Winding cell and lithium ion battery
By setting a local coating on the electrode of the wound cell to isolate the current collector from the electrode and reduce the contact between the electrolyte and the active material layer, the safety hazards of wound cells in the needle penetration test and hot box test are solved, the safety performance and test pass rate are improved, and the energy density loss is reduced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ZHUHAI COSMX BATTERY CO LTD
- Filing Date
- 2025-03-26
- Publication Date
- 2026-07-10
AI Technical Summary
There are safety hazards in nail penetration tests and hot box tests for wound battery cells, especially the problems of easy deformation of the external parts of the battery cell, internal short circuits, and heat generation from side reactions, which affect the test pass rate and safety performance.
A first coating and a second coating are provided in local areas on the first electrode of the wound cell to isolate the current collector from the electrode and reduce the contact between the electrolyte and the active material layer. The coating is provided at the winding end of the electrode to prevent short circuits and side reactions.
It improves the safety performance of wound cells, enhances the pass rate of needle penetration test and hot box test, reduces energy density loss, and maintains the basic electrical performance.
Smart Images
Figure CN224480957U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of battery technology, specifically to a wound battery cell and a lithium-ion battery. Background Technology
[0002] During nail penetration testing, the closer to the outer edge of the wound cell, the greater the deformation caused by the nail penetration test, and the more prone to internal short circuits. This can easily cause the wound cell to fail the nail penetration test, affecting its safety performance. Furthermore, during hot box testing, the outermost part of the wound cell heats up the fastest. The contact between the electrolyte and the active material of the positive electrode can easily lead to side reactions generating heat, further causing the hot box test to fail and creating potential safety hazards for the wound cell. Utility Model Content
[0003] In view of this, the present invention provides a wound cell and a lithium-ion battery to solve the problem of safety performance defects in wound cells.
[0004] In a first aspect, this utility model provides a wound battery cell, comprising a first electrode, a separator, and a second electrode stacked and wound together, wherein the first electrode and the second electrode have opposite polarities, and the first electrode comprises:
[0005] First current collector, first active material layer, first coating layer and second coating layer;
[0006] Along the winding direction of the battery cell, the first current collector sequentially includes a first region, a second region, and a third region;
[0007] The first current collector is located on both sides of the first region, and a first active material layer is provided thereon.
[0008] The first current collector is provided with a first active material layer and a first coating layer on both sides of the second region;
[0009] The first current collector is located on one side of the third region and is sequentially provided with a first coating, a first active material layer and a second coating;
[0010] A first coating located in the second region and / or the third region is disposed between the first active material layer and the first current collector;
[0011] Along the length of the first electrode, the lengths of both the first coating and the second coating are less than the length of the first active material layer.
[0012] Beneficial Effects: The wound battery cell provided by the embodiments of this utility model, by setting a first coating and a second coating on the first electrode, can isolate the contact between the first current collector and the second electrode, thereby preventing short circuits and improving the safety performance of the wound battery cell, making it more conducive to passing the needle penetration test; and it can also isolate the contact between the electrolyte and the first active material layer of the positive electrode, reducing heat generation from side reactions, improving the thermal safety performance of the battery cell, and making it more conducive to passing the hot box test. It can pass the needle penetration test and hot box test with minimal energy density loss, thereby improving the safety performance of the battery cell, increasing the pass rate of the needle penetration test and hot box test for large-capacity battery cells, and the energy density loss is extremely low, having almost no impact on the electrical performance of the battery cell. By dividing the first current collector into regions, the first coating and the second coating are both set in local areas, which can minimize energy density loss while meeting safety performance requirements. Along the length direction of the first electrode, the length of both the first coating and the second coating is less than the length of the first active material layer; therefore, it is not necessary to set the first coating and the second coating in the entire area of the first current collector.
[0013] In one alternative embodiment, the second coating is located on the side of the first current collector facing the inside of the wound cell; the second coating is located between the first active material layer of the first electrode and the separator.
[0014] Beneficial effects: By placing the second coating on the side of the first current collector facing the inside of the wound cell, the contact between the electrolyte and the first active material layer of the positive electrode can be separated, reducing heat generation from side reactions, improving the thermal safety performance of the cell, and making it easier to pass the hot box test; by placing the second coating between the first active material layer of the positive electrode and the separator, it is possible to ensure that the second coating separates the electrolyte from the first active material layer of the positive electrode, reducing heat generation from side reactions, improving the thermal safety performance of the cell, and making it easier to pass the hot box test.
[0015] In one optional embodiment, the length of the first active material layer on the first side of the first current collector is L4, and the length of the first active material layer on the second side of the first current collector is L5, satisfying: L5 < L4.
[0016] The first coating on the first side near the tail end of the first electrode plate and the first active material layer on the first side near the tail end of the first electrode plate are at least partially overlapped in projection; the first coating on the second side near the tail end of the first electrode plate and the first active material layer on the second side near the tail end of the first electrode plate are at least partially overlapped in projection.
[0017] The projections of the first coating on the first side near the first electrode end and the first coating on the second side near the first electrode end at least partially overlap;
[0018] The length of the first coating on the first side of the first current collector is L1, the length of the first coating on the second side of the first current collector is L2, and the length of the second coating is L3, satisfying: L2 < L1 and L3 < L1;
[0019] And / or, the value of L1 ranges from 100mm to 2000mm;
[0020] And / or, the value of L2 ranges from 50mm to 1500mm;
[0021] And / or, the value of L3 ranges from 50mm to 500mm.
[0022] Beneficial effects: By adopting this configuration, energy density loss can be minimized while still achieving safety improvements.
[0023] In one optional embodiment, the end of the second coating near the tail end of the first electrode plate at least partially overlaps with the end of the first active material layer on the first side near the tail end of the first electrode plate; the end of the second coating near the head end of the first electrode plate at least partially overlaps with the end of the first active material layer on the second side near the tail end of the first electrode plate.
[0024] Beneficial effects: By ensuring that the projection of the end of the second coating 13 near the tail end of the first electrode plate at least partially overlaps with the projection of the end of the first active material layer 12 near the tail end of the first electrode plate on the first side; and the projection of the end of the second coating 13 near the head end of the first electrode plate at least partially overlaps with the projection of the end of the first active material layer 12 near the tail end of the first electrode plate on the second side, since the first active material layer 12 and the first coating 11 are only provided on one side in the third region 300, when the second coating 13 is further provided in this region, after the first electrode plate is wound, the thickness increase in this region along the thickness direction of the wound cell is not significant, thereby reducing energy density loss to a very low degree and having almost no impact on the electrical performance of the cell.
[0025] In one optional embodiment, the thickness of the first coating is H1, the thickness of the second coating is H2, and the thickness of the first active material layer located in the first region is H3; satisfying: H1≤H3, and / or, H2≤H3; and / or, satisfying: H1≤H2.
[0026] Beneficial effects: The first coating prevents short circuits by isolating the first current collector from the second electrode. By making the thickness H1 of the first coating less than or equal to the thickness H3 of the first active material layer, the thinner thickness of the first coating helps reduce energy density loss. The second coating isolates the electrolyte from the first active material layer of the positive electrode, thus reducing heat generation from side reactions. By making the thickness H2 of the second coating greater than or equal to the thickness H1 of the first coating, the larger thickness of the second coating further reduces heat generation from side reactions, thereby improving safety performance.
[0027] In one alternative implementation, combined with Figure 5 As shown, the first coating is at least partially embedded in the first active material layer, and / or the second coating is at least partially embedded in the first active material layer; the depth to which the first coating is embedded in the first active material layer is not less than 0.5 μm; and / or the depth to which the second coating is embedded in the first active material layer is not less than 0.5 μm.
[0028] Beneficial effects: By embedding the first coating at least partially within the first active material layer, and / or, embedding the second coating at least partially within the first active material layer, it is beneficial to reduce the thickness of the wound cell and the contact resistance.
[0029] In one alternative implementation, the first electrode is a positive electrode and the second electrode is a negative electrode.
[0030] In one optional embodiment, the wound cell includes a flat region and an arc region, and both the first coating and the second coating are located at the tail end of the first electrode of the wound cell; the end of the first coating near the head end of the first electrode is located in the flat region of the wound cell; the end of the first coating near the tail end of the first electrode is located in the flat region of the wound cell; the end of the first coating near the head end of the first electrode is located at least beyond the center position of the wound cell along the width direction of the cell.
[0031] The second coating is located in the flat region of the wound cell at the end closest to the first electrode; the second coating is located in the flat region of the wound cell at the end closest to the first electrode.
[0032] Beneficial effects: Since the flat area is located on the large surface of the wound cell, it is more susceptible to damage from impacts or needle punctures. By setting the end of the first coating near the first electrode at least beyond the center of the wound cell, the first coating can cover a sufficient area of the flat area of the wound cell. This ensures that when the wound cell is subjected to a needle puncture test, the first coating can isolate the contact between the first current collector and the second electrode, preventing short circuits and improving the safety performance of the wound cell, making it more likely to pass the needle puncture test.
[0033] In one alternative embodiment, the wound cell further includes a finishing tape, which is attached at least to a third region of the first current collector.
[0034] Beneficial effect: By attaching the finishing tape to at least the third region of the first current collector, the advantage of the smaller thickness of the first current collector in the third region can be taken advantage of, and the position of the finishing tape can be reasonably arranged to avoid excessively increasing the thickness of the wound cell.
[0035] In one optional embodiment, the material of the first coating includes first inorganic particles, a first adhesive, and a first conductive agent; the material of the second coating includes second inorganic particles and a second adhesive.
[0036] The first inorganic particles and / or the second inorganic particles include at least one of silicon dioxide, magnesium oxide, aluminum oxide, calcium oxide, titanium oxide, boehmite, and magnesium hydroxide.
[0037] The first adhesive and / or the second adhesive comprises at least one of polyacrylic acid, polyacrylate, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, polyolefin, fluorinated rubber, polyimide, and derivatives thereof;
[0038] The first conductive agent includes at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.
[0039] Secondly, this utility model also provides a lithium-ion battery, including: the wound cell as described above.
[0040] Since lithium-ion batteries include wound cells and have the same effect as wound cells, they will not be elaborated on here. Attached Figure Description
[0041] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0042] Figure 1 This is a schematic diagram of the first electrode of this utility model;
[0043] Figure 2 This is a schematic diagram showing the region division of the first electrode plate of this utility model;
[0044] Figure 3 This is a schematic diagram showing the dimensions of the first electrode of this utility model;
[0045] Figure 4 This is a cross-sectional schematic diagram of the wound battery cell of this utility model;
[0046] Figure 5 This is a schematic diagram of another first electrode of this utility model;
[0047] Explanation of reference numerals in the attached figures:
[0048] 10. First current collector; 11. First coating; 12. First active material layer; 13. Second coating;
[0049] 20. Second current collector; 21. Second active material layer; 30. Diaphragm; 40. Finishing adhesive tape;
[0050] 100, Zone 1; 200, Zone 2; 300, Zone 3; 400, Zone 4. Detailed Implementation
[0051] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of 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 some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.
[0052] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0053] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.
[0054] Furthermore, the technical features involved in the different embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other.
[0055] The following is combined with Figures 1 to 5 The following describes embodiments of the present invention.
[0056] According to an embodiment of the present invention, in one aspect, a wound battery cell is provided, comprising a first electrode, a separator, and a second electrode stacked and wound together, wherein the first electrode and the second electrode have opposite polarities, and the first electrode comprises:
[0057] First current collector 10, first active material layer 12, first coating 11 and second coating 13;
[0058] Along the cell winding direction, the first current collector 10 sequentially includes a first region 100, a second region 200 and a third region 300;
[0059] The first current collector 10 is provided with a first active material layer 12 on both sides of the first region 100;
[0060] The first current collector 10 is provided with a first active material layer 12 and a first coating layer 11 on both sides of the second region 200;
[0061] The first current collector 10 is located on one side of the third region 300 and is provided with a first coating 11, a first active material layer 12 and a second coating 13 in sequence;
[0062] A first coating 11 located in the second region 200 and / or the third region 300 is disposed between the first active material layer 12 and the first current collector 10 on at least one side;
[0063] Along the length of the first electrode, the lengths of the first coating 11 and the second coating 13 are both less than the length of the first active material layer 12.
[0064] In this embodiment, the first active material layer 12 can be specifically disposed on both sides of the first current collector 10 along the thickness direction.
[0065] In this embodiment, the first electrode can serve as the positive electrode in the wound cell, and correspondingly, the first current collector 10 can be made of aluminum. The following description uses the first electrode as the positive electrode as an example to illustrate this solution.
[0066] The function of the first coating 11 is to prevent short circuits. The first coating 11 is disposed between the first active material layer 12 and the first current collector 10 on at least one side, which can isolate the contact between the first current collector and the second electrode and play a role in preventing short circuits.
[0067] In some embodiments, the second coating 13 is disposed on the side of the first active material layer 12 away from the first current collector 10, and located on the side of the first current collector 10 facing the inside of the wound cell. The function of the second coating 13 is to isolate the electrolyte from the contact between the electrolyte and the first active material layer 12 of the positive electrode, thereby reducing heat generation from side reactions. It should be noted that the side facing the inside of the wound cell refers to the side of the first current collector 10 near the winding center, with the winding center of the wound cell as a reference.
[0068] In this embodiment, both the first coating 11 and the second coating 13 are located at the winding end of the first electrode sheet.
[0069] For the needle penetration test, the closer to the outside of the wound cell, the greater the deformation caused by the needle penetration test, and the more likely it is to cause an internal short circuit. In this embodiment, a first coating layer 11 is provided between the first active material layer 12 and the first current collector 10. When facing the needle penetration test, it can isolate the contact between the first current collector and the second electrode, thereby preventing short circuits and improving the safety performance of the wound cell, making it more conducive to passing the needle penetration test.
[0070] For hot box testing, the outermost part of the wound cell heats up the fastest. In this embodiment, a second coating 13 is provided at the winding tail end of the first electrode sheet. The second coating 13 is provided on the side of the first active material layer 12 away from the first current collector 10 and on the side of the first current collector 10 facing the inside of the wound cell. This can isolate the electrolyte from the contact between the electrolyte and the first active material layer 12 of the positive electrode, reduce the heat generated by side reactions, improve the thermal safety performance of the cell, and make it more conducive to passing the hot box test.
[0071] The wound battery cell provided in the embodiments of this utility model, by providing a first coating 11 and a second coating 13 at the winding tail end of the first electrode sheet, especially at the winding tail end of the positive electrode sheet, can isolate the contact between the first current collector and the second electrode sheet, thereby preventing short circuits and improving the safety performance of the wound battery cell, making it more conducive to passing the needle penetration test; and can also isolate the contact between the electrolyte and the first active material layer 12 of the positive electrode, reducing the heat generated by side reactions, improving the thermal safety performance of the battery cell, and making it more conducive to passing the hot box test.
[0072] Although applying the first coating 11 and the second coating 13 to the entire area of the first current collector 10 can also improve the safety performance of the wound battery cell, compared to full coating, the first electrode provided in the embodiment of this utility model only applies the first coating 11 and the second coating 13 to a local area, which can minimize energy density loss while meeting safety performance requirements.
[0073] The wound battery cell provided in the embodiments of this utility model has a length of the first coating 11 and the second coating 13 that are both less than the length of the first active material layer 12 along the length direction of the first electrode sheet. Therefore, it is not necessary to provide the first coating 11 and the second coating 13 in the entire area of the first current collector 10. With minimal energy density loss, the battery cell can pass the needle penetration test and hot box test, thereby improving the safety performance of the battery cell, increasing the pass rate of the needle penetration test and hot box test of large-capacity battery cells, and the energy density loss is extremely low, with almost no impact on the electrical performance of the battery cell.
[0074] Additionally, both the first coating 11 and the second coating 13 are located at the winding end of the first electrode, further reducing energy density loss.
[0075] By dividing the first current collector 10 into regions, both the first coating 11 and the second coating 13 are placed in local areas, which can minimize energy density loss while meeting safety performance requirements.
[0076] Furthermore, the second coating 13 is applied only on one side of the third region 300, eliminating the need for a double-sided application, which helps reduce energy density loss and provides excellent safety improvement.
[0077] Additionally, the first current collector 10 also includes a fourth region 400, on both sides of the first current collector 10 located in the fourth region 400, where no other material is disposed, thus forming a blank current collector.
[0078] In some embodiments, combined with Figure 3 As shown, the length of the first active material layer 12 on the first side of the first current collector 10 is L4, and the length of the first active material layer 12 on the second side of the first current collector 10 is L5, satisfying: L5 < L4.
[0079] The projection of the first coating 11 on the first side near the tail end of the first electrode plate at least partially overlaps with the projection of the first active material layer 12 on the first side near the tail end of the first electrode plate; the projection of the first coating 11 on the second side near the tail end of the first electrode plate at least partially overlaps with the projection of the first active material layer 12 on the second side near the tail end of the first electrode plate.
[0080] The projections of the first coating 11 on the first side near the first electrode end and the first coating 11 on the second side near the first electrode end at least partially overlap;
[0081] The length of the first coating 11 on the first side of the first current collector 10 is L1, the length of the first coating 11 on the second side of the first current collector 10 is L2, and the length of the second coating 13 is L3, satisfying: L2 < L1 and L3 < L1;
[0082] In some embodiments, the value of L1 ranges from 100mm to 2000mm;
[0083] In some embodiments, the value of L2 ranges from 50mm to 1500mm;
[0084] In some embodiments, the value of L3 ranges from 50mm to 500mm.
[0085] As an example, L1 can be 100mm, 300mm, 500mm, 800mm, 1000mm, 1300mm, 1500mm, 1800mm, 2000mm, etc., or within the range of any two of the above values.
[0086] As an example, L2 can be 50mm, 80mm, 100mm, 200mm, 300mm, 450mm, 500mm, 800mm, 1000mm, 1300mm, 1500mm, etc., or within the range of any two of the above values.
[0087] As an example, L3 can be 50mm, 80mm, 100mm, 200mm, 300mm, 400mm, 500mm, etc., or within the range of any two of the above values.
[0088] By adopting this configuration, energy density loss can be minimized while still achieving safety improvements.
[0089] As a variation, the end of the first coating 11 on the first side near the tail end of the first electrode can also be shorter than the end of the first active material layer 12 on the first side near the tail end of the first electrode.
[0090] Similarly, as a variation, the end of the first coating 11 on the second side near the tail end of the first electrode can also be shorter than the end of the first active material layer 12 on the second side near the tail end of the first electrode.
[0091] In some embodiments, combined with Figure 3 As shown, the projection of the second coating 13 near the tail end of the first electrode plate at least partially overlaps with the projection of the first active material layer 12 near the tail end of the first electrode plate on the first side; the projection of the second coating 13 near the head end of the first electrode plate at least partially overlaps with the projection of the first active material layer 12 near the tail end of the first electrode plate on the second side.
[0092] By ensuring that the projection of the end of the second coating 13 near the tail end of the first electrode plate at least partially overlaps with the projection of the end of the first active material layer 12 near the tail end of the first electrode plate on the first side; and by ensuring that the projection of the end of the second coating 13 near the head end of the first electrode plate at least partially overlaps with the projection of the end of the first active material layer 12 near the tail end of the first electrode plate on the second side, and combining... Figure 2As shown, in the third region 300, since the first active material layer 12 and the first coating layer 11 are only provided on one side, when the second coating layer 13 is further provided in this region, after the first electrode is wound, the thickness of this region does not increase significantly along the thickness direction of the wound cell, thus reducing energy density loss to a very low level and having almost no impact on the electrical performance of the cell.
[0093] As a variation, the end of the second coating 13 near the tail end of the first electrode can also be shorter than the end of the first active material layer 12 near the tail end of the first electrode on the first side.
[0094] In some embodiments, combined with Figure 3 As shown, the thickness of the first coating 11 is H1, the thickness of the second coating 13 is H2, and the thickness of the first active material layer 12 located in the first region 100 is H3; satisfying: H1≤H3, and / or, H2≤H3.
[0095] In some embodiments, combined with Figure 3 As shown, H1 ≤ H2.
[0096] In this embodiment, the first coating 11 is disposed between the first active material layer 12 and the first current collector 10 on at least one side. Since the function of the first coating 11 is to prevent short circuits and isolate the contact between the first current collector and the second electrode, it plays a role in preventing short circuits. By making the thickness H1 of the first coating 11 less than or equal to the thickness H3 of the first active material layer 12, the thickness of the first coating 11 is thinner, which can help reduce energy density loss.
[0097] The second coating 13 is disposed on the side of the first active material layer 12 away from the first current collector 10 and on the side of the first current collector 10 facing the inside of the wound cell. Since the function of the second coating 13 is to separate the electrolyte from the contact between the first active material layer 12 of the positive electrode, the heat generated by the side reaction is reduced. By making the thickness H2 of the second coating 13 greater than or equal to the thickness H1 of the first coating 11, the thickness of the second coating 13 is larger, which can better reduce the heat generated by the side reaction, thereby improving the safety performance.
[0098] In some embodiments, the first coating 11 is at least partially embedded within the first active material layer 12, and / or the second coating 13 is at least partially embedded within the first active material layer 12.
[0099] In some embodiments, the first coating is embedded in the first active material layer to a depth of not less than 0.5 μm; and / or, the second coating is embedded in the first active material layer to a depth of not less than 0.5 μm.
[0100] By embedding the first coating 11 at least partially within the first active material layer 12, and / or embedding the second coating 13 at least partially within the first active material layer 12, it is beneficial to reduce the thickness of the wound cell and the contact resistance.
[0101] In some embodiments, one of the first electrode and the second electrode is a positive electrode and the other is a negative electrode.
[0102] Furthermore, in this embodiment, the first electrode is a positive electrode and the second electrode is a negative electrode.
[0103] At least one of the positive electrode and the negative electrode includes the first electrode as described above. The negative electrode includes a second current collector 20 and a second active material layer 21 disposed on at least one side of the second current collector 20.
[0104] In some embodiments, the wound cell includes a flat region and an arc region, and both the first coating 11 and the second coating 13 are located at the tail end of the first electrode; the end of the first coating 11 near the head end of the first electrode is located in the flat region of the wound cell; the end of the first coating 11 near the tail end of the first electrode is located in the flat region of the wound cell; the end of the first coating 11 near the head end of the first electrode is located at least beyond the center position of the wound cell along the width direction of the cell.
[0105] The end of the second coating 13 near the first electrode is located in the flat area of the wound cell; the end of the second coating 13 near the tail of the first electrode is located in the flat area of the wound cell.
[0106] The cell width direction specifically refers to Figure 4 direction shown.
[0107] Since the flat area is located on the large surface of the wound cell, it is more susceptible to damage from impacts or punctures. By setting the end of the first coating 11 near the first electrode at least beyond the center of the wound cell, the first coating 11 can cover a sufficient area of the flat area of the wound cell. This ensures that when the wound cell is subjected to a puncture test, the first coating 11 can isolate the contact between the first current collector and the second electrode, preventing short circuits and improving the safety performance of the wound cell, making it more likely to pass the puncture test.
[0108] In some embodiments, the second coating 13 is located between the first active material layer 12 of the positive electrode and the separator 30.
[0109] By placing the second coating 13 between the first active material layer 12 of the positive electrode and the separator 30, the second coating 13 can ensure that the electrolyte is separated from the contact between the first active material layer 12 of the positive electrode, reduce the heat generated by side reactions, improve the thermal safety performance of the battery cell, and make it more conducive to passing the hot box test.
[0110] In some embodiments, the wound cell further includes a finishing tape 40, which is attached at least to a third region 300 of the first current collector 10.
[0111] By attaching the finishing tape 40 to at least the third region 300 of the first current collector 10, the advantage of the smaller thickness of the first current collector 10 in the third region 300 can be taken advantage of, and the position of the finishing tape 40 can be reasonably arranged to avoid excessively increasing the thickness of the wound battery cell.
[0112] In some embodiments, the material of the first coating 11 includes first inorganic particles, a first adhesive, and a first conductive agent; the material of the second coating 13 includes second inorganic particles and a second adhesive.
[0113] The first inorganic particles and / or the second inorganic particles include at least one of silicon dioxide, magnesium oxide, aluminum oxide, calcium oxide, titanium oxide, boehmite, and magnesium hydroxide.
[0114] The first adhesive and / or the second adhesive comprises at least one of polyacrylic acid, polyacrylate, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, polyolefin, fluorinated rubber, polyimide, and derivatives thereof;
[0115] The first conductive agent includes at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.
[0116] The lithium-ion battery includes tabs. In this embodiment, the tabs adopt a CTP (center-in-place tab technology) structure. The first active material layer 12 has a groove, and a tab groove is provided in the groove. The tab is located in the tab groove and is electrically connected to the first current collector 10.
[0117] The tab groove is located on the side of the first current collector 10 away from the second coating 13.
[0118] In this embodiment, the tab of the CTP structure is prepared as follows: the active layer on the first electrode sheet at the location for mounting the tab is cleaned away to obtain a groove. At this time, part of the active layer on one side of the first electrode sheet is cleaned away, exposing the current collector for mounting the tab. The tab is placed in the groove and electrically connected to the current collector. In this embodiment, the tab groove is located at the middle position along the length direction of the first electrode sheet.
[0119] According to an embodiment of the present invention, in another aspect, a lithium-ion battery is also provided, comprising: the wound cell as described above.
[0120] The specific preparation process of the lithium-ion battery provided in this embodiment is as follows:
[0121] Step 1: Prepare the positive electrode first coating 11 slurry. Coat the slurry onto aluminum foil using a gravure coating or skip coating method. After drying, a positive electrode current collector partially coated with the first coating 11 is obtained. The preparation method of the partially undercoated positive electrode first coating 11 provided in this embodiment is as follows: Nano-alumina is mixed evenly with conductive agents carbon black and carbon nanotubes. Then, a certain amount of binder polyvinylidene fluoride adhesive and NMP are added and stirred evenly to obtain the positive electrode first coating 11 slurry.
[0122] Step 2: Prepare the positive electrode active material layer slurry. Add conductive carbon black and carbon nanotubes to the PVDF adhesive and stir until homogeneous. Then add lithium cobalt oxide and stir until homogeneous again to prepare the positive electrode active material layer slurry. Coat the positive electrode active material layer slurry onto the surface of the first positive electrode coating 11 to obtain the positive electrode bottom layer. The mass fraction of lithium cobalt oxide in the positive electrode active material layer is 97.6%, the mass fraction of PVDF is 1.05%, and the mass fraction of conductive carbon black and carbon nanotubes is 1.35% (where the mass ratio of carbon black to carbon nanotubes is 1:1).
[0123] Step 3: Prepare the second coating slurry 13 for the positive electrode. Add nano-silica to the PVDF adhesive and stir until homogeneous. Then add NMP and stir until homogeneous again to obtain the second coating slurry 13. Coat the surface of the positive electrode single-sided sheet with the second coating 13 slurry. After baking and rolling, the positive electrode single-sided sheet is obtained. The mass fraction of nano-silica in the second coating 13 is 90%, and the mass fraction of PVDF is 10%.
[0124] Step 4: Prepare the negative electrode active layer slurry. Mix 97.3% graphite, 0.5% conductive carbon black, 1.3% binder and 0.9% dispersant evenly, then add an appropriate amount of deionized water and disperse evenly to prepare the negative electrode active layer slurry. Coat the negative electrode active layer slurry onto carbon-coated copper foil, and obtain the negative electrode sheet after baking and rolling.
[0125] Step 5: After the positive and negative electrode sheets are slit, formed and wound with the separator to obtain the wound cell, the wound cell is packaged, baked, injected with electrolyte, formed, resealed, sorted and OCV to obtain the lithium-ion battery.
[0126] The electrolyte is a commercially available conventional electrolyte, and the lithium salt in it is LiFP6.
[0127] Safety performance testing may include furnace temperature testing.
[0128] Combination Figure 3 As shown, the length of the first coating 11 on the first side of the first current collector 10 is L1, the length of the second coating 13 is L3, and the length of the first active material layer 12 on the first side of the first current collector 10 is L4.
[0129] Referring to Table 1 below, the safety performance and volumetric energy density of lithium-ion batteries are verified through several examples and comparative examples.
[0130] The specific methods for safety performance testing are as follows:
[0131] ① Needle prick test:
[0132] At room temperature, the battery cell is discharged at 1C to 3.0V, then charged at a constant current of 0.7C to 4.50V, with a cutoff current of 0.02C. This process of discharging at 1C to 3.0V is repeated five times. Then, it is charged again at a constant current of 0.7C to 4.50V, with a cutoff current of 0.02C. Within 48 hours of the test completion, a 2.5mm diameter steel needle is used to vertically penetrate the lithium-ion battery at three positions (left, center, and right) at a speed of 30mm / s. If the battery does not ignite or explode, it passes the test. Twenty samples are tested, and the pass rate of each sample is observed.
[0133] ②Hotbox test:
[0134] The battery cell is fully charged to its maximum operating voltage of 4.5V. It is then placed in an oven and heated to the set target temperature (130℃, 132℃, 135℃, or 140℃) at a rate of 5±2℃ / min, and held for 60 minutes. The test is then complete. The cell is considered passed if it does not catch fire or explode; otherwise, it fails the test if the temperature continues to rise until it catches fire or explodes. Ten samples are tested, and each sample is observed to determine if it passes the test.
[0135] The specific method for measuring volumetric energy density is as follows:
[0136] The prepared battery was charged to full capacity under constant current and constant voltage at 25℃, and then discharged to 3.0V at 0.5C. The discharged capacity was recorded as the battery capacity.
[0137] The prepared finished battery was charged to 50% SOC at 25°C, and the battery thickness was tested using 600g PPG.
[0138] Calculate the volumetric energy density (ED) = battery capacity * platform voltage / battery length / width / thickness.
[0139] Calculate the ED loss rate as follows: (Energy density of Comparative Example 1 - Energy density of Example) / Energy density of Comparative Example 1.
[0140] Table 1
[0141]
[0142] As can be seen from the table above, in Comparative Example 1, the first current collector 10 does not have a first coating 11 and a second coating 13 on both sides. As a result, it failed the hot box test and the needle penetration test, indicating poor safety.
[0143] The volumetric energy density of Comparative Example 1 is used as the basis for comparison. In Example 1, the first side of the first current collector 10 is provided with both a first coating 11 and a second coating 13. It can pass the hot box test and the needle penetration test smoothly, and the volumetric energy density loss is well controlled, thus balancing energy density and safety.
[0144] In Embodiment 2, the length L3 of the second coating 13 is the same as that in Embodiment 1, while the length L1 of the first coating 11 on the first side of the first current collector 10 is longer than that in Embodiment 1. Although it also meets the requirements of safety performance testing, the volumetric energy density loss is greater.
[0145] In Example 3, the length L1 of the first coating 11 on the first side of the first current collector 10 is the same as in Example 1, but the length L3 of the second coating 13 is shorter than that in Example 1. Although the volumetric energy density loss is well controlled, the pass rate of the hot box test is slightly lower.
[0146] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the implementation. Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and all such modifications and variations fall within the scope defined by the present invention.
Claims
1. A wound battery cell, comprising a first electrode, a separator, and a second electrode stacked and wound together, wherein the first electrode and the second electrode have opposite polarities, characterized in that, The first electrode includes a first current collector (10), a first active material layer (12), a first coating (11), and a second coating (13); Along the cell winding direction, the first current collector (10) sequentially includes a first region (100), a second region (200) and a third region (300). The first current collector (10) is provided with the first active material layer (12) on both sides of the first region (100). The first current collector (10) is provided with the first active material layer (12) and the first coating layer (11) on both sides of the second region (200). The first current collector (10) is located on one side of the third region (300) and is sequentially provided with the first coating (11), the first active material layer (12) and the second coating (13). The first coating (11) located in the second region (200) and / or the third region (300) is disposed between the first active material layer (12) and the first current collector (10); Along the length direction of the first electrode, the length of the first coating (11) and the length of the second coating (13) are both less than the length of the first active material layer (12).
2. The wound battery cell according to claim 1, characterized in that, The second coating (13) is located on the side of the first current collector (10) facing the inside of the wound cell; the second coating (13) is located between the first active material layer (12) of the first electrode and the separator (30).
3. The wound battery cell according to claim 1, characterized in that, The length of the first active material layer (12) on the first side of the first current collector (10) is L4, and the length of the first active material layer (12) on the second side of the first current collector (10) is L5, satisfying: L5 < L4; The first coating (11) on the first side near the tail end of the first electrode plate has at least partially overlapped with the first active material layer (12) on the first side near the tail end of the first electrode plate; the first coating (11) on the second side near the tail end of the first electrode plate has at least partially overlapped with the first active material layer (12) on the second side near the tail end of the first electrode plate. The first coating (11) on the first side near the first electrode head end and the first coating (11) on the second side near the first electrode head end project at least partially overlap; The length of the first coating (11) on the first side of the first current collector (10) is L1, the length of the first coating (11) on the second side of the first current collector (10) is L2, and the length of the second coating (13) is L3, satisfying: L2 < L1, and satisfying: L3 < L1; And / or, the value of L1 ranges from 100mm to 2000mm; And / or, the value of L2 ranges from 50mm to 1500mm; And / or, the value of L3 is in the range of 50mm-500mm.
4. The wound battery cell according to claim 3, characterized in that, The second coating (13) near the tail end of the first electrode plate has at least partially overlapped with the first active material layer (12) near the tail end of the first electrode plate on the first side; the second coating (13) near the head end of the first electrode plate has at least partially overlapped with the first active material layer (12) near the tail end of the first electrode plate on the second side.
5. The wound battery cell according to claim 1, characterized in that, The thickness of the first coating (11) is H1, the thickness of the second coating (13) is H2, and the thickness of the first active material layer (12) located in the first region (100) is H3; satisfying: H1≤H3, and / or, H2≤H3; And / or, satisfying: H1≤H2.
6. The wound battery cell according to any one of claims 1 to 5, characterized in that, The first coating (11) is at least partially embedded within the first active material layer (12), and / or the second coating (13) is at least partially embedded within the first active material layer (12); The first coating (11) is embedded in the first active material layer (12) to a depth of not less than 0.5 μm; and / or, the second coating (13) is embedded in the first active material layer (12) to a depth of not less than 0.5 μm.
7. The wound battery cell according to claim 1, characterized in that, The first electrode is the positive electrode, and the second electrode is the negative electrode.
8. The wound battery cell according to claim 1, characterized in that, The wound cell includes a flat region and an arc region. The first coating (11) and the second coating (13) are both located at the tail end of the first electrode. The end of the first coating (11) near the head end of the first electrode is located in the flat region of the wound cell. The end of the first coating (11) near the tail end of the first electrode is located in the flat region of the wound cell. The end of the first coating (11) near the head end of the first electrode is located at least beyond the center position of the wound cell along the width direction of the cell. The second coating (13) is located in the flat area of the wound cell at one end near the first electrode; the second coating (13) is located in the flat area of the wound cell at one end near the tail end of the first electrode.
9. The wound battery cell according to claim 1, characterized in that, The wound cell also includes a finishing adhesive tape (40), which is attached at least to the third region (300) of the first current collector (10).
10. A lithium-ion battery, characterized in that, Including the wound battery cell as described in any one of claims 1 to 9 above.