Battery

Abstract

The invention relates to the technical field of batteries, and discloses a battery which comprises a shell and a battery cell, the battery cell is arranged in the shell and comprises a first pole piece, a diaphragm and a second pole piece, and the first pole piece comprises a first current collector and first active material layers arranged on the surfaces of the two sides of the first current collector in the first direction of the first pole piece; wherein the first active material layer on each side is provided with a first groove extending in the second direction, and the first grooves on the two sides are arranged in a staggered mode in the third direction; in the third direction, the dislocation distance of the two adjacent first grooves in the surfaces of the two sides of the first current collector in the third direction is H1, the thickness of the first current collector is D, and H1 is larger than or equal to 2D; the elongation at break of the first current collector in the third direction is a1, the elongation at break of the first current collector in the second direction is a2, and a1 / a2 is larger than or equal to 0.6 and smaller than or equal to 1.6. According to the invention, the risk of pole piece breakage in the battery cycle process can be reduced, the infiltration effect can be improved, and the battery cycle performance is improved.

Description

Technical Field

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

[0002] Batteries are widely used in various devices, such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools.

[0003] With the rapid development of battery technology, higher requirements are being placed on the cycle performance and safety of batteries. Summary of the Invention

[0004] In view of this, the present invention provides a battery to solve the problems of poor cycle performance and poor safety of batteries.

[0005] In a first aspect, the present invention provides a battery, comprising: a casing; and a battery cell disposed within the casing, the battery cell comprising a first electrode, a separator, and a second electrode, the first electrode comprising a first current collector and a first active material layer disposed on both sides of the first current collector along a first direction of the first electrode; wherein, each side of the first active material layer is provided with a first groove extending along a second direction, the first grooves on both sides are staggered along a third direction, and along the third direction, the stagger distance between two adjacent first grooves on both sides of the first current collector along the third direction is H1, the thickness of the first current collector is D, satisfying that H1≥2D; the elongation at break of the first current collector along the third direction is a1, and the elongation at break of the first current collector along the second direction is a2, satisfying that 0.6≤a1 / a2≤1.6.

[0006] In some embodiments, 0.8 ≤ a1 / a2 ≤ 1.3; and / or, H1 satisfies 7 μm ≤ H1 ≤ 2500 μm.

[0007] In some embodiments, each side has a plurality of first trenches, and the plurality of first trenches are distributed at intervals along the third direction. The misalignment distance between two adjacent first trenches on the same side surface along the first direction of the first electrode is H2, which satisfies 400μm≤H2≤3500μm, preferably 500μm≤H2≤1500μm.

[0008] In some embodiments, the first groove on each side has a top groove opening away from the first current collector and a bottom groove opening close to the first current collector along the first direction; along the third direction, the width H3 of the top groove opening is greater than the width H4 of the bottom groove opening, and satisfies 50μm≤H3≤150μm, 20μm≤H4≤150μm, and 1μm≤H3-H4≤30μm.

[0009] In some embodiments, the depth of the first groove on each side along the first direction is H5, satisfying 10μm≤H5≤50μm, preferably 15μm≤H5≤30μm.

[0010] In some embodiments, in the first trenches on both sides of the first electrode, the outer first trench has a larger dimension along the third direction than the inner first trench; and / or, the outer first trench has a larger dimension along the first direction than the inner first trench; wherein the outer first trench is closer to the outer shell than the inner first trench.

[0011] In some embodiments, the cell is a wound core. Along the winding direction of the wound core, the first electrode has a starting segment near the winding center, a ending segment away from the winding center, and an intermediate segment located between the starting segment and the ending segment. Along the winding direction of the wound core, the starting segment, the intermediate segment, and the ending segment are connected sequentially. The first groove located in the starting segment has a dimension W1 along the third direction, and the first groove located in the ending segment has a dimension W2 along the third direction, satisfying that 90μm≤W1≤130μm, 60μm≤W2≤100μm, and W1-W2≥20μm.

[0012] In some embodiments, along the first direction, the second electrode has a first protrusion on one side surface near the housing, and a first recess on the other side surface of the second electrode corresponding to the first protrusion. On the same projection plane perpendicular to the first direction, the sum of the orthographic projection areas of the first protrusion along the first direction is a7, and the sum of the orthographic projection areas of the first groove on one side surface of the first current collector along the first direction is a8, satisfying 1.5≤a7 / a8≤12.

[0013] In some embodiments, the first electrode is a negative electrode and the second electrode is a positive electrode; the positive electrode includes a cobalt-containing material, which includes at least one of lithium cobalt oxide, nickel-cobalt-manganese ternary material, and nickel-cobalt-aluminum ternary material.

[0014] In some embodiments, the first electrode is a negative electrode and the second electrode is a positive electrode. The negative electrode comprises a silicon-based material, and the particle sizes Dv10, Dv90, and Dv50 of the silicon-based material satisfy the ratio (Dv90-Dv10) / Dv50 as A, where 0.2≤A≤0.5; and / or, the first trench on the surface of the negative electrode near the outer casing has a top groove away from the first current collector along the first direction and a bottom groove near the first current collector. The width H3 of the top groove is greater than the width H4 of the bottom groove, and the widths H3 and H4 of the top groove satisfy 0.01≤A / (H3-H4)≤0.5.

[0015] Beneficial effects: If the misalignment distance H1 between two adjacent first trenches along the third direction is too small, resulting in excessive overlap, the strength of the first electrode at the first trench will be weak. During battery fabrication or cycling, the first electrode will be subjected to bending stress, tensile stress, and expansion and contraction stress. When these stresses concentrate at the first trench location, cracks are easily generated at that location, increasing the frequency of crack propagation and band breakage during battery cycling. On the other hand, when the first electrode has a first trench, more electrolyte is stored at the first trench location, and the active layer material is reduced, resulting in less resistance to lithium-ion insertion and extraction. Therefore, the current is larger and more concentrated at the first trench location, leading to uneven current distribution, causing localized overheating and reduced cycle performance. By ensuring H1 ≥ 2D, the misalignment distance between the two adjacent first trenches along the third direction is larger, which reduces stress concentration at the first trench location, lowers the risk of crack propagation and band breakage during battery cycling, and also makes the current distribution more uniform, improving cycle performance. Furthermore, by using 0.6≤a1 / a2≤1.6, the difference in fracture elongation of the first electrode in the two directions is minimized. This prevents excessive differences in the mechanical properties of the first electrode in the two directions, which could lead to cracks in the relatively weak first trench area of ​​the first electrode easily forming in one direction when subjected to stress. This reduces the risk of cracks and breakage of the first electrode during processing and battery cycling, further improving battery cycle performance and safety. It also allows the first trench to store electrolyte, improving the wetting effect and the flow path of lithium ions, thereby enhancing battery cycle performance. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the battery structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the battery cell structure according to an embodiment of the present invention; Figure 3 for Figure 2 Section AA along the middle; Figure 4 for Figure 2 A partially enlarged schematic diagram of the first electrode plate; Figure 5 This is a cross-sectional view of a battery cell according to another embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of the first electrode sheet in its unfolded state according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the structure of one side surface of the first electrode sheet in an embodiment of the present invention; Figure 8 For this Figure 7 Cross-sectional view of FF.

[0018] Explanation of reference numerals in the attached figures: 1-Outer casing; 2-Battery cell; 3-First electrode; 31-First current collector; 32-First active material layer; 321-First trench; 301-Starting section; 302-Ending section; 303-Intermediate section; 4-Separator; 5-Second electrode; 5a-First protrusion; 5b-First concave portion; 51-Positive current collector; 52-Positive active material layer; X-Second direction; Y-Third direction; Z-First direction. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] With the rapid development of battery technology, higher requirements are being placed on the cycle performance and safety of batteries. Grooves are machined on the surface of the active material layer of the electrode. These grooves can store more electrolyte, improving the wetting effect of the electrode and the flow path of lithium ions, thereby enhancing the battery's cycle performance. However, batteries composed of grooved electrodes are more prone to localized cracking and even electrode breakage during cycling, especially when grooves are machined on both sides of the active material layer along the thickness direction of the electrode. The frequency of crack propagation and electrode breakage is significantly higher after battery cycling.

[0021] Research has found that the main cause of electrode breakage is that the two grooves on the active material layers on both sides of the electrode along its thickness direction overlap too much (or even align), and the current collector of the electrode has too large a difference in elongation at break in different directions.

[0022] During the coating, drying, and rolling processes of the electrode sheets, residual stress and tensile stress of varying degrees are introduced in both the MD (length) and TD (width) directions. In the other direction, the electrode sheets are bent into corresponding shapes under the traction of the winding needles during battery winding. If the difference in elongation at break between the MD and TD directions is too large, it can easily lead to uneven plastic deformation of the electrode sheets during rolling and / or winding, resulting in significant differences in the mechanical properties of the electrode sheets in the MD and TD directions. Therefore, when grooves are set on the active material layer during the electrode sheet's transport process, uneven deformation in both directions is more likely to occur, leading to microcracks inside the electrode sheets. These microcracks can cause localized crack propagation during subsequent battery cycles, even leading to electrode breakage and resulting in low battery capacity and poor cycle performance. This is especially true when both sides of the electrode sheet have grooves and the groove positions overlap, making the strength at the corresponding groove positions weaker and increasing the frequency of electrode breakage.

[0023] In response, this application addresses this issue by misaligning the grooves on the active material layers on both sides of the electrode along its thickness direction and controlling the difference in elongation at break between the current collectors in the two directions within a certain range. This reduces the risk of electrode breakage during processing and battery cycling, thereby improving the battery's cycle performance and safety.

[0024] Below, refer to Figures 1 to 8 The embodiments of the present invention will be described below.

[0025] This invention provides a battery, including a casing 1 and a battery cell 2. The battery cell 2 is disposed inside the casing 1 and includes a first electrode 3, a separator 4, and a second electrode 5. The first electrode 3 includes a first current collector 31 and a first active material layer 32 disposed on both sides of the first current collector 31 along a first direction Z. Each side of the first active material layer 32 has a first groove 321 extending along a second direction X, and the first grooves 321 on both sides are staggered along a third direction Y. Along the third direction Y, the stagger distance between two adjacent first grooves 321 on both sides of the first electrode 3 is H1, and the thickness of the first current collector 31 is D, satisfying that H1 ≥ 2D. The elongation at break of the first current collector 31 along the third direction Y is a1, and the elongation at break of the first current collector 31 along the second direction X is a2, satisfying that 0.6 ≤ a1 / a2 ≤ 1.6. a1 / a2 can be any one of 0.6, 0.7, 0.8, 1, 1.3, 1.4, 1.5, 1.6 or any value between two of them.

[0026] In this embodiment of the invention, the first direction Z can be the thickness direction of the first electrode 3. The second direction X can be the length direction of the first electrode 3, and the third direction Y can be the width direction of the first electrode 3; or, the second direction X can be the width direction of the first electrode 3, and the third direction Y can be the length direction of the first electrode 3. In the following description, the second direction X is taken as the length direction of the first electrode 3, and the third direction Y is taken as the width direction of the first electrode 3, as an example.

[0027] The battery cell 2 can be a wound core or a stacked core. One of the first electrode 3 and the second electrode 5 is the positive electrode, and the other is the negative electrode. The battery cell 2 includes a first electrode 3, a separator 4, and a second electrode 5 stacked together.

[0028] The first grooves 321 on both sides of the first electrode 3 can be completely misaligned along the third direction Y. Figure 4 As shown); it can also be partially misaligned (as shown). Figure 5 As shown in the diagram, the first grooves 321 on both sides of the first electrode 3 are not completely aligned. Complete misalignment of the first grooves 321 on both sides, compared to partial misalignment, can further improve the strength of the first electrode 3, but it presents challenges in the manufacturing process, including complex positioning, high processing precision, and slow efficiency. Partial misalignment of the first grooves 321 on both sides forms an interlaced support structure for the first electrode 3. This interlaced support structure effectively disperses the expansion and contraction stresses during battery cycling, thereby significantly improving the bending strength and toughness of the first electrode 3 and further reducing the risk of crack propagation and breakage during battery cycling. Furthermore, partial misalignment of the first grooves 321 on both sides has lower processing requirements and is relatively easy to achieve.

[0029] Reference Figure 3 , Figure 4 and Figure 5When the first electrode 3 has multiple first grooves 321 on both sides along the thickness direction, the misalignment distance between two adjacent first grooves 321 on both sides of the first electrode 3 along the third direction Y refers to the distance between the two centers of the two first grooves 321 that are closest to each other along the third direction Y.

[0030] Test method for elongation at break: Disassemble the battery and remove the active material layer (first active material layer 32) to obtain the current collector (first current collector 31). The method for removing the first active material layer 32 from the first electrode can be to immerse the obtained first electrode in an aqueous solution (or N-methylpyrrolidone solution), and then use an ultrasonic machine to ultrasonically vibrate the first electrode immersed in the solution until the first active material layer 32 on the first current collector 31 is completely detached, thus obtaining the first current collector 31; the long side is taken as the direction of the current collector's length (e.g., the second direction X). Using the width direction (e.g., the third direction Y) as the short side, take a current collector strip with a size of 200mm × 24mm and mark it as A1. Using the length direction of the electrode (first electrode 3) as the short side and the width direction as the long side, take a current collector strip with a size of 200mm × 24mm and mark it as A2. Use a tensile testing machine to test the elongation at break of A1 and A2 respectively. During the test, the tensile speed of the tensile testing machine is set to 50mm / s, the length of the electrode is set to 200mm, and the width is set to 24mm. Record the test results of the tensile testing machine when the electrode breaks.

[0031] If the misalignment distance H1 between two adjacent first trenches 321 along the third direction Y is too small, they will almost overlap. This will result in the first electrode 3 being weak in the first trench 321. When subjected to bending or tensile stress, the stress will be highly concentrated at the first trench 321, which will easily cause cracks to form in the first electrode 3 at this location. This will not effectively improve the problem of crack propagation and breakage of the first electrode 3 during battery cycling. On the other hand, the current distribution is concentrated in the first trench 321, resulting in uneven current distribution, causing local overheating of the battery, and reducing cycle performance. By making H1≥2D, the misalignment distance between the two adjacent first trenches 321 along the third direction Y is larger, which can reduce the stress concentration of the electrode at the first trench 321, reduce the risk of crack propagation and breakage of the first electrode 3 during battery cycling, and also make the current distribution more uniform, thus improving cycle performance. Furthermore, by using 0.6≤a1 / a2≤1.6, the difference in fracture elongation of the first electrode 3 in the two directions is small, which can further reduce the risk of cracks and breakage of the first electrode 3 during processing and battery cycling, thereby improving safety. It can also store electrolyte through the first trench 321, improve the wetting effect, improve the flow path of lithium ions, and thus improve the battery cycle performance.

[0032] In some embodiments, 0.8 ≤ a1 / a2 ≤ 1.3. a1 / a2 can be any one of 0.8, 0.9, 1, 1.2, 1.3 or any combination thereof. This design further reduces the difference in fracture elongation of the first electrode 3 in the two directions, further reducing the risk of cracks and breakage of the first electrode 3 during processing and battery cycling.

[0033] In some embodiments, H1 satisfies 7μm≤H1≤2500μm. H1 can be any one of 7μm, 20μm, 50μm, 100μm, 250μm, 300μm, 400μm, 500μm, 600μm, 750μm, 800μm, 900μm, 1000μm, 1500μm, 2000μm, 2500μm, or a value between any two of them.

[0034] If the misalignment distance H1 between two adjacent first trenches 321 along the third direction Y is too small (less than 7 μm), they will almost overlap, resulting in the first electrode 3 being thinner at the location of the first trench 321. Under bending or tensile stress, the stress will be highly concentrated at the location of the first trench 321, making it very easy for cracks to form in the first electrode 3 at this location. During battery cycling, the frequency of crack propagation and band breakage of the first electrode 3 will be higher. On the other hand, it will cause the current distribution to be concentrated in the first trench 321, resulting in uneven current distribution and causing side reactions such as local overheating of the battery, thus reducing cycle performance. If H1 is too large (greater than 2500 μm), the total area of ​​the first trench 321 on each side of the first electrode 3 will be small, resulting in low electrolyte storage and poor wetting effect. Therefore, 7 μm ≤ H1 ≤ 2500 μm can reduce the risk of crack propagation and band breakage of the first electrode 3 during battery cycling and improve the wetting effect.

[0035] In some embodiments, a plurality of first trenches 321 are provided on each side, and the plurality of first trenches 321 are distributed at intervals along the third direction Y. The interval between two adjacent first trenches 321 on the same side surface along the first direction Z of the first electrode is H2. Figure 4 As shown), satisfying 400μm≤H2≤3500μm. Preferably, 500μm≤H2≤1500μm. H2 can be any one of 400μm, 500μm, 700μm, 1000μm, 1200μm, 1400μm, 1500μm, 2000μm, 3500μm, or a value between any two of them.

[0036] If H2 is too small (less than 400 μm), the spacing between two adjacent first trenches 321 on the same side is too close, resulting in a large area occupied by the first trenches 321. This leads to insufficient strength of the first electrode 3, increasing the risk of crack propagation and breakage during battery cycling, and posing a risk of low capacity. Furthermore, when the spacing between two adjacent first trenches 321 on the same side is too close, the risk of material shedding from the area where the first trenches are located is greater during battery cycling due to expansion and contraction, thus reducing battery cycle life. If H2 is too large (greater than 3500 μm), the total area of ​​the first trenches 321 is small, resulting in low electrolyte storage and poor wetting effect, with little improvement on battery cycle performance. Therefore, 400 μm ≤ H2 ≤ 3500 μm can ensure the strength of the first electrode 3, reduce the risk of crack propagation and breakage during battery cycling, and improve the wetting effect.

[0037] In some embodiments, refer to Figure 5 Each side of the first groove 321 has a top groove opening away from the first current collector 31 along the first direction Z and a bottom groove opening close to the first current collector 31. Along the third direction Y, the width H3 of the top groove opening is greater than the width H4 of the bottom groove opening, and satisfies the following conditions: 50μm≤H3≤150μm, 20μm≤H4≤150μm, and 1μm≤H3-H4≤30μm. H3 can be any one of 50μm, 70μm, 80μm, 90μm, 100μm, 120μm, 150μm, or any value between any two. H4 can be any one of 20μm, 40μm, 60μm, 80μm, 100μm, 120μm, 150μm, or any value between any two. H3-H4 can be any one of 1μm, 5μm, 15μm, 20μm, 25μm, 30μm, or any value between any two.

[0038] The H3 and H4 test methods for the first trench are as follows: After discharging the battery to 0% SOC, disassemble the battery to obtain the electrode sheet (e.g., the negative electrode sheet). Cut the negative electrode sheet along a cross-section parallel to the depth direction (Z direction) and perpendicular to the length direction (X direction) of the first trench to obtain the cross-section (e.g., ...). Figure 5 As shown), using a scanning electron microscope magnified to 500x, along the depth direction (Z direction) of the first trench, towards the surface of the negative electrode current collector, take multiple straight lines connecting the left and right side walls of the width direction (Y direction) of the first trench and parallel to the surface of the negative electrode current collector. Among the multiple straight lines, the longest straight line is the one closest to the negative electrode active material layer and furthest from the surface of the negative electrode current collector. The length of this longest straight line is H3. Among the multiple straight lines, the shortest straight line is the one closest to the negative electrode current collector and overlaps with the bottom surface of the trench. The length of this shortest overlapping straight line is H4.

[0039] It should be noted that if the bottom surface of the first trench is an uneven surface, then among the multiple straight lines, there is the shortest straight line that is closest to the negative electrode current collector and passes through the lowest point of the bottom surface of the trench. The length of this shortest straight line is H4.

[0040] The width H3 of the top opening of the first trench 321 is greater than the width H4 of the bottom opening, making the trench wall of the first trench 321 inclined. This not only increases the electrolyte storage capacity but also facilitates the electrolyte's penetration into the interior of the first trench 321 and its diffusion into the surrounding areas without trenches, improving the wetting effect and thus enhancing the battery's cycle performance. Furthermore, the inclined surface of the first trench 321 means that during battery cycling, when expansion occurs, the inclined surface of the trench wall generates an inward component force, which helps to offset some of the expansion stress. The outward tension maintains the overall stability of the trench and prevents the structure of the first trench from collapsing. When the wall surface of the first trench 321 is inclined, compared with a straight surface, it can increase the contact area between the active material and lithium ions, improve the ability of lithium ions to be inserted and extracted in the negative electrode active material layer, and further improve the cycle performance of the battery. Moreover, the width H3 of the top opening of the first trench 321 is greater than the width H4 of the bottom opening, which is also conducive to the dissipation of heat inside the battery to the outside through the wider top opening, improving the heat dissipation capacity, and thus improving the charging and discharging performance of the battery.

[0041] If the difference between the width H3 of the top opening and the width H4 of the bottom opening of the first trench 321 is too large, exceeding 30 μm, the structure of the first trench 321 will be less stable, the active material at the edge of the top opening will be more prone to detachment, and it will not be conducive to improving the stability of the electrolyte storage in the first trench. During expansion, the electrolyte in the trench may be squeezed out. If the difference between the width of the top opening and the width of the bottom opening of the first trench 321 is too small, less than 1 μm, then more advanced materials will be needed when removing the active layer that is close to the bottom of the current collector. High laser energy or increased pressure on the bottom active layer by the mechanical roller can more easily cause irreversible damage to the current collector structure. Moreover, if the difference between the top and bottom groove widths of the first groove 321 is too small, it will be difficult to remove active material debris generated during the groove setting process, which will result in an excessive voltage drop in the battery. Therefore, 1μm≤H3-H4≤30μm can not only increase the electrolyte storage capacity, improve electrolyte storage stability, and enhance battery cycle performance, but also prevent damage to the current collector and improve safety.

[0042] In some embodiments, the depth of the first groove 321 on each side along the first direction Z is H5, satisfying 10μm≤H5≤50μm, preferably 15μm≤H5≤30μm. H5 can be any one of 10μm, 15μm, 20μm, 30μm, 40μm, 50μm, or any value between two of them.

[0043] If H5 is too small, less than 10μm, it is not conducive to the electrolyte penetrating into the first trench 321 and spreading to the surrounding areas where no trench is set, resulting in poor wetting effect. If H5 is too large, greater than 50μm, it is easy to reduce the number of lithium ion-accommodating points at the bottom of the trench, thereby causing lithium ion deposition. It can also lead to excessive material removal, reducing capacity. Furthermore, removing too much active material can easily damage the current collector structure. Therefore, 10μm≤H5≤50μm can improve the wetting effect, improve the cycle performance of the battery, and also improve safety.

[0044] It should be noted that when setting the first groove on the first electrode, if the first groove is set by laser grooving, the difference between the width H3 of the top groove and the width H4 of the bottom groove 321 can be achieved by adjusting parameters such as the energy, frequency, and focused spot diameter of the laser during the groove setting process. If the first groove is set by mechanical roller grooving, the difference between the width H3 of the top groove and the width H4 of the bottom groove 321 can be achieved by adjusting the mechanical rollers of different sizes or by adjusting the distance between the mechanical rollers and the first electrode during the groove setting process. The specific implementation method is not limited, as long as the corresponding structural changes can be achieved.

[0045] In some embodiments, among the first trenches 321 on both sides of the first electrode 3, the outer first trench 321 has a larger dimension along the third direction Y than the inner first trench 321. And / or, the outer first trench 321 has a larger dimension along the first direction Z than the inner first trench 321. The outer first trench 321 is closer to the outer casing 1 than the inner first trench 321.

[0046] This helps to quickly conduct heat from inside the battery to the outside near the outer casing 1, reducing the temperature rise during battery cycling, improving the problem of increased side reactions between active materials and electrolyte when the battery temperature is too high, and enhancing the battery's cycle performance.

[0047] In some embodiments, reference is made together with Figure 2 and Figure 6 , Figure 6This is a schematic diagram of the first electrode 3 in its unfolded state. The battery cell 2 is a wound core. Along the winding direction of the wound core, the first electrode 3 has a starting segment 301 near the winding center O, a ending segment 302 away from the winding center O, and an intermediate segment 303 located between the starting segment 301 and the ending segment 302. Along the winding direction of the wound core, the starting segment 301, intermediate segment 303, and ending segment 302 are connected sequentially. The first groove 321 located in the starting segment 301 has a dimension W1 along the third direction Y, and the first groove 321 located in the ending segment 302 has a dimension W2 along the third direction Y, satisfying 90μm≤W1≤130μm, 60μm≤W2≤100μm, and W1-W2≥20μm. W1 can be any one of 90μm, 100μm, 110μm, 120μm, and 130μm, or a value between any two. W2 can be any value among 60μm, 70μm, 80μm, 90μm, and 100μm, or any value between two of them.

[0048] During battery cycling, the starting segment 301, which is closer to the winding center O, accumulates heat more easily than the ending segment 302, which is farther away from the winding center O. In some embodiments, the size of the first trench 321 located in the starting segment 301 along the third direction Y is W1, which is larger than the size of the first trench 321 located in the ending segment 302 along the third direction Y, and the difference between the two is greater than or equal to 20μm. This makes the size of the first trench 321 closer to the winding center O larger, which is beneficial for quickly dissipating the heat accumulated inside the winding center O through the larger first trench 321 to the outside, reducing the temperature rise during battery cycling and improving the battery's cycle performance.

[0049] In some embodiments, refer to Figure 7 and Figure 8 Along the first direction Z, the second electrode 5 has a first protrusion 5a on the side surface near the outer shell 1, and a first recess 5b corresponding to the first protrusion on the other side surface of the second electrode 5. On the same projection plane perpendicular to the first direction Z, the sum of the orthogonal projection areas of the first protrusion 5a along the first direction Z is a7, and the sum of the orthogonal projection areas of the first groove 321 on one side surface of the first current collector 31 along the first direction Z is a8, satisfying 1.5 ≤ a7 / a8 ≤ 12. a7 / a8 can be any value or a combination of 1.5, 2, 3.5, 5.5, 6, 7, 8.5, 9, 10, 11, and 12. The second electrode 5 can be a positive electrode, and the first electrode 3 can be a negative electrode.

[0050] The negative electrode sheet contains silicon-based materials. Silicon-based materials expand significantly during cycling. The first trench on the negative electrode sheet can alleviate this expansion. However, the expansion stress on the negative electrode sheet acts on the adjacent positive electrode sheet, easily leading to deformation, powder shedding, and breakage. A first recess 5b and a corresponding first protrusion 5a are provided on the positive electrode sheet. The first recess 5b can store electrolyte, improving cycle performance, and the presence of the first protrusion 5a can alleviate the compression of the positive electrode sheet by the expansion of the negative electrode during battery cycling, releasing electrolyte. Interlayer stress is a concern, but excessive first protrusion 5a can reduce the strength of the positive electrode and cause point contact with the negative electrode during expansion. If the contact area between the first protrusion 5a and the first trench on the negative electrode is too large, it can easily lead to breakage in the area where the trench on the negative electrode is located. Therefore, it is necessary to control the ratio of the area of ​​the first protrusion 5a on the positive electrode to the area of ​​the first trench on the negative electrode within a suitable range. This can reduce the risk of breakage of the positive and negative electrodes, improve the battery's liquid storage capacity, and enhance the battery's cycle performance and safety. When a7 / a8 is greater than 12, a7 is too large, resulting in a large contact area between the first protrusion 5a and the negative electrode. When the cell expands, the pressure exerted by the first protrusion 5a on the positive electrode on the first groove on the negative electrode is greater, which can easily cause the positive or negative electrode to break during cycling. When a7 / a8 is less than 1.5, a7 is too small, which cannot fully utilize the functions of the first concave portion 5b in storing electrolyte and the first protrusion 5a in mitigating expansion. Therefore, 1.5≤a7 / a8≤12 can fully utilize the functions of storing electrolyte and mitigating expansion, and can also reduce the risk of breakage of the positive or negative electrode during cycling.

[0051] a7 / a8 Measurement Method: After discharging the battery to 0% SOC, disassemble the battery to obtain positive and negative electrode plates. In the thickness direction of the cell layer, cut 2cm long and 2cm wide positive and negative electrode plate samples from adjacent positive and negative electrode plates near the middle along the length and width directions, respectively. The cut positive electrode plate sample has multiple first protrusions 5a, and the cut negative electrode plate sample has multiple first grooves 321. Use a 3D profilometer to obtain a first image of the positive electrode plate sample and a second image of the negative electrode plate sample, respectively. Obtain the sum of the projected areas of the multiple first protrusions 5a in the first image and the sum of the projected areas of the multiple first grooves 321 in the second image. The ratio of the sum of the two projected areas is a7 / a8.

[0052] In some embodiments, the first electrode 3 is a negative electrode, and the second electrode 5 is a positive electrode. The positive electrode includes a positive current collector 51 and positive active material layers 52 disposed on both sides of the positive current collector. The positive electrode includes a cobalt-containing material, which includes at least one of lithium cobalt oxide, nickel-cobalt-manganese ternary materials, and nickel-cobalt-aluminum ternary materials. The nickel-cobalt-manganese and nickel-cobalt-aluminum ternary materials respectively include single-crystal materials and / or polycrystalline materials. The DV50 particle size range A3 of the single-crystal material satisfies 1μm≤A3≤5μm, and the DV50 particle size range A4 of the polycrystalline material satisfies 5μm≤A4≤20μm. The DV50 particle size range of lithium cobalt oxide is 5μm~25μm.

[0053] The negative electrode sheet comprises silicon-based materials. The particle sizes of the silicon-based materials, Dv10, Dv90, and Dv50, satisfy the condition (Dv90-Dv10) / Dv50, where A is 0.2≤A≤0.5. A can be any one of 0.2, 0.3, 0.35, 0.04, or 0.5, or any combination thereof.

[0054] Narrower particle sizes and higher uniformity in silicon-based materials improve lithium-ion transport efficiency within the negative electrode and reduce volume changes. When A > 0.5, the particle size distribution is wide, resulting in a mixture of large and small particles. This leads to significant differences in expansion and contraction during battery cycling, intense mutual compression between silicon particles, and rapid shedding and breakage, failing to effectively improve cycle performance. When A < 0.2, although the silicon-carbon particle size concentration is high, multiple collisions during silicon-carbon material preparation can easily cause particle breakage, exposing internal silicon, increasing internal defects, reducing lithium insertion / extraction efficiency, and lowering battery cycle performance. Therefore, a value of 0.2 ≤ A ≤ 0.5 is necessary to improve battery cycle performance while effectively suppressing expansion during cycling.

[0055] The particle sizes Dv10, Dv90, and Dv50 of silicon-carbon composite particles can be measured using a laser particle size analyzer.

[0056] In some embodiments, the first groove 321 on the side surface of the negative electrode near the outer casing 1 has a top groove that is away from the first current collector 31 along the first direction Z and a bottom groove that is close to the first current collector 31. The width H3 of the top groove is greater than the width H4 of the bottom groove. The widths H3 of the top groove and H4 of the bottom groove satisfy 0.01≤A / (H3-H4)≤0.5.

[0057] A larger A value indicates a more uneven particle size distribution of the silicon-based material and greater differences in particle volume change. Therefore, it is necessary to differentiate the top and bottom openings of the first trench 321 to better disperse the volume change of the silicon-based material. On the other hand, the more uneven the particle size distribution of the silicon-based material, the worse the structural stability of the material. During the battery charging and discharging reaction, the possibility of silicon-based material cracking increases, and the SEI film generated by its interaction with the electrolyte is less stable, making it easier for the silicon-based material to undergo side reactions with the electrolyte, repeatedly generating SEI film, increasing heat generation, and reducing the cycle performance of the battery. Therefore, a larger H3-H4 value is needed to more easily guide the generated heat to the casing and the outside environment for heat exchange. Conversely, a smaller A value indicates a more uniform volume change of the silicon-based material during the battery charging and discharging reaction, better structural stability of the material, and a more stable SEI film generated by the reaction of the silicon-based material with the electrolyte, resulting in less heat generation. Therefore, it is not necessary to set a large difference in the H3-H4 value of the trench to meet the battery heat dissipation requirements. In fact, setting a large difference in the H3-H4 value would reduce the battery energy density.

[0058] Example 1: Battery preparation: I. Preparation of the positive electrode sheet Lithium cobalt oxide (LCO), polyvinylidene fluoride (PVDF), and conductive carbon (SuperP) are dissolved in N-methylpyrrolidone (NMP) at a mass ratio of 98:1:1 and stirred evenly to form a positive electrode slurry. This slurry is then uniformly coated onto both sides of the positive electrode current collector along its thickness direction to form a positive electrode sheet. A specific roller is used to process a structure on the positive electrode sheet where one surface has a first convex portion and the other surface has a corresponding first concave portion.

[0059] II. Preparation of the negative electrode sheet Silicon-carbon composite material, graphite, conductive carbon black, polyacrylic acid, sodium carboxymethyl cellulose, and styrene-butadiene rubber were mixed in a mass ratio of 43.5:53.5:0.5:1.2:0.4:0.9. This mixture was then added to deionized water and stirred until homogeneous to form a negative electrode slurry. This slurry was then uniformly coated onto both sides of a 5μm thick copper foil current collector, forming a negative electrode active material layer. After drying and rolling, the slurry was formed into a negative electrode sheet. Two first grooves 321, staggered along the width direction, were machined on the negative electrode active material layer on both sides of the current collector using a mechanical roller. The misalignment distance H1 of two adjacent first grooves 321 on both sides of the negative electrode current collector was measured along the width direction. The top groove width H3 and the bottom groove width H4 of the first groove 321 were measured. The elongation at break a2 along the length direction and the elongation at break a1 along the width direction of the current collector of the negative electrode sheet were measured using a universal tensile testing machine. The particle sizes Dv10, Dv90, and Dv50 of silicon-based materials were measured using a laser particle size analyzer, and then the ratio A of (Dv90-Dv10) / Dv50 among the three was calculated.

[0060] III. Preparation of Electrolyte The lithium salt was 1M lithium hexafluorophosphate (LiPF6), the solvents were ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a mass ratio of 1:1:1, the non-aqueous organic solvents were a mixture of carboxylic acid ester solvents (a 2:1 mixture of ethyl propionate (EP) and propyl propionate (PP)) and fluoroethylene carbonate (8%), which were counted by the total amount of electrolyte.

[0061] IV. Battery Assembly The negative electrode, the first separator, the positive electrode, and the second separator are stacked in sequence and wound to form a battery cell. The battery cell is then encapsulated with a casing, followed by processes such as electrolyte injection, secondary sealing, formation, and sorting to obtain the battery. The battery preparation methods in Examples 2-19 are the same as those in Example 1 and will not be detailed here. Some parameter changes are shown in Table 1 below.

[0062] Table 1: Effects of different parameters on battery yield and capacity retention of the embodiments and comparative examples of the present invention.

[0063] Test method for pass rate of 800T cycle battery: In each of the above embodiments and comparative examples, there are 10 batteries in each group. After disassembling 10 batteries that have undergone 800T cycles, if one battery has a crack or break in the electrode, it is recorded as 1 / 10. If no crack or break is found in any of the 10 batteries, it is recorded as 0 / 10.

[0064] 800T Cycling Capacity Retention Rate Test Method: The lithium-ion batteries prepared in the above examples and comparative examples were placed in an environment of 25±2℃ and charged at a constant current of 1C until the cutoff current was 0.05C. After the batteries were fully charged, they were left to rest for 5 minutes, and then discharged at a constant current of 0.5C until the cutoff voltage was 3.0V. The charging and discharging mechanism was repeated three times, and the highest discharge capacity in the first three cycles was recorded as the initial capacity Q0. After 800 cycles, the discharge capacity Q1 of the battery was recorded. The high-temperature capacity retention rate of the battery is Q1 / Q0×100%. As shown in Table 1, in Examples 1-19, when H1≥2D and 0.6≤a1 / a2≤1.6, the battery pass rate and battery capacity retention rate are both greater than those in Comparative Examples 1 and 2 when a1 / a2 is not in the range of 0.6~1.6. This indicates that when the battery in the embodiments of the present invention satisfies H1≥2D and 0.6≤a1 / a2≤1.6, it can effectively reduce the risk of electrode breakage during battery cycling and improve battery cycle performance.

[0065] In Examples 1-15 and Examples 17-19, when 7μm≤H1≤2500μm, the battery pass rate is greater than that in Comparative Example 3 when H1 is not in the range of 7μm~2500μm (H1=6μm). This shows that when the battery of the present invention meets the requirement of 7μm≤H1≤2500μm, it can effectively reduce the risk of electrode breakage during battery cycling.

[0066] In Examples 1-19, when a7 / a8 is greater than 12 in Example 18, the contact area between the first protrusion 5a and the negative electrode is larger, resulting in a lower battery qualification rate than in other examples where 1.5≤a7 / a8≤12. This indicates that the battery of the present invention can effectively reduce the risk of breakage of the positive or negative electrode during cycling when 1.5≤a7 / a8≤12.

[0067] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this application, are intended to cover non-exclusive inclusion. In the description of embodiments of this application, technical terms such as "first," "second," etc., are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary or secondary relationship of the indicated technical features. In the description of embodiments of this application, "a plurality of" means two or more, unless otherwise expressly and specifically defined. The reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0068] In the description of the embodiments of this application, the technical terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "circumferential," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed, operated, or used in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0069] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" 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 or an electrical connection; 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. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0070] Although embodiments of the 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 invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A battery, characterized by, The battery comprises: a shell (1); an electric core (2) arranged in the shell (1), the electric core (2) comprising a first pole piece (3), a diaphragm (4) and a second pole piece (5), the first pole piece (3) comprising a first current collector (31) and a first active material layer (32) arranged on both sides of the first current collector (31) along a first direction (Z) of the first pole piece (3); wherein the first active material layer (32) on each side is provided with a first groove (321) extending along a second direction (X), and the first grooves (321) on both sides are arranged in a staggered manner along a third direction (Y), along the third direction (Y), the staggered distance of two first grooves (321) adjacent to each other on both sides of the first pole piece (3) along the third direction (Y) is H1, the thickness of the first current collector (31) is D, and H1≥2D is satisfied; the breaking elongation rate of the first current collector (31) along the third direction (Y) is a1, and the breaking elongation rate of the first current collector (31) along the second direction (X) is a2, and 0.6≤a1 / a2≤1.6 is satisfied.

2. The battery according to claim 1, wherein 0.8≤a1 / a2≤1.3; and / or, H1 satisfies 7μm≤H1≤2500μm.

3. The battery according to claim 1, wherein a plurality of the first grooves (321) are arranged on each side, and the plurality of first grooves (321) are distributed at intervals along the third direction (Y), the interval distance between two first grooves (321) on the same side surface of the first pole piece (3) along the first direction (Z) is H2, and 400μm≤H2≤3500μm, preferably 500μm≤H2≤1500μm, is satisfied.

4. The battery according to claim 1, wherein the first groove (321) on each side has a top notch away from the first current collector (31) along the first direction (Z) and a bottom notch close to the first current collector (31); along the third direction (Y), the width H3 of the top notch is greater than the width H4 of the bottom notch, and 50μm≤H3≤150μm, 20μm≤H4≤150μm, 1μm≤H3-H4≤30μm is satisfied.

5. The battery according to claim 1, wherein the depth of the first groove (321) on each side along the first direction (Z) is H5, and 10μm≤H5≤50μm, preferably 15μm≤H5≤30μm, is satisfied.

6. The battery according to claim 1, wherein among the first grooves (321) on both sides of the first pole piece (3), the size of the outer first groove (321) along the third direction (Y) is greater than the size of the inner first groove (321) along the third direction (Y); and / or, the size of the outer first groove (321) along the first direction (Z) is greater than the size of the inner first groove (321) along the first direction (Z). ​ ​ ​ ​ ​ ​ The first groove (321) on the outer side is closer to the shell (1) than the first groove (321) on the inner side.

7. The battery of claim 1, wherein, the first tab (3) has a starting section (301) close to a winding center (O), an ending section (302) away from the winding center (O), and an intermediate section (303) between the starting section (301) and the ending section (302) along a winding direction of the jelly-roll, the starting section (301), the intermediate section (303), and the ending section (302) are sequentially connected along the winding direction of the jelly-roll, a dimension of the first groove (321) on the starting section (301) along the third direction (Y) is W1, a dimension of the first groove (321) on the ending section (302) along the third direction (Y) is W2, and 90 μm≤W1≤130 μm, 60 μm≤W2≤100 μm, and W1-W2≥20 μm are satisfied.

8. The battery of any one of claims 1-7, wherein, the second tab (5) has a first protrusion on one side surface close to the shell (1) along the first direction (Z), and has a first recess on the other side surface corresponding to the first protrusion, a sum of the positive projection areas of the first protrusion along the first direction (Z) in the same projection plane perpendicular to the first direction (Z) is a7, and a sum of the positive projection areas of the first grooves (321) on the one side surface of the first tab (3) along the first direction (Z) is a8, and 1.5≤a7 / a8≤12 is satisfied.

9. The battery of claim 8, wherein, the first tab (3) is a negative tab, and the second tab (5) is a positive tab; the positive tab comprises a cobalt-containing material, and the cobalt-containing material comprises at least one of lithium cobaltate, nickel-cobalt-manganese ternary material, and nickel-cobalt-aluminum ternary material.

10. The battery of claim 9, wherein, the first tab (3) is a negative tab, and the second tab (5) is a positive tab, the negative tab comprises a silicon-based material, a ratio of (Dv90-Dv10) / Dv50 between Dv10, Dv90, and Dv50 of the silicon-based material is A, and 0.2≤A≤0.5 is satisfied; and / or, the first groove (321) on the one side surface close to the shell (1) of the negative tab has a top slot away from the first current collector (31) along the first direction (Z) and a bottom slot close to the first current collector (31), a width H3 of the top slot is greater than a width H4 of the bottom slot, and 0.01≤A / (H3-H4)≤0.5 is satisfied.

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