Dry-method negative electrode sheet, preparation method thereof, and solid-state battery

Abstract

This application discloses a dry-process negative electrode sheet and its preparation method, as well as a solid-state battery. The dry-process negative electrode sheet includes a modified sulfide solid electrolyte and a silicon-containing material. The modified sulfide solid electrolyte comprises a sulfide solid electrolyte and a coating layer located on at least a portion of the surface of the sulfide solid electrolyte. The coating layer comprises oxides and / or thiophosphates. This suppresses interfacial side reactions between the silicon-containing material and the sulfide solid electrolyte, reduces the consumption of the sulfide solid electrolyte during cycling, and improves the cycle life of the solid-state battery.

Description

Technical Field

[0001] This application relates to the field of solid-state batteries, specifically to dry-process negative electrode sheets and their preparation methods, and solid-state batteries. Background Technology

[0002] The rapid development of electric vehicles has spurred continuous innovation in battery technology, with solid-state lithium-ion batteries attracting significant attention due to their promise of intrinsic safety and high energy density. High specific capacity anode active materials play a crucial role in achieving high-energy-density sulfide solid-state batteries. While lithium metal anodes possess extremely high theoretical specific capacity, problems such as interfacial side reactions with sulfide solid electrolytes and internal short circuits caused by lithium dendrites remain difficult to resolve in the short term. In contrast, silicon anode materials also exhibit high specific capacity, are chemically more stable, abundant, and environmentally friendly, making them a viable anode material option for sulfide solid-state batteries.

[0003] It should be noted that the above statements are only used to provide background information related to this application and do not necessarily constitute prior art. Summary of the Invention

[0004] In a first aspect, this application proposes a dry-process negative electrode, comprising: a modified sulfide solid electrolyte and a silicon-containing material; wherein the modified sulfide solid electrolyte includes a sulfide solid electrolyte and a coating layer located on at least a portion of the surface of the sulfide solid electrolyte, the coating layer comprising oxides and / or thiophosphates. This can suppress the occurrence of interfacial side reactions between the silicon-containing material and the sulfide solid electrolyte, reduce the consumption of the sulfide solid electrolyte during cycling, and improve the cycle life of the solid-state battery.

[0005] In some embodiments, the coating layer includes Al2O3, ZnO, Li3PS4, and Li7P3S. 11 At least one of the following. Thus, the coating layer can prevent direct contact between the silicon-containing material and the sulfide solid electrolyte, thereby suppressing interfacial side reactions between the two, and at the same time helping to build stable lithium-ion channels and reduce the internal resistance of the solid-state battery.

[0006] In some embodiments, the thickness of the coating layer is 1 nm-20 nm; optionally, 1 nm-10 nm. This reduces side reactions between the silicon-containing material and the sulfide solid electrolyte while minimizing obstruction to lithium-ion transport.

[0007] In some embodiments, the silicon-containing material is spherical and / or quasi-spherical in shape. This helps to mitigate the volume expansion of the silicon-containing material, improve the structural stability of the dry-process negative electrode, and allows the silicon-containing material to contact the sulfide solid electrolyte more stably, achieving close packing and improving ion transport efficiency and energy density.

[0008] In some embodiments, the particle size of the silicon-containing material is 50 nm-500 nm; optionally, 50 nm-300 nm. This helps to reduce the mechanical stress of the silicon-containing material, alleviate volume expansion, shorten the lithium-ion transport path, and increase the contact area between the silicon-containing material and the modified sulfide solid electrolyte.

[0009] In some embodiments, the sulfide solid electrolyte includes (100-x)Li₂S₁₀P₂S₅, Li₃PS₄, Li₇P₃S₁₀, Li₆PS₅Cl, Li₆PS₅Br, Li₆PS₅I, Li 5.5 PS 4.5 Br 1.5 Li 5.5 PS 4.5 Cl 1.5 At least one of them. This is beneficial for improving the ionic conductivity of the dry-process negative electrode.

[0010] In some embodiments, the dry-process negative electrode further includes a conductive agent, which includes at least one of conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, vapor-grown carbon fibers, graphene, and acetylene black. This is beneficial for improving the electronic conductivity of the dry-process negative electrode.

[0011] In some embodiments, the mass ratio of the silicon-containing material, the modified sulfide solid electrolyte, and the conductive agent is (50-80):(10-50):(0-10). This is beneficial for improving the ionic conductivity, electronic conductivity, and energy density of the dry-process negative electrode.

[0012] In a second aspect, this application proposes a method for preparing a dry-process negative electrode sheet, comprising: placing a sulfide solid electrolyte in an atomic layer deposition reaction chamber, alternately introducing a metal precursor and a reaction source, and obtaining a modified sulfide solid electrolyte after deposition; mixing the modified sulfide solid electrolyte, a silicon-containing material, and a conductive agent to obtain a mixed powder; and, under an inert atmosphere, mixing the mixed powder with spherical stones and then ball-milling the mixture, and subjecting the ball-milled powder material to pressure treatment to obtain the dry-process negative electrode sheet. This application, by forming a coating layer on the surface of the sulfide solid electrolyte, can effectively suppress the interfacial reaction between the sulfide solid electrolyte and the silicon-containing material, effectively improving the cycle life of the solid-state battery. Furthermore, the preparation method is simple and easy to scale up for mass production.

[0013] In some embodiments, the metal precursor includes at least one of trimethylaluminum, a lithium source, and dimethylzinc; and / or, the reaction source includes at least one of H2O gas, oxygen, ozone, hydrogen sulfide, trimethyl phosphate, and PH3. This facilitates the formation of a uniform coating layer on the surface of the sulfide solid electrolyte, and since no liquid is present during the formation of the coating layer, it has minimal impact on the electrochemical stability of the sulfide solid electrolyte.

[0014] In some embodiments, the deposition temperature is 60°C-400°C. This facilitates control of the deposition rate and improves the uniformity and density of the coating layer.

[0015] In some embodiments, the mass ratio of the ball milling stones to the mixed powder is (10:1)-(40:1); and / or, the ball milling speed is 50 r / min-500 r / min; and / or, the ball milling time is 1 h-20 h. This improves ball milling efficiency and promotes thorough compounding of the mixed powder.

[0016] In a third aspect, this application proposes a solid-state battery, comprising the dry-process negative electrode sheet described in the first aspect of this application or a dry-process negative electrode sheet prepared using the method described in the second aspect of this application. Therefore, this solid-state battery has a long cycle life. Attached Figure Description

[0017] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, wherein,

[0018] Figure 1 This is an elemental distribution diagram of the modified sulfide solid electrolyte prepared in Example 1 of this application; Figure 2 This is a TEM image of the modified sulfide solid electrolyte prepared in Example 1 of this application; Figure 3 The graphs show the cycle performance and coulombic efficiency of the solid-state batteries of Example 1 and Comparative Example 1 of this application. Detailed Implementation

[0019] The embodiments of this application are described in detail below, with examples of these embodiments shown in the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0020] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0021] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are open-ended expressions, meaning they include what is specified in this application but do not exclude other aspects.

[0022] In the description of this application, all figures disclosed herein, whether or not the words "approximately" or "about" are used, are approximate values. Each figure may vary by less than 10% or by a difference that is considered reasonable by one of the art, such as 1%, 2%, 3%, 4%, or 5%.

[0023] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0024] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0025] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0026] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0027] Because silicon-containing materials have inherently poor ionic and electronic conductivity, they need to be mixed with solid electrolytes and conductive agents to prepare dry-process negative electrode sheets. However, silicon-containing materials undergo side reactions with sulfide solid electrolytes during charge and discharge, resulting in the loss of active lithium, low coulombic efficiency, and battery capacity decay. Furthermore, conductive agents are often added to the negative electrode sheets, which promote interfacial side reactions between silicon materials and solid electrolytes, further depleting the solid electrolyte and reducing battery cycle life. To suppress interfacial reactions between silicon-containing materials and solid electrolytes, coating of either the silicon-containing material or the solid electrolyte is commonly used, but this presents several problems: 1) Surface coating of silicon negative electrode materials cannot effectively cope with the exposure of new interfaces due to the volume expansion of silicon-containing materials during long-term cycling. 2) Due to the inherent instability of sulfide solid electrolytes, wet coating often affects the structure of the solid electrolyte, while dry coating methods such as ball milling can result in uneven coating layers.

[0028] In a first aspect, this application proposes a dry-process negative electrode, comprising: a modified sulfide solid electrolyte and a silicon-containing material; wherein the modified sulfide solid electrolyte includes a sulfide solid electrolyte and a coating layer located on at least a portion of the surface of the sulfide solid electrolyte, the coating layer comprising oxides and / or thiophosphates. During charge and discharge, the coating layer can form an inert interface layer in situ with the silicon-containing material, i.e., an electrochemical reaction occurs to generate a stable phase. This inert interface layer can physically isolate the silicon-containing material from direct contact with the sulfide solid electrolyte, which is the first step in suppressing side reactions. Furthermore, since the inert interface layer is electronically insulated but ionically conductive, this characteristic can suppress the reductive decomposition reaction of the sulfide solid electrolyte at low potentials. Therefore, the occurrence of interfacial side reactions between the silicon-containing material and the sulfide solid electrolyte can be suppressed, reducing the consumption of the sulfide solid electrolyte during cycling, lowering interfacial impedance, improving coulombic efficiency, and thus improving the cycle life of the solid-state battery. Compared to conventional methods of coating silicon-containing materials, coating sulfide solid electrolytes does not crack due to the volume expansion and contraction of silicon materials, thus maintaining the stability and integrity of the coating layer during charge and discharge processes. Furthermore, for nano-silicon materials, due to their small particle size, surface modification is difficult, hindering large-scale production and application.

[0029] In some embodiments, the coating layer includes Al2O3, ZnO, Li3PS4, and Li7P3S. 11At least one of the following. Thus, the coating layer can prevent direct contact between the silicon-containing material and the sulfide solid electrolyte, thereby suppressing interfacial side reactions between the two, and at the same time helping to build stable lithium-ion channels and reduce the internal resistance of the solid-state battery.

[0030] In some embodiments, the thickness of the coating layer is 1 nm-20 nm, for example, it can be 1 nm, 2 nm, 5 nm, 10 nm, 13 nm, 15 nm, 18 nm or 20 nm, etc.; optionally, 1 nm-10 nm. Thus, while reducing side reactions between the silicon-containing material and the sulfide solid electrolyte, it also minimizes the obstruction to lithium-ion transport.

[0031] In some embodiments, the silicon-containing material is spherical and / or quasi-spherical in shape. This helps to mitigate the volume expansion of the silicon-containing material, improve the structural stability of the dry-process negative electrode, and allows the silicon-containing material to contact the sulfide solid electrolyte more stably, achieving close packing and improving ion transport efficiency and energy density.

[0032] In some embodiments, the particle size of the silicon-containing material is 50nm-500nm, for example, it can be 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, or 500nm; optionally, it is 50nm-300nm. This helps to reduce the mechanical stress of the silicon-containing material, alleviate volume expansion, shorten the lithium-ion transport path, and increase the contact area between the silicon-containing material and the modified sulfide solid electrolyte.

[0033] In some embodiments, the sulfide solid electrolyte includes (100-x)Li₂S₁₀P₂S₅, Li₃PS₄, Li₇P₃S₁₀, Li₆PS₅Cl, Li₆PS₅Br, Li₆PS₅I, Li 5.5 PS 4.5 Br 1.5 Li 5.5 PS 4.5 Cl 1.5 At least one of them. This is beneficial for improving the ionic conductivity of the dry-process negative electrode.

[0034] In some embodiments, the dry-process negative electrode further includes a conductive agent, which includes at least one of conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, vapor-grown carbon fiber (VGCF), graphene, and acetylene black. This is beneficial for improving the electronic conductivity of the dry-process negative electrode.

[0035] In some embodiments, the mass ratio of the silicon-containing material, the modified sulfide solid electrolyte, and the conductive agent is (50-80):(10-50):(0-10), for example, 50:50:0, 80:20:0, 80:10:10, 70:20:10, 60:30:10, or 55:40:5. This is beneficial for improving the ionic conductivity, electronic conductivity, and energy density of the dry-process negative electrode.

[0036] In a second aspect, this application proposes a method for preparing a dry negative electrode sheet. This method utilizes atomic layer deposition (ALD) to form a coating layer on the surface of a sulfide solid electrolyte. The coating thickness is controllable and the coating layer is uniform, without damaging the structure of the sulfide solid electrolyte itself. This avoids the damage to the sulfide solid electrolyte structure caused by wet coating and the unevenness of the dry coating layer. It effectively isolates the sulfide solid electrolyte from silicon-containing materials, and the preparation method is simple and easy to scale up for mass production. Specifically, the method includes: S1: The sulfide solid electrolyte is placed in the atomic layer deposition reaction chamber, and the metal precursor and reaction source are alternately introduced. After deposition, the modified sulfide solid electrolyte is obtained.

[0037] In some embodiments, the metal precursor includes at least one of trimethylaluminum, a lithium source (such as lithium 2,2,6,6-tetramethyl-3,5-heptadecylene (LiTMHD) or lithium tert-butoxide (LTB), and dimethylzinc; and / or, the reaction source includes at least one of H2O gas, oxygen, ozone, hydrogen sulfide, trimethyl phosphate (TMP), and pH3. This facilitates the formation of a uniform coating layer on the surface of the sulfide solid electrolyte, and since no liquid is present during the formation of the coating layer, it has minimal impact on the electrochemical stability of the sulfide solid electrolyte.

[0038] As an example, when the coating layer is Al2O3, trimethylaluminum and H2O gas can be injected sequentially into the atomic layer deposition reaction chamber, so that it can complete the adsorption and chemical reaction on the surface of the sulfide solid electrolyte.

[0039] As an example, when the coating layer is ZnO, dimethyl zinc and H2O gas can be alternately introduced into the atomic layer deposition reaction chamber to allow it to complete adsorption and chemical reaction on the surface of the sulfide solid electrolyte.

[0040] As an example, the coating layer is thiophosphate LPS (Li3PS4, Li7P3S). 11 During the atomic layer deposition reaction chamber, LTB, phosphorus-containing precursors (such as trimethyl phosphate) and H2S can be sequentially injected into the chamber, allowing them to complete adsorption and chemical reaction on the surface of the sulfide solid electrolyte.

[0041] In some embodiments, the deposition temperature is 60℃-400℃, for example, it can be 60℃, 80℃, 100℃, 150℃, 200℃, 250℃, 300℃, 350℃, or 400℃. This is beneficial for controlling the deposition rate and improving the uniformity and density of the coating layer.

[0042] In some embodiments, deposition includes 1-500 cycles, and the thickness of the coating layer can be adjusted by controlling the number of cycles.

[0043] S2: The modified sulfide solid electrolyte, silicon-containing material and conductive agent are mixed to obtain a mixed powder.

[0044] It is understood that this application does not specify the mixing method of the modified sulfide solid electrolyte, silicon-containing material and conductive agent. For example, the modified sulfide solid electrolyte, silicon-containing material and conductive agent can be added to a ball mill jar with zirconia balls under Ar atmosphere protection in a certain mass ratio.

[0045] S3: Under an inert atmosphere, the mixed powder and pebbles are mixed and then ball-milled. The ball-milled powder material is then subjected to pressure treatment to obtain the dry negative electrode sheet.

[0046] In some embodiments, the mass ratio of the pebbles to the mixed powder is (10:1)-(40:1), for example, it can be 10:1, 15:1, 20:1, 25:1, 30:1, 35:1 or 40:1.

[0047] In some embodiments, the rotational speed of the ball milling process is 50 r / min to 500 r / min, for example, it can be 50 r / min, 100 r / min, 150 r / min, 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min or 500 r / min, etc.

[0048] In some embodiments, the ball milling treatment time is 1h-20h, for example, it can be 1h, 5h, 8h, 10h, 13h, 15h, 18h or 20h.

[0049] Meeting the above ball milling conditions is beneficial to improving ball milling efficiency and promoting the full compounding of mixed powders.

[0050] In some embodiments, the inert atmosphere may be argon. This prevents oxidation of silicon-containing materials and modified sulfide solid electrolytes.

[0051] In some embodiments, the spheres may be zirconia spheres.

[0052] It should be noted that the powder material obtained after ball milling can be stored for later use. When it is necessary to assemble a solid-state battery, it can be bonded to the electrolyte membrane layer and then subjected to pressure treatment.

[0053] In a third aspect, this application proposes a solid-state battery, comprising the dry-process negative electrode sheet described in the first aspect of this application or a dry-process negative electrode sheet prepared using the method described in the second aspect of this application. Therefore, this solid-state battery has a long cycle life.

[0054] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0055] The following specific embodiments illustrate the solution of this application. It should be noted that these embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0056] Example 1 Li6PS5Cl was dispersed in an atomic layer deposition reaction chamber, and trimethylaluminum and H2O gas were injected sequentially. The deposition temperature was 200℃ and the number of cycles was 100, forming an Al2O3 coating layer with a thickness of 3nm on the surface of Li6PS5Cl.

[0057] Nano-silicon particles, coated Li6PS5Cl, and VGCF were mixed in a mass ratio of 80:15:5 and added to a high-energy ball mill jar equipped with zirconia balls, wherein the mass ratio of zirconia balls to mixed powder was 30:1. The ball milling speed was set to 200 r / min, with each cycle consisting of 5 min of ball milling time and 5 min of settling time. 36 cycles were performed, for a total ball milling time of 6 h. The composite material was collected in an Ar atmosphere glove box.

[0058] Example 2 The difference from Example 1 is that the number of cycles is 200 and the coating thickness is 6nm.

[0059] Example 3 The difference from Example 1 is that Li6PS5Cl is dispersed in the atomic layer deposition reaction chamber, and dimethyl zinc and H2O gas are injected sequentially. The deposition temperature is 150°C and the number of cycles is 120, forming a ZnO coating layer with a thickness of 3nm on the surface of Li6PS5Cl.

[0060] Example 4 The difference from Example 1 is that the total ball milling time for 72 cycles is 12 hours.

[0061] Example 5 The difference from Example 1 is that the ball milling speed is 400 r / min.

[0062] Example 6 The difference from Example 1 is that the mass ratio of zirconia balls to mixed powder is 15:1.

[0063] Example 7 The difference from Example 1 is that the number of cycles is 40 and the coating thickness is 1 nm.

[0064] Example 8 The difference from Example 1 is that the number of cycles is 840 and the coating thickness is 20nm.

[0065] The assembly process of the half-cell from the examples is as follows: 100 mg of Li6PS5Cl is weighed as an intermediate layer, and a pressure of 1t is applied and held for 1 min; 2 mg of the composite material prepared in Examples 1-8 is weighed and added to one side of the electrolyte, and a pressure of 3t is applied and held for 1 min; Li-In sheet is used on the other side, and a pressure of 0.5t is applied and held for 1 min; finally, the mold shell is used to apply an external pressure of 1t to the battery and hold.

[0066] Comparative Example 1 The difference from Example 1 is that Li6PS5Cl was not coated or modified.

[0067] Comparative Example 2 The difference from Example 1 is that Li6PS5Cl was not coated and modified, and VGCF was replaced with conductive carbon black.

[0068] Comparative Example 3 The difference from Example 1 is that Li6PS5Cl was not coated and modified, and VGCF was replaced with conductive carbon black; the total ball milling time for 72 cycles was 12 hours.

[0069] Comparative Example 4 The difference from Example 1 is that: Li6PS5Cl was not coated and modified, and VGCF was replaced with conductive carbon black; the ball milling speed was 400 r / min.

[0070] Comparative Example 5 The difference from Example 1 is that: Li6PS5Cl was not coated and modified, and VGCF was replaced with conductive carbon black; the mass ratio of zirconium oxide balls to mixed powder was 15:1.

[0071] Comparative Example 6 The difference from Example 1 is that the sulfide solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 Li 5.5 PS 4.5 Cl 1.5 Coating modification is performed.

[0072] Comparative Example 7 The difference from Example 1 is that the coating layer is a nitride material TiN. The specific coating method is as follows: Li6PS5Cl is dispersed in the atomic layer deposition reaction chamber, TiCl4 and N2 are injected sequentially, the deposition temperature is 350℃, the number of cycles is 100, and a TiN coating layer with a thickness of 3nm is formed on the surface of Li6PS5Cl.

[0073] Nano-silicon particles, coated Li6PS5Cl, and VGCF were mixed in a mass ratio of 80:15:5 and added to a high-energy ball mill jar equipped with zirconia balls, wherein the mass ratio of zirconia balls to mixed powder was 30:1. The ball milling speed was set to 200 r / min, with each cycle consisting of 5 min of ball milling time and 5 min of settling time. 36 cycles were performed, for a total ball milling time of 6 h. The composite material was collected in an Ar atmosphere glove box.

[0074] The assembly process of the half-cells from Comparative Examples 1-5 and Comparative Example 7 is as follows: 100 mg of Li6PS5Cl solid electrolyte is weighed as the intermediate layer, and a pressure of 1t is applied and held for 1 min; 2 mg of the composite material prepared in Comparative Examples 1-5 is weighed and added to one side of the electrolyte, and a pressure of 3t is applied and held for 1 min; Li-In sheet is used on the other side, and a pressure of 0.5t is applied and held for 1 min; finally, the mold shell is used to apply an external pressure of 1t to the battery and hold.

[0075] The process of assembling the half-cell from Comparative Example 6 is as follows: Weigh 70 mg of Li 5.5 PS 4.5 Cl 1.5 A pressure of 1 t was applied and held for 1 min. Then, 30 mg of Li6PS5Cl was added to one side, and a pressure of 1 t was applied and held for 1 min to form an intermediate layer. 2 mg of the composite material prepared in Comparative Example 6 was weighed and added to the electrolyte Li. 5.5 PS 4.5 Cl 1.5 On one side, apply a pressure of 3t and hold for 1 minute; on the other side, use a Li-In sheet, apply a pressure of 0.5t and hold for 1 minute, and finally use a mold shell to apply an external pressure of 1t to the battery and hold.

[0076] The mold batteries assembled in the above embodiments and comparative examples were subjected to charge-discharge tests at 0.1C and 0.3C, with a test voltage range of 0.005V-1.5V (vs Li / Li). + The test was conducted at room temperature, and the results are shown in Table 1.

[0077] Table 1

[0078] from Figure 1 The surface elemental distribution diagram of Example 1 shows that Al and O elements are relatively uniformly distributed on the surface of the sulfide solid electrolyte, indicating that Al2O3 was successfully coated on the surface of the sulfide solid electrolyte. Figure 2 An amorphous thin film of approximately 3 nm was observed to form on the surface of the sulfide solid electrolyte, indicating that Al2O3 was uniformly coated on the surface of the sulfide solid electrolyte. Furthermore, the crystal structure of the internal substrate material was clearly observed, with a crystal plane spacing of approximately 0.16 nm, corresponding to the (311) crystal plane of the sulfide solid electrolyte.

[0079] Figure 3 To compare the cycling performance of the batteries in Example 1 and Example 1 at 0.3C (after one cycle of activation at 0.1C), the cycling performance (both negative electrode charging capacity) was analyzed. After 40 cycles, the capacity retention rate of Example 1 was 91%, while that of Comparative Example 1 was 83.7%. Furthermore, around cycle 40, Comparative Example 1 showed a significant capacity drop, indicating that the interface between the silicon material and the sulfide electrolyte deteriorated rapidly and irreversibly. After 60 cycles, the capacity retention rate of Example 1 was 85.1%, while that of Comparative Example 1 was 39.6%. The results show that the cycling of Comparative Example 1 was unstable during the cycling process, while the cycling stability of Example 1 was significantly improved. By comparing the coulombic efficiency during the cycling process, it was found that after the fourth cycle, the coulombic efficiency of Example 1 could be stably maintained above 99%, while the coulombic efficiency of Comparative Example 1 was unstable. Although some cycles reached above 99%, the overall efficiency was slightly lower than that of the coated sample.

[0080] As can be seen from Table 1, the dry negative electrode uses a sulfide solid electrolyte with surface coating. The in-situ generated high ion conductivity inert interface layer between silicon and sulfide solid electrolyte can effectively suppress interface side reactions, thereby improving the cycle stability of the negative electrode.

[0081] In Comparative Example 7, the TiN coating layer is a nitride material with good conductivity, but it is not insulating. Therefore, it cannot suppress the side reactions of the sulfide solid electrolyte, but instead exacerbates the occurrence of side reactions, resulting in poor cycle performance of the solid battery.

[0082] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A dry-process negative electrode sheet, characterized in that, include: Modified sulfide solid electrolytes and silicon-containing materials; The modified sulfide solid electrolyte comprises a sulfide solid electrolyte and a coating layer located on at least a portion of the surface of the sulfide solid electrolyte, the coating layer comprising oxides and / or thiophosphates.

2. The dry-process negative electrode sheet according to claim 1, characterized in that, The coating layer includes Al2O3, ZnO, Li3PS4, and Li7P3S. 11 At least one of them.

3. The dry-process negative electrode sheet according to claim 1 or 2, characterized in that, The thickness of the coating layer is 1nm-20nm; optionally, 1nm-10nm.

4. The dry-process negative electrode sheet according to claim 1, characterized in that, The silicon-containing material may be spherical or quasi-spherical in shape.

5. The dry-process negative electrode sheet according to claim 4, characterized in that, The particle size of the silicon-containing material is 50nm-500nm; optionally, 50nm-300nm.

6. The dry-process negative electrode sheet according to claim 1, characterized in that, The sulfide solid electrolyte includes (100-x)Li₂S⁻⁴P₂S₅, Li₃PS₄, Li₇P₃S₁₁, Li₆PS₅Cl, Li₆PS₅Br, Li₆PS₅I, and Li₂S⁻⁴. 5.5 PS 4.5 Br 1.5 Li 5.5 PS 4.5 Cl 1.5 At least one of them.

7. The dry-process negative electrode sheet according to claim 1, characterized in that, It also includes a conductive agent, which includes at least one of conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, vapor-grown carbon fibers, graphene, and acetylene black.

8. The dry-process negative electrode sheet according to claim 7, characterized in that, The mass ratio of the silicon-containing material, the modified sulfide solid electrolyte, and the conductive agent is (50-80):(10-50):(0-10).

9. A method for preparing the dry-process negative electrode sheet according to any one of claims 1-8, characterized in that, include: The sulfide solid electrolyte was placed in the atomic layer deposition reaction chamber, and the metal precursor and reaction source were alternately introduced. After deposition, the modified sulfide solid electrolyte was obtained. The modified sulfide solid electrolyte, silicon-containing material, and conductive agent are mixed to obtain a mixed powder; Under an inert atmosphere, the mixed powder and pebbles are mixed and then ball-milled. The ball-milled powder material is then subjected to pressure treatment to obtain the dry negative electrode sheet.

10. The method according to claim 9, characterized in that, The metal precursor includes at least one of trimethylaluminum, lithium source, and dimethylzinc; and / or, The reaction source includes at least one of H2O gas, oxygen, ozone, hydrogen sulfide, trimethyl phosphate, and PH3; and / or, The deposition temperature is 60℃-400℃.

11. The method according to claim 9, characterized in that, The mass ratio of the pebbles to the mixed powder is (10:1)-(40:1); and / or, The ball milling process is performed at a rotation speed of 50 r / min to 500 r / min; and / or, The ball milling process takes 1-20 hours.

12. A solid-state battery, characterized in that, Includes the dry negative electrode sheet as described in any one of claims 1-8 or the dry negative electrode sheet prepared by the method described in any one of claims 9-11.

Images