Negative electrode plate, secondary battery, battery module, battery pack and power consuming device

Abstract

This application discloses a negative electrode plate, a secondary battery, a battery module, a battery pack, and a power consumption device. The negative electrode plate disclosed in this application includes a negative electrode current collector and an active material layer disposed on at least one surface of the negative electrode current collector, wherein the active material layer includes a first active material layer and a second active material layer disposed on the surface of the first active material layer, the first active material layer includes a first active material, and the second active material layer includes a second active material, and the active material layers satisfy α×CW2≦CW1, where α is an interlayer distance relative coefficient, JPEG2023552027000018.jpg1728 and 1≦α≦1.12. A secondary battery obtained by using the negative electrode plate of the present application can effectively improve both the rate performance and energy density of the battery.

Description

[Technical field]

[0001] The present application relates to the technical field of lithium batteries, and in particular to negative electrodes, secondary batteries, battery modules, battery packs and power consuming devices. [Background technology]

[0002] In recent years, the application range of lithium-ion batteries has become wider and wider. For example, lithium-ion batteries are widely used in many fields, such as energy storage power systems such as hydroelectric, thermal, wind, and solar power stations, electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and so on. Due to the wide range of applications of lithium-ion batteries, the overall performance requirements for current batteries are also becoming higher and higher, and more and more application scenarios require power batteries to have high energy density and good charge and discharge characteristics. As one of the most important components of lithium-ion batteries, the negative electrode design directly affects the performance of the battery, especially the charging-related characteristics of the battery. How to obtain a battery that balances energy density and dynamic performance by optimizing the negative electrode plate design is a common challenge currently faced in the industry. Summary of the Invention

[0003] The present application aims to provide a negative electrode plate to meet existing demand. The present application also provides a secondary battery, a battery module, a battery pack and a power consumption device using the negative electrode plate. The inventors of the present application have discovered that a battery negative electrode having both higher energy density and better charge / discharge kinetic performance can be obtained by adopting a bi-layer or multi-layer active material layer in the negative electrode and adjusting and controlling the relationship between the interlayer distance and the coating weight of each active material layer.

[0004] In order to achieve the above object, a first aspect of the present application provides a negative electrode plate including a negative electrode current collector and an active material layer disposed on at least one surface of the negative electrode current collector, the active material layer including a first active material layer and a second active material layer disposed on a surface of the first active material layer, the first active material layer including a first active material, the second active material layer including a second active material, and the active material layers satisfy α×CW2≦CW1, where JPEG0007674463000001.jpg19159d1: Interlayer distance corresponding to the d002 peak of the first active material, unit: nm; d2: the interlayer distance corresponding to the d002 peak of the second active material, unit: nm; CW1: mass of the first active material layer placed on the negative electrode current collector per unit area, unit: g / m 2 , CW2: Mass of the second active material layer placed on the negative electrode current collector per unit area, unit: g / m 2 .

[0005] Thus, by adopting a two-layer or multi-layer active material layer for the negative electrode and adjusting and controlling the relationship between the interlayer distance and the coating weight of each active material layer, a battery negative electrode having both higher energy density and better charge / discharge dynamic performance can be obtained. More specifically, the inventors of the present application found that by coating two active material layers on the current collector on the same side of the negative electrode plate, the interlayer distance of the active material of the second active material layer is greater than the interlayer distance of the active material of the first active material layer, and when lithium ions move from the positive electrode to the negative electrode, the interlayer distance of the surface layer material is large and the absorption impedance of lithium ions is low, so that the lithium ions are absorbed quickly into the surface active material, and the deposition of lithium ions on the surface of the negative electrode plate due to excessive charging speed can be avoided. The larger the interlayer distance of the negative electrode active material, the lower the capacity of the material, so the coating weight of the second active material becomes larger, and the impact on the capacity of the entire negative electrode plate becomes larger. In order to achieve both the capacity of the negative electrode plate and the performance of the charging window, the present application limits the coating weight of the second active material layer. The larger the interlayer distance of the active material of the second active material layer, the higher its charging ability and the lower its capacity. Accordingly, the smaller the coating weight, the better the charging level can be achieved. If the interlayer distance of the active material of the second active material layer is relatively small, its charging ability will be weak and its capacity will be large. At this time, in order to have good charging performance as a whole electrode plate, it is necessary to increase the ratio of the coating weight of the second active material layer to the coating weight of the whole electrode plate. The inventors of the present application unexpectedly discovered that by using a two-layer active material layer structure, the interlayer distance of the active material of the first active material layer is small, the capacity is large, and the electrode plate and the battery have a relatively high energy density, and the interlayer distance of the active material of the second active material layer is large, the lithium absorption impedance of the surface layer of the negative electrode plate is reduced, and the deposition of lithium ions on the surface of the negative electrode during high-rate charging is avoided, and the charging window of the battery is improved. Therefore, a battery negative electrode having an active material layer that satisfies the above relationship has both a high energy density and good charge / discharge dynamic performance.

[0006] JPEG0007674463000002.jpg14161

[0007] In order to achieve both the energy density and charging performance of the battery and avoid the influence of over-designing one performance causing the other to be insufficient, the inventors further limit the relationship between the coating weight and the interlayer distance of the first and second active material layers based on the actual test results. When this relationship is satisfied, the rate performance and energy density of the negative electrode plate and the battery can be improved.

[0008] JPEG0007674463000003.jpg20164Da 50 : volume average particle size of the first active material, unit: μm; Db 50 : Volume average particle size of the second active material, unit: μm.

[0009] The coating weight of the active material layer is adjusted according to the interlayer distance and particle size of each active material layer, thereby achieving both rapid charging performance and high energy density in the electrode plate and battery.

[0010] In any embodiment of the present application, the volume average particle size Da of the first active material 50 and the second JPEG0007674463000004.jpg18144

[0011] By defining the relative particle size relationship of the active materials in the two active material layers, it is possible to further improve the dynamic performance, which is advantageous in realizing processing performance when the coating weight of the second layer is low.

[0012] In any embodiment of the present application, the range of the interlayer distance d1 corresponding to the d002 peak of the first active material is 0.335 to 0.3362 nm, and the range of the interlayer distance d2 corresponding to the d002 peak of the second active material is 0.3356 to 0.38 nm.

[0013] In any embodiment of the present application, the first active material has a volume average particle size Da50 in the range of 8-20 μm, and the second active material has a volume average particle size Db50 in the range of 4-12 μm.

[0014] In any embodiment of the present application, the mass CW1 of the first active material layer disposed on the negative electrode current collector per unit area is in the range of 80 to 200 g / m 2 and the mass CW2 of the second active material layer placed on the negative electrode current collector per unit area is in the range of 10 to 110 g / m 2 It is.

[0015] In any embodiment of the present application, the first active material is a natural graphite or synthetic graphite material and / or the second active material is a synthetic graphite material.

[0016] In an optional embodiment, the first active layer and / or the second active layer comprises soft carbon or hard carbon.

[0017] According to a second aspect, the present application provides a secondary battery including the negative electrode plate of the first aspect of the present application.

[0018] According to a third aspect, the present application provides a battery module including the secondary battery of the second aspect of the present application.

[0019] According to a fourth aspect, the present application provides a battery pack including the secondary battery according to the second aspect of the present application and any one of the battery modules according to the third aspect.

[0020] According to a fifth aspect, the present application provides a power consuming device including at least one of the secondary battery according to the second aspect, the battery module according to the third aspect, and the battery pack according to the fourth aspect of the present application.

[0021] The battery module, battery pack and power consuming device of the present application include the secondary battery provided by the present application, and therefore have at least the same advantages as the secondary battery. [Brief description of the drawings]

[0022] In order to more clearly describe the technical solutions of the embodiments of the present application, the following briefly introduces the necessary drawings used in the embodiments of the present application. It is obvious that the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on the drawings without paying creative efforts. [Figure 1] FIG. 2 is a schematic diagram of one embodiment of a negative electrode plate of the present application. [Diagram 2] FIG. 1 is a schematic diagram of one embodiment of a secondary battery of the present application. [Diagram 3] FIG. 1 is a schematic diagram of one embodiment of a secondary battery of the present application. [Figure 4] FIG. 1 is a schematic diagram of one embodiment of a battery module of the present application. [Diagram 5] FIG. 1 is a schematic diagram of one embodiment of a battery pack of the present application. [Figure 6] FIG. 6 is an exploded view of FIG. 5. [Figure 7] 1 is a schematic diagram of an embodiment of a power consuming device powered by a secondary battery of the present application; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the negative electrode plate, secondary battery, battery module, battery pack, and power consumption device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and duplicated description of structures that are actually the same may be omitted. This is to avoid the following description becoming unnecessarily long and to allow those skilled in the art to easily understand. Note that the drawings and the following description are provided to allow those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0024] The "ranges" disclosed in this application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit that define the boundaries of the particular range. Such defined ranges may or may not include the end values, and may be combined in any way, i.e., any lower limit and any upper limit may be combined to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is also conceivable that they are understood as ranges of 60-110 and 80-120. It is noted that if the minimum range values ​​listed are 1 and 2, and the maximum range values ​​listed are 3, 4, and 5, then all of the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are conceivable. In this application, unless otherwise stated, the numerical range "a-b" is a shorthand expression representing all real number combinations between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed herein, with "0-5" being merely a shorthand notation for combinations of these numbers. Also, when a parameter is described as an integer ≧2, this is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0025] Unless otherwise stated, all the embodiments and optional embodiments in the present application may be combined with each other to form a new technical solution.

[0026] Unless otherwise stated, all technical features and optional technical features of the present application may be combined with each other to form a new technical solution.

[0027] Unless otherwise stated, all steps in the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b) 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 mentioned above may further include step (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), etc.

[0028] Unless otherwise specified, the terms "comprise" and "comprises" referred to in this application may be open ended or closed ended. For example, the terms "comprise" and "comprises" may further include or include other ingredients not listed, or may include or include only the listed ingredients.

[0029] In this application, unless otherwise stated, the term "or" is inclusive. For example, the term "A or B" means "A, B, or both A and B." More specifically, "A or B" is satisfied if A is true (or exists) and B is false (or does not exist), if A is false (or does not exist) but B is true (or exists), and if both A and B are true (or exist).

[0030] secondary battery A secondary battery is also called a rechargeable battery or a storage battery, and refers to a battery that can be used continuously by activating the active material through the application of current after the battery is discharged.

[0031] In general, a secondary battery includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. During the charge and discharge process of the secondary battery, active ions (e.g., lithium ions) shuttle between the positive electrode plate and the negative electrode plate to absorb and release. The separator is installed between the positive electrode plate and the negative electrode plate, and mainly serves to prevent short-circuiting between the positive and negative electrodes, while allowing the active ions to pass through. The electrolyte mainly serves to conduct the active ions between the positive electrode plate and the negative electrode plate.

[0032] [Negative electrode plate] As one of the most important components of lithium-ion batteries, the design of the anode directly affects the performance of the battery, especially the charge-response characteristics of the battery. How to achieve a battery that combines energy density and kinetic performance by optimizing the design of the anode plate is a common challenge faced by the current industry.

[0033] In order to solve the above problems, the inventors have conducted extensive research and provided a negative electrode plate. The negative electrode plate of the present application employs two or more active material layers, and adjusts and controls the relationship between the interlayer distance and the coating weight of each active material layer, thereby achieving both high energy density and good charge / discharge kinetic performance.

[0034] The negative electrode plate of the present application includes a negative electrode current collector and an active material layer disposed on at least one surface of the negative electrode current collector, the active material layer including a first active material layer and a second active material layer disposed on a surface of the first active material layer, the first active material layer including a first active material, the second active material layer including a second active material, and the active material layers satisfy α×CW2≦CW1, where: JPEG0007674463000005.jpg24166d1: Interlayer distance corresponding to the d002 peak of the first active material, unit: nm; d2: the interlayer distance corresponding to the d002 peak of the second active material, unit: nm; CW1: mass of the first active material layer placed on the negative electrode current collector per unit area, unit: g / m 2When a first active material layer and a second active material layer are provided on both sides of the negative electrode current collector, the mass of the first active material layer on both sides is represented by CW2: Mass of the second active material layer placed on the negative electrode current collector per unit area, unit: g / m 2 When a first active material layer and a second active material layer are provided on both sides of the negative electrode current collector, the mass of both sides of the second active material layer is taken as the mass of both sides of the second active material layer.

[0035] Thus, the present application employs a two-layer or multi-layer active material layer for the negative electrode, and adjusts and controls the relationship between the interlayer distance and the coating weight of each active material layer, thereby obtaining a battery negative electrode with both higher energy density and better charge / discharge dynamic performance. More specifically, the inventors of the present application found that two active material layers are coated on the current collector on the same side of the negative electrode plate, and the interlayer distance of the active material of the second active material layer is greater than the interlayer distance of the active material of the first active material layer, and when lithium ions move from the positive electrode to the negative electrode, the interlayer distance of the surface layer material is large and the absorption impedance of lithium ions is low, so that the lithium ions are absorbed quickly into the surface active material, and the deposition of lithium ions on the surface of the negative electrode plate due to excessive charging speed can be avoided. The larger the interlayer distance of the negative electrode active material, the lower the capacity of the material, so the coating weight of the second active material becomes larger, and the impact on the capacity of the entire negative electrode plate becomes greater. In order to achieve both the capacity of the negative electrode plate and the performance of the charging window, the present application limits the coating weight of the second active material layer. The larger the interlayer distance of the active material of the second active material layer, the higher its charging ability and the lower its capacity. Accordingly, the smaller the coating weight, the better the charging level can be achieved. If the interlayer distance of the active material of the second active material layer is relatively small, its charging ability will be weak and its capacity will be large. At this time, in order to obtain good charging performance as a whole electrode plate, it is necessary to increase the ratio of the coating weight of the second active material layer to the coating weight of the whole electrode plate. The inventors of the present application have found that by using a two-layer active material layer structure, the interlayer distance of the active material of the first active material layer is small, the capacity is large, and the electrode plate and the battery have a relatively high energy density, and the interlayer distance of the active material of the second active material layer is large, the lithium absorption impedance of the surface layer of the negative electrode plate is reduced, and the deposition of lithium ions on the surface of the negative electrode during high-rate charging is avoided, and the charging window of the battery is improved. Therefore, a battery negative electrode having an active material layer that satisfies the above relationship combines energy density with good charge / discharge kinetic performance.

[0036] JPEG0007674463000006.jpg15150

[0037] The weight of the second active material layer is adjusted according to the interlayer distance and the weight of the first active material layer. In order to provide the negative electrode plate with both high energy density and dynamic performance as a whole, the coating weight of the second active material layer is should satisfy JPEG0007674463000007.jpg1760.

[0038] The inventors of the present application have found that the smaller the weight of the active material layer applied on the negative electrode plate, the larger the interlayer distance of the active material, the lower the internal resistance of the electrode plate and the battery, and the better the charge and discharge performance, but when the weight of the active material layer is small and the interlayer distance of the active material is large, the same battery capacity will result in a decrease in the energy density of the battery due to the increase in the amount of auxiliary materials such as foil materials and the increase in the amount of materials used. In order to achieve both the energy density and charging performance of the battery and avoid the influence of over-designing one performance causing a shortage of the other performance, the inventors further limited the relationship between the application weight and the interlayer distance of the first and second active material layers based on the actual test effect. When this relationship is satisfied, the rate performance and energy density of the negative electrode plate and the battery can both be well improved.

[0039] JPEG0007674463000008.jpg20167Da 50 : volume average particle size of the first active material, unit: μm; Db 50 : Volume average particle size of the second active material, unit: μm.

[0040] JPEG0007674463000009.jpg38168

[0041] In some embodiments, the volume average particle size Da of the first active material 50 and the volume average particle size Db of the second active material 50 teeth, Fill in JPEG0007674463000010.jpg1870.

[0042] The particle size relationship of the active materials in the two active material layers is specified, which further improves the dynamic performance and is advantageous for achieving processing performance when the coating amount of the second layer is low.

[0043] In some embodiments, the interlayer distance d1 corresponding to the d002 peak of the first active material is in the range of 0.335 to 0.3362 nm, and the interlayer distance d2 corresponding to the d002 peak of the second active material is in the range of 0.3356 to 0.38 nm.

[0044] In some embodiments, the first active material has a volume average particle size Da50 in the range of 8 to 20 μm, and the second active material has a volume average particle size Db50 in the range of 4 to 12 μm.

[0045] In some embodiments, the mass CW1 of the first active material layer disposed on the negative electrode current collector per unit area is in the range of 80 to 200 g / m 2 and the mass CW2 of the second active material layer placed on the negative electrode current collector per unit area is in the range of 10 to 110 g / m 2 It is.

[0046] In this application, the volume average particle size D50 of a material has a meaning known in the art and may be measured using methods and instruments known in the art, for example, it can be measured using a laser particle size analyzer (e.g., Marvin Mastersizer 2000E, UK) with reference to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method.

[0047] In some embodiments, the negative electrode plate further includes a conductive agent and an adhesive, the type and content of which are not specifically limited and can be selected according to actual needs. Exemplarily, the conductive agent may include one or more of superconducting carbon, carbon black (e.g., acetylene black, ketjen black, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The adhesive may include one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). The other optional auxiliary agents may be the same or different, and exemplarily, the other optional auxiliary agents may include thickeners (e.g., sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials, etc.

[0048] In the negative electrode plate of the present application, the negative electrode current collector may adopt a metal foil sheet or a composite current collector. An example of the metal foil sheet may adopt copper foil. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. Exemplarily, the metal material may be selected from one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. Exemplarily, the polymeric material base layer may be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0049] In some embodiments, the active material layer is disposed on at least one surface of the negative electrode current collector, for example, the negative electrode current collector has two opposing surfaces in the thickness direction of the negative electrode current collector, and the active material layer is disposed on either one or both of the two opposing surfaces of the negative electrode current collector.

[0050] FIG. 1 shows a negative electrode current collector and active material layers on its surfaces, and each of the two surfaces of the negative electrode current collector shown in FIG. 1 has a first active material layer and a second active material layer.

[0051] Of course, the negative electrode plate 10 of the present application may have other embodiments, for example, the negative electrode plate 10 is composed of a negative electrode collector 11, a first active material layer 121 disposed on one side of the negative electrode collector, and a second active material layer 122 disposed on the first active material layer 121.

[0052] In addition, the negative electrode plate of the present application does not exclude additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the present application may further include a conductive undercoat layer (e.g., made of a conductive agent and an adhesive) disposed between the negative electrode current collector and the second negative electrode film layer. In other embodiments, the negative electrode plate of the present application further includes a protective layer covering the surface of the first negative electrode film layer.

[0053] In some embodiments, the method for producing a negative electrode plate of the present application includes: 1. Separately preparing a slurry A containing a first active material and a slurry B containing a second active material; 2. Calculating CW1 and CW2 from the interlayer distance of the first active material and the interlayer distance of the second active material; 3. Applying the slurry A to a current collector and drying it to obtain a plate A coated with a first active material layer; 4. Applying slurry B to the surface of electrode plate A, drying, and cold pressing and slitting to obtain the negative electrode plate described in the present application; The coating amounts of the first active material layer and the second active material layer satisfy CW1 and CW2, respectively.

[0054] In some embodiments, the slurry A includes one or more of a first active material, a conductive agent, an adhesive, and a thickener.

[0055] In some embodiments, the slurry B includes one or more of a second active material, a conductive agent, an adhesive, and a thickener.

[0056] The specific method for manufacturing the negative electrode may be referred to in the specific examples of the present application, and will not be described further herein.

[0057] [Positive electrode plate] A secondary battery includes a positive electrode plate, which generally includes a positive electrode current collector and a positive electrode film layer that is disposed on at least one surface of the positive electrode current collector and includes a positive electrode active material. For example, the positive electrode current collector has two surfaces that face each other in the thickness direction of the positive electrode current collector, and the positive electrode film layer is disposed on either one or both of the two facing surfaces of the positive electrode current collector.

[0058] In the positive electrode plate of the present application, the positive electrode current collector may adopt a metal foil sheet or a composite current collector. As an example of the metal foil sheet, the positive electrode current collector may adopt an aluminum foil. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. Exemplarily, the metal material may be selected from one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. Exemplarily, the polymer material base layer may be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0059] In the positive electrode plate of the present application, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material may adopt a positive electrode active material for secondary batteries known in the art. Exemplarily, the positive electrode active material may include one or more of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and modified compounds thereof. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and modified compounds thereof. The present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for secondary batteries may be used. These positive electrode active materials may be used alone or in combination of two or more.

[0060] In the positive electrode plate of the present application, the modified compound of each of the above-mentioned positive electrode active materials may be a doping modification, a surface coating modification, or a simultaneous doping modification and surface coating modification of the positive electrode active material.

[0061] In the positive electrode plate of the present application, the positive electrode membrane layer generally includes a positive electrode active material, an optional adhesive, and an optional conductive agent. The positive electrode membrane layer is generally formed by applying a positive electrode slurry onto a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is generally formed by dispersing the positive electrode active material, the optional conductive agent, the optional adhesive, and any other components in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP). Exemplarily, the adhesive used in the positive electrode membrane layer may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylidene fluoride-tetrafluoroethylene-propylene terpolymer, polyvinylidene fluoride-hexafluoropropene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropene copolymer, and fluorine-containing acrylate resin. For example, the conductive agent used in the positive electrode film layer may include one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. It should be noted that the configuration or parameters of each positive electrode film layer described in this application refer to the range of the configuration or parameters of a single film layer of a positive electrode current collector. When the positive electrode film layers are installed on two opposing surfaces of a positive electrode current collector, if the configuration or parameters of the positive electrode film layer on either surface meets the present application, it is deemed to be within the protection scope of this application.

[0062] [Electrolyte] The electrolyte serves to conduct active ions between the positive and negative electrodes. The secondary battery of the present application is not specifically limited to the type of electrolyte, and may be selected according to need. For example, the electrolyte may be selected from at least one of a solid electrolyte and a liquid electrolyte (i.e., an electrolytic solution).

[0063] In some embodiments, the electrolyte employs an electrolyte solution, which includes an electrolyte salt and a solvent.

[0064] In some embodiments, the type of electrolyte salt is not specifically limited and can be selected according to actual demand.Exemplarily, the electrolyte salt can be selected from one or more of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiAsF6 (lithium hexafluoroarsenate), LiFSI (lithium bisfluorosulfonimide), LiTFSI (lithium bistrifluoromethanesulfonimide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluoro(oxalato)borate), LiBOB (lithium bis(oxalato)borate), LiPO2F2 (lithium difluorophosphate), LiDFOP (lithium difluorobis(oxalato)phosphate) and LiTFOP (lithium tetrafluoro(oxalato)phosphate).

[0065] In some embodiments, the type of solvent is not specifically limited and can be selected according to actual needs. Illustratively, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfone (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0066] Optionally, in some embodiments, the solvent is a non-aqueous solvent.

[0067] In some embodiments, the electrolyte solution optionally further includes additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive that can improve some performance of the battery, such as an additive that improves the overcharge performance of the battery, an additive that improves the high temperature performance of the battery, or an additive that improves the low temperature performance of the battery.

[0068] [Separator] A separator is further included in secondary batteries using an electrolyte and in some secondary batteries using a solid electrolyte. The separator is disposed between the positive electrode plate and the negative electrode plate to achieve the effect of isolation. In the present application, there is no particular limitation on the type of separator, and any separator with a porous structure having well-known good chemical stability and mechanical stability may be selected. In some embodiments, the material of the separator may be selected from one or more of glass fiber, nonwoven 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.

[0069] In some embodiments, the positive and negative plates and the separator can be manufactured into an electrode component by a winding or lamination process.

[0070] In some embodiments, the secondary battery may include an exterior packaging, which may be used to package the electrode components and electrolyte.

[0071] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a soft bag, such as a pouch-type soft bag. The material of the soft bag may be one or more of plastics, such as polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0072] The present application does not particularly limit the shape of the secondary battery, which may be cylindrical, rectangular or any other shape. For example, FIG. 2 shows a secondary battery 5 with a rectangular structure as an example.

[0073] In some embodiments, referring to FIG. 3, the exterior may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate surround and form a chamber. The case 51 has an opening communicating with the chamber, and the cover plate 53 is disposed over the opening to close the chamber. The positive electrode plate, the negative electrode plate and the separator may form an electrode component 52 by a winding process or a lamination process. The electrode component 52 is packaged in the chamber. The electrolyte is permeated into the electrode component 52. The number of electrode components 52 included in the secondary battery 5 may be one or more, and may be adjusted according to demand.

[0074] In some embodiments, the secondary batteries may be assembled into a battery module, and the battery module may include multiple secondary batteries, with the specific number being selected based on the application and capacity of the battery module.

[0075] Fig. 4 shows an example of a battery module 4. Referring to Fig. 4, in the battery module 4, the multiple secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the multiple secondary batteries 5 may be fixed by a fastener.

[0076] Optionally, the battery module 4 may further include a housing having an accommodating space, and the multiple secondary batteries 5 are accommodated in the accommodating space.

[0077] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be selected based on the application and capacity of the battery pack.

[0078] 5 and 6 show an example of a battery pack 1. Referring to Fig. 5 and Fig. 6, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 is covered by the lower housing 3 to form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0079] power consumption equipment An embodiment of the present application further provides a power consuming device including at least one of a secondary battery, a battery module, and a battery pack according to the present application. The secondary battery, the battery module, or the battery pack may be used as a power source for the power consuming device, or may be used as an energy storage unit for the power consuming device. The power consuming device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0080] The power consumption device may select a secondary battery, a battery module or a battery pack according to the needs of its usage.

[0081] 7 shows an example power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. A battery pack or battery module may be employed to meet the high power and high energy density demands of the power consuming device.

[0082] As another example, the power consuming device may be a mobile phone, a tablet computer, a notebook computer, etc. Generally, such a power consuming device is required to be thin and lightweight, and may employ a secondary battery as a power source.

[0083] Working Example The following examples are used only to more specifically describe the contents disclosed in the present application, and it is obvious to those skilled in the art that various modifications and changes are made within the scope of the disclosure of the present application, so these examples are used only to describe the contents.Unless otherwise stated, all ingredients, percentages, and ratios reported in the following examples are calculated by weight, and all reagents, first active materials, and second active materials used in the examples are commercially available or obtained by synthesis according to conventional methods, and all equipment used in the examples are commercially available.

[0084] Examples 1-9 The lithium ion batteries including the negative electrode plates of the present application in Examples 1-9 are manufactured in the following manner.

[0085] Negative electrode plate manufacturing 1. According to Table 1, the first active material of the first active material layer, the conductive agent Super-P, the adhesive SBR, and the thickener CMC are mixed in a mass ratio of 96:1:2:1, and then thoroughly stirred and mixed in a deionized water solvent to obtain slurry A.

[0086] 2. According to Table 1, the second active material of the second active material layer, the conductive agent Super-P, the adhesive SBR, and the thickener CMC are mixed in a mass ratio of 96:1:2:1, and then thoroughly stirred and mixed in a deionized water solvent to obtain slurry B.

[0087] 3. Based on Table 1, slurry A is applied onto a Cu foil and then dried to obtain electrode plate A coated with a first active material layer.

[0088] 4. Based on Table 1, slurry B is applied to the surface of electrode plate A, dried, and then cold pressed and slit to obtain a negative electrode plate having two active material layers.

[0089] The coating amounts of the first active material layer and the second active material layer satisfy CW1 and CW2, respectively.

[0090] Positive electrode plate manufacturing The positive electrode active material LiFePO4, conductive agent acetylene black, and adhesive polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 96:2:2, solvent N-methylpyrrolidone (NMP) is added, and the mixture is stirred in a vacuum mixer until the system is homogeneous to obtain positive electrode slurry. The positive electrode slurry is evenly applied onto the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven to continue drying, and then cold pressed and slit to obtain the positive electrode plate.

[0091] Electrolyte production Ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then a sufficiently dried lithium salt LiPF6 is dissolved in the organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0092] Separator manufacturing A polyethylene film is used as the separator.

[0093] Secondary battery manufacturing A positive electrode plate, a separator, and a negative electrode plate are stacked in order, the separator is placed between the positive electrode plate and the negative electrode plate to provide an insulating effect, and then the stack is wound to obtain an electrode component. The electrode component is placed in an outer casing, dried, and then an electrolyte is injected. The secondary battery is obtained through processes such as vacuum packaging, standing, chemical formation, and shaping.

[0094] Comparative Example 1-3 The manufacturing method of the secondary battery of Comparative Example 1-3 was similar to that of Example 1-13, with the difference being in the manufacturing process of the negative electrode plate, the details of which are shown in Table 1.

[0095] Testing part Energy density: At 25℃, a lithium-ion battery is charged to 4.2V at a constant current of 1C, then charged to a current of less than 0.05C at a constant voltage of 4.2V, and then discharged to 2.8V at 0.1C to obtain discharge energy Q. If the mass of the battery is M, then the energy density = Q / M.

[0096] Charge time: The time required for constant current charging at 25° C. to 85% SOC, which is the window rate for lithium deposition at 85% SOC, is the charge time described in this application.

[0097] [Table 1] JPEG0007674463000012.jpg206138

[0098] In the present application, a two-layer or multi-layer active material layer is employed for the negative electrode, and the relationship between the interlayer distance and the coating weight of each active material layer is adjusted and controlled, thereby making it possible to obtain a battery negative electrode having both higher energy density and better charge / discharge kinetic performance.

[0099] Comparing Examples 1-9 and Comparative Examples 1-3 based on Table 1, it can be seen that by using two active material layers in the negative electrode and adjusting and controlling the relationship between the interlayer distance and the coating weight of each active material layer, a secondary battery with both higher energy density and better charge / discharge kinetic performance can be obtained. In short, the negative electrode materials produced by the method of the present invention all satisfy the charging time≦75min and 0.3C energy density≧170Wh / kg.

[0100] Comparative Examples 1-3 do not meet the relationship between the interlayer distance and the coating weight of each active material layer of the present application. Specifically, when comparing Comparative Example 1 with Example 1 of the present application, the second active material of Comparative Example 1 adopts hard carbon with a larger interlayer distance, and its capacity density is much lower than that of Example 1 of the present application. That is, the larger the interlayer distance of the active material of the second active material layer, the higher its charging ability, but the lower the capacity, and it is clear that the energy density and the charge / discharge kinetic performance cannot be compatible. Compared with Example 1, in Comparative Example 2, the interlayer distance relative coefficient α is outside the range of the present application (1≦α≦1.12), and the energy density and the charge / discharge kinetic performance cannot be compatible. Compared with Example 1, Comparative Example 3 is a single-layer coating, and under the premise of the same coating amount, the single-layer coating cannot achieve both the energy density and the charge / discharge kinetic performance.

[0101] Furthermore, compared with Examples 1-3, the CW2 / (CW2+CW1) of Example 5 exceeds the scope of the present application, and although the charge / discharge kinetic performance is good, it is impossible to achieve a good balance with the energy density. Conversely, the CW2 / (CW2+CW1) of Example 4 exceeds the scope of the present application, and although the energy density is good, it is impossible to achieve a good balance with the charge / discharge kinetic performance.

[0102] Furthermore, compared with Examples 1, 6, and 7, the Db50 / Da50 of Examples 8 and 9 is outside the scope of the present application, and it is not possible to achieve both energy density and charge / discharge dynamic performance.

[0103] The above description is merely a specific embodiment of the present application, and the scope of protection of the present application is not limited thereto. Any modifications or replacements that can be easily conceived by any person skilled in the art within the technical scope set forth in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

[0104] It should be noted that the present application is not limited to the above-mentioned embodiment. The above-mentioned embodiment is merely an example, and any embodiment having substantially the same configuration as the technical idea and having the same action and effect within the scope of the technical proposal of the present application is included in the technical scope of the present application. In addition, various modifications that a person skilled in the art can conceive of to the embodiment are implemented within the scope of the gist of the present application, and other forms constructed by combining some of the components in the embodiment are also included in the scope of the present application. [Explanation of symbols]

[0105] In the drawings, the drawings are not drawn to scale. 1 battery pack 2 Upper housing 3 Lower housing 4 Battery Module 5 secondary battery 51 cases 52 electrode components 53 Lid plate.

Claims

1. A negative electrode plate including a negative electrode current collector and an active material layer disposed on at least one surface of the negative electrode current collector, the active material layer including a first active material layer and a second active material layer disposed on a surface of the first active material layer, the first active material layer including a first active material, the second active material layer including a second active material, and the active material layer is a lattice constant of α×CW ２ ≦C.W. １ where d １ : Interlayer distance corresponding to the d002 peak of the first active material, unit: nm, d １ The range is 0.335 to 0.3358 nm, d ２ : Interlayer distance corresponding to the d002 peak of the second active material, unit: nm, C.W. １ : Mass of the first active material layer disposed on the negative electrode current collector per unit area, unit: g / m ２ , C.W. ２ : Mass of the second active material layer placed on the negative electrode current collector per unit area, unit: g / m ２ Indicates the negative electrode plate.

2. The active material layer is The negative electrode plate according to claim 1 ,

3. The volume average particle size Da of the first active material ５０ and the volume average particle size Db of the second active material ５０ teeth, The negative electrode plate according to claim 2 ,

4. The volume average particle size Da of the first active material ５０ The range of the volume average particle diameter Db of the second active material is 8 to 20 μm. ５０ The negative electrode plate according to claim 2 or 3, wherein the range is 4 to 12 μm.

5. Mass CW of the first active material layer placed on the negative electrode current collector per unit area １ The range is 80 to 200 g / m ２ and the mass CW of the second active material layer placed on the negative electrode current collector per unit area. ２ The range is 10 to 110 g / m ２ The negative electrode plate according to any one of claims 2 to 4,

6. the first active material is a natural or synthetic graphite material; and / or 6. The negative electrode plate of claim 1, wherein the second active material is an artificial graphite material.

7. The negative electrode plate according to claim 1 , wherein the first active material layer and / or the second active material layer contains soft carbon or hard carbon.

8. A secondary battery comprising the negative electrode plate according to any one of claims 1 to 7.

9. A battery module comprising the secondary battery according to claim 8 .

10. A battery pack comprising the secondary battery according to claim 8 or the battery module according to claim 9.

11. A power consuming device comprising at least one of the secondary battery according to claim 8, the battery module according to claim 9, and the battery pack according to claim 10.

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