MXene interface reconstruction graphite and preparation method thereof, negative electrode, battery and electric device

Abstract

The invention discloses MXene interface reconstruction graphite and a preparation method thereof, a negative electrode, a battery and a power utilization device.The preparation method comprises the steps that a graphite material is subjected to amination treatment, so that the surface of the graphite material contains amino functional groups, and aminated graphite is obtained; and mixing and dispersing the aminated graphite and MXene in a water solvent, and enabling an MXene sheet layer to be adhered to a base surface of the graphite through an electrostatic adsorption effect, so as to form the MXene interface reconstructed graphite with an interlayer-shaped MXene-graphite-MXene heterostructure. The Ah-grade battery with the MXene interface reconstruction graphite negative electrode has super-long durability, high energy density and excellent rate capability, and is superior to a pure graphite negative electrode.

Description

Technical Field

[0001] The present invention belongs to the field of materials, and particularly relates to a MXene interface-reconstructed graphite anode material and method, an anode, a battery, and an electrical device. Background Art

[0002] Commercial lithium-ion batteries (LIBs) have attracted worldwide attention as power sources for electric vehicles due to their high energy density, long cycle life, and cost-effectiveness. Generally, LIBs are made of a graphite anode and a transition metal oxide / phosphide cathode in an organic electrolyte, and have a high energy density of 140-280 Wh kg -1 at ambient temperature conditions. However, under extreme conditions such as sub-zero temperatures and high rates, LIBs usually have poor electrochemical performance due to high electrochemical polarization at the electrolyte / electrode interface and uneven reaction currents associated with the inevitable formation of lithium dendrites at the edges of graphite. The emerging lithium dendrites will further prevent Li + from inserting into the graphite interlayer, severely exacerbating the polarization and uncontrollable growth of lithium dendrites, which largely hinders the practical application of LIBs in certain scenarios.

[0003] To address the problems of large electrochemical polarization and uncontrollable lithium dendrites, researchers have explored some strategies, including promoting the migration of Li + in the solid electrolyte interface (SEI) layer and increasing the diffusion coefficient of Li + in the anode, specifically as follows: (1) Using advanced electrolytes such as local high-concentration electrolytes (LHCE) to promote the formation of an anion-derived interface with high ionic conductivity and improve the reversibility of the lithium deposition layer; (2) Constructing an artificial interface layer (such as an inorganic layer) to reduce the Li + desolvation energy barrier at the electrolyte / graphite interface and accelerate the interfacial reaction kinetics; (3) Uniformly distributing Li + by adding hard carbon or amorphous carbon with a high specific surface area to the graphite anode to inhibit the deposition of metallic lithium. Although these strategies can alleviate electrochemical polarization and lithium dendrites to a certain extent, eliminating lithium dendrites in graphite anodes under extreme conditions such as low temperature (<0 °C) and high rate (>4C, the goal of the US Advanced Battery Consortium) remains a huge challenge. Summary of the Invention

[0004] Aiming at the technical problems in the prior art that the graphite anode material of commercial lithium-ion batteries has a decline in electrochemical performance and safety problems due to the generation of lithium dendrites in low-temperature or high-rate environments, resulting in limited practical applications.

[0005] The first aspect of the present invention provides a method for preparing MXene interfacial reconstructed graphite, and the steps include: subjecting a graphite material to amination treatment to make the surface of the graphite material contain amino functional groups, thereby obtaining aminated graphite; mixing and dispersing the aminated graphite and MXene in a solvent, and through electrostatic adsorption, forming an MXene interfacial layer on the basal plane of the graphite to obtain MXene interfacial reconstructed graphite with a sandwich-like MXene-graphite-MXene heterostructure.

[0006] In some embodiments, the specific steps of the above amination treatment include: treating the graphite material with an amino silane coupling agent; more specific steps include: mixing and treating the graphite material with an aqueous solution of an amino silane coupling agent.

[0007] In some embodiments, the above amino silane coupling agent is selected from one or more of: aminopropyltrimethoxysilane (APS), γ-aminopropyltriethoxysilane (KH-550), β-aminoethyltrimethoxysilane (KH560), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH602), 3-aminopropyltriethoxysilane (APTES), N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, bis(3-triethoxysilylpropyl)amine, N-cyclohexyl-γ-aminopropylmethyldimethoxysilane (KH612), bis(triethoxysilylpropyl)amine (GX-552), N-n-butyl-3-aminopropyltrimethoxysilane.

[0008] In some embodiments, the above MXene contains fluorine (-F), hydroxyl (-OH), and oxygen (-O) functional groups.

[0009] In some embodiments, the Zeta potential of the above MXene is negative, and the Zeta potential of the aminated graphite is positive.

[0010] In some embodiments, the preparation method of the above MXene includes: first etching the A layer in the MAX phase with a fluorine-containing etching solution, and obtaining it after washing, exfoliating, and solid-liquid separation; preferably, the fluorine-containing etching solution is a hydrofluoric acid solution or a mixed solution of a fluoride salt and an acid; more preferably, the fluorine-containing etching solution is a mixed solution of lithium fluoride and hydrochloric acid.

[0011] In some embodiments, for the preparation method of the above MXene interfacial reconstructed graphite, the steps further include: solid-liquid separation and drying treatment to obtain a powder of MXene interfacial reconstructed graphite.

[0012] In some embodiments, for the preparation method of the above MXene interfacial reconstructed graphite, the steps further include: a purification step, washing and purifying the dispersion of the obtained MXene interfacial reconstructed graphite in the aqueous solvent to obtain an aqueous dispersion of MXene interfacial reconstructed graphite.

[0013] In the second aspect of the present invention, there is provided an MXene interface-reconstructed graphite powder obtained by the above preparation method, or an aqueous dispersion of MXene interface-reconstructed graphite.

[0014] In the third aspect of the present invention, there is provided an MXene interface-reconstructed graphite, which has a sandwich-like MXene-graphite-MXene heterostructure, and MXene sheets form an MXene interface layer on the basal plane of graphite.

[0015] In some embodiments, the above-mentioned MXene interface-reconstructed graphite characterization shows that it includes carbon, oxygen, fluorine, and transition metal elements; preferably, the transition metal elements are selected from one or more of Ti, V, Nb, Ta, Zr, W, Mo, and Cr.

[0016] In some embodiments, the conductivity of the above-mentioned MXene interface-reconstructed graphite is more than 2 times that of pure graphite; preferably, it is 2 to 2.5 times.

[0017] In some embodiments, metallic lithium preferentially grows along the (110) plane on the MXene interface of the above-mentioned MXene interface-reconstructed graphite.

[0018] In some embodiments, the content of MXene in the above-mentioned MXene interface-reconstructed graphite is ≤ 2 wt.%, preferably, it is between 1 and 2 wt.%; more preferably, it is between 1 and 1.5 wt.%, and still more preferably, it is between 1 and 1.2 wt.%.

[0019] In some embodiments, lithium ions can deposit on the above-mentioned MXene interface-reconstructed graphite to form metallic lithium with a body-centered cubic lattice structure, and the exposed crystal plane of the metallic lithium is the (110) crystal plane.

[0020] In some embodiments, the size of the above-mentioned MXene sheets ranges from 0.5 to 4 microns.

[0021] In some embodiments, the particle size range of the above-mentioned MXene interface-reconstructed graphite ranges from 100 to 1000 microns.

[0022] In some embodiments, the thickness of the above-mentioned MXene sheets ranges from 1 to 10 nm, preferably, the thickness ranges from 1 to 3 nm;

[0023] In some embodiments, the thickness of the MXene interface layer in the above-mentioned MXene interface-reconstructed graphite ranges from 1 to 10 nm, preferably, the thickness is from 1 to 3 nm.

[0024] In some embodiments, the thickness of the MXene interface layer in the above-mentioned MXene interface-reconstructed graphite is the thickness of a single sheet or several sheets of MXene sheets.

[0025] In some embodiments, the thickness of the MXene interface layer in the above-mentioned MXene interface-reconstructed graphite ranges from 1 to 10 nm, preferably from 1 to 3 nm.

[0026] The fourth aspect of the present invention provides a lithium metal / graphite composite material, comprising the above-mentioned MXene interface-reconstructed graphite; and lithium metal on the surface of the MXene interface-reconstructed graphite.

[0027] In some embodiments, the above-mentioned lithium metal is on the surface of the MXene interface layer.

[0028] In some embodiments, the crystal lattice structure of the above-mentioned lithium metal is body-centered cubic.

[0029] In some embodiments, the exposed crystal plane of the above-mentioned lithium metal is the (110) crystal plane.

[0030] In some embodiments, the lattice spacing of the above-mentioned lithium metal is

[0031] In some embodiments, the above-mentioned lithium metal microscopically presents an oval-shaped particle morphology.

[0032] The fifth aspect of the present invention provides a battery electrode, which contains the above-mentioned MXene interface-reconstructed graphite, or the above-mentioned lithium metal / graphite composite material.

[0033] In some embodiments, the mass loading density of the MXene interface-reconstructed graphite in the above-mentioned battery electrode is greater than 8 mg cm -2 , more preferably, it ranges from 8 to 20 mg cm -2 ; still more preferably, it ranges from 10 to 19.3 mg cm -2 .

[0034] In some embodiments, when the above-mentioned battery electrode is used as the negative electrode of a lithium-ion battery, lithium ions are deposited on the MXene interface-reconstructed graphite to form body-centered cubic lithium metal with a (110) crystal plane.

[0035] In some embodiments, the average exfoliation strength of the above-mentioned battery electrode is more than 1.5 times that of a graphite electrode.

[0036] In some embodiments, the deposition capacity of lithium metal in the above-mentioned battery electrode ranges from 1 to 10 mAh cm -2 , and no lithium dendrites are generated.

[0037] The fifth aspect of the present invention provides a preparation method for the above-mentioned battery electrode, which is characterized in that the steps include: mixing the MXene interface-reconstructed graphite, a binder, a conductive agent and a solvent to form a slurry, and then coating it on a current collector.

[0038] In some embodiments, the solid content in the above-mentioned slurry is ≥ 37%, preferably ≥ 38%, more preferably ≥ 39%; even more preferably ≥ 42%.

[0039] In some embodiments, the viscosity of the above-mentioned slurry is ≥ 2000 mPa·s -1 , preferably ≥ 3451 mPa·s -1 , more preferably ≥ 4700 mPa·s -1 , even more preferably ≥ 5954 mPa·s -1 , still preferably ≥ 11291 mPa·s -1 .

[0040] In some embodiments, the above-mentioned binder contains hydrogen bonds and the solvent contains water.

[0041] In some embodiments, the above-mentioned binder is carboxymethyl cellulose.

[0042] In some embodiments, the solid content in the above-mentioned slurry is between 37% and 42%.

[0043] In some embodiments, the viscosity of the above-mentioned slurry is between 2000 and 12000 mPa·s -1 ; preferably between 3451 and 11291 mPa·s -1 ; more preferably between 4700 and 11291 mPa·s -1 , even more preferably between 5954 and 11291 mPa·s -1 .

[0044] The sixth aspect of the present application provides a battery, which contains the battery negative electrode as described in the above claims.

[0045] The seventh aspect of the present invention provides an electricity-using or electricity-storing device, which contains the above-mentioned battery. The electricity-using devices include new energy electric vehicles, electric bicycles, electric airplanes, electric drones, electric robots, etc.; the electricity-storing devices include energy storage power stations, assembled battery packs, etc.

[0046] The beneficial technical effects of the present invention: The present invention provides an effective strategy for interfacial reconstruction from carbon to MXene in a graphite electrode to eliminate lithium dendrites in commercial lithium-ion batteries under extreme conditions. The outermost MXene interfacial layer can not only effectively reduce the nucleation barrier of Li in the negative electrode, but also has good lattice compatibility with the precipitated lithium, which helps to horizontally grow dense-packed bcc-Li (body-centered cubic metallic lithium) along the (110) plane under extreme conditions. The Ah-level battery with the MXene interfacial reconstructed graphite negative electrode has ultra-long durability, high energy density, and excellent rate performance, which are superior to the pure graphite negative electrode. Description of the Drawings

[0047] Figure 1 (a) Schematic diagram of the synthesis of MXene-reconstructed graphite; (b-d) Test results of the surface zeta potential of graphite (b), APS-graphite (c), and MXene (d).

[0048] Figure 2 (a) Schematic diagram of the structure of MXene-configured graphite of the present invention, showing that layered graphite is sandwiched between two MXene interfacial layers, forming a unique sandwich structure; (b) Fourier transform infrared spectroscopy (FTIR) of graphite and APS graphite.

[0049] Figure 3 (a) Optical photographs of MXene-graphite mixture (left) and MXene-configured graphite (right) dispersions; (b) Thermogravimetric analysis (TGA) curve of MXene-reconstructed graphite in air.

[0050] Figure 4 (a) Transmission electron microscope (TEM) image of MXene flakes, showing that their average size is distributed in the range of 0.5 - 4 μm; (b) Atomic force microscope (TEM) image of MXene flakes, showing that the thickness of MXene nanosheets is about 2 nm; (c) Scanning electron microscope (SEM) image of MXene-configured graphite observed from the side; (c) Particle size distribution diagrams of MXene-configured graphite and graphite.

[0051] Figure 5 (a) and (b) High-resolution transmission electron microscope (HRTEM) and corresponding FFT images (insets) of MXene-configured graphite of the present invention, revealing that the MXene interfacial layer is located on the surface of graphite.

[0052] Figure 6 (a) Cross-sectional transmission electron microscope (TEM) image of MXene-configured graphite of the present invention and EDS line scan analysis of C (b) and Ti (c) elements along the yellow line in a, showing that C elements are mainly in the middle, while Ti elements appear on both sides, clearly indicating that MXene-configured graphite of the present invention has a sandwich-like MXene-graphite-MXene heterostructure.

[0053] Figure 7 (a) Lithium atoms in MXene Ti3C2T of MXene-configured graphite of the present invention xThe adsorption energy on the interface is -3.41 eV, which is about 3 times that of pure graphite (-1.03 eV); (b) The nucleation overpotential of the lithium deposition layer on the MXene interface reconstructed graphite is 12 mV, which is much lower than that of pure graphite (42 mV).

[0054] Figure 8 For MXene Ti3C2T x Low-temperature TEM images and corresponding FFT patterns (insets) at different deposition capacities of 0.3 (a), 0.5 (b), and 0.7 (c) mAh cm -2 on the interface.

[0055] Figure 9 This is the experimental test of the lithium deposition mechanism on the MXene interface of the MXene interface reconstructed graphite anode material of the present invention; (a) Schematic diagrams of lithium nucleation, horizontal stacking, and planar growth on the MXene Ti3C2T x interface; (b, c) Low-temperature TEM images with a deposited lithium capacity of 0.3 (b) and 1.0 (c) mAh cm -2 on the interface, where the red, blue, and yellow regions represent crystalline Li metal, LiF, and Li2O nanocrystals, respectively. Inset: Fast Fourier transform pattern obtained from the deposited lithium metal region; (d) Enlarged image of the blue boxed region in Figure c, showing a good crystal structure; (e) Atomic resolution transmission electron microscope image of the boxed region in Figure d, showing the distance between the (110) facets (f) Lattice mismatch between the (110), (200), (211), and (310) planes of lithium and the hexagonal planes of the MXene Ti3C2T x interface. Inset: Lattice matching diagram between different crystal planes of Li and the MXene Ti3C2T x interface; (g) Adsorption energy of lithium atoms growing horizontally or vertically on lithium, MXene Ti3C2T x , graphene, and copper substrates.

[0056] Figure 10 This is the low-temperature TEM characterization of lithium deposited on the carbon layer at a current density of 0.5 mA cm -2 with a deposited lithium capacity of 1 mAh cm -2 .

[0057] Figure 11 This is the in-situ XRD patterns of the (110) plane (a) and (200) plane (b) of Li during Li deposition on MXene Ti3C2T -2 at a capacity level of 10 mAh cm x ; (c) Variation of the intensities of the Li (110) and (200) planes with increasing capacity.

[0058] Figure 12 (a) shows the viscosities of MXene interface-reconstructed graphite slurries with different solid contents in Example 3. The results show that the MXene interface-reconstructed graphite slurries have a viscosity as high as 3451 mPa s -1 . (b) shows the viscosities of slurries containing MXene interface-reconstructed graphite and graphite when the solid content is 42%.

[0059] Figure 13 (a) is a schematic diagram for testing the peel strength of the MXene-reconstructed graphite electrode in Example 3; (b) is the peel strength - peel elongation curve of the MXene-reconstructed graphite and pure graphite electrodes, showing that the average peel strength of the MXene-reconstructed graphite electrode is 11.9 N m -1 .

[0060] Figure 14 (a) is the powder conductivity of MXene and common graphite anode additives; (b) is the conductivity of the modified graphite anode in Example 3 of the present invention.

[0061] Figure 15 (a) shows the average apparent Li + diffusion coefficient of the graphite anode obtained from the galvanostatic intermittent titration technique (GITT) curve at -20°C in Example 3 of the present invention. The mass loadings of the anode are approximately 3 mg cm -2 (a) and approximately 12 mg cm -2 (b), respectively. c, the DRT curve corresponding to the anode with a mass loading of approximately 12 mg cm -2 at -20°C.

[0062] Figure 16 (a) is the high-resolution F1s XPS spectra of MXene interface-reconstructed graphite (a) and pure graphite (b) after one cycle, showing that the peak ratio (I LiF / I C-F ) of the MXene interface-reconstructed graphite increases compared to pure graphite, indicating that the SEI layer of the MXene interface-reconstructed graphite anode is rich in LiF, which is beneficial to the rapid transport of lithium ions.

[0063] Figure 17 is a schematic diagram of the graphite and modified graphite of the present invention; among them, (a) graphite; (b) mechanical mixture of graphene and graphite. (c) MXene interface-reconstructed graphite; (d) mechanical mixture of 1% MXene and graphite; (e) mechanical mixture of 5% MXene and graphite.

[0064] Figure 18Electrochemical performance of the MXene interfacially reconstructed graphite anode in Example 3 of the present invention; where (a) Activation energy of lithium ion diffusion in the SEI film of the MXene interfacially reconstructed graphite anode; (b) dQ / dV curve in the half-cell at -20 °C; (c) DCM curve at -20 °C, the low slope of which indicates a small surface area of deposited lithium on the MXene interface; (d-e) Cycling performance of the Ah-level soft-pack battery in the temperature range of 40 °C to -20 °C and the corresponding constant current / constant voltage charging stage, and the MXene interfacially reconstructed graphite anode exhibits excellent low-temperature performance; (f) Physical photos and SEM images of the MXene interfacially reconstructed graphite anode and the graphite anode after 100 cycles at -20 °C, showing no dendritic morphology characteristics.

[0065] Figure 19 SEM images of the (a-e) MXene interfacially reconstructed graphite anode at different states of charge (SoC) at -20 °C low temperature, showing that the deposited lithium presents a smooth and uniform morphology; (f-j) SEM images of the graphite anode at different states of charge (SoC) at -20 °C low temperature, and a large number of lithium dendrites can be seen.

[0066] Figure 20 XRD pattern of the deposited lithium on the MXene interfacially reconstructed graphite anode in Example 3 of the present invention at -20 °C low temperature and 200% SoC shows that its I (110) / I (200) diffraction peak intensity ratio is as high as 3.8, nearly 4 times that of pure graphite (1.1).

[0067] Figure 21 Macrophotographs and SEM images of the MXene interfacially reconstructed graphite anode (left) and the graphite anode (right) in Example 3 of the present invention after 100 lithium deposition / stripping cycles at -20 °C and 1C rate, the comparison shows that: the surface of the MXene interfacially reconstructed graphite anode still remains smooth, and no silver-white dead lithium is generated, while obvious dead lithium appears on the surface of the graphite anode.

[0068] Figure 22 SEM images of the anode materials at different lithium deposition amounts under room temperature conditions in Example 3 of the present invention. SEM images of pure MXene deposition: (a) 0.5 mAh cm -2 ; (b) 1 mAh cm -2 ; (c) 3 mAh cm -2 ; (d) 5 mAh cm -2 . SEM images of MXene-configurated graphite deposition: (e) 0.5 mAh cm -2 ; (f) 1 mAh cm -2 ;

[0069] (g) 3 mAh / cm -2 ; (h) 5 mAh / cm -2 . SEM images of MXene(1%)-graphite deposition: (i) 0.5 mAh / cm -2 ; (j) 1 mAh / cm -2 ; (k) 3 mAh / cm -2 ; (l) 5 mAh / cm -2 . SEM images of MXene(5%)-graphite deposition: (m) 0.5 mAh / cm -2 ; (n) 1 mAh / cm -2 ; (o) 3 mAh / cm -2 ; (p) 5 mAh / cm -2 .

[0070] SEM images of Graphene-graphite deposition: (q) 0.5 mAh / cm -2 ; (r) 1 mAh / cm -2 ; (s) 3 mAh / cm -2 ;

[0071] (t) 5 mAh / cm -2 . SEM images of Graphite deposition: (u) 0.5 mAh / cm -2 ; (v) 1 mAh / cm -2 ; (w)

[0072] 3 mAh / cm -2 ; (x) 5 mAh / cm -2 .

[0073] Figure 23 These are SEM images of the negative electrode material at different lithium deposition amounts under the -20°C low temperature condition in Example 3 of the present invention. SEM images of pure MXene deposition: (a) 0.5 mAh / cm -2 ; (b) 1 mAh / cm -2 ; (c) 3 mAh / cm -2 ; (d)

[0074] 5 mAh / cm -2 . SEM images of MXene-configurated graphite deposition: (e) 0.5 mAh / cm -2 ; (f) 1 mAh / cm -2 ; (g) 3 mAh / cm -2 ; (h) 5 mAh / cm -2 . SEM images of MXene(1%)-graphite deposition: (i)

[0075] 0.5 mAh / cm -2 ;(j) 1 mAh / cm -2 ;(k) 3 mAh / cm -2 ;(l) 5 mAh / cm -2 。SEM images of MXene(5%)-graphite deposition: (m) 0.5 mAh / cm -2 ;(n) 1 mAh / cm -2 ;(o) 3 mAh / cm -2 ;(p) 5 mAh / cm -2 。SEM images of Graphene-graphite deposition: (q) 0.5 mAh / cm -2 ;(r) 1 mAh / cm -2 ;(s) 3 mAh / cm -2 ;

[0076] (t) 5 mAh / cm -2 。SEM images of Graphite deposition: (u) 0.5 mAh / cm -2 ;(v) 1 mAh / cm -2 ;(w)

[0077] 3 mAh / cm -2 ;(x) 5 mAh / cm -2 。

[0078] Figure 24 dQ / dV plots of graphite and modified graphite at -20 °C. (a) MXene-configurated graphite; (b) MXene(1%)-graphite; (c) MXene(5%)-graphite; (d) Graphene-graphite;

[0079] (e) Graphite; (f) Statistical results of voltage differences between charge and discharge platforms.

[0080] Figure 25Electrochemical performance of the MXene interface-reconstructed graphite anode Ah-level soft-pack battery under extreme conditions in Example 3 of the present invention; among them, (a) Schematic diagram of the MXene interface-reconstructed graphite||NCM811 soft-pack battery structure and design of the in-situ pressure monitoring device; (b-c) At -20°C, the stress fluctuation and long-cycle performance of the MXene interface-reconstructed graphite anode soft-pack battery show that the stress fluctuation is negligible and the cycle stability is excellent. After 1200 cycles at -20°C, the capacity retention rate of MXene interface-modified graphite is 2.2 times that of unmodified graphite; (d) Comparison of the energy density of the soft-pack battery and comparison with the performance of soft-pack batteries reported in other literatures show that it has the highest energy density retention rate in the wide temperature range from -20°C to 40°C.

[0081] Figure 26 Long-cycle performance at a 1C rate of graphite and modified graphite under the low-temperature condition of -20°C in Example 3 of the present invention.

[0082] Figure 27 Long-cycle performance of the soft-pack batteries with MXene interface-reconstructed graphite, MXene-graphite mixture, and graphite anodes of the present invention at 25°C and 10C.

[0083] Figure 28 Multiple functions of the MXene interface in the MXene interface-reconstructed graphite of the present invention. Detailed implementation manners

[0084] The technical solutions of the present invention are described below through specific examples. It should be understood that one or more steps mentioned in the present invention do not exclude the existence of other methods and steps before and after the combined steps, or other methods and steps can be inserted between these clearly mentioned steps. It should also be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. Unless otherwise specified, the numbers of each method step are only for the purpose of identifying each method step, rather than limiting the arrangement order of each method or defining the implementation scope of the present invention. The change or adjustment of their relative relationship can also be regarded as the scope in which the present invention can be implemented under the condition of no substantial change in technical content.

[0085] There are no specific restrictions on the sources of the raw materials and instruments used in the examples, and they can be purchased in the market or prepared according to the conventional methods well-known to those skilled in the art.

[0086] Example 1

[0087] This example provides an interface-reconstructed graphite anode material and method. As shown in Figure 1 (a), the implementation steps include:

[0088] 1) Graphite amination: The graphite material is subjected to amination treatment so that the surface of the graphite material contains amino functional groups, and aminated graphite is obtained. In this process, a large number of positively charged amino (-NH2) groups are introduced onto the graphite surface. In this embodiment, 3-aminopropyltrimethoxysilane (APS) is grafted onto the graphite, thereby generating positively charged amino (-NH2) groups on the graphite surface.

[0089] 2) Electrostatic adsorption: Electrostatic interaction between positively charged modified graphite and negatively charged MXene. In this embodiment, the aminated modified graphite (APS-graphite) and MXene are mixed and dispersed in an aqueous solvent, then solid-liquid separation is carried out, and then drying treatment is performed. The MXene is obtained by etching the A layer in the MAX phase with a fluorine-containing etching solution, and after washing, exfoliating, and solid-liquid separation; in some embodiments, the fluorine-containing etching solution is a hydrofluoric acid (HF) solution or a mixture of a fluoride salt and an acid, and the obtained MXene has a two-dimensional sheet morphology and a surface rich in hydroxyl (-OH) and oxygen (-O) functional groups, making the surface of the MXene sheet negatively charged. Figure 1 b to d respectively give the surface zeta potentials of graphite, APS-graphite, and MXene. The results show that the zeta potential of APS-graphite is +6.5 mV, while the zeta potential of MXene is -29.7 mV, which means that the MXene layer will spontaneously adsorb onto the surface of APS-graphite through electrostatic interaction.

[0090] When negatively charged MXene is mixed with positively charged aminated graphite in a solution, the two-dimensional ultrathin MXene layer spontaneously adsorbs onto the graphite surface through electrostatic interaction, thereby forming a unique sandwich structure, as Figure 2 shown in a, the graphite is sandwiched between two MXene interfacial layers, forming a heterostructure of MXene-graphite-MXene (referred to as MXene interfacial reconstructed graphite in the present invention). Fourier transform infrared spectroscopy ( Figure 2 b) tests of graphite and APS-graphite show that the wavelength range is 4000 to 600 cm -1 , and the main characteristic peaks at 1594, 1350, 1086, and 760 cm -1 are respectively assigned to the stretching or bending vibrations of -NH2, C-N, Si-O-Si, and Si-H / -NH2, indicating that the APS component has been successfully grafted onto the graphite surface.

[0091] As Figure 2As shown in the schematic diagram, a MXene interface layer is formed by many single or multiple MXene sheets adhering to the graphite substrate surface. Therefore, the MXene interface layer has an ultra-thin thickness, which is the thickness of single or multiple MXene sheets. The thickness of the MXene sheets can be measured by atomic force microscopy (AFM) (about 1 - 10 nm). Preferably, the thickness of the MXene interface layer is between 1 - 10 nm. When the single MXene sheet is a single-atom-layer MXene, AFM measurement shows that the thickness of the MXene sheet is about 1 - 3 nm. For example, in the embodiments of the present invention, the thickness of the MXene sheet measured is only 2 nm( Figure 4 b). That is, when the MXene interface layer is only formed by single-atom-layer MXene adhering to the graphite substrate surface, the ultra-thin thickness of the MXene interface layer of the MXene interface-reconstructed graphite in the present invention is 1 - 3 nm.

[0092] Example 2

[0093] This example provides a specific MXene interface-reconstructed graphite and implementation method, where MXene is Ti3C2T x , which is obtained by using MAX phase Ti3AlC2 as the precursor (produced by Jinan Sanchuan New Material Technology Co., Ltd.) and lithium fluoride (LiF) and hydrochloric acid (HCl) as etching agents to etch the Al layer in Ti3AlC2. The more specific preparation method steps include: immersing 1 g of Ti3AlC2 powder into a mixture containing 40 mL of 12 M HCl and 3.2 g of LiF, and heating at 35 °C for 24 hours under magnetic stirring. The suspension is repeatedly washed with deionized water and ultrasonic waves for several hours, and after centrifugation, a Ti3C2T x dispersion is obtained.

[0094] The method for interface-reconstructed graphite includes the steps of:

[0095] (1) Graphite amination: Disperse 1 g of graphite particles in 100 mL of APS aqueous solution (0.15 mg mL -1 ), then stir at 60 °C for 12 hours, and finally wash with deionized water for several cycles to synthesize APS-modified graphite (APS-graphite).

[0096] (2) MXene interface reconstruction: Drop 50 mL of MXene aqueous solution (0.2 mg mL -1 ) into 100 mL of APS-modified graphite aqueous solution (10 mg mL -1 ), stir for 2 hours to obtain a MXene interface-reconstructed graphite dispersion, then perform solid-liquid separation, and after vacuum drying, obtain MXene interface-reconstructed graphite.

[0097] Figure 3a shows a comparison of the optical photographs of the MXene-graphite mixture (left) and the MXene interface-reconstructed graphite (right) dispersions, and obvious precipitation can be seen due to the electrostatic interaction between MXene and APS-modified graphite. Thermogravimetric analysis (TGA) of the MXene-reconstructed graphite in air shows that it is completely oxidized to titanium dioxide (TiO2) when the temperature gradually rises to 1400 °C, with a weight loss of 98.72%. It can be deduced from the relative molar masses of MXene and TiO2 that the content of MXene is approximately ~1%( Figure 3 b).

[0098] To better illustrate the unique sandwich structure of the MXene interface-reconstructed graphite of the present invention, the morphology of the product was characterized. The scanning electron microscope (SEM) image of the MXene interface-reconstructed graphite observed from the side clearly shows that the MXene interface-reconstructed graphite has a sandwich-like MXene-graphite-MXene structure( Figure 4 c). The planar size of the MXene sheets is between 0.5 - 4 μm( Figure 4 a), and the thickness is about 2 nm( Figure 4 b); the particle size range of the graphite particles is between 100 microns and 1000 microns, and the average particle size is approximately ~307 μm( Figure 4 c). The size of the negatively charged MXene sheets is significantly smaller than that of the graphite particles, and the vast majority of the MXene sheets will be adsorbed on the basal plane of the positively charged APS-graphite. This can be proven by the particle size distribution of the MXene interface-reconstructed graphite (average particle size of ~312 μm) being close to that of graphite( Figure 4 c).

[0099] Through high-resolution transmission electron microscopy (HRTEM), it can be clearly seen that the MXene interface layer is located on the surface of the graphite and forms a sandwich structure( Figure 5 ), and the MXene interface layer (shown by the orange dotted line) has an ultra-thin thickness of only about ~1 nm, indicating that the MXene interface layer is a single-atom layer of MXene. Combining with the cross-sectional transmission electron microscopy image (TEM)( Figure 6 ) clearly shows the elemental distribution of Ti on both sides and C in the middle, confirming that the MXene interface-reconstructed graphite of the present invention has a sandwich-like MXene-graphite-MXene heterostructure. The MXene sheets are mainly adhered to the basal plane of the graphite, providing effective interface reconstruction for the interface of the graphite.

[0100] Calculations by density functional theory (DFT) show that this interface reconstruction from carbon to MXene will greatly increase the Li adsorption energy to -3.41 eV, approximately 3 times that of pure graphite (-1.03 eV)( Figure 7 ). The experimental results show that the nucleation overpotential of the MXene interface (|ηn is only 12 mV, about one-fourth of pure graphite (42 mV). Based on classical nucleation theory (ΔGn* ∝ z|η n |, where z is the charge of the cation), due to the Li nucleation energy barrier (ΔG n *) being proportional to the overpotential, the MXene interface will undoubtedly lower the Li nucleation energy barrier and effectively promote the uniform nucleation of Li on the MXene interface-reconstructed graphite anode material.

[0101] To gain in-depth understanding of the lithium deposition behavior on the MXene (Ti3C2T x ) interface, cryogenic transmission electron microscopy (cryo-TEM) was performed after different deposition capacities from 0.3 to 0.7 mAh cm -2 . ( Figure 8 and Figure 9 b, c). As shown in Figure 9 b, at a deposition capacity of 0.3 mAh cm -2 , some isolated grains with diameters of 10 - 20 nm were observed on the interface layer. When the deposition capacity increased to 1.0 mAh cm -2 , a large amount of metallic lithium grew uniformly on the MXene interface layer without visible dendritic lithium ( Figure 9 c). It is worth noting that the deposited metallic lithium is entirely body-centered cubic bcc Li, and most of the exposed crystal planes are (110) crystal planes with a lattice spacing of ( Figure 9 d, e). This is in contrast to the dendritic lithium that grows randomly along multiple planes of (110), (200), or (211) on the carbon layer surface ( Figure 10 ). Through in-situ X-ray diffraction (XRD) measurements, the preferential growth of lithium along the (110) plane on the MXene interface can be further demonstrated. As the lithium deposition capacity increases to 10 mAh cm -2 , the intensity of the (110) plane gradually increases ( Figure 11 ), which does not exist in the cases of graphite and Cu-Li anodes.

[0102] To further clarify the stacking mode of lithium atoms along the horizontal or vertical direction on the MXene interface during the lithium deposition process, DFT calculations were carried out. In Figure 9 g, for horizontal accumulation, the adsorption energy of MXene Ti3C2T x is -3.05 eV, much higher than the adsorption energies of pure Li (-1.65 eV), graphene (-1.46 eV), and copper (-2.33 eV). In contrast, for vertical accumulation, MXene Ti3C2T xThe adsorption energy is -0.33 eV, which is much lower than that of pure Li (-1.01 eV), graphene (-1.54 eV) and copper (-1.01 eV). Driven by the difference in adsorption energy, lithium has an obvious horizontal growth trend on the MXene interface, which may solve the technical problem of the vertical growth of dendritic lithium on pure lithium and many other substrates.

[0103] To further understand the Li deposition mechanism at the MXene interface, the lattice compatibility between the lithium electrodeposited along different planes and the reconstructed graphite of the MXene interface was calculated by the Bramfitt two-dimensional mismatch formula:

[0104]

[0105] In the formula represents the lattice mismatch between the exposed plane of the two-dimensional (2D) material and the (hkl) crystal plane of Li metal, represents the atomic spacing of the two-dimensional material along the low refractive index direction [uvw] 2D . represents the atomic spacing in the low refractive index direction of the Li (hkl) plane, and θ is the angle between the low refractive index directions [uvw] 2D and [uvw] Li . The calculation results show that the lattice mismatch between the (110) crystal plane of Li and the hexagonal crystal plane of MXene Ti3C2T x is only 7.5%, much lower than other Li planes, such as 36.5% for the (200) crystal plane, 32.4% for the (211) crystal plane, and 70.7% for the (310) crystal plane ( Figure 9 f), indicating that Li atoms are easy to densely pack in the direction of the close-packed plane (110). The plane at the MXene interface is consistent with the above low-temperature TEM and XRD analysis results. In contrast, the lattice mismatch between the (110) crystal plane of Li and the hexagonal crystal plane of graphite is as high as 39.6%, which is about 5 times that of the MXene interface. Obviously, the interface reconstruction of MXene can effectively regulate the lithium deposition behavior in the graphite anode.

[0106] In some other embodiments of the present invention, by adjusting the reaction parameters, the mass content of MXene can be preferably controlled ≤ 2 wt.%; preferably, it is between 1 and 2 wt.%; more preferably, it is between 1 and 1.5 wt.%; still more preferably, it is between 1 and 1.2 wt.%.

[0107] Example 3

[0108] This example provides an electrode sheet, a battery and their electrochemical performance containing the graphite anode material with MXene interface reconstruction of the present invention.

[0109] Preparation method of electrode sheet: A negative electrode sheet with MXene interface reconstructed graphite as the negative electrode material was prepared by the classical slurry method. Specifically, 98 wt% of MXene interface reconstructed graphite, 1 wt% of carboxymethyl cellulose (CMC) binder, and 1 wt% of conductive agent SuperP were sequentially dispersed in deionized water to form a uniform slurry. Then the slurry was coated on both sides of a copper foil (6 μm) and vacuum dried at 80 °C for 15 hours to produce the MXene interface reconstructed graphite negative electrode. After rolling, the negative electrode was cut into rectangular blocks to assemble a soft-pack battery.

[0110] Comparative Example: Graphite negative electrode (Graphite), 1% graphene and graphite mechanically mixed negative electrode (Graphene-graphite), 1% MXene and graphite mechanically mixed negative electrode (MXene(1%)-graphite), 5% MXene and graphite mechanically mixed negative electrode (MXene(5%)-graphite) were used as comparisons to further explore the fundamental reasons for the improvement of the electrochemical performance of the MXene interface reconstructed graphite negative electrode material (MXene-configurated graphite) under extreme conditions.

[0111] During the preparation of the MXene interface reconstructed graphite slurry, by adjusting the addition amount of MXene interface reconstructed graphite, this example also studied the viscosity change of the slurry with a solid content ranging from 37% to 42% ( Figure 12 ). When the solid content of the MXene interface reconstructed graphite electrode slurry is about 37%, because the viscosity of the slurry is 3451 mPa·s at this time -1 , it is in the range (2000 - 4000 mPa·s -1 ) that is beneficial to good electrode manufacturing. However, the solid content of this MXene interface reconstructed graphite slurry is much lower than that of commercial graphite electrodes (about 42%). If the solid content of MXene interface reconstructed graphite is set to about 42%, the viscosity will increase significantly to 11291 mPa·s -1 , which is much higher than the viscosity of the graphite slurry (2437 mPa·s -1 ). This high viscosity of MXene interface reconstructed graphite should be attributed to the abundant functional groups of MXene, which will produce hydrogen bond interactions with water or carboxymethyl cellulose (CMC) binder. According to the literature (J.Power Sources 2018, 397, 223), we evaluated the exfoliation strength of the MXene interface reconstructed graphite electrode. The exfoliation strength - peel elongation curve shows ( Figure 13 ) that the average exfoliation strength of the MXene interface reconstructed graphite electrode is 11.9 N m -1 , about that of the graphite electrode (7.6 N m -11.5 times that of (). Based on the high viscosity and good exfoliation strength of the slurry, our research achieved a mass loading of up to 19.3 mg cm -1 MXene interface-reconstructed graphite electrodes.

[0112] In some other embodiments, the mass loading of the MXene interface-reconstructed graphite electrode can be easily adjusted to 9, 10, 11, 12, 14, 16, 17, 18, 19, 20 mg cm according to the battery design -2 .

[0113] It should be noted that in order to obtain a lithium-ion battery with good low-temperature and high-rate performance, the graphite electrode usually has an optimal active mass loading of ≤8 mg cm -2 because too high a mass loading will have a great impact on the electron transfer and ion diffusion capabilities, resulting in large electrochemical polarization. Different from this, our MXene interface-reconstructed graphite electrode has a high mass loading of ~19.3 mg cm -2 , and due to its high viscosity, it can not only be easily fabricated by traditional slurry methods, but also has high electrical conductivity, showing excellent low-temperature performance, high-rate performance and high energy density.

[0114] The electrochemical performance of lithium-ion batteries is closely related to the transport rates of electrons and ions in the battery. As Figure 14 shown in a, MXene has excellent electronic conductivity (4545 S cm -1 ), about 17 times that of graphite (262 S cm -1 ), 12 times that of graphene (359 S cm -1 ). Correspondingly, the electronic conductivity of the MXene-configurated graphite electrode is 1084 S cm -1 , about 2 - 2.5 times that of graphite and graphene Graphene-graphite. In addition, as the content of MXene increases to 5%, the electronic conductivity of the MXene(5%)-graphite electrode also increases to 1736 S cm -1 , further confirming that introducing high-conductivity MXene into the graphite negative electrode can effectively increase the electronic conductivity of the composite electrode.

[0115] In order to evaluate the ion diffusion coefficient of the modified graphite electrode. Using graphite or modified graphite as the positive electrode and metallic lithium as the negative electrode, a half-cell was assembled, and the battery was activated for 2 cycles at a room temperature of 0.1C rate, and then the diffusion coefficient of the half-cell was tested under low-temperature (-20 °C) conditions by the galvanostatic intermittent titration method GITT technology. As Figure 15 shown in a, for a mass loading of about 3 mg cm -2For the electrode, the average Li+ diffusion coefficient of MXene interfacial reconstructed graphite at -20 °C is 8.7×10 -11 cm 2 s -1 , which is twice that of the MXene-graphite composite or mixture (3.8×10 -11 cm 2 s -1 ). As the mass loading in the electrode increases, this difference will increase significantly. At a mass loading of up to about 12 mg cm -2 , the average Li+ diffusion coefficient of MXene interfacial reconstructed graphite (with a mass loading of about 12 mg cm 2 s-1) is 2.87×10 -11 cm 2 s -1 , which is about 16 times higher than that of the MXene-graphite composite or mixture (0.17×10 -11 cm 2 s -1 )( Figure 15 b). As shown by the results of the distribution of relaxation times (DRT) measurements in Figure 15 c, where at -20 °C, the peak (about 48 s) related to Li+ diffusion (R diff-Gr ) in the MXene interfacial reconstructed graphite negative electrode is 971 Ωs -1 , much lower than that of the MXene-graphite composite or mixture (6962 Ωs -1 ), clearly indicating that MXene interfacial reconstructed graphite has a higher Li+ diffusion coefficient at low temperatures.

[0116] On the one hand, the high ionic diffusion coefficient of the MXene-configurated graphite electrode stems from the fact that the reaction between the MXene interface and lithium generates a SEI film rich in LiF with a high ionic diffusion rate (where the surface diffusion rate of LiF ions is ~3×10 -3 Scm -1 )( Figure 16 ). On the other hand, as shown in Figure 17 , Graphene-graphite, MXene(1%)-graphite, MXene(5%)-graphite will wrap the graphite as a whole, and this lamellar wrapping structure will have a "steric effect" on the transport of lithium ions, significantly increasing the ion transport path; while in MXene-configurated graphite( Figure 17 c), the MXene sheets mainly adhere to the basal plane of graphite and do not block the intercalation and deintercalation of ions on the edge plane.

[0117] In addition, the activation energy of the MXene interfacially reconstructed graphite electrode (49.0 kJ mol -1 , Figure 18 a) is lower than that of graphite (58.5 kJ mol -1 ). Therefore, at a typical low temperature of -20 °C, the half-cell with the MXene interfacially reconstructed graphite anode shows much lower electrochemical polarization ( Figure 18 b, the potential difference between the lithiation / delithiation peaks is 138 mV) than that of the pure graphite anode (223 mV). At -20 °C, the MXene interfacially reconstructed graphite anode has a high specific capacity of 298 mAh g -1 , accounting for 81% of the capacity at room temperature (365 mAh g -l ).

[0118] To further investigate the reason for the enhanced electrochemical performance of the MXene interfacially reconstructed graphite anode at low temperatures, in-situ dynamic capacitance measurements (DCM) were carried out. At -20 °C, the onset time of lithium deposition on the MXene interfacially reconstructed graphite anode is 19549 s, much later than that of the pure graphite anode (14449 s), indicating that the MXene interface can effectively delay the initial time of lithium deposition. In addition, the slope of the capacitance Cs change of the MXene interfacially reconstructed graphite anode with lithium deposition time is lower, at 0.8×10 -6 , only one-fifth of that of the graphite anode (4.2×10 -6 , Figure 18 c). According to the literature on DCM tests, the slope is positively correlated with the electrochemically active surface area of lithium deposition on the electrode. This can be further demonstrated by the SEM images of the MXene interfacially reconstructed graphite after discharging from 100% to 200% state of charge (SoC), where all electrode surfaces are smooth ( Figure 19 ). In contrast, many lithium dendrites were observed on the pure graphite electrode, similar to the graphite anodes reported under extreme conditions. It should be noted that the excessive lithium deposition on the MXene interfacially reconstructed graphite anode (200% SoC) provides a high I Figure 20 / I (110) / I (200) value of 3.8 in the XRD pattern ( Figure 20 ), almost three times that of the pure graphite anode (1.1), which is highly consistent with the dominant (110) observation obtained from the low-temperature TEM images and DFT calculations above. According to the reported lithium anodes, the most densely packed (110) plane of Li has the lowest migration energy barrier of 0.11 J m -2 , with good reversibility. After 100 cycles of lithium electrodeposition / stripping, the surface of the MXene interfacially reconstructed graphite anode is still smooth, without any silver-white dead lithium, which mainly exists on pure graphite ( Figure 21 ).

[0119] This example further evaluated the morphology of lithium nucleation and growth on the modified graphite anode under room temperature ( Figure 22 ) and low temperature ( Figure 23 ). The above-mentioned half-cells were respectively deposited with metallic lithium with a capacity of 0.5 - 5 mAh cm -2 at a current density of 0.5 mA cm -2 . Then, the electrode sheets were disassembled, washed, dried, and finally the morphology of the microscopic region was observed by SEM. As Figure 22 shows, at room temperature, metallic lithium grows horizontally along the two-dimensional nanosheets, then grows into pebble-like lithium particles, and finally covers the entire electrode surface. No obvious lithium precipitation was observed on the surface of MXene-configurated graphite at 1 mAh cm -2 , and flat plate-like metallic lithium was observed at 3 mAh cm -2 . Different from MXene-configurated graphite, horizontally growing metallic lithium with a diameter greater than 20 μm was precipitated on MXene(1%)-graphite at 3 mAh cm -2 ; horizontally growing metallic lithium was already precipitated on MXene(5%)-graphite at 1 mAh cm -2 . While lithium dendrites were already precipitated on Graphene-graphite and the graphite anode at 1 mAh cm -2 . Under the low temperature condition of -20 °C, spherical metallic lithium with a diameter of about 2 μm was formed on the surface of MXene at 1 mAh cm -2 , and the metal particles on MXene gradually became larger with the increase of the deposition amount. Similar to room temperature, no obvious metallic lithium was observed on the surface of MXene-configurated graphite at 1 mAh cm -2 , pebble-like metallic lithium was formed on the surface of MXene(5%)-graphite at 1 mAh cm -2 , and the graphite anodes added with MXene all showed a dense deposition morphology at 1 mAh cm -2 . While obvious lithium dendrites were precipitated on Graphene-graphite and the graphite anode. In summary, different from the precipitation of lithium dendrites on the surfaces of graphene-modified graphite and pure graphite, the MXene interface can achieve controllable lithium precipitation on the graphite anode both at room temperature and low temperature.

[0120] In addition, the dQ / dV diagram of the modified graphite half-cell at -20 °C and 0.05 C shows that ( Figure 24) The voltage difference between the charge and discharge platforms of the MXene-configurated graphite is 26.8 mV, which is lower than that of MXene(1%)-graphite(33.4 mV), MXene(5%)-graphite(46.5 mV), Graphene-graphite(49.7 mV) and Graphite(58.3 mV), confirming that MXene-configurated graphite can effectively alleviate the electrochemical polarization inside the battery.

[0121] In summary, when lithium ions are deposited on the surface of MXene-interface reconstructed graphite to form metallic lithium, a metallic lithium / graphite composite material is obtained. Metallic lithium preferentially deposits and grows along the two-dimensional MXene sheets of the MXene interface layer, gradually forming pebble-like lithium particles, and finally covering the entire electrode surface.

[0122] Example 4

[0123] Based on the above research, in this example, graphite and modified graphite were assembled with the cathode material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) to assemble an Ah-level soft-pack battery ( Figure 25 a, c), and a constant current (CC)-constant voltage (CV) charging protocol was used to test the long-cycle performance at low temperature. As is well known, stress change is an important factor in evaluating commercial lithium-ion batteries. In this example, an in-situ pressure monitoring device ( Figure 25 a) was also assembled to evaluate the stress fluctuations in the soft-pack battery with an MXene-interface reconstructed graphite anode. At -20 °C, small stress fluctuations with an average pressure increase of 0.12 kPa were observed ( Figure 25 b), which is 5% of that of the pure graphite anode battery (2.37 kPa), clearly indicating that the volume change of our soft-pack battery during low-temperature cycling can be negligible. Such low stress fluctuations are beneficial for long-cycle performance under extreme conditions (including low temperature and high rate). When cycling at 1C@-20 °C, the energy density is as high as 273 Wh kg -1 , which is 84% of the cycling energy density at room temperature (324 Wh kg -1 ). It is worth noting that after cycling 1200 times at low temperature, the capacity retention rate is as high as 93% ( Figure 25 c). In contrast, under the same test conditions, the soft-pack battery with a pure graphite anode shows a relatively low energy density (191 Wh kg -1 ) and capacity retention rate (43%). Existing lithium-ion batteries under similar conditions (144 - 176 Wh kg -1 , Figure 25d). Additionally, at room temperature of 25 °C and a high rate of 10 C, our soft-pack batteries still exhibit a remarkable capacity retention rate of 94% after 1200 cycles and an energy density of 287 Wh kg -1 which is superior to that of pure graphite anode batteries and reported lithium-ion batteries (180 - 265 Wh kg Figure 25 d), -1 ).

[0124] As Figure 26 shown, at -20 °C and a rate of 1 C, the soft-pack batteries with MXene interface reconstructed graphite can stably cycle 1200 times, and its capacity retention rate (93%) is far superior to that of MXene (1%)-graphite (71%), MXene (5%)-graphite (63%), Graphene-graphite (54%) and Graphite (55%). Additionally, at room temperature of 25 °C and a rate as high as 10 C, the soft-pack batteries with MXene interface reconstructed graphite still show a remarkable capacity retention rate of 94% after 1100 cycles, which is superior to that of the batteries with MXene-graphite mixture (81%) and graphite anode (54%) Figure 27 ).

[0125] In summary, the MXene interface in MXene-configurated graphite is a multifunctional interface Figure 28 ), and its main functions include: ① The MXene interface can enhance the electronic conductivity of the anode (1084 S cm -1 ); ② The MXene interface has a high adsorption performance for lithium ions (-3.41 eV), which can effectively reduce the nucleation barrier of Li in the anode; ③ The MXene interface can induce the formation of a LiF-rich SEI film, which can promote the transport of lithium ions; ④ The MXene interface has good lattice compatibility with the deposited lithium, which is beneficial to the formation of body-centered cubic Li that grows horizontally and densely packed along the (110) crystal plane under extreme conditions.

[0126] It should be noted that the graphite used in the examples is natural flake graphite purchased from the market. Using other types of graphite or anode materials with a graphite structure is also included in the scope of the present invention. Since MXene is a type of two-dimensional material with similar material properties, the MXene Ti3C2T x in this example can be replaced by MXene materials M n+1 X n T x, wherein the transition metal element M is selected from one or more of elements such as Ti, V, Nb, Ta, Zr, W, Mo, Cr, etc., the non-metal element X is selected from one or more of the elements C, N, B, T represents a surface group (such as -F, -Cl, -OH, -O, etc.), 1 ≤ n ≤ 4, 0 < x ≤ 2, by using T x It means that the surface has functional groups.

[0127] In materials science, the "basal plane" specifically refers to the crystal plane parallel to the main layer in a layered crystal. For example, the basal plane of graphite refers to the crystal plane parallel to the graphite layer direction; it is contrasted with the "prismatic plane" or "end face" (such as the (100), (110) planes of graphite, the crystal plane perpendicular to the layer edge).

[0128] The foregoing description of the specific exemplary embodiments of the present invention is for purposes of illustration and exemplification. These descriptions are not intended to limit the invention to the precise forms disclosed, and obviously, many changes and variations are possible in light of the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the invention and its practical applications, so that those skilled in the art can implement and utilize the various different exemplary embodiments of the present invention, as well as various different selections and changes. The scope of the present invention is intended to be defined by the claims and their equivalents.

Claims

1. A preparation method of MXene interface-reconstructed graphite, characterized in that the steps Comprising: Aminating a graphite material to make the surface of the graphite material contain amino functional groups, obtaining aminated graphite; Mixing and dispersing the aminated graphite and MXene in a solvent, and through electrostatic adsorption, forming an MXene interfacial layer on the basal plane of the graphite to obtain MXene interfacial reconstructed graphite with a sandwich-like MXene-graphite-MXene heterostructure.

2. The preparation method according to claim 1, characterized in that, The specific steps of the amination treatment include: treating the graphite material with an amino silane coupling agent; more specific steps include: mixing and treating the graphite material with an aqueous solution of the amino silane coupling agent; Preferably, the amino silane coupling agent is selected from one or more of: aminopropyltrimethoxysilane (APS), γ-aminopropyltriethoxysilane (KH-550), β-aminoethyltrimethoxysilane (KH560), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH602), 3-aminopropyltriethoxysilane (APTES), N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, bis(3-triethoxysilylpropyl)amine, N-cyclohexyl-γ-aminopropylmethyldimethoxysilane (KH612), bis(triethoxysilylpropyl)amine (GX-552), N-n-butyl-3-aminopropyltrimethoxysilane.

3. The preparation method according to claim 1, characterized in that, The MXene contains fluorine, hydroxyl, and oxygen functional groups; And / or, the Zeta potential of the MXene is negative, and the Zeta potential of the aminated graphite is positive; And / or, the elemental characterization of the MXene interfacial reconstructed graphite shows that it includes: carbon, oxygen, fluorine, and transition metal elements; preferably, the transition metal elements are selected from one or more of Ti, V, Nb, Ta, Zr, W, Mo, Cr; And / or, the particle size range of the MXene interfacial reconstructed graphite is between 100 and 1000 microns; And / or, the size of the MXene sheets is between 0.5 and 4 microns; And / or, the thickness of the MXene sheets is between 1 and 10 nm, preferably between 1 and 3 nm; And / or, the content of MXene in the MXene interfacial reconstructed graphite is ≤2 wt.%, preferably between 1 and 2 wt.%; more preferably between 1 and 1.5 wt.%, and still more preferably between 1 and 1.2 wt.%; And / or, the thickness of the MXene interfacial layer in the MXene interfacial reconstructed graphite is between 1 and 10 nm, preferably 1 to 3 nm; And / or, the MXene interfacial layer in the MXene interfacial reconstructed graphite is the thickness of a single or several MXene sheets; And / or, the preparation method of the MXene includes: first etching the A layer in the MAX phase with a fluorine-containing etching solution, and obtaining it after washing, exfoliating, and solid-liquid separation; preferably, the fluorine-containing etching solution is a hydrofluoric acid solution or a mixture of a fluoride salt and an acid; more preferably, the fluorine-containing etching solution is a mixture of lithium fluoride and hydrochloric acid.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The steps also include: solid-liquid separation and drying treatment to obtain a powder of the MXene interfacial reconstructed graphite; And / or, a purification step, in which the obtained dispersion of MXene interfacially reconstructed graphite in the aqueous solvent is washed and purified to obtain an aqueous dispersion of MXene interfacially reconstructed graphite.

5. MXene interfacially reconstructed graphite powder obtained by the preparation method according to any one of claims 1 to 4, or an aqueous dispersion of MXene interfacially reconstructed graphite.

6. A MXene interface-reconstructed graphite, characterized in that, MXene sheets form an MXene interface layer on the basal plane of graphite, and the MXene interfacially reconstructed graphite has a sandwich-like MXene-graphite-MXene heterostructure.

7. The MXene interface-reconstructed graphite according to claim 6, wherein, Characterization of the MXene interfacially reconstructed graphite shows that it includes carbon, oxygen, fluorine, and transition metal elements; preferably, the transition metal element is selected from one or more of Ti, V, Nb, Ta, Zr, W, Mo, Cr; And / or, the MXene sheets form an MXene interface layer on the basal plane of the graphite through electrostatic adsorption; And / or, the conductivity of the MXene interfacially reconstructed graphite is more than 2 times that of pure graphite; preferably, it is 2 to 2.5 times; And / or, the content of MXene in the MXene interfacially reconstructed graphite is ≤2 wt.%, preferably, it is between 1 and 2 wt.%; more preferably, it is between 1 and 1.5 wt.%, still more preferably, it is between 1 and 1.2 wt.%; And / or, the particle size range of the MXene interfacially reconstructed graphite is between 100 and 1000 microns; And / or, the size of the MXene sheets is between 0.5 and 4 microns; And / or, the thickness of the MXene sheets is between 1 and 10 nm, preferably, the thickness is between 1 and 3 nm; And / or, the thickness of the MXene interface layer in the MXene interfacially reconstructed graphite is between 1 and 10 nm, preferably, the thickness is 1 to 3 nm; And / or, the thickness of the MXene interface layer in the MXene interfacially reconstructed graphite is the thickness of a single or several MXene sheets; And / or, the thickness of the MXene interface layer in the MXene interfacially reconstructed graphite is between 1 and 10 nm, preferably, the thickness is 1 to 3 nm; And / or, metallic lithium preferentially grows along the (110) plane on the MXene interface of the MXene interfacially reconstructed graphite; And / or, lithium ions can deposit on the MXene interfacially reconstructed graphite to form metallic lithium with a body-centered cubic lattice structure, and the exposed crystal plane of the metallic lithium is the (110) crystal plane.

8. A lithium metal / graphite composite material, characterized in that, MXene interfacially reconstructed graphite obtained by the preparation method according to any one of claims 1 to 4, or MXene interfacially reconstructed graphite according to claim 6 or 7; and metallic lithium on the surface of the MXene interfacially reconstructed graphite; Preferably, the metallic lithium is on the surface of the MXene interface layer; and / or, the crystal lattice structure of the metallic lithium is body-centered cubic; and / or, the exposed crystal plane of the metallic lithium is the (110) crystal plane; and / or, the lattice spacing of the metallic lithium is and / or, the metallic lithium microscopically presents a pebble-like particle morphology.

9. A battery electrode, characterized in that, The battery electrode contains MXene interfacially reconstructed graphite obtained by the preparation method according to any one of claims 1 to 4, or MXene interfacially reconstructed graphite according to claim 6 or 7, or the metallic lithium / graphite composite material according to claim 8.

10. The battery electrode according to claim 9, characterized in that, The mass loading density of the MXene interface-reconstructed graphite in the battery anode is greater than 8 mg cm -2 , more preferably, between 8 and 20 mg cm -2 ; even more preferably, between 10 and 19.3 mg cm -2 ; And / or, when the battery electrode serves as the negative electrode of a lithium-ion battery, lithium ions deposit on the MXene interface-reconstructed graphite as metallic lithium with a body-centered cubic lattice structure, and the exposed crystal plane of the metallic lithium is the (110) crystal plane; And / or, the average exfoliation strength of the battery electrode is more than 1.5 times that of a graphite electrode; and / or, the deposition capacity of metallic lithium in the battery electrode ranges from 1 to 10 mAh cm -2 , and no lithium dendrites are formed.

11. A method for preparing a battery electrode according to claim 9 or 10, characterized in that the steps Comprising: Mix the MXene interface-reconstructed graphite, binder, conductive agent and solvent to form a slurry, and then coat it on a current collector; preferably, the solid content in the slurry is ≥37%, preferably ≥38%, more preferably ≥39%; even more preferably, ≥42%; And / or, the viscosity of the slurry ≥ 2000 mPa·s -1 , preferably, ≥ 3451 mPa·s -1 , more preferably, ≥ 4700 mPa·s -1 , even more preferably, ≥ 5954 mPa·s -1 , still preferably, ≥ 11291 mPa·s -1 .

12. The preparation method according to claim 11, characterized in that, The binder contains hydrogen bonds and the solvent contains water; preferably, the binder is carboxymethyl cellulose; And / or, the solid content in the slurry ranges from 37% to 42%; And / or, the viscosity of the slurry is between 2000 and 12000 mPa·s -1 ; preferably, between 3451 and 11291 mPa·s -1 ; more preferably, between 4700 and 11291 mPa·s -1 , even more preferably, between 5954 and 11291 mPa·s -1 .

13. A battery, characterized in that, The battery contains the battery electrode as claimed in claim 9 or 10, or the battery electrode obtained by the preparation method as claimed in claim 11 or 12.

14. An electricity-using or electricity-storing device, characterized in that, Containing the battery as claimed in claim 13.

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