Battery cell and battery pack with improved electrolyte wettability
By covering the outer wall of the battery cell with a perforated protective film and creating grooves on the negative electrode, the problem of poor electrolyte wettability in the middle layer and the central area of the electrode in large-size battery cells is solved, thereby improving the cycle life and safety performance of the battery cell.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SHANGHAI XUANYI NEW ENERGY DEV CO LTD
- Filing Date
- 2025-06-13
- Publication Date
- 2026-07-24
AI Technical Summary
Poor electrolyte wettability in the middle layer and central region of the electrode in large-size cells leads to increased lithium-ion transport impedance, severe lithium plating, and affects cell cycle life, safety performance, and power performance.
A perforated protective film is wrapped around the outer wall of the battery cell, and grooves are made on the negative electrode to form channels for the electrolyte, thereby improving the wettability of the electrolyte.
It significantly improves the cell interface, reduces lithium-ion migration resistance, enhances cell cycle life and power performance, and improves thermal, electrical, and mechanical safety performance.
Smart Images
Figure CN224554384U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of battery technology, and in particular to a battery cell and battery pack that improves electrolyte wettability. Background Technology
[0002] With the development and application of large-capacity lithium iron phosphate (LFP) energy storage cells, the dimensions of these cells are continuously increasing, leading to increasingly poor electrolyte wetting in the middle layer and central electrode area. Furthermore, most existing energy storage cells employ a prismatic design. To prevent corrosion caused by contact between the negative electrode and the aluminum shell, a PET film is wrapped around the bare cell. However, this PET film further hinders electrolyte wetting within the electrode. Poor interface wetting increases lithium-ion transport impedance, exacerbating purple spots or lithium plating in this area during later stages of cycling, resulting in irreversible loss of active lithium and ultimately reducing cell cycle life and power performance.
[0003] More seriously, lithium plating caused by poor electrolyte wettability in the intermediate layer and central region of large-size battery cells not only affects the cell's electrical performance but also severely impacts its thermal, electrical, and mechanical safety performance in the later stages of battery cycling. Lithium dendrites first puncture the separator, leading to internal short circuits and a decrease in the K-value. Severely uneven, blocky lithium dendrites can cause short circuits over a larger area, easily triggering thermal runaway under overcharging and other application conditions. Simultaneously, the intermediate layer of large-size battery cells has poor heat dissipation, and the lithium dendrites in the intermediate layer react with the surface electrolyte at high temperatures, generating a large amount of heat and gas, further increasing the temperature of the intermediate layer and repeatedly triggering thermal runaway. Therefore, solving the electrolyte wettability problem in the central region of the intermediate layer of large-size battery cells is becoming increasingly important.
[0004] Currently, methods to improve electrolyte wettability mainly include using macroporous membranes, increasing aging time and temperature during cell manufacturing, and using low-viscosity electrolytes. Macroporous membranes have a certain effect on improving electrolyte wettability, but their tensile and puncture strength are poor, leading to a decrease in the cell's K-value and mechanical safety performance, and their relatively high cost hinders the commercialization of low-cost cells. Increasing aging time and temperature during cell manufacturing increases the cell's internal resistance, reduces its initial efficiency, and increases manufacturing costs. Low-viscosity electrolytes often contain linear ester solvents, but linear ester solvents have low boiling points, which can worsen the cell's thermal safety performance. These solutions involve a trade-off between performance and cost and are not the optimal solutions for addressing the electrolyte wettability problem in large-size cells. Utility Model Content
[0005] To address the above technical problems, this utility model provides a battery cell with improved electrolyte wettability; on the other hand, it also provides a battery pack.
[0006] The technical problem solved by this utility model can be achieved by the following technical solution:
[0007] On the one hand, a battery cell with improved electrolyte wettability is provided, the battery cell including a housing and a cover plate that closes the opening of the housing, and a bare battery cell is disposed inside the housing;
[0008] The outer wall of the bare battery cell is covered with a protective film, which is located between the bare battery cell and the housing and the cover plate. The protective film has perforated areas.
[0009] Preferably, the perforated areas are located on the protective films on both sides of the bare battery cell; and / or
[0010] The perforated area is located on the protective film on the bottom surface of the bare battery cell.
[0011] Preferably, there is a first gap between the perforated area and the edge of the protective film on the surface.
[0012] Preferably, the first spacing is 2mm to 10mm.
[0013] Preferably, the areas on the protective film other than the perforated areas are unperforated areas.
[0014] Preferably, the perforated area is provided with multiple openings, the diameter of the openings is 1mm to 3mm, and the spacing between the openings is 2mm to 10mm.
[0015] Preferably, the bare cell is formed by stacking or winding a positive electrode sheet, a separator, and a negative electrode sheet in sequence. The negative electrode sheet has a groove that extends from one edge of the negative electrode sheet along a first direction to the other edge.
[0016] Preferably, the first direction is the length direction and / or width direction of the negative electrode sheet.
[0017] Preferably, the width of the groove is 0.5mm to 3mm; and / or
[0018] The depth of the groove is 5μm to 50μm; and / or
[0019] The grooves include multiple grooves, and the spacing between adjacent grooves is 2mm to 5mm; and / or
[0020] The groove and the negative electrode sheet have a second distance at their edges in a second direction perpendicular to the first direction, and the second distance is not less than 20 mm.
[0021] On the other hand, a battery pack is also provided, including at least one cell as described above that improves electrolyte wettability.
[0022] The advantages or beneficial effects of this utility model's technical solution are as follows:
[0023] This invention solves the problem of conventional PET wrapping films hindering the absorption and wetting of external electrolyte into the bare cell by covering the outer wall of the cell with a perforated protective film, thereby improving the electrolyte wettability of the cell and thus improving the cycle life and power performance of the cell. In addition, the reduction in lithium plating can improve the thermal, electrical and mechanical safety performance of the cell during use. Attached Figure Description
[0024] Figure 1 This is a schematic diagram of the structure of a battery cell that improves electrolyte wettability, as shown in a preferred embodiment of the present invention.
[0025] Figure 2 This is a schematic diagram of the perforated area of the protective film in a preferred embodiment of the present invention.
[0026] Figure 3 This is a schematic diagram of the grooved structure of the negative electrode sheet in a preferred embodiment of the present invention. Detailed Implementation
[0027] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0028] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.
[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention.
[0030] In a preferred embodiment of this utility model, based on the above-mentioned problems existing in the prior art, a battery cell with improved electrolyte wettability is provided, such as... Figure 1 and Figure 2 As shown, the battery cell mainly consists of a housing 1 and a cover plate for sealing the opening of the housing 1, with a bare battery cell 2 disposed inside the housing 1.
[0031] The outer wall of the bare cell 2 is covered with a protective film 3, which is located between the bare cell 2 and the housing 1 and the cover plate. In particular, perforated areas are formed on the protective film 3 to allow electrolyte from the outside of the bare cell 2 to pass through, so as to be adsorbed and wetted into the interior of the bare cell 2.
[0032] Specifically, addressing the issue that conventional PET film wrapping hinders the adsorption and wetting of external electrolyte into the bare battery cell, this embodiment employs a perforated protective film coating the outer wall of the bare battery cell 2. This involves creating perforated areas on the protective film 3, allowing external electrolyte to be adsorbed and wetted into the bare battery cell 2 through these perforated areas. This improves the electrolyte wettability of the battery cell, thereby enhancing its cycle life and power performance. Furthermore, it reduces lithium plating, thus improving the thermal, electrical, and mechanical safety performance of the battery cell during use.
[0033] More specifically, the protective film 3 used in this embodiment is a polyethylene terephthalate (PET) film.
[0034] In a preferred embodiment, the perforated areas are located on the protective films 3 on both sides of the bare cell 2; and / or
[0035] The perforated area is located on the protective film 3 on the bottom surface of the bare cell 2.
[0036] Specifically, in this embodiment, the PET protective film 3 is wrapped around the six outer surfaces of the bare battery cell 2. Here, each surface of the bare battery cell 2 wrapped with the PET protective film 3 is defined as follows: the top surface is the same surface as the cover plate, the bottom surface is the surface opposite to the top surface, the front and back surfaces are the two opposite surfaces of the bare battery cell 2 with the largest area, and the remaining two surfaces are defined as the side surfaces.
[0037] It is worth noting that the perforated areas on the PET protective film 3 are only set on the two sides and bottom of the bare battery cell 2, while the top and front and back PET protective films 3 are not perforated.
[0038] Considering that the electrolyte on the outside of the bare cell mainly flows into the inside of the bare cell through the PET protective film 3 with openings on the sides, top, and bottom, openings in the protective film 3 on the sides and bottom can effectively reduce the obstruction encountered by the electrolyte when flowing in these three directions. The top surface is left unperforated to reduce the risk of a short circuit caused by contact between the anode and the cover plate; the front and back surfaces are left unperforated to eliminate the risk of corrosion caused by contact between the front and back electrode plates and the casing 1.
[0039] In a preferred embodiment, a first distance, denoted as S2, is provided between the perforated area and the edge of the protective film 3 on the surface.
[0040] In a preferred embodiment, the first spacing S2 is 2mm to 10mm.
[0041] Specifically, for the perforated areas on each side of the protective film 3, there is a first distance S2 between them and the edge of the protective film on that side. If the first distance S2 is too small, the perforated areas are too close to the edge of the protective film and other non-perforated surfaces of the protective film, increasing the possibility of contact between the electrode and the cover plate and the shell, thereby increasing the risk of corrosion and short circuit caused by contact between the electrode and the shell 1. If the first distance S2 is too large, the perforated areas are relatively smaller, and the channels through which the electrolyte can enter the bare cell become narrower and fewer, making it difficult to effectively alleviate the degree of purple spots in the central area and reduce the degree of lithium plating. The perforated areas weaken the electrolyte transport effect on the intermediate layer, resulting in an insignificant improvement effect on the cell interface and difficulty in effectively reducing the lithium ion migration resistance.
[0042] The first spacing S2 ranges from 2mm to 10mm. As an example and not a limitation, the first spacing S2 can be 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, or 10mm.
[0043] In a preferred embodiment, the areas on the protective film other than the perforated areas are unperforated areas, which are located on the front, back and top surfaces of the bare battery cell 2.
[0044] In a preferred embodiment, the perforated area is provided with multiple openings, the diameter R1 of which is 1mm to 3mm and the spacing S1 of which is 2mm to 10mm.
[0045] Specifically, if the aperture is too small, it will affect the flow of the electrolyte and reduce the wetting efficiency; while a large aperture may reduce the strength of the protective film, increasing the risk of short circuits and a decrease in the K-value of the battery cell. In this embodiment, the aperture R1 ranges from 1 mm to 3 mm. As an example and not a limitation, the aperture R can be 1 mm, 1.5 mm, 2 mm, 2.5 mm, or 3 mm.
[0046] Specifically, excessively dense perforations can compromise the overall strength of the protective film, increasing the risk of damage and potentially causing the electrolyte flow to become too concentrated, hindering uniform wetting. Conversely, excessively sparse perforations reduce the channels for electrolyte to enter the bare battery cell, reducing the wetting effect. In this embodiment, the spacing S1 between adjacent perforations ranges from 2mm to 10mm. As an example and not a limitation, the perforation spacing S1 can be 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, or 10mm.
[0047] In a preferred embodiment, the bare cell 2 is formed by sequentially stacking or winding a positive electrode sheet, a separator, and a negative electrode sheet, such as... Figure 3 As shown, a groove 41 is provided on the negative electrode 4, and the groove 41 extends from one edge of the negative electrode 4 along a first direction to the other edge.
[0048] Specifically, the housing 1 contains several positive electrode plates and negative electrode plates 4 (cathode plates) stacked in an alternating manner; a diaphragm separates the positive electrode plates and negative electrode plates 4.
[0049] In this embodiment, the negative electrode 4 used in the bare cell 2 is a scribing and grooved cathode electrode. The scribing and grooved negative electrode is created by laser cleaning, etching linear grooves of a certain depth, such as 5–20 μm, at equal intervals on the surface of the negative electrode. This channel facilitates the transport of the peripheral electrolyte to the interior and reaches the central region of the electrode.
[0050] Furthermore, the scribed and grooved cathode electrode can be used to replace several layers of negative electrode in the middle of a large-size bare cell, or it can be used to replace all conventional negative electrode.
[0051] In a preferred embodiment, the first direction is the length direction and / or width direction of the negative electrode 4.
[0052] Specifically, in some embodiments, the groove 41 can be opened along the length direction of the negative electrode 4, extending from one end of the negative electrode 4 to the edge of the electrode at the other end, thereby ensuring that the groove 41 exists at the edge of the electrode, so that the electrolyte outside the bare cell flows into the inside of the bare cell along the groove 41 after passing through the protective film 3 with the side opening.
[0053] In other embodiments, the groove 41 may also be opened along the width direction of the negative electrode 4, extending from one end of the negative electrode 4 to the edge of the electrode at the other end, thereby ensuring that the groove 41 exists at the edge of the electrode, so that the electrolyte outside the bare cell flows into the inside of the bare cell along the groove 41 after passing through the protective film 3 with the bottom opening.
[0054] In a preferred embodiment, the width of the groove 41 is 0.5 mm to 3 mm; and / or
[0055] The depth of the groove 41 is 5μm to 50μm, more preferably, the depth of the groove 41 is 5μm to 20μm; and / or
[0056] The grooves 41 include multiple grooves, and the spacing between adjacent grooves 41 is 2mm to 5mm; and / or
[0057] The groove 41 and the negative electrode sheet have a second distance S3 at the edge of the second direction perpendicular to the first direction. The second distance S3 is not less than 20mm, that is, S3>20mm.
[0058] On the other hand, a battery pack is also provided, including at least one cell as described above that improves electrolyte wettability.
[0059] In this embodiment of the invention, a novel approach combining perforation of the PET protective film 3 encasing the bare cell 2 with grooves 41 created on the negative electrode 4 is applied for the first time to a large-size battery cell. This enhances the electrolyte wetting effect. Perforation of the PET protective film 3 allows the electrolyte outside the battery cell 2 to be absorbed and wetted into the battery cell 2 through the perforated areas, solving the problem of conventional PET films hindering the absorption and wetting of electrolyte from the outside of the battery cell. Simultaneously, the grooves 41 on the negative electrode 4 address the issue of poor electrolyte wetting in the middle layer and central area of the electrode in large-size, thick batteries, significantly improving the cell interface and reducing lithium-ion migration resistance. This, in turn, significantly improves the cell's cycle life and power performance. Furthermore, the reduced degree of lithium plating also improves the thermal, electrical, and mechanical safety performance of the battery cell during use.
[0060] The following specific embodiments further illustrate and explain this technical solution:
[0061] Example 1
[0062] In this embodiment 1, the bare cell 2 can be a 340Ah lithium iron phosphate square aluminum shell cell with a width of 214mm, a height of 219mm, and a thickness of 53mm.
[0063] A hole is made in the PET protective film 3, and the perforated PET protective film 3 is wrapped around the outer wall of the aforementioned 340Ah bare battery cell 2 and then fitted into the inner cover of the housing 1.
[0064] The opening information on the PET protective film 3 is designed as follows: openings are only made on the two sides and the bottom of the PET protective film; the diameter of the opening is 1.5mm and the spacing between the openings is 3mm; the distance between the perforated area and the outer edge of the PET protective film 3 on the same side is 5mm.
[0065] Example 2
[0066] In the battery cell of this embodiment 1, the bare battery cell 2 is also a 340Ah lithium iron phosphate square aluminum shell battery cell with a width of 214mm, a height of 219mm, and a thickness of 53mm.
[0067] Linear grooves 41 are formed on the negative electrode plate 4 of the bare cell 2.
[0068] The design of the groove 41 is as follows: the width of the groove 41 is 1mm, the spacing of the groove 41 is 3mm, the depth of the groove 41 is 10μm, and the groove 41 is designed to be parallel to the width direction of the negative electrode sheet; the distance S3 between the edge of the groove 41 area and the edge of the negative electrode sheet is 40mm.
[0069] The perforation scheme on the PET protective film 3 is the same as that in Example 1, and will not be described again here.
[0070] Comparative Example 1
[0071] In the battery cell of Comparative Example 1, the bare battery cell 2 also uses a 340Ah lithium iron phosphate square aluminum shell battery cell with a width of 214mm, a height of 219mm, and a thickness of 53mm. The outer wall of the bare battery cell 2 is wrapped with a conventional PET protective film, and there are no grooves on the electrode plates.
[0072] Table 1 Comparison of the schemes in Examples 1-2 and Comparative Example 1
[0073] Group plan Comparative Example 1 Standard PET protective film Example 1 Open-pore PET protective film Example 2 Perforated PET protective film + slotted negative electrode sheet
[0074] The battery cells prepared in Examples 1-2 and Comparative Example 1 as shown in Table 1 above were tested, and the test results are shown in Table 2 below.
[0075] Table 2 shows the test results for Examples 1-2 and Comparative Example 1:
[0076]
[0077] Based on Table 2 above, compared with the existing conventional PET wrapping film solution, by making perforations on the protective film 3 that is separately wrapped on the outer wall of the battery cell, the electrolyte outside the bare battery cell 2 can be adsorbed and wetted into the interior of the bare battery cell 2 from the perforated area of the protective film 3. This can alleviate the degree of purple spots in the central area to a certain extent, reduce the degree of lithium plating, and improve the cycle performance of the battery cell.
[0078] Compared with the single protective film perforation scheme, the cell interface is greatly improved by adopting the superposition scheme of protective film 3 perforation and electrode grooving, and the cycle performance is significantly improved.
[0079] The advantages or beneficial effects of adopting the above technical solution are as follows: This utility model, by superimposing a perforated protective film covering the outer wall of the battery cell with a grooved design on the negative electrode, improves the electrolyte wetting effect of the intermediate layer and the central region of the electrode in large-size, thick battery cells, significantly improves the battery cell interface, reduces lithium-ion migration resistance, and thus significantly improves the cycle life and power performance of the battery cell. Furthermore, the reduction in lithium plating can also improve the thermal, electrical, and mechanical safety performance of the battery cell during use.
[0080] The above are merely preferred embodiments of the present utility model and are not intended to limit the implementation methods and protection scope of the present utility model. Those skilled in the art should realize that any equivalent substitutions and obvious changes made using the content of this specification and illustrations should be included within the protection scope of the present utility model.
Claims
1. A battery cell for improving electrolyte wettability, characterized in that, The battery cell includes a housing and a cover plate that closes the opening of the housing, and a bare battery cell is disposed inside the housing; The outer wall of the bare battery cell is covered with a protective film, which is located between the bare battery cell and the housing and the cover plate. The protective film has perforated areas.
2. The battery cell with improved electrolyte wettability according to claim 1, characterized in that, The perforated areas are located on the protective films on both sides of the bare battery cell; and / or The perforated area is located on the protective film on the bottom surface of the bare battery cell.
3. The battery cell with improved electrolyte wettability according to claim 1, characterized in that, There is a first distance between the perforated area and the edge of the protective film on the surface.
4. The battery cell with improved electrolyte wettability according to claim 3, characterized in that, The first spacing is 2mm to 10mm.
5. The battery cell with improved electrolyte wettability according to claim 1, characterized in that, The areas on the protective film other than the perforated areas are unperforated areas.
6. The battery cell with improved electrolyte wettability according to claim 1, characterized in that, The perforated area is provided with multiple openings, the diameter of which is 1mm to 3mm and the spacing between which is 2mm to 10mm.
7. The battery cell with improved electrolyte wettability according to claim 1, characterized in that, The bare cell is formed by stacking or winding a positive electrode, a separator, and a negative electrode in sequence. The negative electrode has a groove that extends from one edge of the negative electrode along a first direction to the other edge.
8. The battery cell with improved electrolyte wettability according to claim 7, characterized in that, The first direction is the length direction and / or width direction of the negative electrode sheet.
9. The battery cell with improved electrolyte wettability according to claim 7, characterized in that, The width of the groove is 0.5mm to 3mm; and / or The depth of the groove is 5μm to 50μm; and / or The grooves include multiple grooves, and the spacing between adjacent grooves is 2mm to 5mm; and / or The groove and the negative electrode sheet have a second distance at their edges in a second direction perpendicular to the first direction, and the second distance is not less than 20 mm.
10. A battery pack, characterized in that, It includes at least one battery cell that improves electrolyte wettability as described in any one of claims 1-9.