Negative plate, battery and negative plate manufacturing method

Abstract

The invention discloses a negative plate, a battery and a manufacturing method of the negative plate. The negative plate comprises a foil; a first active material layer; a second active material layer; the foil material, the first active material layer, the blocking piece and the second active material layer are sequentially arranged in a stacked mode in the thickness direction of the foil material, and the blocking piece is used for blocking expansion of the first active material layer. The negative plate disclosed by the invention can have relatively good performance.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a negative electrode sheet, a battery and a method for manufacturing the negative electrode sheet. Background Art

[0002] In the related art, the negative electrode sheet includes a foil and an active material layer. Specifically, the foil can be a copper foil, and the active material layer includes graphite, which is coated on the copper foil to form a negative electrode sheet. In order to further improve the energy density of the battery, silicon material can be added to the active material layer of the negative electrode sheet. Specifically, the silicon material is coated on the foil, and then the graphite is coated on the silicon material. Among them, after the active material layer formed by the silicon material and graphite is coated on the copper foil, although the energy density of the battery can be improved, the silicon will undergo a significant volume change during the insertion and extraction of lithium ions, which will result in poor performance of the negative electrode sheet. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a negative electrode sheet that can have better performance.

[0004] The invention also provides a battery.

[0005] The invention also provides a method for manufacturing a negative electrode sheet.

[0006] The negative electrode sheet according to the first embodiment of the present invention comprises: Foil; a first active material layer; a second active material layer; The barrier is configured such that the foil, the first active material layer, the barrier and the second active material layer are sequentially stacked along the thickness direction of the foil, wherein the barrier is used to prevent the first active material layer from expanding.

[0007] The negative electrode sheet according to the embodiment of the present invention has at least the following beneficial effects: the barrier is arranged between the first active material layer and the second active material layer, wherein the barrier is used to prevent the first active material layer from expanding. In the prior art, the silicon material is coated on the foil material, and the graphite material is coated on the silicon material. The silicon material will expand greatly, resulting in poor performance of the negative electrode sheet. In the present application, the barrier can effectively prevent the first active material layer from expanding, thereby effectively improving the performance of the negative electrode sheet. Specifically, the negative electrode sheet can have better performance.

[0008] According to the negative electrode sheet of some embodiments of the present invention, the blocking member is a mesh structure.

[0009] According to the negative electrode sheets of some embodiments of the present invention, the blocking member is provided with a plurality of through holes, and the aperture of the through holes is L, 100 nm≤L≤180 nm.

[0010] According to the negative electrode sheets of some embodiments of the present invention, the blocking member is provided with a plurality of through holes, and the porosity of the blocking member is W, 60%≤W≤90%.

[0011] According to the negative electrode sheet of some embodiments of the present invention, the thickness of the barrier is A, 45um≤A≤90um.

[0012] According to some embodiments of the negative electrode sheet of the present invention, the foil includes two blank areas and a coated area, the two blank areas are respectively connected to the two ends of the coated area, the first active material layer is connected to the coated area, the blocking member includes a main body and two protruding parts, the two protruding parts are respectively connected to the two ends of the main body, and the two protruding parts protrude relative to the main body in the same direction, the two protruding parts are respectively welded to the two blank areas, and the main body covers the first active material layer.

[0013] In the negative electrode sheet according to some embodiments of the present invention, the main body is a mesh structure.

[0014] According to the negative electrode sheet of some embodiments of the present invention, the first active material layer includes a plurality of sub-active material layers, and a plurality of the blocking members are provided, and along the thickness direction of the foil, the plurality of sub-active material layers and the plurality of the blocking members are alternately arranged.

[0015] The battery according to the second aspect of the present invention comprises the negative electrode sheet described in any one of the first aspect of the present invention.

[0016] The battery according to the embodiment of the present invention has at least the following beneficial effects: the barrier is arranged between the first active material layer and the second active material layer, wherein the barrier is used to prevent the first active material layer from expanding. In the prior art, the silicon material is coated on the foil material, and the graphite material is coated on the silicon material. The silicon material will expand greatly, resulting in poor performance of the negative electrode sheet. In the present application, the barrier can effectively prevent the first active material layer from expanding, thereby effectively improving the performance of the negative electrode sheet. Specifically, the negative electrode sheet can have better performance. Furthermore, the battery with the negative electrode sheet has better performance.

[0017] The method for manufacturing a negative electrode sheet according to the third aspect of the present invention comprises the following steps: Producing a foil; coating a first active material layer on the foil; placing and fixing a blocking member on the first active material layer; A second active material layer is coated on the barrier.

[0018] The negative electrode sheet manufacturing method according to the embodiment of the present invention has at least the following beneficial effects: In the prior art, the silicon material is coated on the foil material, and the graphite material is coated on the silicon material, and the silicon material will expand greatly, resulting in poor performance of the negative electrode sheet. In the present application, the blocking member can be arranged between the first active material layer and the second active material layer, wherein the blocking member is used to block the expansion of the first active material layer, thereby effectively improving the performance of the negative electrode sheet. Specifically, the negative electrode sheet manufactured by the negative electrode sheet manufacturing method can have better performance.

[0019] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 is a schematic diagram of a negative electrode sheet according to a first embodiment of the present invention; Figure 2 Schematic diagram of a blocking member in a negative electrode sheet of some embodiments of the present invention; Figure 3 is a schematic diagram of a negative electrode sheet according to a second embodiment of the present invention; Figure 4 FIG. 4 is a schematic diagram of a negative electrode sheet according to a third embodiment of the present invention.

[0021] Reference numerals: The negative electrode sheet 100 , the foil material 200 , the blank area 210 , the coating area 220 , the first active material layer 300 , the sub-active material layer 310 , the second active material layer 400 , the blocking member 500 , the through hole 510 , the main body 520 , and the protrusion 530 . DETAILED DESCRIPTION

[0022] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0023] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0024] In the description of the present invention, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0025] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0026] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0027] The battery can be a lithium ion battery, a sodium ion battery, a sodium lithium ion battery, a lithium metal battery, a sodium metal battery, a lithium sulfur battery, a magnesium ion battery, a nickel hydrogen battery, a nickel cadmium battery, a lead storage battery, etc., which is not limited in the embodiments of the present application.

[0028] Batteries generally include cells. Cells include positive electrodes, negative electrodes, and separators. During the battery charging and discharging process, active ions (such as lithium ions) are inserted and removed between the positive and negative electrodes. The separator is set between the positive and negative electrodes to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through.

[0029] In some embodiments, the positive electrode may be a positive electrode sheet, and the positive electrode sheet may include a positive electrode current collector and a positive electrode active material disposed on at least one surface of the positive electrode current collector.

[0030] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0031] As an example, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel or titanium, etc. may be used. The composite current collector may include a polymer material base layer and a metal layer. 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, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0032] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates, lithium transition metal oxides, 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-containing phosphates 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. 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 NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2)) and at least one of its modified compounds, etc.

[0033] In some embodiments, the positive electrode may be a foamed metal. The foamed metal may be a nickel foam, a copper foam, an aluminum foam, an alloy foam, etc. When the foamed metal is used as the positive electrode, the positive electrode active material may not be provided on the surface of the foamed metal, but of course, the positive electrode active material may also be provided. As an example, a lithium source material, potassium metal or sodium metal may also be filled or / and deposited in the foamed metal, and the lithium source material is lithium metal and / or a lithium-rich material.

[0034] In some embodiments, the negative electrode may be a negative electrode sheet, and the negative electrode sheet may include a negative electrode current collector.

[0035] As an example, the negative electrode current collector may be a metal foil, a foamed metal or a composite current collector. For example, as the metal foil, aluminum or stainless steel treated with silver, stainless steel, copper, aluminum, nickel, carbon electrode, nickel or titanium, etc. may be used. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, etc. The composite current collector may include a polymer material base and a metal layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0036] As an example, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector.

[0037] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0038] As an example, the negative electrode active material may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0039] In some embodiments, the material of the positive electrode current collector may be aluminum, and the material of the negative electrode current collector may be copper.

[0040] In some embodiments, the battery cell further includes a separator, which is disposed between the positive electrode and the negative electrode.

[0041] In some embodiments, the separator is a separator membrane. There are many types of separator membranes, and any known porous separator membrane with good chemical stability and mechanical stability can be selected.

[0042] As an example, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different. The separator may be a separate component located between the positive and negative electrodes, or may be attached to the surface of the positive and negative electrodes.

[0043] In some embodiments, the separator is a solid electrolyte, which is disposed between the positive electrode and the negative electrode and serves to transmit ions and isolate the positive and negative electrodes.

[0044] In some embodiments, the battery further comprises an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. The electrolyte may be liquid, gel or solid. The liquid electrolyte comprises an electrolyte salt and a solvent.

[0045] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0046] In some embodiments, the solvent may include 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, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone. The solvent may also be an ether solvent. The ether solvent 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, methyltetrahydrofuran, diphenyl ether and crown ether.

[0047] Among them, the gel electrolyte includes a skeleton network with a polymer as the electrolyte, combined with an ionic liquid-lithium salt.

[0048] Among them, solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0049] As an example, the polymer solid electrolyte may be polyether (polyethylene oxide), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, a single ion polymer, polyionic liquid-lithium salt, cellulose, and the like.

[0050] As an example, the inorganic solid electrolyte may include an oxide solid electrolyte (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON film), a sulfide solid electrolyte (crystalline lithium superion conductor (lithium germanium phosphosulfide, silver germanium sulfide), amorphous sulfide) and one or more of a halide solid electrolyte, a nitride solid electrolyte and a hydride solid electrolyte.

[0051] As an example, the composite solid electrolyte is formed by adding an inorganic solid electrolyte filler to a polymer solid electrolyte.

[0052] In some embodiments, the battery cell is a wound structure, wherein the positive electrode sheet and the negative electrode sheet are wound into a wound structure.

[0053] In some embodiments, the battery cell has a stacked structure.

[0054] As an example, a plurality of positive electrode sheets and a plurality of negative electrode sheets may be provided respectively, and the plurality of positive electrode sheets and the plurality of negative electrode sheets may be alternately stacked.

[0055] As an example, a plurality of positive electrode sheets may be provided, and the negative electrode sheet may be folded to form a plurality of stacked folded segments, with a positive electrode sheet being sandwiched between adjacent folded segments.

[0056] As an example, both the positive electrode sheet and the negative electrode sheet are folded to form a plurality of folded sections that are stacked.

[0057] As an example, a plurality of separators may be provided, each of which is provided between any adjacent positive electrode sheets or negative electrode sheets.

[0058] As an example, the separator may be disposed continuously, and may be disposed between any adjacent positive electrode sheets or negative electrode sheets by folding or winding.

[0059] In some embodiments, the shape of the battery cell can be cylindrical, flat, or polygonal.

[0060] In some embodiments, the battery cell is provided with a tab, which can lead current out of the battery cell. The tab includes a positive tab and a negative tab.

[0061] In some embodiments, the battery may include a housing. The housing is used to encapsulate components such as the battery cell and the electrolyte. The housing may be a steel housing, an aluminum housing, a plastic housing (such as polypropylene), a composite metal housing (such as a copper-aluminum composite housing), or an aluminum-plastic film.

[0062] As an example, the battery may be a cylindrical battery, a prismatic battery, a soft-pack battery or a battery of other shapes. Prismatic batteries include but are not limited to square-shell batteries, blade-shaped batteries, and polygonal batteries. Polygonal batteries may be, for example, hexagonal batteries.

[0063] The battery mentioned in the embodiments of the present application refers to a single physical module including one or more batteries to provide higher voltage and capacity.

[0064] In some embodiments, the battery may be a battery module. When there are multiple batteries, the multiple batteries are arranged and fixed to form a battery module.

[0065] In some embodiments, the battery may be a battery pack, which includes a case and batteries, wherein the batteries or battery modules are accommodated in the case.

[0066] In some embodiments, the box body can be used as a part of the chassis structure of the vehicle. For example, part of the box body can become at least a part of the floor of the vehicle, or part of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0067] The embodiment of the present application provides an electric device using a battery as a power source, and the electric device may be, but is not limited to, a mobile phone, a tablet, a laptop, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft, etc. Among them, the electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy, etc., and the spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft, etc.

[0068] In the related art, the negative electrode sheet includes a foil and an active material layer. Specifically, the foil can be a copper foil, and the active material layer includes graphite, and the graphite is coated on the copper foil to form a negative electrode sheet. In order to further improve the energy density of the battery, silicon material can be added to the active material layer of the negative electrode sheet. Specifically, the silicon material is coated on the foil, and then the graphite is coated on the silicon material. Among them, after the active material layer formed by the silicon material and the graphite is coated on the copper foil, although the energy density of the battery can be improved, the silicon will undergo a significant volume change during the insertion and extraction of lithium ions, which will result in poor performance of the negative electrode sheet. To this end, the present application proposes a negative electrode sheet.

[0069] Please refer to Figure 1 to Figure 2In some embodiments, the negative electrode sheet 100 includes: a foil 200, a first active material layer 300, a second active material layer 400 and a barrier 500. The foil 200 may be a copper foil, which is cheap and can reduce the manufacturing cost of the negative electrode sheet 100. The first active material layer 300 may be a silicon material, and the second active material layer 400 may be graphite. The binder content of the second active material layer 400 is greater than the binder content of the first active material layer 300. Along the thickness direction of the foil 200, the foil 200, the first active material layer 300, the barrier 500 and the second active material layer 400 are stacked in sequence. That is, the two sides of the first active material layer 300 are respectively connected to the foil 200 and the barrier 500, and the two sides of the barrier 500 are respectively connected to the first active material layer 300 and the second active material layer 400. Among them, the barrier 500 is used to prevent the first active material layer 300 from expanding. Specifically, the barrier 500 is disposed between the first active material layer 300 and the second active material layer 400, wherein the barrier 500 is used to prevent the first active material layer 300 from expanding. In the prior art, the silicon material is coated on the foil 200, and the graphite material is coated on the silicon material. The silicon material will expand greatly, resulting in poor performance of the negative electrode sheet 100. In the present application, the barrier 500 can effectively prevent the first active material layer 300 from expanding, thereby effectively improving the performance of the negative electrode sheet 100. Specifically, the negative electrode sheet 100 can have better performance.

[0070] Furthermore, the barrier 500 may be a metal piece, or a sheet structure made of other conductive materials. Among them, the other conductive material may be a conductive inorganic material. When the barrier 500 is a sheet structure, such as a copper sheet, the first active material layer 300 expands, and the barrier 500 can effectively block the expansion of the first active material layer 300. In addition, in addition to being a sheet structure, the barrier 500 may also be a mesh structure. Therefore, please refer to Figure 2 In some embodiments, the blocking member 500 is a mesh structure. Specifically, the mesh structure refers to a plurality of through holes 510 provided on the blocking member 500. When the blocking member 500 is made of metal, such as copper, the blocking member 500 may be a copper mesh. When the first active material layer 300 expands, the copper mesh can prevent the silicon particles from expanding too much, thereby effectively improving the expansion degree of the silicon-carbon negative electrode and effectively preventing the negative electrode sheet 100 from expanding too much. At the same time, the presence of the second active material layer 400 can ensure that the silicon particles are always inside the graphite negative electrode, effectively preventing the silicon particles from losing electrical contact due to expansion and pulverization, which can effectively improve the performance of the negative electrode sheet 100.

[0071] Further, in some embodiments, the blocking member 500 is a mesh structure, and the blocking member 500 has a first state and a second state. It is conceivable that when the first active material layer 300 is not expanded, the blocking member 500 is located between the first active material layer 300 and the second active material layer 400. After the first active material layer 300 expands, the blocking member 500 is designed as a mesh structure, which may cause at least a portion of the blocking member 500 to be pushed into the second active material layer 400 by the first active material layer 300. That is, when the blocking member 500 is in the first state, the blocking member 500 is located between the first active material layer 300 and the second active material layer 400, and when the blocking member 500 is in the second state, at least a portion of the blocking member 500 is located in the second active material layer 400.

[0072] Further, the manufacturing method of the negative electrode sheet 100 may be to coat the first active material slurry on the foil 200 according to the technical requirements to form the first active material layer 300, and then fix the copper mesh on the first active material layer 300 by using the dispensing technology. After the copper mesh is fixed, the second active material is further coated on the surface of the first active material layer to form the second active material layer 400. After the coating is completed, the negative electrode sheet 100 is further compacted by rolling to ensure that the flatness of the negative electrode sheet 100 is good. Among them, the material of the first active material layer 300 is silicon carbon. The material of the second active material layer 400 may be graphite, and the material of graphite includes but is not limited to graphene, carbon fiber, graphite particles, etc. The material of the conductive agent includes but is not limited to one of conductive carbon black, acetylene black, and metal powder. The binder includes one of polyacrylic acid (PAA), lithium polyacrylate (PAA-Li), sodium polyacrylate (PAA-Na), polyvinyl alcohol (PVA), and polyacrylonitrile (PAN). The first active material layer 300 has a silicon carbon content of 95% to 97%, a conductive agent content of 1% to 4%, and a binder content of 0.2% to 1%. The second active material layer 400 has a graphite content of 92% to 94%, a conductive agent content of 1% to 4%, and a binder content of 2% to 6%.

[0073] The beneficial effects of the negative electrode sheet 100 in the present application are illustrated below through experiments.

[0074] Embodiment 1: The method for preparing the negative electrode sheet 100 comprises the following steps: S1: preparing the first active material layer 300 according to 96% silicon-carbon negative electrode, 3% conductive carbon black, and 1% polyvinyl alcohol; S2: preparing the second active material layer 400 according to 92% graphene, 3% conductive carbon black, and 5% polyvinyl alcohol; S3: prepare a copper mesh, the thickness of the copper mesh is 50 μm; S4: coating the first active material layer 300, the copper mesh and the second active material layer 400 on the foil 200 respectively; S5: rolling the sprayed negative electrode sheet 100, wherein the thickness of the negative electrode sheet 100 after rolling is 400 μm; S6: Make soft-pack batteries, inject liquid and form batteries.

[0075] Embodiment 2: S1: preparing the first active material layer 300 according to 97% silicon-carbon negative electrode, 2% conductive carbon black, and 1% polyvinyl alcohol; S2: preparing the second active material layer 400 according to 93% graphene, 2% conductive carbon black, and 5% polyvinyl alcohol; S3: prepare a copper mesh, the thickness of the copper mesh is 50 μm; S4: coating the first active material layer 300, the copper mesh and the second active material layer 400 on the foil 200 respectively; S5: rolling the sprayed negative electrode sheet 100, wherein the thickness of the negative electrode sheet 100 after rolling is 450 μm; S6: Make soft-pack batteries, inject liquid and form batteries.

[0076] Embodiment 3: S1: preparing the first active material layer 300 according to 96% silicon-carbon negative electrode, 3% conductive carbon black, and 1% polyvinyl alcohol; S2: preparing the second active material layer 400 according to 92% graphene, 3% conductive carbon black, and 5% polyvinyl alcohol; S3: coating the first active material layer 300 and the second active material layer 400 on the foil 200 respectively; S4: rolling the sprayed negative electrode sheet 100, wherein the thickness of the negative electrode sheet 100 after rolling is 400 μm; S5: Make soft-pack batteries, inject liquid into the batteries, and perform formation.

[0077] Specifically, after the negative electrode sheet 100 is made into a battery, the battery is tested, wherein the first discharge capacity test refers to: performing a constant current discharge test on the battery at room temperature, with a charge and discharge interval of 1.0 to 3V and a current density range of 400 to 5000 mA / g.

[0078] The capacity retention rate test refers to the ratio between the discharge capacity after 500 cycles and the initial discharge capacity when the batteries of each embodiment and comparative example are tested at room temperature and operated at a current density of 0.2C. Cycle capacity retention rate = (500th cycle discharge capacity / first cycle discharge capacity)*100%.

[0079] Thermal shock performance refers to: under 25℃ environmental conditions, discharge to 3.0V with a given current of 0.2C; leave for 5 minutes; charge to 4.45V with a charging current of 0.2C. When the battery voltage reaches 4.45V, change to 4.45V constant voltage charging until the charging current is less than or equal to the given cut-off current of 0.05C; after leaving for 1h, put the battery into an oven, and the oven temperature is increased to 135±2℃ at a rate of 5±2℃ / min, and kept for 30 minutes before stopping. The judgment standard is that the battery does not catch fire or explode.

[0080] The 60℃ high temperature storage test means: put the battery at room temperature and charge and discharge it once at 0.5C (4.45V~3.0V), record the discharge capacity C0 before storage, then charge the battery to 4.45V full power state with constant current and constant voltage, use PPG battery thickness gauge (500g) to test the thickness d1 of the battery before high temperature storage, put the battery in a 60℃ constant temperature box for 14 days, take out the battery after storage to test the thermal thickness d2 of the battery, and calculate the thickness expansion rate of the battery after 60℃ storage for 14 days; after the battery is cooled at room temperature for 24h, discharge the battery to 3.0V at 0.5C again, and then charge to 4.45V at 0.5C constant current and constant voltage, record the discharge capacity C1 and charge capacity C2 after storage, and calculate the capacity remaining rate and recovery rate of the battery after 60℃ storage for 14 days, the calculation formula is as follows: Thickness expansion rate after 60℃ storage for 14 days = (d2-d1) / d1*100%. The experimental results are shown in the following table.

[0081]

[0082] It can be seen from the above table that Example 1 and Example 2 adopt the setting of the blocking member 500. Compared with Example 3 which does not adopt the setting of the blocking member 500, the battery made by adopting the blocking member 500 has a smaller expansion rate, a higher probability of passing through thermal shock, a higher capacity retention rate, and a higher first discharge specific capacity.

[0083] For further information, please refer to Figure 2 In some embodiments, the barrier 500 is provided with a plurality of through holes 510, and the aperture of the through hole 510 is L, 100nm≤L≤180nm. The aperture of the through hole 510 may be 100nm, 110nm, 120nm, 150nm or 180nm. When the aperture of the through hole 510 is less than 100nm, due to the small aperture of the through hole 510, the silicon material particles may not be able to pass through, resulting in a greater stress on the barrier 500, and the barrier 500 may not be able to effectively prevent the first active material layer 300 from expanding. When the aperture of the through hole 510 is greater than 180nm, due to the excessive aperture of the through hole 510, most of the silicon material particles will pass through the through hole 510, and the expansion degree of the negative electrode sheet 100 will be too large.

[0084] Further, in some embodiments, the blocking member 500 is provided with a plurality of through holes 510, and the porosity of the blocking member 500 is W, 60%≤W≤90%. Specifically, the porosity of the blocking member 500 may be 60%, 70%, 80% or 90%. Among them, the porosity reflects the amount and distribution of pores in the blocking member 500. That is, the greater the porosity. The more through holes 510 are provided on the blocking member 500, the smaller the gap between two adjacent through holes 510. When the porosity of the blocking member 500 is greater than 90%, there are more through holes 510 provided on the blocking member 500, which may cause the blocking member 500 to be difficult to manufacture when the through holes 510 are provided, resulting in excessively high costs of the blocking member 500. When the porosity of the blocking member 500 is less than 60%, the number of through holes 510 provided on the blocking member 500 is small, which may result in that the blocking member 500 is not effective in limiting the expansion of the silicon material. The silicon material may lift up the blocking member 500, resulting in a lower flatness of the negative electrode sheet 100.

[0085] Further, in some embodiments, the thickness of the barrier 500 is A, 45um≤A≤90um. Specifically, the thickness of the barrier 500 may be 45um, 50um, 60um, 80um or 90um. When the thickness of the barrier 500 is relatively large, since the function of the barrier 500 is mainly to limit the expansion of the silicon layer, the greater the thickness of the barrier 500, the less active material the negative electrode sheet 100 can have under a fixed size, thereby making the energy density of the negative electrode sheet 100 lower, and therefore the thickness of the barrier 500 cannot be greater than 90um. When the thickness of the barrier 500 is less than 45um, due to the small thickness of the barrier 500, on the one hand, it will increase the difficulty of punching holes in the barrier 500, and on the other hand, due to the small strength of the barrier 500, the barrier 500 will have a poor effect in limiting the expansion of the silicon material.

[0086] Further, the following describes a specific method for effectively limiting the expansion of the silicon material by the blocking member 500. Figure 3In some embodiments, the foil 200 includes two blank areas 210 and a coating area 220. The two blank areas 210 are respectively connected to the two ends of the coating area 220. Specifically, along the length direction of the foil 200, the blank area 210, the coating area 220 and the blank area 210 are arranged in sequence. The first active material layer 300 is connected to the coating area 220, and the blocking member 500 includes a main body 520 and two protrusions 530, the two protrusions 530 are respectively connected to the two ends of the main body 520, and the two protrusions 530 protrude relative to the main body 520 in the same direction. The two protrusions 530 are respectively welded to the two blank areas 210, and the main body 520 covers the first active material layer 300. Specifically, the two protrusions 530 are respectively welded to the blank area 210, which can fix the blocking member 500 on the foil 200. After the main body 520 covers the first active material layer 300, when the silicon material expands, the silicon material will abut the main body 520, and the protrusion 530 can pull the main body 520, and the main body 520 can effectively abut the silicon material, thereby preventing the silicon material from expanding.

[0087] For further information, please refer to Figure 3 In some embodiments, the main body 520 is a mesh structure. Specifically, the main body 520 is set to a mesh structure, and the mesh structure refers to a plurality of through holes 510 provided on the main body 520. When the blocking member 500 is made of metal, such as copper, the main body 520 may be a copper mesh. When the first active material layer 300 expands, the copper mesh can prevent the silicon particles from expanding too much, thereby effectively improving the expansion degree of the silicon-carbon negative electrode and effectively preventing the negative electrode sheet 100 from expanding too much. At the same time, the presence of the second active material layer 400 can ensure that the silicon particles are always inside the graphite negative electrode, effectively preventing the silicon particles from losing electrical contact due to expansion and pulverization, which can effectively improve the performance of the negative electrode sheet 100.

[0088] For further information, please refer to Figure 4In some embodiments, the first active material layer 300 includes a plurality of sub-active material layers 310, and a plurality of blocking members 500 are provided. Along the thickness direction of the foil 200, the plurality of sub-active material layers 310 and the plurality of blocking members 500 are alternately arranged. For example, taking the case where the first active material layer 300 includes two sub-active material layers 310 and two blocking members 500 are provided as an example, along the thickness direction of the foil 200, the plurality of sub-active material layers 310 and the plurality of blocking members 500 are alternately arranged as follows: sub-active material layer 310-blocking member 500-sub-active material layer 310-blocking member 500. In the above arrangement, the first active material layer 300 can be layered, and then the blocking member 500 can be arranged between two adjacent sub-active material layers 310. After layering, the expansion degree of each sub-active material layer 310 is low, and the blocking member 500 can effectively limit it, thereby further improving the performance of the negative electrode sheet 100. That is, the arrangement of the plurality of blocking members 500 can improve the effect of limiting the expansion of the silicon material.

[0089] In some embodiments, the battery includes the negative electrode sheet 100 of any one of the above embodiments. Specifically, the barrier 500 is disposed between the first active material layer 300 and the second active material layer 400, wherein the barrier 500 is used to prevent the first active material layer 300 from expanding. In the prior art, the silicon material is coated on the foil 200, and the graphite material is coated on the silicon material. The silicon material will expand greatly, resulting in poor performance of the negative electrode sheet 100. In the present application, the barrier 500 can effectively prevent the first active material layer 300 from expanding, thereby effectively improving the performance of the negative electrode sheet 100. Specifically, the negative electrode sheet 100 can have better performance. Further, the battery having the negative electrode sheet 100 has better performance.

[0090] In some embodiments, the method for manufacturing the negative electrode sheet 100 includes the following steps: S100, preparing foil 200; S200, coating a first active material layer 300 on the foil 200; S300, placing and fixing a barrier 500 on the first active material layer 300; S400 : coating the second active material layer 400 on the blocking member 500 .

[0091] Specifically, in the prior art, the silicon material is coated on the foil 200, and the graphite material is coated on the silicon material, and the silicon material will expand greatly, resulting in poor performance of the negative electrode sheet 100. In the present application, the blocking member 500 can be arranged between the first active material layer 300 and the second active material layer 400, wherein the blocking member 500 is used to prevent the first active material layer 300 from expanding, thereby effectively improving the performance of the negative electrode sheet 100. Specifically, the negative electrode sheet 100 manufactured by the negative electrode sheet 100 manufacturing method can have good performance.

[0092] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A negative electrode sheet, characterized in that: include: Foil; a first active material layer; a second active material layer; The barrier is configured such that the foil, the first active material layer, the barrier and the second active material layer are sequentially stacked along the thickness direction of the foil, wherein the barrier is used to prevent the first active material layer from expanding.

2. The negative electrode sheet according to claim 1, characterized in that: The blocking member is a mesh structure.

3. The negative electrode sheet according to claim 2, characterized in that: The blocking member is provided with a plurality of through holes, and the aperture of the through holes is L, 100nm≤L≤180nm.

4. The negative electrode sheet according to claim 2, characterized in that: The blocking member is provided with a plurality of through holes, and the porosity of the blocking member is W, 60%≤W≤90%.

5. The negative electrode sheet according to claim 1, characterized in that: The thickness of the blocking member is A, 45um≤A≤90um.

6. The negative electrode sheet according to claim 1, characterized in that: The foil material includes two blank areas and a coated area, the two blank areas are respectively connected to the two ends of the coated area, the first active material layer is connected to the coated area, the blocking member includes a main body and two protruding parts, the two protruding parts are respectively connected to the two ends of the main body, and the two protruding parts protrude relative to the main body in the same direction, the two protruding parts are respectively welded to the two blank areas, and the main body covers the first active material layer.

7. The negative electrode sheet according to claim 6, characterized in that: The main body is a mesh structure.

8. The negative electrode sheet according to claim 1, characterized in that: The first active material layer includes a plurality of sub-active material layers, and a plurality of the blocking members are provided. Along the thickness direction of the foil material, the plurality of sub-active material layers and the plurality of blocking members are alternately arranged.

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

10. A method for manufacturing a negative electrode sheet, characterized in that: The following steps are involved: Producing a foil; coating a first active material layer on the foil; placing and fixing a blocking member on the first active material layer; A second active material layer is coated on the barrier.

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