Battery and electric equipment

Abstract

The invention relates to the technical field of lithium batteries, discloses a battery and electric equipment, and aims to improve the safety performance of the battery in a high-temperature environment and the electrolyte infiltration effect. The battery comprises a positive plate, a first diaphragm, a negative plate and a second diaphragm, the positive plate is provided with a positive tab, the negative plate is provided with a negative tab, and the positive tab and the negative tab are positioned on the same side; the first diaphragm and the second diaphragm are arranged on two sides of the negative plate along the thickness direction of the battery; along one side close to the extension direction of the positive tab, the edges of the first diaphragm and the second diaphragm exceed the negative plate and form a first edge; at least partial areas of the first edge are connected to form a composite area, and at least partial areas are not connected to form a non-composite area; the battery comprises an electrolyte, wherein the electrolyte comprises a carboxylic ester organic solvent; on the basis of the mass of the electrolyte, the mass content A of the carboxylic ester organic solvent in the electrolyte is 7.5%-60%.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and in particular to a battery and electrical equipment. Background Art

[0002] With the widespread adoption of lithium-ion batteries in consumer electronics, electric vehicles, and other fields, safety and reliability issues have become a key bottleneck hindering the commercialization of high-energy-density batteries. Under extreme operating conditions such as high temperature, high pressure, or mechanical stress, traditional battery structures are prone to heat generation, causing the separator to shrink. This can lead to direct contact between the positive and negative electrodes, resulting in internal micro-short circuits and a thermal runaway chain reaction, leading to battery failure or even fire and explosion.

[0003] Some technical solutions improve battery safety by bonding the separator at the top of the battery (the end with the tab), effectively reducing the risk of short circuits caused by separator shrinkage. However, in this design, the physical barrier formed in the bonding area blocks the electrolyte infiltration path at the top of the battery, hindering electrolyte penetration between the electrode layers and poor electrolyte infiltration, which in turn affects battery performance. Summary of the Invention

[0004] In view of this, the present invention provides a battery and an electrical device to solve the problem that existing technical solutions are difficult to balance improving the safety performance of the battery in a high temperature environment and the electrolyte infiltration effect.

[0005] In a first aspect, the present invention provides a battery comprising a positive electrode sheet, a first diaphragm, a negative electrode sheet, and a second diaphragm stacked in sequence; a positive electrode ear is provided on the positive electrode sheet, and a negative electrode ear is provided on the negative electrode sheet, and the positive electrode ear and the negative electrode ear are located on the same side along the height direction of the battery; along the thickness direction of the battery, the first diaphragm and the second diaphragm are provided on both sides of the negative electrode sheet; along the side close to the direction in which the positive electrode ear extends, the edge of the first diaphragm and the edge of the second diaphragm both exceed the edge of the negative electrode sheet to form a first edge; at least a portion of the first edge is connected to form a composite area, and at least a portion of the first edge is not connected And form a non-composite area; along the width direction of the battery, the composite area and the non-composite area are alternately arranged, and the non-composite area is arranged corresponding to the area where the positive electrode ear and the negative electrode ear are located; the battery includes an electrolyte, and the electrolyte includes a carboxylic acid ester organic solvent; the carboxylic acid ester organic solvent includes one or more of ethyl acetate, ethyl propionate, methyl acetate, propyl acetate, methyl propionate, methyl butyrate and ethyl butyrate; based on the mass of the electrolyte, the mass content A of the carboxylic acid ester organic solvent in the electrolyte is 7.5% to 60%; wherein the height direction, the width direction and the thickness direction of the battery are perpendicular to each other.

[0006] In an optional embodiment, along the width direction of the battery, the size of the non-recombined area is L1 mm, and the ratio L1 / A ranges from 20 to 160.

[0007] In an optional embodiment, tab glue is provided on the positive electrode sheet and the negative electrode tab; along the width direction of the battery, the size of the tab glue is L2, and the difference between L1 and L2 is: 0.8mm~2mm; wherein, the value range of L1 is 11mm~16mm, and the value range of L2 is 10mm~12mm; preferably, along the width direction of the battery, the non-composite area is located between two adjacent composite areas; along the width direction of the battery, the spacing between the tab glue and the adjacent composite area is L3, and the value range of L3 is 0.4mm~1mm.

[0008] In an optional embodiment, the negative electrode sheet includes a negative electrode active layer, and a plurality of grooves are spaced apart on the negative electrode active layer; along the height direction of the battery, at least some of the grooves are arranged opposite to the non-composite area; the groove width is W, and the value range of W is 50μm-200μm; the ratio of L1 / W is in the range of 55 to 280; and / or the groove depth is 5μm to 20μm; and / or the spacing between adjacent grooves is 1.2mm to 2.0mm.

[0009] In an optional embodiment, the battery includes a packaging shell; the ear glue includes an intermediate film layer and two surface film layers, and along the thickness direction of the battery, the two surface film layers are located on both sides of the intermediate film layer; of the two surface film layers, one is connected to the positive ear or the negative ear, and the other is connected to the packaging shell; the melting point of the surface film layer is 95°C to 130°C, and the melting point of the intermediate film layer is 130°C to 160°C.

[0010] In an optional embodiment, along the side away from the extension direction of the positive electrode ear, the edge of the first diaphragm and the edge of the second diaphragm both extend beyond the edge of the negative electrode sheet to form a second edge; the length of the first edge extending beyond the negative electrode sheet is X1 mm, and the length of the second edge protruding from the negative electrode sheet is X2 mm, X1>X2; wherein the value range of X1 is 1.5 mm to 3 mm; and / or the value range of X2 is 0.5 mm to 1.8 mm.

[0011] In an optional embodiment, the first edge includes a plurality of first edge portions and a plurality of second edge portions, and the first edge portions and the second edge portions are alternately arranged along the length direction of the first diaphragm; the first edge portion is located in the composite area, and the second edge portion is located in the non-composite area; the length direction of the first diaphragm is perpendicular to the height direction of the battery; the plurality of first edge portions are bent toward the direction close to the negative electrode sheet, and in the thickness direction of the battery, at least part of the structure of two adjacent first edge portions is stacked and connected; along the side close to the extending direction of the negative electrode ear, the length of the first edge portion exceeding the edge of the negative electrode sheet is X3 mm, and the length of the second edge portion exceeding the edge of the negative electrode sheet is X4 mm; X4>X3; and / or, the difference range between X4 and X3 is: 0.2mm~0.6mm; wherein, the value range of X3 is 0.9mm~2.6mm, and the value range of X4 is 1.5mm~3mm.

[0012] In an optional embodiment, the first diaphragm and / or the second diaphragm is placed in a hot box environment at 130°C for 1H, and the thermal shrinkage rate along the height direction of the battery is η; the ratio range of η / X4 is 0.005~0.02; preferably, the value range of η is 1.5%~3%.

[0013] In an optional embodiment, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer, the negative electrode active layer being disposed on the surface of the negative electrode current collector; the negative electrode active layer includes a silicon-based material, the mass content of silicon element in the negative electrode active layer is B, and the value range of B is 1.5% to 50%; along the thickness direction of the battery, the peel strength between two adjacent first edge portions is FN / cm, and the value range of F is 0.02N / cm to 0.045N / cm;

[0014] Among them, the B / F ratio ranges from 0.33 to 25.

[0015] In a second aspect, the present invention further provides an electrical device comprising the above-mentioned battery.

[0016] The technical solution of the present invention forms alternating composite and non-composite regions on the side of the battery near the direction of extension of the positive electrode tab using the first edge of the diaphragm, and rationally adjusts the content of the carboxylate organic solvent in the electrolyte, thereby improving both the safety performance of the battery under high-temperature environments and the electrolyte infiltration effect. On the one hand, the connection between the diaphragms in the composite region forms a physical protective barrier, effectively suppressing the risk of positive and negative electrode contact caused by thermal shrinkage of the diaphragm under extreme working conditions, fundamentally blocking the triggering path of the thermal runaway chain reaction, and reducing thermal runaway phenomena such as explosion caused by positive and negative electrode short circuit contact caused by diaphragm shrinkage during furnace temperature testing, thereby improving battery safety. On the other hand, the lack of connection between the diaphragms in the non-composite region is used to reserve an infiltration channel for the electrolyte, and the viscosity of the carboxylate organic solvent is relatively low. By rationally controlling the content of the carboxylate organic solvent in the electrolyte, the fluidity of the electrolyte can be improved, allowing the electrolyte to fully infiltrate the electrode layers through the infiltration channel formed by the non-composite region, improving the infiltration effect, ensuring the intercalation and deintercalation of lithium ions, and thus ensuring the performance of the battery. Furthermore, during furnace temperature testing, since the positive and negative tabs, as the battery terminals, have higher thermal conductivity, the electrolyte near the positive and negative tabs undergoes side reactions at high temperatures, leading to a greater risk of heat and gas production. This solution establishes non-composite zones at the corresponding locations of the positive and negative tabs. These zones serve as channels for heat transfer and gas circulation, preventing internal heat from accumulating in the tabs and potentially causing more severe thermal runaway or short circuit risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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.

[0018] Figure 1 This is a schematic structural diagram of an electrode assembly according to an embodiment of the present invention before a hot blanching process is performed;

[0019] Figure 2 for Figure 1 A schematic diagram of a local cross section along the height direction of the battery;

[0020] Figure 3 This is a schematic structural diagram of an electrode assembly according to an embodiment of the present invention after a hot blanching process;

[0021] Figure 4 for Figure 3 Schematic diagram of a local cross section along the height direction of the battery at the middle composite area;

[0022] Figure 5 for Figure 3 Schematic diagram of a local cross section along the height direction of the battery at the mid-African composite area;

[0023] Figure 6 for Figure 3 A schematic structural diagram of an electrode assembly in a partially unfolded state;

[0024] Figure 7 Schematic diagram of the partial structure of a negative electrode sheet according to an embodiment;

[0025] Figure 8 A schematic diagram of the partial structure of a negative electrode sheet according to another embodiment;

[0026] Figure 9 Schematic diagram of the structure of the ear glue;

[0027] Figure 10 and Figure 11 A schematic diagram of a hot blanching process for an electrode assembly according to the present invention;

[0028] Figure 12 This is a schematic structural diagram of another electrode assembly according to an embodiment of the present invention before and after the hot stamping process.

[0029] Description of reference numerals:

[0030] 10. Electrode assembly; 1. Positive electrode sheet; 2. Positive tab; 3. Negative electrode sheet; 31. Negative active layer; 311. Groove; 4. Negative tab; 5. Separator; 5a. First separator; 5b. Second separator; 51. First edge; 511. Composite region; 512. Non-composite region; 513. First edge portion; 514. Second edge portion; 52. Second edge; 6. Tab glue; 611. Intermediate film layer; 612. Surface film layer; 7. First hot plate; 71. First airtight zone; 8. Second hot plate; 81. Second airtight zone;

[0031] X, battery height direction; Y, battery width direction; T, battery thickness direction; R, first diaphragm length direction. DETAILED DESCRIPTION

[0032] 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.

[0033] The following combination Figures 1 to 12 , describing embodiments of the present invention.

[0034] According to an embodiment of the present invention, on the one hand, a battery is provided, such as Figure 1-Figure 5 As shown, the battery has a battery height direction X, a battery width direction Y, and a battery thickness direction T, which are mutually perpendicular. The battery includes an electrode assembly 10, a packaging shell, and an electrolyte. The packaging shell has a receiving cavity formed therein, and the electrode assembly 10 and the electrolyte are encapsulated in the receiving cavity of the packaging shell.

[0035] Furthermore, the electrode assembly 10 includes a positive electrode sheet 1, a negative electrode sheet 3 and a separator 5 stacked in sequence, wherein the separator 5 includes a first separator 5a and a second separator 5b. A positive electrode tab 2 is provided on the positive electrode sheet 1, and a negative electrode tab 4 is provided on the negative electrode sheet 3. The positive electrode tab 2 and the negative electrode tab 4 are located on the same side along the battery height direction X. Figure 2 As shown, along the battery thickness direction T, the first separator 5a and the second separator 5b are arranged on both sides of the negative electrode sheet 3. Along the side close to the extension direction of the positive electrode tab 2, the edge of the first separator 5a and the edge of the second separator 5b both extend beyond the edge of the negative electrode sheet 3, forming a first edge 51. At least part of the first edge 51 is connected and forms a composite area 511, and at least part of the first edge 51 is unconnected and forms a non-composite area 512. Along the battery width direction Y, the composite areas 511 and the non-composite areas 512 are arranged alternately, and the non-composite areas 512 are arranged corresponding to the areas where the positive electrode tab 2 and the negative electrode tab 4 are located. It should be noted that the composite areas 511 and the non-composite areas 512 can be formed by a separator hot stamping process. Figure 1 and Figure 2 The schematic diagram of the structure of the electrode assembly 10 before the diaphragm hot stamping process is shown. Figure 3-Figure 5 A schematic diagram of the structure of the electrode assembly 10 after the diaphragm hot stamping process is shown.

[0036] It is understandable that the electrode assembly 10 of the present invention may be a wound structure (eg Figure 1 As shown), it can also be a laminated structure (as shown Figure 12 As shown in FIG, the present application does not impose any specific limitation on this, as long as the above-mentioned composite area 511 and non-composite area 512 can be formed.

[0037] Furthermore, the battery includes an electrolyte, which includes a carboxylate organic solvent. The carboxylate organic solvent includes one or more of ethyl acetate, ethyl propionate, methyl acetate, propyl acetate, methyl propionate, methyl butyrate, and ethyl butyrate. The mass content A of the carboxylate organic solvent in the electrolyte is 7.5% to 60%, based on the mass of the electrolyte.

[0038] For example, A can be 7.5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc.

[0039] In this embodiment, by utilizing the first edge 51 of the diaphragm 5 on the side of the battery close to the extension direction of the positive electrode ear 2 to form alternatingly distributed composite areas 511 and non-composite areas 512, and reasonably setting the content of the carboxylic acid ester organic solvent in the electrolyte, the safety performance of the battery in a high temperature environment and the electrolyte infiltration effect are both improved: on the one hand, the connection between the diaphragms 5 in the composite area 511 is utilized to form a physical protective barrier, which effectively suppresses the risk of positive and negative electrode contact caused by thermal shrinkage of the diaphragm 5 under extreme working conditions, fundamentally blocks the triggering path of the thermal runaway chain reaction, and improves the safety of the battery; on the other hand, the non-composite area 512 is utilized to reserve an infiltration channel for the electrolyte, and the carboxylic acid ester organic solvent has a low viscosity. By rationally controlling the content of carboxylic acid ester organic solvents in the electrolyte, the fluidity of the electrolyte can be improved, so that the electrolyte can fully penetrate the electrode layers through the infiltration channel formed by the non-composite area 512, improve the infiltration effect, ensure the deintercalation of lithium ions, and thus ensure the battery cycle performance; at the same time, improving the infiltration effect of the electrolyte can reduce the migration resistance of electrons and reduce the internal resistance of the battery. In addition, during the furnace temperature test, since the positive electrode ear 2 and the negative electrode ear 4 are the battery lead terminals and have a higher thermal conductivity, the electrolyte near the positive electrode ear 2 and the negative electrode ear 4 will undergo side reactions at high temperatures, resulting in a greater risk of heat and gas production. This solution sets a non-composite area 512 at the corresponding positions of the positive electrode ear 2 and the negative electrode ear 4. The non-composite area 512 can serve as a channel for heat transfer and gas circulation, preventing the internal heat of the battery from accumulating at the electrode position, thereby causing a more serious risk of thermal runaway or short circuit. In addition, the composite area 511 can be formed by a hot stamping process. Through the precise corresponding design of the non-composite area 512 and the tab area, interference between the hot stamping block and the tab during the hot stamping process can be avoided, thereby simplifying the processing technology and improving production efficiency.

[0040] In some embodiments, along the cell width direction Y, the size of the non-recombined region 512 is L1 mm, and the ratio L1 / A ranges from 20 to 160. For example, the ratio L1 / A can be 20, 25, 30, 35, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 135, 140, 145, 150, 155, 160, etc.

[0041] In a high-temperature environment, the low-boiling-point solvent portion of the electrolyte is easily volatilized into gas, and the side reactions increase, causing the organic and inorganic components in the SEI (SEI Solid Electrolyte Interface, negative electrode electrolyte interface membrane) and CEI (Cathode Electrolyte Interface, positive electrode electrolyte interface membrane) to decompose and generate heat, further heating up and releasing high-temperature gases; especially for the silicon-doped negative electrode, the unstable SEI decomposition and heat generation are more serious. Among them, the non-composite area 512 can serve as a channel for heat transfer and gas-liquid circulation, preventing the accumulation of heat inside the battery from being unable to dissipate heat in time, thereby improving the safety performance of the battery. In this embodiment, by reasonably controlling the ratio of L1 / A, it is possible to ensure that the non-composite area 512 is of sufficient size to provide the battery with a channel for heat transfer and gas-liquid circulation, thereby improving the safety performance of the battery; it is also possible to reduce the occurrence of gas production while improving the infiltration effect of the electrolyte, ensuring the deintercalation of lithium ions, reducing the internal resistance of the battery, and thereby improving the cycle performance of the battery. If the ratio of L1 / A is too large, A is too small relative to L1, the content of low-viscosity carboxylic acid ester organic solvent in the electrolyte is small, the electrolyte fluidity and its wetting effect and wetting speed on the electrode assembly 10 are poor, the electrode assembly 10 cannot be well wetted, thereby reducing the cycle performance of the battery and increasing the internal resistance of the battery; if the ratio of L1 / A is too small, L1 is too small relative to A. Although it can effectively improve the wettability, excessive addition of carboxylic acid ester organic solvent will reduce the starting temperature of the thermal stability of the entire electrolyte, making it more likely to volatilize, decompose or even burn at high temperatures, increasing the risk of thermal runaway of the battery under high temperature or abuse conditions. At the same time, the electrolyte is more likely to accelerate decomposition at high temperatures to produce a large amount of high-temperature gas, which cannot be discharged through the non-composite area 512 in time, causing deformation of the electrode and even thermal runaway problems.

[0042] The present invention does not impose any specific restrictions on the number of composite regions 511 and non-composite regions 512, as long as they can improve battery safety and electrolyte wetting. It is understood that one, two, three, or more composite regions 511 can be provided; and one, two, three, or more non-composite regions 512 can also be provided. In this embodiment, the dimension L1 of the non-composite region 512 along the battery width direction Y specifically refers to one non-composite dimension.

[0043] For example, Figure 1 and Figure 3As shown, there are three composite regions 511 and two non-composite regions. Two non-composite regions 512 are provided around the positive tab 2 and the negative tab 4, respectively, corresponding to the areas where the positive tab 2 and the negative tab 4 are located. Along the width of the battery, the three composite regions 511 are located between the positive tab 2 and the negative tab 4, and on either side of the positive tab 2 and the negative tab 4, respectively. L1 can refer to the size of the non-composite region 512 surrounding the positive tab 2 along the battery width direction Y; it can also refer to the size of the non-composite region 512 surrounding the negative tab 4 along the battery width direction Y.

[0044] Furthermore, in some embodiments, Figure 3 As shown, the positive electrode sheet 1 and the negative electrode tab 4 are provided with tab glue 6. The non-composite area 512 is provided corresponding to the area where the tab is located, more specifically, corresponding to the area where the tab glue 6 is located.

[0045] Along the battery width direction Y, the dimension of the tab glue 6 is L2, and the difference between L1 and L2 ranges from 0.8 mm to 2 mm. For example, the difference between L1 and L2 can be 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, etc.

[0046] It is understood that at least part of the structure of the tabs (positive tab 2 and negative tab 4) extends outside the packaging shell, and the tab glue 6 is bonded between the tabs and the packaging shell to ensure the sealing of the electrode assembly 10 within the packaging shell. Tab glue 6 is provided on both the positive tab 2 and the negative tab 4. In this embodiment, L2 can refer to the dimension of the tab glue 6 provided on the positive tab 2 along the battery width direction Y, or it can refer to the dimension of the tab glue 6 provided on the negative tab 4 along the battery width direction Y.

[0047] The value range of L1 is 11 mm to 16 mm, preferably 12.8 mm to 14 mm. For example, L1 can be 11 mm, 11.4 mm, 11.8 mm, 12 mm, 12.4 mm, 12.8 mm, 13 mm, 13.4 mm, 13.8 mm, 14 mm, 14.4 mm, 14.8 mm, 15 mm, 15.4 mm, 15.8 mm, 16 mm, etc.

[0048] The value range of L2 is 10 mm to 12 mm. For example, L2 can be 10 mm, 10.2 mm, 10.4 mm, 10.6 mm, 10.8 mm, 11 mm, 11.2 mm, 11.4 mm, 11.6 mm, 11.8 mm, 12 mm, etc.

[0049] In this embodiment, by rationally controlling the dimensions of L1 and L2 and their difference, both battery safety in high-temperature environments and electrolyte wetting are further balanced, thereby improving overall battery performance. If the difference between L1 and L2 is greater than 2 mm, L1 is too large, resulting in a too-small size for the composite region 511. This makes it difficult to effectively mitigate the risk of short circuits caused by separator 5 shrinkage in extreme conditions, making it difficult to ensure battery safety. If the difference between L1 and L2 is less than 0.8 mm, L1 is too small, and the non-composite region 512 provides a narrow channel for electrolyte wetting, reducing the wetting effect. It is understandable that during the hot-scalding process of the separator 5, the composite region 511 is formed by heating and pressurizing a hot-scalding block. If the difference between L1 and L2 is less than 0.8 mm, the distance between the composite region 511 and the tab glue 6 in the battery width direction Y is too small, increasing the difficulty of process control. During the hot-scalding process, the gap between the hot-scalding block and the tab glue 6 is too small, which can damage the tab glue 6 and reduce the battery's sealing performance.

[0050] Preferably, in some embodiments, Figure 1 As shown, along the width direction of the battery, the non-recombined area 512 is located between two adjacent composite areas 511. Along the width direction of the battery, the distance between the tab glue 6 and the adjacent composite areas 511 is L3, and the value range of L3 is 0.4mm-1mm.

[0051] For example, L3 can be 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, 0.75mm, 0.8mm, 0.85mm, 0.9mm, 0.95mm, 1mm, etc.

[0052] It is understood that L3 can refer to the distance between the tab glue 6 provided on the positive tab 2 and the adjacent composite area 511, or it can refer to the distance between the tab glue 6 provided on the negative tab 4 and the adjacent composite area 511. More specifically, in the battery height direction X, the tab glue 6 falls within the non-composite area 512 on the plane where the non-composite area 512 is located. That is, in the battery width direction Y, the two sides of the non-composite area 512 respectively extend beyond the two sides of the tab glue 6, thereby forming the above-mentioned distance L3 between the tab glue 6 and the composite area 511.

[0053] In this embodiment, by further limiting the spacing between the tab glue 6 and the adjacent composite area 511 in the battery width direction Y, the difficulty of process control is further reduced, damage to the tab glue 6 during the hot stamping process is avoided, and the battery's sealing is ensured. In addition, by properly controlling the size of L3, a sufficiently large channel can be formed between the tab glue 6 and the composite area 511 to meet the requirements of heat transfer and gas and liquid discharge in high-temperature environments.

[0054] Furthermore, in some embodiments, in the battery thickness direction T and on the plane where the tab glue 6 is located, the portion where the projection of the first edge 51 overlaps with the tab glue 6 is a non-reinforced area 512. With this arrangement, in the battery thickness direction T, the non-reinforced area 512 can be opposite to the gaps between the electrode layers, providing an infiltration channel for the electrolyte, ensuring uniform electrolyte infiltration within the battery, and thereby ensuring battery capacity and cycle performance.

[0055] Furthermore, in some embodiments, Figure 7 and Figure 8 As shown, the negative electrode sheet 3 includes a negative electrode current collector and a negative electrode active layer 31 disposed on at least one surface of the negative electrode current collector. A plurality of grooves 311 are spaced apart on the negative electrode active layer 31. Along the battery height direction X, at least some of the grooves 311 are disposed opposite the non-recombined region 512.

[0056] The groove 311 has a width of W, which ranges from 50 μm to 200 μm, preferably from 30 μm to 130 μm, and more preferably from 70 μm to 90 μm. For example, W can be 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, etc. It is understood that by providing a groove 311 of a reasonable width, the groove 311 can provide a diffusion channel for the electrolyte, shorten the infiltration path, and thus accelerate the penetration of the electrolyte into the interior of the electrode, reduce the infiltration time, and improve the infiltration uniformity, thereby compensating for the effect of the recombination area 511 on the electrolyte infiltration effect.

[0057] Furthermore, the ratio of L1 / W ranges from 55 to 280, preferably from 142 to 200. For example, the ratio of L1 / W can be 55, 60, 70, 80, 90, 100, 110, 120, 130, 140, 142, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, etc.

[0058] It is understandable that when calculating the ratio L1 / W, L1 and W should be converted into the same measurement unit, such as millimeters or micrometers.

[0059] In this embodiment, by setting the groove 311 and reasonably controlling the ratio of L1 / W, the electrolyte infiltration speed and uniformity can be improved, and the electrolyte infiltration effect can be further improved. If the ratio of L1 / W is less than 55, W is too large, that is, the width of the groove 311 is too large, which will weaken the connection strength between the negative electrode active layer 31 and the negative electrode current collector, causing the negative electrode active layer 31 to fall off; the falling off of the negative electrode active layer 31 will destroy the contact interface between the active material and the current collector, resulting in an increase in the internal resistance of the battery and poor cycle performance. If the ratio of L1 / W is greater than 200, W is too small relative to L1, that is, the width of the groove 311 is too small, which will not be able to effectively guide the flow of the electrolyte, resulting in obstruction of ion transport, difficulty in ensuring the electrolyte infiltration speed and uniformity, and reduced infiltration effect. As mentioned above, poor electrolyte infiltration will affect the deintercalation and extraction of lithium ions, thereby reducing the battery cycle performance; and poor infiltration will increase the migration resistance of electrons, causing the internal resistance of the battery to increase.

[0060] Furthermore, in some embodiments, the groove 311 has a depth of 5 μm to 20 μm, preferably 10 μm to 15 μm. For example, the groove 311 may have a depth of 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, etc. In this embodiment, a moderate groove depth can avoid the risk of peeling of the negative electrode active layer 31 due to excessive etching, while also preventing the problem of limited lateral diffusion of the electrolyte caused by insufficient groove depth. This improves the interlayer penetration efficiency of the electrolyte while maintaining the mechanical strength of the negative electrode sheet 3, ensuring wetting uniformity and reducing the risk of electrode sheet deformation.

[0061] Furthermore, in some embodiments, the spacing between adjacent grooves 311 is 1.2mm to 2.0mm, preferably 1.4mm to 1.8mm. For example, the spacing between adjacent grooves 311 can be 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2.0mm, etc. In this embodiment, the appropriate spacing between the grooves 311 can form a continuous electrolyte transmission network, avoiding the reduction in the bonding strength between the active layer and the current collector due to too small a spacing, and preventing the electrode from deforming due to local stress concentration; at the same time, it can avoid the obstruction of lateral diffusion of the electrolyte caused by excessive spacing, ensuring uniform infiltration of the electrolyte in the plane direction of the electrode.

[0062] For example, Figure 7As shown, multiple grooves 311 are spaced apart in the longitudinal direction of the negative electrode sheet 3, preferably evenly spaced apart. The longitudinal direction of the negative electrode sheet 3 is also the length direction R of the first separator, which is perpendicular to the battery height direction X. When the electrode assembly 10 formed by the negative electrode sheet 3, the positive electrode sheet 1, the first separator 5a, and the second separator 5b is a wound structure, the length direction R of the first separator is also the winding direction of the electrode assembly 10. When the electrode assembly 10 formed by the negative electrode sheet 3, the positive electrode sheet 1, the first separator 5a, and the second separator 5b is a stacked structure, the length direction R of the first separator is also the battery width direction Y.

[0063] For example, Figure 8 As shown, among the multiple grooves 311, some grooves 311 are spaced apart in the length direction of the negative electrode sheet 3, preferably evenly spaced apart; some grooves 311 are spaced apart in the battery height direction X, preferably evenly spaced apart, to form a grid structure together.

[0064] Alternatively, in some embodiments not shown in the figures, the groove 311 may also be arranged at an acute angle to the height direction X of the battery, such as an angle of 30°, 45°, 60°, etc.

[0065] The groove 311 of the present invention can be formed by a laser scribing process. In some embodiments, the groove 311 can be set only in the area of ​​the negative electrode sheet 3 corresponding to the non-recombined area 512; or the groove 311 can be set in the area of ​​the negative electrode sheet 3 corresponding to the non-recombined area 512, and the groove 311 can be set in the area of ​​the negative electrode sheet 3 corresponding to the recombination area 511.

[0066] Furthermore, in some embodiments, Figure 9 As shown, the tab glue 6 includes an intermediate film layer 611 and two surface film layers 612. Along the thickness direction of the battery, the two surface film layers 612 are located on both sides of the intermediate film layer 611. Among them, one of the two surface film layers 612 is connected to the positive tab 2 or the negative tab 4, and the other is connected to the packaging shell.

[0067] The melting point of the surface film layer 612 is 95°C to 130°C. For example, the melting point of the surface film layer 612 can be 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, etc. The melting point of the middle film layer 611 is 130°C to 160°C. For example, the melting point of the middle film layer 611 can be 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, etc.

[0068] In this embodiment, the melting point range of the surface film layer 612 is relatively high, while the melting point range of the intermediate film layer 611 is relatively low. When the battery is in a high-temperature environment, the side reactions inside the battery at high temperatures produce a large amount of high-temperature and high-pressure gas. Compared with the intermediate film layer 611, the surface film layer 612 preferentially melts at a lower temperature, gradually weakening the sealing strength of the packaging shell and forming an exhaust channel at the pole ear; while the intermediate film layer 611 maintains structural support to prevent the connection between the packaging shell and the pole ear from completely breaking. At the same time, under the synergistic effect of the non-composite area 512, the high-pressure gas formed inside the electrode assembly 10 is directionally gathered to the exhaust channel formed by the melting of the pole ear glue 6, achieving precise pressure relief, so that heat and gas are discharged in a direction, avoiding the risk of heat spread caused by internal pressure out of control, thereby improving the high-temperature safety protection performance of the battery while ensuring the reliability of the seal.

[0069] It can be understood that the packaging shell is used to encapsulate the electrode assembly 10 and components such as the electrolyte. The packaging shell can be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite shell) or an aluminum-plastic film. For example, the packaging shell is an aluminum-plastic film, and the aluminum-plastic film has a top packaging edge near one end of the tab, and at least part of the structure of the positive tab 2 and the negative tab 4 extends from the top packaging edge. At the positive tab 2, the surface film layer 612 on one side of the tab glue 6 is bonded to the positive tab 2, and the surface film layer 612 on the other side is bonded to the top packaging edge. At the negative tab 4, the surface film layer 612 on one side of the tab glue 6 is bonded to the negative tab 4, and the surface film layer 612 on the other side is bonded to the top packaging edge.

[0070] Furthermore, when the battery is in a high-temperature environment, the temperature rise and deformation degree of various parts are different. Usually, the thermal conductivity coefficient at the pole ear is high, which makes the temperature rise and deformation of the end of the battery close to the pole ear faster, and the heat shrinkage at the first edge 51 is more serious, which makes it easier to cause contact short circuit problems between the positive electrode sheet 1 and the negative electrode sheet 3 due to the heat shrinkage of the diaphragm 5.

[0071] In some embodiments, as Figure 1-Figure 5 As shown, along the side away from the extending direction of the positive electrode tab 2, the edge of the first separator 5a and the edge of the second separator 5b both exceed the edge of the negative electrode sheet 3 to form a second edge 52. Figure 2 As shown, the first edge 51 protrudes from the negative electrode sheet 3 by a length of X1 mm, and the second edge 52 protrudes from the negative electrode sheet 3 by a length of X2 mm, where X1>X2.

[0072] The value range of X1 is 1.5 mm to 3 mm, for example, it can be 1.5 mm, 1.7 mm, 1.9 mm, 2.1 mm, 2.3 mm, 2.5 mm, 2.7 mm, 3 mm, etc.

[0073] Among them, the value range of X2 is 0.5mm~1.8mm, for example, it can be 0.5mm, 0.7mm, 0.9mm, 1mm, 1.1mm, 1.3mm, 1.5mm, 1.7mm, 1.8mm, etc.

[0074] It should be noted that, in this embodiment, X1 and X2 specifically refer to the dimensions of the first edge 51 and the second edge 52 along the height direction X of the battery before the hot stamping process.

[0075] In this embodiment, by making X1>X2, that is, on the side of the battery close to the tab, the length of the first edge 51 extending beyond the negative electrode sheet 3 is widened, thereby alleviating the contact short circuit problem between the positive electrode sheet 1 and the negative electrode sheet 3 caused by the thermal shrinkage of the diaphragm 5, improving thermal runaway, and improving the safety performance of the battery in a high temperature environment.

[0076] Furthermore, in a high-temperature environment, the second edge 52 is less likely to deform significantly, and therefore, the second edge 52 may not be connected, allowing the electrolyte to directly enter the interlayer through the second edge 52 to achieve infiltration. Of course, in some embodiments not shown in the figures, the second edge 52 may also adopt the same structure as the first edge 51, that is, providing recombination areas 511 and non-recombination areas 512 alternately arranged along the battery width direction Y, and the present invention is not specifically limited to this.

[0077] More specifically, in some embodiments, the first edge 51 includes a plurality of first edge portions 513 and a plurality of second edge portions 514. The first edge portions 513 and the second edge portions 514 are alternately arranged along the length direction R of the first separator. The first edge portions 513 are located in the composite region 511, and the second edge portions 514 are located in the non-composite region 512. The length direction of the first separator 5a is perpendicular to the height direction of the battery.

[0078] Furthermore, multiple first edge portions 513 are bent toward the negative electrode sheet 3. In the thickness direction of the battery, at least portions of two adjacent first edge portions 513 are stacked and connected. Along the side proximal to the direction in which the negative electrode tab 4 extends, the first edge portion 513 protrudes from the edge of the negative electrode sheet 3 by a length of X3 mm, and the second edge portion 514 protrudes from the edge of the negative electrode sheet 3 by a length of X4 mm.

[0079] It should be noted that, in this embodiment, X3 and X4 specifically refer to the dimensions of the first edge portion 513 and the second edge portion 514 along the battery height direction X when the first separator 5a and the second separator 5b are in the unfolded state after the hot stamping process.

[0080] Since the first edge portion 513 shrinks during the hot ironing process, the dimension X3 of the first edge portion 513 is smaller than X4. Specifically, the value range of X3 is 0.9 mm to 2.6 mm, for example, 0.9 mm, 1 mm, 1.1 mm, 1.3 mm, 1.5 mm, 1.7 mm, 1.9 mm, 2.1 mm, 2.3 mm, 2.5 mm, 2.6 mm, etc.

[0081] Since the second edge portion 514 is not subjected to hot stamping, the dimension X4 of the second edge portion 514 is equal to X1. The value range of X4 is 1.5 mm to 3 mm, for example, 1.5 mm, 1.7 mm, 1.9 mm, 2.1 mm, 2.3 mm, 2.5 mm, 2.7 mm, 3 mm, etc.

[0082] Furthermore, in some embodiments, the difference between X4 and X3 ranges from 0.2 mm to 0.6 mm. For example, the difference between X4 and X3 can be 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, etc.

[0083] In this embodiment, the difference between X4 and X3 is caused by the shrinkage of the first edge portion 513 after the blanching process. If the difference between X4 and X3 is less than 0.2 mm, the shrinkage of the first edge portion 513 during the blanching process is too small. In this case, the first edge portion 513 is not fully heated, and the bonding strength between adjacent first edge portions 513 is insufficient. In a high-temperature environment, the first edge portion 513 is easily separated from the adjacent first edge portion 513 during shrinkage, and there is still a risk of contact and short circuit between the positive electrode sheet 1 and the negative electrode sheet 3 due to the shrinkage of the separator 5. If the difference between X4 and X3 is greater than 0.6 mm, the shrinkage of the first edge portion 513 during the blanching process is too large, that is, X3 is too small. In a high-temperature environment, the first edge portion 513 will further shrink, and there is a risk that the first edge portion 513 will not cover the positive electrode sheet 1 and the negative electrode sheet 3 in the direction near the protruding tab, which increases the risk of contact and short circuit between the positive electrode sheet 1 and the negative electrode sheet 3. Therefore, this embodiment reasonably controls the difference between X4 and X3, balances the connection strength between the first edge portions 513 and the length of the first edge portions 513, ensures the effectiveness of the setting of the composite area 511, and effectively alleviates the risk of contact short circuit between the positive electrode sheet 1 and the negative electrode sheet 3 caused by the shrinkage of the diaphragm 5.

[0084] Specifically, by properly controlling the blanching temperature and time during the blanching process, the size of X3 can be adjusted, thereby adjusting the difference between X4 and X3. For example, the blanching temperature can be 120°C to 140°C, preferably 130°C to 135°C. For example, the blanching time can be 1 to 3 seconds, preferably 1.5 to 2.5 seconds.

[0085] Furthermore, the degree of thermal shrinkage of the separator 5 is a key factor affecting the safety performance of the battery in high-temperature environments. To ensure that the separator 5 can still effectively block the positive electrode sheet 1 and the negative electrode sheet 3 after experiencing thermal shrinkage and misalignment caused by electrode deformation in high-temperature environments, in some embodiments, the first separator 5a and / or the second separator 5b are placed in a 130°C hot box for 1 hour, and the thermal shrinkage rate along the height direction of the battery is η. The ratio η / X4 ranges from 0.005 to 0.02, for example, the ratio η / X4 can be 0.005, 0.007, 0.01, 0.012, 0.015, 0.017, 0.02, etc. Preferably, the value of η ranges from 1.5% to 3%, for example, 1.5%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 2.9%, 3%, etc.

[0086] In this embodiment, by reasonably controlling the ratio of η / X4, the first diaphragm 5a and / or the second diaphragm 5b still have sufficient margin after thermal shrinkage in a high temperature environment to isolate the positive electrode sheet 1 and the negative electrode sheet 3, thereby preventing the positive electrode sheet 1 and the negative electrode sheet 3 from contacting and causing a short circuit, thereby improving the safety performance of the battery in a high temperature environment. If the ratio of η / X4 is less than 0.005, then X4 is too small relative to η. In a high temperature environment, the margin of the diaphragm 5 after shrinkage is small, and the diaphragm 5 cannot fully block the positive electrode sheet 1 and the negative electrode sheet 3. Or, after the electrode sheet is deformed or misaligned due to impact, high temperature, etc., the diaphragm 5 cannot isolate the positive electrode sheet 1 and the negative electrode sheet 3, making it difficult to effectively ensure the safety performance of the battery in a high temperature environment. If the ratio of η / X4 is greater than 0.02, then X4 is too large relative to η, which easily causes interference between the diaphragm 5 and the aluminum-plastic film in the process, resulting in the risk of false seal leakage, making it difficult to ensure the safety performance of the battery in a high temperature environment.

[0087] Furthermore, the negative electrode active layer 31 of the negative electrode sheet 3 comprises a silicon-based material and a graphite material. The silicon-based material includes at least one of a silicon-carbon composite material and a silicon-oxygen composite material. Because silicon materials experience significantly greater volume expansion than graphite materials during charge and discharge, the higher the silicon content in the negative electrode active layer 31, the greater the volume expansion of the negative electrode sheet 3 during charge and discharge. Furthermore, regions of the negative electrode sheet 3 with higher silicon content experience greater expansion and deformation during battery cycling. Therefore, a higher silicon content in the negative electrode active layer 31 increases the susceptibility of the negative electrode sheet 3 to local deformation, which in turn can lead to overall structural instability. Furthermore, near the end of the battery where the tab protrudes, the negative electrode sheet 3 is more susceptible to deformation due to the faster temperature rise near the tab and more intense side reactions. Deformation or expansion during cycling can easily stretch the first edge portion 513 of the composite region 511, impacting the isolation performance of the separator 5 and creating the risk of short circuiting between the positive and negative electrode sheets 1 and 3.

[0088] To solve this technical problem, in some embodiments, the mass content of silicon in the negative electrode active layer 31 is B, and the value range of B is 1.5% to 50%. For example, B can be 1.5%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.

[0089] Furthermore, along the battery thickness direction T, the peel strength between two adjacent first edge portions 513 is FN / cm, and the value range of F is 0.02N / cm to 0.045N / cm. For example, F can be 0.02N / cm, 0.025N / cm, 0.03N / cm, 0.035N / cm, 0.04N / cm, 0.045N / cm, etc.

[0090] The B / F ratio ranges from 0.33 to 25. For example, the B / F ratio can be 0.33, 0.5, 1, 2, 3, 5, 7, 9, 13, 15, 18, 20, 21, 22, 23, 24, 25, etc.

[0091] In this embodiment, by properly controlling the B / F ratio, the expansion effect of the silicon-based material and the stability of the electrode structure can be balanced. When B / F is within a reasonable range, the silicon-based material can be used to improve the battery energy density, while the appropriate peel strength can be used to alleviate the local stress concentration caused by silicon expansion, preventing excessive deformation of the electrode from stretching the first edge portion 513 of the composite region 511. This maintains the isolation performance of the separator 5, reduces the risk of contact short circuit between the positive and negative electrode sheets 3, and ensures the safety performance of the battery in high-temperature environments. If B / F is less than 0.33, B is too small relative to F, that is, the silicon content is too low, making it difficult to effectively improve the battery energy density. When F is large, the electrolyte is more difficult to penetrate, affecting the battery's cycle retention rate. If B / F is greater than 25, B is too large relative to F, that is, the silicon content is too high, and the bonding force between the first edge portion 513 is insufficient to cope with the expansion of the negative electrode sheet 3, which can easily stretch the first edge portion 513 of the composite region 511, causing contact short circuit between the positive electrode sheet 1 and the negative electrode sheet 3, making it difficult to ensure the safety performance of the battery in high-temperature environments.

[0092] Furthermore, in some embodiments, the negative electrode active layer 31 adopts a double-layer coating structure, specifically including a bottom layer close to the negative electrode current collector and a surface layer covering the bottom layer. Among them, the bottom layer is made of high-stability graphite material mixed with silicon negative electrode. This design can effectively cope with the volume changes of the silicon negative electrode during the charging and discharging process, reduce damage to the negative electrode structure, and ensure the stability of the battery. The surface layer adopts small-particle size, high specific surface area graphite material mixed with silicon negative electrode. This material can support higher charge and discharge rates and meet fast charging requirements. Through this double-layer structure design, the negative electrode active layer 31 can take into account the fast charging performance of the silicon-doped negative electrode and the need to reduce expansion and deformation, thereby ensuring the isolation effect of the composite area 511 and improving the overall performance of the battery.

[0093] like Figure 10 and Figure 11 As shown, the blanching process of the present invention is as follows:

[0094] Blanching steps: Figure 10 According to the set blanching temperature and blanching time, the first edge 51 is blanched using the first blanching block 7. The first blanching block 7 has a blanching area and a first avoidance area 71. The blanching area corresponds to the laminating area 511, and the first avoidance area 71 corresponds to the non-laminating area 512.

[0095] Leveling steps: Figure 11 The first edge 51 is flattened using the second ironing block 8 according to the set flattening temperature. The second ironing block 8 has a flattening area and a second avoidance area 81, which corresponds to the composite area 511 and the non-composite area 512. The second avoidance area 81 is disposed around the tab glue 6 and a certain distance is reserved between the tab glue 6, which can be 0.4 mm to 1 mm, to avoid damaging the tab glue 6. The flattening temperature can be 80°C to 95°C.

[0096] During the blanching step, the first edge portion 513 located in the composite zone 511 is pre-shrunk and squeezed. Figure 2 The upright state shown in FIG. Figure 4 As shown in the figure, the two edges of the non-composite portion are overlapped, bonded and covered on the top of the negative electrode sheet 3. Figure 2 The upright state shown in FIG. Figure 5 In the flattening step, the second ironing block 8 further presses down and shapes the second edge portion 514, allowing it to lay flatter on top of the negative electrode sheet 3. This facilitates packaging of the electrode assembly 10 within the packaging can, avoiding the risk of leaks caused by interference with the packaging due to the second edge portion 514.

[0097] Of course, in some cases, after the hot stamping step, the state of the second edge portion 514 does not interfere with the packaging, and the flattening step can be omitted.

[0098] According to another aspect of an embodiment of the present invention, an electrical device is provided, comprising the battery described in any of the above embodiments. The electrical device of the present invention comprises the battery of the present invention, and thus has the same technical effects as the battery of the present invention, which will not be described in detail here.

[0099] The electrical equipment of the present invention can be any device that uses a battery. For example, the electrical equipment can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, and the like. The vehicle can be a fuel vehicle, a gas vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, and the like; the spacecraft includes airplanes, rockets, space shuttles, and spacecraft, and the like; the electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like; the electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, and the like. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical equipment.

[0100] Example

[0101] Example 1

[0102] Method for preparing lithium-ion battery

[0103] 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, fluid positive electrode active slurry. The positive electrode active slurry is then coated on the surface of aluminum foil, baked, rolled, and slit to produce a positive electrode sheet 1.

[0104] Step 2: Graphite (graphite blended with silicon and carbon, with a silicon content of 10%), conductive carbon black (Super P), styrene-butadiene rubber, and carboxymethyl cellulose were mixed in deionized water at a weight ratio of 96:0.5:2:1.5. The mixture was continuously stirred in a blender to form a uniform, fluid negative electrode active slurry. The negative electrode active slurry was coated onto carbon-coated copper foil, and the negative electrode sheet 3 was obtained after baking, laser scribing, roller pressing, and slitting.

[0105] In this step, the mass content B of silicon element can be adjusted by adjusting the content of silicon carbon.

[0106] Step 3: Using laser scribing technology, a groove 311 is formed on the negative electrode active layer 31. The groove width W of the groove 311 can be adjusted by adjusting the laser power, spot diameter, scanning speed, etc.

[0107] Step 4: Use a 6.5μm thick separator 5 (including a first separator 5a and a second separator 5b) that is 3.2mm longer than the negative electrode sheet in the width direction. The separator 5 and the above-mentioned cut and prepared positive electrode sheet 1 and negative electrode sheet 3 are rolled into a wound structure battery cell.

[0108] In the wound cell, along the side of the negative electrode sheet 3 near the negative electrode tab 4, the length X1 of the separator 5 extending beyond the negative electrode sheet 3 is 2 mm. It can be understood that the value of X1 also corresponds to the value of X4. Along the side of the negative electrode sheet 3 away from the negative electrode tab 4, the length of the separator 5 extending beyond the negative electrode sheet 3 is 1.2 mm. In this step, the value of X4 can be adjusted by adjusting the width of the separator 5.

[0109] Among them, the diaphragm 5 includes a substrate layer and a ceramic layer and an adhesive layer covering the substrate layer. The thermal shrinkage rate of the diaphragm 5 can be adjusted to η by adjusting the type of the substrate layer and modifying or adjusting the thickness and content of the ceramic layer and the adhesive layer.

[0110] Step 5: Use the first hot block 7 to hot-scald the separator 5 on the side of the battery cell near the tab to form a composite area 511 and a non-composite area 512. The size L1 of the non-composite area 512 can be adjusted by adjusting the size of the first clearance area 71 of the first hot block 7 in the battery width direction Y.

[0111] The peeling strength F between two adjacent first edge portions 513 can be adjusted by controlling the blanching temperature and the blanching time.

[0112] Step 6: Use lithium hexafluorophosphate (LiPF6) with a concentration of 1M 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 a carboxylic acid ester solvent with a mass content of 20% (ethyl propionate (EP) and propyl propionate (PP) with a mass ratio of 1:1) as the non-aqueous organic solvent.

[0113] The mass content A of the carboxylate organic solvent in the electrolyte can be adjusted by adjusting the mass ratio of the carboxylate solvent.

[0114] Step 7: After hot pressing, packaging, liquid injection, chemical formation, and secondary sealing of the battery cell, a lithium-ion battery is obtained.

[0115] The lithium-ion batteries in the examples and comparative examples of the present application were prepared using the same method as in Example 1.

[0116] The following test methods were used for the various examples and comparative examples of the present application:

[0117] 1. Battery capacity test method: In a constant temperature test room at 25°C, discharge at a constant current of 0.2C to the lower limit voltage, let it stand for 5 minutes, charge at a constant current of 0.5C to the upper limit voltage, keep constant voltage until the current reaches 0.02C, then discharge at a constant current of 0.2C to the lower limit voltage, and record the discharge capacity.

[0118] 2. Battery oven temperature test method: At 25°C, discharge at a constant current of 0.2C to the lower voltage limit and allow to rest for 5 minutes. Charge at a constant current of 0.5C to the upper voltage limit and maintain constant voltage until the current drops to 0.02C. Place the fully charged battery in a hot box and heat at a rate of 5°C / min to 130°C, maintaining this temperature for 60 minutes. Test five batteries and record the percentage of batteries that pass at both 129°C and 130°C. If neither fire nor explosion occurs, the battery is considered to have passed. If fire or explosion occurs, the battery is considered to have failed.

[0119] 3. Battery retention rate test method: The battery was placed in a 45°C constant temperature test room for 1 hour to reach a constant temperature, then discharged at a constant current of 0.2C to the lower limit voltage; after standing for 5 minutes, it was charged at a constant current of 0.5C to the upper limit voltage of 4.53V, and then charged at a constant voltage until the current dropped to 0.02C. After standing for 5 minutes, it was discharged at a constant current of 0.2C to the lower limit voltage of 3V. The discharge capacity was recorded as the initial capacity (D0). The battery was step-charged in a 45°C constant temperature box: 3C constant current charged to 4.35V, 2.5C constant current charged to 4.35V, and then constant voltage charged until the current reached 1.8C; after charging at a constant current of 1.8C to 4.4V, it was charged at a constant voltage charged to 1.5C; after charging at a constant current of 1.5C to 4.5V, it was charged at a constant voltage charged to 1.2C; after charging at a constant current of 1.2C to 4.58V, it was charged at a constant voltage charged to 0.25C. After standing for 5 minutes, discharge at 0.7C to a lower voltage of 2.8V. Repeat the charge-discharge cycle until 800T. Record the discharge capacity at 800T (D1). The capacity retention rate is (D1 / D0) × 100%.

[0120] 4. Battery expansion rate test method: Measure the initial thickness of the battery (M0). After the battery has been cycled 800 times, measure the post-cycle thickness (M1). The expansion rate is (M1 / M0) × 100%.

[0121] 5. Battery internal resistance test method: Use an ACIR tester to apply a low-amplitude AC current signal (100Hz, 100mA) to the battery and measure the voltage response across the battery. Based on the voltage and current, use Ohm's law to calculate the internal resistance.

[0122] Among them, the testing method of each parameter in each embodiment and comparative example of the present application is:

[0123] 1. Test method for the content A of carboxylic acid ester organic solvents: Separate and quantitatively analyze the electrolyte sample using a gas chromatograph, gas chromatography-mass spectrometer, or liquid chromatograph. Determine the contents of EP and PP using the standard curve method. The sum of the contents of EP and PP is A.

[0124] 2. Diaphragm shrinkage rate η test method: Disassemble the battery cell, then cut a sample of standard size and record the original width of the sample (W0). Wash the removed diaphragm with DMC and dry it. Set the hot box temperature (130°C) and heating time (60min). Use a vernier caliper to measure the width after heating (W1). Shrinkage rate η = (W1 / W0) × 100%.

[0125] 3. Peel Strength F: Disassemble the battery and cut the two bonded separators in the composite region 511 into standard size. Using an electronic universal testing machine, secure one separator to a peeling fixture and the other separator to a tensile fixture, with the bonding direction perpendicular to the tensile direction. Start the tensile testing machine, identify the maximum force and stretching distance during the stretching process, and calculate the peel strength F.

[0126] 4. Test method for the mass content of silicon in the negative electrode active layer: 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, and use EDS point scanning mode to obtain the silicon content percentage of each silicon-based particle, 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 coating can be calculated from the percentage of silicon and the average silicon content of the silicon-based particles.

[0127] The differences between Comparative Examples 1 and 2 and Examples 1-17 are: the content A of the carboxylate organic solvent, the size L1 of the non-composite area 512, the groove width W of the groove 311, the thermal shrinkage rate η of the separator 5, the length X4 of the separator 5 extending beyond the negative electrode sheet 3, the silicon content B of the negative electrode sheet 3, and the peel strength F between the second edge portions 514 are different, as shown in the table below:

[0128]

[0129]

[0130] Combining the test results of Comparative Examples 1 and 2 and Examples 1-3, it can be seen that compared with Comparative Examples 1 and 2, Examples 1-3 have a high furnace temperature pass rate, a high capacity retention rate, and a low internal resistance. Therefore, it can be seen that setting the composite area 511 and the non-composite area 512 and reasonably controlling the content A of the carboxylic acid ester organic solvent in the electrolyte can take into account the improvement of the safety performance of the battery at high temperature and the electrolyte infiltration effect, thereby improving the cycle performance of the battery.

[0131] Combined with the test results of Examples 1-5, it can be seen that compared with Examples 4 and 5, Examples 1-3 have a high furnace temperature pass rate, a high capacity retention rate, and a low internal resistance. It can be seen that reasonable control of the L1 / A ratio can further improve the electrolyte infiltration effect while ensuring the safety and cycle performance of the battery at high temperatures.

[0132] Combined with the test results of Examples 6-9, it can be seen that compared with Examples 8 and 9, Examples 6 and 7 have high capacity retention rates and low internal resistance. Therefore, it can be seen that reasonable control of the L1 / W ratio can further improve the electrolyte infiltration effect and ensure the cycle performance of the battery.

[0133] Combined with the test results of Examples 10-13, it can be seen that compared with Examples 12 and 13, Examples 10 and 11 have higher furnace temperature pass rates. Therefore, it can be seen that reasonable control of the ratio η / X4 further improves the safety performance of the battery at high temperatures.

[0134] Combined with the test results of Examples 14-17, it can be seen that compared with Example 16, Examples 14 and 15 have a higher furnace temperature pass rate; compared with Example 17, Examples 14 and 15 have a higher capacity retention rate. It can be seen that reasonable control of the B / F ratio further improves the safety performance and cycle performance of the battery at high temperature.

[0135] 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: The battery comprises a positive electrode sheet (1), a first diaphragm (5a), a negative electrode sheet (3) and a second diaphragm (5b) stacked in sequence; the positive electrode sheet (1) is provided with a positive electrode ear (2), the negative electrode sheet (3) is provided with a negative electrode ear (4), the positive electrode ear (2) and the negative electrode ear (4) are located on the same side along the height direction (X) of the battery; along the thickness direction (T) of the battery, the first diaphragm (5a) and the second diaphragm (5b) are provided on both sides of the negative electrode sheet (3); along the side close to the extending direction of the positive electrode ear (2), the first diaphragm (5a) and the second diaphragm (5b) are provided on the side close to the extending direction of the positive electrode ear (2). The edge of the first diaphragm (5a) and the edge of the second diaphragm (5b) both extend beyond the edge of the negative electrode sheet (3) to form a first edge (51); at least a portion of the first edge (51) is connected to form a composite area (511), and at least a portion of the first edge (51) is not connected to form a non-composite area (512); along the width direction (Y) of the battery, the composite area (511) and the non-composite area (512) are alternately arranged, and the non-composite area (512) is arranged corresponding to the area where the positive electrode tab (2) and the negative electrode tab (4) are located; The battery includes an electrolyte, and the electrolyte includes a carboxylate organic solvent; the carboxylate organic solvent includes one or more of ethyl acetate, ethyl propionate, methyl acetate, propyl acetate, methyl propionate, methyl butyrate, and ethyl butyrate; Based on the mass of the electrolyte, the mass content A of the carboxylate organic solvent in the electrolyte is 7.5% to 60%; The battery height direction (X), the battery width direction (Y) and the battery thickness direction (T) are perpendicular to each other.

2. The battery according to claim 1, characterized in that Along the width direction (Y) of the battery, the size of the non-recombined area (512) is L1 mm, and the ratio L1 / A ranges from 20 to 160.

3. The battery according to claim 1, characterized in that The positive electrode sheet (1) and the negative electrode tab (4) are provided with tab glue (6); Along the width direction (Y) of the battery, the size of the tab glue (6) is L2, and the difference between L1 and L2 is in the range of 0.8 mm to 2 mm; Among them, the value range of L1 is 11mm~16mm, and the value range of L2 is 10mm~12mm; Preferably, along the width direction (Y) of the battery, the non-recombination area (512) is located between two adjacent composite areas (511); Along the width direction (Y) of the battery, the distance between the tab glue (6) and the adjacent composite area (511) is L3, and the value range of L3 is 0.4mm to 1mm.

4. The battery according to claim 3, characterized in that The negative electrode sheet (3) comprises a negative electrode active layer (31), and a plurality of grooves (311) are arranged at intervals on the negative electrode active layer (31); along the height direction (X) of the battery, at least some of the grooves (311) are arranged opposite to the non-composite area (512); The groove (311) has a groove width of W, with a value range of W being 50 μm to 200 μm; a ratio of L1 / W being 55 to 280; and / or, The groove (311) has a depth of 5 μm to 20 μm; and / or, The distance between adjacent grooves (311) is 1.2 mm to 2.0 mm.

5. The battery according to claim 3, characterized in that The battery includes a packaging shell; The tab glue (6) comprises an intermediate film layer (611) and two surface film layers (612), and along the thickness direction (T) of the battery, the two surface film layers (612) are located on both sides of the intermediate film layer (611); one of the two surface film layers (612) is connected to the positive tab (2) or the negative tab (4), and the other is connected to the packaging shell; The melting point of the surface film layer (612) is 95°C to 130°C, and the melting point of the intermediate film layer (611) is 130°C to 160°C.

6. The battery according to any one of claims 1 to 5, characterized in that Along a side away from the extending direction of the positive electrode tab (2), an edge of the first diaphragm (5a) and an edge of the second diaphragm (5b) both extend beyond the edge of the negative electrode sheet (3), forming a second edge (52); the length of the first edge (51) extending beyond the negative electrode sheet (3) is X1 mm, and the length of the second edge (52) extending beyond the negative electrode sheet (3) is X2 mm, where X1>X2; The value range of X1 is 1.5 mm to 3 mm; and / or the value range of X2 is 0.5 mm to 1.8 mm.

7. The battery according to any one of claims 1 to 5, characterized in that The first edge (51) includes a plurality of first edge portions (513) and a plurality of second edge portions (514), and the first edge portions (513) and the second edge portions (514) are alternately arranged along the length direction (R) of the first diaphragm (5a); the first edge portions (513) are located in the composite area (511), and the second edge portions (514) are located in the non-composite area (512); the length direction (R) of the first diaphragm (5a) is perpendicular to the height direction (X) of the battery; The plurality of first edge portions (513) are bent in a direction close to the negative electrode sheet (3), and in the thickness direction (T) of the battery, at least parts of the structures of two adjacent first edge portions (513) are stacked and bonded; Along the side close to the extending direction of the negative electrode ear (4), the length of the first edge portion (513) extending beyond the edge of the negative electrode sheet (3) is X3 mm; the length of the second edge portion (514) extending beyond the edge of the negative electrode sheet (3) is X4 mm, X4>X3; And / or, the difference between X4 and X3 is in the range of 0.2 mm to 0.6 mm; Among them, the value range of X3 is 0.9mm~2.6mm, and the value range of X4 is 1.5mm~3mm.

8. The battery according to claim 7, characterized in that The first diaphragm (5a) and / or the second diaphragm (5b) are placed in a hot box environment at 130°C for 1 hour, and the thermal shrinkage rate along the height direction (X) of the battery is η; the ratio η / X4 ranges from 0.005 to 0.02; Preferably, the value range of η is 1.5% to 3%.

9. The battery according to claim 7, characterized in that The negative electrode sheet (3) comprises a negative electrode current collector and a negative electrode active layer (31), wherein the negative electrode active layer (31) is arranged on the surface of the negative electrode current collector; The negative electrode active layer (31) comprises a silicon-based material, the mass content of silicon in the negative electrode active layer (31) is B, and the value range of B is 1.5% to 50%; Along the thickness direction (T) of the battery, the peel strength between two adjacent first edge portions (513) is FN / cm, and the value range of F is 0.02N / cm to 0.045N / cm; Among them, the B / F ratio ranges from 0.33 to 25.

10. An electrical device, characterized in that: include: The battery according to any one of claims 1 to 9.

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