Battery cell structure and composite diaphragm for battery cell

Abstract

The utility model discloses a battery cell structure and a composite diaphragm for a battery cell. The battery cell structure comprises a positive pole piece, a negative pole piece and the composite diaphragm, the positive pole piece comprises a positive material section and a positive empty foil area arranged at at least one end of the positive material section; the negative pole piece comprises a negative pole material section and a negative pole empty foil area arranged at at least one end of the negative pole material section; the composite diaphragm comprises an extension protection section and a contraction protection section arranged at at least one end of the extension protection section; the positive empty foil area and the negative empty foil area at least partially coincide with the contraction protection section, and the negative material section, the positive material section and the extension protection section at least partially coincide; the extension protection section is arranged corresponding to the material area and is made of a material which is hot-ductility or does not rebound after being stressed; the shrinkage protection section is arranged corresponding to the empty foil part and is made of a heat-shrinkable material or a material which extends and rebounds after being stressed; the short-circuit probability of the material area is reduced when the battery is punctured, so that more short circuits occur in the empty foil part of the pole piece, the risk of fire explosion of the battery is reduced, and the safety performance of the battery is improved.

Description

Technical Field

[0001] This utility model relates to the field of lithium-ion battery technology, and in particular to a cell structure and a composite separator for battery cells. Background Technology

[0002] Lithium-ion batteries have been widely used in civilian and power applications. Existing lithium-ion batteries have complex internal structures, involving multiple layers of materials such as positive electrodes, negative electrodes, and separators tightly wound or stacked. When a lithium-ion battery is punctured by a foreign object, the object can penetrate the electrodes and separator, causing a short circuit as the positive and negative electrodes come into contact. Once an internal short circuit occurs, the entire battery will discharge and release energy through the short circuit point, and the rapid release of a large amount of heat can easily trigger thermal runaway. Due to the strong exothermic nature of the internal chemical reactions, once thermal runaway is triggered, the temperature rises rapidly, potentially leading to battery fire or explosion, causing serious safety accidents. Therefore, there is an urgent need for a solution to reduce the risk of fire and explosion in lithium-ion batteries and address these issues. Utility Model Content

[0003] This invention provides a cell structure and a composite separator for battery cells, aiming to reduce the risk of fire and explosion caused by internal short circuits when lithium-ion batteries are punctured by foreign objects.

[0004] To achieve the above objectives, this utility model proposes a battery cell structure, including a positive electrode plate, a negative electrode plate, and a composite separator;

[0005] The positive electrode sheet includes a positive electrode material section and a positive electrode empty foil section disposed at at least one end of the positive electrode material section;

[0006] The negative electrode sheet includes a negative electrode material section and a negative electrode empty foil section disposed at at least one end of the negative electrode material section;

[0007] The composite diaphragm includes an extended protection section and a contraction protection section disposed at at least one end of the extended protection section;

[0008] The positive electrode empty foil region and the negative electrode empty foil region both overlap at least partially with the shrinkage protection section, and the negative electrode material section and the positive electrode material section overlap at least partially with the extension protection section.

[0009] In some embodiments, both ends of the positive electrode material section are provided with positive electrode empty foil regions, namely a first positive electrode empty foil region and a second positive electrode empty foil region; the length of the first positive electrode empty foil region is less than the length of the second positive electrode empty foil region.

[0010] Both ends of the negative electrode material section are provided with negative electrode empty foil areas, namely a first negative electrode empty foil area and a second negative electrode empty foil area; the length of the first negative electrode empty foil area is less than the length of the second negative electrode empty foil area;

[0011] Both ends of the extended protection section are provided with the contraction protection section, namely a first contraction protection section and a second contraction protection section; the length of the first contraction protection section is less than the length of the second contraction protection section.

[0012] In some embodiments, there are two composite membranes, namely a first composite membrane and a second composite membrane;

[0013] The first composite separator, the negative electrode sheet, the second composite separator, and the positive electrode sheet are sequentially arranged and wound from the inside to the outside to form a core;

[0014] The core includes a first protective section, a functional section, and a second protective section arranged sequentially from the inside to the outside;

[0015] The first protective section includes the first positive electrode empty foil region, the first negative electrode empty foil region, the first shrinkage protection section of the first composite separator, and the first shrinkage protection section of the second composite separator;

[0016] The second protection section includes the second positive electrode empty foil region, the second negative electrode empty foil region, the second shrinkage protection section of the first composite membrane, and the second shrinkage protection section of the second composite membrane;

[0017] The functional segments include the positive electrode material segment, the negative electrode material segment, the extension protection segment of the first composite separator, and the extension protection segment of the second composite separator.

[0018] In some embodiments, the length of the first protective segment is at least around the innermost layer of the core.

[0019] In some embodiments, the length of the second protective segment is at least around the outermost layer of the core.

[0020] In some embodiments, the length of the extended protection section is greater than the length of the negative electrode section and the positive electrode section.

[0021] In some embodiments, the material used for the extended protective segment is at least one of polyimide and polyetheretherketone;

[0022] The material used in the shrinkage protection section is at least one of acrylonitrile-butadiene-styrene copolymer, polyethylene, polyvinyl chloride, and polytetrafluoroethylene.

[0023] This utility model also proposes a composite separator for battery cells, comprising:

[0024] Extended protection section;

[0025] A contraction protection section is provided at at least one end of the extension protection section;

[0026] The width of the shrinkage protection section is equal to the width of the extension protection section, and the length of the shrinkage protection section is less than the length of the extension protection section.

[0027] In some embodiments, both ends of the extended protection section are provided with the contraction protection section, namely a first contraction protection section and a second contraction protection section; the length of the first contraction protection section is less than the length of the second contraction protection section.

[0028] In some embodiments, the material used for the extended protective segment is at least one of polyimide and polyetheretherketone;

[0029] The material used in the shrinkage protection section is at least one of acrylonitrile-butadiene-styrene copolymer, polyethylene, polyvinyl chloride, and polytetrafluoroethylene.

[0030] The beneficial effects of this utility model are as follows: The composite separator in this utility model provides extension protection sections for the positive and negative electrode material areas of the corresponding electrode sheet. These extension protection sections are made of materials that are thermally malleable or do not spring back after being stretched under force. Conversely, shrinkage protection sections are provided for the positive and negative electrode empty foil areas of the corresponding electrode sheet. These shrinkage protection sections are made of materials that are thermally shrinkable or spring back after being stretched under force. Regardless of which part of the electrode sheet is punctured, the probability of short circuits occurring in the electrode material area can be reduced, causing short circuits to occur more frequently in the empty foil areas at the ends of the positive and negative electrode sheets. Since the current collector resistance is less than the material area resistance, the empty foil area will share most of the current, reducing the heat in the electrode material area. This utility model does not require additional additives or protective coatings to ensure that short circuits occur more frequently in the empty foil areas of the current collector, reducing the reaction heat in the electrode material area, lowering the risk of battery fire and explosion, and improving battery safety performance. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the battery cell structure of this utility model;

[0032] Figure 2 This is a schematic cross-sectional view of the overall structure of the battery cell of this utility model;

[0033] In the diagram: 100, battery cell; 100a, first protection section; 100b, functional section; 100c, second protection section; 1, positive electrode plate; 11, positive electrode material section; 12, positive electrode empty foil area; 12a, first positive electrode empty foil area; 12b, second positive electrode empty foil area; 2, negative electrode plate; 21, negative electrode material section; 22, negative electrode empty foil area; 22a, first negative electrode empty foil area; 22b, second negative electrode empty foil area; 3, composite separator; 3a, first composite separator; 3b, second composite separator; 31, extension protection section; 32, shrinkage protection section; 32a, first shrinkage protection section; 32b, second shrinkage protection section. Detailed Implementation

[0034] The solutions in the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.

[0035] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0036] It should also be noted that when a component is described as "fixed to" or "set on" another component, it can be directly on the other component or there may be an intervening component present. When a component is described as "connected to" another component, it can be directly connected to the other component or there may be an intervening component present.

[0037] Furthermore, the use of terms such as "first" and "second" in this utility model is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this utility model.

[0038] Example 1

[0039] This embodiment proposes a battery cell structure, referring to... Figures 1 to 2 It includes a positive electrode 1, a negative electrode 2 and a composite separator 3;

[0040] The positive electrode 1 includes a positive electrode material section 11 and a positive electrode empty foil section 12 disposed at at least one end of the positive electrode material section 11;

[0041] The negative electrode 2 includes a negative electrode material section 21 and a negative electrode empty foil section 22 disposed at at least one end of the negative electrode material section 21;

[0042] The composite diaphragm 3 includes an extension protection section 31 and a shrinkage protection section 32 disposed at at least one end of the extension protection section 31;

[0043] The positive electrode empty foil region 12 and the negative electrode empty foil region 22 both overlap at least partially with the shrinkage protection section 32, and the negative electrode material section 21 and the positive electrode material section 11 overlap at least partially with the extension protection section 31.

[0044] In this embodiment, empty foil sections are reserved on the positive electrode 1 and the negative electrode 2, and a composite separator 3 is arranged along the length direction of the positive electrode 1 and the negative electrode 2. An extension protection section 31 is provided on the composite separator 3 corresponding to the material area of ​​the electrode. The extension protection section 31 covers and isolates the positive electrode material area 11 and the negative electrode material area 21. The extension protection section 31 is made of a material that is thermally malleable or does not spring back after being stretched under force. If the battery is punctured and heats up, the extension protection section 31 will extend under heat or force, thus isolating the material areas on the positive electrode 1 and the negative electrode 2 and preventing short circuits within the material areas. A shrinkage protection section 32 is provided on the composite separator 3 corresponding to the positive electrode empty foil area 12 and the negative electrode empty foil area 22 of the electrode. The protection section 32 is made of a material that is thermally shrinkable or elastic after being stretched under stress. If the battery heats up after being punctured, the shrinkage protection section 32 will shrink due to heat or spring back under stress, which can cause the positive electrode empty foil area 12 of the positive electrode 1 and the negative electrode empty foil area 22 of the negative electrode 2 to come into contact with each other and cause a short circuit. Since the current collector resistance is less than the material area resistance, the empty foil area will share most of the current, reducing the heat in the electrode material area. With this design, no matter which part of the battery is punctured, the probability of a short circuit in the electrode material area can be greatly reduced, so that the short circuit occurs more often in the empty foil area of ​​the current collector, reducing the reaction heat of the electrode material area, reducing the risk of battery fire and explosion, and improving the safety performance of the battery.

[0045] Furthermore, both ends of the positive electrode material section 11 are provided with positive electrode empty foil regions 12, namely a first positive electrode empty foil region 12a and a second positive electrode empty foil region 12b; the length of the first positive electrode empty foil region 12a is less than the length of the second positive electrode empty foil region 12b.

[0046] Both ends of the negative electrode material section 21 are provided with negative electrode empty foil regions 22, namely a first negative electrode empty foil region 22a and a second negative electrode empty foil region 22b; the length of the first negative electrode empty foil region 22a is less than the length of the second negative electrode empty foil region 22b.

[0047] Both ends of the extended protection section 31 are provided with contraction protection sections 32, namely a first contraction protection section 32a and a second contraction protection section 32b; the length of the first contraction protection section 32a is less than the length of the second contraction protection section 32b.

[0048] In this embodiment, both ends of the positive electrode 1 and the negative electrode 2 are provided with empty foil areas, and the length of the empty foil area at the tail of the electrode is greater than the length of the empty foil area at the head of the electrode, which can further reduce the probability of short circuits occurring in the electrode material area, so that short circuits occur more often in the empty foil area of ​​the current collector; correspondingly, the length of the shrinkage protection section 32 at the tail of the composite separator 3 is also greater than the length of the shrinkage protection section 32 at the head of the composite separator 3.

[0049] Furthermore, there are two composite membranes 3, namely a first composite membrane 3a and a second composite membrane 3b;

[0050] The first composite diaphragm 3a, the negative electrode 2, the second composite diaphragm 3b, and the positive electrode 1 are arranged and wound from the inside to the outside to form a core;

[0051] The core includes a first protective section 100a, a functional section 100b, and a second protective section 100c arranged sequentially from the inside to the outside.

[0052] The first protection section 100a includes a first positive electrode empty foil region 12a, a first negative electrode empty foil region 22a, a first shrinkage protection section 32a of the first composite membrane 3a, and a first shrinkage protection section 32a of the second composite membrane 3b.

[0053] The second protection section 100c includes a second positive electrode empty foil region 12b, a second negative electrode empty foil region 22b, a second shrinkage protection section 32b of the first composite membrane 3a, and a second shrinkage protection section 32b of the second composite membrane 3b.

[0054] Functional segment 100b includes positive electrode material segment 11, negative electrode material segment 21, extension protection segment 31 of the first composite separator 3a, and extension protection segment 3 of the second composite separator 3b.

[0055] In the battery cell 100 of this embodiment, the first composite separator 3a, the negative electrode 2, the second composite separator 3b, and the positive electrode 1 are sequentially wound from the inside to the outside to form a core. The core includes protective sections distributed on the outermost and innermost rings, and a functional section 100b in the middle. The protective sections include the empty foil portions of the positive electrode 1 and the negative electrode 2, and the shrinkage protection section 32 of the composite separator 3. The functional section 100b includes the material areas of the positive electrode 1 and the negative electrode 2, and the extension protection section 31 of the composite separator 3. If the battery is punctured and heated, the shrinkage protection section 32 in the protective section shrinks due to heat or rebounds under force, and the composite separator 3 shrinks, exposing the core. The empty foil portions of the positive and negative electrodes allow the empty foil area 12 of the positive electrode 1 and the empty foil area 22 of the negative electrode 2 to come into contact with each other, causing a short circuit. The extended protection section 31 extends under heat or force, and the composite separator 3 extends outward, which can isolate and cover the material areas on the positive electrode 1 and the negative electrode 2, preventing short circuits inside the material areas. The current collector resistance is less than the material area resistance, and the empty foil area will share most of the current, reducing the heat in the electrode material areas. This setting can greatly reduce the probability of short circuits in the electrode material areas, making short circuits occur more often in the empty foil area of ​​the current collector, reducing the risk of battery fire and explosion, and improving the battery safety performance.

[0056] Furthermore, the length of the first protective section 100a is at least one loop around the innermost layer of the core; the length of the first protective section 100a located at the innermost loop of the core must be at least one loop around the innermost layer of the core, leaving a safe length to reduce the probability of short circuit in the material area of ​​the inner positive electrode 1 and negative electrode 2.

[0057] Furthermore, the length of the second protective section 100c is at least one full turn around the outermost layer of the core; the length of the second protective section 100c located on the outermost ring of the core must be at least one full turn around the outermost layer of the core to reserve a safe length. When the battery is punctured, the outermost second protective section 100c can play a protective role first, so that the short circuit occurs in the empty foil area, distributing most of the current and reducing the heat in the electrode material area.

[0058] Furthermore, the length of the extended protection section 31 is greater than the length of the negative electrode section 21 and the positive electrode section 11; the length of the contracted protection section 32 must be greater than the length of the negative electrode section 21 to ensure that it covers and isolates the positive electrode section and the negative electrode section.

[0059] Furthermore, the material used in the extended protective section 31 is at least one of polyimide (PI) and polyetheretherketone (PEEK); their common characteristics are that they are heat-shrinkable or that they will spring back after being stretched under stress.

[0060] The shrinkage protection section 32 is made of at least one of acrylonitrile-butadiene-styrene copolymer (ABS), polyethylene (PE), polyvinyl chloride (PVC), and polytetrafluoroethylene (PTEE); their common characteristic is that they stretch when heated or stretched under force without rebounding.

[0061] Example 2

[0062] This embodiment proposes a composite separator for battery cells, comprising: an extended protection section;

[0063] A contraction protection section is provided at at least one end of the extension protection section;

[0064] The width of the contraction protection section is equal to the width of the extension protection section, and the length of the contraction protection section is less than the length of the extension protection section.

[0065] Furthermore, both ends of the extended protection section are provided with contraction protection sections, namely the first contraction protection section and the second contraction protection section; the length of the first contraction protection section is less than the length of the second contraction protection section.

[0066] Furthermore, the material used in the extended protective section is at least one of polyimide and polyetheretherketone;

[0067] The material used in the shrinkage protection section is at least one of acrylonitrile-butadiene-styrene copolymer, polyethylene, polyvinyl chloride, and polytetrafluoroethylene.

[0068] The above description is only a part or preferred embodiment of this utility model. Neither the text nor the drawings should limit the scope of protection of this utility model. All equivalent structural transformations made using the content of this utility model specification and drawings under the overall concept of this utility model, or direct / indirect applications in other related technical fields, are included within the scope of protection of this utility model.

Claims

1. A battery cell structure, characterized in that, Includes positive electrode plates, negative electrode plates, and composite separators; The positive electrode sheet includes a positive electrode material section and a positive electrode empty foil section disposed at at least one end of the positive electrode material section; The negative electrode sheet includes a negative electrode material section and a negative electrode empty foil section disposed at at least one end of the negative electrode material section; The composite diaphragm includes an extended protection section and a contraction protection section disposed at at least one end of the extended protection section; The positive electrode empty foil region and the negative electrode empty foil region both overlap at least partially with the shrinkage protection section, and the negative electrode material section and the positive electrode material section overlap at least partially with the extension protection section.

2. The cell structure according to claim 1, characterized in that, Both ends of the positive electrode material section are provided with positive electrode empty foil regions, namely a first positive electrode empty foil region and a second positive electrode empty foil region; the length of the first positive electrode empty foil region is less than the length of the second positive electrode empty foil region; Both ends of the negative electrode material section are provided with negative electrode empty foil areas, namely a first negative electrode empty foil area and a second negative electrode empty foil area; the length of the first negative electrode empty foil area is less than the length of the second negative electrode empty foil area; Both ends of the extended protection section are provided with the contraction protection section, namely a first contraction protection section and a second contraction protection section; the length of the first contraction protection section is less than the length of the second contraction protection section.

3. The cell structure according to claim 2, characterized in that, There are two composite membranes, namely a first composite membrane and a second composite membrane; The first composite separator, the negative electrode sheet, the second composite separator, and the positive electrode sheet are sequentially arranged and wound from the inside to the outside to form a core; The core includes a first protective section, a functional section, and a second protective section arranged sequentially from the inside to the outside; The first protective section includes the first positive electrode empty foil region, the first negative electrode empty foil region, the first shrinkage protection section of the first composite separator, and the first shrinkage protection section of the second composite separator; The second protection section includes the second positive electrode empty foil region, the second negative electrode empty foil region, the second shrinkage protection section of the first composite membrane, and the second shrinkage protection section of the second composite membrane; The functional segments include the positive electrode material segment, the negative electrode material segment, the extension protection segment of the first composite separator, and the extension protection segment of the second composite separator.

4. The cell structure according to claim 3, characterized in that, The length of the first protective section is at least one revolution around the innermost layer of the core.

5. The cell structure according to claim 3, characterized in that, The length of the second protective section is at least one lap around the outermost layer of the core.

6. The cell structure according to claim 2, characterized in that, The length of the extended protection section is greater than the length of the negative electrode section and the positive electrode section.

7. The cell structure according to any one of claims 1 to 6, characterized in that, The material used in the extended protective section is at least one of polyimide and polyetheretherketone; The material used in the shrinkage protection section is at least one of acrylonitrile-butadiene-styrene copolymer, polyethylene, polyvinyl chloride, and polytetrafluoroethylene.

8. A composite separator for battery cells, characterized in that, include: Extended protection section; A contraction protection section is provided at at least one end of the extension protection section; The width of the shrinkage protection section is equal to the width of the extension protection section, and the length of the shrinkage protection section is less than the length of the extension protection section.

9. The composite separator for battery cells according to claim 8, characterized in that, Both ends of the extended protection section are provided with the contraction protection section, namely a first contraction protection section and a second contraction protection section; the length of the first contraction protection section is less than the length of the second contraction protection section.

10. The composite separator for battery cells according to claim 8 or 9, characterized in that, The material used in the extended protective section is at least one of polyimide and polyetheretherketone; The material used in the shrinkage protection section is at least one of acrylonitrile-butadiene-styrene copolymer, polyethylene, polyvinyl chloride, and polytetrafluoroethylene.

Images