Battery cell and battery
By installing elastic elements at the corners of the battery cells, the problems of electrode breakage and lithium plating caused by uneven stress in the cells are solved, thereby improving the cycle performance and lifespan of the batteries.
Patent Information
- Application Number
- CN202422770032.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-13
- Publication Date
- 2025-12-19
- Estimated Expiration
- 2034-11-13
AI Technical Summary
Uneven lateral stress in wound aluminum casings and pouch cells leads to a mismatch between the positive and negative electrode sheets, causing lithium dendrite deposition, increasing cell thickness and posing a risk of internal short circuits. Meanwhile, irreversible expansion of silicon-based cells during charge-discharge cycles can cause breakage of the positive and negative current collectors, affecting battery cycle performance.
An elastic element is provided at the corner of the battery cell, including first and second elastic parts, which are connected by a connecting part. It has a porous structure, which can adjust the force on the battery cell, improve the contact of the electrode and adsorb the electrolyte, and enhance the battery cycle performance.
It improves the problem of electrode breakage and contact during cycling, enhances the cycle performance of the battery, reduces lithium plating, increases the electrolyte adsorption, and improves the cycle life of the battery.
Smart Images
Figure CN223693176U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to the secondary battery field, concretely relates to a battery and electric core. BACKGROUND
[0002] At present, the uneven stress and the positive plate cladding negative plate of the side of the winding type aluminum shell and the soft package battery cause the CB value mismatching problem, thereby easily leading to the side center starting lithium precipitation to gradually diffuse, and the lithium dendrite formed will not only cause the thickness of the electric core to increase, but also will cause the safety risk of internal short circuit caused by puncturing the diaphragm.
[0003] The side lithium precipitation problem is a common problem in the industry and is also a winding structure high-rate charging problem, which greatly limits the development of high-energy high-rate winding type electric core. At the same time, the irreversible expansion generated in the charge-discharge cycle process of the silicon system electric core causes the metal fatigue of the positive and negative electrode current collectors to break and causes safety risks, especially at the corner of the soft package battery. The diaphragm pore forming can improve the corner fracture to some extent, but the uneven stress on the side will consume the uneven pores and cause local poor contact of the positive and negative plates.
[0004] Therefore, an innovative technical solution is needed to improve the plate fracture and improve the cycle performance of the battery. UTILITY MODEL CONTENTS
[0005] The utility model aims at: in view of the prior art's insufficient, provide a kind of electric core, can improve the plate fracture and improve the cycle performance of the battery.
[0006] In order to realize the above-mentioned purpose, the utility model adopts the following technical solutions:
[0007] An electric core, comprising an electric core body and an elastic member disposed outside a corner of the electric core body, the elastic member comprising a first elastic portion and a second elastic portion connected to the first elastic portion, the first elastic portion and the second elastic portion being symmetrically disposed along the central axis of the corner.
[0008] Preferably, the elastic member further comprises a connecting portion, and the first elastic portion is connected to the second elastic portion through the connecting portion.
[0009] Preferably, the elastic member is a porous elastic member.
[0010] Preferably, the first elastic portion and the second elastic portion are both arc-shaped structures.
[0011] Preferably, the elastic member is provided with an adhesive layer on the surface, and the elastic member is pasted to the corner of the electric core body through the adhesive layer.
[0012] Preferably, the CB value of the corner part of the electric core body is 1.05-1.2.
[0013] Preferably, the cell body is formed by stacking and winding the positive electrode sheet, the separator and the negative electrode sheet in sequence.
[0014] The negative electrode sheet comprises a negative electrode current collector and a first active material layer arranged on the negative electrode current collector; the negative electrode sheet is further provided with a second active material layer at the corner of the cell, and the second active material layer is coated on the outer surface of the first active material layer.
[0015] The length L1 of the elastic member and the length L2 of the second active material layer satisfy the relationship: L1 / L2 = 1.0-1.02.
[0016] The width W1 of the elastic member and the width W2 of the second active material layer satisfy the relationship: W1 / W2 = 1.0-1.02.
[0017] Preferably, the thickness of the first elastic part and the second elastic part is 3-1000 microns.
[0018] Preferably, the thickness of the connecting part is 1-990 microns.
[0019] In addition, the utility model also provides a kind of battery comprising cell and the shell of encapsulating cell, and the cell is the cell described above.
[0020] Compared with prior art, the utility model has the beneficial effects that:
[0021] 1) the cell corner of the utility model is provided with elastic member, the elastic member can adjust cell stress in circulation process, solves the problem that positive electrode sheet and negative electrode sheet cannot be effectively contacted due to volume expansion in circulation process, and reduces the cycle performance, while avoiding the fracture of electrode sheet in circulation process.
[0022] 2) the elastic member of the utility model has porous structure, can offset the stress generated by volume expansion in cell circulation process, can increase electrolyte adsorption amount, under the stress of charge and discharge, electrolyte flows into electrode sheet from the material, to supplement the problem of insufficient cell electrode liquid, to further improve cycle life.
[0023] (3) the CB value of the corner part of the cell body of the utility model is 1.05-1.2, which can improve the problem of lithium precipitation due to mismatch of side CB value in cell circulation process. BRIEF DESCRIPTION OF DRAWINGS
[0024] Figure 1 It is the structure schematic view of the cell of one embodiment of the utility model.
[0025] Figure 2 It is the structure schematic view of the battery of one embodiment of the utility model.
[0026] 1 - the cell body; 11 - the positive plate; 12 - the diaphragm; 13 - the negative plate; 2 - the elastic member; 21 - the first elastic part; 22 - the second elastic part; 23 - the connecting part; 24 - the adhesive layer; 3 - the shell. DETAILED DESCRIPTION
[0027] In order to make the technical scheme and advantages of the utility model clearer, the utility model and its beneficial effects will be described in further detail below in combination with specific implementation manners and the drawings of the specification, but the implementation manners of the utility model are not limited to this.
[0028] The terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the utility model, the meaning of "multiple" is two or more, unless otherwise explicitly specified.
[0029] In order to make the technical scheme and advantages of the utility model clearer, the utility model and its beneficial effects will be described in further detail below in combination with specific implementation manners and the drawings of the specification, but the implementation manners of the utility model are not limited to this.
[0030] As shown in Figure 1 According to the first aspect of the present application, the present application aims to provide a cell, comprising: a cell body 1 and an elastic member 2 arranged outside the corner of the cell body 1, the elastic member 2 comprising a first elastic part 21 and a second elastic part 22 connected with the first elastic part 21, the first elastic part 21 and the second elastic part 22 being symmetrically arranged along the central axis of the corner.
[0031] The elastic member can adjust the stress of the cell during the cycle process, solve the problem that the positive plate and the negative plate cannot be effectively contacted due to the volume expansion of the cell during the cycle process, and avoid the fracture of the plate during the cycle process.
[0032] In some embodiments, the elastic member 2 is one of polypropylene, polyethylene, polyurethane, poly-p-phenyleneterephthalamide, polyvinylidene fluoride, polystyrene, polyperfluoroethylene, polymethyl methacrylate, polyacrylonitrile, polystyrene-co-butyl acrylate, polyimide and polyacrylate.
[0033] In some embodiments, the elastic member 2 further comprises a connecting part 23, and the first elastic part 21 is connected with the second elastic part 22 through the connecting part 23.
[0034] In some embodiments, the first elastic part 21 and the second elastic part 22 are both in arc-shaped structure.
[0035] In some embodiments, the elastic member is an elastic member with a porous structure. The elastic member with a porous structure can offset the stress generated by the volume expansion during the cycle of the battery cell, can increase the adsorption amount of electrolyte, and can supplement the electrolyte in the electrode under the stress of charging and discharging, thereby further improving the cycle life.
[0036] In some embodiments, the surface of the elastic member 2 is provided with an adhesive layer 24, and the elastic member 2 is attached to the corner of the battery cell body 1 through the adhesive layer 24.
[0037] In some embodiments, the CB value of the corner part of the battery cell body 1 is 1.05-1.2. Increasing the CB value of the corner part of the battery cell body can improve the lithium precipitation problem caused by the mismatch of the side CB value during the cycle of the battery cell.
[0038] In some embodiments, the battery cell body 1 is formed by sequentially stacking and winding the positive electrode sheet 11, the separator film 12, and the negative electrode sheet 13; the negative electrode sheet 13 includes a negative electrode current collector and a first active material layer disposed on the negative electrode current collector; the negative electrode sheet 13 further includes a second active material layer disposed at the corner of the battery cell, and the second active material layer is coated on the outer surface of the first active material layer.
[0039] The length L1 of the elastic member 2 and the length L2 of the second active material layer satisfy the relationship: L1 / L2 = 1.0-1.02, for example, which can be 1.0, 1.01, or 1.02.
[0040] If L1 / L2 is too small, the corner electrode sheet cannot be completely wrapped from the width direction of the electrode sheet, and the desired effect cannot be achieved; if L1 / L2 is too large, the space utilization rate is low, and the elastic member is also wasted.
[0041] The width W1 of the elastic member 2 and the width W2 of the second active material layer satisfy the relationship: W1 / W2 = 1.0-1.02, for example, which can be 1.0, 1.01, or 1.02.
[0042] If W1 / W2 is too small, the corner of the outer ring of the battery cell cannot be wrapped, and the desired effect cannot be achieved; if W1 / W2 is too large, the elastic pad will be on the battery cell body, increasing the thickness of the battery cell, making the battery cell uneven, and also wasting the elastic member, reducing the space utilization rate.
[0043] The values of L1, L2, W1, and W2 satisfy the above relationship, which can adapt the size between the elastic member and the second active material layer, and further improve the cycle performance of the battery. In some embodiments, the first active material and the second active material can be one or more of, but not limited to, graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials, lithium titanate, or other metals that can form alloys with lithium.
[0044] wherein the graphite can be selected from one or more of artificial graphite, natural graphite, and modified graphite; the silicon-based material can be selected from one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon alloys; and the tin-based material can be selected from one or more of elemental tin, tin oxide compounds, tin alloys.
[0045] In some embodiments, the compression rate of the elastic member 2 is 10%-60%, for example, can be 10%, 20%, 30%, 40%, 50%, or 60%.
[0046] In some embodiments, the resilience rate of the elastic member 2 is 30%-90%, for example, can be 30%, 40%, 50%, 60%, 70%, 80%, or 90%.
[0047] In some embodiments, the tensile strength of the elastic member 2 is 0.5-10 MPa, for example, can be 0.5 MPa, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, or 10 MPa.
[0048] If the compression rate is too low, the corresponding elastic effect cannot be achieved, and the electrolyte in the elastic pad cannot be squeezed out to supplement the electrode plate of the battery cell. In addition, a low compression rate will result in insufficient stress release of the electrode plate. If the compression rate is too high, the elastic force is insufficient, and the corresponding elastic effect cannot be achieved.
[0049] If the resilience rate is too low, the elastic force is insufficient, and the elastic force cannot be satisfied. If the resilience rate is too high, the force is too large, which will exert a counteracting force on the electrode plate of the battery cell, causing deterioration.
[0050] If the tensile strength is too small, it is easy to break and cannot function. If the tensile strength is too large, the material will be too rigid and the elasticity will be insufficient.
[0051] In some embodiments, the thickness of the first elastic portion 21 and the second elastic portion 22 is 3 μm-1000 μm, for example, can be 3 μm, 10 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, or 1000 μm.
[0052] In some embodiments, the thickness of the connecting portion 23 is 1 μm-990 μm, for example, can be 1 μm, 10 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, or 990 μm.
[0053] As Figure 2As shown, according to the second aspect of the present application, the present application provides a secondary battery comprising a cell and a housing 3 encapsulating the cell, the cell being the cell as described above.
[0054] The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material, which can be one or more combinations of compounds as represented by LiaNixCoyMzO2-bNb (wherein 0.95≤a≤1.2, x>0, y≥0, z≥0, and x+y+z=1, 0≤b≤1, M is selected from one or more combinations of Mn, Al, and N is selected from one or more combinations of F, P, S), but not limited to, and can also be one or more combinations of LiCoO2, LiNiO2, LiVO2, LiCrO2, LiMn2O4, LiCoMnO4, Li2NiMn3O8, LiNi 0.5 Mn 1.5 O4, LiCoPO4, LiMnPO4, LiFePO4, LiNiPO4, LiCoFSO4, CuS2, FeS2, MoS2, NiS, TiS2, etc. The positive electrode active material can also be subjected to a modification treatment, and methods for modifying the positive electrode active material are known to those skilled in the art, for example, the positive electrode active material can be modified by coating, doping, etc., and the materials used for the modification treatment can be one or more combinations of Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, W, etc., but not limited to. The positive electrode current collector is generally a structure or part that collects current, and can be various materials suitable for use as a positive electrode current collector for lithium ion batteries in the art, for example, the positive electrode current collector can be one or more combinations of metal foils, etc., but not limited to, and more specifically can be one or more combinations of aluminum foils, etc., but not limited to.
[0055] The separator can be various materials suitable for use as a separator for lithium ion batteries in the art, for example, can be one or more combinations of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, and natural fibers, etc., but not limited to.
[0056] The lithium ion battery further comprises an electrolyte, the electrolyte comprising an organic solvent, an electrolyte lithium salt and an additive. The electrolyte lithium salt can be LiPF6 and / or LiBOB used in a high-temperature electrolyte, at least one of LiBF4, LiBOB and LiPF6 used in a low-temperature electrolyte, at least one of LiBF4, LiBOB, LiPF6 and LiTFSI used in an overcharge-preventing electrolyte, and at least one of LiClO4, LiAsF6, LiCF3SO3 and LiN(CF3SO2)2. The organic solvent can be a cyclic carbonate including PC and EC, a chain carbonate including DFC, DMC or EMC, and a carboxylic acid ester including MF, MA, EA and MP. The additive includes, but is not limited to, at least one of a film-forming additive, a conductive additive, a flame-retardant additive, an overcharge-preventing additive, an additive for controlling the contents of H2O and HF in the electrolyte, an additive for improving low-temperature performance, and a multifunctional additive.
[0057] Embodiment 1
[0058] (1) Preparation of the positive electrode sheet
[0059] After the positive electrode material lithium cobaltate, the conductive agent acetylene black (SP) and the binder polyvinylidene fluoride (PVDF) are fully stirred and uniformly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 98:1.2:0.8, they are coated on an Al foil, dried, rolled, and then slitted to obtain the positive electrode sheet.
[0060] (2) Preparation of the negative electrode sheet
[0061] After the negative electrode material, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR) and the thickening agent sodium carboxymethyl cellulose (CMC) are fully stirred and uniformly mixed in a deionized water solvent system at a mass ratio of 98.1:0.5:0.7:0.7, they are first coated on a Cu foil with a CB value of 1.045 corresponding to the coating, dried, rolled, and then secondarily coated with a coating corresponding to an increased CB value at the corner position of the corresponding battery cell, dried and rolled, and then slitted to obtain the negative electrode sheet.
[0062] The CB value at the corner position is 1.05.
[0063] (3) Preparation of the separator
[0064] The separator is an alumina ceramic polyethylene (PE) porous polymer film.
[0065] (4) Preparation of the electrolyte
[0066] A solution prepared by mixing (vinylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC): propyl propionate (PP): vinylene carbonate (VC)) = 25:25:15:31:4 by mass ratio as a non-aqueous organic solvent, and lithium salt LiPF6 with the non-aqueous organic solvent in a mass ratio of 8:92 is used as the electrolyte of the lithium battery.
[0067] (5) Preparation of the battery
[0068] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, with the separator between the positive electrode sheet and the negative electrode sheet to play a safe isolation role, and the stack is wound to obtain a battery cell. An elastic member is attached to the corner of the battery cell, the battery cell is placed in a packaging shell, electrolyte is injected and packaged to obtain a lithium battery.
[0069] The ratio L1 / L2 of the length L1 of the elastic member to the length L2 of the second active material layer is 1.0, and the ratio W1 / W2 of the width W1 of the elastic member to the width W2 of the second active material layer is 1.0; the compression rate of the elastic member is 10%, the resilience rate is 90%, and the tensile strength is 0.5 MPa; the thickness of the first elastic part and the second elastic part is 3 μm; and the thickness of the connecting part is 1 μm.
[0070] The preparation methods of Examples 2-10 and Comparative Examples 1-3 are the same as that of Example 1, except that the CB value of the corner part of the battery cell body and the parameters of the elastic member are different, and the specific parameters are shown in Table 1.
[0071] Table 1
[0072]
[0073]
[0074] The lithium ion batteries prepared in the examples and comparative examples are respectively subjected to the following performance tests:
[0075] (1) Cycle performance test: the cycle test is performed at an ambient temperature of 25°C on a new power test cabinet, and the steps are as follows: 1. resting: 5 min; 2. charging at 0.5C constant current and constant voltage to 4.53V, with a cutoff current of 0.02C; 3. resting: 5 min; 4. discharging at 0.5C constant current, with a cutoff voltage of 3.0V; 5. repeating steps 1 to 4 for 1500 cycles.
[0076] (2) Thickness expansion rate test: 1. the left hand holds the handle of the thickness gauge, and the right hand takes the battery cell from the blister box; 2. the battery cell is placed in the middle position of the flat plate, with the tabs just leveled with the upper edge of the pressure plate; 3. the initial thickness is measured using a 600ppg; 4. the thickness after cycling is measured after 1500 cycles according to the above steps. The thickness expansion rate = (thickness after cycling-initial thickness)*100%.
[0077] (3) Lithium precipitation test of pole piece: after the battery cell is cycled at room temperature, the battery cell is charged at 0.5C current constant current constant voltage to 4.53V, and then is disassembled in a disassembly room with temperature of 10℃-30℃ and humidity of 0%-10%, the interface of the negative pole piece is observed during disassembly, and the battery cell and the pole piece are photographed and retained.
[0078] The performance test results are shown in Table 2.
[0079] Table 2
[0080]
[0081]
[0082] From the data comparison of Examples 1-10 and Comparative Examples 1-3 in Table 2, it can be seen that when the CB value of the corner part of the battery cell body is 1.10, the thickness of the first elastic part and the second elastic part is 300μm, the thickness of the connecting part is 100μm, the compression rate of the elastic member is 30%, the resilience rate is 50%, and the tensile strength is 5.0MPa, the cycle performance of the battery is the best, and the thickness expansion rate is the smallest.
[0083] From the data comparison of Examples 1, 3 and Comparative Example 2, it can be seen that when the CB value increases, the cycle life of the battery increases, and the thickness expansion rate increases, and when the CB value is less than the set range, the lithium precipitation degree of the pole piece is obvious.
[0084] From the data comparison of Examples 1-10 and Comparative Examples 1, 3, it can be seen that when the battery cell does not contain the elastic member, it is difficult to adjust the stress of the battery cell during the cycle process, which leads to that the positive pole piece and the negative pole piece cannot be effectively contacted, and reduces the cycle life and also leads to the fracture of the pole piece.
[0085] According to the disclosure and teaching of the above description, those skilled in the art of the present application can also make changes and modifications to the above embodiments. Therefore, the present application is not limited to the above specific embodiments, and any obvious improvements, replacements or modifications made by those skilled in the art on the basis of the present application all belong to the protection scope of the present application. In addition, although some specific terms are used in the present specification, these terms are only for convenience of explanation and do not constitute any limitation on the present application.
Claims
1. An electric cell, characterized by, The elastic member comprises a first elastic part and a second elastic part connected with the first elastic part, and the first elastic part and the second elastic part are symmetrically arranged along the central axis of the corner.
2. The electric cell of claim 1, wherein, The elastic member further comprises a connecting part, and the first elastic part is connected with the second elastic part through the connecting part.
3. The electric cell of claim 1, wherein, The first elastic part and the second elastic part are both in arc structure.
4. The electric cell of claim 1, wherein, The elastic member is a porous elastic member.
5. The electric cell of claim 1, wherein, The elastic member is pasted to the corner of the battery cell body through the adhesive layer.
6. The electric cell of claim 1, wherein, The CB value of the corner part of the battery cell body is 1.05-1.
2.
7. The electric cell of claim 1, wherein, The battery cell body is formed by sequentially stacking and winding a positive electrode sheet, a separator and a negative electrode sheet. The negative electrode sheet comprises a negative electrode current collector and a first active material layer arranged on the negative electrode current collector; the negative electrode sheet further comprises a second active material layer arranged at the corner of the battery cell, and the second active material layer is coated on the outer surface of the first active material layer. The length L1 of the elastic member and the length L2 of the second active material layer satisfy the relationship: L1 / L2=1.0-1.
02. The width W1 of the elastic member and the width W2 of the second active material layer satisfy the relationship: W1 / W2=1.0-1.
02.
8. The electric cell of claim 1, wherein, The compression rate of the elastic member is 10%-60%, the resilience rate is 30%-90%, and the tensile strength is 0.5-10 MPa.
9. The electric cell of claim 1, wherein, The thickness of the first elastic part and the second elastic part is 3 μm-1000 μm, and the thickness of the connecting part is 1 μm-990 μm.
10. A battery comprising a cell and a case that encloses the cell, characterized in that, The battery cell is the battery cell according to any one of claims 1-9.