Negative electrode framework material, negative electrode, battery and preparation method of negative electrode framework material

Abstract

The invention discloses a negative electrode framework material, a negative electrode, a battery and a preparation method of the negative electrode framework material, the negative electrode framework material is of a Li15Si4 / Li3N double-phase structure, the Li15Si4 / Li3N double-phase structure has a Li < 1s > wave crest and a Si < 2p > wave crest in XPS determination, and in the Li < 1s > wave crest, the Li < 1s > wave crest and the Si < 2p > wave crest have peaks at 56.1 eV and 55.2 eV; in a Si < 2 > p waveform, there are peaks at 101.2 eV and 102.3 eV. According to the method, Li < + > solvent removing energy barriers can be reduced, the uniformity of the lithium deposition process can be improved, and lithium dendrite growth can be inhibited.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium metal batteries, and particularly relates to a negative electrode framework material, a negative electrode, a battery and a preparation method of the negative electrode framework material. BACKGROUND

[0002] The lithium metal negative electrode is regarded as the core material of the next generation of high-energy-density batteries due to a theoretical specific capacity of 3860 mAh g -1 -3.04 V (vs. SHE) and low potential, but its practical application has long been plagued by capacity decay and safety hazards caused by lithium dendrite growth. And the existing negative electrode generally uses a copper substrate, which has the disadvantage of high desolvation energy barrier, and the copper substrate is prone to lithium dendrite growth during lithium deposition.

[0003] The information disclosed in this BACKGROUND section is only intended to increase an understanding of the general context of the application and is not admitted to be prior art against the application. SUMMARY

[0004] The purpose of the present application is to provide a negative electrode framework material, a negative electrode, a battery and a preparation method of the negative electrode framework material, which can reduce the desolvation energy barrier of Li + and improve the uniformity of the lithium deposition process and inhibit lithium dendrite growth.

[0005] In order to achieve the above-mentioned purpose, the technical scheme provided by an embodiment of the present application is as follows: a negative electrode framework material applied in a lithium metal battery, the negative electrode framework material is Li 15 Si4 / Li3N dual-phase structure, the Li 15 Si4 / Li3N dual-phase structure has Li 1s and Si 2p wave peaks in XPS measurement, and has peaks at 56.1 eV and 55.2 eV in the Li 1s wave form; and has peaks at 101.2 eV and 102.3 eV in the Si 2p wave form.

[0006] In one or more embodiments of the present application, the Li 15 Si4 / Li3N dual-phase structure has a crystal face spacing of 0.24 nm for the

[211] crystal face of Li 15 Si4, and a crystal face spacing of 0.18 nm for the

[110] crystal face of Li3N in the cross-section observation of HRTEM.

[0007] An embodiment of the present application further provides a preparation method of a negative electrode framework material, which is used to prepare the above-mentioned negative electrode framework material, and the preparation method comprises the following steps:

[0008] The silicon nitride, the conductive carbon black and the polyvinylidene fluoride are uniformly mixed, and then coated on a substrate to form a coating layer.

[0009] The substrate with the coating layer is placed in an electrolyte to perform a lithiation reaction, so as to obtain the negative skeleton material.

[0010] In one or more embodiments of the present application, the mass ratio of the silicon nitride, the conductive carbon black and the polyvinylidene fluoride is 8:1:1.

[0011] In one or more embodiments of the present application, the silicon nitride is silicon nitride microrods, the diameter of the silicon nitride microrods is 0.5-1 mu m, and the length of the silicon nitride microrods is 2-5 mu m.

[0012] The diameter of the silicon nitride nanoparticles is 50-200 nm.

[0013] In one or more embodiments of the present application, the solute of the electrolyte includes lithium bis(trifluoromethanesulfonyl)imide and lithium nitrate, and the solvent of the electrolyte includes ethylene glycol dimethyl ether and 1,3-dioxolane.

[0014] In one or more embodiments of the present application, in the electrolyte, the concentration of the lithium bis(trifluoromethanesulfonyl)imide is 1 mol / L, the concentration of the lithium nitrate is 2 wt%, and the volume ratio of the ethylene glycol dimethyl ether and the 1,3-dioxolane is 1:1.

[0015] A negative electrode of a lithium metal battery is also provided in an embodiment of the present application, which includes a substrate, a negative skeleton material modified on the substrate, and metal lithium deposited on the negative skeleton material, and the negative skeleton material is the above-mentioned negative skeleton material.

[0016] In one or more embodiments of the present application, the substrate is a copper substrate.

[0017] A lithium metal battery is also provided in an embodiment of the present application, which includes a positive electrode, an electrolyte and the above-mentioned negative electrode.

[0018] Compared with the prior art, the negative skeleton material, the negative electrode, the battery and the preparation method of the negative skeleton material of the present application can form Li 15 Si4 / Li3N dual-phase structure to form a Li + desolvation energy barrier. Li 15 Si4 and Li3N can effectively prevent the local aggregation of Li + on the surface, and promote the uniform deposition of metal lithium. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only need to show some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0020] Figure 1 Li4Si4 / Li3N dual-phase structure in an embodiment of the present application 15 XPS spectrum of the Li4Si4 / Li3N dual-phase structure;

[0021] Figure 2 Li4Si4 / Li3N dual-phase structure in an embodiment of the present application 15 EELS spectrum of the Li4Si4 / Li3N dual-phase structure;

[0022] Figure 3 Li4Si4 / Li3N dual-phase structure in an embodiment of the present application 15 High-magnification TEM image of the Li4Si4 / Li3N dual-phase structure;

[0023] Figure 4 Schematic diagram of the preparation process of the negative electrode in an embodiment of the present application

[0024] Figure 5 Surface SEM image of lithium on a copper foil substrate with different deposition capacities in Comparative Example 1 of the present application

[0025] Figure 6 Surface SEM image of lithium on a copper foil substrate with different deposition capacities in Comparative Example 2 of the present application 15 Surface SEM image of lithium on a copper foil substrate with different deposition capacities in Comparative Example 2 of the present application

[0026] Figure 7 Surface SEM image of lithium on a copper foil substrate with different deposition capacities in Example 1 of the present application 15 Surface SEM image of lithium on a copper foil substrate with different deposition capacities in Example 1 of the present application

[0027] Figure 8 In-situ optical microscope image of lithium on a copper foil substrate with different deposition times in Example 1 of the present application 15 In-situ optical microscope image of lithium on a copper foil substrate with different deposition times in Example 1 of the present application

[0028] Figure 9 In-situ optical microscope image of lithium on a copper foil substrate with different deposition times in Comparative Example 1 of the present application

[0029] Figure 10 In-situ optical microscope image of lithium on a copper foil substrate with different deposition times in Comparative Example 2 of the present application 15 In-situ optical microscope image of lithium on a copper foil substrate with different deposition times in Comparative Example 2 of the present application DETAILED DESCRIPTION

[0030] In order for those skilled in the technical field to better understand the technical solutions in the present disclosure, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in combination with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of protection of the present disclosure.

[0031] As described in the background, in lithium metal batteries, the substrate of the lithium metal negative electrode is generally a copper substrate, and lithium metal is deposited on the copper substrate to form a lithium metal negative electrode. It has the following disadvantages:

[0032] (1) High desolvation energy barrier: Based on the Cu substrate, the desolvation energy barrier > 254 kJ·mol -1 .

[0033] (2) Limited ion diffusion: For the Cu substrate, the uneven distribution of the surface electric field leads to the accumulation of electrons on the surface protrusions. At the same time, the lack of effective ion diffusion paths hinders the rapid redistribution of Li + , resulting in local nucleation in high electric field intensity areas. During continuous deposition, uneven nucleation gradually develops into Li dendrites.

[0034] (3) Accumulation of lithium dendrites: Cu electrodes exhibit significant polarization after 30 hours at a current density of 1 mA cm -2 , and the voltage curve continues to fluctuate in subsequent cycles, mainly due to the accelerated accumulation of Li dendrites. At high current densities, lithium-ion batteries produce dead Li, which further exacerbates structural degradation and ultimately leads to a sharp decline in electrochemical performance.

[0035] Although the prior art adopts the method of modifying the substrate, it still produces Li dendrites due to the high desolvation energy barrier of lithium ions and the limited deposition kinetics.

[0036] Therefore, the present disclosure discloses a negative electrode framework material which can be used in lithium metal batteries. By designing the negative electrode framework material and modifying it on the substrate of the negative electrode, the desolvation energy barrier can be reduced, the growth of lithium dendrites can be inhibited, homogeneous lithium deposition can be achieved, the nucleation potential barrier of Li + can be effectively reduced, and the performance of lithium metal batteries can be improved.

[0037] As shown in Figure 1 , the negative electrode framework material of the present disclosure is a Li 15 Si4 / Li3N dual-phase structure, and the Li 15The Si4 / Li3N biphase structure exhibits Li 1s and Si 2p waveforms in XPS measurements. In the Li 1s waveform, peaks are observed at 56.1 eV and 55.2 eV; in the Si 2p waveform, peaks are observed at 101.2 eV and 102.3 eV.

[0038] It is understood that after the negative electrode framework material of the present invention is modified on the substrate, Li is used... 15 Si4 and Li3N with Li + The competitive interaction between solvent molecules and anions adsorbed in the solvent structure reconstructs the solvation structure at the interface, reducing the Li + The desolvation energy barrier accelerates the desolvation process, allowing it to be fabricated as an anode and used in lithium metal batteries, which can significantly improve the performance of lithium metal batteries. For example... Figure 1 In Figure a, the peaks at 56.1 eV and 55.2 eV in the Li 1s waveform correspond to Li3N and Li-Si alloys, respectively. 15 Si4). Among them, Li 15 The Si4 / Li3N dual-phase structure, often referred to as the LSLN framework, primarily functions as a framework, facilitating the deposition of lithium metal onto the framework. Combined with a substrate, this forms the negative electrode of a lithium metal battery. XPS stands for X-ray photoelectron spectroscopy.

[0039] Li 15 The Si4 / Li3N dual-phase structure exhibits ultrafast ion conduction capabilities, thanks to Li 15 The combination of Si4 and Li3N results in excellent lithium affinity and enhanced ion transport kinetics, which effectively promotes the uniform deposition of lithium metal.

[0040] like Figure 2 As shown, Li 15 The electron energy loss spectrum of the Si4 / Li3N dual-phase structure under spherical aberration electron microscopy fully demonstrates the electron energy loss of Li4 / Li3N. 15 The uniform distribution of Li, N, and Si elements in the Si4 / Li3N dual-phase structure indirectly confirms the successful lithiation process.

[0041] like Figure 3 As shown, Li 15 In cross-sectional observations of the Si4 / Li3N dual-phase structure using HRTEM (High Resolution Transmission Electron Microscopy), Li... 15 Li on the

[211] crystal plane of Si4 15 The

[211] plane of Si4 has a spacing of 0.24 nm, and the

[110] plane of Li3N has a spacing of 0.18 nm. (This is achieved through...) Figure 2 and Figure 3The combination of the above-mentioned contents can determine Li-Si alloy and Li3N, thereby fully proving Li 15 The Si4 / Li3N dual-phase structure is successfully constructed.

[0042] The application further provides a preparation method of the negative electrode framework material, which can be used for preparing the negative electrode framework material, and comprises the following steps:

[0043] The silicon nitride, the conductive carbon black and the polyvinylidene fluoride (PVDF) are uniformly mixed and then coated on a substrate to form a coating layer.

[0044] The substrate with the coating layer is placed in an electrolyte for a lithiation reaction to obtain the negative electrode framework material.

[0045] Specifically, the mass ratio of the silicon nitride, the conductive carbon black and the polyvinylidene fluoride is 8:1:1.

[0046] Specifically, the solute of the electrolyte comprises lithium bis(trifluoromethanesulfonyl) imide and lithium nitrate, and the solvent of the electrolyte comprises ethylene glycol dimethyl ether and 1,3-dioxolane.

[0047] Preferably, the concentration of lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) can be 1 mol / L, the concentration of lithium nitrate is 1wt%-3wt%, and the volume ratio of ethylene glycol dimethyl ether and 1,3-dioxolane is 1:1.

[0048] Specifically, the silicon nitride (Si3N4) is silicon nitride microrods, the diameter of the silicon nitride microrods is 0.5-1 μm, and the length of the silicon nitride microrods is 2-5 μm; or, the silicon nitride can also be silicon nitride nanoparticles, and the diameter of the silicon nitride nanoparticles is 50-200 nm.

[0049] The application further provides a negative electrode of a lithium metal battery, which comprises a substrate, a negative electrode framework material modified on the substrate, and metal lithium deposited on the negative electrode framework material, and the negative electrode framework material is the negative electrode framework material.

[0050] Specifically, the substrate is a copper substrate, for example, a copper foil or a copper sheet.

[0051] The application further provides a preparation method of the negative electrode of the lithium metal battery, which comprises the following steps:

[0052] The silicon nitride, the conductive carbon black and the polyvinylidene fluoride are uniformly mixed and then coated on a substrate to form a coating layer.

[0053] The substrate with the coating layer is placed in an electrolyte for a lithiation reaction to obtain the substrate modified with the negative electrode framework material.

[0054] The substrate modified with the negative skeleton material is subjected to lithium deposition to form metal lithium on the negative skeleton material, thereby obtaining the negative electrode of the application.

[0055] Figure 4 A schematic diagram of the preparation process of the negative electrode.

[0056] The application also provides an alkali metal battery comprising a positive electrode, an electrolyte and the negative electrode as claimed in claim 8 or 9.

[0057] The negative skeleton material, the negative electrode, the battery and the preparation method of the negative skeleton material of the application will be described in detail below in combination with specific examples and comparative examples.

[0058] Example 1

[0059] Silicon nitride microrods, conductive carbon black and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 8:1:1. The diameter of the silicon nitride microrods is 0.5-1 μm, and the length of the silicon nitride microrods is 2-5 μm.

[0060] The mixture is coated on a copper foil to form a coating layer, and the thickness of the coating layer is about 40 μm.

[0061] The copper foil with the coating layer is matched with lithium metal to assemble a half battery. Lithiation reaction is carried out in a constant current mode at a current density of 0.1 mA cm -2 -2, and the cutoff voltage is 0.005 V. After the lithiation is completed, the battery is disassembled and the electrode sheet is taken out to obtain a copper foil modified with a Li 15 Si4 / Li3N dual-phase structure on the surface. The electrolyte used is a mixture of ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) in a volume ratio of 1:1. The solutes in the electrolyte are LiTFSI (lithium bis-trifluoromethyl sulfonamide) and LiNO3 (lithium nitrate), wherein the concentration of LiTFSI is 1 mol / L, and the concentration of LiNO3 is 2 wt%. This electrolyte formulation can provide high ionic conductivity and help improve the uniformity of lithium metal deposition.

[0062] The copper foil modified with the Li 15 Si4 / Li3N dual-phase structure is used as a negative electrode material, and lithium deposition is carried out at a current density of 1 mA cm -2 -2 for 2 h.

[0063] Example 2

[0064] Silicon nitride microrods, conductive carbon black and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 8:1:1. The diameter of the silicon nitride microrods is 0.1-0.5 μm, and the length of the silicon nitride microrods is 7-10 μm

[0065] The mixture was coated on a copper foil to form a coating layer with a thickness of about 40 pm.

[0066] The copper foil with the coating layer was matched with lithium metal to assemble a half battery. Lithiation reaction was carried out in a constant current mode at a current density of 0.1 mA cm -2 -1, and the cut-off voltage was 0.005 V. After the completion of lithiation, the battery was disassembled and the electrode sheet was taken out to obtain a copper foil with a Li 15 Si4 / Li3N dual-phase structure on the surface. The electrolyte used was a mixture of ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) in a volume ratio of 1:1. The solutes in the electrolyte were LiTFSI (lithium bistrifluoromethanesulfonimide) and LiNO3 (lithium nitrate), with the concentration of LiTFSI being 1 mol / L and the concentration of LiNO3 being 1 wt%. This electrolyte formulation can provide high ionic conductivity and help improve the uniformity of lithium metal deposition.

[0067] The copper foil with the Li 15 Si4 / Li3N dual-phase structure on the surface was used as a negative electrode material, and lithium deposition was carried out at a current density of 1 mA cm -2 -1 for 2 h.

[0068] Example 3

[0069] Silicon nitride microrods, conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 8:1:1. The diameter of the silicon nitride microrods was 1-1.5 pm, and the length of the silicon nitride microrods was 0-1 pm

[0070] The mixture was coated on a copper foil to form a coating layer with a thickness of about 40 pm.

[0071] The copper foil with the coating layer was matched with lithium metal to assemble a half battery. Lithiation reaction was carried out in a constant current mode at a current density of 0.1 mA cm -2 -1, and the cut-off voltage was 0.005 V. After the completion of lithiation, the battery was disassembled and the electrode sheet was taken out to obtain a copper foil with a Li 15 Si4 / Li3N dual-phase structure on the surface. The electrolyte used was a mixture of ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) in a volume ratio of 1:1. The solutes in the electrolyte were LiTFSI (lithium bistrifluoromethanesulfonimide) and LiNO3 (lithium nitrate), with the concentration of LiTFSI being 1 mol / L and the concentration of LiNO3 being 3 wt%. This electrolyte formulation can provide high ionic conductivity and help improve the uniformity of lithium metal deposition.

[0072] Li-modified 15 Using Si4 / Li3N dual-phase copper foil as the negative electrode material, at 1 mA cm⁻¹ -2 Lithium deposition was performed at a current density of 2 h.

[0073] Comparative Example 1

[0074] The electrode after lithium deposition on bare copper foil (pure copper) is selected as the negative electrode.

[0075] Comparative Example 2

[0076] Choose the modification with Li 15 The electrode after lithium deposition on bare copper foil containing Si4 nanoparticles is used as the negative electrode.

[0077] The following performance tests were performed on the structures and electrodes in Example 1, Comparative Example 1, and Comparative Example 2:

[0078] The testing process for Example 1 is as follows:

[0079] (1) Lithium sheet and Li-modified sheet 15 A half-cell was assembled from copper foils with a Si4 / Li3N biphase structure and subjected to multiple cycles of constant current discharge-constant voltage charge in an electrolyte. This method was used to evaluate the role of lithium metal in Li... 15 The reversibility of deposition and stripping on the Si4 / Li3N biphase structure. Specifically, the half-cell is first subjected to constant current discharge, typically with a current density set at 1 mA cm⁻¹. -2 The charging time is fixed at 1 hour. Afterwards, constant voltage charging is performed until the battery reaches a set voltage (e.g., 0.5V). This process is repeated multiple times, recording the capacity for each cycle and calculating the coulombic efficiency. By analyzing the changes in charge / discharge capacity, the reversibility of lithium metal deposition and stripping on this two-phase structure is evaluated.

[0080] (2) Half-cell cycle stability test: In Li-modified cells 15 On one side of the Si4 / Li3N dual-phase copper foil, firstly, at 2mA cm -2 Lithium metal pre-deposition was performed at a current density to serve as the negative electrode, and the cells were assembled into a symmetrical battery. The stability of this structure during long-term cycling and its improvement effect on the desolvation process were evaluated through a constant current constant capacity charge-discharge process. During the test, constant current charge-discharge was applied until the battery reached 2 mAh cm⁻¹. -2 By continuously cycling the battery multiple times, the capacity decay was monitored to evaluate the uniformity and stability of lithium metal deposition on the negative electrode surface, as well as the effect of the two-phase structure on improving lithium metal deposition behavior.

[0081] (3) When modified with Li 15On a copper foil with a Si4 / Li3N dual-phase structure, at a density of 2 mA cm -2 Lithium metal pre-deposition was performed at a current density with a loading of 10 mg / cm³. -2 LiFePO4 was used as the positive electrode to assemble a full cell. The application potential of this electrode in practical batteries was evaluated through charge-discharge tests and rate tests. Full cell testing included standard charge-discharge cycles, typically with a battery voltage range of 2.5 V to 3.9 V, and charge-discharge tests were conducted at different current densities (e.g., 0.1C, 0.5C, 1C, etc.). The performance of the electrode material and its stability under different operating conditions were further evaluated by analyzing the battery capacity and efficiency in each charge-discharge cycle.

[0082] The testing process for Comparative Example 1 is as follows:

[0083] (1) A half-cell was assembled from lithium foil and copper foil, and subjected to multiple cycles of constant current discharge-constant voltage charge in an electrolyte. This method was used to evaluate the reversibility of lithium metal deposition and stripping on the copper foil. Specifically, the half-cell was first subjected to constant current discharge, typically with a current density set at 1 mA cm⁻¹. -2 The charging time is fixed at 1 hour. Afterwards, constant voltage charging is performed until the battery reaches a set voltage (e.g., 0.5V). This process is repeated multiple times, recording the capacity for each cycle and calculating the coulombic efficiency. By analyzing the changes in charge / discharge capacity, the reversibility of lithium metal deposition and stripping on the copper foil is evaluated.

[0084] (2) Half-cell cycle stability test: On the copper foil side, firstly at 2 mA cm -2 Lithium metal pre-deposition was performed at a current density to serve as the negative electrode, and the cells were assembled into a symmetrical battery. The stability of this structure during long-term cycling and its improvement effect on the desolvation process were evaluated through a constant current constant capacity charge-discharge process. During the test, constant current charge-discharge was applied until the battery reached 2 mAh cm⁻¹. -2 By continuously cycling the battery multiple times, the capacity decay was monitored, and the deposition behavior of lithium metal on the copper foil surface was evaluated.

[0085] (3) Apply 2 mA cm on copper foil -2 Lithium metal pre-deposition was performed at a current density with a loading of 10 mg / cm³. -2LiFeP04 as a cathode to assemble a full cell. The potential of the electrode in a real battery is evaluated by charge-discharge tests and rate capability tests. The tests of the full cell include standard charge-discharge processes, usually the voltage range of the battery is between 2.5 V and 3.9 V, and the charge-discharge tests are performed at different current densities (e.g. 0.1C, 0.5C, 1C, etc.). By analyzing the capacity and efficiency of the battery in each charge-discharge cycle, the performance of the electrode material and the stability under different working conditions are further evaluated.

[0086] The test procedure of Comparative Example 2 is as follows:

[0087] (1) Lithium foil and Li 15 Si4 nanoparticle modified copper foil are assembled into a half-cell, and a multi-cycle constant current discharge-constant voltage charging process is performed in the electrolyte. In this way, the reversibility of lithium metal deposition and stripping on the Li 15 Si4 nanoparticle modified copper foil is evaluated. Specifically, the half-cell is first subjected to constant current discharge, and the current density is usually set to 1 mA cm -2 , and the fixed time is 1 h. Then constant voltage charging is performed, and the battery is charged to a set voltage (e.g. 0.5 V). This process is repeated multiple times, the capacity of each cycle is recorded, and the coulombic efficiency is calculated. By analyzing the change of charge-discharge capacity, the reversibility of lithium metal deposition and stripping on the structure is evaluated.

[0088] (2) Half-cell cycle stability test: on one side of the Li 15 Si4 nanoparticle modified copper foil, lithium metal is first pre-deposited at a current density of 2 mA cm -2 , as the negative electrode, to assemble a symmetric cell. The stability of the structure during long-term cycling and its improvement on the desolvation process are evaluated by constant current constant capacity charge-discharge process. During the test, constant current charge-discharge is performed until the battery reaches 2 mAh cm -2 . By continuous multiple cycles, the capacity decay of the battery is monitored, and the deposition behavior of lithium metal on the Li 15 Si4 nanoparticle modified copper foil is evaluated.

[0089] (3) Lithium metal is pre-deposited on the Li 15 Si4 nanoparticle modified copper foil at a current density of 2 mA cm -2 , and the loading is 10 mg cm -2LiFePO4 as cathode to assemble full cells. The potential of the electrode in practical batteries is evaluated by charge-discharge tests and rate tests. The tests of full cells include standard charge-discharge processes, usually the voltage range of the battery is between 2.5 V and 3.9 V, and the charge-discharge tests are carried out at different current densities (such as 0.1C, 0.5C, 1C, etc.). By analyzing the battery capacity and efficiency in each charge-discharge cycle, the performance of the electrode material and the stability under different working conditions are further evaluated.

[0090] The above performance tests respectively obtain data graphs as Figures 5 to 10

[0091] As shown in Figure 5 , in Comparative Example 1, only copper is deposited on the pure copper substrate as the electrode, and the pure copper is lithium-averse on the surface, and the filamentous lithium metal structure is observed at a low deposition capacity of 2 mAh·cm -2 . As the deposition capacity increases to 4 and 6 mAh·cm -2 , the lithium dendrites grow more significantly on the surface of the electrode, indicating that the lithium metal forms a loose and porous structure on the copper foil. This structure not only affects the deposition uniformity of the lithium metal, but also leads to poor electrochemical stability and short cycle life.

[0092] As shown in Figure 6 , in Comparative Example 2, the copper substrate is modified with Li 15 Si4 alloy particles, and the modified structure is lithiumophilic, and no obvious dendrite growth is observed at different deposition capacities. However, the skeleton constructed by the Li 15 Si4 alloy particles of the electrode collapses significantly at high capacity, leading to inevitable growth of lithium dendrites after multiple cycles.

[0093] As shown in Figure 7 , in Example 1, the copper substrate is modified with Li 15 Si4 / Li3N dual-phase structure, and the modified structure exhibits dendrite-free lithium deposition behavior at different deposition capacities, mainly due to the synergistic effect of multiple mechanisms such as excellent lithiumophilicity, fast ion transport ability, and competitive adsorption. This dendrite-free deposition behavior provides a reliable guarantee for the high reversibility and long cycle life of the battery.

[0094] As shown in Figure 8 , by observing the lithium deposition process in situ by optical microscopy, in the electrode modified with the Li 15 Si4 / Li3N dual-phase structure, a uniform and dendrite-free lithium layer is formed after 40 minutes of deposition; after the deposition time is extended to 80 and 120 minutes, the lithium layer gradually thickens, but no dendrite structure is formed.

[0095] As shown in Figure 9 ​As shown, on an unmodified copper foil substrate, metallic lithium begins to deposit within the first 40 minutes, and filamentous structures appear at 80 minutes. The number of dendrites increases significantly at 120 minutes, which is consistent with the SEM observation results.

[0096] like Figure 10 As shown, for Li modified 15 Although no obvious dendrites were initially observed on the copper foil substrate of Si4 alloy particles, lithium agglomerates began to appear on the electrode surface after the deposition time was extended to 80 and 120 minutes.

[0097] In summary, the Li of the present invention 15 The Si4 / Li3N dual-phase structure utilizes Li 15 Si4 and Li3N with Li + The competitive interaction between solvent molecules and anions adsorbed in the solvent structure reconstructs the solvation structure at the interface, reducing the Li + The desolventization process is accelerated, thereby greatly improving the performance of lithium metal batteries.

[0098] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0099] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A negative electrode framework material, used in lithium metal batteries, characterized in that, The negative electrode framework material is Li. 15 The Si4 / Li3N dual-phase structure, wherein the Li 15 The Si4 / Li3N biphase structure exhibits Li 1s and Si 2p peaks in XPS measurements. In the Li 1s waveform, peaks are observed at 56.1 eV and 55.2 eV; in the Si 2p waveform, peaks are observed at 101.2 eV and 102.3 eV.

2. The negative electrode framework material according to claim 1, characterized in that, The Li 15 In cross-sectional observations of the Si4 / Li3N two-phase structure by HRTEM, Li 15 The interplanar spacing of the [211] crystal plane of Si4 is 0.24 nm, and the interplanar spacing of the [110] crystal plane of Li3N is 0.18 nm.

3. A method for preparing a negative electrode framework material, used to prepare the negative electrode framework material according to claim 1 or 2, characterized in that, The preparation method includes the following steps: Silicon nitride, conductive carbon black and polyvinylidene fluoride are mixed evenly and then coated onto a substrate to form a coating layer. The substrate with the coating is placed in an electrolyte to undergo a lithiation reaction, thereby obtaining the negative electrode framework material.

4. The method for preparing the negative electrode framework material according to claim 3, characterized in that, The mass ratio of silicon nitride, conductive carbon black and polyvinylidene fluoride is 8:1:

1.

5. The method for preparing the negative electrode framework material according to claim 3, characterized in that, The silicon nitride is a silicon nitride microrod, the diameter of which is 0.5~1μm and the length of which is 2~5μm; or, The silicon nitride is silicon nitride nanoparticles with a diameter of 50~200nm.

6. The method for preparing the negative electrode framework material according to claim 3, characterized in that, The solutes in the electrolyte include lithium bis(trifluoromethanesulfonyl)imide and lithium nitrate, and the solvents in the electrolyte include ethylene glycol dimethyl ether and 1,3-dioxolane.

7. The method for preparing the negative electrode framework material according to claim 6, characterized in that, In the electrolyte, the concentration of lithium bis(trifluoromethanesulfonate)imide is 1 mol / L, the concentration of lithium nitrate is 2 wt%, and the volume ratio of ethylene glycol dimethyl ether to 1,3-dioxolane is 1:

1.

8. A negative electrode for a lithium metal battery, characterized in that, The anode material includes a substrate, a negative electrode framework material modified on the substrate, and metallic lithium deposited on the negative electrode framework material, wherein the negative electrode framework material is the negative electrode framework material according to claim 1 or 2.

9. The negative electrode of the lithium metal battery according to claim 8, characterized in that, The substrate is a copper substrate.

10. A lithium metal battery, characterized in that, It includes a positive electrode, an electrolyte, and a negative electrode as described in claim 8 or 9.

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