Secondary battery and device
The three-layer electrode structure in cylindrical batteries addresses the disparities in thermal conductivity and peeling force, enhancing performance uniformity and extending battery life by creating a uniform performance environment.
Patent Information
- Application Number
- CN202323464261.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-18
- Publication Date
- 2024-12-13
- Estimated Expiration
- 2033-12-18
AI Technical Summary
Cylindrical lithium-ion batteries experience significant performance disparities due to temperature and electrolyte infiltration differences between the central and outer regions, leading to uneven degradation and reduced battery life.
A secondary battery design with a three-layer electrode sheet structure, featuring a central, transition, and peripheral region, where the central region has a composite layer formed by stacking the first and third active material layers, the transition region has a different active material layer and a third active material layer, optimized for thermal conductivity and peeling force, and the transition region balances these properties to create a uniform performance environment.
The design enhances the balance of working conditions across the battery, improving performance uniformity and extending the battery's service life by addressing temperature and electrolyte distribution issues.
Smart Images
Figure CN222168469U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of energy storage, and in particular to a secondary battery and a device. Background Art
[0002] Lithium-ion batteries have the advantages of high energy density, good power performance, and long cycle life, and have been increasingly used in the field of electric vehicles in recent years. Among the many types of lithium battery structures, cylindrical batteries occupy an important position in the market due to their comprehensive advantages of outstanding safety, high production efficiency, and low manufacturing cost.
[0003] However, current secondary batteries and devices still need to be improved. Utility Model Content
[0004] The inventors found some problems in the application of cylindrical batteries. First, the working temperature of cylindrical batteries from the inside to the outside in the radial direction is quite different. The temperature in the center area is significantly higher than that in the outer layer, causing the pole pieces in the center area to be in a high temperature environment for a long time. The performance decays significantly faster than that in the outer layer, which leads to the rapid decay of the overall battery performance and shortens the battery life. Secondly, due to the structural characteristics of the cylinder itself, the inner pole pieces have obvious deviations in electrolyte infiltration compared with the outer pole pieces. Therefore, the pole pieces in different areas have different performance, which affects the battery performance. Therefore, the art needs a secondary battery whose electrode pole pieces can have a balanced working environment in the radial direction.
[0005] In view of the above problems existing in the prior art, the present application provides a secondary battery having an electrode sheet in a winding structure, the electrode sheet having a current collector and an active material layer arranged on the surface of the current collector, the electrode sheet having a length L in the circumferential direction, the electrode sheet having a first region, a second region and a third region in the circumferential direction in sequence, the length of the first region being L 1 , the length of the second region is L 2 , the length of the third region is L 3 , L 1 0.2L to 0.3L, L 2 0.4L to 0.6L, L 3 is 0.2L to 0.3L; wherein the active material layer comprises a first active material layer arranged in the first region, a composite layer arranged in the second region and a third active material layer arranged in the third region, and the composite layer is formed by stacking the first active material layer and the third active material layer; in the second region, the first active material layer is arranged between the third active material layer and the current collector.
[0006] In some embodiments, the first active material layer and the third active material layer are composed of different materials.
[0007] In some embodiments, the first region forms a central region in the radial direction of the secondary battery, the second region forms a transition region in the radial direction, the third region forms a peripheral region in the radial direction, and the central region, transition region, and peripheral region are arranged from inside to outside in the radial direction.
[0008] In some embodiments, the first active material layer, the composite layer, and the third active material layer have the same thickness T.
[0009] In some embodiments, the thickness T of the composite layer is determined by the thickness T of the first active material layer in the second region. 1 and the thickness T of the third active material layer in the second region 3 Composition; T in the second region near the first region 1 Greater than or equal to T of a position away from the first region 1 , T of the position in the second region close to the third region 3 Greater than or equal to T of a position away from the third region 3 .
[0010] In some embodiments, in the second region, the interface between the first active material layer and the third active material layer is in a straight line shape, a step shape, a pulse shape, an arc shape, or any combination thereof.
[0011] In some embodiments, the conductivity of the first active material layer is greater than the conductivity of the third active material layer.
[0012] In some embodiments, the cycle life of the first active material layer is greater than the cycle life of the third active material layer.
[0013] In some embodiments, the peeling force between the first active material layer and the current collector is greater than the peeling force between the third active material layer and the current collector.
[0014] In some embodiments, the peeling force between the composite layer and the current collector is greater than the peeling force between the third active material layer and the current collector.
[0015] In some embodiments, the electrode sheet is a positive electrode sheet, and the gram capacity of the first active material layer is less than the gram capacity of the third active material layer.
[0016] In some embodiments, the electrode sheet is a negative electrode sheet, and the gram capacity of the first active material layer is less than the gram capacity of the third active material layer.
[0017] The present application also aims to provide a device, which includes the secondary battery according to the present application.
[0018] The beneficial effects of this application are:
[0019] The secondary battery provided by the present application, by arranging a composite layer in the second area (forming a transition area after winding) of the electrode plate of the secondary battery, the winding structure formed by winding the electrode plate forms a three-layer structure of a central area, a transition area, and a peripheral area from the center to the outer layer. The three-layer structure has different functions and performances, and realizes the optimization of functions and performances of different areas, thereby improving the balance of the working environment and accurately regulating the radial differences of the cylindrical battery, alleviating the problems of differences in working temperature, wetting, etc. between the central area and the peripheral area of the cylindrical battery during use, thereby improving the comprehensive performance of the secondary battery and extending its service life. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 A schematic diagram showing an electrode sheet after unfolding according to an embodiment of the utility model is shown;
[0021] Figure 2 A schematic diagram of another embodiment of the present invention after the electrode sheet is wound is shown. DETAILED DESCRIPTION
[0022] The embodiments of the present application will be described in detail below. The embodiments of the present application should not be interpreted as limiting the present application.
[0023] In addition, sometimes amounts, ratios and other numerical values are presented in a range format in this application. It should be understood that such a range format is for convenience and brevity, and should be flexibly understood to include not only the numerical values explicitly specified as range limits, but also all individual numerical values or sub-ranges included in the range, as if each numerical value and sub-range were explicitly specified.
[0024] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.
[0025] In the context of the present application, the terms "center", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.
[0026] In the context of this application, the terms "first", "second" and "third" etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.
[0027] In the context of this application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.
[0028] Primary and secondary batteries
[0029] The present application provides a secondary battery, referring to Figures 1-2 The secondary battery has an electrode sheet in a winding structure, the electrode sheet has a current collector and an active material layer arranged on the surface of the current collector, the electrode sheet has a length L in the circumferential direction, and the electrode sheet has a first region, a second region and a third region in the circumferential direction in sequence, and the length of the first region is L 1 , the length of the second region is L 2 , the length of the third region is L 3 , L 1 0.2L to 0.3L, L 2 0.4L to 0.6L, L 3 The active material layer has a first active material layer arranged in the first region, a composite layer arranged in the second region, and a third active material layer arranged in the third region, and the composite layer is formed by stacking the first active material layer and the third active material layer; in the second region, the first active material layer is arranged between the third active material layer and the current collector. It should be noted that the electrode sheet is in the circumferential direction, that is, the winding direction of the electrode sheet.
[0030] Therefore, the secondary battery provided by the present application, by arranging a composite layer in the second area of the electrode plate of the secondary battery (forming a transition area after winding), the winding structure formed by winding the electrode plate forms a three-layer structure of a central area, a transition area, and a peripheral area from the center to the outer layer. The three-layer structure has different functions and performances, and realizes the optimization of functions and performances of different areas, thereby improving the balance of the working environment and accurately regulating the radial differences of the cylindrical battery, alleviating the problems of differences in working temperature, wetting, etc. between the central area and the peripheral area of the cylindrical battery during use, thereby improving the comprehensive performance of the secondary battery and extending its service life.
[0031] In some embodiments, reference Figure 1 (Cross-section view of the electrode sheet after expansion), L 1 is 0.2 L, 0.22 L, 0.24 L, 0.26 L, 0.28 L, 0.3 L or any value therebetween. In some embodiments, L 2 0.4 L, 0.42 L, 0.44 L, 0.46 L, 0.48 L, 0.5 L, 0.52 L, 0.54 L, 0.56 L, 0.58 L, 0.6 L or any value therebetween. In some embodiments, 0.2 L, 0.22 L, 0.24 L, 0.26 L, 0.28 L, 0.3 L or any value therebetween.
[0032] In some embodiments, reference Figure 2 (Top view of the electrode sheet after winding), the first area forms a central area in the radial direction of the secondary battery, the second area forms a transition area in the radial direction, and the third area forms a peripheral area in the radial direction. The central area, transition area and peripheral area are arranged from inside to outside in the radial direction. Therefore, the three-layer structure of the central area, transition area and peripheral area has different functions and performances, realizes the optimization of functions and performances of different areas, and balances the uniformity of the performance of the cylindrical battery in the microscopic area.
[0033] In some embodiments, the first active material layer, the composite layer, and the third active material layer have the same thickness T.
[0034] In some embodiments, the thickness T of the composite layer is determined by the thickness T of the first active material layer in the second region. 1 and the thickness T of the third active material layer in the second region 3 Composition: T in the second region near the first region 1 Greater than or equal to T at a position away from the first region 1 , T of the position in the second area close to the third area 3 Greater than or equal to T at a position away from the third region 3 .
[0035] In some embodiments, the composite layer is formed by stacking the first active material layer and the third active material layer. In some embodiments, in the second region, the first active material layer is disposed between the third active material layer and the current collector, and the interface between the first active material layer and the third active material layer is linear, stepped, pulsed, arc-shaped, or any combination thereof.
[0036] In some embodiments, the constituent materials of the first active material layer and the third active material layer are different. It should be noted that the constituent materials of the first active material layer and the third active material layer are different, which means that the two active material layers have the same active material type (for example, both are positive electrode active materials or both are negative electrode active material layers), but the specific material category of the active material, the mass percentage of each component, etc. are different. In some embodiments, the conductivity of the first active material layer and the third active material layer are different. In some embodiments, the peeling force between the first active material layer and the current collector is different from the peeling force between the third active material layer and the current collector. In some embodiments, the gram capacity of the first active material layer and the third active material layer is different. In some embodiments, the cycle life of the first active material layer and the third active material layer is different.
[0037] Specifically, the first region and the second region may be coated to form a first active material layer (located in the first region) and an active material layer (formed with the same material as the first active material layer) located in the second region, and then the third region and the second region may be coated to form a third active material layer (located in the third region) and an active material layer (formed with the same material as the third active material layer) located in the second region, whereby the two stacked active material layers located in the second region constitute the composite layer. That is, the first active material layer extending to the second region and the third active material layer extending to the second region constitute the composite layer.
[0038] More specifically, the first and third regions are coated with a single layer, which is composed of a single slurry formula. Different slurry formulas are designed to achieve functional differences between the first and third regions. The selection of the active material layer formulas for the first and third regions comprehensively considers the differences in the working temperature field and wetting between the central and outer regions of the cylindrical battery to optimize the formula and balance the uniformity of the performance of the cylindrical battery in the microscopic region. For example, the slurry formula of the first region is composed of 94wt% to 97wt% active material, 1wt% to 3wt% binder and 1wt% to 3wt% conductive agent, the conductive agent is carbon nanotubes, which improves the thermal conductivity and heat dissipation properties of the pole piece itself, and the slurry formula of the third region is composed of 95wt% to 98wt% active material, 0.5wt% to 2wt% binder and 0.5wt% to 2wt% conductive agent. From the comparison of the slurry formula, it can be seen that the proportion of binder and conductive agent in the first region formula is significantly higher than that in the third region. By increasing the content of the conductive agent in the first region, the thermal conductivity and heat dissipation capacity of the pole piece in this region, the rate and storage capacity of the pole piece to absorb electrolyte, and the wetting effect of the pole piece in the central region of the battery are improved. Increasing the proportion of the binder in the first region can improve the overall peeling force of the bottom pole piece in the first and second regions, improve the flexibility of the pole piece, avoid the pole piece from dropping when winding, and avoid the active material and current collector peeling phenomenon due to insufficient bonding force of the pole piece during use of the battery, causing the rapid attenuation of battery performance. In the selection of active materials in the first and third regions, in order to balance the difference in cycle performance between the electrodes in the central region and the peripheral region of the winding core, and considering the influence of the operating temperature on the cycle life of the electrodes, the active material selection in the first region is consistent with that in the third region in terms of material type, but the cycle life of the active material in the first region is required to be better than that in the third region, or the gram capacity of the active material in the first region is less than that in the third region. For example, the active material in the first region is LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi is selected in the third area 0.9 Co 0.05 Mn 0.05 O 2 (NCM900), for example, the active material of the first region is artificial graphite with a density of 350 mAh / g, and the active material of the third region is artificial graphite with a density of 360 mAh / g.
[0039] More specifically, the second region is coated with a double layer, the bottom active material layer has the same active material slurry formula as the first region, the surface density or thickness gradually decreases along the circumferential direction (for example, from 100% to 0%), the upper active material layer has the same active material slurry formula as the third region, the surface density or thickness gradually increases along the circumferential direction (for example, from 0% to 100%), and the coated electrode sheet is dried and cured in an oven to form the electrode sheet of this structure. Double-layer coating ensures that the total thickness of the active material layer in the second region is the same as the thickness of the active material layer in the first region and the third region (no obvious steps observed by naked eye), thereby achieving a uniform transition of the performance of the electrode sheet in the circumferential direction.
[0040] In some embodiments, the conductivity of the first active material layer is greater than the conductivity of the third active material layer.
[0041] In some embodiments, the peeling force between the first active material layer and the current collector is greater than the peeling force between the third active material layer and the current collector.
[0042] In some embodiments, the peeling force between the composite layer and the current collector is greater than the peeling force between the third active material layer and the current collector.
[0043] In some embodiments, the cycle life of the first active material layer is greater than the cycle life of the third active material layer.
[0044] In some embodiments, the electrode plate is a positive electrode plate, and the electrode plate is described in detail below as a positive electrode plate.
[0045] In some embodiments, the gram capacity of the first active material layer is less than the gram capacity of the third active material layer.
[0046] In some embodiments, the cycle life of the first active material layer is greater than the cycle life of the third active material layer.
[0047] In some embodiments, the positive electrode sheet includes a current collector and a positive electrode active material layer located on the surface of the current collector, and the positive electrode active material layer is composed of a positive electrode active material, a binder and a conductive agent. Thus, the binder improves the bonding between the positive electrode active material particles and also improves the bonding between the positive electrode active material and the current collector. In some embodiments, the current collector is aluminum foil, aluminum alloy, stainless steel foil, nickel, nickel alloy, titanium, titanium alloy, silver or silver alloy. The positive electrode active material is LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi0.8 Co 0.1 Mn 0.1 O 2 (NCM811), LiNi 0.9 Co 0.05 Mn 0.05 O 2 (NCM900), LiNi 0.92 Co 0.05 Mn 0.03 O 2 (Ni92) or LiNi 0.95 Co 0.05 O 2 (Ni95). The binder is polyvinylidene fluoride. The conductive agent is conductive carbon black and / or carbon nanotubes.
[0048] In some embodiments, based on the mass of the positive electrode active material layer, the mass percentage of the positive electrode active material is 95% to 98%, the mass percentage of the binder is 1% to 1.8%, and the mass percentage of the conductive agent is 0.9% to 1.3%. In some embodiments, based on the mass of the active material layer, the mass percentage of the positive electrode active material is 95%, 96%, 97%, 98% or any value therebetween, the mass percentage of the binder is 1%, 1.2%, 1.4%, 1.6%, 1.8% or any value therebetween, and the mass percentage of the conductive agent is 0.9%, 1%, 1.1%, 1.2%, 1.3% or any value therebetween.
[0049] In some embodiments, the positive electrode sheet has a length L in the circumferential direction, and the positive electrode sheet has a first region, a second region, and a third region in the circumferential direction in sequence, and the length of the first region is L 1 , the length of the second region is L 2 , the length of the third region is L 3 , L 1 0.2L to 0.3L, L 2 0.4L to 0.6L, L 3 is 0.2L to 0.3L; wherein the positive electrode active material layer has a first active material layer arranged in the first area, a composite layer arranged in the second area, and a third active material layer arranged in the third area, and the composite layer is formed by stacking the first active material layer and the third active material layer; in the second area, the first active material layer is arranged between the third active material layer and the current collector.
[0050] In some embodiments, the electrode plate is a negative electrode plate, and the following detailed description is made with the electrode plate being a negative electrode plate.
[0051] In some embodiments, the gram capacity of the first active material layer is less than the gram capacity of the third active material layer.
[0052] In some embodiments, the cycle life of the first active material layer is greater than the cycle life of the third active material layer.
[0053] In some embodiments, the negative electrode sheet includes a current collector and a negative electrode active material layer located on the surface of the current collector. In some embodiments, the negative electrode active material layer is composed of a negative electrode active material, a binder and a conductive agent. In some embodiments, the negative electrode active material layer is composed of a negative electrode active material, a binder, a thickener and a conductive agent. In some embodiments, the current collector is copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam or copper foam.
[0054] In some embodiments, the negative electrode active material is composed of a carbon-based material and a silicon-based material. The carbon-based material is at least one of artificial graphite, natural graphite, hard carbon and soft carbon. The silicon-based material is at least one of silicon, silicon alloy, silicon oxide and silicon carbon compound. In some embodiments, the silicon-based material is a silicon oxide and / or a silicon carbon compound. In some embodiments, the silicon oxide is SiO x , 0.5≤x≤1.5. In some embodiments, the binder is polyacrylic acid and styrene-butadiene rubber. The thickener is sodium carboxymethyl cellulose. The conductive agent is conductive carbon black. In some embodiments, based on the mass of the active material layer, the mass percentage of artificial graphite is 80% to 85%, the mass percentage of silicon oxide is 12% to 16%, the mass percentage of the binder is 0.4% to 1.0%, the mass percentage of the thickener is 0.4% to 1.0%, and the mass percentage of the conductive agent is 0.6% to 1.0%.
[0055] In some embodiments, based on the mass of the negative electrode active material layer, the mass percentage of artificial graphite is 80%, 81%, 82%, 83%, 84%, 85% or any value therebetween, the mass percentage of silicon oxide is 12%, 13%, 14%, 15%, 16% or any value therebetween, the mass percentage of binder is 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0% or any value therebetween, the mass percentage of thickener is 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0% or any value therebetween, and the mass percentage of conductive agent is 0.6%, 0.7%, 0.8%, 0.9%, 1.0% or any value therebetween.
[0056] In some embodiments, the negative electrode sheet has a length L in the circumferential direction, and the negative electrode sheet has a first region, a second region, and a third region in the circumferential direction in sequence, and the length of the first region is L 1 , the length of the second region is L 2 , the length of the third region is L 3 , L 10.2L to 0.3L, L 2 0.4L to 0.6L, L 3 is 0.2L to 0.3L; wherein the negative electrode active material layer has a first active material layer arranged in the first area, a composite layer arranged in the second area, and a third active material layer arranged in the third area, and the composite layer is formed by stacking the first active material layer and the third active material layer; in the second area, the first active material layer is arranged between the third active material layer and the current collector.
[0057] In some embodiments, the secondary battery of the present application includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. The electrode sheet is a positive electrode sheet and can be used as the positive electrode sheet of the secondary battery, and the electrode sheet is a negative electrode sheet and can be used as the negative electrode sheet of the secondary battery.
[0058] In some embodiments, the electrolyte is composed of a lithium salt, a solvent, and an additive. In some embodiments, the lithium salt includes, but is not limited to, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonylimide), lithium bis(oxalate borate), or lithium difluorooxalate borate. In some embodiments, the solvent is selected from one or more of ethylene carbonate (EC), propylene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. In some embodiments, the additive is at least one of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), tris(trimethylsilyl) phosphate (TMSP), tris(trimethylsilyl) borate (TMSB), succinonitrile, adiponitrile, glutaronitrile, hexanetrinitrile, methylene methyl disulfonate (MMDS), ethylene ethyl disulfonate, 1,3-propane sultone (PS), 1-propylene-1,3-sultone (PST), 1,4-butane sultone (1,4-BS), vinyl sulfate (DTD), 4-methylethylene sulfate (PCS), 4-ethylethylene sulfate (PES), 4-propylethylene sulfate (PEGLST), propylene sulfate (TS), ethylene sulfite (DTO), dimethyl sulfite (DMS) and diethyl sulfite (DES).
[0059] In some embodiments, the secondary battery of the present application is provided with a separator between the positive electrode and the negative electrode to prevent short circuit. The material and shape of the separator used in the present application are not particularly limited, and it can be any technology disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic substance formed by a material that is stable to the electrolyte of the present application. For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. In some embodiments, a surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixed polymer and an inorganic substance. In some embodiments, the separator includes a porous substrate and a surface layer, and the surface layer includes inorganic particles and a binder. In some embodiments, the thickness of the surface layer is about 0.5 microns to about 10 microns, about 1 micron to about 8 microns, or about 3 microns to about 5 microns.
[0060] In some embodiments, the secondary battery of the present application is a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, a lithium ion polymer secondary battery, a sodium ion secondary battery, a sodium polymer secondary battery, or a sodium ion polymer secondary battery.
[0061] In some embodiments, the secondary battery is a cylindrical battery. Figures 1-2 , the secondary battery has an electrode sheet in a winding structure, that is, the electrode sheet is formed by winding to form the winding structure. The width direction of the electrode sheet is the same as the axial direction of the winding structure, and the length direction of the electrode sheet is the same as the winding direction (circumferential direction) of the winding structure. Specifically, the positive electrode sheet, the first diaphragm and the negative electrode sheet can be stacked in sequence to form a stacked structure, and the stacked structure is wound along the length direction of the stacked structure to form a wound battery cell, that is, a wound structure. Further, the positions of the positive electrode sheet and the negative electrode sheet can be interchanged. Further, the stacked structure also includes a second diaphragm, and the second diaphragm is arranged on the side of the positive electrode sheet away from the first diaphragm, and / or the second diaphragm is arranged on the side of the negative electrode sheet away from the first diaphragm. Thus, in the winding structure formed after winding, the positive electrode sheet and the negative electrode sheet are separated by the first diaphragm or the second diaphragm to prevent short circuit. In some embodiments, the positive electrode sheet, the first separator, the negative electrode sheet and the second separator may be the positive electrode sheet, the separator and the negative electrode sheet described above, which will not be described in detail here.
[0062] 2. Device
[0063] The present application also provides a device, which includes the above-mentioned secondary battery. Therefore, the device has all the features and advantages of the secondary battery provided by the present application, which will not be described in detail here.
[0064] In some embodiments, the devices of the present invention include but are not limited to: laptop computers, pen-type computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD televisions, portable cleaners, portable CD players, mini CDs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars (such as electric vehicles, hybrid electric vehicles or plug-in hybrid electric vehicles), motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries or lithium-ion capacitors, etc.
[0065] Example 1
[0066] Figure 1 The schematic diagram of the electrode sheet after unfolding is shown. The electrode sheet has a current collector and an active material layer arranged on the surface of the current collector. The motor pole sheet has a length L in the circumferential direction. The electrode sheet has a first region, a second region and a third region in the circumferential direction, wherein the length of the first region is L. 1 , the length of the second region is L 2 , the length of the third region is L 3 , L 1 0.2L to 0.3L, L 2 0.4L to 0.6L, L 3 The active material layer comprises a first active material layer arranged in the first region, a composite layer arranged in the second region, and a third active material layer arranged in the third region, the composite layer is formed by stacking the first active material layer and the third active material layer, the interface between the first active material layer and the third active material layer in the composite layer is an inclined surface, and in the composite layer in the second region, the first active material layer is arranged between the third active material layer and the current collector.
[0067] like Figure 2 As shown in FIG. , the secondary battery has an electrode sheet in a wound structure.
[0068] Combination Figure 1 and Figure 2 It can be seen that the first region forms a central region in the radial direction of the secondary battery, the second region forms a transition region in the radial direction, and the third region forms a peripheral region in the radial direction. The central region, transition region and peripheral region are arranged from inside to outside in the radial direction.
[0069] from Figure 1 It can be seen that the first active material layer, the composite layer and the third active material layer have the same thickness T. And the thickness T of the composite layer in the second region is determined by the thickness T of the first active material layer in the second region. 1and the thickness T of the third active material layer in the second region 3 The T of the second region near the first region 1 Greater than or equal to T at a position away from the first region 1 , T of the position in the second area close to the third area 3 Greater than or equal to T at a position away from the third region 3 .
[0070] In order to achieve the above-mentioned purpose and enable technicians in this technical field to understand the application scheme, the following examples are given for the specific implementation scheme adopted in this application. It should be stated that the described embodiments are only partial embodiments of this application, not all embodiments.
[0071] Although some exemplary embodiments of the present application have been illustrated and described, the present application is not limited to the disclosed embodiments. On the contrary, those skilled in the art will recognize that some modifications and changes may be made to the described embodiments without departing from the spirit and scope of the present application as described in the appended claims. As long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any manner.
Claims
1. A secondary battery, It is characterized in that The secondary battery has an electrode sheet in a winding structure, the electrode sheet has a current collector and an active material layer arranged on the surface of the current collector, the electrode sheet has a length L in the circumferential direction, and the electrode sheet has a first region, a second region and a third region in the circumferential direction in sequence, and the length of the first region is L 1 , the length of the second region is L 2 , the length of the third region is L 3 , L 1 0.2L to 0.3L, L 2 0.4L to 0.6L, L 3 0.2L to 0.3L; The active material layer comprises a first active material layer arranged in the first region, a composite layer arranged in the second region, and a third active material layer arranged in the third region, and the composite layer is formed by stacking the first active material layer and the third active material layer; in the second region, the first active material layer is arranged between the third active material layer and the current collector.
2. The secondary battery according to claim 1, It is characterized in that At least one of the following conditions is met: (i) the first active material layer and the third active material layer have different electrical conductivities; (ii) the peeling force between the first active material layer and the current collector is different from the peeling force between the third active material layer and the current collector; (iii) the gram capacities of the first active material layer and the third active material layer are different; (iv) The cycle lives of the first active material layer and the third active material layer are different.
3. The secondary battery according to claim 1 or 2, It is characterized in that The first region forms a central region in the radial direction of the secondary battery, the second region forms a transition region in the radial direction, the third region forms a peripheral region in the radial direction, and the central region, transition region and peripheral region are arranged from inside to outside in the radial direction.
4. The secondary battery according to claim 1 or 2, It is characterized in that The first active material layer, the composite layer, and the third active material layer have the same thickness T.
5. The secondary battery according to claim 4, It is characterized in that The thickness T of the composite layer is determined by the thickness T of the first active material layer in the second region. 1 and the thickness T of the third active material layer in the second region 3 composition; T of the position in the second region close to the first region 1 Greater than or equal to T of a position away from the first region 1 , T of the position in the second region close to the third region 3 Greater than or equal to T of a position away from the third region 3 .
6. The secondary battery according to claim 1, 2 or 5, It is characterized in that In the second region, the interface between the first active material layer and the third active material layer is in a straight line shape, a step shape, a pulse shape, an arc shape, or any combination thereof.
7. The secondary battery according to claim 1, It is characterized in that The electrical conductivity of the first active material layer is greater than the electrical conductivity of the third active material layer; and / or The cycle life of the first active material layer is greater than the cycle life of the third active material layer.
8. The secondary battery according to claim 1, It is characterized in that The peeling force between the first active material layer and the current collector is greater than the peeling force between the third active material layer and the current collector; and / or The peeling force between the composite layer and the current collector is greater than the peeling force between the third active material layer and the current collector.
9. The secondary battery according to claim 1, It is characterized in that The electrode plate is a positive electrode plate, and the gram capacity of the first active material layer is less than the gram capacity of the third active material layer; or The electrode plate is a negative electrode plate, and the gram capacity of the first active material layer is less than the gram capacity of the third active material layer.
10. A device, It is characterized in that A secondary battery comprising the secondary battery according to any one of claims 1 to 9.