Preparation and application of metal hydride used as lithium ion battery negative electrode material

Abstract

The invention relates to preparation and application of a metal hydride serving as a lithium ion battery negative electrode material. The lithium ion battery negative electrode material is obtained by mixing Ti3C2 and MgH2 serving as raw materials and then carrying out dehydrogenation-hydrogenation treatment. Compared with the prior art, the lithium ion negative electrode material provided by the invention is simple in preparation method, and the obtained product is high in purity, uniform in size distribution and good in electrochemical performance, and can be further applied to the fields of battery materials, supercapacitors and the like.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion anode material preparation technology, and relates to the preparation and application of a metal hydride as a lithium-ion battery anode material. Background Technology

[0002] Recently, two-dimensional (2D) transition metal carbides / nitrides (commonly known as MXenes) have attracted considerable attention in energy storage systems, including supercapacitors, lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and lithium-oxygen batteries. This interest stems from their unique physicochemical properties, such as abundant surface functional groups (-O, -OH, -F), intrinsic hydrophilicity, and tunable electronic properties, while maintaining metallic conductivity. Compared to traditional carbon-based materials, MXenes possess a dual function, serving as both the active component in electrodes and a conductive matrix. For example, MXene-based electrodes exhibit excellent pseudocapacitive properties, enabling stable operation at high current densities.

[0003] For example, Chinese patent application CN202510271068.1 provides a high-rate, high-capacity MXene-based composite anode material. The nano-silicon distributed within the pores of the MXene-based composite anode material can effectively increase the sodium storage active sites, thereby improving the sodium storage capacity of the MXene-based composite anode material. The MXene-based composite anode material has a large interlayer spacing, which is conducive to the shuttle of sodium ions between MXene layers and can improve the sodium ion insertion / extraction kinetics. The nitrogen-containing nano-carbon embedded between the layers of the MXene-based composite anode material has high conductivity, which can effectively alleviate the accumulation phenomenon between MXene layers, form a stable and continuous electron transport network, and improve electron transport kinetics. Due to the synergistic improvement of ion transport and electron transport, the MXene-based composite anode material has good rate performance.

[0004] However, MXene's initial specific surface area is small, resulting in a lack of active sites in the electrode material and a low theoretical lithium storage capacity. Furthermore, the collapse of its layered structure during lithium-ion insertion / extraction poses a significant challenge to the electrode material during cycling, reducing the reaction kinetics of lithium-ion storage and increasing the diffusion distance of lithium ions during charge and discharge, thus leading to electrode pulverization and capacity reduction. These problems slow down lithium-ion storage kinetics, resulting in a decline in the electrochemical performance of MXene anode materials. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing and applying metal hydrides as negative electrode materials for lithium-ion batteries, which exhibits high reversible discharge capacity and excellent electrochemical performance.

[0006] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a metal hydride for use as a negative electrode material for lithium-ion batteries, which is obtained by mixing Ti3C2 and MgH2 as raw materials and then performing dehydrogenation-hydrogenation treatment.

[0007] In a second aspect, the present invention provides a method for preparing a metal hydride as a negative electrode material for a lithium-ion battery, comprising the following steps: S1. Nano-Ti3C2 is added to MgH2, and then ball-milled under an inert atmosphere to obtain a mixed powder; S2. The mixed powder obtained in S1 is subjected to a cycle of hydrogen desorption and hydrogen absorption treatment to obtain a lithium-ion battery anode material.

[0008] Furthermore, in S1, the mass ratio of nano-Ti3C2 to MgH2 is 5:1~6. Even further, the mass ratio of nano-Ti3C2 to MgH2 is 5:2.

[0009] Furthermore, in S1, the ball milling process is carried out in a planetary ball mill with a ball-to-material ratio of 35~45:1 and a rotation speed of 250~450 rpm / min.

[0010] Furthermore, the nano-Ti3C2 is obtained by etching Ti3AlC2, a MAX precursor, with a hydrofluoric acid solution. Even further, during the etching process, the mass fraction of hydrofluoric acid is 35%–45%, the etching temperature is 40–60°C, and the etching time is 30–40 hours.

[0011] Furthermore, in S2, during the hydrogen release process, the temperature is 350~450℃, and the temperature is maintained for 5-20 minutes; During hydrogen absorption, the temperature is 350~450℃, the hydrogen pressure is 2-6MPa, and the holding time is 1-3h. Furthermore, in S2, during the hydrogen release-hydrogen absorption process, the heating rate is 2-10℃ / min.

[0012] During the hydrogen desorption and resorption process, the particle size of Ti3C2 and MgH2 particles becomes finer and their distribution more uniform, resulting in an MX / MH-res composite material. Ti3C2, as a layered material, provides numerous active sites for lithium ion insertion and extraction. The presence of Ti3C2 can mitigate the volume expansion / contraction of MgH2, reducing stress caused by volume changes and maintaining electrode integrity. The increased number of -F end groups on MgH2 and Ti3C2 further enhances the stability of the composite material. Finally, the Ti3C2 / MgH2 composite material after hydrogen desorption and resorption treatment can increase the Li-ion exchange rate. + / Electron migration rate. Due to the synergistic effect of Ti3C2 and MgH2, the prepared Ti3C2 / MgH2 composite anode has a high reversible discharge capacity and exhibits better electrochemical performance.

[0013] In a third aspect, the present invention provides an application of metal hydrides as negative electrode materials for lithium-ion batteries in the preparation of lithium-ion batteries.

[0014] Compared with the prior art, the present invention has the following advantages: (1) The preparation method provided by the present invention is relatively simple, easy to operate, and has a short experimental cycle.

[0015] (2) The Ti3C2 and MgH2 particles of the present invention have finer particle size and more uniform distribution, resulting in an MX / MH-5 / 2-res composite material. Ti3C2, as a layered material, provides a large number of active sites for lithium ion insertion and extraction. The presence of Ti3C2 can alleviate the volume expansion / contraction of MgH2, reduce stress caused by volume changes, and maintain the integrity of the electrode. The increased number of -F end groups on MgH2 and Ti3C2 further increases the stability of the composite material. Finally, the Ti3C2 / MgH2 composite material after hydrogen release and re-absorption treatment can increase the Li-ion exchange rate. + / Electron migration rate.

[0016] (3) The preparation method of this invention is simple, easy to operate, and has a short experimental cycle. During the hydrogen release and re-absorption process, an MX / MH-5 / 2-res composite material is generated, and the increased number of -F end groups on MgH2 and Ti3C2 further enhances the stability of the composite material. Due to the synergistic effect of Ti3C2 and MgH2, the prepared Ti3C2 / MgH2 composite anode exhibits high reversible discharge capacity and better electrochemical performance. It can be applied to battery materials and supercapacitors, and has excellent performance. Attached Figure Description

[0017] Figure 1 The X-ray diffraction (XRD) patterns of the composite materials MX / MH-5 / 1, MX / MH-5 / 2, MX / MH-5 / 2-res, MX / MH-5 / 3, and MX / MH-5 / 4 prepared in Example 1 are shown.

[0018] Figure 2 SEM images of the composite materials MX / MH-5 / 1, MX / MH-5 / 2, MX / MH-5 / 2-res, MX / MH-5 / 3, and MX / MH-5 / 4 prepared in Example 1.

[0019] Figure 3 The image shows an HRTEM image of the MX / MH-5 / 2-res composite material prepared in Example 1.

[0020] Figure 4The N2 adsorption-desorption curves are for the composite materials S MX / MH-5 / 1, MX / MH-5 / 2, MX / MH-5 / 2-res, MX / MH-5 / 3, and MX / MH-5 / 4 prepared in Example 1.

[0021] Figure 5 The XPS F 1s fitting spectra of the composite materials MX / MH-5 / 1, MX / MH-5 / 2, MX / MH-5 / 2-res, MX / MH-5 / 3, and MX / MH-5 / 4 prepared in Example 1 are shown.

[0022] Figure 6 The XPS Mg 1s fitting spectra of the composite materials MX / MH-5 / 1, MX / MH-5 / 2, MX / MH-5 / 2-res, MX / MH-5 / 3, and MX / MH-5 / 4 prepared in Example 1 are shown.

[0023] Figure 7 The CV curves are for the MX / MH-5 / 2 and MX / MH-5 / 2-res composite materials prepared in Example 1.

[0024] Figure 8 The galvanostatic charge-discharge curves (GCD) of the composite materials MX / MH-5 / 1, MX / MH-5 / 2, MX / MH-5 / 2-res, MX / MH-5 / 3, and MX / MH-5 / 4 prepared in Example 1 are shown.

[0025] Figure 9 Electrochemical performance—long-cycle capacity performance and corresponding coulombic efficiency—of the MX / MH-5 / 2 and MX / MH-5 / 2-res, MX / MH-5 / 3, and MX / MH-5 / 4 composite materials prepared in Example 1 are presented. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0028] As used herein, the terms "and / or," "or / and," and "and / or" encompass any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that, in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR."

[0029] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0030] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0031] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0032] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows temperature fluctuations within the precision range controlled by the instrument, such as ±5°C, ±4°C, ±3°C, ±2°C, or ±1°C.

[0033] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0034] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0035] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0036] In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0037] Unless otherwise specified, all preparations and tests described herein took place at 25°C.

[0038] The terms “comprising,” “including,” “containing,” “having,” “comprising,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means that other steps and ingredients may be added without affecting the final result. The compositions and methods / processes of the present invention comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. No distinction is made between the terms “efficacy,” “performance,” “effect,” and “potency” herein.

[0039] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0040] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but sequentially is preferred.

[0041] In the following examples, the concentration of HF was 40 wt%, the purity of MgH2 was 98%, and the purity of the MAX precursor Ti3AlC2 was 98% and 200 mesh. There were no special requirements for MgH2 and the MAX precursor, and conventional commercially available products in the art could be used.

[0042] Example 1: This embodiment provides a method for preparing a lithium-ion battery anode material, specifically including the following steps: (S1) Under ice bath conditions, Ti3AlC2 sample (1 g) was etched for 25 min using HF (40 wt%, 20 mL) etchant. The addition process was slow to avoid generating bubbles, and a mixture was obtained. The mixture was stirred at 50℃ for 36 h, then washed with deionized water 3 times, centrifuged until the pH of the supernatant was about 6 (the speed was 5000 rpm / min and the time was 5 min during each centrifugation), and vacuum dried (80℃, 12 h) to obtain Ti3C2 powder. (S2) Mix 0.1 g of carbon powder as a grinding aid with 0.4 g of Ti3C2, with a ball-to-powder weight ratio of 30:1, and rotate at 500 rpm. -1 Nanoscale Ti3C2 was prepared by ball milling for 30 h. Then, the obtained nanoscale Ti3C2 was directly added to MgH2 at different mass ratios, and Ti3C2 / MgH2 composites were prepared by mechanical ball milling. The ball milling parameters were 400 rpm min. -1 The mixture was subjected to heat treatment for 4 hours, with a ball-to-material ratio of 40:1. The mass ratios of nano-Ti3C2 and MgH2 were 5:1, 5:2, 5:3, and 5:4, respectively, and were labeled as MX / MH-5 / 1, MX / MH-5 / 2, MX / MH-5 / 3, and MX / MH-5 / 4.

[0043] (S3) The MX / MH-5 / 2 sample with a mass ratio of 5:2 was subjected to a cycle of hydrogen release-hydrogen absorption treatment through a PCT device. During the hydrogen release process, the temperature was 400℃ and the holding time was 10 min. During the hydrogen absorption process, the temperature was 400℃, the pressure was 4 MPa, and the holding time was 2 h. The prepared sample was labeled as MX / MH-5 / 2-res.

[0044] The electrochemical energy of the prepared Ti3C2 / MgH2 composite material was tested: First, 80 mg of MX / MH-5 / 1, MX / MH-5 / 2, MX / MH-5 / 2-res, MX / MH-5 / 3, and MX / MH-5 / 4, 10 mg of conductive carbon black, and 10 mg of polymethyl methacrylate (PMMA) were weighed and placed in an agate mortar. The mixture was ground for 0.5 h under an argon atmosphere, and 300 μL of NMP solvent was added. The mixture was stirred continuously on a stirrer for 4 h to form a black slurry. Before use, the foamed copper was cleaned with anhydrous ethanol to ensure a clean and impurity-free surface. The foamed copper was then pressed using an electric roller mill. The slurry was uniformly coated onto the foamed copper using a four-sided wet film preparer, and then dried in a vacuum drying oven at 60 °C for 12 h in a water- and oxygen-free environment. Electrode sheets with a diameter of 12 mm were cut using a slicer and weighed for use. A lithium metal sheet approximately 0.4 mm thick and 14 mm in diameter was selected as the counter electrode, and coin cells were assembled in an argon-filled glove box. The oxygen content and water content inside the glove box were both below 0.01 ppm.

[0045] XRD spectrum ( Figure 1The crystal structures of MX / MH-5 / 1, MX / MH-5 / 2, MX / MH-5 / 2-res, MX / MH-5 / 3, and MX / MH-5 / 4 in the mixture are shown. From MX / MH-5 / 1 to MX / MH-5 / 4, the positions of the diffraction peaks in the XRD patterns are basically consistent, indicating that the components of the mixture are all Ti3C2 and MgH2. Figure 5-1 (b) The XRD pattern of the pure MgH2 phase shows peaks at 22.4°, 27.9°, 35.7°, and 54.7°, all corresponding to MgH2. Notably, the diffraction peak intensity of the MgH2 in the MX / MH-5 / 2-res sample increased after hydrogen desorption / absorption treatment, indicating improved crystallinity of MgH2 after this process. Furthermore, the relatively smooth, large and small "bun-like" peaks around 20° are due to the encapsulation with polymer tape. The polymer tape serves to isolate the sample from air, preventing oxidation during testing.

[0046] Figure 2 To observe the morphology of MX / MH-5 / 1, MX / MH-5 / 2, MX / MH-5 / 2-res, MX / MH-5 / 3, and MX / MH-5 / 4 using SEM, MgH2 was introduced into nano-Ti3C2 at a certain mass ratio through ball milling. It can be seen that the mixed samples after ball milling all exhibit a lamellar morphology. Samples MX / MH-5 / 1 and MX / MH-5 / 2 show an irregular aggregated structure, with small particles stacked together to form larger lamellar blocks, but MX / MH-5 / 2 has a relatively uniform overall distribution. With the increase of MgH2 content, larger nanosheet particles begin to appear in MX / MH-5 / 3 and MX / MH-5 / 4, exhibiting tight packing and forming larger agglomerated lamellars. After undergoing a hydrogen release-absorption treatment, the MX / MH-5 / 2-res sample, compared to the MX / MH-5 / 2 sample, showed a significant change in morphology. The MX / MH-5 / 2 sample had a rough surface, while the MX / MH-5 / 2-res sample had a smooth surface and more uniform particle size. Combined with... Figure 2 (f)-(j) Observing the sample morphology at low magnification can more intuitively show that the MX / MH-5 / 2-res particles after hydrogen release-absorption treatment are small, uniformly distributed, without obvious agglomeration, with clear particle boundaries and regular and orderly structure.

[0047] TEM testing was performed on the composite material to observe the local structure of the MX / MH-5 / 2-res composite. Figure 3(a) The high-resolution TEM (HRTEM) image clearly shows the lattice fringes of the nanocrystals, with a measured d-interval of 0.223 nm, corresponding to the (200) crystal plane of MgH2, indicating that the obtained nanocrystals have good crystallinity. Selected area electron diffraction (SAED) pattern ( Figure 3 (b) clearly shows the polycrystalline structure of MgH2, which is consistent with the XRD results. Figure 3 The STEM image and corresponding elemental distribution map (EDS mapping) in (c) show that Mg, Ti, and C elements are uniformly distributed in the composite material, verifying the homogeneity of the mixing of MgH2 and Ti3C2. In particular, the uniform distribution of C element also confirms that Ti3C2 maintained its structural integrity during the composite process.

[0048] Figure 4 The specific surface area and pore structure of different Ti3C2 / MgH2 composite materials were analyzed. Figure 4 (a) shows the nitrogen adsorption-desorption isotherms of Ti3C2 / MgH2 composites with different contents at 77.3 K. It can be clearly seen that the adsorption / desorption curves belong to the same type, indicating that the introduction of different masses of MgH2 did not change the pore structure. Furthermore, all composites showed low adsorption amounts in the low relative pressure region (p / p0 close to 0), gradually increasing with increasing relative pressure. Compared to MX / MH-5 / 1 (21.9 m... 2 g -1 ), MX / MH-5 / 2 (17.8 m 2 g -1 ), MX / MH-5 / 3 (13.9 m 2 g -1 ) and MX / MH-5 / 4 (12.1 m 2 g -1 MX / MH-5 / 2-res has a relatively large specific surface area of ​​35.7 m². 2 g -1 , . Figure 4 (b) is a pore size distribution diagram, further demonstrating that the pore size distribution of all composite materials is mainly concentrated in the smaller pore size region (approximately 2-10 nm), with MX / MH-5 / 2-res exhibiting a relatively large pore volume. After the pore size exceeds 10 nm, the pore volume gradually decreases, indicating that the Ti3C2 / MgH2 composite material is predominantly mesoporous. The larger specific surface area of ​​MX / MH-5 / 2-res significantly increases the number of active sites in the electrode material, thereby enhancing its energy storage capacity. The presence of the mesoporous structure facilitates rapid electrolyte penetration and shortens the Li... + The diffusion path improves the lithium-ion transport efficiency.

[0049] Figure 5 and Figure 6 This is an X-ray photoelectron spectroscopy (XPS) spectrum of the Ti3C2 / MgH2 composite material, showing the electron binding energies of C 1s, F 1s, and Mg 1s in different samples (MX / MH-5 / 1, MX / MH-5 / 2, MX / MH-5 / 2-res, MX / MH-5 / 3, MX / MH-5 / 4). All samples were prepared in a glove box and transferred to the testing stage under an inert atmosphere to avoid oxidation of MgH2. The XPS fitting data were corrected for CC (284.8 eV). By testing the valence states of Mg and F atoms in the samples, it was confirmed that MgH2 was adsorbed by F atoms in Ti3C2. The F 1s spectrum (…) Figure 5 The Mg 1s spectrum shows peaks at 685.9 and 686.7 eV, respectively, with the 685.9 eV Ti-F peak originating from the F functional group in Ti3C2. Meanwhile, the Mg 1s spectrum... Figure 6 Peaks were observed at 1304.6 and 1305.7 eV, respectively. The peak at 1304.6 eV can be attributed to the Mg-H signal. The peaks at 1305.7 and 686.7 eV are attributed to the F-Mg signal, with the F source also originating from the F functional group in Ti3C2, indicating that F-Ti3C2 has an adsorption effect on MgH2. Compared to the MX / MH-5 / 2 and MX / MH-5 / 2-res samples, the peak intensity ratio of MgF2 to MgH2 increased, indicating that in the MX / MH-5 / 2-res sample after hydrogen release-absorption treatment, the interaction between MgH2 and Ti3C2 promoted the increased bonding of fluorine atoms introduced during etching with magnesium atoms. Figure 5 It can be observed that as the proportion of MgH2 in the composite system increases, the fitting area of ​​the fluorine-magnesium bond (Ti-F-Mg) increases, indicating an increase in the fluorine content at 686.7 eV. However, in the MX / MH-5 / 2-res sample, the MgH2 content did not change compared to MX / MH-5 / 2, but the fitting area of ​​the fluorine-magnesium bond (Ti-F-Mg) showed a more significant increase. This further illustrates that the interaction between MgH2 and Ti3C2 in the MX / MH-5 / 2-res sample promotes increased bonding between fluorine and magnesium atoms. It is well known that abundant surface / interface properties are crucial for battery performance; the formed F-Mg chemical bonds will enhance the interfacial properties between Ti3C2 and MgH2, thereby affecting electrochemical performance.

[0050] The lithiation / delithiation process of MgH2, as shown in the following equation, is widely accepted: MgH2 + 2Li + + 2e - ↔ Mg + 2LiH(1) Mg + x Li + + x e - ↔ Li x Mg(2) To elucidate the electrochemical pathway of the Ti3C2 / MgH2 electrode, a voltage range of 0.01–3.0 V was used with a 0.1 mV st ratio. -1 The CV test was performed on the sample at the scanning rate. Figure 7 The CV curves of MX / MH-5 / 2-res showed a consistent shape when the MgH2 content increased to a Ti3C2 / MgH2 mass ratio of 5 / 2. Specifically, a distinct MgH2 conversion peak appeared in the anolyte CV curve within the voltage range of 0.60 V to 0.70 V. In contrast, a broad peak centered at 0.48 V was observed in the CV curve of MX / MH-5 / 1. This is mainly attributed to the Li... x The dealloying of Mg and the extraction of Li from the Ti3C2 interlayer space are observed. On the other hand, the CV curves of the MX / MH-5 / 2-res electrode show a prominent and broad cathode peak at 0.65 V in the first cycle, primarily attributed to the formation of the SEI film, the conversion of MgH2, and the intercalation of lithium into carbon. The anodic peak at 0.66 V is due to the extraction of lithium from the composite material and the regeneration of MgH2. With increasing scan cycles, only the anodic peak resulting from MgH2 regeneration shows a significant decrease. After the fourth cycle, the change in the anodic peak is negligible, and the overlap of the CV curves is satisfactory, indicating that the MX / MH-5 / 2-res electrode exhibits excellent reversibility in the electrochemical process.

[0051] Further research and comparison were conducted on MX / MH-5 / 1, MX / MH-5 / 2, MX / MH-5 / 2-res, MX / MH-5 / 3, and MX / MH-5 / 4 at a voltage range of 0.01 to 3.0 V and a current density of 0.1 A g. -1 Constant current charge-discharge curve (GCD) characteristics in the first cycle Figure 8 The initial specific discharge capacity of MX / MH-5 / 1 is significantly lower, at 680.2 mA hg. -1 In contrast, MX / MH-5 / 2, MX / MH-5 / 3, and MX / MH-5 / 4 all have higher initial specific discharge capacities (1397.9, 1674.1, and 1971.1 mA hg, respectively). -1 The initial specific discharge capacity of the MX / MH-5 / 2-res sample after hydrogen desorption-absorption treatment was 1416.3 mA hg. -1The concentration of MgH2 was not significantly increased compared to untreated MX / MH-5 / 2. The GCD curves of different samples were similar, indicating that the MgH2 content and hydrogen desorption-absorption treatment did not alter the discharge voltage plateau of the samples.

[0052] like Figure 9 As shown, this invention compares MX / MH-5 / 1, MX / MH-5 / 2, MX / MH-5 / 2-res, MX / MH-5 / 3, and MX / MH-5 / 4 at 0.1 A g. -1 Cyclic performance at current densities. Although the discharge specific capacity of the samples monotonically increased with increasing MgH2 content in the first cycle, the discharge specific capacities of MX / MH-5 / 3 and MX / MH-5 / 4 decreased significantly after the second and third cycles, to 413.0 and 307.3 mA hg, respectively. -1 and 482.7, 303.7 mA hg -1 The discharge specific capacities of MX / MH-5 / 1 and MX / MH-5 / 2 are 479.3 and 413.8 mA h g-1 and 712.1 and 570.0 mA h g-1, respectively. -1 On the other hand, the discharge specific capacities of MX / MH-5 / 2-res after the second and third cycles were 803.2 and 684.8 mA hg, respectively. -1 The specific discharge capacity of all tested samples tended to stabilize after 10 activation cycles. At 0.1 A g... -1 In long-term electrochemical tests after 140 cycles under the specified conditions, the specific discharge capacities at MX / MH-5 / n (n=1-4) current densities were 253.5, 335.5, 229.9, and 158.0 mA hg, respectively. -1 However, MX / MH-5 / 2-res still exhibits the best cycling performance, with a discharge specific capacity of 434.4 mAh g⁻¹. -1 The specific capacity of MX / MH-5 / 2-res surpassed that of the undehydrogenated / hydrogenated MX / MH-5 / 2, and was the highest among all MX / MH-5 / n (n=1-4). Furthermore, the final specific capacity of MX / MH-5 / 2-res even exceeded that of MX / MH-5 / 3, and was comparable to the reversible capacities of MX / MH-5 / 1 and MX / MH-5 / 4. This indicates that the more uniformly sized Ti3C2 / MgH2 particles provide more active sites, improve ion migration kinetics, further stabilize the material structure, and suppress capacity decay. This alleviates structural stress during cycling, promotes rapid lithium-ion transport and stable storage, and thus significantly improves the electrochemical performance of the material.

[0053] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. Metal hydride for use as negative electrode material for lithium ion batteries, characterized in that, The Ti3C2 and MgH2 are mixed as raw materials, and then dehydrogenation-hydrogenation treatment is performed to obtain the metal hydride.

2. A process for the preparation of a metal hydride for use as a negative material for lithium ion batteries according to claim 1, characterized in that, The method comprises the following steps: S1. Adding nano-Ti3C2 to MgH2, and then performing ball milling treatment under inert atmosphere to obtain a mixed powder; S2. Performing one cycle of dehydrogenation-hydrogenation treatment on the mixed powder obtained in S1 to obtain a lithium ion battery negative electrode material.

3. A process for the preparation of a metal hydride for use as a negative material for lithium ion batteries according to claim 2, characterized in that, In S1, the mass ratio of nano-Ti3C2 to MgH2 is 5:1-6.

4. A process for the preparation of a metal hydride for use as a negative material for lithium ion batteries according to claim 3, characterized in that, The mass ratio of nano-Ti3C2 to MgH2 is 5:

2.

5. A process for the preparation of a metal hydride for use as a negative material for lithium ion batteries according to claim 2, characterized in that, In S1, the ball milling process is performed in a planetary ball mill, the ball-to-material ratio is 35-45:1, and the rotation speed is 250-450 rpm / min.

6. A process for the preparation of a metal hydride for use as a negative material for lithium ion batteries according to claim 2, characterized in that, The nano-Ti3C2 is obtained by etching treatment of a Ti3AlC2 MAX precursor with a hydrofluoric acid solution.

7. A process for the preparation of a metal hydride for use as a negative material for lithium ion batteries according to claim 6, characterized in that, In the etching treatment process, the mass fraction of hydrofluoric acid is 35%-45%, the etching temperature is 40-60°C, and the time is 30-40 h.

8. A process for the preparation of a metal hydride for use as a negative material for lithium ion batteries according to claim 2, characterized in that, In S2, in the dehydrogenation process, the temperature is 350-450°C, the pressure is normal pressure, and the holding time is 5-20 min; In the hydrogenation process, the temperature is 350-450°C, the hydrogen pressure is 2-6 MPa, and the holding time is 1-3 h.

9. A process for the preparation of a metal hydride for use as a negative material for lithium ion batteries according to claim 8, characterized in that, In S2, in the dehydrogenation-hydrogenation treatment process, the heating rate is 2-10°C / min.

10. Use of the metal hydride of claim 1 as a lithium ion battery negative electrode material in the preparation of a lithium ion battery.

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