Battery cell, battery device and electric device

Abstract

The invention relates to the technical field of batteries, in particular to a single battery, a battery device and a power utilization device. The negative electrode plate comprises a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector; the negative electrode film layer comprises a negative electrode active material; the negative electrode active material comprises an inner core layer and a shell layer, the inner core layer comprises graphite; and the shell layer comprises a metal silicide. The charge transfer impedance of the battery monomer is relatively small, so that the charging capability of the battery monomer can be improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a battery cell, a battery device, and an electrical device. Background Technology

[0002] Battery cells have a wide range of applications due to their excellent performance. In the existing technology, for battery cells with graphite as the negative electrode active material, the charge transfer impedance of the battery cell is relatively large due to the small number of active sites on the graphite surface, which limits its charging capacity. Summary of the Invention

[0003] In view of the above problems, this application provides a battery cell, a battery device, and an electrical device, wherein the battery cell has a low charge transfer impedance and a good charging capability.

[0004] In a first aspect, this application provides a battery cell, the battery cell including a negative electrode sheet;

[0005] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector;

[0006] The negative electrode film layer includes a negative electrode active material;

[0007] The negative electrode active material includes a core layer and a shell layer;

[0008] The core layer comprises graphite; the outer shell layer comprises metal silicide.

[0009] In the technical solution of this application, the metal element in the metal silicide has a low nucleation site and a good affinity for active ions, which increases the active sites on the graphite surface in the core layer and improves the charging capability of the battery cell. At the same time, the metal element in the negative electrode active material can be introduced into the solid electrolyte interface film formation, which reduces the charge transfer impedance of the battery cell, significantly improves the charging window of the battery cell, and further enhances the charging capability of the battery cell.

[0010] In some embodiments, at least a portion of the graphite on the outer surface of the core layer and at least a portion of the metal silicide on the inner surface of the outer shell layer form a metal silicon carbide compound.

[0011] In the technical solution of this application, the metal silicon carbide has metal-silicon bonds and carbon-silicon bonds. The carbon-silicon bonds can stabilize the combination of the metal silicon carbide and / or metal silicide metal-silicon bonds with graphite, so that the graphite in the core layer and the outer shell layer are stably combined, further improving the charging capability of the battery cell.

[0012] In some embodiments, the Dv50 particle size of the negative electrode active material is 1-30 μm, optionally 5-15 μm.

[0013] In the technical solution of this application, the Dv50 particle size of the negative electrode active material is within the above-mentioned range, which is beneficial to improving the structural stability of the negative electrode active material. The diffusion path of active ions in the core layer is shorter, which comprehensively improves the charging capability of the battery cell.

[0014] In some embodiments, the metal element in the metal silicide includes one or more of copper, iron, tantalum, tungsten, hafnium, niobium, vanadium, chromium, magnesium, zirconium, molybdenum, zinc, calcium, or titanium.

[0015] In the technical solution of this application, the metal element in the metal silicide is within the above-mentioned range. On the one hand, it has a low nucleation site, which increases the active site on the graphite surface; on the other hand, the metal element has strong reactivity and high binding ability with graphite, making it easier to form a stable metal silicon carbide compound, thus improving the overall charging capability of the battery cell.

[0016] In some embodiments, the Dv50 particle size of the metal silicide is 5-200 nm, optionally 5-20 nm.

[0017] In the technical solution of this application, the Dv50 particle size of the metal silicide is within the above-mentioned range. The outer shell layer formed by the metal silicide has a good coating effect on the core layer, which makes the structure of the negative electrode active material highly stable and increases the active sites on the graphite surface, which is beneficial to improving the charging capacity of the battery cell.

[0018] In some embodiments, the mass of the outer shell layer is 0.1%-30% of the total mass of the core layer, which is 100%; and / or;

[0019] The thickness of the outer shell layer is 1-10 nm, and optionally 3-7 nm.

[0020] In the technical solution of this application, the mass of the outer shell layer relative to the core layer is within the above-mentioned range, and the thickness of the outer shell layer is set within the above-mentioned range, which can enhance the structural stability of the negative electrode active material, reduce the side reactions between graphite and electrolyte in the core layer, and thus reduce the specific capacity loss of graphite.

[0021] In some embodiments, the compaction density of the negative electrode film layer is 1.6 g / cm³ when the battery cell is at 0% charge. 3 -1.8g / cm 3 .

[0022] In the technical solution of this application, the compaction density of the negative electrode sheet is within the above-mentioned range, and the electrochemical performance of the formed battery cell can be maintained at a relatively good level.

[0023] Secondly, this application provides a method for preparing a negative electrode active material, the method comprising the following steps:

[0024] An outer shell layer is formed on the surface of the core layer to obtain the negative electrode active material;

[0025] The core layer is made of graphite; the outer shell layer is made of metal silicide.

[0026] In some implementations, the arrangement includes placing the outer shell layer on the surface of at least a portion of the core layer, followed by heat treatment.

[0027] In some embodiments, the heat treatment temperature is 700-1200°C; and / or;

[0028] The heat treatment time is 1-10 hours.

[0029] In a second aspect, this application provides a battery device comprising a plurality of battery cells according to the first aspect.

[0030] Thirdly, this application provides an electrical device comprising the battery cell described in the first aspect, or the negative electrode active material obtained by the preparation method described in the second aspect, or the battery device described in the third aspect.

[0031] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0032] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0033] Figure 1 Scanning electron microscope (SEM) images of the negative electrode active materials of some embodiments of this application;

[0034] Figure 2 This is a scanning electron microscope image of the negative electrode active material of Comparative Example 1 of this application;

[0035] Figure 3 This is a comparison of X-ray diffraction patterns of Example 1 and Comparative Example 1 of this application;

[0036] Figure 4 This is a comparison chart of the rate performance of Example 1 and Comparative Example 1 of this application;

[0037] Figure 5 This is a comparison graph of charge transfer impedance tests for Example 1 and Comparative Example 1 of this application. Detailed Implementation

[0038] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0040] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0041] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0042] 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 also 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 "2-10" indicates that all real numbers between "2-10" have been listed in this article; "2-10" 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.

[0043] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0044] In the existing technology, for battery cells using graphite as the negative electrode active material, the charge transfer impedance of the resulting battery cell is relatively large due to the small number of active sites on the graphite surface, which limits its charging capacity.

[0045] This application improves the charging capability of a battery cell by providing a shell layer containing metal silicides on the surface of a graphite core layer, thereby increasing the active sites on the graphite surface and reducing the charge transfer impedance of the battery cell. This application also provides a battery cell, a battery device, and an electrical device.

[0046] [Battery cell]

[0047] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0048] The battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and the embodiments of this application are not limited to this.

[0049] [Electrode Assembly]

[0050] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator positioned between the negative and positive electrodes. During the charging and discharging process of a single battery cell, active ions (such as lithium ions or sodium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits while allowing active ions to pass through.

[0051] The electrode assembly can be a wound structure, a stacked structure, or a hybrid structure of wound and stacked.

[0052] In some embodiments, the electrode assembly is a wound structure. The positive electrode and the negative electrode are wound into a wound structure.

[0053] In some implementations, the electrode assembly is a stacked structure.

[0054] As an example, multiple positive and negative electrode plates can be set, and multiple positive and multiple negative electrode plates can be stacked alternately.

[0055] As an example, multiple positive electrode sheets can be set, and negative electrode sheets are folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0056] As an example, both the positive and negative electrode sheets are folded to form multiple stacked folded segments.

[0057] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0058] In some embodiments, the electrode assembly has tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0059] [Negative electrode plate]

[0060] This application provides a battery cell, the battery cell including a negative electrode sheet;

[0061] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector;

[0062] The negative electrode film layer includes a negative electrode active material;

[0063] The negative electrode active material includes a core layer and a shell layer;

[0064] The core layer comprises graphite; the outer shell layer comprises metal silicide.

[0065] In this application, the graphite in the core layer and the metal silicide in the outer shell layer of the negative electrode active material in the battery cell can be analyzed by combining electron microscopy, X-ray diffraction, and energy dispersive spectroscopy. Specifically, electron microscopy, such as transmission electron microscopy or scanning electron microscopy, is first used to understand the structural information of the sample. Then, X-ray diffraction is used to determine the crystal structure and phase composition of the sample. Finally, energy dispersive spectroscopy is used to perform specific material identification and analysis on the core layer and outer shell layer of the negative electrode active material.

[0066] The specific testing process is as follows:

[0067] (1) Sample preparation: The electrode is soaked in water, and the negative electrode active material is obtained from the negative electrode film layer by methods such as phase separation. The samples required for each test process are prepared. Among them, the samples tested by the energy dispersive spectrometer need to be broken to expose the core layer and the outer shell layer.

[0068] (2) Electron microscopy test: The sample is scanned by an electron microscope. According to the test standard GB / T0584-2020, a high-resolution image and structural information of the sample are acquired by a Zeiss Sigma 300 scanning electron microscope to obtain high-resolution image and structural information.

[0069] (3) X-ray diffraction test: The sample is scanned by an X-ray diffractometer according to the national standard GB / T 30904-2014, and the diffraction pattern is collected to determine the crystal structure and phase composition of the sample.

[0070] (4) Energy dispersive spectrometer test: The sample is scanned by an energy dispersive spectrometer according to the national standard GB / T 17359-2023 to collect the spectrum, and qualitative and quantitative analysis of the elements in the core layer and the outer shell layer is performed to complete the specific material identification and analysis.

[0071] In this application, the metal silicide is selected from products with high purity, such as 80%-99.99%, to reduce the influence of unknown impurities.

[0072] In the technical solution of this application embodiment, the metal element in the metal silicide has a low nucleation site and a good affinity for active ions, which increases the active sites on the graphite surface in the core layer and improves the charging capability of the battery cell. At the same time, the metal element in the negative electrode active material can be introduced into the solid electrolyte interface film formation, which reduces the charge transfer impedance of the battery cell, significantly improves the charging window of the battery cell, and further enhances the charging capability of the battery cell.

[0073] In some embodiments, at least a portion of the graphite on the outer surface of the core layer and at least a portion of the metal silicide on the inner surface of the outer shell layer form a metal silicon carbide compound.

[0074] In this application, the metal silicon carbide is formed by heat treatment, such as silicon (Si) and carbon (C) forming silicon carbide (SiC) at high temperature, and metal silicide (M-Si, where M represents a metal element) and C in graphite forming metal silicon carbide (M-Si-C) through heat treatment.

[0075] In the technical solution of this application embodiment, the metal silicon carbide has metal-silicon bonds and carbon-silicon bonds. The carbon-silicon bonds can stabilize the combination of the metal silicon carbide and / or metal silicide metal-silicon bonds with graphite, so that the graphite in the core layer and the outer shell layer are stably combined, further improving the charging capability of the battery cell.

[0076] In some embodiments, the Dv50 particle size of the negative electrode active material is 1-30 μm, optionally 5-15 μm, such as 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, etc.

[0077] In this application, the Dv50 particle size refers to the median particle size, specifically the volume average particle size of the material. Dv50 refers to the particle size corresponding to 50% of the volume distribution. It can be detected using equipment and methods known in the art. For example, using the negative electrode active material as a sample, the Dv50 particle size of the particles can be tested using a Mastersizer 2000E laser particle size analyzer according to the testing standard GB / T 19077-2016.

[0078] In the technical solution of this application embodiment, the Dv50 particle size of the negative electrode active material is within the above-mentioned range, which is beneficial to improving the structural stability of the negative electrode active material. The diffusion path of active ions in the core layer is shorter, which comprehensively improves the charging capability of the battery cell. In some embodiments, the metal element in the metal silicide includes one or more of copper, iron, tantalum, tungsten, hafnium, niobium, vanadium, chromium, magnesium, zirconium, molybdenum, zinc, calcium, or titanium.

[0079] In the technical solution of this application embodiment, the metal element in the metal silicide is within the above-mentioned range. On the one hand, it has a low nucleation site, which increases the active site on the graphite surface; on the other hand, the metal element has strong reactivity and high binding ability with graphite, making it easier to form a stable metal silicon carbide compound, thus improving the overall charging capability of the battery cell.

[0080] In some embodiments, the Dv50 particle size of the metal silicide is 5-200 nm, optionally 5-20 nm, such as 10 nm, 50 nm, 100 nm, 150 nm, etc.

[0081] In the technical solution of this application embodiment, the Dv50 particle size of the metal silicide is within the above range, and the outer shell layer formed by the metal silicide has a good coating effect on the core layer, which makes the structure of the negative electrode active material highly stable and increases the active sites on the graphite surface, which is beneficial to improving the charging capacity of the battery cell.

[0082] In some embodiments, the mass of the outer shell layer is 0.1%-30% of the total mass of the core layer, optionally 0.5%-10%, such as 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, etc.; and / or;

[0083] The thickness of the outer shell layer is 1-10nm, optionally 3-7nm, such as 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, etc.

[0084] In this application, the thickness of the outer shell layer is adjusted by the mass ratio of the core layer and the outer shell layer. For large graphite particles in the core layer, the amount of metal silicide added in the outer shell layer can be appropriately increased to make the thickness of the outer shell layer within the required range; for small graphite particles, the amount of metal silicide added in the outer shell layer can be appropriately reduced to make the thickness of the outer shell layer within the required range.

[0085] In the technical solution of this application embodiment, the mass of the outer shell layer relative to the core layer is within the above-mentioned range, and the thickness of the outer shell layer is set within the above-mentioned range, which can enhance the structural stability of the negative electrode active material, reduce the side reaction between graphite and electrolyte in the core layer, and thus reduce the specific capacity loss of graphite.

[0086] In some embodiments, the negative electrode current collector may be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals may be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by depositing a polymer material substrate (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.) on the surface of a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.).

[0087] In some embodiments, when the battery cell is at 0% charge, the compaction density of the negative electrode film is 1.6-1.8 g / cm³. 3 For example, 1.7 g / cm³ 3 wait.

[0088] In this application, the compaction density refers to the mass of negative electrode active material contained in a unit volume of the negative electrode sheet under a certain pressure. The calculation formula is: Compaction density = Areal density / (Thickness of the electrode sheet after compaction - Thickness of the negative electrode current collector). Wherein, areal density is the mass of negative electrode active material coated on the surface of the negative electrode current collector per unit area.

[0089] In this application, the 0% state of charge refers to the battery cell being in a completely delithiated state, i.e., delithiated at 0.33C to the specified cutoff voltage of 2.0V, reaching a 0% state of charge. In this state, the remaining charge in the battery cell is zero, meaning the battery cell has used up all its available charge and cannot provide any more electrical energy. Therefore, the compaction density described in this application is the result of disassembling the battery cell in a 0% state of charge and then testing the resulting electrode sheets.

[0090] In the technical solution of this application embodiment, the compaction density of the negative electrode sheet is within the above range, and the electrochemical performance of the formed battery cell can be maintained at a relatively good level.

[0091] In some embodiments, the graphite includes, but is not limited to, one or more of artificial graphite, natural graphite, mesophase carbon microspheres, or hard carbon.

[0092] In some embodiments, the negative electrode film layer further includes a conductive agent and / or a binder.

[0093] As an example, the conductive agent includes one or more of carbon black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0094] As an example, the carbon black includes one or more of acetylene black, Ketjen black, or Super P.

[0095] As an example, the adhesive includes one or more of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), or polymethyl methacrylate (PMMA).

[0096] [Preparation of negative electrode active materials]

[0097] This application provides a method for preparing a negative electrode active material, the method comprising the following steps:

[0098] An outer shell layer is formed on the surface of the core layer to obtain the negative electrode active material;

[0099] The core layer is made of graphite; the outer shell layer is made of metal silicide.

[0100] In some embodiments, the arrangement includes placing the outer shell layer on the surface of at least a portion of the core layer before heat treatment.

[0101] As an example, a method of placing the outer shell layer on the surface of at least part of the core layer includes mixing the raw materials of the core layer, such as graphite, and the raw materials of the outer shell layer, such as metal silicides, to achieve uniform dispersion.

[0102] In some embodiments, the temperature of the heat treatment is 700-1200°C, such as 750°C, 800°C, 850°C, 900°C, 1000°C, 1050°C, 1100°C, 1150°C, etc.; and / or;

[0103] The heat treatment time is 1-10 hours, for example, 2 hours, 4 hours, 6 hours, 8 hours, etc.

[0104] In some embodiments, the heat treatment is performed in an inert atmosphere.

[0105] In some embodiments, the heat treatment process further includes grinding, crushing, and sieving.

[0106] In some embodiments, the preparation method further includes nano-sizing the raw material of the metal silicide. If the particle size of the raw material of the metal silicide itself meets the requirements, then nano-sizing is not necessary.

[0107] As an example, the nano-sizing process includes operations such as ball milling and / or air jet milling, ultrasonication, washing with water, and drying. The ball milling process includes wet ball milling and / or dry ball milling.

[0108] The process parameters are as follows:

[0109] The mass ratio of the balls to the material is (5-15):1, such as 10:1, etc.

[0110] The ball mill's rotation speed is 100-1000 rpm, such as 200 rpm, 400 rpm, 600 rpm, 800 rpm, etc.

[0111] The ball milling time is 1-10 hours, such as 2 hours, 4 hours, 6 hours, 8 hours, etc.

[0112] The ball milling operation is carried out in an alcohol solvent such as ethanol.

[0113] The power of ultrasound is 100-500W / cm. 2 For example, 200W / cm 2 300W / cm 2 400W / cm 2 wait.

[0114] The ultrasound session lasts 1-5 hours, for example, 2 hours, 3 hours, 4 hours, etc.

[0115] As an example, the nano-sizing process specifically includes: ball milling the metal silicide raw material in an alcohol solvent at a ball-to-material mass ratio of (5-15):1 for 1-10 hours at a speed of 100-1000 rpm, and then... 2 The metal silicide is subjected to ultrasonication for 1-5 hours under certain conditions, followed by washing and drying to obtain the metal silicide.

[0116] In some embodiments, the method for preparing the negative electrode active material includes:

[0117] Graphite and metal silicide are mixed and uniformly dispersed, and then heat-treated at 700-1200℃ for 1-10 hours in an inert atmosphere. After grinding, crushing and sieving, the negative electrode active material is obtained.

[0118] Optionally, the metal silicide is nano-sized before mixing.

[0119] In some embodiments, the method for preparing the negative electrode sheet includes: dissolving a negative electrode material, such as a negative electrode active material, a conductive agent, a binder, and other arbitrary components (such as thickeners, such as sodium carboxymethyl cellulose) in a solvent (such as deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector; and then drying, cold pressing, and slitting the slurry to obtain the negative electrode sheet.

[0120] [Positive electrode plate]

[0121] In some embodiments, the battery cell further includes a positive electrode sheet.

[0122] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector.

[0123] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0124] As an example, the positive current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by setting a polymer material substrate (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.) on the surface of a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.).

[0125] In some embodiments, the positive electrode film layer includes a positive electrode active material.

[0126] As an example, the positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphate may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as 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 oxide may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Modified compounds refer to substances obtained by modification methods such as doping or coating based on the above-mentioned substances.

[0127] In some embodiments, the positive electrode film layer further includes a conductive agent and / or a binder.

[0128] As an example, the conductive agent includes one or more of carbon black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0129] As an example, the carbon black includes one or more of acetylene black, Ketjen black, or Super P.

[0130] As an example, the adhesive includes one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, or fluorinated acrylate resin.

[0131] In some embodiments, the method for preparing the positive electrode sheet includes: dissolving a positive electrode material, such as a positive electrode active material, a conductive agent, a binder, and other arbitrary components in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto a negative electrode current collector; and then drying, cold pressing, and slitting the slurry to obtain the positive electrode sheet.

[0132] [Isolation Component]

[0133] In some embodiments, the battery cell further includes a separator disposed between the positive electrode and the negative electrode.

[0134] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0135] As an example, the separator can be continuously arranged between any adjacent positive or negative electrode plates by folding or rolling.

[0136] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0137] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a single component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0138] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrode plates, serving both to transport ions and to isolate the positive and negative electrodes.

[0139] [Electrolytes]

[0140] In some embodiments, the battery cell further includes an electrolyte. The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte, which can be selected according to requirements. The electrolyte can be liquid, gel, or solid.

[0141] Liquid electrolytes include electrolyte salts and solvents.

[0142] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0143] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0144] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the battery cell, such as additives that improve the overcharge / fast charge performance of the battery cell, additives that improve the high-temperature performance of the battery cell, and additives that improve the low-temperature performance of the battery cell.

[0145] The gel electrolyte includes a polymer as a backbone network and can be used in conjunction with an ionic liquid-lithium salt.

[0146] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0147] As an example, the polymers of polymeric solid electrolytes may include polyethers (polyoxyethylene), polysiloxanes, polycarbonates, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids, cellulose, etc.

[0148] As an example, inorganic solid electrolytes can be one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium germanium phosphorus sulfide, silver sulfide germanium ore), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0149] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0150] [Battery Device]

[0151] In some embodiments, a battery cell may include a casing. The casing may be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc. In some embodiments, the casing may be a sealed structure or a non-sealed structure. As an example, when the casing is a non-sealed structure, the casing serves to protect the electrode assembly, and a sealing bag is included between the casing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag may be a bag-shaped insulating component or an aluminum-plastic film. When the casing is a sealed structure, it is used to encapsulate components such as the electrode assembly and electrolyte.

[0152] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0153] In some embodiments, the housing includes an end cap and a housing, the housing having an opening, and the end cap covering the opening. The housing may have one or more openings. The end cap may also be provided one or more.

[0154] 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 battery cells connected in series, parallel, or mixed connections via a busbar.

[0155] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0156] 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.

[0157] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0158] 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.

[0159] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] [ Electrical appliances ]

[0164] This application provides an electrical device, which includes the aforementioned battery cell.

[0165] In some embodiments, the electrical device includes at least one of the battery modules or battery packs provided in any embodiment of this application.

[0166] The battery cells, battery modules, or battery packs described in this application can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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., including but not limited to these.

[0167] [Example]

[0168] Example 1

[0169] Negative electrode plate:

[0170] (1) Preparation of negative electrode active material:

[0171] Commercially available metal silicides (magnesium silicides) were nano-sized using a planetary ball mill with a ball-to-material mass ratio of 10:1. Ethanol solvent was added, ensuring the solvent completely covered the materials. The milling speed was set at 400 rpm for 6 hours to obtain an ethanol solution of the metal silicides. This ethanol solution was then subjected to ultrasonic treatment at a power of 300 W / cm². 2 The mixture was ultrasonicated for 2 hours; finally, it was dried, washed with water, and dried again to obtain nano-sized metal silicides.

[0172] Artificial graphite and metal silicide are mixed according to the formula and dispersed evenly. Then, in an inert atmosphere, they are heat-treated at 900°C for 5 hours to form metal silicon carbide compounds from at least a portion of the artificial graphite on the outer surface of the core layer and at least a portion of the metal silicide on the inner surface of the outer shell layer. The mixture is then ground, pulverized, and sieved to obtain the negative electrode active material. The specific information of its structure is shown in Table 1.

[0173] (2) Preparation of negative electrode sheet: The negative electrode active material, conductive carbon black, binder (SBR) and carboxymethyl cellulose (CMC) are uniformly mixed in water at a weight ratio of 80:10:3:7 to form a negative electrode slurry. The slurry is then coated onto copper foil, and after cold pressing and cutting, a compacted density of 1.7 g / cm³ is obtained. 3 The negative electrode sheet.

[0174] Separator: A polyethylene film with a thickness of 13μm is used as the separator.

[0175] Electrolyte: Ethyl carbonate, diethyl carbonate, and dimethyl carbonate were mixed in a volume ratio of 1:1:1. Lithium hexafluorophosphate (LiPF6) was dissolved in the above solution to obtain the electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L.

[0176] Assembly: Using lithium sheets as the counter electrode, a secondary battery is manufactured.

[0177] Example 2

[0178] The difference between this embodiment and Embodiment 1 is that no heat treatment was performed, that is, the graphite on the outer surface of the core layer and the metal silicide on the inner surface of the outer shell layer did not form a metal silicon carbide compound. All other aspects are the same as in Embodiment 1.

[0179] Examples 2-10 and Comparative Example 1

[0180] Except for the parameters in Table 1, the secondary battery was obtained according to the method described in Example 1.

[0181] Table 1

[0182]

[0183] In the table, "—" represents data that is not included.

[0184] The scanning electron microscope (SEM) images of the negative electrode active materials prepared in Example 1 and Comparative Example 1 are shown below. Figure 1 and Figure 2 As shown, the results indicate that Figure 1 Compared to Figure 2 The surface of the negative electrode active material is rough, and it combines with... Figure 3 The XRD test results prove that the negative electrode active material described in this application was successfully prepared.

[0185] [Performance Testing]

[0186] (1) Charge transfer impedance (EIS) test: At an ambient temperature of 25℃, an electrochemical workstation was used with a voltage range of 0.005-5V and an AC micro-perturbation current of 5mV to test the charge transfer impedance of the secondary battery.

[0187] (2) Charging capacity test: The first charge and discharge test was conducted at an ambient temperature of 25℃. The test voltage range was 0.05-2V. The charge and discharge rate was 0.05C discharge and 0.1C charge. After completing the basic charge and discharge test, the charge and discharge current density was changed to conduct tests at different rates. The rates were 0.1C, 0.5C, 1C, 2C, 4C, 6C, and 0.5C. Each rate was cycled 10 times. The discharge capacity was recorded, and the specific capacity was calculated by dividing the discharge capacity by the mass of the negative electrode active material.

[0188] The test results are summarized in Table 2-3 and Figure 4-5 middle.

[0189] Table 2

[0190] Charge transfer impedance (Ω) Example 1 3.01 Example 2 3.55 Example 3 3.55 Example 4 3.30 Example 5 3.51 Example 6 3.51 Example 7 3.54 Example 8 3.36 Example 9 3.48 Example 10 3.45 Comparative Example 1 3.65

[0191] Analysis of the data in Table 2 shows that the charge transfer impedance of the battery cell described in this application is below 3.55Ω; the charge transfer impedance of the battery cell described in this application is relatively low.

[0192] Analysis of Comparative Example 1 and Example 1 shows that, combined with Figure 4 It can be seen that the performance of Comparative Example 1 is not as good as that of Example 1, which proves that the battery cell formed by the negative electrode active material described in this application has better performance.

[0193] Analysis of Example 2 and Example 1 shows that the performance of Example 2 is not as good as that of Example 1, which proves that the battery cell formed by the combination of at least part of the graphite on the outer surface of the core layer and at least part of the metal silicide on the inner surface of the outer shell layer to form a metal silicon carbide compound has better performance.

[0194] Analysis of Example 3 and Example 1 shows that the performance of Example 3 is not as good as that of Example 1, which proves that the negative electrode active material formed by the Dv50 particle size of metal silicide within the specified range is more conducive to improving the performance of battery cells.

[0195] Analysis of Example 7 and Example 1 shows that the performance of Example 7 is not as good as that of Example 1, which proves that the negative electrode active material formed within the Dv50 particle size range is more conducive to improving the performance of the battery cell.

[0196] Analysis of Examples 10 and 8 shows that the performance of Example 10 is not as good as that of Example 8, proving that the thickness of the outer shell layer of the negative electrode active material within the specified range is more conducive to improving the performance of the battery cell.

[0197] Table 3

[0198]

[0199] Analysis of the data in Table 3 shows that the specific capacity of the battery cells described in this application after 10 cycles at 0.1C, 0.5C, 1C, 2C, 4C, 6C, and 0.5C are 345.4-350.0 mAh / g, 286.6-291.5 mAh / g, 259.6-279.6 mAh / g, 238.21-270.3 mAh / g, 143.9-187.2 mAh / g, 99.3-133.9 mAh / g, and 276.0-286.5 mAh / g, respectively. The battery cells described in this application have excellent rate performance and good charging capability.

[0200] Analysis of Comparative Example 1 and Example 1 shows that, combined with Figure 5 It can be seen that the performance of Comparative Example 1 is not as good as that of Example 1, which proves that the battery cell formed by the negative electrode active material described in this application has better performance.

[0201] Analysis of Example 2 and Example 1 shows that the performance of Example 2 is not as good as that of Example 1, which proves that the battery cell formed by the combination of at least part of the graphite on the outer surface of the core layer and at least part of the metal silicide on the inner surface of the outer shell layer to form a metal silicon carbide compound has better performance.

[0202] Analysis of Example 3 and Example 1 shows that the performance of Example 3 is not as good as that of Example 1, which proves that the negative electrode active material formed by the Dv50 particle size of metal silicide within the specified range is more conducive to improving the performance of battery cells.

[0203] Analysis of Example 7 and Example 1 shows that the performance of Example 7 is not as good as that of Example 1, which proves that the negative electrode active material formed within the Dv50 particle size range is more conducive to improving the performance of the battery cell.

[0204] Analysis of Examples 10 and 8 shows that the performance of Example 10 is not as good as that of Example 8, proving that the thickness of the outer shell layer of the negative electrode active material within the specified range is more conducive to improving the performance of the battery cell.

[0205] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized in that, The battery cell includes a negative electrode sheet; The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector; The negative electrode film layer includes a negative electrode active material; The negative electrode active material includes a core layer and a shell layer; The core layer comprises graphite; the outer shell layer comprises metal silicide.

2. The battery cell according to claim 1, characterized in that, At least a portion of the graphite on the outer surface of the core layer and at least a portion of the metal silicide on the inner surface of the outer shell layer form a metal silicon carbide compound.

3. The battery cell according to claim 1 or 2, characterized in that, The Dv50 particle size of the negative electrode active material is 1-30 μm, and optionally 5-15 μm.

4. The battery cell according to any one of claims 1-3, characterized in that, The metal element in the metal silicide includes one or more of copper, iron, tantalum, tungsten, hafnium, niobium, vanadium, chromium, magnesium, zirconium, molybdenum, zinc, calcium, or titanium.

5. The battery cell according to any one of claims 1-4, characterized in that, The Dv50 particle size of the metal silicide is 5-200 nm, optionally 5-20 nm.

6. The battery cell according to any one of claims 1-5, characterized in that, With the total mass of the core layer being 100%, the mass of the outer shell layer is 0.1%-30%; and / or; The thickness of the outer shell layer is 1-10 nm, and optionally 3-7 nm.

7. The battery cell according to any one of claims 1-6, characterized in that, When the battery cell is at 0% charge, the compaction density of the negative electrode film is 1.6-1.8 g / cm³. 3 .

8. A method for preparing a negative electrode active material, characterized in that, The preparation method includes the following steps: An outer shell layer is formed on the surface of the core layer to obtain the negative electrode active material; The core layer is made of graphite; the outer shell layer is made of metal silicide.

9. The preparation method according to claim 8, characterized in that, The configuration method includes placing the outer shell layer on the surface of at least a portion of the core layer, followed by heat treatment.

10. The preparation method according to claim 9, characterized in that, The heat treatment temperature is 700-1200℃; and / or; The heat treatment time is 1-10 hours.

11. A battery device, characterized in that, The battery device comprises a plurality of battery cells according to any one of claims 1-7.

12. An electrical appliance, characterized in that, The electrical device includes a battery cell according to any one of claims 1-7, or a negative electrode active material obtained by the preparation method according to any one of claims 8-10, or a battery device according to claim 11.

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