battery

Abstract

The embodiment of the present application provides a battery. Wherein, the battery comprises an electrode assembly, a first adhesive layer, a positive pole lug and a second adhesive layer. The electrode assembly comprises a negative pole sheet and a positive pole sheet; the negative pole sheet comprises a thinning groove formed in a negative pole active layer; along a first direction, the negative pole sheet has oppositely arranged first and second edges, the thinning groove is arranged close to the first edge, and the thinning groove has a first gap L1 with the first edge, 0 < L1 < 5 mm; the first adhesive layer is located in the thinning groove; along the first direction, part of the positive pole lug extends to outside the first edge, part of the positive pole lug is located in the thinning groove; the second adhesive layer is arranged on the positive pole lug, and a projection of the second adhesive layer is located in the thinning groove. Therefore, the battery of the embodiment of the present application helps to reduce the local enrichment of electrolyte in the thinning groove area and inhibit the risk of copper foil precipitation.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a battery. Background Technology

[0002] To improve battery energy density, related technologies typically involve creating a thinning region at the edge of the negative electrode and filling this region with an adhesive layer to form an embedded adhesive structure. However, during battery liquid filling and cycling, under high-voltage systems or specific charge / discharge conditions, this can easily lead to internal short circuits or overheating, causing thermal runaway and affecting safety. Summary of the Invention

[0003] In view of this, the present invention aims to provide a battery that solves the problems of short cycle life or even thermal runaway in existing batteries.

[0004] One aspect of this invention is a battery.

[0005] The charging cutoff voltage of the battery is ≥4.48V.

[0006] The battery of this invention includes an electrode assembly, a first adhesive layer, a positive electrode tab, and a second adhesive layer.

[0007] The electrode assembly includes a core structure formed by stacking and winding a negative electrode sheet, a separator, and a positive electrode sheet; the negative electrode sheet includes a thinning groove formed in the negative electrode active layer, the thickness of the negative electrode active layer in the thinning groove is less than the thickness of the negative electrode active layer in the non-thinning groove region of the negative electrode sheet; along a first direction, the negative electrode sheet has a first edge and a second edge disposed opposite to each other, the thinning groove is disposed close to the first edge, and the thinning groove and the first edge have a first gap L1, 0 < L1 ≤ 5 mm; a first adhesive layer is located in the thinning groove; a positive electrode tab is electrically connected to the positive electrode sheet, along the first direction, a portion of the positive electrode tab extends beyond the first edge, and in the orthographic projection of a plane perpendicular to the second direction, a portion of the positive electrode tab is located in the thinning groove; a second adhesive layer is disposed on the positive electrode tab, and in the orthographic projection of a plane perpendicular to the second direction, the projection of the second adhesive layer is located in the thinning groove; the first direction and the second direction are perpendicular to each other.

[0008] The edge of the first adhesive layer is spaced a certain distance from the edge of the negative electrode sheet, forming a locally thinned groove structure. In this structure, the thickness of the negative electrode paste is less than that of other areas, thus creating an electrolyte-rich area with better electrolyte wettability. The electrolyte contacts the copper foil, leading to copper deposition. Furthermore, this invention targets high-voltage systems with a charging cutoff voltage ≥4.48V. These systems are more prone to situations where the negative electrode potential is lower than the copper deposition potential, resulting in a significantly higher risk of copper foil corrosion and copper deposition compared to conventional voltage systems.

[0009] The battery of this invention, by placing a first adhesive layer in the thinning groove of the negative electrode and a second adhesive layer on the positive electrode tab, ensures that the orthogonal projection of the second adhesive layer in a plane perpendicular to the second direction lies within the thinning groove. The second adhesive layer can be assembled into the thinning groove with the battery, sharing the groove space with the first adhesive layer. This effectively reduces the volume available for electrolyte accumulation in the thinning groove area, suppressing the risk of copper foil deposition due to localized electrolyte enrichment. This extends the battery's cycle life and avoids internal short circuits caused by copper ion deposition inside the battery, significantly reducing the risk of thermal runaway in high-voltage battery systems and significantly improving the safety and cycle life of batteries with high charging cut-off voltages.

[0010] Furthermore, by controlling the range of the first gap L1 between the thinning groove and the first edge of the negative electrode sheet, it is possible to avoid L1 being too large, which would cause the thinning groove to shift inward towards the negative electrode sheet, failing to effectively occupy the empty volume within the groove and reduce electrolyte accumulation, thus hindering the suppression of copper foil corrosion. Conversely, L1 should not be too small, as this would cause the thinning groove to be too close to the first edge of the negative electrode sheet, and the edge of the first adhesive layer to be too close to the electrode sheet cutting edge, making it prone to peeling and detachment of the first adhesive layer during electrode processing and winding, leading to electrode edge structural failure. In this embodiment, by controlling L1 within the aforementioned reasonable range, the structural stability of the electrode edge can be guaranteed, while minimizing excess cavity within the thinning groove. This reduces the risk of local electrolyte accumulation at the source, effectively suppressing copper foil corrosion and copper deposition, and improving the cycle life and safety of high-voltage batteries with a charging cutoff voltage ≥4.48V.

[0011] Therefore, the battery of the present invention has the advantages of reducing the risk of local enrichment of electrolyte in the thinning tank area and suppressing copper foil precipitation.

[0012] In one embodiment, the negative electrode sheet includes a negative current collector and a negative active layer disposed on at least one side of the negative current collector in the thickness direction. The negative active layer on at least one side includes a silicon-carbon particle layer and a graphite active layer. The graphite active layer is disposed on the negative current collector, the silicon-carbon particle layer is located on the graphite active layer, and the thinning groove is formed on the silicon-carbon particle layer.

[0013] In one embodiment, the battery further includes an electrolyte, which further comprises LiTFSI, wherein the content of LiTFSI is 2% to 15% of the total mass of the electrolyte. In one embodiment, the electrolyte further comprises vitamin C, and the content of vitamin C is from 0.01% to 2% of the total mass of the electrolyte.

[0014] In one embodiment, the second adhesive layer is at least one of polypropylene, resin, phenolic resin, or ceramic.

[0015] In one embodiment, in the third-party direction, the length of the second adhesive layer is W1, where W1 satisfies: 0.5 ≤ W1 ≤ 2.5 mm.

[0016] In one embodiment, the width of the positive electrode tab is W2, and the relationship between W1 and W2 satisfies: 0.9≤W1 / W2≤1; the first direction, the second direction, and the third direction are arranged perpendicular to each other.

[0017] In one embodiment, in the first direction, the second adhesive layer has a third edge and a fourth edge disposed opposite to each other along the first direction, the third edge being disposed close to the first edge, and the distance between the third edge and the fourth edge in the first direction is L2, where L2 satisfies: 0.5≤L2≤2.5mm.

[0018] In one embodiment, in the orthographic projection of a plane perpendicular to the second direction, along the first direction, the distance between the third edge and the wall of the thinning groove on the side near the first edge is L3, where 0.1≤L3≤5mm.

[0019] In one embodiment, in an orthographic projection onto a plane perpendicular to the second direction, the projection of the fourth edge falls onto the first adhesive layer.

[0020] In one embodiment, in the first direction, the second adhesive layer has a third edge and a fourth edge disposed opposite to each other along the first direction.

[0021] In the first direction, the first adhesive layer has a fifth edge and a sixth edge disposed opposite to each other along the first direction, the fifth edge being disposed close to the first edge; the distance between the fourth edge and the fifth edge is L4, L4 satisfying: 0 < L4 ≤ 1.5 mm.

[0022] In one embodiment, in the first direction, the distance between the fifth edge of the first adhesive layer and the edge of the thinning groove is L5, where L5 satisfies: 0.1≤L5≤5mm.

[0023] In one embodiment, in the first direction, the positive electrode sheet has an arc-shaped notch at its first end. In the orthographic projection of a plane perpendicular to the second direction, the projection of the positive electrode tab at the first end falls within the arc-shaped notch, and the distance between the edge of the second adhesive layer and the bottom of the notch is L6, where L6 > 0.

[0024] In one embodiment, 0.1 ≤ L1 ≤ 1.5 mm.

[0025] In one embodiment, in the second direction, the thickness of the second adhesive layer is H1, the depth of the thinning groove is H3, and the relationship between H1 and H3 satisfies: 0.5 ≤ H1 / H3 ≤ 1.

[0026] In one embodiment, the thickness of the first adhesive layer is H2, and in the orthographic projection onto a plane perpendicular to the second direction, the orthographic projection of the second adhesive layer at least partially overlaps with the first adhesive layer, where 0.5 ≤ (H2 + H1) / H3 ≤ 1.1.

[0027] In one embodiment, the thickness H1 of the second adhesive layer is 5 μm to 80 μm.

[0028] In one embodiment, the thickness H2 of the first adhesive layer satisfies: 10μm < H2 ≤ 20μm.

[0029] In one embodiment, the battery further includes a first adhesive tape, which is attached to the positive electrode tab and the surface of the second adhesive layer. The thickness of the first adhesive tape is H4, and the relationship between H1 and H4 satisfies 0.25≤H1 / H4≤8, where H4 is 10μm~20μm. Preferably, 0.5 ≤ H1 / H4 ≤ 2. Attached Figure Description

[0030] Figure 1 This is a cross-sectional view of the electrode assembly according to an embodiment of the present invention.

[0031] Figure 2 yes Figure 1 A partially enlarged view of the cross-section along the first direction at point A.

[0032] Figure 3 This is a diagram showing the fit between the positive electrode sheet and the second adhesive layer in an embodiment of the present invention, as well as the region of the negative electrode sheet and the first adhesive layer embedded in the adhesive groove in the middle region of the positive electrode ear image.

[0033] Figure 4 This is a schematic diagram showing the positions of the positive electrode sheet, positive electrode tab, first adhesive layer, and second adhesive layer in an embodiment of the present invention.

[0034] Figure 5 This is a perspective view of the electrode assembly according to an embodiment of the present invention.

[0035] Explanation of reference numerals in the attached figures: Negative electrode 1; Negative electrode active layer 11; Thinning groove 12; First edge 13; Second edge 14; Positive electrode 2; First adhesive layer 3; Positive electrode 4; Arc-shaped notch 41; Second adhesive layer 5; Third edge 51; Fourth edge 52; 6. Insulating tape; 7. Diaphragm. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0037] The following is for reference. Figures 1-5 The battery of the present invention will be described by way of example.

[0038] The battery's charging cut-off voltage is ≥4.48V.

[0039] The battery of this invention includes an electrode assembly, a first adhesive layer 3, a positive electrode tab 4, and a second adhesive layer 5. The electrode assembly includes a core structure formed by stacking and winding a negative electrode sheet 1, a separator 7, and a positive electrode sheet 2. The negative electrode sheet 1 includes a thinning groove 12 formed in the negative electrode active layer 11, the thickness of the negative electrode active layer 11 within the thinning groove 12 being less than the thickness of the negative electrode active layer 11 in the region of the negative electrode sheet 1 outside the thinning groove 12. Along a first direction, the negative electrode sheet 1 has a first edge 13 and a second edge 14 disposed opposite to each other, the thinning groove 12 being disposed close to the first edge 13, and the thinning groove 12 and the first edge 13 having a first gap L1. 0 < L1 ≤ 1.5 mm; the first adhesive layer 3 is located within the thinning groove 12; the positive electrode tab 4 is electrically connected to the positive electrode sheet 2, and along the first direction, a portion of the positive electrode tab 4 extends beyond the first edge 13. In the orthographic projection of the plane perpendicular to the second direction, a portion of the positive electrode tab 4 is located within the thinning groove 12; the second adhesive layer 5 is disposed on the positive electrode tab 4, and in the orthographic projection of the plane perpendicular to the second direction, the projection of the second adhesive layer 5 is located within the thinning groove 12; the first direction and the second direction are perpendicularly arranged.

[0040] It should be noted that the edge of the first adhesive layer 3 is spaced a certain distance from the edge of the negative electrode sheet 1, forming a locally thinned groove 12 structure. In this structure, the thickness of the negative electrode paste is less than that of other areas, thus forming an electrolyte-rich area with better electrolyte wettability than other areas. The electrolyte comes into contact with the copper foil, leading to copper deposition. Furthermore, this invention targets high-voltage systems with a charging cutoff voltage ≥4.48V. Such systems are more prone to situations where the negative electrode potential is lower than the copper deposition potential, resulting in a significantly higher risk of copper foil corrosion and copper deposition compared to conventional voltage systems.

[0041] It should also be noted that the electrode assembly is wound along the length of the positive / negative electrode 1, with the first direction being the width direction of the positive / negative electrode 1 and the second direction being the thickness direction of the electrode assembly.

[0042] The first edge 13 and the second edge 14 are the edges of the negative electrode 1 along the width direction. Along the second direction, the first edge 13 extends beyond one side edge of the corresponding positive electrode 2, and the second edge 14 extends beyond the other side edge of the corresponding positive electrode 2, i.e., the overhang region.

[0043] In this embodiment of the battery, a first adhesive layer 3 is disposed within the thinning groove 12 of the negative electrode sheet 1, and a second adhesive layer 5 is disposed on the positive electrode tab 4. The orthogonal projection of the second adhesive layer 5 in a plane perpendicular to the second direction lies within the thinning groove 12. The second adhesive layer 5 can be assembled into the thinning groove 12 along with the first adhesive layer 3, occupying the space within the groove. This effectively reduces the volume available for electrolyte accumulation in the thinning groove 12 area, suppressing the risk of copper foil deposition due to localized electrolyte enrichment. This extends the battery's cycle life and avoids internal short circuits caused by copper ion deposition inside the battery, significantly reducing the risk of thermal runaway in high-voltage battery systems and significantly improving the safety and cycle life of batteries with high charging cutoff voltages.

[0044] Furthermore, by controlling the range of the first gap L1 between the thinning groove 12 and the first edge 13 of the negative electrode 1, it is possible to avoid L1 being too large, which would cause the thinning groove 12 to shift inward towards the negative electrode 1, failing to effectively occupy the empty volume within the groove and reduce electrolyte accumulation, thus hindering the suppression of copper foil deposition. Simultaneously, it is also to avoid L1 being too small, which would cause the thinning groove 12 to be too close to the first edge 13 of the negative electrode 1, and the edge of the first adhesive layer 3 to be too close to the electrode cutting edge, making it prone to lifting and detachment of the first adhesive layer 3 during electrode processing and winding, leading to electrode edge structural failure. In this embodiment, by controlling L1 within the aforementioned reasonable range, the structural stability of the electrode edge can be guaranteed, the risk of local electrolyte accumulation can be reduced, copper foil corrosion and deposition can be effectively suppressed, and the cycle life and safety of high-voltage batteries with a charging cutoff voltage ≥4.48V can be improved.

[0045] Therefore, the battery of the present invention has the advantages of reducing the risk of local enrichment of electrolyte in the thinning tank 12 region and suppressing copper foil precipitation.

[0046] Preferably, the charging cut-off voltage of the battery is ≥4.53V. Under this high-voltage, high-energy-density system, the structure of the present invention has a more prominent effect on suppressing the risk of copper plating on copper foil, and can effectively solve the problem of copper plating failure during long-term cycling of high-voltage batteries while ensuring battery energy output.

[0047] Preferably, L1 can be 0.2mm, 0.5mm, 0.8mm, 1.0mm, 1.5mm, or any range between two point values.

[0048] like Figures 1 to 3As shown, the negative electrode 1 includes a negative electrode current collector and a negative electrode active layer 11 disposed on at least one side in the thickness direction of the negative electrode current collector. The negative electrode active layer 11 on at least one side includes a silicon carbon particle layer and a graphite active layer. The graphite active layer is disposed on the negative electrode current collector, the silicon carbon particle layer is located on the graphite active layer, and the thinning groove 12 is formed on the silicon carbon particle layer.

[0049] The battery of this invention features a double-layer structure comprising a silicon-carbon particle layer and a graphite active layer on the negative electrode 1, with a thinning groove 12 formed on the upper silicon-carbon particle layer. This ensures that only the graphite active layer with a low expansion rate is retained in the thinning groove 12 region, while completely removing the silicon-carbon particle layer, which expands significantly during charging and discharging. This substantially reduces the volume change of the thinning groove 12 region during cycling, effectively preventing the risk of the active material expanding and causing the first adhesive layer 3 (such as tab protectant) within the thinning groove 12 to detach. Furthermore, placing the silicon-carbon particle layer on the surface improves the conductivity of the negative electrode 1, reduces its longitudinal polarization, and prevents copper deposition due to excessively low negative electrode potential under high voltage conditions.

[0050] The battery in this embodiment of the invention also includes an electrolyte, which further contains lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Based on the total mass of the electrolyte, the content of lithium bis(trifluoromethanesulfonyl)imide is 2% to 15% of the total mass of the electrolyte.

[0051] The battery of this invention, by adding lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) at a content of 2% to 15% of the total mass in the electrolyte, helps to reduce the negative electrode potential when the battery's charging cut-off voltage is ≥4.48V, thereby suppressing the deposition of copper ions.

[0052] Simultaneously, LiTFSI preferentially adsorbs and forms a film on the copper foil surface exposed in the thinning tank 12 region, creating a stable passivation protective layer. This prevents direct contact between the electrolyte and the copper foil substrate, reducing copper foil corrosion and inhibiting copper ion deposition. This effectively solves the copper foil deposition problem in high-voltage battery systems, further improving battery cycle life, reducing the risk of internal short circuits and thermal runaway, and enhancing battery safety and reliability under high-voltage conditions.

[0053] Optionally, based on the total mass of the electrolyte, the content of lithium bis(trifluoromethanesulfonyl)imide is 2%, 5%, 8%, 11%, or 15% of the total mass of the electrolyte, or a range between any two point values.

[0054] The electrolyte also contains vinylene carbonate, and the content of vinylene carbonate is 0.01% to 2% of the total mass of the electrolyte.

[0055] The battery of this invention uses vinylene carbonate (VC) in an electrolyte at a content of 0.01% to 2% of the total mass. VC has excellent antioxidant properties and can inhibit the oxidative decomposition reaction of the electrolyte under high voltage system, thereby reducing problems such as increased internal pressure and increased internal resistance of the battery caused by the decomposition of electrolyte.

[0056] Meanwhile, VC can work synergistically with LiTFSI to form a more stable and dense composite passivation protective film on the exposed copper foil surface, further improving the structural stability of the passivation film, preventing the protective film from cracking or falling off during long-term charge-discharge cycles, continuously blocking direct contact between the copper foil substrate and the electrolyte, and persistently inhibiting copper foil corrosion and copper ion deposition, thereby further improving the cycle life and structural stability of the battery.

[0057] Optionally, based on the total mass of the electrolyte, the content of vinylene carbonate is 0.01%, 0.1%, 0.5%, 1%, 1.5% or 2% of the total mass of the electrolyte, or a range between any two point values.

[0058] The second adhesive layer 5 is at least one of polypropylene, resin, phenolic resin, or ceramic.

[0059] The battery of this invention, by using the above-mentioned materials to prepare the second adhesive layer 5, can ensure that the second adhesive layer 5 has excellent structural strength and insulation performance, and the materials used have good rubber-based adhesive paper compatibility, so that the filling will not fail or new side reaction products will be introduced due to material deterioration. Moreover, it is relatively stable in a low temperature range (<100℃), so no harmful side reactions will occur during battery operation, and no impurities will be introduced to affect the electrochemical performance of the battery, thereby improving battery safety and cycle life.

[0060] In the third direction, the length of the second adhesive layer 5 is W1, and W1 satisfies: 0.5≤W1≤2.5mm.

[0061] In this embodiment of the battery, by limiting the range of the length W1 of the second adhesive layer 5, the following advantages are achieved: Firstly, if W1 is too small, the second adhesive layer 5 cannot fully fill the thinning groove 12, making it difficult to prevent localized electrolyte accumulation in the thinning groove 12 region, resulting in insufficient suppression of copper plating on the copper foil. Secondly, if W1 is too large, the second adhesive layer 5 will extend beyond the thinning groove 12 into the active region outside the thinning groove 12, further encroaching on the space for the negative electrode active material and causing a decrease in the overall energy density of the battery. Therefore, by reasonably setting the range of W1, both the energy density of the battery and the suppression of copper plating on the copper foil can be simultaneously considered.

[0062] Optionally, W1 can be 0.5mm, 0.8mm, 1.0mm, 1.5mm, 2.0mm, or 2.5mm, or a range between any two point values.

[0063] like Figures 1 to 3 As shown, the width of the positive electrode tab 4 is W2, and the relationship between W1 and W2 satisfies: 0.9≤W1 / W2≤1, and the first direction, the second direction and the third direction are set perpendicular to each other.

[0064] The battery in this embodiment of the invention, by limiting the ratio of W1 to the width W2 of the positive electrode tab 4 within the aforementioned range, avoids two issues. First, W1 / W2 is less than 0.9, which would prevent the positive electrode tab 4 from fully covering the projected area within the thinning groove 12, leaving a large amount of uncovered space for electrolyte accumulation and insufficient suppression of copper plating on the copper foil. Second, W1 / W2 is greater than 1, which would additionally encroach on the arrangement space of the negative electrode active layer 11 outside the thinning groove 12, causing a loss in the overall energy density of the battery. It could also interfere with surrounding structures during the winding process, affecting the forming accuracy and structural stability of the core. By controlling W1 / W2 within the range of this embodiment, both the energy density and safety performance of the battery are taken into account, which is beneficial for high-voltage battery systems to simultaneously achieve high energy density and long cycle life.

[0065] Optionally, W1 / W2 can be 0.9, 0.92, 0.94, 0.95, 0.98, or 1, as well as a range of values ​​between any two points.

[0066] like Figures 1 to 3 As shown, in the first direction, the second adhesive layer 5 has a third edge 51 and a fourth edge 52 disposed opposite to each other along the first direction. The third edge 51 is disposed close to the first edge 13, and the distance between the third edge 51 and the fourth edge 52 is L2, which satisfies: 0.5≤L2≤2.5mm.

[0067] In this embodiment of the battery, by limiting the range of the length L2 of the second adhesive layer 5 in the first direction, it avoids two problems. Firstly, if L2 is too small, the second adhesive layer 5 cannot fully cover the extension range of the thinning groove 12 along the first direction, leading to localized electrolyte enrichment and the risk of copper foil deposition. Secondly, it avoids if L2 is too large, the second adhesive layer 5 will crowd out the active area of ​​the negative electrode 1, and there will be problems such as edge lifting and detachment of the second adhesive layer 5. Controlling L2 within the above range reduces the risk of copper foil deposition and further improves the overall electrochemical performance and safety of the high-voltage battery system with a charging cutoff voltage ≥4.48V.

[0068] Optionally, L2 can be 0.5mm, 0.8mm, 1.0mm, 1.5mm, 2.0mm, or 2.5mm, or a range between any two point values.

[0069] like Figures 1 to 3 As shown, in the orthographic projection of the plane perpendicular to the second direction, the distance between the third edge 51 and the edge of the non-thinning groove 12 is L3, 0.1≤L3≤5mm.

[0070] The battery of this embodiment limits the distance L3 between the third edge 51 and the edge of the non-thinning groove 12 of the negative electrode sheet 1. On the one hand, this avoids L3 being too small, causing the third edge 51 to be too close to the negative electrode active layer 11 in the non-thinning groove 12 region, excessively occupying the effective placement space of the negative electrode active material, which could easily lead to problems such as the second adhesive layer 5 or the active material swelling and lifting or falling off. On the other hand, it avoids L3 being too large, causing the third edge 51 to be too far from the non-thinning groove 12, which would prevent the second adhesive layer 5 from completely filling the empty volume at the corresponding position of the thinning groove 12, resulting in local enrichment of electrolyte and the risk of copper foil deposition, thereby improving the high-voltage safety of the battery.

[0071] Optionally, L3 can be 0.1mm, 0.5mm, 1mm, 2mm, 3mm or 5mm and any range between two point values.

[0072] like Figures 1 to 3 As shown, in the orthographic projection onto a plane perpendicular to the second direction, the projection of the fourth edge 52 falls onto the first adhesive layer 3.

[0073] In the battery embodiment of the present invention, by making the orthographic projection of the fourth edge 52 of the second adhesive layer 5 onto the first adhesive layer 3 in a plane perpendicular to the second direction, it is ensured that the second adhesive layer 5 and the first adhesive layer 3 located in the thinning tank 12 form a covering and overlapping relationship in the vertical direction. This allows the second adhesive layer 5 to cooperate with the first adhesive layer 3 to occupy the space in the tank, reducing the accumulation of electrolyte in the thinning tank 12, thereby effectively suppressing the risk of copper foil deposition caused by local enrichment of electrolyte.

[0074] At the same time, applying a certain pressure to the first adhesive layer 3 by utilizing the overlapping part helps to enhance the adhesion stability of the first adhesive layer 3 at the bottom of the thinning groove 12, prevents it from falling off due to the expansion of the active material, reduces the incidence of filling failure caused by the falling off of the first adhesive layer 3, and improves the overall reliability of the filling structure.

[0075] like Figures 1 to 3 As shown, in the first direction, the first adhesive layer 3 has a fifth edge and a sixth edge disposed opposite to each other along the first direction. The fifth edge is disposed close to the first edge 13. The distance between the fourth edge 52 and the fifth edge is L4, and L4 satisfies: 0 < L4 ≤ 1.5 mm.

[0076] In the battery embodiment of the present invention, by setting the first adhesive layer 3 near the fifth edge of the first edge 13 of the negative electrode 1 in the first direction at the near end position in the thinning groove 12, the first adhesive layer 3 can fill the space in the groove from the side of the thinning groove 12 near the edge of the electrode, thereby more effectively covering and occupying the volume of the area near the groove opening in the thinning groove 12, reducing the local enrichment space of electrolyte in this area, further improving the effect of suppressing the risk of copper foil precipitation, and enhancing the reliability of the overall filling structure.

[0077] Furthermore, in this embodiment of the invention, the distance L4 between the fourth edge 52 of the second adhesive layer 5 and the fifth edge of the first adhesive layer 3 is limited to be greater than 0 and not greater than 1.5 mm, which avoids the overlap area between the second adhesive layer 5 and the first adhesive layer 3 being too wide and prevents the excessive increase in local thickness from having an adverse effect on the flatness of the battery stack or the energy density.

[0078] Optionally, L4 can be 0.1mm, 0.3mm, 0.5mm, 0.8mm, 1.0mm, 1.2mm or 1.5mm, or a range between any two point values.

[0079] like Figures 1 to 3 As shown, in the first direction, at the first end, the distance between the fifth edge of the first adhesive layer 3 and the edge of the thinning groove 12 is L5, and L5 satisfies: 0.1≤L5≤5mm.

[0080] In this embodiment of the battery, by limiting the distance L5 between the fifth edge of the first adhesive layer 3 and the edge of the thinning groove 12 to within the aforementioned range, it avoids two problems. Firstly, if L5 is too small, the fifth edge of the first adhesive layer 3 would be too close to the edge of the thinning groove 12, making it easy to pull the edge of the first adhesive layer 3 during electrode processing and cutting, causing the first adhesive layer 3 to lift and fall off, ultimately leading to the failure of the thinning groove 12 to fill, increasing the risk of localized copper deposition in the electrolyte. Secondly, it avoids if L5 is too large, causing the first adhesive layer 3 to shift inwards towards the thinning groove 12, failing to effectively fill the empty volume near the electrode edge of the thinning groove 12, leaving space for electrolyte accumulation, and failing to achieve the expected effect of inhibiting copper deposition. Therefore, this embodiment, by controlling L5 within the aforementioned reasonable range, balances the energy density, cycle life, and safety of the high-voltage battery system.

[0081] Optionally, L5 can be 0.1mm, 0.5mm, 1mm, 2mm, 3mm or 5mm and any range between two point values.

[0082] like Figures 1 to 3As shown, in the first direction, the positive electrode 2 has an arc-shaped notch 41 at its first end. In the orthographic projection of the plane perpendicular to the second direction, the projection of the positive electrode tab 4 at the first end falls within the arc-shaped notch 41. The distance between the edge of the second adhesive layer 5 and the bottom of the notch is L6, where L6 > 0.

[0083] The battery of this embodiment of the invention, by setting an arc-shaped notch 41 at the first end of the positive electrode plate 2 and making the projection of the positive electrode tab 4 fall into the notch, effectively avoids the problem of excessive total thickness of the tab area caused by the excessive superposition of the positive electrode tab 4 and the positive electrode plate 2 body, further releasing the usable space inside the cell, which is conducive to improving the overall energy density of the battery.

[0084] Furthermore, by controlling the distance L6 between the edge of the second adhesive layer 5 and the bottom of the notch to be greater than 0, it is ensured that the second adhesive layer 5 will not extend to the bottom area of ​​the arc-shaped notch 41 of the positive electrode 2 along the first direction. This avoids unnecessary overlap or contact between the second adhesive layer 5 and the main body of the positive electrode 2 (excluding the area of ​​the tab). It effectively prevents the risk of local current blockage, increased contact resistance, or internal short circuit that may be caused by the second adhesive layer 5 covering the surface of the positive current collector (aluminum foil). At the same time, the existence of this gap provides sufficient space for the welding area of ​​the tab, avoiding interference of the second adhesive layer 5 with the welding process of the tab and the external circuit, and ensuring the reliability of the electrical connection.

[0085] Optionally, L6 can be 0.1mm, 0.2mm, 0.5mm, 0.8mm, 1mm, 1.5mm, 2mm or 3mm, or a range between any two point values.

[0086] Preferably, 0.1 ≤ L1 ≤ 1.5 mm.

[0087] The battery in this embodiment of the invention, by further optimizing the range of L1, avoids problems such as edge coating damage, current collector exposure, or decreased electrode end strength caused by the thinning groove 12 opening extending to the electrode end. This reduces the risk of burrs or powder shedding at the electrode edge, thereby preventing the risk of internal short circuits caused by these issues. Simultaneously, by limiting L1 to no more than 1.5 mm, the excessive gap between the thinning groove 12 and the electrode edge is avoided, preventing the risk of localized electrolyte accumulation within the thinning groove 12 and the excessive encroachment on the effective coating space of the negative electrode active material, which would lead to a decrease in the overall energy density of the battery.

[0088] like Figures 1 to 3 As shown, in the second direction, the thickness of the second adhesive layer 5 is H1, and the depth of the thinning groove 12 is H3. The relationship between H1 and H3 satisfies: 0.5≤H1 / H3≤1.

[0089] The battery of this embodiment of the invention ensures that the second adhesive layer 5 can occupy half to all of the depth of the thinning groove 12 by adjusting the ratio range of the thickness H1 of the second adhesive layer 5 to the depth H3 of the thinning groove 12. This effectively reduces the volume of electrolyte accumulation in the area and suppresses the risk of copper foil deposition caused by local enrichment of electrolyte.

[0090] At the same time, this ratio does not exceed 1, which avoids local bulges or assembly interference caused by the thickness of the second adhesive layer 5 exceeding the depth of the thinning groove 12, and prevents the impact of overfilling on the flatness or energy density of the battery stack.

[0091] Optionally, H1 / H3 can be 0.5, 0.6, 0.7, 0.8, 0.9, or 1, or a range of values ​​between any two points.

[0092] like Figures 1 to 3 As shown, the thickness of the first adhesive layer 3 is H2. In the orthographic projection of the plane perpendicular to the second direction, the orthographic projection of the second adhesive layer 5 at least partially overlaps with the first adhesive layer 3, and 0.5≤(H2+H1) / H3≤1.1.

[0093] In this embodiment of the battery, the second adhesive layer 5 and the first adhesive layer 3 at least partially overlap in projection, and the ratio of the sum of their thicknesses (H2+H1) to the depth (H3) of the thinning groove 12 is controlled between 0.5 and 1.1. This ensures that the total filling thickness in the overlapping area is at least half the groove depth, thereby effectively occupying the space within the thinning groove 12 where electrolyte can accumulate, and suppressing the risk of copper foil deposition caused by local electrolyte enrichment. On the other hand, the upper limit of this ratio is no more than 1.1, allowing the total filling thickness to be slightly greater than the groove depth, preventing the filling structure from protruding excessively from the groove surface, which could lead to abnormal local thickness of the battery, excessive pressure on the stacked structure, or affect the energy density.

[0094] Optionally, (H2+H1) / H3 can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.05 or 1.1, or a range between any two point values.

[0095] Furthermore, such as Figures 1 to 3 As shown, the thickness H1 of the second adhesive layer 5 is 5μm to 80μm. The thickness H2 of the first adhesive layer 3 satisfies: 10μm < H2 ≤ 20μm.

[0096] In the battery embodiment of the present invention, by limiting the thickness H1 of the second adhesive layer 5 to between 5μm and 25μm, it is ensured that it has sufficient volume to effectively fill the remaining space in the thinning groove 12, thereby reducing the local enrichment of electrolyte. If H1 is too small (e.g., less than 5μm), the filling effect is insufficient and it cannot fully occupy the volume of the groove, thus weakening the effect of inhibiting electrolyte enrichment. If H1 is too large (e.g., more than 25μm), it may exceed the upper limit of the total thickness after the depth of the thinning groove 12 and the first adhesive layer 3 are superimposed, resulting in local bulges and affecting the flatness of the battery stack or the assembly accuracy.

[0097] Meanwhile, the thickness H2 of the first adhesive layer 3 is limited to be greater than 0 and not more than 1.5 mm, which ensures that the first adhesive layer 3 has a certain thickness to achieve the function of adhesion and filling at the bottom of the thinning groove 12. If H2 is too small (close to 0), the first adhesive layer 3 is too thin and may not be able to effectively fill the gap at the bottom of the thinning groove 12 or adhere firmly, and may fall off easily during the cycle. If H2 is too large (more than 1.5 mm), it will cause energy density loss or local stress concentration.

[0098] Optionally, the thickness H1 of the second adhesive layer 5 is 5μm, 10μm, 15μm, 20μm, 25μm, 35μm, 45μm, 60μm, 70μm, 80μm, or any range between two point values.

[0099] Optionally, the thickness H2 of the first adhesive layer 3 is 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, or a range between any two point values.

[0100] like Figures 1 to 3 As shown, the battery in this embodiment of the invention also includes a first adhesive tape, which is attached to the surface of the positive electrode tab 4 and the second adhesive layer 5. The thickness of the first adhesive tape is H4, and the relationship between H1 and H4 satisfies 0.25≤H1 / H4≤8, where H4 is 10μm~20μm.

[0101] The battery of this invention limits the thickness H4 range of the first adhesive layer and controls the ratio of the thickness H1 of the second adhesive layer 5 to the thickness H4 of the first adhesive layer to be within the range of 0.25 to 8. On the one hand, if the H1 / H4 ratio is too small, it means that the second adhesive layer 5 is too thin relative to the first adhesive layer, which may result in insufficient filling function of the second adhesive layer 5, and the first adhesive layer may bulge locally due to being too thick, affecting the flatness of the electrode area and the overall energy density.

[0102] like Figures 1 to 3As shown, on the other hand, if the H1 / H4 ratio is too large (e.g., greater than 8), the second adhesive layer 5 will be too thick, and the first adhesive paper, being relatively thin, will be unable to fully wrap and fix the second adhesive layer 5. This can easily cause the second adhesive layer 5 to shift or fall off during cycling. At the same time, uneven overall thickness may cause local stress on the battery stack structure. The first adhesive paper provides stable coverage and protection, and the second adhesive layer 5 effectively fills the space of the thinning groove 12, thereby suppressing the risk of electrolyte accumulation and improving the long-term stability of the battery.

[0103] Optionally, H1 / H4 can be 0.25, 0.5, 1, 2, 3, 4, 6, or 8, or a range between any two point values. Preferably, 0.5 ≤ H1 / H4 ≤ 2.

[0104] Optionally, H4 can be 10μm, 12μm, 14μm, 15μm, 16μm, 18μm, or 20μm, or a range between any two point values.

[0105] Furthermore, insulating tape 6 can be applied to the electrode assembly for fixation.

[0106] This application allows for the measurement of the determined length, depth, and thickness using a 2.5D microscope.

[0107] Example 1 Core preparation: Preparation of positive electrode 2: Lithium cobalt oxide, conductive agent, PVDF are mixed in a mass ratio of 97:1:2, and NMP is added. The mixture is stirred evenly to prepare a positive electrode slurry. The positive electrode slurry is coated on both sides of an aluminum foil. After baking and rolling, a positive electrode 2 with a thickness of 100μm is obtained. A groove of a fixed size is provided at a certain position of the positive electrode 2. The nickel positive electrode tab 4 is welded into this groove by laser or ultrasonic welding. PP adhesive is set on the metal strip of the positive electrode tab 4 as a second adhesive layer 5.

[0108] Preparation of negative electrode 1: Graphite, silicon carbon particles, conductive carbon, CMC-Li, and PAA are mixed in a mass ratio of 87.5:9.7 (silicon carbon accounts for 10% of the weight of graphite, and spherical silicon carbon contains 40% silicon) 0.05:0.35:2.4, and deionized water is added to prepare a negative electrode slurry; the negative electrode slurry is coated on both sides of a carbon-coated copper foil, and after baking and rolling, a negative electrode 1 with a thickness of 110μm is obtained. A groove of fixed size is provided at a certain position of the negative electrode 1, and a copper-plated nickel positive electrode tab 4 is welded into this groove by laser or ultrasonic welding; linear thinning grooves 12 with a width of 80μm and a spacing of 1m are made on the surface of the negative electrode using a laser. After the positive and negative electrode sheets 1 are slit and formed, they are wound with the separator 7 to obtain a core. The separator 7 used is a 5μm PE base film, a 2μm polyacrylonitrile organic coating, and a 2.5μm second adhesive layer 5 (including a 2μm PMMA+PVDF mixed coating covering the organic coating and a 0.5μm pure PMMA adhesive layer on the base film surface). After encapsulation, a heat-fusible first adhesive layer 3 with a melting point of 120℃ is placed at the side sealing edge. Its width is 1.5mm and its length is 45mm. The first adhesive layer 3 is 15mm away from the top of the cell. Then, after baking, liquid injection, formation, secondary sealing, sorting and OCV, the edge is folded and glued to obtain a lithium-ion battery. The height of the lithium-ion battery is 90mm.

[0109] Electrolyte preparation: In an argon glove box with a water content of <0.1ppm and an oxygen content of <0.1ppm, carbonates (EC and PC in a mass ratio of 1:1) and carboxylic acids (PP, EP, and DFEA in a mass ratio of 1:1:10) were mixed evenly at a mass ratio of 1:6. Then, fluoroethylene carbonate, lithium hexafluorophosphate, and lithium bis(trifluoromethanesulfonyl)imide were added to obtain the electrolyte. Based on the total mass of the electrolyte, the content of fluoroethylene carbonate was 13.7%, the content of lithium hexafluorophosphate was 15%, the content of lithium bis(trifluoromethanesulfonyl)imide was 7%, and the remainder was carbonates and carboxylic acids.

[0110] The first gap L1 between the thinning groove 12 and the first edge 13 is 0.8mm, the distance L2 between the third edge 51 and the fourth edge 52 is 1.5mm, the distance L3 between the third edge 51 and the edge of the non-thinning groove 12 is 2mm, the distance L4 between the fourth edge 52 and the fifth edge is 0.8mm, the distance L5 between the fifth edge of the first adhesive layer 3 and the edge of the thinning groove 12 is 2.5mm, the distance L6 between the edge of the second adhesive layer 5 and the bottom of the notch is 5mm, the length W1 of the second adhesive layer 5 is 2mm, the width W2 of the positive electrode tab 4, W1 / W2 is 0.9, the thickness H1 of the second adhesive layer 5 is 8mm, the thickness H2 of the first adhesive layer 3 is 0.5mm, H1 / H3 is 0.8, (H2+H1) / H3 is 0.88, and H1 / H4 is 1.

[0111] Table 1 Where L3 = L5 + L4 - L2; L3 is a negative number, indicating that there is an overlap between the two, and the third edge 51 extends beyond the edge of the non-thinning groove 12.

[0112] The specific settings of the embodiment are shown in Table 1, wherein the units of the data in Table 1 are the same as those in the specification.

[0113] Comparative Example 1 differs from Example 1 in that L1 is 5.2 mm.

[0114] Comparative Example 2 differs from Example 1 in that L1 is 0 mm.

[0115] Comparative Example 3 differs from Example 1 in that it does not have a second adhesive layer 5.

[0116] Charge-discharge cycle performance: This test was conducted entirely in a constant temperature environment of 25℃. The battery's rated capacity was used as the charge / discharge rate benchmark (1C rate corresponds to the current value of the battery's 1-hour charge / discharge rate). The test was completed using a standard battery charge / discharge testing system—NEWARE CT-9008-5V6A (BTS series), a constant temperature test chamber—ESPEC GPU-3B, and a thickness meter—Quankeruida CHY-02H. The specific steps are as follows: 1. Sample pretreatment: The lithium battery under test was placed in a constant temperature environment of 25℃ for 2 hours to allow the battery body temperature to reach thermal equilibrium with the ambient temperature.

[0117] 2. Initial baseline parameter test: ① Charge at a constant current rate of 1C until the charging cutoff voltage is 4.55V, then switch to constant voltage charging until the charging current drops to 0.05C and the charging is terminated. ② Use a thickness tester to test the center thickness of the main body area of ​​the battery cell (avoid the tabs and sealing edge areas), and record it as the initial full charge thickness h1; ③ After the battery has been left to stand for 10 minutes, it is discharged at a constant current of 0.5C until the discharge cutoff voltage of 3.0V is reached. The discharge capacity is then stopped and recorded as the initial discharge capacity Q1. ④ Let the battery rest for 10 minutes to complete the first charge-discharge cycle.

[0118] 3. Cyclic life test: Perform continuous cycle testing according to the charge and discharge regime described in step 2: each cycle sequentially performs 1C constant current and constant voltage charging, rest for 10 minutes, 0.5C constant current discharging, and rest for 10 minutes, accumulating 1000 charge and discharge cycles.

[0119] 4. Parameter testing after loop: After completing 1000 cycles, the charging, discharging and testing process in step 2 was completely repeated to obtain the full charge thickness h2 and the discharge capacity Q2 after the cycle.

[0120] 5. Performance parameter calculation: Capacity retention rate after 1000 cycles: Calculated using the following formula, with the result expressed as a percentage. Capacity retention rate = Q2 / Q1 × 100% Thickness expansion rate after 1000 cycles: Calculated using the following formula, with the result expressed as a percentage. Thickness expansion rate = h2 / h1×100%.

[0121] After copper ions are deposited, they enter the electrolyte, which not only affects the energy storage efficiency of the battery, but may also form deposits inside the battery, blocking the current channels inside the battery and causing a decrease in battery conductivity. Therefore, it is important to characterize the cycle performance.

[0122] 2. Adhesive layer curling rate / % Each group consists of 100 battery sets. Batteries that have undergone 1000 cycles are disassembled, and the probability of adhesive layer displacement and lifting is tested using visual inspection and optical instruments such as a 3D microscope. The area of ​​the lifted region (height exceeding a threshold) is divided by the total effective adhesive area. This is automatically calculated using a 3D profilometer pseudo-color image. The lifting area percentage (RA) is also calculated; RA > 5% is considered unacceptable.

[0123] 3. Battery energy density testing method: This test was conducted in a constant temperature environment of 25℃. The charge / discharge rate was based on the battery's rated capacity (1C rate corresponds to the current value of the battery's 1-hour charge / discharge rate). The test was completed using a battery charge / discharge test system—NEWARE CT-9008-5V6A (BTS series)—and a digital micrometer. The specific operating steps are as follows: 1. Sample thermal equilibrium pretreatment The lithium battery under test was placed in a constant temperature environment of 25°C for at least 2 hours to allow the battery body temperature to reach thermal equilibrium with the ambient temperature.

[0124] 2. Constant current and constant voltage charging Charge the battery at a constant current rate of 0.2C until the battery's rated charging cutoff voltage, then switch to constant voltage charging until the charging current drops to 0.02C and charging is terminated.

[0125] 3. Constant Current Discharge and Energy Harvesting After the battery is left to stand for 5 minutes, it is discharged at a constant current rate of 0.2C until the battery's rated discharge cutoff voltage is reached, and then the discharge is terminated. The total discharge energy of this discharge process is automatically recorded by the charge and discharge test system and denoted as E.

[0126] 4. Battery volume calculation After discharge and 5 minutes of rest, the external dimensions of the battery cell's main body area were measured using a dimensional measuring device: the length, width, and center thickness of the battery body were measured, avoiding non-cell main body structures such as tabs and encapsulation edges; the battery volume V was calculated using the following formula: V = Length × Width × Thickness The volumetric energy density (VED) of a single battery cell is calculated using the following formula: VED = E / V 5. Data Statistical Rules For each set of embodiments and comparative examples, at least 20 parallel test batteries were selected. The volumetric energy density of each battery was calculated, and the arithmetic mean was taken as the final volumetric energy density test result of the set.

[0127] Table 2 The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0128] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0129] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0130] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0131] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0132] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0133] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A battery, characterized in that, The battery has a charging cutoff voltage ≥4.48V, including: Electrode assembly, comprising a core structure formed by stacking and winding negative electrode, separator and positive electrode; The negative electrode sheet includes a thinning groove formed in the negative electrode active layer, and the thickness of the negative electrode active layer in the thinning groove is less than the thickness of the negative electrode active layer in the non-thinning groove region of the negative electrode sheet. Along the first direction, the negative electrode sheet has a first edge and a second edge disposed opposite to each other, the thinning groove is disposed close to the first edge, and the thinning groove and the first edge have a first gap L1, 0 < L1 ≤ 5 mm; The first adhesive layer is located within the thinning groove; A positive electrode tab is electrically connected to the positive electrode sheet. Along the first direction, a portion of the positive electrode tab extends beyond the first edge. In the orthographic projection of a plane perpendicular to the second direction, a portion of the positive electrode tab is located within the thinning groove. The second adhesive layer is disposed on the positive electrode tab, and in the orthographic projection of the plane perpendicular to the second direction, the projection of the second adhesive layer is located within the thinning groove; The first direction and the second direction are set perpendicularly.

2. The battery according to claim 1, characterized in that, The negative electrode sheet includes a negative current collector and a negative active layer disposed on at least one side of the negative current collector in the thickness direction. The negative active layer on at least one side includes a silicon-carbon particle layer and a graphite active layer. The graphite active layer is disposed on the negative current collector, the silicon-carbon particle layer is located on the graphite active layer, and the thinning groove is formed on the silicon-carbon particle layer.

3. The battery according to claim 2, characterized in that, It also includes an electrolyte, which further contains LiTFSI, wherein the content of LiTFSI is 2% to 15% of the total mass of the electrolyte. And / or, the electrolyte further comprises VC, and the content of VC is from 0.01% to 2% of the total mass of the electrolyte.

4. The battery according to claim 1, characterized in that, The second adhesive layer is at least one of polypropylene, resin, phenolic resin or ceramic.

5. The battery according to claim 1, characterized in that, In the third direction, the length of the second adhesive layer is W1, where W1 satisfies: 0.5≤W1≤2.5mm; And / or, the width of the positive electrode tab is W2, and the relationship between W1 and W2 satisfies: 0.9≤W1 / W2≤1; The first direction, the second direction, and the third direction are set perpendicular to each other.

6. The battery according to claim 1, characterized in that, In the first direction, the second adhesive layer has a third edge and a fourth edge disposed opposite to each other along the first direction, the third edge being disposed close to the first edge, and the distance between the third edge and the fourth edge in the first direction is L2, where L2 satisfies: 0.5≤L2≤2.5mm; In the orthographic projection of a plane perpendicular to the second direction, along the first direction, the distance between the third edge and the wall of the thinning groove on the side closer to the first edge is L3, 0.1≤L3≤5mm; And / or, in an orthographic projection onto a plane perpendicular to the second direction, the projection of the fourth edge falls onto the first adhesive layer.

7. The battery according to claim 1, characterized in that, In the first direction, the second adhesive layer has a third edge and a fourth edge disposed opposite to each other along the first direction; In the first direction, the first adhesive layer has a fifth edge and a sixth edge disposed opposite to each other along the first direction, the fifth edge being disposed close to the first edge; The distance between the fourth edge and the fifth edge is L4, where L4 satisfies: 0 < L4 ≤ 1.5 mm; And / or, in the first direction, the distance between the fifth edge of the first adhesive layer and the edge of the thinning groove is L5, where L5 satisfies: 0.1≤L5≤5mm; And / or, in the first direction, the positive electrode sheet has an arc-shaped notch at its first end, and in the orthographic projection of a plane perpendicular to the second direction, at the first end, the projection of the positive electrode tab falls within the arc-shaped notch, and the distance between the edge of the second adhesive layer and the bottom of the notch is L6, where L6 > 0; And / or, 0.1≤L1≤1.5mm.

8. The battery according to claim 1, characterized in that, In the second direction, the thickness of the second adhesive layer is H1, and the depth of the thinning groove is H3. The relationship between H1 and H3 satisfies: 0.5 ≤ H1 / H3 ≤ 1; and / or, And / or, the thickness of the first adhesive layer is H2, and in the orthographic projection onto a plane perpendicular to the second direction, the orthographic projection of the second adhesive layer at least partially overlaps with the first adhesive layer, 0.5≤(H2+H1) / H3≤1.

1.

9. The battery according to claim 5, characterized in that, The thickness H1 of the second adhesive layer is 5μm~80μm; And / or, the thickness H2 of the first adhesive layer satisfies: 10μm < H2 ≤ 20μm.

10. The battery according to claim 5, characterized in that, It also includes a first adhesive tape, which is attached to the positive electrode tab and the surface of the second adhesive layer. The thickness of the first adhesive tape is H4, and the relationship between H1 and H4 satisfies 0.25≤H1 / H4≤8, where H4 is 10μm~20μm. Preferably, 0.5 ≤ H1 / H4 ≤ 2.

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