indicating that a thinner coating layer hinders ion transport less. However, Example 4's 45°C / 200-cycle retention of 76.2% and 60°C storage retention of 85.5% were significantly lower than Example 1's 82.8% and 91.2%, respectively, indicating that a 2.0 nm chemical barrier thickness is insufficient for protection under high temperature and long-term conditions. Example 5 (coating thickness 3.0 nm) showed the best cycling stability (87.8% at 25°C / 500 cycles) and the highest 60°C storage recovery rate (96.5%), but its rate performance decreased to 65.8%, and its low-temperature performance decreased to 55.8%, indicating that a thicker coating layer increased the ion transport path. A coating thickness window of 2 nm to 3 nm achieved a reasonable balance between protective capability and ion conductivity.

[0217] A comparison of gradient transition methods (Example 8: Mild Type; Example 1: Standard Type; Example 9: Rapid Change Type) shows that the three schemes have very little difference in various core performance indicators: the 500-cycle retention rates are 85.5%, 86.2%, and 84.8%, respectively; and the rate performance is 70.2%, 72.5%, and 71.8%, respectively, with all differences within the experimental error range. This result indicates that the gradient coating design has low sensitivity to the transition method and good process robustness.

[0218] (3) Functional verification of Li2MnO3 synergistic additive

[0219] The data from Comparative Example 4 (without Li2MnO3) clearly reveal the dual functionality of the Li2MnO3 nanoparticles. The initial coulombic efficiency of Comparative Example 4 was only 72.8%, nearly 15 percentage points lower than the 87.5% of Example 1, while the difference in first-cycle discharge specific capacity was limited (135 mAh / g for Comparative Example 4, 138 mAh / g for Example 1). This indicates that Comparative Example 4 consumed a large amount of irreversible lithium during charging. The formation of the cathode-electrolyte interphase (CEI) film and the construction of the solid-electrolyte interphase (SEI) film on the negative electrode side of the MXene cathode under high voltage conditions jointly consumed a large amount of active lithium, resulting in a significantly lower initial-cycle efficiency. Li2MnO3 underwent irreversible decomposition and released Li during the 4.5V to 4.8V potential range of the first charge. + To compensate for the aforementioned lithium loss, the initial coulombic efficiency was increased from 72.8% to 87.5%.

[0220] The contribution of Li₂MnO₃ is not limited to lithium source compensation. The capacity retention rate of Comparative Example 4 at 25°C / 500 cycles was 78.8%, lower than 86.2% in Example 1, and the capacity retention rate at 45°C / 200 cycles was 75.5%, also lower than 82.8% in Example 1. Based on this, it is speculated that the Mn-based oxide residue formed after the initial decomposition of Li₂MnO₃ may act as an interface modification component, synergistically enhancing the interface stability under high voltage with the gradient coating layer. The DCIR growth of Comparative Example 4 after cycling (from 48 mΩ to 65 mΩ, an increase of 35%) was higher than that of Example 1 (from 45 mΩ to 58 mΩ, an increase of 29%), further confirming the inhibitory effect of Li₂MnO₃ on interface degradation from the perspective of interface impedance.

[0221] The validation of the Li2MnO3 content window clarified the parameter optimization space. Example 6 (5 wt%) achieved an initial coulombic efficiency of 82.5%, a significant improvement over Comparative Example 4's 72.8%, but still lower than Example 1 (8 wt%, 87.5%), indicating that 5 wt% Li2MnO3 was insufficient to fully compensate for irreversible lithium loss in the first cycle. Example 7 (10 wt%) further improved the initial coulombic efficiency to 90.2%, demonstrating sufficient lithium compensation, but its average discharge voltage (4.18 V) was slightly lower than Example 1 (4.25 V), and the capacity retention after 500 cycles also decreased to 83.5%. This is because the higher Li2MnO3 content generated more Mn ion dissolution and oxygen release side reactions during decomposition, negatively impacting the active material structure and electrolyte stability. Therefore, 5 wt%–10 wt% constitutes an effective process window, with the area around 8 wt% representing the optimal range for overall performance.

[0222] (4) Technical advantages of step intercalation process

[0223] Comparative Example 5 employed a single-step TBAOH intercalation (direct treatment with 0.75 mol / L), resulting in an interlayer spacing of (1.7 ± 0.2) nm, lower than the target value of (2.0 ± 0.1) nm in Example 1, and exhibiting a larger range of interlayer spacing fluctuations. The initial discharge specific capacity of Comparative Example 5 was 115 mAh / g, 23 mAh / g lower than that of Example 1. During the single-step high-concentration TBAOH treatment, the permeation rate of the intercalating agent molecules between the MXene layers was uneven. The outer layers first came into contact with the high-concentration solution, resulting in rapid intercalation. The internal regions, due to limited diffusion, underwent insufficient intercalation, leading to a structure with an uneven interlayer spacing distribution. This unevenness reduced the effective anion insertion sites and caused localized stress concentration during cycling. The capacity retention rate of Comparative Example 5 after 500 cycles was 70.5%, approximately 16 percentage points lower than that of Example 1, and its rate performance of 60.5% was also significantly lower than the 72.5% of Example 1. These findings are consistent with the trends observed in the cycling and rate data. The stepwise strategy of this application achieves uniform penetration through low-concentration pretreatment, and then achieves full expansion of the target interlayer spacing on the basis of uniformity through high-concentration deep treatment, thus ensuring precise control of the interlayer spacing and spatial uniformity.

[0224] (5) Application extension verification

[0225] Example 10 used an EMIm-TFSI ionic liquid electrolyte system to verify the effect of MXene cathode material on TFSI. - Adaptability of anion intercalation. The average discharge voltage of Example 10 reached 4.35 V, higher than 4.25 V of the carbonate system in Example 1, which is related to the wider electrochemical window of the ionic liquid and TFSI. - This is consistent with the higher oxidative stability of anions. The initial discharge specific capacity of Example 10 was 125 mAh / g, lower than the 138 mAh / g of Example 1, presumably due to the higher TFSI. - The larger geometric dimensions are related to the limited embedding dynamics. Of particular note is the performance of Example 10 in high-temperature cycling at 45°C (85.5% retention after 200 cycles), which is superior to the 82.8% retention of Example 1. This is attributed to the excellent thermal stability and extremely low vapor pressure of the ionic liquid itself. The comparison between Example 10 and Example 1 demonstrates that this application achieves good compatibility with different anionic systems through a reasonable interface design.

[0226] Example 11 used a PAA aqueous binder instead of the PVDF / NMP route, and the performance was very similar to that of Example 1, with an initial capacity of 135 mAh / g, a 500-cycle retention rate of 84.8%, and a rate capability of 71.2%. These results indicate that the modified MXene material has good compatibility with the aqueous binder, providing data support for the adoption of an environmentally friendly process route.

[0227] Example 12 reduced the conductive agent content from 2.5 wt% to 2 wt%, allocating the saved formulation space to the active material (94 wt%). Example 12 achieved a first-cycle capacity of 140 mAh / g, a rate performance of 73.8%, a 500-cycle retention rate of 87.8%, and a 60°C storage recovery rate of 95.8%, achieving the best overall performance among all examples. This demonstrates that MXene's own two-dimensional conductive network can partially replace the function of an external conductive agent, reducing the amount of conductive agent used without sacrificing rate performance. This reflects the inherent advantages of MXene materials in terms of conductivity and verifies the potential for further improvement through multi-parameter synergistic optimization.

[0228] (6) Comprehensive performance evaluation

[0229] Based on all test data, the dual-ion co-intercalated MXene cathode material system of this application demonstrates a comprehensive improvement in multiple key performance indicators. Example 1 shows an initial discharge specific capacity of 138 mAh / g, an initial coulombic efficiency of 87.5%, and an average discharge voltage of 4.25 V, representing a substantial improvement compared to the original MXene Comparative Example 1 (52 mAh / g, 58.5%, 3.55 V). Capacity retention of 86.2% at 25℃ / 500 cycles and 82.8% at 45℃ / 200 cycles indicates good structural stability during long-term cycling. A 72.5% 2C / 0.2C rate retention ratio and a 62.0% capacity retention at -10℃ verify the improvement effect of the gradient coating design on ion conduction kinetics. A 95.5% capacity recovery rate after 30 days of storage at 60℃ demonstrates good chemical stability of the material system under extreme conditions.

[0230] Through systematic comparative experiments, this application clearly demonstrates the necessity and independent contribution of each technological innovation: interlayer spacing control provides the structural basis for anion intercalation (capacity increased from 52 mAh / g in Comparative Example 1 to 138 mAh / g in Example 1); the gradient coating layer solves the high-voltage interface stability problem (500-cycle retention rate increased from 68.2% in Comparative Example 2 to 86.2% in Example 1); the Li2MnO3 synergistic additive compensates for irreversible lithium loss in the first cycle (coulombic efficiency increased from 72.8% in Comparative Example 4 to 87.5% in Example 1); and the step-intercalation process ensures precise control and uniformity of the structure (capacity increased from 115 mAh / g in Comparative Example 5 to 138 mAh / g in Example 1). These four technological features form a synergistic effect through functional complementarity: interlayer spacing control provides anion intercalation space, gradient coating protects the structural integrity of this space during long-term cycling, Li2MnO3 compensates for the active lithium consumed by the interface reaction and enhances interface stability, and step-intercalation ensures the uniform realization of the above design at the material level. This multi-level collaborative design provides a complete technical solution for the engineering application of MXene-based cathode materials.

[0231] Table 1-1

[0232]

[0233] Table 1-2

[0234]

[0235] Table 1-3

[0236]

[0237] In Tables 1-1, 1-2, and 1-3, Example 1 and Comparative Examples 1 to 6 belong to the core innovation verification group, Examples 2 to 9 belong to the process window verification group, and Examples 10 to 12 belong to the application expansion verification group.

[0238] Table 2-1

[0239]

[0240] Table 2-2

[0241]

[0242] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes can be made in form and detail without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A method for preparing a single battery cell, characterized in that, include: Provide a battery cell assembly, the battery cell assembly being formed by stacking or winding a positive electrode sheet, a separator and a negative electrode sheet; A housing is provided to house the battery cell assembly within the housing; Provide electrolyte and inject the electrolyte into the housing; Perform the formation step; The positive electrode sheet includes a positive electrode active component, which includes a modified MXene material. The modified MXene material includes an MXene matrix and an Al2O3 / AlF3 gradient coating layer covering the MXene matrix. The preparation method of the modified MXene material includes: Preparation of MXene matrix materials; The MXene matrix material is coated with an Al2O3 / AlF3 gradient to form an Al2O3 / AlF3 gradient coating layer; The preparation method of the MXene matrix material includes: Ti3AlC2 powder was pretreated to remove moisture and organic impurities, and then reacted with an aqueous hydrofluoric acid solution to obtain Ti3C2T. x MXene; The Ti3C2T x MXene was post-treated in a hydrogen fluoride vapor atmosphere to obtain the precursor; The precursor is dispersed in a tetrabutylammonium aqueous solution of a first concentration, and preliminary intercalation is performed at a first temperature to obtain a first intercalation product; The first intercalation product was further intercalated in a tetrabutylammonium aqueous solution of the second concentration at a second temperature to obtain the MXene matrix material; The first concentration is less than the second concentration, and the first temperature is less than the second temperature; The positive electrode active ingredient also includes Li2MnO3 as a synergistic additive.

2. The method for preparing a single battery cell according to claim 1, characterized in that, The general formula of the MXene matrix is ​​Ti3C2T. x T x The MXene matrix comprises -OH, -O, and -F, and has 5 to 50 layers with an average lateral dimension of 0.5 μm to 10 μm. The molar fraction of -F functional groups is 20% to 60%, the molar fraction of -OH functional groups is 15% to 50%, and the molar fraction of -O functional groups is 10% to 40%.

3. The method for preparing a single battery cell according to claim 1, characterized in that, The hydrofluoric acid aqueous solution has a mass fraction of 30% to 50%.

4. The method for preparing a single battery cell according to claim 1, characterized in that, The first concentration is 0.2 mol / L to 0.3 mol / L, and the second concentration is 0.7 mol / L to 0.8 mol / L.

5. The method for preparing a single battery cell according to claim 1, characterized in that, The first temperature is 60℃~70℃, and the second temperature is 65℃~75℃.

6. The method for preparing a single battery cell according to claim 1, characterized in that, The gradient wrapping method includes: The MXene matrix material was atomically deposited using a first deposition solution at a third temperature to form an Al2O3 inner layer. On the surface of the inner Al2O3 layer, atomic layer deposition is performed using a third deposition solution at a fourth temperature to form an AlF3 transition layer. On the surface of the AlF3 transition layer, atomic layer deposition is performed using a second deposition solution at a fourth temperature to form an AlF3 outer layer; The first deposition solution is a mixture of trimethylaluminum and water, the second deposition solution is a mixture of hydrogen fluoride-pyridine complex, and the third deposition solution is a mixture of the first deposition solution and the second deposition solution; the third temperature is greater than the fourth temperature.

7. The method for preparing a single battery cell according to claim 6, characterized in that, The third temperature is 100℃~120℃, and the fourth temperature is 80℃~100℃.

8. The method for preparing a single battery cell according to claim 6, characterized in that, The thickness of the Al2O3 inner layer is 0.8 nm to 1.2 nm, the thickness of the transition layer is 0.8 nm to 1.0 nm, and the thickness of the AlF3 outer layer is 1.0 nm to 1.8 nm.

9. The method for preparing a battery cell according to claim 1, characterized in that, The average particle size of the Li2MnO3 synergistic additive is 10nm~20nm, and the specific surface area is 80m². 2 / g~150m 2 / g.

10. The method for preparing a battery cell according to claim 8 or 9, characterized in that, The preparation method of the Li2MnO3 synergistic additive includes: Manganese sulfate and lithium hydroxide were dissolved in deionized water in stoichiometric ratio, and after co-precipitation under alkaline conditions, they were calcined at 500℃~600℃ to obtain the Li2MnO3 synergistic additive.

11. A single battery cell, characterized in that, include: A battery cell assembly, wherein the battery cell assembly is formed by stacking or winding a positive electrode sheet, a separator and a negative electrode sheet; The housing, in which the battery cell assembly is located; An electrolyte is provided, located within the housing, and the battery cell assembly is immersed in the electrolyte. The positive electrode sheet includes a positive electrode active component, which includes a modified MXene material. The modified MXene material includes an MXene matrix and an Al2O3 / AlF3 gradient coating layer covering the MXene matrix. The preparation method of the modified MXene material includes: Preparation of MXene matrix materials; The MXene matrix material is coated with an Al2O3 / AlF3 gradient to form an Al2O3 / AlF3 gradient coating layer; The preparation method of the MXene matrix material includes: Ti3AlC2 powder was pretreated to remove moisture and organic impurities, and then reacted with an aqueous hydrofluoric acid solution to obtain Ti3C2T. x MXene; The Ti3C2T x MXene was post-treated in a hydrogen fluoride vapor atmosphere to obtain the precursor; The precursor is dispersed in a tetrabutylammonium aqueous solution of a first concentration, and preliminary intercalation is performed at a first temperature to obtain a first intercalation product; The first intercalation product was further intercalated in a tetrabutylammonium aqueous solution of the second concentration at a second temperature to obtain the MXene matrix material; The first concentration is less than the second concentration, and the first temperature is less than the second temperature; The positive electrode active ingredient also includes Li2MnO3 as a synergistic additive.

12. A battery device, characterized in that, The battery device includes a battery cell prepared by the method described in any one of claims 1 to 10, or a battery cell as described in claim 11, wherein the battery device includes one or more of a battery module, a battery pack, and an energy storage battery.

13. An electrical appliance, characterized in that, The electrical device includes the battery device as described in claim 12, the battery device being used to provide electrical energy.

14. An energy storage device, characterized in that, The energy storage device includes the battery device as described in claim 12, the battery device being used to store electrical energy.

Images