Solid-state battery cell, negative electrode sheet, preparation method therefor, and related apparatus

Abstract

A solid-state battery cell, a negative electrode sheet, a preparation method therefor, and a related apparatus. The solid-state battery cell comprises a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode active layer provided on at least one side of the negative electrode current collector; the negative electrode active layer comprises a carbon material and a binder, the binder comprising a structural unit (formula I) or a tautomer thereof, wherein n = 10000-100000; and the carbon material is connected to the binder. The solid-state battery cell addresses the problems of low initial Coulombic efficiency and poor cycling performance in solid-state batteries when a carbon material is used as a negative electrode material.

Description

Solid-state battery cells, negative electrode sheets and their preparation methods, and related equipment Technical Field

[0001] This application relates to the field of battery technology, and in particular to solid-state battery cells, negative electrode sheets, their preparation methods, and related apparatus. Background Technology

[0002] Carbon materials have advantages such as low cost, high specific capacity, high conductivity, and good stability, and are widely used as anode materials in solid-state batteries. However, in practice, it has been found that solid-state batteries using carbon materials as anode materials often suffer from low initial efficiency and poor cycle performance. Summary of the Invention

[0003] This application is made in view of the above-mentioned technical problems, and its purpose is to solve the problems of insufficient first-efficiency and cycle performance of solid-state batteries when carbon materials are used as negative electrode materials.

[0004] To achieve the above objectives, this application provides a solid-state battery cell, a negative electrode sheet, a method for preparing the same, and related apparatus.

[0005] The first aspect of this application provides a solid-state battery cell, including a negative electrode sheet, the negative electrode sheet including a negative current collector and a negative active layer disposed on at least one side of the negative current collector, the negative active layer including a carbon material and a binder, the binder including a structural unit as shown in Formula I or a tautomer thereof; the carbon material is connected to the binder;

[0006] Formula I, n=10000~100000.

[0007] The solution in this application embodiment can effectively improve the first-efficiency and cycle performance of solid-state batteries using carbon materials as a negative electrode material. The mechanism may include:

[0008] On the one hand, the carbon material is connected to the binder, and the segments of the binder connected to the carbon material can replace the oxygen-containing functional groups on the surface of the carbon material, reducing the number of oxygen-containing functional groups and alleviating the lithium swallowing phenomenon caused by oxygen-containing functional groups, thus reducing the loss of active lithium. On the other hand, the binder includes structural units as shown in Formula I or their tautomers. The conjugated structure in this structural unit provides a fast ion / electron transport channel, thereby forming a high ion / electron transport network, which can improve the ion / electron transport performance of the negative electrode.

[0009] Therefore, the embodiments of this application can effectively improve the first efficiency and cycle performance of solid-state batteries by simultaneously improving the lithium swallowing problem of oxygen-containing functional groups on the surface of carbon materials and the obstacle problem of ion / electron transport by binders.

[0010] In some embodiments, the binder includes cyclized PAN (cyclized polyacrylonitrile) polymers.

[0011] Cyclic PAN polymers have high ion / electron transport capabilities, which are beneficial to improving the ion / electron transport performance of the negative electrode. In addition, cyclic PAN polymers have high viscosity, which can improve the cohesion of the negative electrode sheet. Under the combined effect, they can effectively improve the first efficiency and cycle performance of solid-state batteries.

[0012] In some embodiments, the binder content in the negative electrode active layer is 3% to 8% by mass, optionally 3% to 5%.

[0013] At this content, the binder can effectively bond the carbon material tightly, improve the cohesion of the negative electrode sheet, and enhance the ion / electron transport performance of the negative electrode sheet. At the same time, the binder can be uniformly dispersed in the negative electrode active layer at this content, and will not occupy too much of the proportion of carbon material used to provide capacity, which is beneficial to improving the energy density of the negative electrode sheet.

[0014] In some embodiments, the C / O mass ratio (the mass ratio of carbon to oxygen) of the carbon material is above 1000, optionally between 1000 and 2000. A C / O mass ratio of above 1000 in the carbon material means that the content of oxygen-containing functional groups is relatively low, which can alleviate the lithium swallowing problem caused by oxygen-containing functional groups.

[0015] In some embodiments, the carbon material includes one or more of silicon-carbon (a compound or composite material containing silicon and carbon), graphite (artificial graphite, natural graphite), mesophase carbon microspheres, soft carbon, and hard carbon. These carbon materials typically retain oxygen-containing functional groups on their surface during processing and use. The solution described in this application can effectively reduce the number of oxygen-containing functional groups on the surface of these carbon materials, improving the lithium absorption problem caused by these functional groups, and enabling solid-state batteries using these carbon materials as anode materials to have high initial efficiency and good cycle performance.

[0016] A second aspect of this application provides a negative electrode sheet, including a negative electrode current collector and a negative electrode active layer disposed on at least one side of the negative electrode current collector. The negative electrode active layer includes a carbon material and a binder. The binder includes a structural unit as shown in Formula I or a tautomer thereof. The carbon material is connected to the binder.

[0017] Formula I, n=10000~100000.

[0018] The negative electrode sheet of this application embodiment can effectively improve the first efficiency and cycle performance of solid-state batteries using carbon materials as negative electrode active materials.

[0019] A third aspect of this application provides a method for preparing a negative electrode sheet, comprising:

[0020] Carbon materials are cyanided to obtain cyano-carbon materials;

[0021] A negative electrode active layer comprising carbon cyanide material and binder precursor is prepared on at least one side of the negative electrode current collector, wherein the binder precursor comprises the structural unit shown in Formula II.

[0022] This causes a crosslinking reaction between the cyanocarbon material and the binder precursor.

[0023] Formula II, n = 10000 ~ 100000.

[0024] The negative electrode sheet prepared in this application embodiment can effectively improve the first-efficiency and cycle performance of solid-state batteries using carbon materials as negative electrode active materials. The mechanism may include:

[0025] By cyaniding carbon materials and then crosslinking the resulting cyano-treated carbon materials with a binder precursor containing the structural unit shown in Formula II, the cyano groups can replace the oxygen-containing functional groups on the surface of the carbon materials, reducing the number of oxygen-containing functional groups and mitigating lithium absorption caused by these groups, thus reducing the loss of active lithium. Furthermore, the cyano groups on the surface of the cyano-treated carbon materials can participate in the crosslinking reaction, forming a crosslinked product with the structural unit shown in Formula I or its tautomers together with the binder precursor. This crosslinked product with the structural unit has high viscosity and can be used as a binder. Since part of the binder's structure originates from the cyano groups on the surface of the cyano-treated carbon materials, the binder can connect to the carbon materials and utilize the conjugated structure in its Formula I structural unit or its tautomers to provide a fast ion / electron transport channel, thereby forming a high ion / electron transport network that can improve the ion / electron transport performance of the negative electrode.

[0026] Therefore, the preparation method of this application embodiment can effectively improve the first efficiency and cycle performance of solid-state batteries by simultaneously improving the lithium swallowing problem of oxygen-containing functional groups on the surface of carbon materials and the obstacle problem of ion / electron transport by binders.

[0027] In some embodiments, the cyano group content in the cyano-modified carbon material is 2.5% to 6% by mass, optionally 3.5% to 4%. By modifying the carbon material with a certain amount of cyano groups, the number of oxygen-containing functional groups on the surface of the carbon material can be reduced, alleviating the lithium swallowing phenomenon caused by oxygen-containing functional groups and reducing the loss of active lithium.

[0028] In some embodiments, the method for cyaniding carbon materials includes reacting the carbon material with a cyaniding reagent. The cyanidation reaction can be carried out in the presence of an alkaline environment and a catalyst. The cyano groups in the cyaniding reagent can replace oxygen-containing functional groups on the surface of the carbon material, reducing lithium absorption by these groups and thus improving the initial efficiency and cycle performance of solid-state batteries.

[0029] The cyaniding reagent includes one or more of trimethylcyanosilane (TMSCN), acetone cyanohydrin, sodium cyanide, potassium cyanide, hydrogen cyanide, and acrylonitrile.

[0030] In some embodiments, the mass ratio of carbon material to cyanide reagent is 100:(10-20), optionally 100:(15-17). By combining carbon material and cyanide reagent in an appropriate ratio, a certain amount of cyano groups can be modified onto the carbon material, reducing the number of oxygen-containing functional groups on the carbon material surface, mitigating lithium absorption caused by oxygen-containing functional groups, and reducing the loss of active lithium.

[0031] In some embodiments, the cyanidation treatment temperature is 20°C to 50°C, optionally 25°C to 40°C. The cyanidation treatment time is 5 hours to 20 hours, optionally 8 hours to 12 hours. Treating at this temperature for a certain time allows for successful modification of the carbon material surface with cyano groups.

[0032] In some embodiments, the binder precursor includes polyacrylonitrile (PAN) polymers. During the crosslinking reaction, PAN polymers can form cyclized PAN polymers, and the molecular chains of these cyclized PAN polymers can connect with carbon material particles, thereby tightly binding the carbon material particles together and improving the cohesion of the negative electrode. Furthermore, the cyclized PAN polymers possess high ion / electron transport capabilities, which is beneficial for improving the ion / electron transport performance of the negative electrode, thus improving the first-efficiency and cycle performance of the solid-state battery.

[0033] In some embodiments, the binder precursor has a mass content of 4% to 9% in the negative electrode active layer, optionally 4% to 6%. At this content, a certain amount of binder comprising the structural unit shown in Formula I or its tautomers and possessing high ion / electron transport performance can be generated using the binder precursor. This reduces the binder's obstruction to ion / electron transport, giving the negative electrode suitable conductivity. Furthermore, both the binder precursor and the generated binder precursor have good uniformity in the negative electrode active layer, which is beneficial for improving the first-efficiency and cycle performance of solid-state batteries.

[0034] In some embodiments, the method for causing the cyanocarbon material to undergo a crosslinking reaction with the binder precursor includes: heat treatment under a protective atmosphere at a temperature of 200°C to 350°C, optionally 280°C to 320°C; and heat treatment for a time of 4 hours to 9 hours, optionally 4 hours to 6 hours. Heat treatment under a protective atmosphere allows the binder precursor, comprising the structural unit shown in Formula II, to undergo a crosslinking reaction with the cyanocarbon material, and cyclization occurs during the crosslinking process to generate a binder comprising the structural unit shown in Formula I or its tautomers. The binder is then connected to the carbon material, which is beneficial for constructing a high ion / electron transport network and reducing the binder's obstruction of ion / electron transport. Furthermore, by controlling the temperature and time of heat treatment, the generated binder can have a suitable degree of cyclization, which can improve the cohesion of the negative electrode sheet and give it suitable conductivity. When the negative electrode sheet is used in solid-state batteries, it can have good compatibility with most of the solid electrolyte membranes in the solid-state battery, and will not cause the solid electrolyte membrane to decompose due to excessive conductivity. Moreover, the binder generated at this content can tightly bond the carbon material, improve the cohesion of the negative electrode sheet, and form a structurally stable negative electrode sheet, which is conducive to improving the first efficiency and cycle performance of solid-state batteries.

[0035] This application also provides some related devices, including battery devices, energy storage devices, and power consumption devices.

[0036] The battery device includes multiple solid-state battery cells.

[0037] The solid-state battery cell of this application embodiment has good cycle performance. Therefore, applying the solid-state battery cell to a battery device can help improve the cycle performance of the battery device and extend the service life of the battery device.

[0038] Energy storage devices include multiple solid-state battery cells or multiple battery devices, which are used to store or provide electrical energy.

[0039] The aforementioned solid-state battery cells and battery devices with good cycle performance are used to store or provide electrical energy for energy storage devices, which can extend the service life of energy storage devices.

[0040] Electrical devices include multiple solid-state battery cells or multiple battery devices, which are used to store or provide electrical energy.

[0041] The aforementioned solid-state battery cells and battery devices with good cycle performance can be used as power sources for electrical devices or as energy storage units for electrical devices, thereby increasing the capacity of electrical devices and extending their service life. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 is a schematic diagram of cyanidation treatment of carbon materials according to an embodiment of this application;

[0044] Figure 2 is a schematic diagram of the internal structure of the negative electrode sheet in an embodiment of this application;

[0045] Figure 3 is a schematic diagram of a solid-state battery cell according to an embodiment of this application;

[0046] Figure 4 is an exploded view of a solid-state battery cell according to an embodiment of this application, as shown in Figure 3. Detailed Implementation

[0047] The embodiments of this application are hereby disclosed in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy 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.

[0048] 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 understood that ranges of 60–110 and 80–120 are also expected. 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 "a–b" 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.

[0049] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0050] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0051] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0052] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0053] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0054] Commercial lithium-ion batteries typically use electrolytes containing flammable carbonate and ether solvents. These electrolytes can easily cause lithium-ion batteries to spontaneously combust or explode under conditions such as impact or puncture, posing a significant safety hazard. In contrast, all-solid-state batteries using solid-state electrolytes can effectively solve these safety issues during battery use.

[0055] Carbon materials possess advantages such as low cost, high specific capacity, high conductivity, and good stability, making them widely used as anode materials in all-solid-state batteries. However, in practice, it has been found that using carbon materials as anode materials often results in low initial efficiency and poor cycle performance. The reasons for this may include: conventional carbon materials inevitably retain oxygen-containing functional groups on their surface during processing and use, such as hydroxyl, carboxyl, and ester groups; when the proportion of these oxygen-containing functional groups is too high, a severe lithium-electrolysis phenomenon occurs, where some active lithium becomes inactive lithium and cannot continue to participate in electrochemical reactions, causing a decline in the battery's initial efficiency and cycle performance. Related technologies have not recognized or solved this problem.

[0056] To address the aforementioned issues, surface modification or functional group substitution could potentially reduce oxygen-containing functional groups. However, current anodes typically use non-ionic / electronic active materials such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) as binders, which hinder ion / electron transport within the anode. This hindering effect is particularly pronounced in all-solid-state batteries due to the non-flowability of the solid electrolyte, ultimately leading to reduced initial efficiency and cycle performance. Therefore, even reducing oxygen-containing functional groups on the surface of carbon materials is unlikely to effectively improve the battery's initial efficiency and cycle performance.

[0057] Based on this, embodiments of this application provide a solid-state battery cell, which includes a negative electrode sheet. The negative electrode sheet uses a special polymer as a binder, and the binder is connected to a carbon material. This can simultaneously reduce the excessive oxygen-containing functional groups on the surface of the carbon material, solve the problem of the binder hindering ion / electron transport, and enable the solid-state battery to exhibit high initial efficiency and good cycle performance.

[0058] [Negative electrode plate]

[0059] The negative electrode sheet of this application embodiment includes a negative current collector and a negative active layer disposed on at least one side of the negative current collector. The negative active layer includes a carbon material and a binder. The binder includes a structural unit as shown in Formula I or its tautomer. The carbon material is connected to the binder.

[0060] Formula I, n=10000~100000.

[0061] For example, n can be any point value from 10000, 20000, 40000, 60000, 80000, 100000, or a range between any two.

[0062] The tautomers of the structural unit shown in Equation I refer to functional group isomers generated by double bond or proton migration. For example, the possible tautomers of the structural unit shown in Equation I are shown in Equation I-1 and Equation I-2.

[0063] The connection between carbon materials and binders refers to a chemical bond (usually a covalent bond) between the carbon materials and the binder. More specifically, the polymer segments of the binder are chemically bonded to the surface of the carbon materials. The connection between carbon materials and binders may form structures as shown in Formula I-3, where at least one of A, B, C, and D includes carbon materials. The carbon materials are covalently bonded to any one or more carbon atoms in the structural unit or its tautomer of Formula I. Optionally, the carbon materials are covalently bonded to the nitrogen-containing six-membered rings included in the structural unit or its tautomer of Formula I. One or more carbon atoms in the carbon material are covalently bonded together. Alternatively, the carbon material is covalently bonded to the carbon atoms adjacent to nitrogen in the nitrogen-containing six-membered ring contained in the structural unit of Formula I or its tautomer.

[0064] Infrared spectroscopy and nuclear magnetic resonance (NMR) analysis can be performed on the negative electrode active layer to determine whether it contains carbon materials and a binder comprising structural units as shown in Formula I or their tautomers. Since the connection between the carbon materials and the binder causes a shift in the characteristic peaks of the carbon materials, after identifying that the sample contains carbon materials, the spectrum of the sample can be compared with that of a standard carbon material. Observing a shift in the characteristic peaks of the sample relative to the standard confirms the connection between the carbon materials and the binder. Alternatively, after determining that the sample contains carbon materials and a binder (and after testing the mass content of each component using thermogravimetric analysis), a control group can be prepared based on the obtained composition: a negative electrode slurry containing carbon materials and a binder is coated onto at least one side of the negative electrode current collector to form a negative electrode active layer, with the coating amount, negative electrode active layer thickness, and other technical parameters controlled to be the same as those of the sample. It is generally believed that the binder and carbon materials in the negative electrode active layer of the control group prepared in this way do not have the connection relationship described in this application. If a test sample has the negative electrode structure of this application, the cohesive force of the test sample is stronger than that of the control group because the carbon material in its negative electrode active layer is connected to the binder. Therefore, the cohesive force of the test sample and the control group can be compared. If the cohesive force of the test sample is significantly greater than that of the control group, it can be considered that the carbon material in the test sample is connected to the binder.

[0065] The negative electrode sheet of this application embodiment can effectively improve the first-efficiency and cycle performance of solid-state batteries using carbon materials as negative electrode materials. The mechanism may include:

[0066] On the one hand, the carbon material is connected to the binder, and the segments of the binder connected to the carbon material can replace the oxygen-containing functional groups on the surface of the carbon material, reducing the number of oxygen-containing functional groups and alleviating the lithium swallowing phenomenon caused by oxygen-containing functional groups, thus reducing the loss of active lithium. On the other hand, the binder includes structural units as shown in Formula I or their tautomers. The conjugated structure in this structural unit provides a fast ion / electron transport channel, thereby forming a high ion / electron transport network, which can improve the ion / electron transport performance of the negative electrode.

[0067] Therefore, the embodiments of this application can effectively improve the first efficiency and cycle performance of solid-state batteries by simultaneously improving the lithium swallowing problem of oxygen-containing functional groups on the surface of carbon materials and the obstacle problem of ion / electron transport by binders.

[0068] In some embodiments, the binder includes cyclized PAN (cyclized polyacrylonitrile) polymers.

[0069] Cyclic PAN polymers are polymers containing a cyclized PAN structure. Cyclic PAN is a product generated by the cyclization reaction of PAN polymers (PAN polymers are polymers containing a PAN structure, which can be PAN or PAN with added substituents or other molecular segments, containing the structural unit shown in Formula II). Depending on the cyclization conditions, cyclized PAN may have different structural formulas. It is generally believed that cyclized PAN contains the structural unit shown in Formula I or its tautomers, and may contain the structural unit shown in Formula III. Cyclic PAN polymers are polymers containing a cyclized PAN structure, and therefore also contain the structural unit shown in Formula II. Cyclic PAN polymers can be cyclized PAN, or they can be cyclized PAN with added substituents or other molecular segments.

[0070] Infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) techniques can be used to test the negative electrode active layer to determine its composition and whether it contains cyclic PAN polymers. For example, the infrared spectra of cyclic PAN polymers typically show a peak at 1620 cm⁻¹. -1 Nearby (C=N stretching vibration peak), 2243cm -1 An absorption peak appears near the C≡N stretching vibration peak, possibly at 1580 cm⁻¹. -1 There is an absorption peak nearby (C=C stretching vibration peak, some cyclized PAN structures may contain C=C bonds); 13In C NMR spectra, resonance peaks typically appear around 155 ppm (C=N) and 108 ppm (uncyclized C≡N), and may appear around 116 ppm (C=C) and 150 ppm (C=C). Understandably, these absorption or resonance peak positions are merely examples. Due to the diversity of cyclized PAN polymer structures and their varying chemical environments, the positions of absorption or resonance peaks in their infrared and NMR spectra may differ. The peak positions of cyclized PAN polymers can be determined based on the specific circumstances and in conjunction with general chemical analysis methods.

[0071] Cyclic PAN polymers have high ion / electron transport capabilities, which are beneficial to improving the ion / electron transport performance of the negative electrode. In addition, cyclic PAN polymers have high viscosity, which can improve the cohesion of the negative electrode sheet. Under the combined effect, they can effectively improve the first efficiency and cycle performance of solid-state batteries.

[0072] In some embodiments, the binder content in the negative electrode active layer is 3% to 8% by mass, optionally 3% to 5%, for example, any value or range between 3%, 4%, 5%, 6%, 7%, and 8%. Since the thermal decomposition temperatures of the components in the negative electrode active layer differ, the mass content of the binder in the negative electrode active layer can be determined using thermogravimetric analysis. At this content, the binder can effectively bind the carbon material tightly, improving the cohesion of the negative electrode sheet and enhancing its ion / electron transport performance; simultaneously, the binder can be uniformly dispersed in the negative electrode active layer at this content; and it does not excessively occupy the proportion of carbon material used to provide capacity, which is beneficial for improving the energy density of the negative electrode sheet.

[0073] In some embodiments, the thickness of the negative electrode active layer is 10 μm to 30 μm, for example, any one of 10 μm, 15 μm, 20 μm, 25 μm, and 30 μm, or a range between any two. The thickness of the negative electrode active layer in the embodiments of this application can be designed as needed and is not limited to the thickness range listed above. For negative electrode active layers of different thicknesses, the solutions adopted in the embodiments of this application can simultaneously solve the lithium swallowing problem of oxygen-containing functional groups on the surface of carbon materials and the problem of binder hindering ion / electron transport, thereby improving the first-efficiency and cycle performance of solid-state batteries.

[0074] In some embodiments, the C / O mass ratio (mass ratio of carbon to oxygen) of the carbon material is above 1000, optionally between 1000 and 2000, for example, any value from 1000, 1200, 1400, 1600, 1800, to 2000, or a range between any two. The C / O mass ratio can be obtained by inductively coupled plasma (ICP) or X-ray photoelectron spectroscopy (XPS). A C / O mass ratio above 1000 in the carbon material indicates a lower content of oxygen-containing functional groups, which can alleviate the lithium swallowing problem caused by oxygen-containing functional groups.

[0075] In some embodiments, the carbon material includes one or more of silicon-carbon (a compound or composite material containing silicon and carbon), graphite (artificial graphite, natural graphite), mesophase carbon microspheres, soft carbon, and hard carbon. These carbon materials typically retain oxygen-containing functional groups on their surface during processing and use. The solution described in this application can effectively reduce the number of oxygen-containing functional groups on the surface of these carbon materials, improving the lithium absorption problem caused by these functional groups, and enabling solid-state batteries using these carbon materials as anode materials to have high initial efficiency and good cycle performance.

[0076] Understandably, carbon materials are used as the negative electrode active material. Meanwhile, in the negative electrode active layer of this application embodiment, the negative electrode active material may also include other materials, such as silicon-based materials, tin-based materials, etc. Silicon-based materials may include one or more of elemental silicon, silicon-oxygen materials (compounds or composites containing silicon and oxygen), silicon-nitrogen materials (compounds or composites containing silicon and nitrogen), and silicon alloys. Tin-based materials may include one or more of elemental tin, tin-oxygen materials, and tin alloys. Generally, a negative electrode active material with high stability that does not react with other substances (e.g., binder precursors) during the preparation of the negative electrode sheet can be selected, thereby reducing the difficulty in forming the negative electrode sheet and successfully obtaining the desired negative electrode sheet. Typically, the negative electrode active layer of this application embodiment does not contain Li4Ti5O. 12 These include unstable materials with low melting points, such as titanium-based materials and Li-In, which can react with binder precursors.

[0077] In some embodiments, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector. The negative electrode current collector includes one or more of metal foil and composite current collector. For example, one or more of copper foil, stainless steel foil, nickel foil, and titanium foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, stainless steel, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate [such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.].

[0078] The negative electrode sheet provided in this embodiment is prepared by the following method:

[0079] Carbon materials are cyanided to obtain cyano-carbon materials;

[0080] A negative electrode active layer comprising carbon cyanide material and binder precursor is prepared on at least one side of the negative electrode current collector, wherein the binder precursor comprises the structural unit shown in Formula II.

[0081] This causes a crosslinking reaction between the cyanocarbon material and the binder precursor.

[0082] Formula II, n = 10000 ~ 100000.

[0083] Cyanidation of carbon materials refers to the modification of the carbon material surface with cyano groups, giving the carbon material a cyano group appearance. Since carbon materials typically contain oxygen-containing functional groups (usually, before cyanidation, the C / O mass ratio of common carbon materials is between 50 and 500), during the cyanidation process, the cyano groups usually replace (partially or completely replace) these oxygen-containing functional groups, as shown in Figure 1 (Figure 1 uses hydroxyl groups as an example of oxygen-containing functional groups). Whether a material contains carbon and whether it contains cyano groups can be determined by Raman spectroscopy, infrared spectroscopy, or XPS (exposure propellant spectroscopy), thus identifying whether the material is a cyanided carbon material.

[0084] A crosslinking reaction is initiated between cyanocarbon material and binder precursor, including a crosslinking reaction between some (or all) of the cyanocarbon material and some (or all) of the binder precursor. Since the cyanocarbon material contains cyano groups, and the structural unit of Formula II in the binder precursor contains repeating cyano groups, during the crosslinking reaction, the cyano groups in the cyanocarbon material can crosslink with the binder precursor, and intramolecular cyclization also occurs (therefore, the crosslinking reaction between the cyanocarbon material and the binder precursor can also be described as a cyclization reaction between the cyanocarbon material and the binder precursor), forming a crosslinked product (binder) with a cyclized structure containing a structural unit of Formula I or its tautomers. Furthermore, at least one nitrogen-containing six-membered ring C=N or CN structure in the structural unit of Formula I or its tautomers originates from the cyanocarbon material; therefore, after the crosslinking reaction, the carbon material is linked to the binder. More specifically, the carbon material and the nitrogen-containing six-membered ring contained in the structural unit of Formula I or its tautomers... The carbon atoms adjacent to nitrogen are covalently bonded. Understandably, due to the complexity of the cross-linking process, the carbon material may also be covalently bonded to other carbon atoms in the nitrogen-containing six-membered ring contained in the structural unit shown in Formula I or its tautomers.

[0085] The products after the cross-linking reaction can be analyzed by infrared spectroscopy and nuclear magnetic resonance (NMR). If the product contains the structural unit shown in Formula I or its tautomer, the cross-linking reaction can be considered to have occurred. For example, the infrared spectrum of the structural unit shown in Formula I is typically at 1620 cm⁻¹. -1 Nearby (C=N stretching vibration peak), 2940cm -1 An absorption peak appears nearby (CH2 stretching vibration). 13 A resonance peak typically appears at 155 ppm (C=N) in a C NMR spectrum.

[0086] The negative electrode sheet prepared in this application embodiment can effectively improve the first-efficiency and cycle performance of solid-state batteries using carbon materials as negative electrode active materials. The mechanism may include:

[0087] By cyaniding carbon materials and then crosslinking the resulting cyano-treated carbon materials with a binder precursor containing the structural unit shown in Formula II, the cyano groups can replace the oxygen-containing functional groups on the surface of the carbon materials, reducing the number of oxygen-containing functional groups and mitigating lithium absorption caused by these groups, thus reducing the loss of active lithium. Furthermore, the cyano groups on the surface of the cyano-treated carbon materials can participate in the crosslinking reaction, forming a crosslinked product with the structural unit shown in Formula I or its tautomers together with the binder precursor. This crosslinked product with the structural unit has high viscosity and can be used as a binder. Since part of the binder's structure originates from the cyano groups on the surface of the cyano-treated carbon materials, the binder can connect to the carbon materials and utilize the conjugated structure in its Formula I structural unit or its tautomers to provide a fast ion / electron transport channel, thereby forming a high ion / electron transport network that can improve the ion / electron transport performance of the negative electrode.

[0088] Therefore, the preparation method of this application embodiment can effectively improve the first efficiency and cycle performance of solid-state batteries by simultaneously improving the lithium swallowing problem of oxygen-containing functional groups on the surface of carbon materials and the obstacle problem of ion / electron transport by binders.

[0089] In some embodiments, the cyano group content in the cyanocarbon material is 2.5% to 6% by mass, optionally 3.5% to 4%, for example, any one of 2.5%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.5%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, 5%, 5.5%, 6%, or a range between any two. The mass content of cyano groups in the cyanocarbon material can be determined by thermogravimetric analysis. By modifying the carbon material with a certain amount of cyano groups, the number of oxygen-containing functional groups on the surface of the carbon material can be reduced, alleviating the lithium absorption phenomenon caused by oxygen-containing functional groups and reducing the loss of active lithium.

[0090] In some embodiments, the method for cyaniding carbon materials includes reacting the carbon material with a cyaniding reagent. The cyanidation reaction can be carried out in the presence of an alkaline environment and a catalyst. The cyano groups in the cyaniding reagent can replace oxygen-containing functional groups on the surface of the carbon material, reducing lithium absorption by these groups and thus improving the initial efficiency and cycle performance of solid-state batteries.

[0091] The cyaniding reagent is a compound containing a cyano group, including one or more of trimethylcyanosilane (TMSCN), acetone cyanohydrin, sodium cyanide, potassium cyanide, hydrogen cyanide, and acrylonitrile.

[0092] The base includes one or more of Li₂CO₃, Na₂CO₃, K₂CO₃, NaOH, and KOH. Alkaline conditions can promote the hydrolysis of cyanide reagents, thereby achieving the substitution of oxygen-containing functional groups on the surface of carbon materials by cyano groups.

[0093] Catalysts include one or more of iodine, iron-containing compounds (such as FeCl3, Fe2(SO4)3, etc.), and copper-containing compounds (such as CuSO4, Cu(NO3)2, etc.). The reaction rate of cyanidation can be increased under the action of a catalyst.

[0094] In some embodiments, the mass ratio of carbon material to cyaniding reagent is 100:(10-20), optionally 100:(15-17), for example, any one of 100:10, 100:12, 100:14, 100:15, 100:16, 100:17, 100:18, 100:20, or any range between the two. By combining carbon material and cyaniding reagent in an appropriate ratio, a certain amount of cyano groups can be modified onto the carbon material, reducing the number of oxygen-containing functional groups on the carbon material surface, mitigating lithium absorption caused by oxygen-containing functional groups, and reducing the loss of active lithium. Typically, the mass content of cyano groups in the cyano-modified carbon material can be calculated based on the mass ratio of carbon material to cyaniding reagent. Taking the cyaniding reagent TMSCN as an example, the mass content of cyano groups in TMSCN is about 26%. When the mass ratio of carbon material to cyaniding reagent is 100:16, the mass content of cyano groups in the cyanidated carbon material obtained is about 4% [(16×26%) / (16×26%+100)=4%], or less than 4% (when the cyaniding reagent is in excess).

[0095] The mass ratio of carbon material to alkali is 100:(0.1 to 1), optionally 100:(0.5 to 0.7), for example, any one of the following values ​​or any range between 100:0.1, 100:0.2, 100:0.4, 100:0.5, 100:0.6, 100:0.7, 100:0.8, and 100:1.

[0096] The mass ratio of carbon material to catalyst is 100:(0.5 to 5), optionally 100:(1 to 3), for example, any one of the following values ​​or any range between 100:0.5, 100:1, 100:1.5, 100:2, 100:2.5, 100:3, 100:3.5, 100:4, 100:4.5, 100:5.

[0097] In some embodiments, the cyanidation reaction is typically carried out in a solvent system. Solvents used in the cyanidation process include one or more of dichloromethane, acetonitrile, acetone, N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO). These solvents can effectively dissolve or disperse cyaniding agents, bases, catalysts, and other substances.

[0098] In the reaction system, the concentration of carbon material can be set between 0.5 g / mL and 2 g / mL, optionally between 0.8 g / mL and 1.2 g / mL, for example, any one of the values ​​of 0.5 g / mL, 0.6 g / mL, 0.8 g / mL, 1 g / mL, 1.2 g / mL, 1.4 g / mL, 1.6 g / mL, 1.8 g / mL, and 2 g / mL, or any range between two of them.

[0099] The concentration of the cyanide reagent can be set between 0.1 g / mL and 0.2 g / mL, optionally between 0.15 g / mL and 0.17 g / mL, for example, any one of 0.1 g / mL, 0.12 g / mL, 0.14 g / mL, 0.15 g / mL, 0.16 g / mL, 0.17 g / mL, 0.18 g / mL, 0.2 g / mL, or any range between two of these values.

[0100] The concentration of the alkali can be set between 0.001 g / mL and 0.01 g / mL, optionally between 0.005 g / mL and 0.007 g / mL, for example, any one of the following values ​​or any range between 0.001 g / mL, 0.002 g / mL, 0.004 g / mL, 0.005 g / mL, 0.006 g / mL, 0.007 g / mL, 0.008 g / mL, and 0.01 g / mL.

[0101] The concentration of the catalyst can be set between 0.005 g / mL and 0.05 g / mL, optionally between 0.01 g / mL and 0.03 g / mL, for example, any one of 0.005 g / mL, 0.01 g / mL, 0.015 g / mL, 0.02 g / mL, 0.025 g / mL, 0.03 g / mL, 0.035 g / mL, 0.04 g / mL, 0.045 g / mL, 0.05 g / mL, or any range between two of these values.

[0102] In some embodiments, the cyanotyping temperature is 20°C to 50°C, optionally 25°C to 40°C, for example, any one of 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, and 50°C, or a range between any two. The cyanotyping time is 5 hours to 20 hours, optionally 8 hours to 12 hours, for example, any one of 5 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, and 20 hours, or a range between any two. Treating at this temperature for a certain time allows for successful modification of the carbon material surface with cyano groups.

[0103] In some embodiments, the cyanidation process is carried out in a protective atmosphere, such as a nitrogen atmosphere, a helium atmosphere, or a vacuum atmosphere. Under a protective atmosphere, unwanted side reactions can be reduced, successfully modifying carbon materials with cyano groups.

[0104] In some embodiments, the method for cyaniding carbon materials includes: dispersing the carbon material in a solvent, adding a cyaniding reagent, an alkali, and a catalyst, and stirring at 20°C to 50°C for 5 to 20 hours; subsequently performing solid-liquid separation, washing, and drying to obtain cyanided carbon materials.

[0105] In some embodiments, the binder precursor includes a polyacrylonitrile (PAN) polymer. PAN polymers are polymers containing a PAN structure, which can be PAN itself or have substituents or other molecular chain segments added to the PAN structure, containing the structural unit shown in Formula II. In the crosslinking reaction, PAN polymers can generate cyclized PAN polymers, and the molecular chains of the cyclized PAN polymers can be linked to carbon material particles, as shown in Figure 2, thereby tightly binding the carbon material particles together and improving the cohesion of the negative electrode. Furthermore, cyclized PAN polymers have high ion / electron transport capabilities, which is beneficial for improving the ion / electron transport performance of the negative electrode, thereby improving the first-efficiency and cycle performance of the solid-state battery.

[0106] In some embodiments, the weight-average molecular weight of the binder precursor is 100,000 to 500,000, optionally 200,000 to 400,000, for example, any one of 100,000, 150,000, 200,000, 250,000, 300,000, 350,000, 400,000, 450,000, or 500,000, or a range between any two. The weight-average molecular weight of the binder precursor in the raw material can be determined using methods such as light scattering or gel permeation chromatography. Binder precursors at this molecular weight can undergo cross-linking reactions at a relatively fast reaction rate, generating stable, highly viscous binders.

[0107] In some embodiments, the mass content of the binder precursor in the negative electrode active layer is 4% to 9%, optionally 4% to 6%, for example, any one of 4%, 5%, 6%, 7%, 8%, or 9%, or a range between any two. The mass content of the binder precursor in the negative electrode active layer can be calculated based on the amount of raw materials used; or the mass content of the binder precursor in the negative electrode active layer can be determined by thermogravimetric analysis based on different pyrolysis temperatures. At this content, a certain amount of binder comprising the structural units shown in Formula I or their tautomers, with high ion / electron transport performance, can be generated using the binder precursor, reducing the binder's obstruction to ion / electron transport, giving the negative electrode sheet suitable conductivity, and ensuring good uniformity of both the binder precursor and the generated binder in the negative electrode active layer, which is beneficial for improving the first-efficiency and cycle performance of the solid-state battery.

[0108] Understandably, because the binder precursor may undergo a cracking reaction during the crosslinking process, generating small molecule gases or causing some structures to detach from the molecular chain, the mass of the resulting binder is usually lower than the mass of the binder precursor added during the preparation process. Typically, when the mass content of the binder precursor in the negative electrode active layer is 4%–9%, ​​the mass content of the resulting binder in the negative electrode active layer is estimated to be 3%–8%; when the mass content of the binder precursor in the negative electrode active layer is 4%–6%, the mass content of the resulting binder in the negative electrode active layer is estimated to be 3%–5%.

[0109] In some embodiments, the method for causing the cyanocarbon material to undergo a crosslinking reaction with the binder precursor includes: performing heat treatment under a protective atmosphere at a temperature of 200°C to 350°C, optionally 280°C to 320°C, such as any one of 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, and 350°C, or a range between any two. The heat treatment time is 4 hours to 9 hours, optionally 4 hours to 6 hours, such as any one of 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, and 9 hours, or a range between any two. The protective atmosphere includes one or more of nitrogen, helium, argon, and vacuum atmospheres.

[0110] Understandably, the heat treatment time can be adaptively adjusted according to the temperature. Generally, a higher heat treatment temperature allows for a shorter time, while a lower temperature allows for a longer time. Heat treatment under a protective atmosphere allows the binder precursor, including the structural unit shown in Formula II, to undergo a crosslinking reaction with the cyano-carbon material. During the crosslinking process, cyclization occurs, generating a binder including the structural unit shown in Formula I or its tautomers. The binder connects to the carbon material, which is beneficial for constructing a high ion / electron transport network and reducing the binder's obstruction of ion / electron transport. Furthermore, by controlling the heat treatment temperature and time, the generated binder can have a suitable degree of cyclization, which improves the cohesion of the negative electrode and gives it suitable conductivity. When applied to solid-state batteries, the negative electrode exhibits good compatibility with most solid electrolyte membranes, preventing decomposition of the solid electrolyte membrane due to excessive conductivity. Moreover, the binder generated at this concentration can tightly bond the carbon material, improving the cohesion of the negative electrode and forming a structurally stable negative electrode, thus improving the first-efficiency and cycle performance of the solid-state battery.

[0111] In some embodiments, the Dv50 of the carbon material is 10 nm to 20 μm, optionally 1 μm to 20 μm, for example, any point value or range between any two of 10 nm, 50 nm, 100 nm, 200 nm, 400 nm, 600 nm, 800 nm, 1 μm, 2 μm, 4 μm, 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, and 20 μm. The particle size distribution of a material is usually expressed as the percentage of particles within different particle size ranges. There are various benchmarks for determining particle size distribution, such as number distribution, length distribution, area distribution, volume distribution, and weight distribution. Dv50 is a specific particle size distribution based on volume distribution, also known as the median particle size, which refers to the particle size at which the cumulative volume distribution is 50%, indicating that 50% of the particles have a diameter greater than this value and 50% of the particles have a diameter less than this value. The Dv50 of the particles can be obtained by referring to GB / T 19077-2016 / ISO 13320:2009 "Particle size distribution - Laser diffraction method". The embodiments of this application can use carbon materials of various particle sizes as raw materials to prepare negative electrode sheets, and the method has good universality.

[0112] In some embodiments, the negative electrode active layer in the above-mentioned method for preparing the negative electrode sheet typically does not contain conductive agents, such as vapor-grown carbon fiber (VGCF), carbon dots, carbon nanotubes, graphene, carbon nanofibers, etc. These conductive agents can confine the cyclization of the binder precursor, causing a decrease in the cohesion of the negative electrode active layer.

[0113] [Positive electrode plate]

[0114] The positive electrode sheet of this application embodiment includes a positive current collector and a positive active layer disposed on at least one side of the positive current collector. The positive active layer may contain a positive active material, a solid electrolyte, a conductive agent, a binder, and may also contain other additives that can improve the performance of the positive electrode sheet.

[0115] In some embodiments, the positive electrode active material includes one or more of lithium phosphates having an olivine structure and their modified compounds, lithium transition metal oxides and their modified compounds. Examples of lithium phosphates having an olivine structure include lithium iron phosphate (such as LiFePO4, i.e., LFP), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Examples of lithium transition metal oxides may include lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides [such as LiNi]. 1 / 3 Co1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2(NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 O2), lithium niobium oxides (such as lithium niobate), lithium titanium oxides (such as Li4Ti5O) 12 One or more of the following: ) and their modified compounds. These positive electrode active materials may be used alone or in combination of two or more. The mass content of the positive electrode active material in the positive electrode active layer may include 60% to 80%, optionally 70% to 80%, for example, any one of 60%, 65%, 70%, 75%, 80% or any range between two.

[0116] In some embodiments, the solid electrolyte includes one or more of sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, and polymer solid electrolytes, optionally including sulfide solid electrolytes. Sulfide solid electrolytes include one or more of Li6PS5Cl, Li2S-GeS2, Li2S-P2S5, Li2S-SiS2, and Li2S-MeS2-P2S5 (Me = Si, Ge, Sn, Al, etc.). Halide solid electrolytes include one or more of Li3YCl6, Li3InCl6, Li3ErCl6, Li3ScCl6, Li3HoCl6, Li2MnCl4, Li2MnCl5, and Li6FeCl8. Oxide solid electrolytes include lithium oxide garnet (Li7La3Zr2O). 12The solid electrolyte comprises one or more of the following: LLZO, tin oxide (SnO2), and bismuth oxide (Bi2O3). Polymer solid electrolytes include one or more of polyethylene oxide electrolytes, polycarbonate electrolytes, and polysiloxane electrolytes. The mass content of the solid electrolyte in the positive electrode active layer can include 20% to 30%, optionally 25% to 27%, for example, any one of 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, and 30%, or a range between any two.

[0117] In some embodiments, the conductive agent may include one or more of vapor-grown carbon fiber (VGCF), superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The mass content of the conductive agent in the positive electrode active layer may be 1% to 5%, for example, it may be any one of 1%, 2%, 3%, 4%, and 5%, or any range between two values.

[0118] In some embodiments, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, polyamide (PA), polyacrylonitrile (PAN), polyacrylate, polyethylene ether, polymethyl methacrylate (PMMA), polyhexafluoropropylene, and styrene-butadiene rubber (SBR). The mass content of the binder in the positive electrode active layer may be 0.5% to 5%, for example, any one of 0.5%, 1%, 2%, 3%, 4%, and 5%, or a range between any two.

[0119] In some embodiments, the positive current collector includes two surfaces opposite each other in its own thickness direction, and the positive active layer can be disposed on either or both of the opposite surfaces of the positive current collector. The positive current collector includes one or more of metal foil and composite current collector. For example, aluminum foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate [such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.].

[0120] The positive electrode sheet can be prepared by the following method:

[0121] The components used to prepare the positive electrode sheet, such as the positive electrode active material, solid electrolyte, conductive agent, binder, and any other components, are mixed, formed into a film, and pressed to obtain the positive electrode film. The positive electrode film is then combined with a positive electrode current collector to obtain the positive electrode sheet.

[0122] Alternatively, the components used to prepare the positive electrode sheet, such as positive active material, solid electrolyte, conductive agent, binder and any other components, are mixed to form a positive electrode slurry. The positive electrode slurry is coated on the positive current collector and then dried and cold-pressed to obtain the positive electrode sheet.

[0123] [Solid electrolyte membrane]

[0124] The battery cell in this application embodiment includes a solid electrolyte, which is typically used in the form of a membrane, i.e., a solid electrolyte membrane. The solid electrolyte membrane is disposed between the positive and negative electrode plates and is in contact with both plates. During battery charging and discharging, active ions repeatedly insert and extract between the positive and negative electrode plates, and the solid electrolyte membrane acts as a conductor of ions between them.

[0125] The solid electrolyte membrane in this application includes one or more of sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, and polymer solid electrolytes, and optionally includes sulfide solid electrolytes. Sulfide solid electrolytes include one or more of Li6PS5Cl, Li2S-GeS2, Li2S-P2S5, Li2S-SiS2, and Li2S-MeS2-P2S5 (Me = Si, Ge, Sn, Al, etc.). Halide solid electrolytes include one or more of Li3YCl6, Li3InCl6, Li3ErCl6, Li3ScCl6, Li3HoCl6, Li2MnCl4, Li2MnCl5, and Li6FeCl8. Oxide solid electrolytes include lithium oxide garnet (Li7La3Zr2O). 12 This includes one or more of the following: LLZO, tin oxide (SnO2), and bismuth oxide (Bi2O3). Polymer solid electrolytes include one or more of the following: polyethylene oxide electrolytes, polycarbonate electrolytes, and polysiloxane electrolytes.

[0126] To improve the compatibility between the solid electrolyte membrane and the electrode, the solid electrolyte membrane can have the same or similar properties as the solid electrolyte in the positive electrode active layer.

[0127] Solid electrolyte membranes can be prepared by the following method:

[0128] A solid electrolyte is mixed with a binder to form a membrane of suitable thickness. In the solid electrolyte membrane, the mass of the binder can be 0.5% to 5%, for example, any one of 0.5%, 1%, 2%, 3%, 4%, or 5%, or a range between any two. The binder in the solid electrolyte membrane includes one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, polyamide (PA), polyacrylonitrile (PAN), polyacrylate, polyethylene ether, polymethyl methacrylate (PMMA), polyhexafluoropropylene, and styrene-butadiene rubber (SBR).

[0129] [Outer Packaging]

[0130] Solid-state battery cells may include an outer packaging that can be used to encapsulate the positive electrode, negative electrode, and solid electrolyte membrane.

[0131] The outer packaging can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell; or it can be a soft package, such as a pouch. The material of the soft package can be plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0132] The outer packaging can be cylindrical, square, or any other shape. For example, Figure 3 shows a solid-state battery cell with a square outer packaging structure as an example.

[0133] Referring to Figure 4, the outer packaging may include a housing 01 and a cover plate 02. The housing 01 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 01 has an opening communicating with the receiving cavity, and the cover plate 02 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a solid electrolyte membrane may be stacked to form an electrode assembly 03. One or more electrode assemblies 03 are encapsulated within the receiving cavity.

[0134] [Solid-state battery cell]

[0135] In this embodiment, the solid-state battery cell can be a rechargeable battery, which refers to a battery cell that can be recharged after discharge to reactivate the active materials and continue to be used. Optionally, the solid-state battery cell in this embodiment is an all-solid-state battery, and more preferably an all-solid-state lithium-ion battery. It is understood that the battery cell in this embodiment may also include a semi-solid-state battery, etc., as needed.

[0136] The solid-state battery cell of this application embodiment includes the above-mentioned negative electrode sheet. The carbon material surface of the negative electrode sheet has a small number of oxygen-containing functional groups, which can reduce the lithium swallowing phenomenon caused by oxygen-containing functional groups. In addition, a highly conductive / ion transport network is constructed in the negative electrode sheet, which has excellent ion / electron transport performance, so that the solid-state battery cell exhibits high first efficiency and cycle performance.

[0137] Solid-state battery cells can be assembled as follows: stack the positive electrode, solid electrolyte membrane, and negative electrode in that order, and apply pressure to make the positive electrode and negative electrode in close contact with the solid electrolyte membrane.

[0138] [Battery Device]

[0139] This application provides a battery apparatus including multiple solid-state battery cells. Specifically, the battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple solid-state battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0140] The solid-state battery cell of this application embodiment has good cycle performance. Therefore, applying the battery cell to a battery device can help improve the cycle performance of the battery device and extend the service life of the battery device.

[0141] In some implementations, a battery cell assembly is typically formed by arranging multiple battery cells.

[0142] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0143] In some implementations, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0144] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0145] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0146] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0147] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0148] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0149] The technical solutions described in the embodiments of this application are applicable to various battery devices that use solid-state battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships and spacecraft, etc. For example, spacecraft include airplanes, rockets, space shuttles and spacecraft.

[0150] [Energy Storage Device]

[0151] This application provides an energy storage device, including multiple solid-state battery cells or multiple battery devices, wherein the solid-state battery cells or battery devices are used to store or provide electrical energy.

[0152] The aforementioned solid-state battery cells and battery devices with good cycle performance are used to store or provide electrical energy for energy storage devices, which can extend the service life of energy storage devices.

[0153] In some implementations, the energy storage device includes one or more battery clusters to increase the voltage and capacity of the energy storage device. A battery cluster may include multiple battery units connected in series via a busbar to increase the voltage of the energy storage device. When the energy storage device includes multiple battery clusters, the battery clusters are connected in parallel to increase the capacity of the energy storage device.

[0154] Energy storage devices can be used in energy storage power stations, wind power generation systems, solar power generation systems, mobile power systems, or temporary power supply systems. Energy storage devices can store electrical energy as needed and output it when appropriate. For example, an energy storage device can store electrical energy during off-peak hours and provide power to relevant users or electrical equipment during peak hours. The energy storage system provided in this application embodiment can be any power system that requires energy storage devices.

[0155] In some implementations, the energy storage device is an energy storage container or an energy storage cabinet.

[0156] In some implementations, the energy storage device may include a cabinet and one or more battery clusters housed within the cabinet.

[0157] In some implementations, the energy storage device may include modules such as a thermal management module, a main control module, a central control module, a power distribution module, and a fire protection module.

[0158] As an example, the thermal management module may include a liquid cooling unit that supplies coolant to each battery device via piping to regulate the temperature of the individual battery cells.

[0159] As an example, the main control module can serve as the battery management unit for the battery cluster, used to monitor and manage the battery cluster. The main control module can monitor information such as the current, voltage, power, or temperature of the battery cluster. For instance, it can control the charging and discharging current and voltage of the battery cluster. The main control module includes a slave battery management unit (SBMU), a fusion switch, and other modules.

[0160] As an example, the central control module can serve as the battery management unit for an energy storage device, used to monitor and manage the device. The central control module can monitor information such as the energy storage device's current, voltage, power, state of charge, or temperature. For instance, it can control the charging and discharging current and voltage of the energy storage device. As an example, the central control module includes modules such as an Insulation Monitoring Module (IMM), a Master Battery Management Unit (MBMU), an Ethernet (ETH) module, and a fiber optic conversion module.

[0161] As an example, the fire protection module includes a control panel, detectors, alarm devices, etc., used to detect, alarm, or extinguish fires in the energy storage system.

[0162] As an example, a power distribution module can be used to distribute power to modules in an energy storage device that require electricity.

[0163] [Electrical appliances]

[0164] This application provides an electrical device, including multiple solid-state battery cells or multiple battery devices, wherein the solid-state battery cells or battery devices are used to store or provide electrical energy.

[0165] The aforementioned solid-state battery cells and battery devices with good cycle performance can be used as power sources for electrical devices or as energy storage units for electrical devices, thereby extending the service life of electrical devices.

[0166] Electrical devices may include, but are not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0167] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0168] Example 1

[0169] 1. Negative electrode plate

[0170] 100 g of vapor-deposited silicon carbon (DV50 approximately 5 μm, C / O mass ratio approximately 300) was dispersed in 100 mL of dichloromethane solvent. 16 g of trimethylsilane cyanide (TMSCN), 0.6 g of Li₂CO₃, and 2.08 g of elemental iodine were added sequentially. The mixture was stirred at 35 °C for 10 h under an inert atmosphere. The mixture was then filtered, washed with a large amount of dichloromethane, and dried under vacuum at 35 °C to obtain silicon carbon cyanide. ICP testing showed that the C / O mass ratio of this silicon carbon cyanide was above 1000.

[0171] Silicon cyanide carbon and PAN were mixed at a mass ratio of 95:5 (PAN content was 5%), and NMP solvent was added. The mixture was stirred thoroughly to obtain a negative electrode slurry. The negative electrode slurry was coated onto copper foil, dried, cold-pressed, and then heated in a vacuum tube furnace at 300℃ for 5 hours to allow PAN to spontaneously cyclize and form cyclized PAN, thus obtaining a negative electrode sheet (the thickness of the negative electrode active layer is about 20 μm).

[0172] 2. Positive electrode plate

[0173] The positive electrode active material NCM811, the sulfide solid electrolyte Li6PS5Cl, and the conductive agent VGCF were uniformly mixed for 10 min at a mass ratio of 70:27:3 to obtain a composite positive electrode powder. PTFE binder, equivalent to 1% of the mass of the first three materials, was added and rolled into a positive electrode film (approximately 20 μm thick).

[0174] 3. Solid electrolyte membrane

[0175] The sulfide solid electrolyte Li6PS5Cl was thoroughly mixed with PTFE binder at 1% of the mass of Li6PS5Cl and rolled into a solid electrolyte membrane.

[0176] 4. Battery assembly

[0177] The negative electrode, solid electrolyte membrane, and positive electrode are stacked in that order from bottom to top. After being subjected to a 600MPa isostatic pressing, the battery cell is obtained, which is then packaged in an aluminum-plastic bag and subjected to battery cell performance testing.

[0178] Example 2

[0179] The difference between this embodiment and Embodiment 1 is that, in the process of preparing silicon carbon cyanide, TMSCN is replaced with an equal mass of NaCN.

[0180] Example 3

[0181] The difference between this embodiment and Embodiment 1 is that, in the preparation process of the negative electrode sheet, the mass ratio of silicon cyanide carbon to PAN is 96:4 (the mass content of PAN is 4%).

[0182] Example 4

[0183] The difference between this embodiment and Embodiment 1 is that, in the preparation process of the negative electrode sheet, the mass ratio of silicon cyanide carbon to PAN is 91:9 (the mass content of PAN is 9%).

[0184] Comparative Example 1

[0185] The difference between this comparative example and Example 1 is that, in the preparation process of the negative electrode sheet, PAN is replaced with an equal mass of PVDF, and no heating is performed.

[0186] Specifically, the negative electrode sheet of this comparative example was prepared according to the following method:

[0187] Silicon cyanide carbon and PVDF were mixed at a mass ratio of 95:5, and NMP solvent was added. The mixture was stirred thoroughly to obtain a negative electrode slurry. The negative electrode slurry was coated onto copper foil, dried, and cold-pressed to obtain a negative electrode sheet.

[0188] Comparative Example 2

[0189] The difference between this comparative example and Example 1 is that the vapor-deposited silicon-carbon was not cyanided during the preparation of the negative electrode sheet.

[0190] Specifically, the negative electrode sheet of this comparative example was prepared according to the following method:

[0191] Vapor-deposited silicon-carbon and PAN were mixed at a mass ratio of 95:5, and NMP solvent was added. The mixture was stirred thoroughly to obtain a negative electrode slurry. The negative electrode slurry was coated onto copper foil, dried, cold-pressed, and then heated in a vacuum tube furnace at 300℃ for 5 hours to allow PAN to spontaneously cyclize and form cyclized PAN, thus obtaining the negative electrode sheet.

[0192] Perform performance testing using the following methods:

[0193] 1. Negative electrode cohesion

[0194] At 25℃, cut the negative electrode sheet into test specimens of 20mm×100mm size for later use; attach one side of double-sided tape to the surface of the steel plate and the other side to the specimen, and press it with a pressure roller to ensure complete adhesion to the specimen; attach cohesion test tape to the other side of the specimen and press it with a pressure roller; bend one end of the cohesion test tape in the opposite direction at a bending angle of 180°; use a universal tensile testing machine to test, fix one end of the steel plate to the lower clamp of the tensile testing machine, fix the bent end of the current collector of the specimen to the upper clamp, adjust the angle of the current collector to ensure that the upper and lower ends are in a vertical position, and then stretch the specimen at a speed of 50mm / min until the entire negative electrode active layer is peeled off from the surface of the current collector, record the displacement and force during the process, take the force when the force is balanced as the adhesive force of the specimen, and divide this force by the adhesion length of the specimen as the adhesive strength, i.e., the negative electrode cohesion.

[0195] 2. 0.1C discharge capacity, first-efficiency

[0196] At 60℃, charge at a constant current of 0.1C to 4.3V, then switch to constant voltage charging until the current is less than 0.05C. Record the initial charge capacity C1 at 0.1C. Then discharge at 0.1C to 2.5V and record the initial discharge capacity C2 at 0.1C, which is the 0.1C discharge capacity. C2 / C1×100% is the first efficiency.

[0197] 3. 0.33C capacity retention rate of 80% and number of cycles

[0198] At 60℃, charge at a constant current of 0.33C to 4.3V, then switch to constant voltage charging until the current is less than 0.05C, and then discharge at 0.33C to 2.5V. Record the initial discharge capacity C1 at 0.33C. Repeat this cycle X times, and record the discharge capacity C after X cycles. X Until C X / C1≤80%, then X is the number of cycles with a capacity retention of 80% at 0.33C.

[0199] [Table 1]

[0200] The battery corresponding to Example 1 achieved an initial efficiency of 85.2%, and its capacity retention only decreased to 80% after 2000 cycles at a relatively high rate of 0.33C, demonstrating high initial efficiency and cycle performance. This is mainly due to the cyanidation treatment of silicon-carbon during the preparation of the negative electrode, followed by heat treatment together with PAN. This process replaces the oxygen-containing functional groups on the surface of the silicon-carbon in the resulting negative electrode, mitigating the lithium swallowing phenomenon caused by these groups. Furthermore, PAN can react with the cyano groups on the silicon-carbon surface to form cyclized PAN. Cyclic PAN has high viscosity and high ion / electron transport performance, which improves the cohesiveness of the negative electrode, resulting in strong bonding between silicon-carbon particles (which helps maintain the structural stability of the negative electrode during battery cycling). The combined effect effectively improves the initial efficiency and cycle performance of the battery. Examples 2 to 4 exhibit performance comparable to Example 1.

[0201] Comparative Example 1 uses PVDF as a binder. Since PVDF lacks ion / electron transport capabilities, it hinders ion / electron transport, resulting in a lower initial discharge capacity and consequently reduced initial efficiency. Simultaneously, the insufficient viscosity of PVDF reduces the cohesive force of the negative electrode, making it easier for the bonding forces between components in the negative electrode sheet to decrease during cycling. This affects the structural stability of the negative electrode sheet, further reducing the battery's cycle performance.

[0202] Despite the addition of PAN and heat treatment during the preparation of the negative electrode in Comparative Example 2, its initial discharge capacity and cycle performance were significantly lower than those of Example 1. This is mainly due to: 1) The silicon-carbon surface retains oxygen-containing functional groups, and Comparative Example 2 cannot reduce these oxygen-containing functional groups. These oxygen-containing functional groups cause lithium absorption, converting some active lithium into inactive lithium, which cannot participate in the electrochemical reaction, leading to a decline in the battery's initial discharge capacity and cycle performance; 2) No cross-linking occurs between silicon-carbon and PAN, reducing the pathway for ion / electron transport between silicon-carbon particles through the cyclized PAN generated by the reaction. This hinders ion / electron transport, resulting in a lower initial discharge capacity and reduced initial discharge capacity and cycle performance; 3) The lack of cross-linking between silicon-carbon and PAN weakens the bonding force between silicon-carbon particles and the cohesion of the negative electrode, thereby reducing the structural stability of the negative electrode during battery cycling and thus reducing the battery's cycle performance.

[0203] 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 solid-state battery cell, characterized in that, The device includes a negative electrode sheet, which comprises a negative electrode current collector and a negative electrode active layer disposed on at least one side of the negative electrode current collector. The negative electrode active layer comprises a carbon material and a binder. The binder comprises a structural unit as shown in Formula I or a tautomer thereof. The carbon material is connected to the binder. Formula I, n=10000~100000.

2. The solid-state battery cell according to claim 1, characterized in that, The adhesive comprises cyclized polyacrylonitrile polymers.

3. The solid-state battery cell according to claim 1 or 2, characterized in that, The binder has a mass content of 3% to 8% in the negative electrode active layer.

4. The solid-state battery cell according to any one of claims 1 to 3, characterized in that, The binder has a mass content of 3% to 5% in the negative electrode active layer.

5. The solid-state battery cell according to any one of claims 1 to 4, characterized in that, The mass ratio of carbon to oxygen in the carbon material is above 1000.

6. The solid-state battery cell according to claim 5, characterized in that, The mass ratio of carbon to oxygen in the carbon material is 1000 to 2000.

7. The solid-state battery cell according to any one of claims 1 to 6, characterized in that, The carbon material includes one or more of silicon carbide, graphite, mesophase carbon microspheres, soft carbon, and hard carbon.

8. A negative electrode sheet, characterized in that, The device includes a negative electrode current collector and a negative electrode active layer disposed on at least one side of the negative electrode current collector. The negative electrode active layer includes a carbon material and a binder. The binder includes a structural unit as shown in Formula I or a tautomer thereof. The carbon material is connected to the binder. Formula I, n=10000~100000.

9. A method for preparing a negative electrode sheet, characterized in that, include: Carbon materials are cyanided to obtain cyano-carbon materials; A negative electrode active layer comprising the cyanocarbon material and a binder precursor is prepared on at least one side of the negative electrode current collector, wherein the binder precursor comprises the structural unit shown in Formula II. The cyanocarbon material undergoes a crosslinking reaction with the binder precursor; Formula II, n = 10000 ~ 100000.

10. The method for preparing the negative electrode sheet according to claim 9, characterized in that, The cyanocarbon material contains 2.5% to 6% cyano groups by mass.

11. The method for preparing the negative electrode sheet according to claim 9 or 10, characterized in that, The cyanocarbon material contains 3.5% to 4% cyano groups by mass.

12. The method for preparing the negative electrode sheet according to any one of claims 9 to 11, characterized in that, The method for cyaniding the carbon material includes: reacting the carbon material with a cyaniding reagent in a cyanidation reaction.

13. The method for preparing the negative electrode sheet according to claim 12, characterized in that, The cyaniding reagent includes one or more of trimethylcyanosilane, acetone cyanohydrin, sodium cyanide, potassium cyanide, hydrogen cyanide, and acrylonitrile.

14. The method for preparing the negative electrode sheet according to any one of claims 12 or 13, characterized in that, The mass ratio of the carbon material to the cyanide reagent is 100:(10-20).

15. The method for preparing the negative electrode sheet according to claim 14, characterized in that, The mass ratio of the carbon material to the cyanide reagent is 100:(15-17).

16. The method for preparing the negative electrode sheet according to any one of claims 9 to 15, characterized in that, The cyanidation treatment temperature is 20℃~50℃, and the cyanidation treatment time is 5h~20h.

17. The method for preparing the negative electrode sheet according to any one of claims 9 to 16, characterized in that, The cyanidation treatment is performed at a temperature of 25°C to 40°C for 8 hours to 12 hours.

18. The method for preparing the negative electrode sheet according to any one of claims 9 to 17, characterized in that, The binder precursor includes polyacrylonitrile polymers.

19. The method for preparing the negative electrode sheet according to any one of claims 9 to 18, characterized in that, The binder precursor has a mass content of 4% to 9% in the negative electrode active layer.

20. The method for preparing the negative electrode sheet according to any one of claims 9 to 19, characterized in that, The binder precursor has a mass content of 4% to 6% in the negative electrode active layer.

21. The method for preparing the negative electrode sheet according to any one of claims 9 to 20, characterized in that, A method for causing the cyanocarbon material to undergo a crosslinking reaction with the binder precursor includes: performing heat treatment under a protective atmosphere.

22. The method for preparing the negative electrode sheet according to claim 21, characterized in that, The heat treatment temperature is 200℃~350℃, and the heat treatment time is 4h~9h.

23. The method for preparing the negative electrode sheet according to claim 21 or 22, characterized in that, The heat treatment temperature is 280℃~320℃, and the heat treatment time is 4h~6h.

24. A battery device, characterized in that, It includes any one of the solid-state battery cells described in claims 1 to 7.

25. An energy storage device, characterized in that, It includes a solid-state battery cell according to any one of claims 1 to 7 or a battery device according to claims 24, wherein the solid-state battery cell or the battery device is used to store or provide electrical energy.

26. An electrical appliance, characterized in that, It includes a solid-state battery cell according to any one of claims 1 to 7 or a battery device according to claims 24, wherein the solid-state battery cell or the battery device is used to store or provide electrical energy.

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