Battery

Abstract

The invention relates to the technical field of batteries, and discloses a battery which comprises a roll core, a first pole piece comprises a first empty foil area and a first coating area which are connected, one end, far away from the first coating area, of the first empty foil area is a winding starting end of the first pole piece, and the part, exceeding the first coating area, of the first empty foil area is wound around a winding center for at least one circle; the first pole piece comprises a silicon-carbon composite material, the mass content of a silicon element in an active layer of the first pole piece is A%, and the value range of A is 1.5-50; the mass of the sulfur-containing additive accounts for 0.1%-6% of the mass of the electrolyte on the basis of the mass of the electrolyte, and the sulfur-containing additive comprises at least one of 1, 3-propane sultone, 1, 3-propene sultone, ethylene sulfate, ethylene sulfite, propylene sulfite, ethylene sulfate and 4-ethylidene methylsulfate. The sulfur-containing additive cooperates with the first empty foil area serving as the heat dissipation part to synchronously improve the high-temperature cycle performance of the battery.

Description

Technical Field

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

[0002] With the rapid development of new energy technologies, battery cells have been widely used in electronic devices, electric vehicles, wearable battery products, and other fields. As battery cells become increasingly widely used, higher requirements are placed on their cycle life and safety performance. However, for the winding core, the heat generated during the charging and discharging process causes the central area of the winding core to become too hot and difficult to dissipate heat, resulting in poor battery cycle performance and the risk of safety issues such as thermal runaway. Summary of the Invention

[0003] In view of this, the present invention provides a battery to solve the problem in the prior art that the temperature in the middle area of the winding core is too high and difficult to dissipate heat, resulting in deterioration of the battery's cycle performance and easily causing safety problems such as thermal runaway.

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

[0005] a housing having a receiving space;

[0006] A winding core is disposed in the accommodating space and is formed by sequentially stacking and winding a first electrode piece, a diaphragm, and a second electrode piece, wherein the first electrode piece includes a first hollow foil area and a first coated area sequentially connected along a winding direction, wherein along the winding direction, an end of the first hollow foil area away from the first coated area is a winding starting end of the first electrode piece, and a portion of the first hollow foil area exceeding the first coated area is wound at least once around the winding center; the first coated area includes an active layer, and the active layer of the first electrode piece includes a silicon-carbon composite material, wherein the mass content of silicon in the active layer is A%, and the value of A ranges from 1.5 to 50;

[0007] The electrolyte comprises a sulfur-containing additive in an amount of 0.1% to 6% by mass based on the mass of the electrolyte, wherein the sulfur-containing additive comprises at least one of 1,3-propane sultone, 1,3-propylene sultone, vinyl sulfate, vinyl sulfite, propylene sulfite, vinyl sulfate, and 4-methylethylene sulfate.

[0008] In an optional embodiment, the number of turns of the portion of the first empty foil area extending beyond the first coated area around the winding center is N, and the value range of A / N is 0.4 to 33; and / or,

[0009] The number of turns of the portion of the first empty foil area extending beyond the first coated area around the winding center is N, and the value of N ranges from 1.5 to 7; and / or,

[0010] Along the winding direction, the length of the portion of the first empty foil area that exceeds the first coated area is L1, and the value of L1 is not less than 7 mm; and / or,

[0011] Along the winding direction, the length of the portion of the first empty foil area that exceeds the first coated area is L1, the diameter of the winding core is d, and L1 / (3.14×d)≥0.2 is satisfied; and / or,

[0012] At least one side of the first hollow foil area is provided with a ceramic layer; and / or,

[0013] The first empty foil area includes a main body and a folded portion. The main body is connected to the first coating area. The folded portion and the main body are stacked in a radial direction of the winding core. There is at least one folded portion.

[0014] In an optional embodiment, the second pole piece includes a second empty foil area and a second coated area. Along the winding direction, the end of the second empty foil area away from the second coated area is the winding starting end of the second pole piece.

[0015] In an optional embodiment, the portion of the second hollow foil area exceeding the second coated area is wound around the winding center for at least one circle; and / or,

[0016] Along the winding direction, the length of the portion of the second empty foil area that exceeds the second coated area is L2, and the value of L2 is not less than 5 mm.

[0017] In an optional embodiment, the second pole piece further includes a third empty foil area, and the second coated area is connected to the third empty foil area along the winding direction, and the end of the third empty foil area away from the second coated area is the winding end of the second pole piece; the battery further includes an insulating layer, and the insulating layer includes a first insulating layer, and the first insulating layer covers two opposite sides of the third empty foil area and partially overlaps with the second coated area.

[0018] In an optional embodiment, the first insulating layer 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 θ, and the value of θ ranges from 10° to 90°; and / or,

[0019] The second pole piece includes a second pole tab, the second pole tab is connected to the third empty foil area, and the first insulating layer covers the second pole tab; and / or,

[0020] The first pole piece includes a first pole tab. Along the radial direction of the winding core, the first pole tab does not overlap with the first insulating layer.

[0021] In an optional embodiment, the first pole piece further includes a fourth hollow foil area, and along the winding direction, the first coating area is connected to the fourth hollow foil area, and the end of the fourth hollow foil area away from the first coating area is the winding end of the first pole piece; the first coating area includes a first double-sided coating area, and along the winding direction, the first double-sided coating area is connected to the fourth hollow foil area, and the projection of the portion of the first insulating layer located in the second coating area radially toward the winding center and away from the winding center both fall on the first double-sided coating area;

[0022] Alternatively, the first pole piece also includes a fourth empty foil area, and along the winding direction, the first coating area is connected to the fourth empty foil area, and the end of the fourth empty foil area away from the first coating area is the winding end of the first pole piece; the first coating area includes a first single-sided coating area and a first double-sided coating area, and along the winding direction, the first double-sided coating area, the first single-sided coating area and the fourth empty foil area are connected in sequence, and the projection of the part of the first insulating layer located in the second coating area radially toward the winding center falls on the first double-sided coating area, and the projection of the part of the first insulating layer located in the second coating area radially away from the winding center falls on the first single-sided coating area.

[0023] In an optional embodiment, the first coating area includes a second single-sided coating area and a second double-sided coating area, and along the winding direction, the first empty foil area, the second single-sided coating area and the second double-sided coating area are sequentially connected and arranged.

[0024] In an optional embodiment, the second coating area includes a third double-sided coating area, the second hollow foil area is connected to the third double-sided coating area, the insulating layer further includes a second insulating layer, the second insulating layer is arranged on two opposite sides of the second hollow foil area and partially overlaps with the third double-sided coating area; the radial projection of the connection between the first hollow foil area and the second single-sided coating area falls on the second insulating layer, and the radial projection of the connection between the second single-sided coating area and the second double-sided coating area falls on the second insulating layer; and / or,

[0025] Along the winding direction, the length of the first empty foil area is L1, the length of the second single-sided coated area is L3, and the value range of L1 / L3 is 1 to 10.

[0026] In an optional embodiment, the insulating layer includes a base material layer and an adhesive layer, and the adhesive layer is arranged on at least one side of the base material layer; the base material layer is a polymer layer, and the polymer layer includes at least one of polyethylene terephthalate, polyimide, polypropylene, polyethylene, and polyetheretherketone; or the base material 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.

[0027] The technical solution of this application has the following advantages:

[0028] The first electrode contains silicon-carbon composite materials. The high theoretical capacity of silicon-carbon composite materials can effectively improve the energy density of the battery. However, the silicon-carbon composite materials expand greatly, and the process of releasing expansion stress is accompanied by friction and extrusion between material particles. These processes will convert mechanical energy into heat energy. At the same time, the silicon-carbon composite materials will continuously react with the electrolyte due to repeated expansion and contraction during the charging and discharging process of the battery, repeatedly forming SEI film (solid electrolyte interface film), generating a large amount of heat and causing the internal temperature of the battery to rise. The high temperature itself will destroy the stability of the SEI film, promote its further decomposition and regeneration, generate more heat, and form a vicious circle. In addition, the particle pulverization caused by the volume change of the silicon-carbon composite material and the failure of contact with the electrode will significantly increase the contact resistance, further aggravate the risk of heat generation, and thus deteriorate the battery's cycle performance, especially the high-temperature cycle performance of the battery. The present application limits the content of silicon elements in the first coating area of the first electrode, while improving the battery's energy density, avoiding the excessive heat generated during the charging and discharging process due to the expansion of the silicon-carbon composite material and its excessive side reactions with the electrolyte, thereby reducing the battery's cycle performance; and, a certain length of empty foil area is reserved in the area near the starting end of the first electrode, and the first empty foil area is made to surround the winding center at least one circle, so that the first empty foil area serves as a heat dissipation part, improves the heat dissipation performance of the middle area of the core, ensures the temperature uniformity of each area of the core, and thus improves the battery's cycle performance; at the same time, adding an appropriate amount of sulfur-containing additives to the electrolyte can form a stable SEI film on the surface of the first electrode, reduce the side reactions of the battery at high temperatures, and thereby cooperate with the first empty foil area as a heat dissipation part to synchronously improve the battery's cycle performance, especially the high-temperature cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] 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.

[0030] Figure 1 It is a structural diagram of a winding core in the prior art;

[0031] Figure 2 This is a schematic structural diagram of a winding core according to an embodiment of the present invention;

[0032] Figure 3 for Figure 2 An enlarged schematic diagram of the winding core at the starting end is shown;

[0033] Figure 4 This is an enlarged schematic diagram of another winding core at the starting end according to an embodiment of the present invention;

[0034] Figure 5 This is a schematic structural diagram of a first pole piece according to an embodiment of the present invention;

[0035] Figure 6 This is a schematic structural diagram of another first pole piece according to an embodiment of the present invention;

[0036] Figure 7 This is a schematic structural diagram of a second pole piece according to an embodiment of the present invention;

[0037] Figure 8 This is a schematic structural diagram of another second pole piece according to an embodiment of the present invention;

[0038] Figure 9 This is a schematic structural diagram of a first pole piece with a folded portion according to an embodiment of the present invention;

[0039] Figure 10 This is a schematic structural diagram of another folding portion according to an embodiment of the present invention;

[0040] Figure 11 This is a schematic structural diagram of another folding portion according to an embodiment of the present invention;

[0041] Figure 12 This is a schematic structural diagram of a winding core with a folded portion according to an embodiment of the present invention;

[0042] Figure 13 Schematic diagram of the structure of the insulating layer according to an embodiment of the present invention;

[0043] Figure 14 This is a structural schematic diagram of a first active layer provided with a recess according to an embodiment of the present invention.

[0044] Description of reference numerals:

[0045] 1. Winding core; 11. First pole piece; 111. First current collector; 112. First active layer; 1121. Recess; 113. First empty foil area; 1131. Main body; 1132. Folding part; 1133. Connecting part; 1134. First folding part; 1135. Second folding part; 1136. First connecting part; 1137. Second connecting part; 114. Ceramic layer; 115. First tab; 116. First coating area; 1161. Second single-sided coating area; 1162. Second double-sided coating area; 1 163. First double-sided coating area; 1164. First single-sided coating area; 117. Fourth hollow foil area; 12. Diaphragm; 13. Second pole piece; 131. Second current collector; 132. Second active layer; 133. Second hollow foil area; 134. Third hollow foil area; 135. Second pole tab; 136. Second coating area; 1361. Third double-sided coating area; 2. Insulating layer; 21. First insulating layer; 211. First connecting line; 212. Second connecting line; 22. Second insulating layer; 23. Base material layer; 24. Adhesive layer. DETAILED DESCRIPTION

[0046] 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.

[0047] The following combination Figures 2 to 14 , describing embodiments of the present invention.

[0048] According to an embodiment of the present invention, on the one hand, a battery is provided, comprising: a housing having a storage space; a winding core 1, arranged in the storage space, and formed by stacking and winding a first electrode 11, a diaphragm 12, and a second electrode 13 in sequence, wherein the first electrode 11 comprises a first hollow foil area 113 and a first coated area 116 connected in sequence along a winding direction, wherein the end of the first hollow foil area 113 away from the first coated area 116 is the winding starting end of the first electrode 11, and the portion of the first hollow foil area 113 exceeding the first coated area 116 is wound around. The center is wound at least once; the first coating area includes an active layer, and the active layer of the first pole piece 11 includes a silicon-carbon composite material, wherein the mass content of silicon element in the active layer is A%, and the value range of A is 1.5 to 50; the electrolyte, based on the mass of the electrolyte, the mass proportion of the sulfur-containing additive in the electrolyte is 0.1% to 6%, and the sulfur-containing additive includes at least one of 1,3-propane sultone, 1,3-propylene sultone, vinyl sulfate, vinyl sulfite, propylene sulfite, vinyl sulfate, and 4-methylethylene sulfate.

[0049] The battery of this embodiment is used so that the first pole piece 11 contains a silicon-carbon composite material. The high theoretical capacity of the silicon-carbon composite material can effectively improve the energy density of the battery. However, the silicon-carbon composite material expands greatly, and the process of releasing the expansion stress is accompanied by friction and extrusion between the material particles. These processes will convert mechanical energy into thermal energy. At the same time, the silicon-carbon composite material will continuously react with the electrolyte due to repeated expansion and contraction during the charging and discharging process of the battery, repeatedly generating SEI film (solid electrolyte interface film), generating a large amount of heat, and causing the internal temperature of the battery to rise. The high temperature itself will destroy the stability of the SEI film, promote its further decomposition and regeneration, generate more heat, and form a vicious cycle. In addition, the particle pulverization caused by the volume change of the silicon-carbon composite material and the failure of contact with the electrode will significantly increase the contact resistance, further aggravate the risk of heat generation, and thus deteriorate the battery's cycle performance, especially the high-temperature cycle performance of the battery. The present application limits the content of silicon in the first coating area of the first electrode, while improving the battery's energy density, avoiding the excessive heat generated during the charging and discharging process due to the expansion of the silicon-carbon composite material and its excessive side reactions with the electrolyte, thereby reducing the battery's cycle performance. In addition, a certain length of empty foil area is reserved in the area near the starting end of the first electrode 11, and the first empty foil area 113 is made to surround the winding center at least once, so that the first empty foil area 113 serves as a heat dissipation part, improves the heat dissipation performance of the middle area of the core 1, and ensures the temperature uniformity of each area of the core 1, thereby improving the battery's cycle performance. At the same time, adding an appropriate amount of sulfur-containing additives to the electrolyte can form a stable SEI film on the surface of the first electrode 11, reduce the side reactions of the battery at high temperatures, and thus cooperate with the first empty foil area 113 as a heat dissipation part to simultaneously improve the battery's cycle performance, especially the high-temperature cycle performance.

[0050] It's worth noting that silicon-containing batteries can provide higher energy density, but they also produce more side reactions during the charge and discharge process, generating more heat. This increases the temperature of the core 1, especially in the central region of the core 1, where heat is difficult to dissipate. This results in excessively high temperatures in the central region, worsening the battery's cycling performance. Therefore, the battery in this embodiment uses an electrolyte containing a sulfur additive to form a stable SEI film on the surface of the first electrode 1, reducing the battery's side reactions at high temperatures and, in turn, reducing the heat generated during the battery's charge and discharge processes. Furthermore, a first hollow foil region 113 of a certain length is used to form a heat dissipation portion around the winding center, improving the heat dissipation performance of the central region of the core 1 and preventing the central region of the core 1 from overheating and affecting the battery's cycling performance. In summary, in this embodiment, by controlling the silicon content of the active layer in the first electrode 11, the energy density of the battery can be improved, and the heat generation during the charging and discharging process can be controlled to a certain extent, thereby avoiding excessive heat generation that cannot be dissipated and affects the cycle performance of the battery. In addition, the use of an electrolyte with a sulfur-containing additive can further reduce the heat generation during the charging and discharging process. At the same time, the first empty foil area 113 is wound in the middle area of the core 1 to form a heat dissipation portion, which facilitates the heat dissipation of the middle area of the core 1, reduces the battery temperature during the charging and discharging process, and improves the temperature uniformity of each area of the battery, thereby improving the cycle performance of the battery.

[0051] It should be noted that if the silicon content in the active layer of the first electrode is too low, that is, the value of A is too small, the improvement in battery energy density will not be significant. If the silicon content in the active layer of the first electrode is too high, that is, the value of A is too large, the heat generated during the battery charge and discharge process will be too high. Even after the battery dissipates heat, the remaining heat will be too high, which will still affect the battery's cycle performance.

[0052] Optionally, the value of A is any value of 1.5, 2, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 42, 45, 48, 50, or a value between any two values.

[0053] For example, when the value of A is 5, it indicates that the content of silicon in the active layer of the first electrode is 5%.

[0054] It should be noted that if the mass percentage of the sulfur-containing additive in the electrolyte is too low, the SEI film formation effect will be insignificant. If the mass percentage of the sulfur-containing additive in the electrolyte is too high, the sulfur-containing additive is generally more unstable at high temperatures. If it is excessive, the decomposition reaction at high temperatures will be rapidly accelerated, generating a large amount of gas, reducing the advantage of having the first empty foil area 113 surround the winding center at least once, thereby deteriorating the battery's high-temperature cycling performance.

[0055] Optionally, the mass proportion of the sulfur-containing additive in the electrolyte is any value of 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, or a value between any two values.

[0056] In this embodiment, the first electrode 11 is a negative electrode, and the second electrode 13 is a positive electrode.

[0057] Furthermore, in one embodiment, the number of turns of the portion of the first bare foil area 113 extending beyond the first coated area 116 around the winding center is N, and the value range of A / N is 0.4 to 33. This configuration improves the cycle performance of the battery while ensuring the energy density of the battery.

[0058] It is worth noting that if the value of A / N is too large, the silicon content in the active layer of the first pole piece is relatively high, and the heat generated during the battery charging and discharging process is relatively high, while the number of windings of the first empty foil area 113 is relatively small, and the heat dissipation capacity of the first empty foil area 113 as a heat dissipation part is limited, resulting in the battery temperature remaining high during the charging and discharging process, affecting the battery's cycle performance. If the value of A / N is too small, the silicon content in the active layer of the first pole piece is relatively low, and the heat generated during the battery charging and discharging process is relatively low, while the number of windings of the first empty foil area 113 is relatively large, which easily leads to the first empty foil area 113 as a heat dissipation part having excessive heat dissipation capacity, and the internal temperature of the battery is lower than normal, which slows down the speed of the electrochemical reaction in the battery, thereby causing the battery capacity to not be effectively utilized, and it will occupy too much space in the winding core 1, resulting in a decrease in the battery energy density.

[0059] On the other hand, in the related art, after the winding of the core 1 is completed and the needle is withdrawn, only the innermost pre-rolled separator 12 at the winding center is formed in the inner circle of the battery (see Figure 1 ), since the diaphragm 12 is relatively thin and soft, when it expands during the cycle of the battery, it cannot effectively resist the expansion stress to maintain the stability of the core structure and the cycle performance, resulting in the expansion during the cycle of the battery causing the winding starting end of the inner circle of the electrode to easily move toward the hollow area of the core 1 or deform, causing the contact flatness and tightness of the first electrode 11 and the second electrode 13 in the local area of the core to be affected, making the gap between the first electrode 11 and the second electrode 13 in the area near the winding starting end too large, which is not conducive to the lithium ion transmission in this area, thereby affecting the cycle performance of the battery.

[0060] Furthermore, the battery in this application may be a button cell battery, in which case the battery housing may be a metal shell, such as a steel shell. The metal shell is relatively hard, and when the battery expands, the expansion stress will act inward and squeeze the winding core, thereby causing the electrode structure on the inner ring of the winding core to deform, resulting in a greater risk of poor contact flatness between the first electrode sheet 11 and the second electrode sheet 13.

[0061] Therefore, in this embodiment, the first empty foil area 113 arranged around the winding center is stronger than the diaphragm, which is equivalent to forming a buffer part of a spring structure at the winding center of the core, which can simultaneously resist and absorb expansion stress, improve the risk of deformation of the electrode in the area near the starting end caused by battery cycle expansion, and make the first electrode 11 and the second electrode 13 in close contact to avoid 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.

[0062] Therefore, it needs to be further explained that if the value of A / N is too large, the content of silicon in the active layer of the first electrode piece is relatively high, and the expansion of the first electrode piece 11 during the charging and discharging process of the battery is relatively high, while the number of winding turns of the first empty foil area 113 is relatively small. The buffering effect of the first empty foil area 113 as a buffer part is limited, resulting in the risk of gaps being formed between the first electrode piece 11 and the second electrode piece 13 during the charging and discharging process, thereby affecting the cycle performance of the battery. If the value of A / N is too small, the silicon content in the active layer of the first electrode is relatively low, and the expansion of the first electrode 11 during the battery charging and discharging process is relatively low, while the number of windings of the first empty foil area 113 is relatively large, which may easily lead to the first empty foil area 113 having an excessive buffering effect as a buffer part. At the same time, the large number of windings of the first empty foil area 113 will also make the internal resistance to deformation too large, so that the battery expansion stress cannot be released, thereby causing the risk of material in the battery coating area being damaged or falling, worsening the battery cycle performance, and the large number of windings of the first empty foil area 113 will occupy too much space in the core 1, resulting in the battery energy density being affected.

[0063] Optionally, the value of A / N is any value among 0.4, 1, 2, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 33, or a value between any two values.

[0064] Specifically, in one embodiment, the number of turns of the portion of the first empty foil area 113 extending beyond the first coating area 116 around the winding center is N, and the value of N ranges from 1.5 to 7.

[0065] Optionally, the value of N is any value of 1.5, 1.8, 2, 2.2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 6.8, 7, or a value between any two values.

[0066] Specifically, in one embodiment, Figure 5 and Figure 6 As shown, along the winding direction, the length of the portion of the first empty foil area 113 that exceeds the first coating area 116 is L1, and the value of L1 is not less than 7 mm.

[0067] It can be understood that if the value of L1 is too small, the number of winding turns of the first empty foil area 113 is insufficient and the length is too short, which may easily lead to insufficient heat dissipation capacity of the first empty foil area 113 and insufficient effect on improving the deformation of the inner ring electrode 1 of the battery cell; if the value of L1 is too large, the number of winding turns of the first empty foil area 113 is too many and the length is too long, which occupies too much space on the core 1 and is not conducive to improving the energy density of the battery.

[0068] Furthermore, in one embodiment, Figure 2 and Figure 5 As shown, along the winding direction, the length of the first hollow foil area 113 extending beyond the first coated area 116 is L1, and the diameter of the winding core 1 is d, satisfying L1 / (3.14×d)≥0.2. This arrangement ensures that the length of the first hollow foil area 113 and the diameter of the winding core 1 are well matched, ensuring the heat dissipation effect of the first hollow foil area 113 while keeping the overall size of the battery within an appropriate range. This avoids increasing the ineffective size of the battery due to the presence of the first hollow foil area 113 surrounding the winding center, thereby ensuring the battery's energy density.

[0069] In one embodiment, Figure 4 As shown, the second pole piece 13 includes a second empty foil area 133 and a second coated area 136. Along the winding direction, the end of the second empty foil area 133 away from the second coated area 136 is the winding starting end of the second pole piece 13. Furthermore, in one embodiment, the portion of the second empty foil area 133 that exceeds the second coated area 136 is wound around the winding center for at least one circle. In this way, the first empty foil area 113 and the second empty foil area 133 arranged around the winding center are utilized to simultaneously resist and absorb the deformation of the area near the starting end of the first pole piece 11 and the area near the starting end of the second pole piece 13, so that the first pole piece 11 and the second pole piece 13 are in close contact, avoiding the generation of abnormal gaps during the battery cycle, thereby improving the interface stability between the first pole piece 11 and the second pole piece 13 and improving the cycle performance of the battery.

[0070] Specifically, in one embodiment, Figure 8 As shown, along the winding direction, the length of the second hollow foil area 133 extending beyond the second coated area 136 is L2, and the value of L2 is not less than 5 mm. This configuration ensures that the second hollow foil area 133, disposed around the winding center, resists and absorbs deformation of the second electrode sheet 13 near the winding starting point, thereby reducing the risk of electrode sheet deformation near the starting point caused by battery cycle expansion and improving the battery's cycle life.

[0071] In one embodiment, Figure 2As shown, the second electrode sheet 13 further includes a third hollow foil region 134. Along the winding direction, the second coated region 136 is connected to the third hollow foil region 134. The end of the third hollow foil region 134 away from the second coated region 136 serves as the winding end of the second electrode sheet 13. The battery further includes an insulating layer 2, which includes a first insulating layer 21. The first insulating layer 21 covers two opposing surfaces of the third hollow foil region 134 and partially overlaps the second coated region 136. This arrangement prevents burrs generated by cutting at the winding end from puncturing the separator 12, thereby improving battery safety.

[0072] Furthermore, in one embodiment, Figure 2 As shown, the first insulating layer 21 has a first end face and a second end face along the winding direction. The first end face forms a first line 211 with the winding center, and the second end face forms a second line 212 with the winding center. The first line 211 and the second line 212 form an angle θ, with a value of θ ranging from 10° to 90°. This arrangement ensures that the first insulating layer 21 effectively covers the third hollow foil area 134 while reducing the risk of interference between the core 1 and the outer shell when assembled into the shell.

[0073] It is worth noting that if the value of θ is too small, the coverage of the first insulating layer 21 is too small, failing to effectively cover the third hollow foil area 134. This can easily expose burrs at the end of the second winding and pierce the separator 12, affecting the safety performance of the battery. If the value of θ is too large, the coverage of the first insulating layer 21 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.

[0074] Optionally, the value of θ is any value of 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, 90°, or a value between any two values.

[0075] In one embodiment, Figure 2 As shown, the second pole piece 13 includes a second pole tab 135, which is connected to the third hollow foil area 134. The first insulating layer 21 covers the second pole tab 135. The first insulating layer 21 can not only isolate and protect the burrs at the winding end of the second pole piece 13, but also cover the position of the second pole tab 135, thereby achieving a protective effect for the second pole tab 135.

[0076] Of course, in other alternative embodiments, the first insulating layer 21 may not cover the second tab 135 , but may be additionally covered with another tab protection tape.

[0077] Furthermore, in one embodiment, Figure 2As shown, the first pole piece 11 includes a first pole tab 115. Along the radial direction of the winding core 1, the first pole tab 115 does not overlap with the first insulating layer 21. This arrangement prevents the first pole tab 115 and the second pole tab 135 from overlapping and causing thickness overlap, thereby reducing the radius of the winding core 1 and improving the battery energy density.

[0078] In one embodiment, Figure 2 As shown, the first electrode piece 11 further includes a fourth empty foil area 117 . Along the winding direction, the first coating area 116 is connected to the fourth empty foil area 117 . The end of the fourth empty foil area 117 away from the first coating area 116 is the winding end of the first electrode piece 11 .

[0079] Further, in one embodiment, Figure 6 As shown, the first coating area 116 includes a first double-sided coating area 1163. Along the winding direction, the first double-sided coating area 1163 is connected to the fourth empty foil area 117. The projection of the portion of the first insulating layer 21 located in the second coating area 136 radially toward the winding center and the projection away from the winding center both fall on the first double-sided coating area 1163. 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), thereby avoiding the occurrence of lithium plating problems.

[0080] Or, in another embodiment, Figure 2 and Figure 5 As shown, the first coating area 116 includes a first single-sided coating area 1164 and a first double-sided coating area 1163. Along the winding direction, the first double-sided coating area 1163, the first single-sided coating area 1164 and the fourth empty foil area 117 are connected in sequence. The projection of the portion of the first insulating layer 21 located in the second coating area 136 radially toward the winding center falls on the first double-sided coating area 1163, and the projection of the portion of the first insulating layer 21 located in the second coating area 136 radially away from the winding center falls on the first single-sided coating area 1164. It can be understood that the active layer of the first single-sided coating area 1164 is provided on the side of the first pole piece 11 facing the winding center. That is, please refer to Figure 2 On the inner circle adjacent to the winding end of the second electrode sheet 13, the intersection of the first double-sided coated area 1163 and the first single-sided coated area 1164 extends beyond the portion of the first insulating layer 21 located in the second coating area 136 along the winding direction. On the outer circle adjacent to the winding end of the second electrode sheet 13, the intersection of the first single-sided coated area 1164 and the fourth hollow foil area 117 extends beyond the portion of the first insulating layer 21 located in the second coating area 136 along the winding direction. This arrangement ensures that lithium ions released from the active layer of the second electrode sheet 13 (positive electrode sheet) are received by the corresponding active layer of the first electrode sheet 11 (negative electrode sheet), thus preventing the occurrence of lithium plating.

[0081] In one embodiment, Figure 4 As shown, the first coating area 116 includes a second single-sided coating area 1161 and a second double-sided coating area 1162. Along the winding direction, the first empty foil area 113, the second single-sided coating area 1161, and the second double-sided coating area 1162 are sequentially connected. The second coating area 136 includes a third double-sided coating area 1361. The second empty foil area 133 is connected to the third double-sided coating area 1361. The insulating layer 2 also includes a second insulating layer 22. The second insulating layer 22 is arranged on two opposite sides of the second empty foil area 133 and partially overlaps with the third double-sided coating area 1361. The radial projection of the connection between the first empty foil area 113 and the second single-sided coating area 1161 falls on the second insulating layer 22, and the radial projection of the connection between the second single-sided coating area 1161 and the second double-sided coating area 1162 falls on the second insulating layer 22. That is, the portion of the second insulating layer 22 located on the third double-sided coating area 1361 is projected radially toward the winding center onto the second single-sided coating area 1161, and the portion of the second insulating layer 22 located on the third double-sided coating area 1361 is projected radially away from the winding center onto the second double-sided coating area 1162. This arrangement enables the lithium ions released from the active layer of the second electrode 13 (positive electrode) to be received by the active layer of the corresponding first electrode 11 (negative electrode), thereby avoiding the occurrence of lithium plating problems.

[0082] As an alternative embodiment, Figure 3 As shown, the first coating area 116 includes a second double-sided coating area 1162, and along the winding direction, the first empty foil area 113 and the second double-sided coating area 1162 are sequentially connected. At this time, the radial projection of the portion of the second insulating layer 22 located on the third double-sided coating area 1361 falls on the second double-sided coating area 1162. That is, the radial projection of the portion of the second insulating layer 22 located on the third double-sided coating area 1361 toward the winding center and the projection away from the winding center both fall on the second double-sided coating area 1162. In this way, the lithium ions released from the active layer of the second electrode 13 (positive electrode) can be received by the active layer of the corresponding first electrode 11 (negative electrode), thereby avoiding the occurrence of lithium plating problems.

[0083] It is worth noting that, in one embodiment, the second insulating layer 22 extends beyond the winding starting end of the second pole piece 13. This arrangement can prevent the burrs generated by cutting at the winding starting end from puncturing the diaphragm 12, thereby improving the battery safety performance.

[0084] Furthermore, in one embodiment, Figure 6As shown, along the winding direction, the length of the first hollow foil area 113 is L1, the length of the second single-sided coated area 1161 is L3, and the value range of L1 / L3 is 1 to 10. This arrangement ensures the heat dissipation capacity of the first hollow foil area 113 and the resistance and absorption effect on electrode deformation while ensuring the energy density of the battery.

[0085] Optionally, the value of L1 / L3 is any value of 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or a value between any two values.

[0086] In one embodiment, Figure 13 As shown, the insulating layer 2 includes a base material layer 23 and an adhesive layer 24 , and the adhesive layer 24 is disposed on at least one side of the base material layer 23 .

[0087] Furthermore, the substrate layer 23 is a polymer layer, and the polymer layer includes at least one of polyethylene terephthalate (PP), polyimide (PET), polypropylene (PE), polyethylene (PI), and polyetheretherketone (PEEK).

[0088] Alternatively, the base material layer 23 is a metal layer, and the metal layer includes copper or aluminum. Specifically, the metal layer can be copper foil, aluminum foil, etc.

[0089] Furthermore, the adhesive layer 24 includes at least one of acrylic adhesive, hot melt adhesive, organic silicone, and rubber.

[0090] It is worth noting that the insulating layer 2 adopts a combination of a base material layer 23 and an adhesive layer 24. The base material layer 23 has a certain strength. When the second insulating layer 22 is wound with the second empty foil area 133 to form a buffer portion, the buffer portion can enhance the resistance and absorption effect of the electrode deformation. At the same time, the adhesive layer 24 has a certain compressibility, which can provide a buffer for the expansion of the electrode, thereby further improving the problem of deformation of the electrode in the area near the starting end caused by battery cycle expansion.

[0091] In one embodiment, Figure 5 As shown, a ceramic layer 114 is provided on at least one side of the first hollow foil region 113. This configuration can improve the structural strength of the first hollow foil region 113, thereby enhancing the buffering effect of the first hollow foil region 113 as a buffer, and further improving the problem of deformation of the electrode near the starting end caused by battery cycle expansion.

[0092] In one embodiment, Figures 9 to 12As shown, the first hollow foil region 113 includes a main portion 1131 and a folded portion 1132. The main portion 1131 is connected to the first coated region 116. The folded portion 1132 is stacked with the main portion 1131 along the radial direction of the winding core 1. There is at least one folded portion 1132. This arrangement allows the first hollow foil region 113 to form a locally thicker area, improving the structural rigidity of the first hollow foil region 113. This further improves the problem of electrode deformation near the starting end caused by battery cycling expansion, resulting in poor contact between the electrode sheets and reduced cycling performance.

[0093] Specifically, as a first embodiment of the folding portion 1132, as Figure 9 As shown, the folding portion 1132 is provided with one, and the main body 1131 has a first end connected to the first coating area 116 and a second end away from the first coating area 116. The folding portion 1132 and the main body 1131 are stacked along the radial direction of the winding core 1. One end of the folding portion 1132 is connected to the second end of the main body 1131 via a connecting portion 1133, and the other end of the folding portion 1132 is located near the first coating area 116. In other words, the first empty foil area 113 is folded once, and the connecting portion 1133 is the bend.

[0094] As a second embodiment of the folding portion 1132, Figure 10 As shown, a plurality of folding portions 1132 are provided, and the plurality of folding portions 1132 and the main body portion 1131 are sequentially stacked along the radial direction of the winding core 1. The first empty foil area 113 also includes at least two connecting portions 1133, which respectively connect the main body portion 1131 and an adjacent folding portion 1132, and two adjacent folding portions 1132. In other words, the first empty foil area 113 is folded multiple times, and the connecting portions 1133 are bends.

[0095] As a third embodiment of the folding portion 1132, Figure 11As shown, the folding portion 1132 is provided with two, namely a first folding portion 1134 and a second folding portion 1135. The second folding portion 1135, the first folding portion 1134, and the main body 1131 are sequentially stacked along the radial direction of the winding core 1 (i.e., the first folding portion 1134 is located between the main body 1131 and the second folding portion 1135). The main body 1131 has a first end connected to the first coating area 116 and a second end away from the first coating area 116. The first folding portion 1134 has a first end close to the first coating area 116 and a second end away from the first coating area 116. The second folding portion 1135 has a first end close to the first coating area 116 and a second end away from the second coating area 136. The first hollow foil region 113 further includes a first connecting portion 1136 and a second connecting portion 1137. The first connecting portion 1136 connects the first end of the first folded portion 1134 and the first end of the second folded portion 1135, while the second connecting portion 1137 connects the second end of the main body 1131 and the second end of the second folded portion 1135. In other words, the first hollow foil region 113 is folded twice, with the first connecting portion 1136 representing the first bend and the second connecting portion 1137 representing the second bend. The second end of the first folded portion 1134 represents the cut end of the first hollow foil region 113. In this embodiment, the cut end of the first hollow foil region 113 is concealed and covered, preventing burrs from puncturing the separator 12 and improving battery safety.

[0096] In this embodiment, if Figure 5 and Figure 6 As shown, the first electrode sheet 11 includes a first current collector 111 and a first active layer 112 disposed on at least one side of the first current collector 111. The first empty foil area 113 corresponds to a portion of the first current collector 111 on both opposite sides without the first active layer 112. The second single-sided coated area 1161 corresponds to a portion of the first current collector 111 on one side with the first active layer 112 disposed on the other side. The second double-sided coated area 1162 corresponds to a portion of the first current collector 111 on both opposite sides with the first active layer 112 disposed on the first double-sided coated area 1163. The first double-sided coated area 1163 corresponds to a portion of the first current collector 111 on both opposite sides with the first active layer 112 disposed on the first side. The first single-sided coated area 1164 corresponds to a portion of the first current collector 111 on one side with the first active layer 112 disposed on the other side. The fourth empty foil area 117 corresponds to a portion of the first current collector 111 on both opposite sides without the first active layer 112 disposed on the first active layer 112.

[0097] It is worth noting that, for the first pole piece 11 , along the winding direction, the second double-sided coating area 1162 and the first double-sided coating area 1163 can be connected. Of course, other coating areas can also be provided between the second double-sided coating area 1162 and the first double-sided coating area 1163 .

[0098] In this embodiment, if Figure 7 and Figure 8 As shown, the second pole piece 13 includes a second current collector 131 and a second active layer 132 disposed on at least one side of the second current collector 131. The second active layer 132 is not disposed on both opposite sides of the portion of the second current collector 131 corresponding to the second hollow foil area 133. The second active layer 132 is disposed on both opposite sides of the portion of the second current collector 131 corresponding to the third double-sided coating area 1361. The second active layer 132 is not disposed on both opposite sides of the portion of the second current collector 131 corresponding to the third hollow foil area 134.

[0099] Further, such as Figure 14 As shown, the first active layer 112 is recessed to form a concave portion 1121 on one side away from the first current collector 111. With this arrangement, when the battery is charged, the active layers on both sides of the concave portion 1121 can expand toward the concave portion 1121, thereby reducing the expansion of the negative electrode sheet along the thickness direction.

[0100] Specifically, in this embodiment, Figure 14 As shown, along the thickness direction of the first pole piece 11 (ie, the radial direction of the winding core 1 ), the depression depth of the recess 1121 is k, and the thickness of the first current collector 111 is t, satisfying k≥t, to ensure that there is enough space for buffering expansion.

[0101] Specifically, in this embodiment, Figure 14 As shown, a plurality of recesses 1121 are arranged at intervals along the length direction (ie, the winding direction) of the first pole piece 11 , and the distance between adjacent recesses 1121 is l, and the value range of l is 0.5 mm to 1.5 mm.

[0102] Optionally, the value of l is any value among 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, or a value between any two values.

[0103] 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.

[0104] Battery preparation process:

[0105] Example 1

[0106] 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 obtain the positive electrode sheet (i.e., the second electrode sheet).

[0107] Step 2: Graphite, silicon-carbon composite material, conductive carbon black (SuperP), polyacrylic acid, and carboxymethyl cellulose are mixed in deionized water at a weight ratio of 41.4:55.5:0.5:1.3:0.4:0.9. The mixture is stirred continuously in a blender to form a uniform, fluid negative electrode active slurry. The negative electrode active slurry is applied to a carbon-coated copper foil to form a negative electrode active layer. The area on at least one side of the current collector where the negative electrode active layer is provided is the first coated area 116, and the areas on both sides where the active layer is not provided are the bare foil areas. After baking, rolling, and slitting, the negative electrode sheet (i.e., the first electrode sheet) is obtained. The specific winding parameters of the first bare foil area 113 of the negative electrode sheet are shown in the following table.

[0108] Test method for the mass content of silicon in the negative electrode active layer of the first coating area: The method for determining the mass content of silicon-based particles in the negative electrode active coating may include the following steps: disassembling the lithium-ion battery, removing the negative electrode sheet, soaking and rinsing it with dimethyl carbonate, and drying it. Then, under SEM backscattering mode, select at least 5 silicon-based particles, obtain the silicon content percentage of each silicon-based particle through EDS point scanning mode, and calculate the average silicon content percentage of the silicon-based particles. The dried negative electrode sheet is then subjected to high-temperature treatment at 400°C for 2 hours (such as in a tube furnace, under a nitrogen or argon atmosphere). The negative electrode active material layer can be peeled off from the current collector and the negative electrode active material can be collected. To test silicon content, a thermogravimetric analyzer (such as the TGA 550) is used with a sample size of 5mg-15mg. The temperature is raised from room temperature to 900°C at a rate of 10°C / min in an air or oxygen atmosphere, and then held at 900°C for 40 minutes. This allows the non-silicon components in the negative electrode material's active layer to volatilize while the silicon is fully oxidized to silicon dioxide. The weight percentage at the end of the test is the ash content of the negative electrode active layer. This 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 in the negative electrode active layer. The mass content of the silicon-based particles in the negative electrode active layer can be calculated from the percentage of silicon and the average silicon content of the silicon-based particles.

[0109] Step 3: Wind the above-cut and prepared positive electrode sheets, negative electrode sheets and separators to form a winding core.

[0110] Step 4: Prepare an electrolyte with lithium hexafluorophosphate (LiPF6) at a concentration of 1M as the lithium salt, a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC) in a mass ratio of 1:1:1:1, and a carboxylic acid ester solvent (ethyl propionate (EP) and propyl propionate (PP) at a mass ratio of 1:1) as the non-aqueous organic solvent, and the electrolyte also includes a sulfur-containing additive with a mass content of 2.00%, specifically 1,3-propane sultone.

[0111] Test method for the mass content of sulfur-containing additives in electrolyte: The mass content can be obtained by separating and quantitatively analyzing the electrolyte sample using a gas chromatograph.

[0112] Step 5: Place the coil core into the outer shell, seal it, and perform other treatments such as liquid injection and formation to obtain a lithium-ion battery. The outer shell is a steel shell.

[0113] The battery preparation processes of Examples 2 to 16 and Comparative Examples 1 to 5 are substantially the same as those of Example 1, and specific parameter changes are shown in Table 1.

[0114] Table 1:

[0115]

[0116]

[0117] 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:

[0118] 1. 600T cycle test method at 45°C

[0119] At 45°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 600 times. The discharge capacity of the battery at the 600th 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 600 cycles.

[0120] 2. 1000T cycle test method at 25℃

[0121] 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 1000 times. The discharge capacity of the battery at the 1000th 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 1000 cycles.

[0122] 3. Energy density (ED) test method

[0123] 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.

[0124] Table 2:

[0125] 600T high temperature cycle performance at 45℃ 1000T cycle performance at 25℃ ED (Wh / L) Example 1 87.1％ 88.5％ 512 Example 2 88.3％ 88.7％ 487 Example 3 85.3％ 88.6％ 530 Example 4 84.6％ 88.2％ 543 Example 5 84.1％ 88.0％ 505 Example 6 85.5％ 87.5％ 517 Example 7 85.7％ 87.9％ 517 Example 8 87.6％ 89.2％ 519 Example 9 85.7％ 87.8％ 518 Example 10 85.6％ 87.5％ 518 Example 11 82.5％ 84.8％ 480 Example 12 81.8％ 83.8％ 532 Example 13 83.1％ 84.5％ 515 Example 14 83.5％ 84.7％ 509 Example 15 85.7％ 87.5％ 511 Example 16 85.4％ 87.8％ 475 Comparative Example 1 80.1％ 83.2％ 482 Comparative Example 2 79.7％ 82.6％ 556 Comparative Example 3 77.8％ 81.9％ 495 Comparative Example 4 76.1％ 80.1％ 493 Comparative Example 5 80.7％ 82.9％ 500

[0126] From Table 1 and Table 2, it can be seen that, by comparing Example 1 with Comparative Example 1, in Comparative Example 1, the content of silicon element in the active layer of the first electrode is not in the range of 1.5% to 50% and is lower than 1.5%, resulting in the battery energy density of Comparative Example 1 being lower than the battery energy density of Example 1.

[0127] From Table 1 and Table 2, it can be seen that, by comparing Example 1 with Comparative Example 2, in Comparative Example 2, the content of silicon in the active layer of the first electrode is not within the range of 1.5% to 50% and is higher than 50%, resulting in the cycle performance of the battery of Comparative Example 2 being lower than the cycle performance of the battery of Example 1.

[0128] From Table 1 and Table 2, it can be seen that, when comparing Example 1 and Comparative Example 3, in Comparative Example 3, the first empty foil area is not made to surround the winding center to form a heat dissipation portion, resulting in the cycle performance of the battery of Comparative Example 3 being lower than the cycle performance of the battery of Example 1.

[0129] Combining Table 1 and Table 2, it can be seen that, by comparing Example 1 and Comparative Example 4, in Comparative Example 4, the battery does not use an electrolyte having a sulfur-containing additive, resulting in the cycle performance of the battery of Comparative Example 4 being lower than that of the battery of Example 1.

[0130] From Table 1 and Table 2, it can be seen that, by comparing Example 1 with Comparative Example 5, in Comparative Example 5, the content of the sulfur-containing additive in the electrolyte is not within the range of 0.1% to 6% and is higher than 6%, resulting in the cycle performance of the battery of Comparative Example 5 being lower than that of the battery of Example 1.

[0131] From Table 1 and Table 2, it can be seen that, comparing Example 1 and Example 2, the silicon content in the active layer of the first pole piece of the battery of Example 2 is lower than the silicon content in the active layer of the first pole piece of the battery of Example 1. Therefore, the high-temperature cycle performance of the battery of Example 2 is higher than the high-temperature cycle performance of the battery of Example 1, but the energy density of the battery of Example 2 is lower than the energy density of the battery of Example 1.

[0132] From Table 1 and Table 2, it can be seen that, by comparing Example 1 and Example 3, the silicon content in the active layer of the first pole piece of the battery of Example 3 is higher than the silicon content in the active layer of the first pole piece of the battery of Example 1. Therefore, the energy density of the battery of Example 3 is higher than the energy density of the battery of Example 1, but the high-temperature cycle performance of the battery of Example 3 is lower than the high-temperature cycle performance of the battery of Example 1.

[0133] From Table 1 and Table 2, it can be seen that, comparing Example 13 and Example 14, the value of N in Example 13 is smaller than the value of N in Example 14. Therefore, the energy density of the battery of Example 13 is higher than the energy density of the battery of Example 14, but the cycle performance of the battery of Example 13 is lower than the cycle performance of the battery of Example 14.

[0134] 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 accommodating 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) comprises a first empty foil area (113) and a first coating area (116) which are sequentially connected and arranged along a winding direction, wherein along the winding direction, an end of the first empty foil area (113) away from the first coating area (116) is the winding starting end of the first pole piece (11), and a portion of the first empty foil area (113) exceeding the first coating area (116) is wound around the winding center for at least one turn; the first coating area comprises an active layer, and the active layer of the first pole piece (11) comprises a silicon-carbon composite material, wherein the mass content of silicon element in the active layer is A%, and the value of A ranges from 1.5 to 50; The electrolyte comprises a sulfur-containing additive in an amount of 0.1% to 6% by mass based on the mass of the electrolyte, wherein the sulfur-containing additive comprises at least one of 1,3-propane sultone, 1,3-propylene sultone, vinyl sulfate, vinyl sulfite, propylene sulfite, vinyl sulfate, and 4-methylethylene sulfate.

2. The battery according to claim 1, characterized in that The number of turns of the portion of the first empty foil area (113) that extends beyond the first coated area (116) around the winding center is N, and the value of A / N ranges from 0.4 to 33; and / or, The number of turns of the portion of the first empty foil area (113) that extends beyond the first coated area (116) around the winding center is N, and the value of N ranges from 1.5 to 7; and / or, Along the winding direction, the length of the portion of the first empty foil area (113) that exceeds the first coated area (116) is L1, and the value of L1 is not less than 7 mm; and / or, Along the winding direction, the length of the portion of the first empty foil area (113) that exceeds the first coated area (116) is L1, the diameter of the winding core (1) is d, and L1 / (3.14×d)≥0.2 is satisfied; and / or, At least one side of the first empty foil area (113) is provided with a ceramic layer (114); and / or, The first empty foil area (113) comprises a main body (1131) and a folding portion (1132), wherein the main body (1131) is connected to the first coating area (116), and the folding portion (1132) and the main body (1131) are stacked in a radial direction of the winding core (1), and at least one folding portion (1132) is provided.

3. The battery according to claim 1 or 2, characterized in that The second pole piece (13) comprises a second empty foil area (133) and a second coating area (136); along the winding direction, the end of the second empty foil area (133) away from the second coating area (136) is the winding starting end of the second pole piece (13).

4. The battery according to claim 3, characterized in that The portion of the second hollow foil area (133) that exceeds the second coated area (136) is wound around the winding center for at least one turn; and / or, Along the winding direction, the length of the portion of the second empty foil area (133) that exceeds the second coating area (136) is L2, and the value of L2 is not less than 5 mm.

5. The battery according to claim 3, characterized in that The second pole piece (13) further comprises a third hollow foil area (134); along the winding direction, the second coating area (136) is connected to the third hollow foil area (134); an end of the third hollow foil area (134) away from the second coating area (136) is the winding end of the second pole piece (13); the battery further comprises an insulating layer (2); the insulating layer (2) comprises a first insulating layer (21); the first insulating layer (21) covers two opposite sides of the third hollow foil area (134) and partially overlaps with the second coating area (136).

6. The battery according to claim 5, characterized in that The first insulating layer (21) has a first end face and a second end face along a winding direction, the first end face and the winding center form a first connecting line (211), the second end face and the winding center form a second connecting line (212), the first connecting line (211) and the second connecting line (212) form an angle θ, and the value range of θ is 10° to 90°; and / or, The second pole piece (13) includes a second pole tab (135), the second pole tab (135) is connected to the third empty foil area (134), and the first insulating layer (21) covers the second pole tab (135); and / or, The first pole piece (11) comprises a first pole tab (115), and along the radial direction of the winding core (1), the first pole tab (115) does not overlap with the first insulating layer (21).

7. The battery according to claim 5, characterized in that The first pole piece (11) further comprises a fourth empty foil area (117); along the winding direction, the first coating area (116) is connected to the fourth empty foil area (117); an end of the fourth empty foil area (117) away from the first coating area (116) is the winding end of the first pole piece (11); the first coating area (116) comprises a first double-sided coating area (1163); along the winding direction, the first double-sided coating area (1163) is connected to the fourth empty foil area (117); a portion of the first insulating layer (21) located in the second coating area (136) has its projection radially toward the winding center and its projection away from the winding center both falling on the first double-sided coating area (1163); Alternatively, the first pole piece (11) further comprises a fourth empty foil area (117), and along the winding direction, the first coating area (116) is connected to the fourth empty foil area (117), and the end of the fourth empty foil area (117) away from the first coating area (116) is the winding end of the first pole piece (11); the first coating area (116) comprises a first single-sided coating area (1164) and a first double-sided coating area (1163), and along the winding direction, the first double-sided coating area (1163), the first single-sided coating area (1164) and the fourth empty foil area (117) are connected in sequence, and the projection of the portion of the first insulating layer (21) located in the second coating area (136) radially toward the winding center falls on the first double-sided coating area (1163), and the projection of the portion of the first insulating layer (21) located in the second coating area (136) radially away from the winding center falls on the first single-sided coating area (1164).

8. The battery according to claim 5, characterized in that The first coating area (116) includes a second single-sided coating area (1161) and a second double-sided coating area (1162). Along the winding direction, the first empty foil area (113), the second single-sided coating area (1161) and the second double-sided coating area (1162) are connected in sequence.

9. The battery according to claim 8, characterized in that The second coating area (136) includes a third double-sided coating area (1361), the second empty foil area (133) is connected to the third double-sided coating area (1361), the insulating layer (2) also includes a second insulating layer (22), the second insulating layer (22) is arranged on two opposite sides of the second empty foil area (133) and partially overlaps with the third double-sided coating area (1361); the radial projection of the connection between the first empty foil area (113) and the second single-sided coating area (1161) falls on the second insulating layer (22), and the radial projection of the connection between the second single-sided coating area (1161) and the second double-sided coating area (1162) falls on the second insulating layer (22); and / or, Along the winding direction, the length of the first empty foil area (113) is L1, the length of the second single-sided coated area (1161) is L3, and the value range of L1 / L3 is 1 to 10.

10. The battery according to claim 5, characterized in that The insulating layer (2) includes a base material layer (23) and an adhesive layer (24), wherein the adhesive layer (24) is arranged on at least one side of the base material layer (23); the base material layer (23) is a polymer layer, and the polymer layer includes at least one of polyethylene terephthalate, polyimide, polypropylene, polyethylene, and polyetheretherketone; or the base material layer (23) is a metal layer, and the metal layer includes copper or aluminum; and the adhesive layer (24) includes at least one of acrylic adhesive, hot melt adhesive, organic silicone, and rubber.

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