Battery

Abstract

The invention relates to the technical field of batteries, and discloses a battery, comprising: a housing having an accommodating space; the winding core is arranged in the accommodating space and is formed by sequentially laminating and winding a first pole piece, a diaphragm and a second pole piece, the first pole piece is provided with a first starting section close to the winding center and comprises a first winding starting end located at the first starting section, and the first starting section is provided with a first surface facing the winding center and a second surface deviating from the winding center; the additional parts comprise a first additional part, the first additional part is arranged on the first surface and / or the second surface, the first additional part extends out of a first winding starting end, and the part, exceeding the first winding starting end, of the first additional part is wound around the winding center by at least one circle; and based on the mass of the electrolyte, the mass content of the carboxylic ester organic solvent in the electrolyte is 5%-60%. The lithium separation problem is avoided, the cycle performance of the battery is improved, and the infiltration effect on the roll core is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to batteries. Background Art

[0002] The core is made of stacked and wound positive electrode sheets, separators and negative electrode sheets. After the core is wound, the ends of the electrode sheets are in a free state. The ends of the electrode sheets are prone to shrink in the opposite direction of winding, and the ends of the electrode sheets are also prone to rebound toward the hollow area of the core, which affects the cycle performance of the battery and makes the battery prone to safety problems such as lithium deposition. Summary of the Invention

[0003] In view of this, the present invention provides a winding core and a battery to solve the problems in the prior art that the cycle performance of the battery is affected and the battery is prone to safety problems such as lithium deposition.

[0004] The present invention provides a battery, comprising:

[0005] a housing having a receiving space;

[0006] a winding core disposed in the accommodation space and formed by sequentially stacking and winding a first pole piece, a diaphragm, and a second pole piece, wherein the first pole piece has a first starting section close to a winding center, the first pole piece includes a first winding starting end located in the first starting section, and the first starting section has a first surface facing the winding center and a second surface facing away from the winding center;

[0007] The additional member includes a first additional member, the first additional member is disposed on the first surface and / or the second surface, the first additional member extends beyond the first winding starting end, and a portion of the first additional member that exceeds the first winding starting end is wound around the winding center for at least one turn;

[0008] The electrolyte comprises a carboxylate organic solvent having a mass content of 5% to 60% based on the mass of the electrolyte, and the carboxylate organic solvent comprises at least one of ethyl acetate, ethyl propionate, methyl acetate, propyl acetate, methyl propionate, methyl butyrate and ethyl butyrate.

[0009] In an optional embodiment, the number of turns of the portion of the first additional member extending beyond the first winding starting end around the winding center is three to eight turns; and / or,

[0010] Along the winding direction, the length of the first additional member extending beyond the first winding starting end is L1, and the value range of L1 is 5 mm to 80 mm; and / or,

[0011] The first additional member is provided on both the first surface and the second surface; a portion of the first additional member provided on the first surface that extends beyond the first winding starting end is connected to a portion of the first additional member provided on the second surface that extends beyond the first winding starting end; and / or,

[0012] The additional component includes a substrate layer and / or an adhesive layer, and the adhesive layer is arranged on at least one side of the substrate layer; the substrate layer is a polymer layer, and the polymer layer includes at least one of polyethylene terephthalate, polyimide, polypropylene, polyethylene, and polyetheretherketone; or, the substrate layer is a metal layer, and the metal layer includes copper elements or aluminum elements; the adhesive layer includes at least one of acrylic glue, hot melt glue, organic silicone, and rubber.

[0013] In an optional embodiment, the first pole piece includes a first empty foil area and a first double-sided coating area sequentially connected by the first winding starting end, and the first additional part and the first double-sided coating area are partially overlapped in the winding direction.

[0014] In an optional embodiment, along the winding direction, the overlapping length of the first additional member and the first double-sided coating area is L2, and the value range of L2 is 0.5 mm to 5 mm; and / or,

[0015] The first pole piece has a first tail section away from the winding center, the first pole piece includes a first winding tail end located in the first tail section, and the first tail section has a third surface facing the winding center and a fourth surface facing away from the winding center;

[0016] The attachment further includes a second attachment, which is at least disposed on the third surface and extends beyond the first winding end.

[0017] In an optional embodiment, the second pole piece has a second starting section close to the winding center, the second pole piece includes a second winding starting end located in the second starting section, and the second starting section has a fifth surface facing the winding center and a sixth surface facing away from the winding center;

[0018] The additional member further includes a third additional member, which is disposed on the fifth surface and / or the sixth surface and extends out of the second winding starting end.

[0019] In an optional embodiment, the second pole piece includes a second empty foil area and a second double-sided coating area sequentially connected by the second winding starting end, and the third additional part and the second double-sided coating area are partially overlapped in the winding direction.

[0020] In an optional embodiment, along the winding direction, the overlapping length of the third additional member and the second double-sided coating area is L3, and the value range of L3 is 0.5mm to 5mm; and / or,

[0021] The second pole piece has a second tail section away from the winding center, the second pole piece includes a second winding tail end located in the second tail section, and the second tail section has a seventh surface facing the winding center and an eighth surface facing away from the winding center;

[0022] The attachment further includes a fourth attachment, which is disposed on the seventh surface and / or the eighth surface and extends out of the second winding end.

[0023] In an optional embodiment, the second pole piece further includes a third empty foil area connected to the second double-sided coated area, the second winding end is an end of the third empty foil area away from the second double-sided coated area along the winding direction, and the fourth additional member is partially overlapped with the second double-sided coated area;

[0024] The second pole piece further includes a second pole tab connected to the third empty foil area, and the fourth additional component is covered on the second pole tab.

[0025] In an optional embodiment, along the winding direction, the overlapping length of the fourth additional member and the second double-sided coating area is L4, and the value range of L4 is 0.5mm to 5mm; and / or,

[0026] The first pole piece further includes a first pole tab, and along the radial direction of the winding core, the first pole tab does not overlap with the fourth additional member; and / or,

[0027] The fourth additional member has a first end face and a second end face along the winding direction, the first end face and the winding center form a first connecting line, the second end face and the winding center form a second connecting line, the first connecting line and the second connecting line form an angle α, and the value of α ranges from 40° to 160°; and / or,

[0028] The radial projection of the portion of the third additional component located in the second double-sided coating area falls on the first double-sided coating area, and the radial projection of the first additional component located on the second surface falls on the third additional component; the radial projection of the portion of the fourth additional component located in the second double-sided coating area falls on the first double-sided coating area; the first electrode is a negative electrode, and the second electrode is a positive electrode; or,

[0029] The radial projection of the portion of the third additional component located in the second double-sided coating area falls on the first double-sided coating area, and the radial projection of the first additional component located on the second surface falls on the third additional component; the first pole piece also includes a first single-sided coating area and a fourth empty foil area sequentially connected to the first double-sided coating area along the winding direction, the first winding tail end is the end of the fourth empty foil area away from the first single-sided coating area along the winding direction, the radial projection of the portion of the fourth additional component located in the second double-sided coating area toward the winding center falls on the first double-sided coating area, and the radial projection of the portion of the fourth additional component located in the second double-sided coating area away from the winding center falls on the first single-sided coating area; the first pole piece is a negative pole piece, and the second pole piece is a positive pole piece; and / or,

[0030] The first electrode sheet includes a negative electrode active material layer, the negative electrode active material layer includes a silicon-carbon material, and the mass proportion of silicon in the negative electrode active material layer is 1.5% to 50%.

[0031] In an optional embodiment, the thickness of the substrate layer is t1, and the value range of t1 is 5 μm to 50 μm; and / or,

[0032] The thickness of the adhesive layer is t2, and the value range of t2 is 2 μm to 16 μm; and / or,

[0033] The thickness of the additional component is T, the first pole piece includes a first current collector and a first active layer disposed on at least one side of the first current collector, the thickness of the first active layer located on one side of the first current collector is H1, and the value range of T / H1 is 0.3 to 3.5; and / or,

[0034] The thickness of the additional component is T, the second pole piece includes a second current collector and a second active layer provided on at least one side of the second current collector, the thickness of the second active layer located on one side of the second current collector is H2, and the value range of T / H2 is 0.3 to 3.5; and / or,

[0035] The adhesive layer is provided on one side of the base material layer, and the adhesive layer is provided on the side of the base material layer facing the first starting section.

[0036] The technical solution of this application has the following advantages:

[0037] By setting the first additional part, the part of the first additional part that exceeds the first winding starting end of the first electrode can be wound at least one circle first at the beginning of winding, thereby effectively limiting and fixing the position of the first electrode on the winding needle, ensuring that the first electrode has a stable winding position, and then inserting the second electrode and winding it synchronously with the first electrode, which can improve the relative position accuracy of the first electrode and the second electrode. Moreover, after the winding is completed, the first additional part set for winding applies a pulling force to the first winding starting end of the first electrode to avoid the first winding starting end from shrinking along the winding direction due to the existence of the winding tension force, which can also improve the relative position accuracy of the first electrode and the second electrode, thereby avoiding the occurrence of lithium plating problems. At the same time, under the support of the first additional part, the first electrode is prevented from rebounding toward the hollow area of the winding core at the first winding starting end, so that the first electrode and the second electrode can be in close contact, avoiding the generation of abnormal gaps, thereby improving the interface stability between the first electrode and the second electrode, and improving the cycle performance of the battery. Furthermore, the use of an electrolyte containing a carboxylate organic solvent in the battery can reduce the viscosity of the electrolyte, prevent the first additional component from occupying the internal space of the core, resulting in a decrease in the electrolyte's infiltration speed and infiltration effect on the core, improve the infiltration effect on the core, and improve the battery cycle performance. In addition, the content of the carboxylate organic solvent in the electrolyte is controlled to ensure sufficient infiltration of the core while avoiding the battery containing too much carboxylate organic solvent, which increases the occurrence of side reactions such as gas production. On the other hand, excessive addition of carboxylate organic solvent will significantly reduce the dielectric constant of the electrolyte, reduce the ionic conductivity, and worsen the cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 This is a schematic structural diagram of a winding core according to an embodiment of the present invention;

[0040] Figure 2 for Figure 1 A partially enlarged schematic diagram of the center position of the winding core is shown;

[0041] Figure 3 This is a schematic structural diagram of another winding core according to an embodiment of the present invention;

[0042] Figure 4 This is a schematic structural diagram of a first pole piece according to an embodiment of the present invention;

[0043] Figure 5 This is a schematic structural diagram of another first pole piece according to an embodiment of the present invention;

[0044] Figure 6 for Figure 5 A schematic diagram of the dimensions of the first pole piece shown;

[0045] Figure 7 This is a schematic structural diagram of another first pole piece according to an embodiment of the present invention;

[0046] Figure 8 This is a schematic structural diagram of a second pole piece according to an embodiment of the present invention;

[0047] Figure 9 for Figure 8 A schematic diagram of the dimensions of the second pole piece shown;

[0048] Figure 10 A schematic structural diagram of an additional component according to an embodiment of the present invention;

[0049] Figure 11 A schematic diagram of the dimensions of the first active layer according to an embodiment of the present invention;

[0050] Figure 12 This is a schematic diagram of the dimensions of the second active layer according to an embodiment of the present invention;

[0051] Figure 13 This is a schematic structural diagram of a recessed portion provided on the first active layer according to an embodiment of the present invention;

[0052] Figure 14 Schematic diagram of the dimensions of the recessed portion according to an embodiment of the present invention.

[0053] Description of reference numerals:

[0054] 1. Winding core; 11. First pole piece; 111. First starting section; 1111. First surface; 1112. Second surface; 112. First current collector; 113. First active layer; 1131. Recess; 114. First double-sided coating area; 115. First hollow foil area; 116. First ending section; 1161. Third surface; 1162. Fourth surface; 117. First tab; 118. First single-sided coating area; 119. Fourth hollow foil area; 12. Separator; 13. Second pole piece; 131. Second starting section; 131 1. Fifth surface; 1312. Sixth surface; 132. Second current collector; 133. Second active layer; 134. Second double-sided coating area; 135. Second empty foil area; 136. Second finishing section; 1361. Seventh surface; 1362. Eighth surface; 137. Third empty foil area; 138. Second tab; 2. Attachments; 21. First attachment; 22. Second attachment; 23. Third attachment; 24. Fourth attachment; 241. First connecting line; 242. Second connecting line; 25. Base material layer; 26. Adhesive layer. DETAILED DESCRIPTION

[0055] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0056] The following combination Figures 1 to 14 , describing embodiments of the present invention.

[0057] According to an embodiment of the present invention, a battery is provided, comprising: a housing having a storage space; a winding core 1, disposed in the storage space and formed by stacking and winding a first electrode sheet 11, a separator 12, and a second electrode sheet 13 in sequence, wherein the first electrode sheet 11 has a first starting section 111 near a winding center, the first electrode sheet 11 includes a first winding starting end located in the first starting section 111, and the first starting section 111 has a first surface 1111 facing the winding center and a second surface 1112 facing away from the winding center; an attachment 2, comprising a first attachment 21. The first additional member 21 is arranged on the first surface 1111 and / or the second surface 1112, and the first additional member 21 extends beyond the first winding starting end, and the portion of the first additional member 21 exceeding the first winding starting end is wound around the winding center for at least one circle; the electrolyte, based on the mass of the electrolyte, the mass content of the carboxylic acid ester organic solvent in the electrolyte accounts for 5% to 60%, and the carboxylic acid ester organic solvent includes at least one of ethyl acetate, ethyl propionate, methyl acetate, propyl acetate, methyl propionate, methyl butyrate and ethyl butyrate.

[0058] In the battery of this embodiment, by providing the first additional member 21, the portion of the first additional member 21 that exceeds the first winding starting end of the first electrode piece 11 can be preferentially wound for at least one turn at the beginning of winding, thereby effectively limiting and fixing the position of the first electrode piece 11 on the winding needle, ensuring that the first electrode piece has a stable winding position, and then inserting the second electrode piece 13 and winding it synchronously with the first electrode piece 11, which can improve the relative position accuracy of the first electrode piece 11 and the second electrode piece 13. Moreover, after the winding is completed, the first winding start of the first electrode piece 11 is fixed by the first additional member 21 provided for winding. A pulling force is applied at the starting end to prevent the starting end of the first winding from shrinking along the winding direction due to the existence of the winding tension force. It can also improve the relative position accuracy of the first electrode 11 and the second electrode 13, thereby avoiding the occurrence of lithium plating problems. At the same time, under the support of the first additional part 21, the first electrode 11 is prevented from rebounding toward the hollow area of the core 1 at the starting end of the first winding, so that the first electrode 11 and the second electrode 13 can be in close contact, avoiding the generation of abnormal gaps, thereby improving the interface stability between the first electrode 11 and the second electrode 13 and improving the cycle performance of the battery. Furthermore, the use of an electrolyte containing a carboxylate organic solvent in the battery can reduce the viscosity of the electrolyte, prevent the first additional component from occupying the internal space of the core, resulting in a decrease in the infiltration speed and infiltration effect of the electrolyte on the core, improve the infiltration effect on the core 1, and improve the battery cycle performance. In addition, the content of the carboxylate organic solvent in the electrolyte is controlled to ensure that the core 1 is fully infiltrated while avoiding the battery containing too much carboxylate organic solvent to increase the occurrence of side reactions such as gas production. On the other hand, excessive addition of carboxylate organic solvent will significantly reduce the dielectric constant of the electrolyte, reduce the ionic conductivity, and worsen the cycle.

[0059] It is worth noting that in the related art, a winding needle is used to wind the positive electrode sheet, the negative electrode sheet and the separator 12 to form a winding core 1. At the beginning of winding, the starting ends of the positive electrode sheet and the negative electrode sheet are respectively inserted into the winding needle or near the winding needle. Since the starting ends of the positive electrode sheet and the negative electrode sheet are in a free state, and in order to improve production efficiency, the winding needle is usually in a high-speed winding state, which will cause the positions of the positive electrode sheet and the negative electrode sheet to fluctuate greatly. After winding, it is easy for the active layer of the positive electrode sheet to exceed the active layer of the negative electrode sheet, resulting in the lithium ions released from the part of the active layer of the positive electrode sheet that exceeds the active layer of the negative electrode sheet when the battery is charged. There is no corresponding negative electrode active material to receive the lithium ions, and the lithium ions will migrate to the edge of the active layer of the negative electrode sheet, resulting in the accumulation of lithium ions at the edge of the active layer of the negative electrode sheet, resulting in the occurrence of lithium plating problems.

[0060] In the present embodiment, by providing a first additional part 21 extending from the first winding starting end at the first starting section 111 of the first pole piece 11, the first pole piece 11 can be pre-fixed at the beginning of winding, thereby avoiding position fluctuation of the first pole piece 11, reducing the risk of misalignment between the first pole piece 11 and the second pole piece 13, improving the matching accuracy of the first pole piece 11 and the second pole piece 13, and avoiding lithium plating problems in the battery.

[0061] In addition, in the related art, after the winding of the core 1 is completed and the winding needle is withdrawn, the positive and negative electrode sheets are supported only by the innermost circle of the pre-rolled diaphragm 12 at the center of the winding. Since the diaphragm 12 is relatively thin and soft in texture, it cannot effectively support the electrode sheets, causing the starting end of the winding of the electrode sheet to easily rebound toward the hollow area of the core 1, making the gap between the positive and negative electrode sheets in the area near the starting end of the winding too large, which is not conducive to the lithium ion transmission in this area, thereby affecting the cycle performance of the battery.

[0062] Furthermore, the battery in this application may be a button cell battery. In this case, the battery housing may be a metal housing, such as a steel housing. The metal housing is relatively hard, and when the battery expands, the expansion stress acts inward, squeezing the winding core. This deteriorates the interface stability between the first electrode sheet 11 and the second electrode sheet 13 on the inner ring of the winding core.

[0063] In the present embodiment, a first additional part 21 extending from the first winding starting end is provided in the first starting section 111 of the first electrode sheet 11, and the portion of the first additional part 21 extending beyond the first winding starting end is wound at least one circle around the winding center. Therefore, when the winding of the core 1 is completed and the needle is withdrawn, the first additional part 21 provided for winding can effectively support the first electrode sheet 11 and the second electrode sheet 13 to avoid electrode rebound, so that the first electrode sheet 11 and the second electrode sheet 13 are in close contact and abnormal gaps are avoided, thereby improving the interface stability between the first electrode sheet 11 and the second electrode sheet 13 and improving the cycle performance of the battery.

[0064] It is worth noting that in the related art, a center hole is formed in the center of the core 1 after the winding is completed, and the electrolyte infiltrates the core 1 through the center hole. In this embodiment, the provision of the first additional component 21 occupies part of the space of the center hole, affecting the infiltration effect of the electrolyte on the core 1. Therefore, the battery of this embodiment uses an electrolyte containing a carboxylic acid ester organic solvent to reduce the viscosity of the electrolyte, improve the wettability of the electrolyte, and enhance the battery cycle performance. However, if the content of the carboxylic acid ester organic solvent in the electrolyte is too high, it will increase the side reactions such as gas production in the battery electrolyte. On the other hand, excessive addition of the carboxylic acid ester organic solvent will significantly reduce the dielectric constant of the electrolyte, reduce the ionic conductivity, and worsen the battery cycle performance.

[0065] Optionally, the mass content of the carboxylic acid ester organic solvent in the electrolyte is any value of 5%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or a value between any two values.

[0066] It is understood that the first electrode 11 and the second electrode 13 are respectively a positive electrode and a negative electrode. Specifically, when the first electrode 11 is a negative electrode, the second electrode 13 is a positive electrode; when the first electrode 11 is a positive electrode, the second electrode 13 is a negative electrode.

[0067] Furthermore, in one embodiment, the number of turns of the portion of the first additional part 21 that extends beyond the first winding starting end around the winding center is three to eight turns. This arrangement can prevent the winding number from being too small, the additional part from being insufficiently pre-wound, and the position of the additional part and the pole piece connected thereto from not yet reaching a stable state, which can easily lead to abnormal misalignment of the first pole piece and the second pole piece during winding, resulting in the edge of the positive pole piece exceeding the edge of the negative pole piece, thereby causing lithium deposition in the battery after charging. At the same time, it can also avoid excessive winding turns, which will occupy more core space and be detrimental to the improvement of battery energy density and cycle performance. That is, a reasonable setting of the winding number of the first additional part 21 can improve the winding misalignment problem between the first pole piece 11 and the second pole piece 13, and at the same time, avoid the influence of excessive winding turns on the energy density and cycle performance of the battery.

[0068] It is worth noting that if the number of winding turns is too small, the effect of restricting and fixing the position of the first pole piece 11 at the beginning of winding is poor, and there is still a risk of misalignment between the first pole piece 11 and the second pole piece 13, which may cause lithium deposition problems. In addition, after the winding needle is withdrawn, the first additional part 21 is less effective in supporting the first pole piece 11 and the second pole piece 13 to prevent rebound. There is also a certain risk of a large gap between the first pole piece 11 and the second pole piece 13, affecting the battery's cycle performance. If the number of winding turns is too large, it will occupy more space in the winding core 1, which is not conducive to improving the battery's energy density and cycle performance.

[0069] Optionally, the number of winding turns is any value among 3 turns, 3.5 turns, 4 turns, 4.5 turns, 5 turns, 5.5 turns, 6 turns, 6.5 turns, 7 turns, 7.5 turns, 8 turns, or a value between any two values.

[0070] Furthermore, in one embodiment, Figure 6As shown, along the winding direction, the length of the first additional member 21 extending beyond the starting end of the first winding is L1, and the value of L1 ranges from 5mm to 80mm. This configuration can reduce the risk of abnormal misalignment of the first and second pole pieces during winding, while also avoiding any impact on the battery's energy density. Furthermore, L1 can be adapted to winding cores of different sizes, meeting the needs of various winding cores.

[0071] It is worth noting that if the value of L1 is too small, the position of the first pole piece 11 will be poorly restricted and fixed due to insufficient pre-winding of the additional part at the beginning of winding, and there is still a risk of misalignment between the first pole piece 11 and the second pole piece 13, which may cause lithium plating problems. Moreover, after the winding needle is withdrawn, the first additional part 21 will not be able to support the first pole piece 11 and the second pole piece 13 to prevent rebound. There is also a certain risk of a large gap between the first pole piece 11 and the second pole piece 13, which may affect the cycle performance of the battery. If the value of L1 is too large, it will occupy more space in the winding core 1, which is not conducive to improving the energy density of the battery.

[0072] Optionally, the value of L1 is any value of 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, or a value between any two values.

[0073] Furthermore, in one embodiment, Figures 4 to 7 As shown, the first surface 1111 and the second surface 1112 are both provided with a first additional part 21; the portion of the first additional part 21 provided on the first surface 1111 that extends beyond the starting end of the first winding is connected to the portion of the first additional part 21 provided on the second surface 1112 that extends beyond the starting end of the first winding. Such a configuration makes the force on the first starting section 111 more uniform, and avoids the first pole piece 11 from bending in the direction of greater force when the material strip is cut at the position of the first additional part 21 during the winding process, thereby avoiding the problem of short-circuiting the positive and negative poles of the core 1 due to the folding of the first pole piece 11, and improving the safety of the battery; the pole piece will undergo thickness expansion changes during the charging and discharging process of the battery. By arranging the first additional part 21 on the first surface 1111 and the second surface 1112 of the first starting section 111, the stress on the first pole piece 11 when expanding can be made more uniform, reducing the degree of expansion of the battery; and it can improve the structural strength of the first starting section 111 and prevent the two first additional parts 21 from sliding against each other. Moreover, because the first additional part is provided with two layers, it can have higher structural strength, thereby further enhancing the limiting effect on the first pole piece and the supporting effect on the first starting section 111, further avoiding the risk of misalignment between the first pole piece and the second pole piece and the rebound of the first starting section toward the hollow area of the core.

[0074] Of course, in other alternative embodiments, the first additional component 21 may be provided only on the first surface 1111 , or the first additional component 21 may be provided only on the second surface 1112 .

[0075] In one embodiment, Figures 4 to 7 As shown, the first pole piece 11 includes a first empty foil area 115 and a first double-sided coating area 114 sequentially connected from the first winding starting end, and the first additional member 21 and the first double-sided coating area 114 are partially overlapped in the winding direction.

[0076] It is worth noting that the first additional member 21 can be a structure with an adhesive layer 26 (for example, having only an adhesive layer, or having both a metal layer and an adhesive layer). The first additional member 21 is bonded to the first hollow foil area 115 and the first double-sided coated area 114 using the adhesive layer 26, thereby improving the firmness of the first additional member 21. Of course, the first additional member 21 may also not have the adhesive layer 26. For example, the first additional member 21 may be a metal layer. In this case, the first additional member 21 and the first hollow foil area 115 may be connected by welding or other means, and the first additional member 21 may not overlap with the first double-sided coated area 114.

[0077] Specifically, in one embodiment, Figure 6 As shown, along the winding direction, the overlap length between the first attachment member 21 and the first double-sided coated area 114 is L2, and the value of L2 ranges from 0.5mm to 5mm. This arrangement ensures the connection stability between the first attachment member 21 and the first double-sided coated area 114 while avoiding any impact on the battery's energy density and preventing the occurrence of lithium plating.

[0078] It is worth noting that if the value of L2 is too small, the mating area between the first attachment member 21 and the first double-sided coating area 114 is too small, making it difficult to achieve a reliable connection between the first attachment member 21 and the first double-sided coating area 114. If the value of L2 is too large, the first attachment member 21 covers too much of the first double-sided coating area 114, affecting the release or reception of lithium ions, affecting the energy density of the battery, and easily causing lithium plating problems.

[0079] It should be further explained that if the first additional component 21 covers the first double-sided coating area 114 too much, when the first electrode 11 is a positive electrode, the first additional component 21 limits the escape of lithium ions, affecting current transmission and thus affecting the energy density of the battery; when the first electrode 11 is a negative electrode, the first additional component 21 limits the reception of lithium ions, and the lithium ions migrate to the junction of the first double-sided coating area 114 and the first additional component 21, resulting in the accumulation of lithium ions and causing lithium plating problems.

[0080] Optionally, the value of L2 is any value among 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, or a value between any two values.

[0081] In one embodiment, Figure 5 As shown, the first pole piece 11 has a first end section 116 away from the winding center. The first pole piece 11 includes a first winding end located in the first end section 116. The first winding end section 116 has a third surface 1161 facing the winding center and a fourth surface 1162 facing away from the winding center. The attachment 2 also includes a second attachment 22, which is disposed at least on the third surface 1161 and extends beyond the first winding end. This arrangement prevents burrs generated by cutting at the first winding end from puncturing the separator 12, thereby improving battery safety.

[0082] It is worth noting that the second additional component 22 can be provided only on the third surface 1161, or can be provided on both the third surface 1161 and the fourth surface 1162. When the second additional component 22 is provided on both the third surface 1161 and the fourth surface 1162, the portion of the second additional component 22 provided on the third surface 1161 that extends beyond the first winding end is connected to the portion of the second additional component 22 provided on the fourth surface 1162 that extends beyond the first winding end. This arrangement can enhance the structural strength of the first electrode 11 at the winding end, enhance the tensile strength of the second additional component 22 to strengthen the restriction on the inner ring electrode, thereby preventing excessive outward expansion of the battery. In addition, the two layers of the second additional component 22 are connected to cover the first winding end, preventing the first winding end from moving when the battery is subjected to force and contacting the second electrode 13 or the outer shell, causing a short circuit.

[0083] In one embodiment, Figure 8 As shown, the second pole piece 13 has a second starting section 131 near the winding center. The second pole piece 13 includes a second winding starting end located in the second starting section 131. The second starting section 131 has a fifth surface 1311 facing the winding center and a sixth surface 1312 facing away from the winding center. The attachment 2 also includes a third attachment 23, which is disposed on the fifth surface 1311 and / or the sixth surface 1312 and extends beyond the second winding starting end. This arrangement prevents burrs generated by cutting at the second winding starting end from puncturing the separator 12, thereby improving battery safety.

[0084] It is worth noting that the third additional member 23 can be provided only on the fifth surface 1311, only on the sixth surface 1312, or on both the fifth and sixth surfaces 1311, 1312. Furthermore, when the third additional member 23 is provided on both the fifth and sixth surfaces 1311, 1312, the portion of the third additional member 23 provided on the fifth surface 1311 that extends beyond the second winding starting end is connected to the portion of the third additional member 23 provided on the sixth surface 1312 that extends beyond the second winding starting end.

[0085] Furthermore, in one embodiment, Figure 8 As shown, the second pole piece 13 includes a second empty foil area 135 and a second double-sided coating area 134 sequentially connected from the second winding starting end, and the third additional member 23 and the second double-sided coating area 134 are partially overlapped in the winding direction.

[0086] It is worth noting that the third additional member 23 can be a structure with an adhesive layer 26 (for example, having only an adhesive layer, or having both a metal layer and an adhesive layer). The third additional member 23 is bonded to the second hollow foil area 135 and the second double-sided coated area 134 using the adhesive layer 26, thereby improving the firmness of the third additional member 23. Of course, the third additional member 23 may also not have an adhesive layer 26. For example, the third additional member 23 may be a metal layer. In this case, the third additional member 23 and the second hollow foil area 135 can be connected by welding or other means, and the third additional member 23 may not overlap with the second double-sided coated area 134.

[0087] Specifically, in one embodiment, Figure 9 As shown, along the winding direction, the overlapping length L3 between the third attachment member 23 and the second double-sided coated area 134 is 0.5 mm to 5 mm. This arrangement ensures the connection stability between the third attachment member 23 and the second double-sided coated area 134 while minimizing the impact on the battery's energy density and preventing lithium plating.

[0088] It is worth noting that if the value of L3 is too small, the mating area between the third attachment member 23 and the second double-sided coating area 134 is too small, making it difficult to achieve a reliable connection between the third attachment member 23 and the second double-sided coating area 134. If the value of L3 is too large, the coverage area of the second double-sided coating area 134 by the third attachment member 23 is too large, which affects the release or reception of lithium ions, affects the energy density of the battery, and is prone to lithium plating.

[0089] It should be further explained that if the third additional component 23 covers the second double-sided coating area 134 too much, when the second electrode 13 is a positive electrode, the third additional component 23 limits the escape of lithium ions, affecting current transmission and thus affecting the energy density of the battery; when the second electrode 13 is a negative electrode, the third additional component 23 limits the reception of lithium ions, and the lithium ions migrate to the intersection of the second double-sided coating area 134 and the third additional component 23, resulting in lithium ion accumulation and causing lithium plating problems.

[0090] Optionally, the value of L3 is any value among 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, or a value between any two values.

[0091] In one embodiment, Figure 8 As shown, the second pole piece 13 has a second end section 136 located away from the winding center. The second pole piece 13 includes a second winding end located in the second end section 136. The second end section 136 has a seventh surface 1361 facing the winding center and an eighth surface 1362 facing away from the winding center. The attachment 2 also includes a fourth attachment 24, which is disposed on the seventh surface 1361 and / or the eighth surface 1362 and extends beyond the second winding end. This arrangement prevents burrs from cutting the second winding end from puncturing the separator 12, thereby improving battery safety.

[0092] It is worth noting that the fourth additional member 24 can be provided only on the seventh surface 1361, only on the eighth surface 1362, or on both the seventh surface 1361 and the eighth surface 1362. When the fourth additional member 24 is provided on both the seventh surface 1361 and the eighth surface 1362, the portion of the fourth additional member 24 provided on the seventh surface 1361 that extends beyond the second winding end is interconnected with the portion of the fourth additional member 24 provided on the eighth surface 1362 that extends beyond the second winding end. This arrangement can enhance the structural strength of the second electrode sheet 13 at the winding end, increase the tensile strength of the fourth additional member 24 to strengthen the restriction on the inner electrode sheet and thus prevent excessive outward expansion of the battery. Furthermore, the two layers of the fourth additional member 24 are connected to cover the second winding end, preventing the second winding end from moving when the battery is subjected to force and contacting the first electrode sheet 11 or the outer shell, causing a short circuit.

[0093] In one embodiment, Figure 8As shown, the second pole piece 13 also includes a third hollow foil area 137 connected to the second double-sided coated area 134. The second winding end is the end of the third hollow foil area 137 away from the second double-sided coated area 134 along the winding direction. The fourth attachment 24 is partially overlapped with the second double-sided coated area 134. The second pole piece 13 also includes a second pole tab 138 connected to the third hollow foil area 137. The fourth attachment 24 covers the second pole tab 138. In this arrangement, the fourth attachment 24 can isolate and protect the burrs at the second winding end and cover the position of the second pole tab 138, thereby achieving a protective effect for the second pole tab 138.

[0094] Of course, in other alternative embodiments, the fourth additional component 24 may not cover the second tab 138 , but may use another tab protection tape to additionally cover it.

[0095] Specifically, in one embodiment, Figure 9 As shown, along the winding direction, the overlapping length L4 between the fourth additional member 24 and the second double-sided coating area 134 is 0.5 mm to 5 mm. This configuration improves battery safety while minimizing the impact on battery energy density and preventing lithium plating.

[0096] It is worth noting that if the value of L4 is too small, the matching area between the fourth additional component 24 and the second double-sided coating area 134 is too small, making it difficult to achieve a reliable connection between the fourth additional component 24 and the second double-sided coating area 134. It is easy for the exposed current collector between the second pole piece 138 and the active layer of the second pole piece 13 to not be completely covered. When the diaphragm 12 between the first pole piece 11 and the second pole piece 13 is abnormal (such as broken, folded, etc.), there is a risk that the active layer of the first pole piece 11 will come into contact with the current collector of the second pole piece 13, which will cause the battery to release a large amount of energy in a very short time, causing safety risks such as battery fire and explosion. If the value of L4 is too large, the coverage area of the second double-sided coating area 134 by the fourth additional component 24 is too large, affecting the release or reception of lithium ions, affecting the energy density of the battery, and easily causing lithium plating problems.

[0097] It should be further explained that if the fourth additional component 24 covers the second double-sided coating area 134 too much, when the second electrode 13 is a positive electrode, the fourth additional component 24 limits the escape of lithium ions, affecting current transmission and thus affecting the energy density of the battery; when the second electrode 13 is a negative electrode, the fourth additional component 24 limits the reception of lithium ions, and the lithium ions migrate to the intersection of the second double-sided coating area 134 and the fourth additional component 24, resulting in lithium ion accumulation and causing lithium plating problems.

[0098] Optionally, the value of L4 is any value among 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, or a value between any two values.

[0099] In one embodiment, Figure 1 and Figure 3 As shown, the first pole piece 11 further includes a first pole tab 117. Along the radial direction of the winding core 1, the first pole tab 117 does not overlap with the fourth additional member 24. This arrangement prevents the first pole tab 117 and the second pole tab 138 from overlapping and causing thickness overlap, thereby reducing the radius of the winding core 1 and improving the battery energy density.

[0100] In one embodiment, Figure 1 As shown, the fourth attachment member 24 has a first end face and a second end face along the winding direction. The first end face forms a first connecting line 241 with the winding center, and the second end face forms a second connecting line 242 with the winding center. The first connecting line 241 and the second connecting line 242 form an angle α, with a value of α ranging from 40° to 160°. This arrangement ensures that the fourth attachment member 24 effectively covers the third empty foil area 137 and the second tab 138 while reducing the risk of interference with the outer shell when the winding core 1 is assembled into the shell.

[0101] It is worth noting that if the value of α is too small, the coverage of the fourth additional member 24 is too limited, failing to effectively cover the third hollow foil area 137 and the second tab 138. This can easily expose burrs at the end of the second winding and puncture the separator 12. There is also a risk of contact between the active layer of the first electrode sheet 11 and the current collector of the second electrode sheet 13, affecting the safety performance of the battery. If the value of α is too large, the coverage of the fourth additional member 24 is too large, resulting in an excessively large overall diameter of the winding core 1, which can easily interfere with the outer shell during assembly.

[0102] Optionally, the value of α is any value among 40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, or a value between any two values.

[0103] Taking the first electrode 11 as a negative electrode and the second electrode 13 as a positive electrode as an example, the arrangement of each additional component 2 is described.

[0104] In one embodiment, Figure 2As shown, the radial projection of the portion of the third additional member 23 located in the second double-sided coating area 134 falls on the first double-sided coating area 114, and the radial projection of the first additional member 21 located on the second surface 1112 falls on the third additional member 23. That is, along the winding direction, the third additional member 23 extends beyond the first additional member 21 in a direction away from the starting end of the second winding. Therefore, lithium ions released from the active layer of the second electrode sheet 13 (positive electrode sheet) are all received by the corresponding active layer of the first electrode sheet 11 (negative electrode sheet), preventing the occurrence of lithium plating.

[0105] In one embodiment, the radial projection of the portion of the fourth additional component 24 located in the second double-sided coating area 134 falls on the first double-sided coating area 114. That is, the radial projection of the fourth additional component 24 toward the winding center and the projection away from the winding center are both located on the first double-sided coating area 114. At this time, the first pole piece 11 also includes a fourth empty foil area 119 connected to the first double-sided coating area 114 along the winding direction, and the first winding end is the end of the fourth empty foil area 119 away from the first double-sided coating area 114 along the winding direction. With such a configuration, the lithium ions released from the active layer of the second pole piece 13 (positive pole piece) can be received by the corresponding active layer of the first pole piece 11 (negative pole piece), thereby avoiding the occurrence of lithium plating problems.

[0106] As an alternative embodiment, Figure 3 As shown, the first electrode 11 includes a first single-sided coating area 118 and a fourth empty foil area 119 that are sequentially connected to the first double-sided coating area 114 along the winding direction. The first winding end is the end of the fourth empty foil area 119 away from the first single-sided coating area 118 along the winding direction. The projection of the portion of the fourth additional member 24 located in the second double-sided coating area 134 radially toward the winding center falls on the first double-sided coating area 114, and the projection of the portion of the fourth additional member 24 located in the second double-sided coating area 134 radially away from the winding center falls on the first single-sided coating area 118. It can be understood that the active layer of the first single-sided coating area 118 is provided on the side of the first electrode 11 facing the winding center. This arrangement enables the lithium ions released from the active layer of the second electrode 13 (positive electrode) to be received by the corresponding active layer of the first electrode 11 (negative electrode), avoiding the occurrence of lithium plating problems.

[0107] Furthermore, in one embodiment, the first electrode 11 includes a negative electrode active material layer, which includes a silicon-carbon material, and the silicon element accounts for 1.5% to 50% by weight of the negative electrode active material layer. This configuration ensures the energy density of the battery while preventing lithium plating.

[0108] It is worth noting that if the mass percentage of silicon in the negative electrode active material layer is too small, the battery's energy density will be low. If the mass percentage of silicon in the negative electrode active material layer is too large, the thickness of the negative electrode sheet will expand excessively during charge and discharge, resulting in a large thickness difference between the negative electrode sheet and the additional component 2. This thickness difference is likely to occur at the junction of the negative electrode active layer and the additional component 2, leading to lithium deposition near this junction, thus affecting battery safety.

[0109] Optionally, the mass proportion of silicon in the negative electrode active material layer is any value of 1.5%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or a value between any two values.

[0110] In one embodiment, the additional component 2 includes a substrate layer 25 and / or an adhesive layer 26. That is, the additional component 2 may be only the substrate layer 25, only the adhesive layer 26, or both the substrate layer 25 and the adhesive layer 26.

[0111] Further, such as Figure 10 As shown, when both the base material layer 25 and the adhesive layer 26 are provided, the adhesive layer 26 is provided on at least one side of the base material layer 25 .

[0112] Specifically, such as Figure 10 As shown, the adhesive layer 26 can be provided on only one side of the substrate layer 25. In this case, taking the first additional component 21 as an example, the adhesive layer 26 is provided on the side of the substrate layer 25 facing the first starting section 111. It can be understood that when the first additional component 21 is provided on the first surface 1111, the adhesive layer 26 is bonded to the first surface 1111, and the substrate layer 25 is located on the side of the adhesive layer 26 away from the first surface 1111. Of course, the second additional component 22, the third additional component 23, and the fourth additional component 24 can also be provided with the adhesive layer 26 on only one side of the substrate layer 25, so as to bond to the corresponding surface. This arrangement prevents the additional component 2 from adhering to the diaphragm 12, thereby preventing wrinkling and misalignment of the diaphragm 12, and further preventing safety issues caused by a short circuit between the first and second electrode sheets 11 and 13.

[0113] Of course, the adhesive layer 26 may be provided on both opposite sides of the base material layer 25. Specifically, the adhesive layer 26 may be provided according to actual needs.

[0114] Specifically, the substrate layer 25 may be a polymer layer, and the polymer layer includes at least one of polyethylene terephthalate (PET), polyimide (PI), polypropylene (PP), polyethylene (PE), and polyetheretherketone (PEEK).

[0115] As an alternative embodiment, the base material layer 25 may also be a metal layer including copper or aluminum, for example, copper foil or aluminum foil.

[0116] Specifically, the adhesive layer 26 includes at least one of acrylic adhesive, hot melt adhesive, organic silicone, and rubber.

[0117] In one embodiment, Figure 10 As shown, the thickness of the substrate layer 25 is t1, and the value range of t1 is 5 μm to 50 μm. This configuration ensures the structural strength of the attachment 2 while avoiding affecting the energy density of the battery.

[0118] It is worth noting that if the value of t1 is too small, the structural strength of the attachment 2 is low, resulting in poor support of the attachment 2 at the starting end to prevent rebound and poor protection of the starting and ending ends of the electrode. If the value of t1 is too large, the attachment 2 takes up too much space, affecting the energy density of the battery.

[0119] Optionally, the value of t1 is any value among 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, or a value between any two values.

[0120] In one embodiment, Figure 10 As shown, the thickness of the adhesive layer 26 is t2, and the value range of t2 is 2 μm to 16 μm. This configuration ensures the bonding stability between the attachment 2 and the electrode while avoiding affecting the energy density of the battery.

[0121] It is worth noting that if the value of t2 is too small, the attachment 2 cannot be stably bonded to the electrode, and there is a risk of the attachment 2 detaching from the electrode, which in turn affects the safety performance of the battery. If the value of t2 is too large, the attachment 2 takes up too much space, affecting the energy density of the battery.

[0122] Optionally, the value of t2 is any value of 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, or a value between any two values.

[0123] In one embodiment, Figure 10 and Figure 11 As shown, the thickness of the additional component 2 is T, the first pole piece 11 includes a first current collector 112 and a first active layer 113 disposed on at least one side of the first current collector 112, the thickness of the first active layer 113 located on one side of the first current collector 112 is H1, and the value range of T / H1 is 0.3 to 3.5. Figure 10 and Figure 12As shown, the second pole piece 13 includes a second current collector 132 and a second active layer 133 disposed on at least one side of the second current collector 132. The second active layer 133 on one side of the second current collector 132 has a thickness H2, and the ratio T / H2 ranges from 0.3 to 3.5. This arrangement reduces the gaps between the different winding layers of the winding core 1 while also minimizing the expansion of the winding core 1.

[0124] It is worth noting that if the value of T is too small or too large, the thickness difference between the additional part 2 and the active layer after it is set on the empty foil area will be too large, resulting in an excessively large gap between different layers of the winding core 1, a poor restrictive effect on the electrode, and a greater degree of expansion of the electrode.

[0125] Optionally, the values of T / H1 and T / H2 are any value among 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.5, 2, 2.5, 3, 3.5, or a value between any two values.

[0126] It should be noted that when the additional component 2 is only the base material layer 25, T is the thickness of the base material layer 25; when the additional component 2 is only the adhesive layer 26, T is the thickness of the adhesive layer 26; Figure 10 As shown, when the additional component 2 has both a base material layer 25 and an adhesive layer 26 , T is the sum of the thickness of the base material layer 25 and the thickness of the adhesive layer 26 .

[0127] It is worth noting that, for the first pole piece 11, the first active layer 113 is not provided on the two opposite sides of the portion of the first current collector 112 corresponding to the first empty foil area 115, the first active layer 113 is provided on the two opposite sides of the portion of the first current collector 112 corresponding to the first double-sided coating area 114, the first active layer 113 is provided on one side of the portion of the first current collector 112 corresponding to the first single-sided coating area 118, and the first active layer 113 is not provided on the other side, and the first active layer 113 is not provided on the two opposite sides of the portion of the first current collector 112 corresponding to the fourth empty foil area 119.

[0128] It is worth noting that, for the second pole piece 13, the second active layer 133 is not provided on the two opposite sides of the portion of the second current collector 132 corresponding to the second empty foil area 135, the second active layer 133 is provided on the two opposite sides of the portion of the second current collector 132 corresponding to the second double-sided coating area 134, and the second active layer 133 is not provided on the two opposite sides of the portion of the second current collector 132 corresponding to the third empty foil area 137.

[0129] In one embodiment, the elastic modulus of the attachment 2 ranges from 1.5 GPa to 10 GPa. This configuration, on the one hand, can ensure that during winding, the pulling force generated by the winding needle is too large, which may cause the attachment to break, thereby failing to improve the relative position accuracy of the first and second electrode sheets during winding, thereby avoiding the occurrence of lithium deposition problems. On the other hand, it can absorb the expansion force of the core 1 while ensuring the molding effect of the core 1 for easy shell insertion.

[0130] It is worth noting that if the elastic modulus of the attachment 2 is too small, the attachment 2 is prone to breakage during winding, resulting in poor structural stability of the core 1, affecting the final molding effect of the core 1 and making it difficult to assemble with the outer shell. Moreover, during subsequent cycles, after the core expands, it squeezes the attachment 2, causing it to easily deform, thereby affecting the flatness of the core's internal interface, exacerbating lithium deposition or worsening the cycle. If the elastic modulus of the attachment 2 is too large, it cannot absorb and buffer the expansion force of the core 1, resulting in a large degree of battery expansion.

[0131] Optionally, the elastic modulus of the accessory 2 is any value of 1.5 GPa, 2 GPa, 2.5 GPa, 3 GPa, 3.5 GPa, 4 GPa, 4.5 GPa, 5 GPa, 5.5 GPa, 6 GPa, 6.5 GPa, 7 GPa, 7.5 GPa, 8 GPa, 8.5 GPa, 9 GPa, 9.5 GPa, 10 GPa, or a value between any two values.

[0132] In one embodiment, the tensile strength of the additional component 2 is not less than 10 MPa. This configuration prevents the additional component 2 from being severely deformed or even broken during the winding process or when subjected to expansion force, thereby ensuring the safety of the winding core 1.

[0133] Optionally, the tensile strength of the attachment 2 is any value among 10MPa, 20MPa, 30MPa, 40MPa, 50MPa, 60MPa, 70MPa, 80MPa, 90MPa, 100MPa, or a value between any two values. Of course, it can also be a value greater than 100MPa.

[0134] In one embodiment, the elongation of the attachment 2 ranges from 10% to 400%. This configuration reduces the risk of deformation of the pole piece connected to the attachment 2 and prevents the attachment 2 from being severely deformed or even broken during the winding process or when subjected to expansion force.

[0135] It is worth noting that if the elongation of the attachment 2 is too low, the electrode connected to the attachment 2 may be easily deformed during the winding process or when subjected to expansion forces, causing the electrode to curl and wrinkle, which may easily lead to lithium deposition problems. If the elongation of the attachment 2 is too high, the tensile strength and fatigue resistance of the attachment 2 will be low, and the attachment 2 may be severely deformed or even broken during the winding process or when subjected to expansion forces, affecting the safety performance of the battery.

[0136] Optionally, the elongation of the accessory 2 is any value of 10%, 25%, 50%, 75%, 100%, 125%, 150%, 175%, 200%, 225%, 250%, 275%, 300%, 325%, 350%, 375%, 400%, or a value between any two values.

[0137] In one embodiment, Figure 13 and Figure 14 As shown, the first electrode sheet 11 is a negative electrode sheet, and the first active layer 113 is recessed on one side away from the first current collector 112 to form a recess 1131. With this arrangement, when the battery is charging, the active layers on both sides of the recess 1131 can expand toward the recess 1131, thereby reducing the expansion of the negative electrode sheet along the thickness direction. At the same time, the presence of the recess can also improve the infiltration rate and effect of the electrolyte on the first electrode sheet, thereby improving the cycle performance of the battery.

[0138] Further, such as Figure 14 As shown, along the thickness direction of the first pole piece 11 (ie, the radial direction of the winding core 1 ), the recessed depth of the recess 1131 is d, and the value range of d is 5 μm to 40 μm.

[0139] Optionally, the value of d is any value among 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, or a value between any two values.

[0140] Further, such as Figure 14 As shown, the opening width of the recess 1131 along the length direction (ie, the winding direction) of the first pole piece 11 is w, and the value range of w is 20 μm to 200 μm.

[0141] Optionally, the value of w is any value of 20μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm, or a value between any two values.

[0142] Further, such as Figure 14 As shown, a plurality of recesses 1131 are arranged at intervals along the length direction (ie, the winding direction) of the first pole piece 11 , and the distance between adjacent recesses 1131 is l, and the value range of l is 0.5 mm to 5 mm.

[0143] Optionally, the value of l is any value among 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, or a value between any two values.

[0144] The following describes the battery of the present application in detail through specific examples. The specific differences between the following batteries are shown in Table 1.

[0145] Battery preparation process:

[0146] Step 1: Lithium cobalt oxide, a conductive carbon material (a mixture of conductive carbon black and carbon nanotubes), and a binder, PVDF, are mixed in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 98.2:1:0.8. The mixture is stirred continuously in a blender to form a uniform positive electrode active slurry. The positive electrode active slurry is then coated on the surface of aluminum foil, baked, rolled, and slit to produce the positive electrode sheet.

[0147] Step 2: Graphite and silicon-carbon composite, conductive carbon black (SuperP), styrene-butadiene rubber, and carboxymethyl cellulose are mixed in deionized water at a weight ratio of 95:0.5:2:2.5. This mixture is continuously stirred in a blender to form a uniform, fluid negative electrode active slurry. The negative electrode active slurry is then coated onto carbon-coated copper foil, baked, rolled, and slit to produce the negative electrode sheet.

[0148] Step 3: Wind the above-cut and prepared positive electrode sheets, negative electrode sheets and separators to form a winding core.

[0149] Step 4: Preparation of electrolyte: lithium hexafluorophosphate (LiPF6) with a concentration of 1M is used as the lithium salt, and a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC) with a mass ratio of 1:1:1 and 40% carboxylic acid ester solvent (ethyl propionate (EP) and propyl propionate (PP) with a mass ratio of 1:1) is used as the non-aqueous organic solvent.

[0150] Testing method for the mass content of carboxylate organic solvents in batteries: Electrolyte samples are separated and quantitatively analyzed using a gas chromatograph. The mass content of EP and / or PP is determined using a standard curve method. The mass content of EP or PP, or the sum of the mass contents of EP and PP, is used to determine the mass content. The mass content A of the carboxylate organic solvent in the electrolyte can be adjusted by adjusting the mass ratio of the carboxylate solvent.

[0151] Step 5: Place the coil core into a shell, seal it, and perform other treatments such as liquid injection and formation to obtain a lithium-ion battery, wherein the shell is a steel shell.

[0152] In Examples 1 to 14, the first electrode sheet 11 is a negative electrode sheet, that is, the first additional component 21 is provided at the starting section of the negative electrode sheet, and in Examples 1 to 13, the first additional component 21 is provided on both opposite sides of the starting section. In Example 14, the first additional component 21 is provided only on one side of the starting section. In Examples 15 and 16, the first electrode sheet 11 is a positive electrode sheet, that is, the first additional component 21 is provided at the starting section of the positive electrode sheet, and the first additional component 21 is provided on both opposite sides of the starting section. In Example 17, the starting sections of the first pole piece 11 and the second pole piece 13 are both provided with an additional part 2, and the starting sections are both provided with additional parts 2 on two opposite sides. Specifically, the first starting section 111 of the first pole piece 11 is provided with a first additional part 21 on two opposite sides, and the second starting section 131 of the second pole piece 13 is provided with a third additional part 23 on two opposite sides. At this time, the first pole piece 11 is a negative pole piece and the second pole piece 13 is a positive pole piece. The number of winding turns and L1 in Table 1 refer to the number of winding turns and the corresponding length of the first additional part 21 provided on the first pole piece 11.

[0153] In Comparative Example 1, neither the first electrode sheet 11 nor the second electrode sheet 13 is provided with the additional member 2. In Comparative Examples 2 and 3, the first electrode sheet 11 is a negative electrode sheet, that is, the first additional member 21 is provided at the starting section of the negative electrode sheet, and the first additional member 21 is provided on both opposite sides of the starting section.

[0154] Table 1:

[0155]

[0156]

[0157] The relevant performances of the batteries in the above embodiments and comparative examples were tested, and the test results are recorded in Table 2. The test method is as follows:

[0158] 1. Lithium precipitation test method

[0159] After the battery has completed 800T cycles, it is removed from the test chamber and left to rest for 2 hours. It is then charged at a constant current and constant voltage of 0.5C to 4.4V, with a cut-off of 0.05C. The battery is then dissected in a dry environment (e.g., a dew point of -40°C) to observe the appearance of the negative electrode surface and the separator in contact with it. If grayish-white or dark gray spots or areas appear, it indicates lithium deposition.

[0160] 2. Cyclic test method

[0161] At 25°C, charge at a constant current of 3C to 4.2V, then charge at a constant current and constant voltage of 2C to 4.4V, cut off at 0.05C, and let stand for 10 minutes; then discharge at 0.7C to 3.0V, and repeat this cycle for 800 times. The discharge capacity of the battery at the 800th cycle is C1, and the discharge capacity of the battery at the first full charge is C0. C1 / C0 is the capacity retention rate after 800 cycles.

[0162] 3. Energy density (ED) test method

[0163] The battery is charged to 4.4V at a current of 0.2C, then charged at a constant voltage until the current drops to 0.02C. It is then discharged at a current of 0.2C to 3.0V. The discharged energy is recorded as E. The thickness, width, and length of the battery are measured and the product of the three is calculated to obtain the volume of the battery, recorded as V. The formula for calculating volumetric energy density is VED = E / V.

[0164] Table 2:

[0165]

[0166]

[0167] Combining Tables 1 and 2, it can be seen that because the battery of Comparative Example 1 does not have the additional component 2, the cycle capacity retention rate of the battery of Comparative Example 1 is lower than that of the batteries of Examples 1 to 17, and the battery has a serious lithium plating problem. It can be seen that by providing the first additional component 21 on the first electrode sheet 11, the cycle performance of the battery can be improved and the lithium plating problem of the negative electrode sheet can be alleviated.

[0168] From Table 1 and Table 2, it can be seen that in Comparative Example 2, the mass content of the carboxylic acid ester organic solvent in the electrolyte is not in the range of 5% to 60% and is less than 5%, resulting in poor cycle performance of the battery and serious lithium plating problems in the battery.

[0169] From Table 1 and Table 2, it can be seen that in Comparative Example 3, the mass content of the carboxylic acid ester organic solvent in the electrolyte is not in the range of 5% to 60% and is greater than 60%. Although the cycle performance of the battery is improved compared to Comparative Example 2 and the lithium plating problem is improved, compared to the batteries of Examples 1 to 17, there are still problems of low cycle performance and lithium plating on the negative electrode sheet.

[0170] From Table 1 and Table 2, it can be seen that, comparing Example 1, Example 2, Example 3, Example 11, Example 12 and Example 13, the number of winding turns of the additional component 2 in Example 2 is the least, resulting in the cycle performance of the battery of Example 2 being slightly lower than that of the batteries of Example 1, Example 3, Example 11, Example 12 and Example 13.

[0171] Combining Table 1 and Table 2, it can be seen that, by comparing Example 1 and Example 4, the mass content of the carboxylic acid ester organic solvent in the electrolyte in Example 4 is lower than the mass content of the carboxylic acid ester organic solvent in the electrolyte in Example 1, resulting in the cycle performance of the battery in Example 4 being slightly lower than that of the battery in Example 1.

[0172] Combining Table 1 and Table 2, it can be seen that, by comparing Example 5 and Example 6, the mass content of the carboxylic acid ester organic solvent in the electrolyte in Example 6 is higher than the mass content of the carboxylic acid ester organic solvent in the electrolyte in Example 5, so that the cycle performance of the battery of Example 6 is slightly higher than that of the battery of Example 5.

[0173] From Table 1 and Table 2, it can be seen that, by comparing Example 2 with Example 7, the mass content of the carboxylic acid ester organic solvent in the electrolyte in Example 7 is lower than the mass content of the carboxylic acid ester organic solvent in the electrolyte in Example 2, resulting in the cycle performance of the battery in Example 7 being lower than that of the battery in Example 2.

[0174] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A battery, characterized in that: include: a housing having a receiving space; A winding core (1) is arranged in the accommodation space and is formed by stacking and winding a first pole piece (11), a diaphragm (12), and a second pole piece (13) in sequence, wherein the first pole piece (11) has a first starting section close to a winding center, the first pole piece (11) includes a first winding starting end located in the first starting section, and the first starting section (111) has a first surface (1111) facing the winding center and a second surface (1112) facing away from the winding center. An additional member (2) comprises a first additional member (21), wherein the first additional member (21) is arranged on the first surface (1111) and / or the second surface (1112), the first additional member (21) extends beyond the first winding starting end, and the portion of the first additional member (21) that exceeds the first winding starting end is wound around the winding center for at least one turn; The electrolyte comprises a carboxylate organic solvent having a mass content of 5% to 60% based on the mass of the electrolyte, and the carboxylate organic solvent comprises at least one of ethyl acetate, ethyl propionate, methyl acetate, propyl acetate, methyl propionate, methyl butyrate and ethyl butyrate.

2. The battery according to claim 1, characterized in that The number of turns of the portion of the first additional member (21) that extends beyond the first winding starting end around the winding center is three to eight turns; and / or, Along the winding direction, the length of the first additional member (21) beyond the first winding starting end is L1, and the value range of L1 is 5mm to 80mm; and / or, The first surface (1111) and the second surface (1112) are both provided with the first additional member (21); a portion of the first additional member (21) provided on the first surface (1111) that extends beyond the first winding starting end is connected to a portion of the first additional member (21) provided on the second surface (1112) that extends beyond the first winding starting end; and / or, The additional component (2) includes a substrate layer (25) and / or an adhesive layer (26), and the adhesive layer (26) is arranged on at least one side of the substrate layer (25); the substrate layer (25) is a polymer layer, and the polymer layer includes at least one of polyethylene terephthalate, polyimide, polypropylene, polyethylene, and polyetheretherketone; or, the substrate layer (25) is a metal layer, and the metal layer includes copper elements or aluminum elements; the adhesive layer (26) includes at least one of acrylic glue, hot melt glue, organic silicone, and rubber.

3. The battery according to claim 1 or 2, characterized in that The first pole piece (11) comprises a first empty foil area (115) and a first double-sided coating area (114) which are sequentially connected by the first winding starting end, and the first additional part (21) and the first double-sided coating area (114) are partially overlapped in the winding direction.

4. The battery according to claim 3, characterized in that Along the winding direction, the overlapping length between the first additional member (21) and the first double-sided coating area (114) is L2, and the value range of L2 is 0.5 mm to 5 mm; and / or, The first pole piece (11) has a first tail section away from the winding center, the first pole piece (11) includes a first winding tail end located at the first tail section, and the first tail section (116) has a third surface (1161) facing the winding center and a fourth surface (1162) facing away from the winding center; The attachment (2) further includes a second attachment (22), wherein the second attachment (22) is at least arranged on the third surface (1161), and the second attachment (22) extends out of the first winding end.

5. The battery according to claim 3, characterized in that The second pole piece (13) has a second starting section close to the winding center, the second pole piece (13) includes a second winding starting end located in the second starting section, and the second starting section (131) has a fifth surface (1311) facing the winding center and a sixth surface (1312) facing away from the winding center; The attachment (2) further comprises a third attachment (23), wherein the third attachment (23) is arranged on the fifth surface (1311) and / or the sixth surface (1312), and the third attachment (23) extends out of the second winding starting end.

6. The battery according to claim 5, characterized in that The second pole piece (13) comprises a second empty foil area (135) and a second double-sided coating area (134) which are sequentially connected by the second winding starting end, and the third additional component (23) and the second double-sided coating area (134) are partially overlapped in the winding direction.

7. The battery according to claim 6, characterized in that Along the winding direction, the overlapping length between the third additional member (23) and the second double-sided coating area (134) is L3, and the value range of L3 is 0.5mm to 5mm; and / or, The second pole piece (13) has a second tail section away from the winding center, the second pole piece (13) includes a second winding tail end located in the second tail section, and the second tail section (136) has a seventh surface (1361) facing the winding center and an eighth surface (1362) facing away from the winding center; The attachment (2) further comprises a fourth attachment (24), wherein the fourth attachment (24) is arranged on the seventh surface (1361) and / or the eighth surface (1362), and the fourth attachment (24) extends out of the second winding tail end.

8. The battery according to claim 7, characterized in that The second pole piece (13) further comprises a third empty foil area (137) connected to the second double-sided coating area (134); the second winding end is an end of the third empty foil area (137) away from the second double-sided coating area (134) along the winding direction; and the fourth attachment (24) is partially overlapped with the second double-sided coating area (134); The second pole piece (13) further comprises a second pole tab (138) connected to the third empty foil area (137), and the fourth additional component (24) is covered on the second pole tab (138).

9. The battery according to claim 8, characterized in that Along the winding direction, the overlapping length of the fourth additional member (24) and the second double-sided coating area (134) is L4, and the value range of L4 is 0.5mm to 5mm; and / or, The first pole piece (11) further includes a first pole tab (117), and along the radial direction of the winding core (1), the first pole tab (117) does not overlap with the fourth additional member (24); and / or, The fourth additional member (24) has a first end face and a second end face along the winding direction, the first end face and the winding center form a first connecting line (241), the second end face and the winding center form a second connecting line (242), the first connecting line (241) and the second connecting line (242) form an angle α, and the value range of α is 40° to 160°; and / or, The radial projection of the portion of the third additional part (23) located in the second double-sided coating area (134) falls on the first double-sided coating area (114), and the radial projection of the first additional part (21) located on the second surface (1112) falls on the third additional part (23); the radial projection of the portion of the fourth additional part (24) located in the second double-sided coating area (134) falls on the first double-sided coating area (114); the first pole piece (11) is a negative pole piece, and the second pole piece (13) is a positive pole piece; or, The radial projection of the portion of the third additional part (23) located in the second double-sided coating area (134) falls on the first double-sided coating area (114), and the radial projection of the first additional part (21) located on the second surface (1112) falls on the third additional part (23); the first pole piece (11) further comprises a first single-sided coating area (118) and a fourth empty foil area (119) which are sequentially connected to the first double-sided coating area (114) along the winding direction, and the first winding end is the fourth empty foil area ( 119) is located at one end of the first single-sided coating area (118) in the winding direction, the projection of the portion of the fourth additional member (24) located in the second double-sided coating area (134) radially toward the winding center falls on the first double-sided coating area (114), and the projection of the portion of the fourth additional member (24) located in the second double-sided coating area (134) radially away from the winding center falls on the first single-sided coating area (118); the first pole piece (11) is a negative pole piece, and the second pole piece (13) is a positive pole piece; and / or, The first electrode sheet (11) comprises a negative electrode active material layer, the negative electrode active material layer comprises a silicon-carbon material, and the mass proportion of silicon in the negative electrode active material layer is 1.5% to 50%.

10. The battery according to claim 2, characterized in that The thickness of the substrate layer (25) is t1, and the value range of t1 is 5 μm to 50 μm; and / or, The thickness of the adhesive layer (26) is t2, and the value range of t2 is 2 μm to 16 μm; and / or, The thickness of the additional component (2) is T, the first pole piece (11) comprises a first current collector (112) and a first active layer (113) disposed on at least one side of the first current collector (112), the thickness of the first active layer (113) located on one side of the first current collector (112) is H1, and the value range of T / H1 is 0.3 to 3.5; and / or, The thickness of the additional component (2) is T, the second pole piece (13) comprises a second current collector (132) and a second active layer (133) arranged on at least one side of the second current collector (132), the thickness of the second active layer (133) located on one side of the second current collector (132) is H2, and the value range of T / H2 is 0.3 to 3.5; and / or, The adhesive layer (26) is provided on one side of the base material layer (25), and the adhesive layer (26) is provided on the side of the base material layer (25) facing the first starting section (111).

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