Negative electrode sheet, secondary battery, battery module, battery pack, power device

Abstract

The present application provides a negative electrode sheet, comprising a coating layer and a current collector, wherein the coating layer is located on at least one surface of the current collector, and the coating layer comprises a first coating layer and a second coating layer, wherein the first coating layer is coated on the surface of the current collector, and the second coating layer is coated on the surface of the first coating layer. The first coating layer comprises a silicon-based material, and the second coating layer comprises one or more selected from Mg, Ca, and Al as metal particles.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and in particular to a negative electrode plate, a secondary battery, a battery module, a battery pack and an electrical device. Background Art

[0002] In recent years, as the application scope of lithium-ion secondary batteries has become more and more extensive, lithium-ion secondary batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. As lithium-ion secondary batteries have made great progress, higher requirements have been put forward for their energy density, cycle performance and safety performance. In addition, as the choice of negative electrode active materials is increasingly limited, silicon-based active materials are considered to be the best choice to meet the requirements of high energy density.

[0003] However, silicon-based materials have high surface activity and produce volume expansion effect during charge and discharge cycles, which leads to the powderization of silicon-based materials. Improving the cycle performance of materials by coating or doping is currently a relatively effective method, but the existing methods will cause different degrees of damage to the performance of lithium-ion secondary batteries, for example, the gram capacity of lithium-ion secondary batteries is reduced, the cycle performance is deteriorated, etc. Therefore, the existing silicon-based material modification technology still needs to be improved. Summary of the invention

[0004] Technical problem to be solved by the invention

[0005] The present application is made in view of the above-mentioned problems, and its object is to provide a negative electrode sheet so that a secondary battery including the negative electrode sheet has both high energy density and excellent cycle performance.

[0006] Technical solutions to solve problems

[0007] In order to achieve the above-mentioned objectives, the present application provides a negative electrode plate, a secondary battery, a battery module, a battery pack and an electrical device.

[0008] The first aspect of the present application provides a negative electrode plate, comprising a coating layer and a current collector, wherein the coating layer is located on at least one surface of the current collector, and the coating layer comprises a first coating layer and a second coating layer, wherein the first coating layer is coated on the surface of the current collector, and the second coating layer is coated on the surface of the first coating layer. The first coating layer comprises a silicon-based material, and the second coating layer comprises one or more selected from Mg, Ca, and Al as metal particles.

[0009] Hence, see Figure 1The negative electrode plate of the present application is provided with a first coating and a second coating. In the first coating, the silicon-based material is used as the negative electrode active material, which has a high discharge gram capacity, thereby ensuring the energy density of the lithium-ion secondary battery. The second coating contains metal particles Ca, Mg, and Al. During the cycle of the negative electrode plate, the above metal particles can form a stable Li-metal-Si phase with the silicon-based material and the embedded lithium ions, thereby inhibiting the surface activity of the silicon-based material and reducing the side reactions between the silicon-based material and the electrolyte, thereby greatly improving the cycle performance of the lithium-ion secondary battery containing the negative electrode plate.

[0010] In any embodiment, the silicon-based material is SiO x (0≤x<2), Si, a mixture of Si and graphite, or more thereof, wherein, in the mixture of Si and graphite, relative to the total weight of the mixture of Si and graphite, the weight ratio of Si is 40-70%, and the weight ratio of graphite is 30-60%. Therefore, from the perspective of improving the energy density of lithium-ion secondary batteries, the above silicon-based materials are selected as negative electrode active materials.

[0011] In any embodiment, in the second coating layer, the metal particles have a Dv50 of 50-500 nm, and the weight ratio of the metal particles relative to the total weight of the second coating layer is 40-80%.

[0012] Therefore, from the perspective of processing convenience and production cost, metal particles within the above-mentioned Dv50 range are selected. Metal powders with a smaller Dv50 are difficult to process and have higher costs, and the mass of a single particle is small, so it is easy to fly, the storage cost increases, and there is a greater safety risk. However, when the Dv50 of the metal particles is too large, the gap between the metal particles is larger, and the metal particle layer at the same thickness is reduced, so the metal particles cannot effectively cover the silicon-based material. Metal particles with a Dv50 that is too large can also easily lead to processing problems, such as coating wiredrawing and other problems.

[0013] In any embodiment, in the first coating layer, the Dv50 of the silicon-based material is 1.5-5 μm, and the weight proportion of the silicon-based material relative to the total weight of the first coating layer is 90-97%.

[0014] Therefore, when the Dv50 of the silicon-based material is within the above range, the negative electrode plate has excellent processing performance. At the same time, when the silicon-based material is within the above weight ratio range, the lithium-ion secondary battery containing the negative electrode plate has a higher energy density.

[0015] In any embodiment, the weight ratio of the metal particles to the silicon-based material is 0.03 to 0.1:1 relative to the total weight of the metal particles and the silicon-based material.

[0016] Therefore, from the perspective of the silicon-based material that can be fully covered by the metal particles, the weight ratio of the silicon-based material to the metal particles is selected in the present application to be within the above range. If the content of the metal particles is low, a relatively complete coating layer cannot be formed on the surface of the silicon-based material, and the improvement effect of the cycle performance is poor; if the content of the metal particles is too high, it affects the loading amount of the negative electrode active material in the negative electrode plate, and further affects the energy density of the lithium-ion secondary battery containing the negative electrode plate.

[0017] In any embodiment, the coating weight of the first coating layer is CW=0.14-0.2 g / 1540.25 mm 2 Therefore, from the perspective of ensuring the energy density of lithium-ion secondary batteries, the present application selects the above coating weight range.

[0018] In any embodiment, the thickness of the first coating is 30 to 50 μm, and the thickness of the second coating is 500 to 2000 nm. Therefore, when the thickness of the second coating in the present application is too thin, processing is difficult and the coverage effect of the second coating is poor, and it is not easy to improve the cycle performance of the lithium-ion secondary battery; when the thickness of the second coating is too thick, the Li-metal-Si phase formed during the first charge and discharge process will consume a large amount of active lithium ions, thereby damaging the energy density of the lithium-ion secondary battery. When the thickness of the first coating is within the above range, the negative electrode sheet has better processing performance, which is conducive to the winding and assembly of the battery cell.

[0019] A second aspect of the present application provides a secondary battery, comprising the negative electrode sheet of the first aspect of the present application.

[0020] A third aspect of the present application provides a battery module, comprising the secondary battery of the second aspect of the present application.

[0021] A fourth aspect of the present application provides a battery pack comprising the battery module of the third aspect of the present application.

[0022] The fifth aspect of the present application provides an electrical device comprising at least one selected from the secondary battery of the second aspect of the present application, the battery module of the third aspect of the present application, or the battery pack of the fourth aspect of the present application.

[0023] Effects of the Invention

[0024] The present application provides a negative electrode plate, a secondary battery, a battery module, a battery pack and an electric device. The second coating of the negative electrode plate of the present application contains metal particles Ca, Mg and Al. During the cycle of the negative electrode plate, the above metal particles can form a stable Li-metal-Si phase with the silicon-based material and the embedded lithium ions, thereby inhibiting the surface activity of the silicon-based material and reducing the side reactions between the silicon-based material and the electrolyte, thereby greatly improving the cycle performance of the lithium-ion secondary battery containing the negative electrode plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the negative electrode sheet of the present application.

[0026] Figure 2 It is a cycle performance diagram of the secondary battery of Example 1 and Comparative Example 1 of the present application.

[0027] Figure 3 is a schematic diagram of a secondary battery according to one embodiment of the present application.

[0028] Figure 4 yes Figure 3 An exploded view of a secondary battery according to an embodiment of the present application is shown.

[0029] Figure 5 is a schematic diagram of a battery module according to an embodiment of the present application.

[0030] Figure 6 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0031] Figure 7 yes Figure 6 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0032] Figure 8 FIG. 1 is a schematic diagram of an electric device using a secondary battery according to an embodiment of the present application as a power source.

[0033] Description of reference numerals:

[0034] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 top cover assembly DETAILED DESCRIPTION

[0035] Below, the embodiments of the negative electrode plate, secondary battery, battery module, battery pack and electric device of the present application are specifically disclosed with appropriate reference to the drawings in detail. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0036] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0037] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0038] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0039] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0040] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0041] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": 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).

[0042] Negative electrode

[0043] In one embodiment of the present application, the present application proposes a negative electrode plate, characterized in that it includes a coating layer and a current collector, the coating layer is located on at least one surface of the current collector, the coating layer includes a first coating layer and a second coating layer, the first coating layer is coated on the surface of the current collector, and the second coating layer is coated on the surface of the first coating layer. Wherein, the first coating layer includes a silicon-based material, and the second coating layer includes one or more of Mg, Ca, and Al as metal particles.

[0044] Although the mechanism is not yet clear, the applicant has unexpectedly discovered through a large number of experiments that the present application sets a first coating and a second coating on the negative electrode plate. In the first coating, the silicon-based material is used as the negative electrode active material and has a high gram capacity, thereby ensuring the energy density of the lithium-ion secondary battery. The second coating contains metal particles Ca, Mg, and Al. The above metal particles can form a stable Li-metal-Si phase with the silicon-based material and the embedded lithium ions, thereby inhibiting the surface activity of the silicon-based material and reducing the side reactions between the silicon-based material and the electrolyte, thereby greatly improving the cycle performance of the lithium-ion secondary battery containing the negative electrode plate. For example, see Figure 2 , Figure 2 This is a cycle performance diagram of Example 1 and Comparative Example 1 of the present application, showing the negative electrode plate during the charge and discharge cycle.

[0045] In some embodiments, the silicon-based material is SiO x (0≤x<2), Si, a mixture of Si and graphite, or more thereof, wherein, in the mixture of Si and graphite, relative to the total weight of the mixture of Si and graphite, the weight ratio of Si is 40-70%, and the weight ratio of graphite is 30-60%. Therefore, from the perspective of improving the energy density of lithium-ion secondary batteries, the above silicon-based materials are selected as negative electrode active materials.

[0046] In some embodiments, in the second coating layer, the metal particles have a Dv50 of 50-500 nm, and the weight ratio of the metal particles relative to the total weight of the second coating layer is 40-80%.

[0047] Therefore, from the perspective of processing convenience and production cost, metal particles within the above-mentioned Dv50 range are selected. Metal powders with a smaller Dv50 are difficult to process and have higher costs, and the mass of a single particle is small, so it is easy to fly, the storage cost increases, and there is a greater safety risk. However, when the Dv50 of the metal particles is too large, the gap between the metal particles is larger, and the metal particle layer at the same thickness is reduced, so the metal particles cannot effectively cover the silicon-based material. Metal particles with a Dv50 that is too large can also easily lead to processing problems, such as coating wiredrawing and other problems.

[0048] In some embodiments, in the first coating layer, the Dv50 of the silicon-based material is 1.5-5 μm, and the weight ratio of the silicon-based material relative to the total weight of the first coating layer is 90-97%.

[0049] Therefore, when the Dv50 of the silicon-based material is within the above range, the negative electrode plate has excellent processing performance. At the same time, when the silicon-based material is within the above weight ratio range, the lithium-ion secondary battery containing the negative electrode plate has a higher energy density.

[0050] In some embodiments, the weight ratio of the metal particles to the silicon-based material is 0.03 to 0.1:1 relative to the total weight of the silicon-based material and the metal particles. Therefore, from the perspective of the silicon-based material that can be fully covered by the metal particles, the weight ratio of the silicon-based material to the metal particles is selected in the present application to be within the above range. If the content of metal particles is low, a relatively complete coating layer cannot be formed on the surface of the silicon-based material, and the improvement effect of the cycle performance is poor; if the content of metal particles is too high, it affects the load of the negative electrode active material in the negative electrode plate, thereby affecting the energy density of the lithium-ion secondary battery containing the negative electrode plate.

[0051] In some embodiments, the coating weight of the first coating is CW=0.14-0.2 g / 1540.25 mm 2 Therefore, from the perspective of ensuring the energy density of the lithium-ion secondary battery, the present application selects the above coating weight.

[0052] In some embodiments, the thickness of the first coating is 30 to 50 μm, and the thickness of the second coating is 500 to 2000 nm. Therefore, when the thickness of the second coating is too thin, the processing is difficult and the coverage effect of the second coating is poor, which is not enough to improve the cycle performance of the lithium-ion secondary battery; when the thickness of the second coating is too thick, the Li-metal-Si phase formed during the first charge and discharge process will consume part of the lithium ions, resulting in a large energy density loss in the lithium-ion secondary battery. When the thickness of the first coating is within the above range, the negative electrode sheet has better processing performance, which is conducive to the winding and assembly of the battery cell.

[0053] It should be noted that the average volume distribution particle size Dv50 refers to the particle size corresponding to when the cumulative volume distribution percentage of the silicon-based material and the metal particles reaches 50%. In the present application, the volume average particle size Dv50 of the negative electrode active material can be measured by laser diffraction particle size analysis. For example, with reference to the standard GB / T 19077-2016, a laser particle size analyzer (such as Malvern Master Size 3000) is used for measurement.

[0054] In addition, the secondary battery, battery module, battery pack, and electric device of the present application will be described below with reference to the drawings as appropriate.

[0055] In one embodiment of the present application, a secondary battery is provided.

[0056] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0057] [Positive electrode]

[0058] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0059] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0060] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may 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 a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0061] In some embodiments, the positive electrode active material may adopt a positive electrode active material for a battery that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides 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, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05O2) and its modified compounds, etc. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0062] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0063] In some embodiments, the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0064] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0065] [Electrolytes]

[0066] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0067] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0068] In some embodiments, the electrolyte salt can 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 difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0069] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0070] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0071] [Isolation film]

[0072] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0073] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0074] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0075] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0076] In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0077] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square or any other shape. Figure 3 The secondary battery 5 is a square structure as an example.

[0078] In some embodiments, reference Figure 4, the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0079] In some embodiments, secondary batteries may be assembled into a battery module. The number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0080] Figure 5 4 is an example of a battery module. Figure 5 In the battery module 4, the plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.

[0081] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0082] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0083] Figure 6 and Figure 7 1 is a battery pack 1 as an example. Figure 6 and Figure 7 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0084] In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include 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., but are not limited thereto.

[0085] As the electrical device, a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.

[0086] Figure 8 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the high power and high energy density requirements of the power consumption device for the secondary battery, a battery pack or a battery module can be used.

[0087] Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.

[0088] Example

[0089] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0090] Example 1

[0091] First coating: Si, conductive agent carbon nanotube CNT, binder lithium polyacrylate Li-PAA, and dispersant lithium carboxymethyl cellulose Li-CMC were mixed in a mass ratio of 90:2:5:3 and added into deionized water, and stirred evenly to obtain slurry A. The obtained slurry A was coated at a coating weight of CW = 0.16 g / 1540.25 mm 2 The first coating is obtained by coating on the copper foil current collector, drying and cold pressing.

[0092] Second coating: Mix metal particles Mg, conductive agent Super P, and binder PVDF in a mass ratio of 5:2:3 and add them to N-methylpyrrolidone, stir to form slurry B, apply the obtained slurry B on the first surface, and dry to obtain the negative electrode sheet.

[0093] Among them, Dv50 of Si = 2.5 μm, Dv50 of metal particles Mg = 200 nm, and metal particles: silicon-based material = 0.05:1 (wt:wt).

[0094] Example 2

[0095] Except that the silicon-based material is replaced by SiO, and the Dv50 of SiO is 3 μm, the other conditions are the same as those in Example 1.

[0096] Example 3

[0097] Except that the silicon-based material is replaced by a mixture of Si and graphite, wherein the mass proportion of Si is 40% and the weight proportion of graphite is 60% relative to the total weight of the mixture of Si and graphite, the other conditions are the same as those in Example 1.

[0098] Example 4

[0099] Except that the metal particles are replaced with Al and the Dv50 of the metal particles Al is 300 nm, the other conditions are the same as those in Example 1.

[0100] Example 5

[0101] Except that the ratio of metal particles to silicon-based material is 0.03:1 (wt:wt), other conditions are the same as those in Example 1.

[0102] Example 6

[0103] Except for the ratio of metal particles to silicon-based material = 0.1:1 (wt:wt), other conditions are the same as those in Example 1.

[0104] Comparative Example 1

[0105] Si, conductive agent carbon nanotube CNT, binder lithium polyacrylate Li-PAA, and dispersant lithium carboxymethyl cellulose Li-CMC were mixed in a mass ratio of 90:2:5:3 and added into deionized water, and stirred evenly to obtain slurry A. The obtained slurry A was coated with a coating weight of CW=0.16g / 1540.25mm 2 The coating is applied on the copper foil current collector, dried and cold pressed to obtain the coating.

[0106] Comparative Example 2

[0107] Except that the metal particles Mg are replaced by metal particles Zn, other conditions are the same as those in Example 1.

[0108] Comparative Example 3

[0109] Except that the metal particles Mg are replaced by metal particles Cr, other conditions are the same as those in Example 1.

[0110] Comparative Example 4

[0111] Except that the metal particles Mg are replaced by metal particles Ti, other conditions are the same as those in Example 1.

[0112] The relevant parameters of the negative electrode sheets of the above-mentioned Examples 1 to 6 and Comparative Examples 1 to 4 are shown in the following Table 1.

[0113] Table 1: Parameter results of Examples 1 to 6 and Comparative Examples 1 to 4

[0114]

[0115]

[0116] In addition, the negative electrode sheets obtained in the above Examples 1 to 6 and Comparative Examples 1 to 4 were respectively prepared into button-type batteries as shown below, and performance tests were performed. The test results are shown in Table 2 below.

[0117] (1) Preparation of button cells

[0118] The negative electrode sheets in the above-mentioned embodiments and comparative examples are used, and the metal lithium sheet is used as the counter electrode; a polyethylene (PE) film is used as an isolation membrane; ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L; the above-mentioned parts are assembled into a CR2430 button battery in an argon-protected glove box.

[0119] (3) Initial gram capacity and cycle performance test of button battery

[0120] Each button cell prepared as above was cycled at 0.005-3V, first discharged at 0.1C to 0.005V, the capacity at this time is the lithium insertion capacity, recorded as C0; after standing for 5 minutes, charged at 0.1C to 3V, the capacity at this time is the initial lithium removal capacity, recorded as D0, and the first efficiency is D0 / C0*100%. The tested lithium removal capacity value (i.e. C0) is divided by the mass of the negative electrode active material in the button cell, which is the initial gram capacity of the negative electrode active material. The gram capacity after 250 cycles can be calculated using the lithium removal capacity after the cycle in the same way, and the capacity retention rate is obtained by using (gram capacity after cycle / initial gram capacity*100%).

[0121] Table 2: Performance test results of Examples 1 to 6 and Comparative Examples 1 to 4

[0122]

[0123]

[0124] According to the above results, the negative electrode plates in Examples 1 to 6 are all provided with a second coating layer containing metal particles Mg, and the silicon-based material in the negative electrode plates, the metal particles and the embedded lithium ions form a Li-metal-Si phase during the cycle, which can stably exist on the surface of the silicon-based material particles, inhibit the reactivity of the silicon-based material particle surface, and reduce the side reactions with the electrolyte, thereby achieving good results in improving the cycle performance of the silicon-based material. In addition, the powderization of the silicon-based material is also inhibited.

[0125] In contrast, Comparative Examples 1 to 4 have not achieved effective improvement in cycle performance. The negative electrode plate in Comparative Example 1 is not provided with a second coating containing metal particles, and the surface of the silicon-based material particles still has a high reactivity, and a side reaction occurs with the electrolyte to form an unstable SEI film, thereby affecting the cycle performance of the silicon-based material. The metal particles Zn in Comparative Example 2, the metal particles Cr in Comparative Example 3, and the metal particles Ti in Comparative Example 4 not only fail to form a stable Li-metal-Si phase on the surface of the silicon-based material particles to avoid side reactions between the silicon-based material and the electrolyte, but also consume a large amount of active lithium ions during the charge and discharge process, thus failing to effectively improve the cycle performance and first coulomb efficiency of the silicon-based material.

[0126] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A negative electrode plate, characterized in that: The coating layer comprises a coating layer and a current collector, wherein the coating layer is located on at least one surface of the current collector, the coating layer comprises a first coating layer and a second coating layer, the first coating layer is coated on the surface of the current collector, and the second coating layer is coated on the surface of the first coating layer. The first coating layer includes a silicon-based material, and the second coating layer includes one or more selected from Mg, Ca, and Al as metal particles.

2. The negative electrode sheet according to claim 1, characterized in that: The silicon-based material is SiO x (0≤x<2), Si, or a mixture of Si and graphite.

3. The negative electrode sheet according to claim 2, characterized in that: In the mixture of Si and graphite, relative to the total weight of the mixture of Si and graphite, the weight ratio of Si is 40-70%, and the weight ratio of graphite is 30-60%.

4. The negative electrode sheet according to claim 1 or 2, characterized in that: In the second coating, the metal particles have a Dv50 of 50 to 500 nm, and The weight ratio of the metal particles is 40-80% relative to the total weight of the second coating layer.

5. The negative electrode sheet according to claim 1, characterized in that: In the first coating, the Dv50 of the silicon-based material is 1.5 to 5 μm, and Relative to the total weight of the first coating layer, the weight proportion of the silicon-based material is 90-97%.

6. The negative electrode sheet according to claim 1, characterized in that: The weight ratio of the metal particles to the silicon-based material is 0.03 to 0.1:

1.

7. The negative electrode sheet according to claim 1, characterized in that: The coating weight of the first coating layer CW=0.14-0.2 g / 1540.25 mm 2 .

8. The negative electrode sheet according to claim 1, characterized in that: The thickness of the first coating layer is 30-50 μm, and the thickness of the second coating layer is 500-2000 nm.

9. A secondary battery, characterized in that: The invention comprises the negative electrode sheet according to any one of claims 1 to 8.

10. A battery module, characterized in that: A secondary battery comprising the secondary battery according to claim 9.

11. A battery pack, characterized in that: A battery module comprising the battery module according to claim 10.

12. An electrical device, characterized in that: The battery comprises at least one selected from the secondary battery of claim 9, the battery module of claim 10, or the battery pack of claim 11.

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