Battery

Abstract

The embodiment of the invention provides a battery. The battery comprises a winding type electrode body, the winding type electrode body comprises a negative plate, a diaphragm and a positive plate which are stacked and wound, and the tail end face of the diaphragm is flush with the tail end face of the negative plate. The negative plate comprises a negative current collector and a negative active material layer, and the negative active material layer at the tail part of the negative plate is flush with the tail part of the negative current collector along the first direction Z; the negative active material layer comprises a silicon-based material, the content of silicon in the negative active material layer is x, and x is larger than or equal to 1.5 wt% and smaller than or equal to 60 wt%. And the peel strength F1 of the diaphragm and the negative plate meets the condition that F1 is greater than or equal to 1N / m < 2 > and less than or equal to 30N / m < 2 >. The value of x and the value of F1 meet the condition that x / F1 is larger than or equal to 0.0005 and smaller than or equal to According to the winding type electrode body, the peeling strength of the diaphragm and the negative plate is controlled within a certain range and is matched with the content of the silicon-based material, namely the content of the silicon element, so that high-temperature shrinkage of the diaphragm can be limited, the contact short circuit of the negative plate and the positive plate is avoided, and the safety of the battery is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular, to a battery. Background Art

[0002] Ion batteries, such as lithium-ion batteries, store and release electrical energy through the movement of ions between electrodes. These batteries typically consist of a positive electrode, a negative electrode, and a separator that allows ions to pass through. For example, the positive electrode, separator, and negative electrode are stacked and wound to form a battery cell. This is then completed through subsequent injection and packaging to create a ion battery.

[0003] Batteries formed with wound electrode bodies have a compact structure, high electrode material utilization, and high energy density, which helps improve battery life. However, batteries formed with wound electrode bodies in related technologies have certain problems.

[0004] For example, if the tail of the diaphragm extends beyond the tail of the negative electrode sheet, the ineffective thickness of the battery may be increased. Alternatively, if the tail of the diaphragm extends beyond the tail of the negative electrode sheet, the diaphragm may be easily folded, wrinkled, or shifted during winding and cutting, affecting the energy density and flatness of the battery formed by the wound electrode body, and thus affecting the battery cycle and safety of use. Summary of the Invention

[0005] In view of this, the embodiments of the present application provide a wound electrode body, a battery and an electrical device to solve the problems in the related art that the tail of the diaphragm of the battery formed by the wound electrode body easily leads to an increase in the invalid size of the battery, or the diaphragm is folded, wrinkled or shifted, thereby reducing the energy density and safety of the battery.

[0006] In a first aspect, an embodiment of the present application provides a wound electrode body, the wound electrode body comprising a negative electrode sheet, a separator, and a positive electrode sheet stacked and wound, wherein the tail end face of the separator is flush with the tail end face of the negative electrode sheet. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer. Along a first direction Z, the negative electrode active material layer at the tail of the negative electrode sheet is flush with the tail of the negative electrode current collector. The negative electrode active material layer comprises a silicon-based material. The silicon content in the negative electrode active material layer is x, where x satisfies: 1.5wt%≤x≤60wt%. The peel strength between the separator and the negative electrode sheet is F1, where F1 satisfies: 1N / m 2 ≤F1≤30N / m 2 The values ​​of x and F1 satisfy: 0.0005≤x / F1≤0.6.

[0007] In combination with the first aspect above, in one possible embodiment, the silicon-based material includes a silicon-carbon composite material, the silicon content in the silicon-carbon composite material is y, y satisfies: 20wt%≤y≤80wt%, and the tensile strength of the diaphragm in the third direction X is Q, Q satisfies: 100MPa≤Q≤700MPa; preferably, the values ​​of y and Q satisfy: 125≤Q / y≤3500.

[0008] In combination with the first aspect above, in one possible embodiment, a plurality of linear grooves are provided on the surface of the negative electrode active material layer, and the plurality of linear grooves have at least one of the following characteristics:

[0009] The width of each wire groove is 50μm to 200μm;

[0010] The depth of each groove is 5μm to 30μm;

[0011] The distance between two adjacent wire ducts is t, and t satisfies: 0.5mm≤t≤2.5mm;

[0012] The plurality of line grooves have an included angle α with the second direction Y, the second direction Y being the length direction of the negative electrode sheet, and α satisfies: 2°≤α≤80°; preferably, α satisfies: 40°≤α≤60°;

[0013] The plurality of line grooves are respectively at a third distance L1 from the head and tail of the negative electrode sheet, 1mm≤L1≤100mm; preferably, L1 satisfies: 10mm≤L1≤60mm.

[0014] In combination with the first aspect above, in a possible implementation manner, the relationship between t and the width W of the negative electrode sheet along the second direction satisfies: 5≤W / t≤250.

[0015] In combination with the first aspect above, in one possible embodiment, the separator includes a first separator and a second separator. Along the first direction Z, the first separator and the second separator are respectively arranged on both sides of the negative electrode sheet, the first separator is arranged close to the winding center of the wound electrode body, and the second separator is arranged away from the winding center of the wound electrode body. The elongation of the first separator is A1, and the elongation of the second separator is A2; A1 and A2 satisfy: A1<A2;

[0016] And / or, A1 satisfies: 10%≤A1≤220%, preferably, A1 satisfies: 30%≤A1≤200%;

[0017] And / or, A2 satisfies: 10%≤A2≤220%, preferably, A1 satisfies: 30%≤A2≤200%.

[0018] In combination with the above-mentioned first aspect, in a possible embodiment, along the first direction Z, the first diaphragm and the second diaphragm both include a first substrate layer and a first functional layer and a second functional layer respectively located on both sides of the first substrate layer, and the first functional layer and the second functional layer respectively include at least one of a polymer glue layer and a ceramic material; and the first functional layer faces the negative electrode sheet, the second functional layer faces the positive electrode sheet, the content of the polymer glue layer in the first functional layer is J1, and the content of the ceramic material is T1, the content of the polymer glue layer in the second functional layer is J2, and the content of the ceramic material is T2, wherein J1 and J2 satisfy: J1>J2, and T1 and T2 satisfy: T1<T2.

[0019] In combination with the first aspect above, in one possible embodiment, the wound electrode body includes a straight portion and a bent portion, the first functional layer includes a sheet-like polymer adhesive layer located in the straight portion, and the first functional layer includes a spherical particle polymer adhesive layer located in the bent portion.

[0020] In combination with the above-mentioned first aspect, in one possible embodiment, along the third direction X, the tail of the negative electrode sheet exceeds the tail of the positive electrode sheet, the positive electrode sheet includes a positive electrode double-sided coating area and a positive electrode single-sided coating area connected to the positive electrode double-sided coating area, the positive electrode single-sided coating area is provided with a positive electrode active material layer on one side surface facing the winding center of the wound electrode body, the positive electrode single-sided coating area is provided on the outermost circle of the wound electrode body, and the tail of the positive electrode sheet is provided with a first insulating member, and the first insulating member is provided on the side surface of the positive electrode single-sided coating area away from the winding center; preferably, the first insulating member is bonded to the tail of the diaphragm, and the bonding length between the first insulating member and the tail of the diaphragm is L2, L2 satisfies: 1mm≤L2≤15mm, and the bonding force between the first insulating member and the diaphragm is F2, and F2 satisfies: 5N / m 2 ≤F2≤200N / m 2 ; preferably,

[0021] The values ​​of L2 and F2 satisfy: 0.005≤L2 / F2≤3.

[0022] In combination with the first aspect above, in a possible embodiment, a second insulating member is provided at the junction of the positive electrode double-sided coating area and the positive electrode single-sided coating area. The second insulating member extends along the winding direction of the positive electrode sheet and is at least partially located in the positive electrode single-sided coating area. The first insulating member is simultaneously bonded to the tail of the side of the diaphragm away from the winding center, the tail end face of the negative electrode sheet and at least part of the second insulating member.

[0023] In combination with the first aspect above, in a possible embodiment, the negative electrode sheet has a negative electrode sheet winding starting end, the winding starting end of the diaphragm is flush with the negative electrode sheet winding starting end, the innermost circle of the positive electrode sheet has a first positive electrode straight section, a first positive electrode bent section and a second positive electrode straight section, the end of the first positive electrode straight section away from the first positive electrode bent section is the winding starting end of the positive electrode sheet, the first positive electrode bent section is arranged opposite to the winding starting end of the negative electrode sheet, and along the third direction X, the winding starting end of the negative electrode sheet and the winding starting end of the positive electrode sheet extend in opposite directions.

[0024] In combination with the first aspect above, in a possible embodiment, a third insulating member is provided on the side surface of the first positive electrode bending section facing the winding center, and the third insulating member includes a second substrate layer and an adhesive layer, and the adhesive layer is provided on at least one side surface of the second substrate layer facing the first positive electrode bending section; preferably, the adhesive layer is arranged at intervals on the second substrate layer to form a blank area on the second substrate layer, and along the winding direction of the positive electrode sheet, at least part of the blank area is arranged corresponding to the first positive electrode bending section, the area of ​​the third insulating member is S1, and the projected area of ​​the adhesive layer on the third insulating member is S2, and S1 and S2 satisfy: 0.2≤S2 / S1≤0.8.

[0025] In a second aspect, the present application provides a battery comprising the wound electrode body described in any one of the above embodiments.

[0026] In a third aspect, the present application provides an electrical device comprising the above-mentioned battery.

[0027] In related technologies, the tail of the separator extends beyond the tail of the negative electrode sheet for a certain distance. This portion of the separator beyond the tail of the negative electrode sheet occupies ineffective volume, reducing the overall energy density of the battery. Furthermore, during winding and cutting, this portion of the separator, with one end being free and subject to limited restraint, is prone to wrinkling, rebounding, and shifting. This increases the ineffective thickness of the battery or reduces the internal flatness of the battery, further reducing the energy density of the battery cell and compromising battery safety.

[0028] According to the wound electrode body of the present application, the tail end face of the diaphragm is flush with the tail end face of the negative electrode sheet, which can reduce the amount of diaphragm used and save costs. At the same time, it can avoid the invalid volume occupation and the folding and displacement of the part of the diaphragm near the free end, which increases the invalid thickness of the battery cell or makes the battery cell locally uneven, thereby improving the energy density and safety of the battery. In addition, while fully utilizing silicon to improve the energy density of the battery, the diaphragm and the negative electrode sheet can have a suitable bonding force to avoid the diaphragm being unable to effectively bond with the negative electrode sheet due to insufficient bonding force when the negative electrode sheet expands, thereby failing to properly suppress the expansion of the negative electrode sheet. Then, it can be avoided that the tail of the diaphragm is displaced due to insufficient bonding force and cannot effectively cover the negative electrode sheet, resulting in poor coverage and increasing the risk of short circuit between the positive and negative electrode sheets. Thus, the thickness expansion rate of the battery can be effectively controlled, and the capacity retention rate and capacity retention rate pass rate of the battery can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic structural diagram of a wound electrode body in the related art.

[0030] Figure 2 This is a schematic diagram of the three-dimensional structure of a wound electrode body provided according to one embodiment of the present application.

[0031] Figure 3 for Figure 2 DD is a cross-sectional view of the wound electrode body shown in FIG.

[0032] Figure 4 for Figure 3 Schematic diagram of the structure of the negative electrode.

[0033] Figure 5 A cross-sectional view of a wound electrode body provided according to one embodiment of the present application.

[0034] Figure 6 for Figure 5 Schematic diagram of the structure of the negative electrode.

[0035] Figure 7 for Figure 5 Schematic diagram of the local structure of the outer part of the wound electrode body.

[0036] Figure 8 for Figure 5 Schematic diagram of the local structure of the innermost part of the wound electrode body.

[0037] Figure 9 Schematic diagram of the structure of a second insulating member provided according to one embodiment of the application.

[0038] Figure 10 This is a schematic structural diagram of a diaphragm provided according to one embodiment of the application.

[0039] Figure 11 Schematic diagram of the structure of a negative electrode sheet provided according to one embodiment of the application.

[0040] Figure 12 Schematic diagram of the structure of another negative electrode sheet provided according to one embodiment of the application.

[0041] Figure 13 This is a schematic structural diagram of a battery provided according to one embodiment of the application.

[0042] Reference numerals:

[0043] 1000, battery;

[0044] 100', wound electrode body; 10', negative electrode sheet; 11, negative electrode current collector; 111, negative electrode empty foil area; 20', positive electrode sheet;

[0045] 100, wound electrode body; 101, bent portion; 101a, first bent portion; 101b, second bent portion; 102, straight portion;

[0046] 10. Negative electrode sheet; 11. Negative electrode current collector; 12. Negative electrode active material layer; 14. Negative electrode sheet single-sided coating area; 15. Negative electrode sheet double-sided coating area; 16. Negative electrode blank foil area; 17. Wire slot;

[0047] 20. Positive electrode sheet; 21. First positive electrode straight section; 22. First positive electrode bent section; 23. Second positive electrode straight section;

[0048] 30, diaphragm; 30a, first diaphragm; 30b, second diaphragm; 31, first substrate layer; 32, first functional layer; 33, second functional layer;

[0049] 40. First insulating member; 50. Third insulating member; 51. Second base material layer; 52. Adhesive layer; 60. Second insulating member;

[0050] 200. Shell. DETAILED DESCRIPTION

[0051] It should be noted that the first direction in this article is the Z direction shown in the figure, which is also the thickness direction of the electrode sheet. The second direction is the Y direction shown in the figure, which is also the width direction of the electrode sheet. The direction perpendicular to the first direction Z and the second direction Y is the X direction shown in the figure, which is also the length direction of the electrode sheet. The winding direction in this article is the w direction shown in the figure, which is the winding direction of the positive electrode sheet, negative electrode sheet, and separator relative to the winding center EE.

[0052] Ion batteries, such as lithium-ion batteries, are batteries that store and release electrical energy through the movement of ions between electrodes. Figure 1Such batteries are usually formed in a certain form by a positive electrode sheet 20', a negative electrode sheet 10' and a separator 30' that can pass ions. For example, the positive electrode sheet 20', the separator 30' and the negative electrode sheet 10' are stacked in sequence and then wound to form a battery cell, and then prepared into an ion battery through subsequent liquid injection and packaging.

[0053] With the advancement of technology, various electronic products are increasingly demanding higher battery life, prompting people to place higher demands on the energy density of polymer lithium-ion batteries. Batteries formed by wound electrode bodies have a compact structure and high electrode material utilization, resulting in high energy density, which helps improve battery life.

[0054] However, reference Figure 1 In the related art, battery cells formed from wound electrode bodies present certain safety risks. For example, the tail of the separator 30' will extend beyond the tail of the negative electrode sheet 10' and extend a certain distance. The separator 30' that extends beyond the tail of the negative electrode sheet 10' will cause ineffective volume occupation, reducing the overall energy density of the battery. In addition, during winding and cutting, this part of the separator 30' is free at one end and is subject to limited restraint force, making it prone to wrinkling, rebounding, folding and shifting, thereby increasing the ineffective thickness of the battery or making the battery cell partially uneven, further reducing the energy density and safety of the battery cell.

[0055] To at least partially address the above issues, refer to Figure 2 、 Figure 3 and Figure 5 , an embodiment of the present application provides a wound electrode body 100. The wound electrode body 100 may include a negative electrode sheet 10, a separator 30, and a positive electrode sheet 20 that are stacked and wound, and the tail end surface of the separator 30 is flush with the tail end surface of the negative electrode sheet 10. For example, the negative electrode sheet 10 and the positive electrode sheet 20 are wound with the separator 30 between them into a wound electrode body 100 having a straight portion 102 and a bent portion 101 (for example, a first bent portion 101a and a second bent portion 101b). For example, the wound electrode body 100 having a straight portion 102 and a bent portion 101 is wound around a winding center EE. The negative electrode sheet 10 includes a negative electrode current collector 11 and a negative electrode active material layer 12. Along the first direction Z, the negative electrode active material layer 12 at the tail of the negative electrode sheet 10 is flush with the tail of the negative electrode current collector 11. The silicon content in the negative electrode active material layer 12 is x, where x satisfies the following: 1.5 wt% ≤ x ≤ 60 wt%; for example, 1.8 wt%, 2 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, or 55 wt%. In this way, the energy density of the battery 1000 can be increased by fully utilizing silicon.

[0056] The peel strength between the separator 30 and the negative electrode sheet 10 is F1, and F1 satisfies: 1N / m2≤F1≤30N / m 2 , for example, 1.5N / m 2 , 5N / m 2 , 10N / m 2 , 15N / m 2 , 20N / m 2 , or 25N / m 2 In this way, while fully utilizing silicon to increase the energy density of the battery 1000, the separator 30 and the negative electrode sheet 10 can maintain appropriate bonding strength. This can prevent the separator 30 from effectively bonding to the negative electrode sheet 10 due to insufficient bonding strength when the negative electrode sheet 10 expands, thereby preventing the separator 30 from being effectively bonded to the negative electrode sheet 10 and thus failing to properly suppress the expansion of the negative electrode sheet 10. Furthermore, this can prevent the tail of the separator 30 from shifting due to insufficient bonding strength and failing to effectively cover the negative electrode sheet 10, resulting in poor coverage and an increased risk of contact short circuits between the positive and negative electrode sheets 10. This effectively controls the battery's thickness expansion rate, improving the battery's capacity retention rate and capacity retention rate pass rate.

[0057] The values ​​of x and F1 satisfy: 0.005≤x / F1≤0.6, for example, 0.08, 0.1, 0.2, 0.3, 0.40 or 0.5, so that the peel strength matches the silicon content in the negative electrode active material layer.

[0058] For example, the peel strength between the negative electrode sheet 10 and the separator 30 can be modified in various ways. For example, the binder content and type in the negative electrode sheet 10 can be modified; and / or the content, thickness, and type of the polymer adhesive layer on the separator 30 can be modified. This application does not limit this, as long as the peel strength between the negative electrode and the separator is maintained.

[0059] In this way, the negative electrode active material layer 12 is provided on both opposing surfaces of the negative electrode sheet 10. This prevents the risk of burrs on the blank foil area of ​​the negative electrode sheet 10 puncturing the aluminum-plastic film, such as the rounded corners of the aluminum-plastic film. Furthermore, by matching the peel strength of the separator 30 to the negative electrode sheet 10 and the silicon-based material content, that is, the silicon content, this can better prevent the tail of the separator 30 from shifting due to insufficient bonding strength, resulting in ineffective coverage of the negative electrode sheet 10 and an increased risk of short-circuiting between the positive and negative electrode sheets. This effectively controls the thickness expansion rate of the battery, improving both the battery's capacity retention rate and the capacity retention rate pass rate.

[0060] Moreover, since there is no empty foil area at the tail of the negative electrode sheet 10, the tail of the diaphragm 30 can be set to be flush with the tail of the negative electrode sheet, so as to save the diaphragm 30 and save costs, while avoiding the part of the diaphragm 30 that exceeds the negative electrode sheet 10 to form an invalid volume, or the part of the diaphragm 30 that exceeds the negative electrode sheet 10 to wrinkle and rebound and fold due to the limited restraint force, thereby increasing the invalid thickness of the battery, or making the battery cell partially uneven, affecting the reduction of the energy density and safety of the battery cell, thereby improving the energy density of the battery 1000.

[0061] For example, along the second direction Y (i.e., the width direction of the negative electrode sheet 10), the separator 30 can extend beyond the negative electrode sheet 10, and the portions of the separator 30 on both sides of the negative electrode sheet 10 that extend beyond the negative electrode sheet 10 are combined. In this way, the separator 30 can cooperate with the negative electrode sheet 10 in the second direction Y to further restrict the shrinkage of the separator 30, thereby preventing the negative electrode sheet 10 from being exposed due to the shrinkage of the separator 30, further reducing the risk of shorting the positive and negative electrode sheets 10, and significantly improving the furnace temperature performance of the battery 1000.

[0062] Illustratively, the silicon-based material may be one or more of elemental silicon, silicon monoxide, and a silicon-based composite material.

[0063] For example, the silicon-based material may include a silicon-carbon composite material, in which the silicon content is y, and y satisfies: 20wt%≤y≤80wt%, for example, 3wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 50wt%, 60wt%, 70wt% or 75wt%, etc., so as to increase the specific capacity (which may be volume specific capacity or mass specific capacity) of the battery 1000 while avoiding causing excessive expansion. The tensile strength of the diaphragm 30 in the third direction X is Q, and Q satisfies: 100MPa≤Q≤700MPa, for example, 150MPa, 200MPa, 250MPa, 300MPa, 350MPa, 400MPa, 450MPa, 500MPa, 550MPa, 600MPa or 650MPa, so that the diaphragm 30 has a certain strength, which can prevent the diaphragm 30 from being stretched and thinned during the expansion of the negative electrode, thereby reducing the ionic conductivity and affecting the cycle performance of the battery cell.

[0064] The values ​​of y and Q can satisfy: 125≤Q / y≤3500, for example, 150, 200, 300, 400, 500, 600, 800, 1000, 1200, 1500, 2000, 2500 or 3000, so as to match the diaphragm 30 with the silicon content, thereby better avoiding the diaphragm 30 being stretched and thinned during the expansion of the negative electrode, thereby reducing the ionic conductivity and affecting the cycle performance of the battery cell.

[0065] For example, the silicon-carbon material (ie, silicon-carbon composite material) may be one or more of a nano-silicon-carbon composite material, a core-shell structured silicon-carbon composite material, and a porous carbon-coated silicon material.

[0066] By way of example only, the negative electrode current collector 11 of the negative electrode sheet 10 may be a strip of metal foil, and the negative electrode active material layer 12 may further include other negative electrode active materials capable of reversibly absorbing and releasing charge carriers, a binder, a dispersant, and various additives.

[0067] By way of example only, the metal foil mentioned in the above-mentioned negative electrode sheet 10 can be copper foil, the other negative electrode active materials mentioned can include one or more of graphite, soft carbon, hard carbon and intermediate phase microspheres, the binder mentioned can be a rubber such as styrene-butadiene rubber, and the dispersant mentioned can be a cellulose such as carboxymethyl cellulose.

[0068] refer to Figure 4 For example, the negative electrode sheet 10 may include a negative electrode blank foil area 16 , a negative electrode single-sided coating area 14 and a negative electrode sheet double-sided coating area 15 .

[0069] refer to Figure 6 Alternatively, the negative electrode sheet 10 may include a negative electrode sheet double-sided coating area 15 .

[0070] Here, the negative electrode empty foil area refers to the area on the negative electrode collector 11 where the negative electrode active material layer 12 is not provided, the negative electrode sheet single-sided coating area refers to the area on the negative electrode collector 11 where the negative electrode active material layer 12 is provided on one side, and the negative electrode sheet double-sided coating area refers to the area on the negative electrode collector 11 where the negative electrode active material layer 12 is provided on both sides (the sides along the first direction Z).

[0071] refer to Figure 4 、 Figure 6 、 Figure 11 and Figure 12 In some embodiments, a plurality of linear grooves 17 may be provided on the surface of the negative electrode active material layer 12. The width of each linear groove is 50 μm to 200 μm, for example, 60 μm, 80 μm, 100 μm, 120 μm, 150 μm, 170 μm or 190 μm, so as to avoid excessive loss of the negative electrode active material layer and reduction of the energy density of the battery due to the width of the linear groove 17 being too wide, or the inability to effectively store the electrolyte due to the width of the linear groove 17 being too small.

[0072] The depth of each groove is 5 μm to 30 μm, for example, 7 μm, 10 μm, 12 μm, 15 μm, 20 μm, 25 μm or 28 μm, so as to prevent the groove 17 from being too deep to damage the negative electrode collector 11 or too shallow to effectively store the electrolyte.

[0073] The spacing between adjacent wire grooves 17 is t, and t satisfies: 0.5mm≤t≤2.5mm, for example, 0.7mm, 1.0mm, 1.2mm, 1.5mm, 1.7mm, 1.9mm or 2.3mm, etc., to ensure the infiltration effect of the electrolyte while not removing too much active material.

[0074] The plurality of grooves 17 form an included angle α with the second direction Y, where α satisfies the following: 2°≤α≤80°, for example, 5°, 10°, 15°, 20°, 30°, 40°, 45°, 50°, 60°, 70°, or 75°, etc., to reduce powder loss during electrode cutting, improve the safety of the battery 1000, and facilitate electrolyte infiltration. Preferably, α satisfies the following: 40°≤α≤60°.

[0075] The plurality of line grooves 17 are respectively at a third distance L1 from the head and tail of the negative electrode sheet 10, 1mm≤L1≤100mm, for example, 2mm, 5mm, 10mm, 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm or 90mm, so as to form an air avoidance zone at the head and tail of the negative electrode sheet. The plurality of line grooves 17 provided on the surface of the negative electrode active material layer 12 usually destroy the adhesion of the surface layer of the negative electrode sheet 10. When the line grooves 17 are too close to the cutting end of the negative electrode sheet 10, it is very easy to cause powder falling during the cutting process. Therefore, controlling L1 within a certain range can, on the one hand, avoid the possibility of battery short circuit caused by powder falling, and on the other hand, avoid the risk of lithium plating when the powder falling area is large, causing safety problems such as short circuit. Preferably, L1 satisfies: 10mm≤L1≤60mm.

[0076] refer to Figure 12 In some embodiments, the relationship between the spacing t between adjacent wire grooves 17 and the width W of the negative electrode sheet 10 along the second direction satisfies: 5≤W / t≤250, for example, 10, 20, 40, 60, 80, 100, 130, 150, 180, 200, 220, or 240. This can ensure electrolyte wetting while preventing the wire grooves 17 from being too dense. This can also improve the contact points and contact area between the wire grooves 17 and the cutter during electrode sheet cutting, which can easily cause powder loss, thereby improving the safety performance of the battery 1000.

[0077] In the present application, the wire groove 17 can be formed by laser forming, mechanical processing, or other suitable forming methods.

[0078] Return Reference Figures 3 to 8In some embodiments, the separator 30 includes a first separator 30a and a second separator 30b. Along the first direction Z, the first separator 30a and the second separator 30b are disposed on either side of the negative electrode sheet 10, respectively. The first separator 30a is disposed near the winding center EE of the wound electrode assembly, while the second separator 30b is disposed away from the winding center EE of the wound electrode assembly. The first separator 30b has an elongation of A1, and the second separator 30b has an elongation of A2.

[0079] A1 and A2 satisfy: A1 < A2. The second separator 30b is positioned away from the winding core EE, subjecting it to greater tensile stress when the negative electrode expands. Setting a higher elongation for the second separator 30b can better prevent stretching damage to the second separator 30b, which could lead to reduced ionic conductivity and affect battery cell performance. This also prevents the second separator 30b from stretching and becoming thinner, potentially causing puncture by particles and affecting battery cell safety.

[0080] In one example, A1 satisfies the following: 10% ≤ A1 ≤ 220%, for example, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 100%, 150%, or 200%, so that the second separator 30b and the first separator 30a are well adapted to each other during operation and cell preparation. Preferably, A1 satisfies the following: 30% ≤ A1 ≤ 200%.

[0081] In one example, A2 satisfies the following: 10% ≤ A2 ≤ 220%, for example, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 100%, 150%, or 200%, so that the second separator 30b and the first separator 30a are well adapted to each other during operation and cell preparation. Preferably, A2 satisfies the following: 30% ≤ A2 ≤ 200%.

[0082] In one example, the second separator 30b and the first separator 30a can be hot-pressed together with the negative electrode sheet 10. Along at least one side of the width of the negative electrode sheet 10, the first separator 30a and the second separator 30b, extending beyond the width edge of the negative electrode sheet 10, are laminated together to form a composite region, which can improve the battery's furnace temperature test pass rate. The hot-pressing lamination process can refer to conventional settings in the field and will not be described in detail here. For example, the hot-pressing lamination pressure ranges from 100N to 6000N, and the temperature ranges from 80°C to 130°C.

[0083] refer to Figure 10In some embodiments, along the first direction Z, the first separator 30a and the second separator 30b each include a first substrate layer 31 and a first functional layer 32 and a second functional layer 33 located on either side of the first substrate layer 31. The first functional layer 31 and the second functional layer 32 each include at least one of a polymer glue layer and a ceramic material. The first functional layer 32 faces the negative electrode sheet 10, and the second functional layer 33 faces the positive electrode sheet 20.

[0084] The glue content in the first functional layer 32 is J1, and the ceramic material content is T2. The content of the polymer glue layer in the second functional layer 33 is J2, and the ceramic material content is T2. J1 and J2 satisfy: J1>J2, T1 and T2 satisfy: T1<T2, so that the glue content in the first functional layer 32 facing the negative electrode sheet 10 is higher, and the diaphragm 30 can be better composited and bonded with the negative electrode sheet 10 during compounding, while the ceramic content in the second functional layer 33 facing the positive electrode sheet 20 (for example, the positive electrode sheet 20) is higher, which can better prevent the active layer particles on the positive electrode sheet 20 from puncturing the diaphragm 30 due to its hardness or prevent the positive electrode sheet 20 from generating more heat on one side during use of the battery, and the surface temperature is higher, thereby affecting the safety performance of the battery 1000.

[0085] Illustratively, the polymer adhesive layer includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene tetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene modified and its copolymers, polyacrylonitrile, polymethyl methacrylate, polyacrylic acid, styrene-butadiene rubber (SBR), polyvinyl alcohol and its copolymer-modified polyvinyl alcohol, polyvinyl acetate, polyacrylamide, phenolic resin, epoxy resin, water-based polyurethane, ethylene-vinyl acetate copolymer, polyacrylic copolymer, lithium polystyrene sulfonate, pure benzene latex, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride-chlorotrifluoroethylene, polyvinyl pyrrolidone, polyethylene oxide, cellulose acetate, butyl cellulose, propyl cellulose, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, and cyanoethyl sucrose.

[0086] Exemplarily, the ceramic material includes at least one of silicon dioxide, aluminum oxide, zirconium dioxide, magnesium hydroxide, boehmite, barium sulfate, fluorphlogopite, fluorapatite, mullite, cordierite, aluminum titanate, titanium dioxide, copper oxide, zinc oxide, boron nitride, aluminum nitride, magnesium nitride, attapulgite or PI piezoelectric ceramics.

[0087] The separator 30 is a component that insulates the negative electrode sheet 10 from the positive electrode sheet 20 and includes a substrate layer. As some examples, the substrate layer of the separator 30 can be a porous tape made of a polyolefin resin such as polyethylene or polypropylene. Of course, other materials are also contemplated for the separator substrate layer, and this application does not impose any particular restrictions or requirements.

[0088] In some examples, in the straight portion 102, the first functional layer 32 includes a sheet-like polymer adhesive layer, which makes the adhesion between the diaphragm and the negative electrode sheet 10 in the straight portion 102 tighter. In the bent portion 101, the first functional layer 32 includes a spherical particle polymer adhesive layer, so that there is a certain gap between the diaphragm 30 and the portion of the negative electrode sheet 10 located in the bent portion 101, preventing lithium deposition and expansion and fracture of the negative electrode sheet 10 in the arc area of ​​the bent portion 101.

[0089] refer to Figure 3 and Figure 5 Along the third direction X, the tail of the negative electrode sheet 10 extends beyond the tail of the positive electrode sheet 20. A first insulating member 40 is provided at the tail of the positive electrode sheet 20. The positive electrode sheet 20 includes a positive electrode double-sided coating region and a positive electrode single-sided coating region connected to the positive electrode double-sided coating region. The positive electrode single-sided coating region is provided with a positive electrode active material layer on the side facing the winding center. The positive electrode single-sided coating region is provided at the outermost ring of the wound electrode body. The tail of the positive electrode sheet 20 is provided with a first insulating member 40. The first insulating member 40 is provided on the side of the positive electrode single-sided coating region away from the winding center. The first insulating member 40 is bonded to the tail of the separator 30 to constrain the tail of the separator 30, preventing the separator 30 from shifting and folding due to the lack of restraint, thereby preventing the negative electrode active material layer 12 from contacting the positive electrode sheet 20 and causing a short circuit.

[0090] refer to Figure 7 , the bonding length between the first insulating member 40 and the tail of the separator 30 is L2, and L2 satisfies: 1mm≤L2≤15mm, for example, 1.5mm, 2mm, 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 12mm or 14mm, etc. In this way, the bonding length of the first insulating member 40 at the tail of the separator 30 can ensure that the first insulating member 40 constrains the tail of the separator 30, avoiding the situation where the bonding length is too short to form an effective constraint, or the bonding length is too long to cause lithium deposition, affecting the utilization rate of the active material and the energy density of the battery 1000. That is, it can ensure that there is sufficient bonding force between the first insulating member 40 and the second separator 30b without lithium deposition and maximizing the utilization of the active material, reducing the risk of the second separator 30b shifting and folding, thereby causing the negative active material layer 12 at the tail of the negative electrode sheet 10 to contact the empty foil area of ​​the positive electrode current collector and cause a short circuit.

[0091] Furthermore, the second separator 30b can be prevented from shifting and rubbing against the negative active material layer 12, thereby preventing the negative active material layer 12 from losing powder and causing a poor K value. Furthermore, the separator 30 can be prevented from shifting and folding, thereby preventing the current collector burrs at the tail of the negative electrode sheet 10 or the risk of active material particles being squeezed into the aluminum-plastic film casing and puncturing the aluminum-plastic film, causing battery cell failure.

[0092] In addition, the separator 30 can be constrained from shrinking during the oven test to prevent the negative active material layer 12 at the tail of the negative electrode sheet 10 from leaking out and contacting the positive electrode sheet to cause a short circuit, thereby improving the ability to pass the oven test.

[0093] The bonding strength between the first insulating member 40 and the diaphragm 30 is F2, and F2 satisfies: 5N / m 2 ≤F2≤200N / m 2 , for example, 6N / m 2 , 10N / m 2 , 20N / m 2 , 50N / m 2 , 80N / m 2 , 100N / m 2 , 120N / m 2 , 150N / m 2 , 170N / m 2 or 190N / m 2 In this way, the bonding strength between the first insulating member 40 and the diaphragm 30 is controlled within a suitable range, ensuring that the first insulating member 40 and the diaphragm 30 have a suitable bonding force, thereby further constraining the diaphragm 30 and avoiding the above-mentioned problems caused by displacement and folding of the diaphragm 30, thereby improving the above-mentioned effect.

[0094] The values ​​of L2 and F2 satisfy the following: 0.005 ≤ L2 / F2 ≤ 3, for example, 0.008, 0.01, 0.06, 0.08, 1.0, 1.5, 2.0, or 2.5. In this way, the bonding strength and bonding length of the first insulating member 40 are adapted to better constrain the diaphragm 30, avoiding the aforementioned problems caused by displacement and folding of the diaphragm 30, thereby further improving the aforementioned effect.

[0095] It should be noted that if the L2 area in the battery is small and affects the accuracy of the test results of measuring F2, the battery can be disassembled to remove the first insulating member 40 and the diaphragm 30 of the same length as the first insulating member 40. After cleaning, the two can be bonded together, and then the test results of F2 can be obtained according to the specific test process.

[0096] refer to Figure 5 In some embodiments, a second insulating member 60 is provided at the junction of the positive electrode double-sided coating area and the positive electrode single-sided coating area. The second insulating member 60 extends along the winding direction of the positive electrode sheet 20 and is at least partially located in the positive electrode single-sided coating area. The first insulating member 40 is simultaneously bonded to the tail of the separator 30 on the side away from the winding center EE, the tail end surface of the negative electrode sheet 10 and at least a portion of the second insulating member 60.

[0097] In this way, the second insulating member 60 can enhance the tensile strength of the portion of the positive electrode sheet 20 at the outermost edge of the wound electrode body 100 located at the bend 101, thereby reducing the risk of fracture in this area and improving the battery's cycling performance. Furthermore, the first insulating member 40 can extend over the second insulating member 60, further enhancing the tensile strength of the portion of the positive electrode sheet 20 at the outermost edge of the wound electrode body 100 located at the bend 101, further reducing the risk of fracture in this area and further improving the battery's cycling performance.

[0098] Furthermore, while securing the tail of the positive electrode sheet 20, the first insulating member 40 can also simultaneously adhere to the tail of the separator 30 and the end surface of the tail of the negative electrode sheet 10, further constraining the tail of the negative electrode sheet 10 and the separator 30, preventing the separator 30 and the negative electrode sheet 10 from shifting or folding, and further preventing the tail of the negative electrode sheet 10 from contacting and short-circuiting with the tail of the positive electrode sheet 20. Furthermore, the first insulating member 40 can prevent burrs on the end surface of the tail of the negative electrode sheet 10 or active material particles from contacting and pressing the aluminum-plastic film casing 200, thereby piercing the aluminum-plastic film and causing cell failure, thereby improving the battery's cycling performance.

[0099] Return to Reference Figure 5 and Figure 8 The negative electrode sheet 10 has a negative electrode sheet winding starting end, and the winding starting end of the separator 30 is flush with the winding starting end of the negative electrode sheet 10. The innermost circle of the positive electrode sheet 20 has a first positive electrode straight section 21, a first positive electrode bent section 22, and a second positive electrode straight section 23. The end of the first positive electrode straight section 21 away from the first positive electrode bent section 22 is the winding starting end of the positive electrode sheet 20. The first positive electrode bent section 22 is arranged opposite to the winding starting end of the negative electrode sheet 10. Along the third direction X, the winding starting end of the negative electrode sheet 10 and the winding starting end of the positive electrode sheet 20 extend in opposite directions.

[0100] Continue to refer Figures 5 to 9 , a third insulating member 50 is provided on the surface of the side of the first positive electrode bending section 22 facing the winding center EE. The third insulating member 50 includes a second substrate layer 51 and an adhesive layer 52 (i.e., a glue layer) provided on the second substrate layer 51. The adhesive layer 52 is provided on at least the surface of the second substrate layer 51 facing the first positive electrode bending section 22. Preferably, the adhesive layer 52 is provided on the second substrate layer 51 at intervals to form a blank area on the second substrate layer 51, that is, the adhesive layer 52 is distributed at intervals on the second substrate layer 51. In this way, the adhesion of the third insulating member 50 to the positive electrode sheet 20 can be reduced, thereby reducing the constraint on the positive electrode sheet 20 and preventing the positive electrode sheet 20 from breaking during winding and bending.

[0101] In one embodiment, the active layer on the surface of the side of the first positive electrode bending section 22 facing the winding center EE is provided with a thinning area (not shown in the figure), and the third insulating member 50 can be arranged in the area where the thinning area of ​​the first positive electrode bending section is located to reduce the risk of lithium deposition and positive electrode fragmentation at this position.

[0102] In the winding direction of the positive electrode sheet 20, at least part of the blank area is arranged corresponding to the first positive electrode bending section 22, the area of ​​the third insulating member 50 is S1, and the projected area of ​​the adhesive layer 52 on the third insulating member 50 is S2. S1 and S2 satisfy: 0.2≤S2 / S1≤0.8, for example, 0.3, 0.4, 0.5, 0.6 or 0.7, to balance the adhesion and constraint force.

[0103] The positive electrode sheet 20 may include a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer may include a positive electrode active material. In addition, the positive electrode active material layer may also include one or more of a binder, a conductive agent, and a solvent.

[0104] Illustratively, the positive electrode active material includes one or more of a nickel-cobalt-lithium manganese oxide ternary material, a lithium cobalt oxide material, a nickel-cobalt-aluminum oxide material, a lithium manganese oxide material, a lithium iron phosphate material, and a lithium-rich manganese-based material.

[0105] For example, the binder may include one or more of polyvinylidene fluoride, polytetrachloroethylene, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyimide, or polyethylene.

[0106] For example, the conductive agent may include one or more of conductive ceramics, carbon black, graphite, graphene, polyaniline, polypyrrole, Ketjen black, acetylene black, and carbon nanotubes.

[0107] For example, the solvent may include one or more of N-methylpyrrolidone, water, ethanol and polyethylene glycol.

[0108] By way of example only, the positive electrode current collector may be a strip of metal foil, such as aluminum foil.

[0109] It should be noted that the first insulating member, the second insulating member and the third insulating member herein may be adhesive tape or an insulating coating, such as a UV curing adhesive insulating material.

[0110] It is understandable that those skilled in the art can split or combine the above embodiments to form new embodiments as needed.

[0111] Exemplary Battery 1000

[0112] refer to Figure 13 As shown, the embodiment of the present application further provides a battery 1000. The battery 1000 includes the wound electrode body 100 described above.

[0113] refer to Figure 13 The battery 1000 may include a wound electrode body 100 and a housing 200. The housing 200 may have an accommodating cavity therein, and one or more wound electrode bodies 100 may be accommodated in the accommodating cavity.

[0114] As shown in the figure, the housing 200 is illustratively flat and made of a relatively soft material, such as an aluminum-plastic film. That is, in this embodiment, the battery 1000 can be a soft-pack battery 1000.

[0115] It should be noted that the structure of other aspects of the battery 1000 may be the same as that of the previous battery 1000. For the purpose of brevity, this embodiment of the present application will not be described in detail.

[0116] The battery 1000 can be manufactured into a wound electrode body 100 by using a conventional winding structure, with the positive electrode sheet 20, the negative electrode sheet 10, and the separator. The battery 1000 is then manufactured through steps such as packaging, liquid injection, formation, secondary sealing, and capacity separation. The electrolyte is a conventional commercially available electrolyte, and this application does not impose any special requirements on this electrolyte.

[0117] The battery 1000 provided according to the embodiment of the present application has the corresponding effects of the aforementioned wound electrode body 100 . Please refer to the above for details, which will not be repeated here.

[0118] It should be noted that in this application, "battery 1000" refers to a storage device that can be repeatedly charged and discharged, which can be interpreted as the concept of a "secondary battery." In the embodiments of this application, the concept of "secondary battery" can include lithium-ion secondary batteries, etc.

[0119] Exemplary Power-Consuming Equipment

[0120] In a third aspect, the present application provides an electric device, which includes the above-mentioned battery 1000. The electric device can be a charging device or a power-consuming device.

[0121] It should be noted that, for the sake of clarity, the entire structure of the aforementioned wound electrode body 100 and battery 1000 is not described. To achieve their necessary functions, those skilled in the art may set other structures according to specific application scenarios, and the embodiments of this application do not limit this. At the same time, for the sake of clarity, the entire preparation process and technology of the aforementioned wound electrode body 100 and battery 1000 are not described. To achieve the preparation of the wound electrode body 100 and battery 1000, those skilled in the art may select the preparation engineering and technology according to the specific application scenario, and the embodiments of this application do not limit this.

[0122] It should be understood that the term "including" and its variations used in the embodiments of the present application are open-ended, i.e., "including but not limited to." The term "according to" means "at least in part according to." The term "one embodiment" means "at least one embodiment," and the term "another embodiment" means "at least another embodiment." The term "plurality" means "more than one," which is intended to cover two, three, or more embodiments.

[0123] It should be understood that although the terms "first" or "second" may be used in the embodiments of the present application to describe various elements, for example, the first positive electrode active material layer and the second positive electrode active material layer, these elements are not defined by these terms, and these terms are only used to distinguish one element from another.

[0124] The scope of protection of the embodiments of this application is not limited to the above-mentioned embodiments. Any changes or substitutions that can be conceived by a person skilled in the art within the technical scope disclosed in the embodiments of this application should be included in the scope of protection of the embodiments of this application. Therefore, the scope of protection of the embodiments of this application should be based on the scope of protection of the claims.

[0125] The present application is described in detail below with reference to specific embodiments, which are intended to help understand but not limit the present application.

[0126] Unless otherwise specified, the materials and reagents used in the following examples are all commercially available. The processing procedures and techniques involved are conventional techniques unless otherwise specified.

[0127] Example 1

[0128] Preparation of negative electrode sheet 10: Disperse the negative electrode active material (i.e., negative electrode active material), sodium carboxymethyl cellulose, styrene-butadiene rubber, and conductive carbon black in a solvent (alternatively water) at a mass ratio of 93:2.5:1.5:3 and mix thoroughly to obtain a slurry. The prepared negative electrode slurry is evenly coated on copper foil, dried at 100°C, and then roll-pressed and slit to obtain the negative electrode sheet 10. The negative electrode active material is graphite and a silicon-carbon composite material. The silicon content x in the negative electrode active material is 19%, and the silicon content y in the silicon-carbon composite material is 45%. The silicon content is controlled by controlling the content of the silicon-carbon composite material in the negative electrode active material.

[0129] The negative electrode sheet 10 is laser-formed with multiple linear grooves 17. The angle α between the linear grooves 17 and the second direction is 45°. The spacing t between adjacent linear grooves 17 is 1.5 mm. L2 = 7 mm. The width W of the negative electrode sheet 10 is 50 mm, and W / t = 33.

[0130] Preparation of the positive electrode sheet 20: The positive electrode active material, lithium nickel cobalt manganese oxide (NCM), the binder, polyvinylidene fluoride, and the conductive agent, carbon black, are mixed in a ratio of 97.2:1.8:1 by weight. An appropriate amount of N-methylpyrrolidone is added as a solvent and stirred evenly to form a uniformly dispersed electrode slurry with a solid content of 65 wt%. The prepared positive electrode slurry is evenly coated onto aluminum foil, rolled, and slit to form the positive electrode sheet 20. A single-sided coating area is provided at the rear of the positive electrode sheet 20.

[0131] Then, the positive electrode sheet 20 , the negative electrode sheet 10 and the separator are wound together to form a wound battery 1000 according to a conventional winding structure.

[0132] A second insulating member 60 (eg, second adhesive tape) is provided at the junction of the positive electrode single-sided coating area and the positive electrode double-sided coating area at the tail of the positive electrode sheet 20 , and the second adhesive tape covers the positive electrode single-sided coating area.

[0133] The tail of the negative electrode sheet 10 extends beyond the tail of the positive electrode sheet 20. A first insulating member 40 (e.g., a first adhesive tape) is provided at the tail of the positive electrode sheet 20. The first insulating member 40 is attached to the tail of the separator at a first distance L2 = 7 mm. The bonding strength F2 between the first insulating member 40 and the separator 30 is 27 N / m. 2 , L1 / F2=0.26. The first insulating member 40 is bonded to the end surface of the negative electrode sheet 10 and the second insulating member 60 at the same time.

[0134] The negative electrode sheet 10 has a negative electrode sheet winding starting end, and the innermost circle of the positive electrode sheet 20 has a first positive electrode straight section 21, a first positive electrode bent section 22, and a second positive electrode straight section 23. The end of the first positive electrode straight section 21 away from the first positive electrode bent section 22 is the winding starting end of the positive electrode sheet 20. The first positive electrode bent section 22 is arranged opposite the winding starting end of the negative electrode sheet 20. Along the third direction X, the winding starting end of the negative electrode sheet 10 and the winding starting end of the positive electrode sheet 20 extend in opposite directions.

[0135] A third insulating member 50 (e.g., a third adhesive tape) is provided on the side of the first positive electrode bend 22 facing the winding center EE. The third insulating member 50 includes a second substrate layer 51 and an adhesive layer 52 (i.e., adhesive) provided on at least one side of the second substrate layer 51. The adhesive layer 52 is provided at intervals to form a blank area on the second substrate layer 51.

[0136] Along the winding direction of the positive electrode sheet 20, the blank area is arranged corresponding to the first positive electrode bending section 22. The total area S1 of the third insulating member 50 is 7.2 cm 2 The total area S2 of the adhesive layer is 3.6 cm 2 , S1 / S2=0.5.

[0137] The peel strength F1 between the separator and the negative electrode sheet 10 is 18N / m 2The tensile strength Q of the diaphragm in the third direction X is 350 MPa, Q / y is 1778, the elongation A1 of the first diaphragm 30a is 100%, the elongation A2 of the second diaphragm 30b is 110%, and A1 / A2 is 91%.

[0138] Then, the wound battery 1000 is further processed through steps such as packaging, electrolyte injection, formation, secondary sealing, and capacity separation to form the battery 1000. Here, the electrolyte is a conventional commercially available electrolyte.

[0139] Example 2

[0140] This embodiment is carried out with reference to the embodiment 1, except that the content x of the silicon-based material is 2 wt %, and x / F1=0.0011.

[0141] Example 3

[0142] This embodiment is carried out with reference to the embodiment 1, except that the content x of the silicon-based material is 60 wt %, and x / F1=0.0333.

[0143] Example 4

[0144] This embodiment is carried out with reference to the embodiment 1, except that F1 is 1.1 N / m 2 , x / F1=0.1727.

[0145] Example 5

[0146] This embodiment is carried out with reference to the embodiment 1, except that F1 is 30N / m 2 , x / F1=0.0063.

[0147] Example 6

[0148] This embodiment is carried out with reference to embodiment 3, except that F1 is 1.1 N / m 2 , x / F1=0.5455.

[0149] Example 7

[0150] This example was carried out with reference to Example 1, except that x=15 wt %, y=21 wt %, x / F1=0.0083, and Q / y=1667.

[0151] Example 8

[0152] This example was carried out with reference to Example 1, except that x=55 wt %, y=78 wt %, x / F1=0.0306, and Q / y=449.

[0153] Example 9

[0154] This embodiment is carried out with reference to the embodiment 1, except that Q=700 MPa and Q / y=1556.

[0155] Example 10

[0156] This example is carried out with reference to Example 1, except that Q=105 MPa and Q / y=233.

[0157] Example 11

[0158] This example was carried out with reference to Example 10, except that x=58 wt%, y=79 wt%, Q=100 MPa, x / F1=0.0322, and Q / y=127.

[0159] Example 12

[0160] This example was carried out with reference to Example 9, except that x=12 wt%, y=20 wt%, Q=698 MPa, x / F1=0.0067, and Q / y=3490.

[0161] Example 13

[0162] This example was carried out with reference to Example 1, except that x=53 wt%, y=79 wt%, Q=80 MPa, x / F1=0.0294, and Q / y=101.

[0163] Example 14

[0164] This example was carried out with reference to Example 9, except that y=18 wt%, Q=698 MPa, and Q / y=3878.

[0165] Example 15

[0166] This example is carried out with reference to Example 1, except that x = 59 wt%, F1 = 18 N / m 2 , y=82wt%, Q=100MPa, x / F1=0.0328, Q / y=122.

[0167] Example 16

[0168] This embodiment is carried out with reference to the embodiment 1, except that S1=15.63cm 2 , S1 / S2=0.23.

[0169] Example 17

[0170] This embodiment is carried out with reference to the embodiment 1, except that S1=4.61cm 2 , S1 / S2=0.78.

[0171] Example 18

[0172] This example is carried out with reference to Example 1, except that S1 = 20 cm 2 , S1 / S2=0.18.

[0173] Example 19

[0174] This embodiment is carried out with reference to the embodiment 1, except that S1=4.23 cm 2 , S1 / S2=0.85.

[0175] Example 20

[0176] This embodiment is carried out with reference to the embodiment 1, except that L2=2 mm and L2 / F2=0.07.

[0177] Example 21

[0178] This embodiment is carried out with reference to the embodiment 1, except that L2=14 mm and L2 / F2=0.52.

[0179] Example 22

[0180] This embodiment is carried out with reference to the embodiment 1, except that L2 = 7 mm, F2 = 6 N / m 2 , L2 / F2=1.16.

[0181] Example 23

[0182] This example is carried out with reference to Example 22, except that F2 = 198 N / m 2 , L2 / F2=0.035.

[0183] Example 24

[0184] This example is carried out with reference to Example 22, except that F2 = 3 N / m 2 , L2 / F2=2.33.

[0185] Example 25

[0186] This embodiment is carried out with reference to the embodiment 1, except that L2=0.4 mm and L2 / F2=0.015.

[0187] Example 26

[0188] This embodiment is carried out with reference to the embodiment 1, except that L2=18 mm and L2 / F2=0.667.

[0189] Example 27

[0190] This embodiment is carried out with reference to the embodiment 1, except that F2 = 220 N / m 2 , L2 / F2=0.032.

[0191] Comparative Example 1

[0192] This comparative example was carried out with reference to Example 1, except that x=0.8 wt %, x / F1=0.0004.

[0193] Comparative Example 2

[0194] This comparative example was carried out with reference to Example 1, except that x=65 wt %, x / F1=0.0361.

[0195] Comparative Example 3

[0196] This comparative example is carried out with reference to Example 1, except that F1 = 0.5 N / m 2 , x / F1=0.38.

[0197] Comparative Example 4

[0198] This comparative example is carried out with reference to Example 1, except that F1 = 32 N / m 2 , x / F1=0.0059.

[0199] Material performance testing

[0200] 1. Energy density: The battery 1000 prepared in the comparative example and the embodiment was charged and discharged at 0.5C / 0.5C for capacity calibration and weighed, and the thickness, width and height of the battery cell were measured. The battery cell volume V = height × thickness × width was calculated to calculate the volume energy density. Among them, V nominal : nominal voltage of the battery (unit: V), C: nominal capacity of the battery (unit: Ah), V: battery volume (unit: cm 3 ).

[0201] 2. Battery 1000T cycle performance and pass rate test:

[0202] Where, C0: initial capacity (discharge capacity of the first cycle), C n : discharge capacity after the nth cycle.

[0203] (1) Initial capacity test (C0)

[0204] First charge: Charge at a constant current of 0.2C to the cut-off voltage (e.g. 4.5V), then switch to constant voltage charging until the current drops to 0.05C.

[0205] First discharge: Discharge at a constant current of 0.2C to the cut-off voltage (e.g. 3.0V), and record the discharge capacity C0.

[0206] (2) Cyclic test (Cn )

[0207] a. Cycling conditions: Test at 25℃±2℃;

[0208] b. Cyclic charge system: 20A-90s or 4.18V to 2.8C-4.26V to 2.5C-4.3V to 2C-4.45V (cutoff at 1.2C) to 1.2C-4.5V (cutoff at 1.0C) to 1.0C-4.545V (cutoff at 0.126C) / 1.5C-3.3V to 0.7C-3V-1200T (20mV reduction after 400T).

[0209] c. Battery 1000T cycle pass rate requirement: Each group tests 6 battery cells, and each battery cell cycles 1000 times. It passes if the capacity retention rate is greater than 80%. If the capacity retention rate of all 6 battery cells is greater than 80%, the pass rate is 6pcs / 6pcs. If only 3 of the 6 battery cells have a capacity retention rate greater than 80%, the pass rate is 6pcs / 3pcs.

[0210] 3. Battery thickness expansion rate test:

[0211] H0: initial thickness of the cell, H n : Cell thickness after the nth cycle.

[0212] Test method and requirements for thickness expansion rate of cycled battery cells: Use a thickness tester to test the thickness of the battery cell every 50 cycles. It is required that the thickness expansion rate of the battery cell should be less than 10% after 1000 cycles.

[0213] 4. Peel strength and adhesive strength test methods (F1, F2)

[0214] Sample preparation

[0215] Size: Cut the required test sample into standard size (such as 24mm×50mm) according to the requirements of the test equipment.

[0216] Quantity: 6 samples were tested in each group to ensure data accuracy.

[0217] 4.2. Test equipment

[0218] Tensile Tester; Range: 100N; Accuracy: 0.01N; Fixture: 90° or 180° peeling fixture

[0219] 4.3. Test steps

[0220] a. Fix the sample in the clamp of the tensile tester.

[0221] b. Set the test speed and angle.

[0222] c. Start the test and record the force value during the peeling process.

[0223] d. After the test is completed, record the maximum peel force or average peel force / adhesion force.

[0224] e. Repeat the test for 6 samples and calculate the average value.

[0225] f. Data recording and analysis

[0226] Peel force / adhesion force (N): Unit is Newton (N)

[0227] Peel strength per unit area (N / m 2 ):

[0228]

[0229] 5. Measuring the Area S1 of the Third Insulating Member 50 and the Area S2 of the Adhesive Layer 52: Lay the third insulating member 50 flat on a work surface. Use a measuring tool to measure the width and length of the third insulating member 50 and the width and length of the adhesive layer 52. Calculate: S1 = width * length; S2 = width * length.

[0230] 6. Diaphragm tensile strength and elongation

[0231] Diaphragm tensile strength test method and standard: GB / T 10004-2008 "Plastic composite film bags": applicable to the tensile strength test of diaphragms; or, ISO 6781-1:2012 "Plastic film and sheeting - Determination of tensile properties": applicable to the tensile strength test of plastic film and sheeting, which can be used as a reference for diaphragm testing.

[0232] Specimen preparation: Cut the specimen according to the standard requirements, usually a rectangular specimen (length 100mm, width 10mm). The specimen should avoid edge defects and ensure a smooth surface.

[0233] Test equipment: A Universal Tensile Tester equipped with a fixture and appropriate sensors was used.

[0234] Test speed: tensile speed 10mm / min or 50mm / min, depending on the material properties.

[0235] Test temperature: The standard test temperature is 23±2℃.

[0236] Test steps: Clamp the specimen between the upper and lower fixtures of the testing machine, ensuring that the specimen axis is aligned with the center of the fixture. Start stretching and record the maximum force and length of the specimen at break.

[0237] Calculate tensile strength: Tensile strength = maximum force / original cross-sectional area.

[0238] Calculate the elongation at break (also known as the extension): elongation at break = (break length - original length) / original length.

[0239] 7. Test method and standard for silicon content in negative electrode active layer

[0240] After disassembling the lithium-ion battery, remove the negative electrode sheet 10, soak and rinse it with dimethyl carbonate, and air dry it. Then, using the SEM backscattering mode, select at least five silicon-based particles and use EDS point scanning mode to determine the silicon content percentage of each silicon-based particle. The average silicon content percentage of the silicon-based particles is then calculated. The dried negative electrode sheet is then subjected to a high-temperature treatment at 400°C ± 5°C for 2 hours (e.g., in a tube furnace under a nitrogen or argon atmosphere). The negative active material layer 12 is then peeled off from the negative current collector 11, and the material of the negative active material layer 12 is collected.

[0241] In the silicon content test, a thermogravimetric analyzer (such as TGA 550 thermogravimetric analyzer) is used, and the sample size for the test is 5mg-15mg. The sample is heated from room temperature to 900°C at a heating rate of 10°C / min in an air or oxygen atmosphere, and kept at 900°C for 40 minutes, so that the non-silicon components in the negative electrode active material layer 12 can be volatilized while the silicon can be fully oxidized to silicon dioxide. The weight percentage at the end of the entire test process is the ash content of the negative electrode active layer. The ash value is divided by the molar mass of silicon dioxide and then multiplied by the molar mass of silicon to obtain the percentage of silicon element in the negative electrode active layer. The mass content of silicon-based particles in the negative electrode active material layer 12 can be calculated from the percentage of silicon element and the average silicon content of silicon-based particles.

[0242] Table 1 shows the test results.

[0243] Table 1

[0244]

[0245]

[0246] From the above data, it can be seen that when the silicon content is at the upper limit, although the energy density of the battery is relatively high, the thickness expansion rate of the battery is relatively high, which may cause partial damage to the silicon particles and lead to a relative decrease in the capacity retention rate.

[0247] When Q is lower than the lower limit, the diaphragm 30 is insufficiently strong and may be damaged during the cycle, thereby affecting the cycle performance, resulting in a decrease in the cycle performance and a decrease in the cycle performance pass rate. When the silicon content in the silicon-carbon composite material is low, the energy density of the battery is low, the cycle performance of the battery is reduced, and the cycle performance pass rate is reduced. When the silicon content in the silicon-carbon composite material exceeds the upper limit, although the battery capacity density is high, the thickness expansion rate of the battery is high, which may cause the electrode and diaphragm to rupture during the battery cycle, thereby resulting in low cycle performance and cycle performance pass rate of the battery.

[0248] If S1 / S2 is below the lower limit, the adhesive layer on the third insulating member 50 (e.g., third adhesive tape) is less, resulting in lower adhesion. This may cause the third insulating member 50 to separate from the positive electrode sheet 20 during cycling, reducing the resistance to expansion in that area of ​​the positive electrode sheet 20 and leading to rupture of the positive electrode sheet 20, which in turn reduces the battery's cycling performance and cycling performance pass rate. If S1 / S2 is above the upper limit, the restraining force on the positive electrode sheet 20 is excessive, affecting its deformation during expansion, potentially causing damage to the positive electrode sheet 20, which in turn reduces the battery's cycling performance and cycling performance pass rate.

[0249] When the bonding length L2 of the first insulating member 40 on the diaphragm 30 is short or the bonding force F2 is small, the restraining force on the tail of the diaphragm 30 is limited. During the battery cycle, the tail of the diaphragm 30 (such as the second diaphragm 30b) is easily displaced or folded, and the furnace temperature performance of the diaphragm 30 is poor, which in turn causes the negative electrode active material layer 12 to easily contact and short-circuit with the positive electrode sheet 20. This leads to a decrease in the battery's cycle performance and cycle performance pass rate. When the bonding length L2 of the first insulating member 40 on the diaphragm 30 is long or the bonding force F2 is small, it affects the transmittance of the diaphragm 30 to a certain extent, which in turn causes a decrease in the battery's energy density, and a decrease in the battery's cycle performance and cycle performance pass rate.

[0250] When x is below the lower limit, the silicon content is low, resulting in a lower battery energy density, decreased cycle performance, and decreased cycle performance pass rate. When x is above the upper limit, the silicon content is too high. Although the battery energy density is high, the battery thickness expansion rate is high, which may cause the electrode to rupture during the cycle process, thereby reducing the battery cycle performance and cycle performance pass rate.

[0251] When F1 is low, the bonding strength between the separator 30 and the negative electrode sheet 10 is low, making it easy for the separator 30 to shift and fold, resulting in the separator 30 not being able to fully cover the negative electrode sheet 10. This in turn causes a short circuit between the positive electrode sheet 20 and the negative electrode sheet, leading to a decrease in the battery's cycling performance and cycling performance pass rate. When F1 is high, the separator's deformation capacity is limited during the battery's cycling process, and it may tear, resulting in a decrease in the battery's cycling performance and cycling performance pass rate.

Claims

1. A battery, characterized in that: The invention comprises a wound electrode body, wherein the wound electrode body comprises a negative electrode sheet, a separator and a positive electrode sheet stacked and wound, and the tail end surface of the separator is flush with the tail end surface of the negative electrode sheet; wherein, The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. Along the first direction Z, the negative electrode active material layer at the tail of the negative electrode sheet is flush with the tail of the negative electrode current collector. The negative electrode active material layer includes a silicon-based material. The silicon content in the negative electrode active material layer is x, and x satisfies: 1.5wt%≤x≤60wt%. The peel strength between the separator and the negative electrode sheet is F1, and F1 satisfies: 1N / m 2 ≤F1≤30N / m 2 ,and, The values ​​of x and F1 satisfy: 0.0005≤x / F1≤0.

6.

2. The battery according to claim 1, characterized in that The silicon-based material includes a silicon-carbon composite material, the silicon content in the silicon-carbon composite material is y, y satisfies: 20wt%≤y≤80wt%, the tensile strength of the diaphragm in the third direction X is Q, Q satisfies: 100MPa≤Q≤700MPa; preferably, The values ​​of y and Q satisfy: 125≤Q / y≤3500.

3. The battery according to claim 1, characterized in that A plurality of line grooves are provided on the surface of the negative electrode active material layer; The plurality of line grooves have an included angle α with the second direction Y, the second direction Y being the length direction of the negative electrode sheet, and α satisfies: 2°≤α≤80°; preferably, α satisfies: 40°≤α≤60°; and / or The plurality of line grooves are respectively at a third distance L1 from the head and tail of the negative electrode sheet, 1mm≤L1≤100mm; preferably, L1 satisfies: 10mm≤L1≤60mm.

4. The battery according to any one of claims 1 to 3, characterized in that The separator includes a first separator and a second separator. Along the first direction Z, the first separator and the second separator are respectively arranged on both sides of the negative electrode sheet. The first separator is arranged close to the winding center of the wound electrode body, and the second separator is arranged away from the winding center of the wound electrode body. The elongation of the first separator is A1, and the elongation of the second separator is A2, wherein A1 and A2 satisfy: A1<A2; and / or, Said A1 satisfies: 10%≤A1≤220%, preferably, said A1 satisfies: 30%≤A1≤200%; and / or, The A2 satisfies: 10%≤A2≤220%. Preferably, the A1 satisfies: 30%≤A2≤200%.

5. The battery according to claim 4, characterized in that Along the first direction Z, the first diaphragm and the second diaphragm each include a first substrate layer and a first functional layer and a second functional layer respectively located on both sides of the first substrate layer, and the first functional layer and the second functional layer respectively include at least one of a polymer adhesive layer and a ceramic material; and The first functional layer faces the negative electrode sheet, the second functional layer faces the positive electrode sheet, the content of the polymer glue layer in the first functional layer is J1, the content of the ceramic material is T1, the content of the polymer glue layer in the second functional layer is J2, the content of the ceramic material is T2, wherein, J1 and J2 satisfy: J1>J2, T1 and T2 satisfy: T1<T2.

6. The battery according to claim 5, characterized in that The wound electrode body includes a straight portion and a bent portion, and the first functional layer includes a sheet-like polymer adhesive layer located in the straight portion and a spherical particle polymer adhesive layer located in the bent portion.

7. The battery according to any one of claims 1 to 3, characterized in that Along the third direction X, the tail of the negative electrode sheet exceeds the tail of the positive electrode sheet, the positive electrode sheet includes a positive electrode double-sided coating area and a positive electrode single-sided coating area connected to the positive electrode double-sided coating area, the positive electrode single-sided coating area is provided with a positive electrode active material layer on a side surface facing the winding center of the wound electrode body, the positive electrode single-sided coating area is provided on the outermost circle of the wound electrode body, the tail of the positive electrode sheet is provided with a first insulating member, the first insulating member is provided on a side surface of the positive electrode single-sided coating area away from the winding center, the first insulating member is bonded to the tail of the separator, the bonding length between the first insulating member and the tail of the separator is L2, and L2 satisfies: 1mm≤L2≤15mm, and the bonding strength between the first insulating member and the separator is F2, and F2 satisfies: 5N / m 2 ≤F2≤200N / m 2 ; preferably, The values ​​of L2 and F2 satisfy: 0.005≤L2 / F2≤3.

8. The battery according to claim 7, characterized in that A second insulating member is provided at the junction of the positive electrode double-sided coating area and the positive electrode single-sided coating area. The second insulating member extends along the winding direction of the positive electrode sheet and is at least partially located in the positive electrode single-sided coating area. The first insulating member is simultaneously bonded to the tail of the diaphragm on the side away from the winding center, the tail end face of the negative electrode sheet and at least part of the second insulating member.

9. The battery according to any one of claims 1 to 3, characterized in that The negative electrode sheet has a negative electrode sheet winding starting end, the winding starting end of the diaphragm is flush with the winding starting end of the negative electrode sheet, the innermost circle of the positive electrode sheet has a first positive electrode straight section, a first positive electrode bent section and a second positive electrode straight section, the end of the first positive electrode straight section away from the first positive electrode bent section is the winding starting end of the positive electrode sheet, the first positive electrode bent section is arranged opposite to the winding starting end of the negative electrode sheet, and along the third direction X, the winding starting end of the negative electrode sheet and the winding starting end of the positive electrode sheet extend in opposite directions.

10. The battery according to claim 9, characterized in that A third insulating member is provided on a surface of the first positive electrode bending section facing the winding center, and the third insulating member includes a second substrate layer and an adhesive layer, and the adhesive layer is provided at least on a surface of the second substrate layer facing the first positive electrode bending section; preferably, The adhesive layer is arranged on the second substrate layer at intervals to form a blank area on the second substrate layer. Along the winding direction of the positive electrode sheet, at least part of the blank area is arranged corresponding to the first positive electrode bending section. The area of ​​the third insulating member is S1, and the projected area of ​​the adhesive layer on the third insulating member is S2. S1 and S2 satisfy: 0.2≤S2 / S1≤0.8.

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