LiSn / In negative electrode, preparation method thereof and all-solid-state battery

Abstract

The application provides a LiSn / In negative electrode and a preparation method thereof and a full-solid-state battery, and relates to the technical field of solid-state batteries.The preparation method comprises the following steps: firstly, Li metal sheets and Sn metal sheets are prepared into LiSn alloy sheets through a mechanical rolling method; and secondly, metal In is evaporated onto the surface of the LiSn alloy sheets by a vacuum evaporation method to obtain the LiSn / In negative electrode.In the LiSn / In negative electrode prepared by the above preparation method, the LiSn alloy has an ultra-low lithium diffusion barrier (0.18eV), can accelerate the uniform transmission of lithium ions, reduce the formation of lithium dendrites, and significantly improve the cycle stability of the battery; and the existence of the interface In can inhibit the interface side reaction of the negative electrode and the sulfide electrolyte, so that the symmetrical battery prepared by using the LiSn / In negative electrode has a higher critical current density and a longer cycle life under the same current density, and the full-solid-state battery prepared by using the LiSn / In negative electrode also has a longer cycle life.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, specifically to a LiSn / In anode, its preparation method, and an all-solid-state battery. Background Technology

[0002] With the rapid development of the global new energy industry, from portable electronic devices to electric vehicles and large-scale energy storage power stations, the performance requirements for energy storage technologies are constantly upgrading. This not only necessitates breaking through the energy density limits of traditional liquid lithium-ion batteries (current commercial systems mostly have energy densities below 300Wh / kg), but also addressing the safety hazards associated with liquid electrolytes, such as leakage, combustion, and explosion. Against this backdrop, all-solid-state lithium metal batteries (ASSLMBs), with their dual advantages of "high energy density + high safety," have become a core research hotspot for next-generation energy storage technologies. Among them, those using sulfide-based solid electrolytes (such as Li...) 10 GeP2S 12 ASSLMBs (typical systems such as LGPS and Li6PS5Cl (LPSCl)) have attracted much attention from the scientific and industrial communities due to their key performance characteristics that far surpass those of other solid electrolytes: the room temperature ionic conductivity of these sulfide electrolytes can reach 10. -3 -10 - 2 S·cm -1 It not only approaches but even surpasses traditional liquid electrolytes (approximately 10...) -2 S·cm -1 Furthermore, it can achieve dense electrode-electrolyte interface contact through cold pressing, significantly reducing interface impedance and laying the foundation for high-rate performance and long-cycle stability of the battery.

[0003] However, despite the great potential of sulfide-based solid electrolytes (ASLBs) in terms of theoretical performance, their practical application still faces three major interrelated challenges. These challenges constrain battery performance from multiple dimensions, including intrinsic electrode properties, interfacial reactions, and structural stability: First, the Li metal anode... + The problem of sluggish bulk diffusion kinetics. Although lithium metal possesses extremely high theoretical specific capacity (3860 mAh / g) and the lowest electrode potential (-3.04 V vs standard hydrogen electrode), its intrinsic Li₂... + The bulk diffusion coefficient is low (approximately 10 at room temperature). -14 ~10 -13 cm² / s), resulting in Li during charging and discharging. + It cannot be transported quickly and uniformly within lithium metal. This problem directly causes spatial inhomogeneities in the lithium deposition / stripping process: during charging, Li... +Lithium bumps tend to accumulate and deposit in localized areas, forming "lithium bumps." These bumps are difficult to peel off evenly during discharge, and over long-term cycling, they gradually destroy the interface integrity between the negative electrode and the sulfide electrolyte, leading to poor interface contact and further exacerbating impedance increases and performance degradation.

[0004] Second, the risk of lithium dendrite growth and penetration. Due to Li + Uneven bulk transport and localized differences in interfacial electric field distribution cause lithium metal to easily grow dendrites along defects (such as micropores and grain boundaries) at the negative electrode-electrolyte interface during charging. Although sulfide electrolytes possess a certain mechanical strength (hardness of approximately 2-5 GPa), which can suppress dendrite growth to some extent, lithium dendrites will continue to grow and gradually penetrate the electrolyte layer under long-term cycling. Once dendrites connect the positive and negative electrodes, they will cause an internal short circuit in the battery, leading not only to instantaneous battery failure but also potentially causing the decomposition of the sulfide electrolyte due to localized overheating, posing a serious safety hazard.

[0005] Third, sulfide electrolytes have a narrow electrochemical stability window, driving interfacial parasitic reactions. The stability window of most sulfide electrolytes is only 0.7–2.5 V (vs. Li). + Lithium oxide (Li₆PS₅Cl) cannot withstand high-voltage cathodes (such as ternary cathodes and nickel-rich cathodes, whose operating voltages are often higher than 3.5 V), and it is also prone to thermodynamically spontaneous parasitic reactions with lithium metal anodes. For example, when Li₆PS₅Cl comes into contact with lithium metal, a reduction reaction occurs to produce products such as Li₂S, LiCl, and elemental P. The interfacial layer formed by these products has extremely low ionic conductivity (the ionic conductivity of Li₂S is about 10 Ω·cm). -8 S·cm -1 Furthermore, it will gradually thicken and crack, leading to a sharp increase in interface impedance and a significant increase in battery overpotential during charging and discharging, ultimately resulting in rapid capacity decay and a significant reduction in cycle life.

[0006] To address these challenges, the scientific research field has conducted extensive explorations, among which "designing artificial interface layers" is currently the mainstream strategy for improving interface stability. For example, buffer layers are constructed between lithium metal and sulfide electrolytes through physical deposition (such as atomic layer deposition of Al2O3 and Li3PO4) or chemical modification (such as in-situ generation of Li3N and Li2S-P2S5 composite layers) to isolate direct contact between the two and suppress parasitic reactions. However, these strategies have significant limitations: on the one hand, they mostly focus on "interface modification," blocking reaction pathways only from the outside, while neglecting the intrinsic Li3N content of the lithium metal anode. +Bulk transport limitations mean that even if interfacial reactions are suppressed, slow bulk diffusion can still lead to uneven lithium deposition, creating a potential breeding ground for dendrite growth. On the other hand, the mechanical stability of artificial interfacial layers is poor. Under long-term cycling, changes in the volume of lithium metal (although the volume change of lithium metal in solid-state batteries is smaller than that in liquid batteries, there is still a fluctuation of about 10% to 15%) can cause the interfacial layer to crack and peel off, losing its protective function and making it difficult to achieve long-term stable cycling performance.

[0007] Therefore, to fundamentally overcome the performance bottlenecks of sulfide-based ASSLMBs and promote their industrial application from the laboratory, it is urgent to develop a method that combines "accelerated Li..." + A negative electrode structure with dual functions of "transmission" and "stable interface". Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention solves the following technical problem: providing a LiSn / In anode, its preparation method, and an all-solid-state battery, which can accelerate uniform lithium-ion transport, reduce lithium dendrite formation, significantly improve battery cycle stability, and suppress interfacial side reactions between the anode and the sulfide electrolyte, thereby increasing the battery's energy density and cycle life.

[0009] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a LiSn / In anode, comprising the following steps: First, Li metal sheets and Sn metal sheets are prepared into LiSn alloy sheets by mechanical rolling. Then, metallic In is deposited onto the surface of the LiSn alloy sheet using a vacuum evaporation method to obtain a LiSn / In negative electrode.

[0010] Preferably, the thickness of the LiSn alloy sheet is 30-70 μm.

[0011] Preferably, the thickness of the In coating in the LiSn / In negative electrode is 1-5 μm.

[0012] Preferably, the specific steps of the mechanical rolling method include: stacking Li metal sheets and Sn metal sheets, folding them in half, and then pressing them with a pressure of 2-150 MPa to obtain LiSn alloy sheets.

[0013] Preferably, the number of times the tablet is folded in half and then compressed is 25-50 times.

[0014] Preferably, the mass ratio of the Li metal sheet to the Sn metal sheet is (1-3):(1-3).

[0015] Preferably, the thickness of the Li metal sheet is 20-60 μm; the thickness of the Sn metal sheet is 20-60 μm.

[0016] Preferably, the specific steps of the vacuum evaporation method include: in a temperature range of ≤5×10⁻⁶ m² / h⁻¹, the vacuum evaporation method includes: -4 Under a vacuum of Pa, metallic In is heated to 800-1200℃ to deposit a metallic In film onto the surface of the LiSn alloy sheet.

[0017] Secondly, the present invention also provides a LiSn / In anode, which is prepared by the LiSn / In anode preparation method described in the first aspect.

[0018] Thirdly, the present invention also provides an all-solid-state battery, comprising a positive electrode, a LiSn / In negative electrode as described in the second aspect, and a sulfide electrolyte.

[0019] Compared with the prior art, the advantages of the present invention are as follows: This invention first prepares a LiSn alloy through mechanical rolling, and then deposits a layer of metallic In on the surface of the LiSn alloy using vacuum evaporation to form a LiSn / In anode. The LiSn alloy has an ultra-low lithium diffusion barrier (0.18 eV), which accelerates uniform lithium-ion transport, reduces lithium dendrite formation, and significantly improves battery cycle stability. The presence of In at the interface suppresses interfacial side reactions between the anode and the sulfide electrolyte, thus enabling symmetric batteries using the LiSn / In anode to exhibit a higher critical current density and longer cycle life at the same current density. It also allows all-solid-state batteries using the LiSn / In anode to exhibit longer cycle life. In summary, this invention combines lithium metal alloying and interface modification technologies, and is simple and effective to operate. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention provides a LiSn / In anode, its preparation method, and an all-solid-state battery. The LiSn / In anode can accelerate the uniform transport of lithium ions, reduce the formation of lithium dendrites, and significantly improve the cycle stability of the battery. At the same time, it can suppress the interfacial side reactions between the anode and the sulfide electrolyte, thereby improving the energy density and cycle life of the battery. This solves the technical defects of sulfide-based solid-state batteries in the prior art, such as poor cycle stability, low energy density, and low cycle life.

[0022] To achieve the above-mentioned technical effects, the overall concept of this invention is as follows: In a first aspect, embodiments of the present invention provide a method for preparing a LiSn / In anode, comprising the following steps: First, Li metal sheets and Sn metal sheets are prepared into LiSn alloy sheets by mechanical rolling. Then, metallic In is deposited onto the surface of the LiSn alloy sheet using a vacuum evaporation method to obtain a LiSn / In negative electrode.

[0023] This invention first prepares LiSn alloy by mechanical rolling, and then deposits a layer of metallic In on the surface of the LiSn alloy by vacuum evaporation to form a LiSn / In negative electrode. By combining lithium metal alloying and interface modification technology, it is not only simple to operate, but also has a significant effect on improving the current density and cycle life of the battery.

[0024] This invention first obtains a uniformly composed LiSn alloy through mechanical rolling. The LiSn alloy has an ultra-low lithium diffusion barrier (0.18 eV), which can accelerate the uniform transport of lithium ions, reduce the formation of lithium dendrites, and significantly improve the cycle stability of the battery. Then, metallic In is deposited on the surface of the LiSn alloy through vacuum evaporation to modify the interface of the LiSn alloy. The presence of In at the interface can suppress the interfacial side reactions between the negative electrode and the sulfide electrolyte, thereby enabling the symmetric battery prepared with LiSn / In negative electrode to exhibit a higher critical current density and a longer cycle life at the same current density. At the same time, it can also enable the all-solid-state battery prepared with LiSn / In negative electrode to exhibit a longer cycle life.

[0025] Preferably, the thickness of the LiSn alloy sheet is 30-70 μm. Through extensive experimental research, this invention has found that if the LiSn alloy sheet is too thick, it will reduce the energy density of the battery and increase the cost of raw materials; if the LiSn alloy sheet is too thin, it is prone to bending and deformation, accelerating lithium dendrite growth, and is also difficult to process.

[0026] Preferably, the thickness of the In coating in the LiSn / In negative electrode is 1-5 μm. Through extensive experimental research, this invention has found that when the In coating is too thin, almost all of the In reacts with excess Li to form a LiIn alloy. The interface modification effect of the LiIn alloy is far inferior to that of the In layer, thus affecting the electrochemical performance of the battery. When the In coating is too thick, it affects the effective lithium-ion transport, thereby affecting the rate performance of the battery.

[0027] Preferably, the specific steps of the mechanical rolling method include: stacking Li metal sheets and Sn metal sheets, folding them in half, and then pressing them with a pressure of 2-150 MPa to obtain LiSn alloy sheets.

[0028] Specifically, the mechanical rolling method of this invention involves first folding stacked Li metal sheets and Sn metal sheets in half, then mechanically rolling them together. After the mechanical rolling process is completed, the resulting sheet is folded in half again, and then mechanically rolled again. This process of folding and rolling is repeated multiple times to obtain a more uniform LiSn alloy, thereby improving the LiSn alloy's role in lithium-ion transport, reducing lithium dendrite formation, and significantly improving battery cycle stability. At the same time, the more uniform LiSn alloy has a stronger bonding ability with metallic In, thus improving the structural stability of the negative electrode.

[0029] Preferably, the folding and pressing process is repeated 25-50 times. Through extensive experimental research, this invention has found that repeating the folding and pressing step 25-50 times results in a relatively uniform composite of metallic Li and metallic Sn, forming a LiSn alloy. However, if the folding is repeated too many times, cracks appear in the LiSn alloy sheet.

[0030] Preferably, the mass ratio of the Li metal sheet to the Sn metal sheet is (1-3):(1-3). Extensive experiments have shown that too much Sn leads to an excess of Sn, which further combines with Li during cycling to form a LiSn alloy, severely reducing the cycling efficiency of Li ions. However, too little Sn results in an insufficient LiSn alloy framework, making it difficult to suppress problems such as volume expansion of metallic Li and dendrite growth.

[0031] In a preferred embodiment, the mass ratio of Li metal sheet to Sn metal sheet is 1:1.

[0032] Preferably, the thickness of the Li metal sheet is 20-60 μm; the thickness of the Sn metal sheet is 20-60 μm.

[0033] Preferably, the specific steps of the vacuum evaporation method include: in a temperature range of ≤5×10⁻⁶ m² / h⁻¹, the vacuum evaporation method includes: -4 Under a vacuum of Pa, metallic In is heated to 800-1200℃ to deposit a metallic In film onto the surface of the LiSn alloy sheet.

[0034] Using high temperatures of 800-1200℃, metallic In is decomposed into atomic levels. On the one hand, atomic-level In reacts rapidly with metallic Li at the beginning of deposition to form a LiIn alloy, ensuring that the subsequent In layer can be tightly bonded to the LiSn alloy sheet, thereby improving the stability of the LiSn / In anode structure. On the other hand, atomic-level metallic In is conducive to the uniform deposition of In onto the surface of the LiSn alloy sheet.

[0035] In this embodiment of the invention, the preparation method of the LiSn / In anode specifically includes the following steps: S1. Prepare a Li metal sheet with a thickness of 20-60μm, a Sn metal sheet with a thickness of 20-60μm, and In metal. The mass ratio of the Li metal sheet to the Sn metal sheet is (1-3):(1-3). S2. In the glove box, place the Li metal sheet and Sn metal sheet on top of each other, fold them in half, and then press them with a pressure of 2-150MPa. Repeat the folding and pressing steps 25-50 times to obtain a LiSn alloy sheet with a thickness of 30-70μm. S3. Place a certain amount of metallic In onto the evaporation boat of the vacuum coating machine, set the evaporation program, and ensure the vacuum degree is ≤5×10⁻⁶. -4 Pa, heat metallic In to 800-1200℃, use LiSn alloy sheet as substrate, and deposit metallic In film onto the surface of LiSn alloy sheet until the thickness of metallic In film is 1-5μm, then stop the evaporation process to prepare LiSn / In anode.

[0036] Secondly, the present invention also provides a LiSn / In anode, which is prepared by the LiSn / In anode preparation method described in the first aspect.

[0037] This invention first prepares a LiSn alloy through mechanical rolling, and then deposits a layer of metallic In on the surface of the LiSn alloy using vacuum evaporation to form a LiSn / In anode. Firstly, repeatedly folding and pressing tin and lithium sheets together yields a more uniformly composed LiSn alloy. The LiSn alloy possesses an ultra-low lithium diffusion barrier (0.18 eV), which accelerates uniform lithium-ion transport, reduces lithium dendrite formation, and significantly improves battery cycle stability. Furthermore, the presence of In at the interface suppresses interfacial side reactions between the anode and the sulfide electrolyte. This results in symmetrical batteries using the LiSn / In anode exhibiting a higher critical current density and longer cycle life at the same current density, and also enables all-solid-state batteries using the LiSn / In anode to exhibit an even longer cycle life.

[0038] Thirdly, the present invention also provides an all-solid-state battery, comprising a positive electrode, a negative electrode, and a sulfide electrolyte. The negative electrode is the LiSn / In negative electrode described in the second aspect.

[0039] This invention first prepares a LiSn alloy by mechanical rolling, and then deposits a layer of metallic In on the surface of the LiSn alloy by vacuum evaporation to form a LiSn / In anode. Firstly, repeatedly folding and pressing tin and lithium sheets together yields a more uniformly composed LiSn alloy. The LiSn alloy possesses an ultra-low lithium diffusion barrier (0.18 eV), which accelerates uniform lithium-ion transport, reduces lithium dendrite formation, and significantly improves battery cycle stability. Furthermore, the presence of In at the interface suppresses interfacial side reactions between the anode and the sulfide electrolyte, resulting in a longer cycle life for all-solid-state batteries using the LiSn / In anode.

[0040] Preferably, the positive electrode is selected from one or more of lithium iron phosphate, nickel-cobalt-manganese ternary materials, and lithium-rich manganese-based materials.

[0041] Preferably, the sulfide electrolyte is selected from one or more of lithium phosphorus sulfide chloride, iodine-doped lithium phosphorus sulfide chloride, lithium phosphorus sulfide, and lithium germanium phosphorus sulfide.

[0042] The following specific embodiments illustrate a LiSn / In anode, its preparation method, and an all-solid-state battery according to the present invention. All raw materials used in the embodiments of the present invention are commercially available battery-grade products, which can be purchased through conventional commercial channels unless otherwise specified.

[0043] Example 1 A method for preparing a LiSn / In anode: S1. Prepare a Li metal sheet with a thickness of 50 μm, a Sn metal sheet with a thickness of 50 μm, and In metal, wherein the mass ratio of the Li metal sheet to the Sn metal sheet is 1:1. S2. In the glove box, Li metal sheet and Sn metal sheet are stacked and folded in half. Then, they are pressed into a sheet using a pressure of 100 MPa. The folding and pressing steps are repeated 30 times to obtain a LiSn alloy sheet with a thickness of 30 μm. S3. Place a certain amount of metallic In onto the evaporation boat of the vacuum coating machine, set the evaporation program, and set the vacuum degree to 5×10. -4 Pa, heat metallic In to 1000℃, use a LiSn alloy sheet as a substrate, and deposit metallic In onto the surface of the LiSn alloy sheet until the thickness of the metallic In coating is 2μm, then stop the evaporation process to prepare a LiSn / In anode.

[0044] Example 2 A method for preparing a LiSn / In anode: S1. Prepare a Li metal sheet with a thickness of 50 μm, a Sn metal sheet with a thickness of 50 μm, and In metal, wherein the mass ratio of the Li metal sheet to the Sn metal sheet is 1:3. S2. In the glove box, Li metal sheet and Sn metal sheet are stacked and folded in half. Then, they are pressed into sheets with a pressure of 100 MPa. The folding and pressing steps are repeated 25 times to obtain a LiSn alloy sheet with a thickness of 70 μm. S3. Place a certain amount of metallic In onto the evaporation boat of the vacuum coating machine, set the evaporation program, and set the vacuum degree to 5×10. -4 Pa, heat metallic In to 1200℃, use LiSn alloy sheet as substrate, deposit metallic In film onto the surface of LiSn alloy sheet until the thickness of metallic In film is 4μm, stop the evaporation process, and prepare LiSn / In anode.

[0045] Example 3 A method for preparing a LiSn / In anode: S1. Prepare a Li metal sheet with a thickness of 50 μm, a Sn metal sheet with a thickness of 50 μm, and In metal, wherein the mass ratio of the Li metal sheet to the Sn metal sheet is 3:1. S2. In the glove box, Li metal sheet and Sn metal sheet are stacked and folded in half. Then, they are pressed into sheets using a pressure of 50 MPa. The folding and pressing steps are repeated 30 times to obtain a LiSn alloy sheet with a thickness of 50 μm. S3. Place a certain amount of metallic In onto the evaporation boat of the vacuum coating machine, set the evaporation program, and set the vacuum degree to 5×10. -4 Pa, heat metallic In to 800℃, use a LiSn alloy sheet as a substrate, and deposit metallic In onto the surface of the LiSn alloy sheet until the thickness of the metallic In coating is 1μm, then stop the evaporation process to prepare a LiSn / In anode.

[0046] Example 4 A method for preparing a LiSn / In anode: S1. Prepare a Li metal sheet with a thickness of 50 μm, a Sn metal sheet with a thickness of 50 μm, and In metal, wherein the mass ratio of the Li metal sheet to the Sn metal sheet is 1:5. S2. In the glove box, Li metal sheet and Sn metal sheet are stacked and folded in half. Then, they are pressed into a sheet using a pressure of 100 MPa. The folding and pressing steps are repeated 30 times to obtain a LiSn alloy sheet with a thickness of 30 μm. S3. Place a certain amount of metallic In onto the evaporation boat of the vacuum coating machine, set the evaporation program, and set the vacuum degree to 5×10. -4Pa, heat metallic In to 1000℃, use a LiSn alloy sheet as a substrate, and deposit metallic In onto the surface of the LiSn alloy sheet until the thickness of the metallic In coating is 2μm, then stop the evaporation process to prepare a LiSn / In anode.

[0047] Example 5 A method for preparing a LiSn / In anode: S1. Prepare a Li metal sheet with a thickness of 50 μm, a Sn metal sheet with a thickness of 50 μm, and In metal, wherein the mass ratio of the Li metal sheet to the Sn metal sheet is 1:1. S2. In the glove box, Li metal sheet and Sn metal sheet are stacked and folded in half. Then, they are pressed into a sheet using a pressure of 100 MPa. The folding and pressing steps are repeated 30 times to obtain a LiSn alloy sheet with a thickness of 30 μm. S3. Place a certain amount of metallic In onto the evaporation boat of the vacuum coating machine, set the evaporation program, and set the vacuum degree to 5×10. -4 Pa, heat metallic In to 1000℃, use a LiSn alloy sheet as a substrate, and deposit metallic In onto the surface of the LiSn alloy sheet until the thickness of the metallic In coating is 10μm, then stop the evaporation process to prepare a LiSn / In anode.

[0048] Example 6 A method for preparing a LiSn / In anode: S1. Prepare a Li metal sheet with a thickness of 50 μm, a Sn metal sheet with a thickness of 50 μm, and In metal, wherein the mass ratio of the Li metal sheet to the Sn metal sheet is 1:1. S2. In the glove box, Li metal sheets and Sn metal sheets are stacked and folded in half. Then, they are pressed into sheets using a pressure of 200 MPa to obtain a LiSn alloy sheet with a thickness of 30 μm. S3. Place a certain amount of metallic In onto the evaporation boat of the vacuum coating machine, set the evaporation program, and set the vacuum degree to 5×10. -4 Pa, heat metallic In to 1000℃, use a LiSn alloy sheet as a substrate, and deposit metallic In onto the surface of the LiSn alloy sheet until the thickness of the metallic In coating is 2μm, then stop the evaporation process to prepare a LiSn / In anode.

[0049] Comparative Example 1 A 50 μm thick Li metal sheet was used as the negative electrode.

[0050] Comparative Example 2 A method for preparing a LiSn anode: S1. Prepare a Li metal sheet with a thickness of 50μm and a Sn metal sheet with a thickness of 50μm. The Li metal sheet and the Sn metal sheet are the same size. S2. In a glove box, Li metal sheets and Sn metal sheets are stacked and folded in half. Then, they are pressed into a sheet using a pressure of 100 MPa. The folding and pressing steps are repeated 30 times to obtain a LiSn alloy sheet with a thickness of 30 μm. The LiSn alloy sheet is used as the negative electrode.

[0051] Comparative Example 3 A method for preparing a Li / In negative electrode: S1. Prepare a Li metal sheet with a thickness of 50μm and In metal; S2. Place a certain amount of metallic In onto the evaporation boat of the vacuum coating machine, set the evaporation program, and set the vacuum degree to 5×10. -4 Pa, heat metallic In to 1000℃, use Li metal sheet as substrate, and deposit metallic In film onto the surface of Li metal sheet until the thickness of metallic In film is 2μm, then stop the evaporation process to prepare Li / In anode.

[0052] Comparative Example 4 A method for preparing a LiSnIn anode: S1. Prepare a Li metal sheet with a thickness of 50μm, a Sn metal sheet with a thickness of 50μm, and an In metal sheet with a thickness of 50μm. All three metal sheets are the same size. S2. In the glove box, Li metal sheet, Sn metal sheet and In metal sheet are stacked in order from top to bottom. First, they are folded in half, and then pressed with a pressure of 100MPa. Repeat the folding and pressing steps 30 times to obtain a LiSnIn alloy sheet with a thickness of 30μm. The LiSnIn alloy sheet is used as the negative electrode of the battery.

[0053] Comparative Example 5 A method for preparing a LiAl / In negative electrode: S1. Prepare a Li metal sheet with a thickness of 50 μm, an Al metal sheet with a thickness of 50 μm, and In metal, wherein the mass ratio of the Li metal sheet to the Al metal sheet is 1:1. S2. In the glove box, Li metal sheet and Al metal sheet are stacked and placed, folded in half, and then pressed with a pressure of 100MPa. Repeat the folding and pressing steps 30 times to obtain a LiAl alloy sheet with a thickness of 30μm. S3. Place a certain amount of metallic In onto the evaporation boat of the vacuum coating machine, set the evaporation program, and set the vacuum degree to 5×10. -4Pa, heat metallic In to 1000℃, use LiAl alloy sheet as substrate, and deposit metallic In film onto the surface of LiAl alloy sheet until the thickness of metallic In film is 2μm, then stop the evaporation process to prepare LiAl / In anode.

[0054] Performance testing The negative electrodes prepared in the above embodiments and comparative examples were used to assemble batteries, and relevant performance tests were conducted.

[0055] (1) Assembly of sulfide lithium metal symmetric batteries: Take out 100mg of sulfide electrolyte LPSC powder and pre-press it into a sheet in a 10mm diameter mold battery (300MPa, 5min). Then, place a negative electrode obtained in the above example and comparative example on both sides of the LPSC sheet as the positive and negative electrodes, respectively. Then pressurize at 100MPa for 30min to assemble a sulfide lithium metal symmetric battery.

[0056] Performance tests were conducted on various sulfide lithium metal symmetric batteries, including the CCD (Critical Current Density) value and cycle performance.

[0057] The CCD value of a battery is tested as follows: Assemble a symmetrical battery into the tester and set the program as follows: the initial current density is 0.1 mA / cm². 2 The charging and discharging time is 1 hour; the current density in the second cycle is the current density of the previous cycle + 0.1 mA / cm². 2 The charging and discharging time is 1 hour. The current density is gradually increased to charge and discharge the battery until an open circuit or short circuit occurs, at which point the charging and discharging is stopped.

[0058] The test method for the cycle performance of the battery is as follows: Assemble the symmetrical battery into the tester and set the program as follows: The current density for the first 3 cycles is 0.1 mA / cm². 2 The charge / discharge time was 1 hour; the current density after the 4th cycle was 0.5 mA / cm². 2 The charging and discharging time is 1 hour, and the current density is kept constant until the battery experiences an open circuit or short circuit, at which point the charging and discharging is stopped.

[0059] The test results are shown in Table 1: Table 1 Performance test results of sulfide lithium metal symmetric batteries assembled with negative electrodes in the embodiments and comparative examples of the present invention.

[0060] (2) Assembly of sulfide lithium metal all-solid-state batteries: 80 mg of ternary material NCM811 and 20 mg of LPSC powder were ground and mixed evenly to obtain a composite material; 100 mg of sulfide electrolyte LPSC powder was taken out and pre-pressed into a sheet in a 10 mm diameter mold battery (100 MPa, 3 min); then 5 mg of the composite material was added to the surface of the electrolyte membrane as the positive electrode and pressed at 300 MPa for 5 min; the negative electrode prepared in the above embodiments and comparative examples was placed on the other side of the sulfide electrolyte sheet, and then pressed at 100 MPa for 30 min to assemble a sulfide lithium metal all-solid-state battery.

[0061] Performance tests were conducted on various sulfide lithium metal all-solid-state batteries: Test method for 0.1C charging capacity: Assemble the all-solid-state battery into the tester and set the program as follows: Set the mass of the positive electrode active material, then set the program to constant rate charge and discharge, the charging rate to 0.1C, the cutoff voltage to 4.2V, and test the 0.1C charging capacity.

[0062] Test method for 0.1C discharge capacity: Assemble the all-solid-state battery into the tester and set the program as follows: Set the mass of the positive electrode active material, then set the program to constant rate charge and discharge, discharge rate of 0.1C, cutoff voltage of 2.5V, and test the 0.1C discharge capacity.

[0063] First Coulomb Efficiency: The first discharge capacity divided by the first charge capacity is the first Coulomb efficiency.

[0064] Test method for 0.5C cycle life: Assemble the all-solid-state battery into the tester and set the program as follows: Set the mass of the positive electrode active material, set the program to constant rate charge and discharge, the charge and discharge rate for the first three cycles is 0.1C, and the charge and discharge voltage range is 2.5~4.2V; thereafter, the charge and discharge rate is 0.5C, and the charge and discharge voltage range is 2.5~4.2V. Take the first cycle of formal charging as the initial capacity A0. When the cycle charge capacity is less than 80% of A0, stop charging and discharging, and record the number of battery charge and discharge cycles.

[0065] The test results are shown in Table 2: Table 2 Performance test results of sulfide lithium metal all-solid-state batteries assembled with negative electrodes in the embodiments and comparative examples of the present invention.

[0066] As can be seen from the data in Table 1, the present invention first prepares LiSn alloy by mechanical rolling, and then deposits a layer of metallic In on the surface of LiSn alloy by vacuum evaporation to form LiSn / In alloy. When LiSn / In anode is used to prepare symmetrical cell, the symmetrical cell can exhibit a higher critical current density (i.e. CCD value) and a longer cycle life at the same current density.

[0067] As can be seen from the data in Table 2, when the LiSn / In anode prepared by the above method is used to prepare lithium sulfide metal all-solid-state batteries, the lithium sulfide metal all-solid-state batteries can exhibit longer cycle life and higher initial coulombic efficiency.

[0068] It should be noted that, in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0069] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A method for preparing a LiSn / In negative electrode, characterized in that, Includes the following steps: First, Li metal sheets and Sn metal sheets are prepared into LiSn alloy sheets by mechanical rolling. Then, metallic In is deposited onto the surface of the LiSn alloy sheet using a vacuum evaporation method to obtain a LiSn / In negative electrode.

2. The method for preparing the LiSn / In anode as described in claim 1, characterized in that, The thickness of the LiSn alloy sheet is 30-70 μm.

3. The method for preparing the LiSn / In anode as described in claim 1, characterized in that, The thickness of the In coating in the LiSn / In anode is 1-5 μm.

4. The method for preparing the LiSn / In anode as described in claim 1, characterized in that, The specific steps of the mechanical rolling method include: stacking Li metal sheets and Sn metal sheets, folding them in half, and then pressing them with a pressure of 2-150 MPa. Repeating the steps of folding and pressing is used to obtain LiSn alloy sheets.

5. The method for preparing the LiSn / In anode as described in claim 4, characterized in that, The number of times the tablet is folded in half and then pressed is 25-50.

6. The method for preparing the LiSn / In anode as described in claim 4, characterized in that, The mass ratio of the Li metal sheet to the Sn metal sheet is (1-3):(1-3).

7. The method for preparing the LiSn / In anode as described in claim 4, characterized in that, The thickness of the Li metal sheet is 20-60 μm; the thickness of the Sn metal sheet is 20-60 μm.

8. The method for preparing the LiSn / In negative electrode as described in claim 1, characterized in that, The specific steps of the vacuum evaporation method include: ≤5×10 -4 Under a vacuum of Pa, metallic In is heated to 800-1200℃ to deposit a metallic In film onto the surface of the LiSn alloy sheet.

9. A LiSn / In negative electrode, characterized in that, It is prepared using the preparation method of LiSn / In anode as described in any one of claims 1-8.

10. An all-solid-state battery, characterized in that, It includes a positive electrode, a sulfide electrolyte, and a LiSn / In negative electrode as described in claim 9.

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