Battery cell, battery device, and electric device

Abstract

The application provides a battery monomer, a battery device and a power utilization device, comprising an electrode assembly, an electrolyte and a shell, the electrode assembly is accommodated in the shell, the material of the shell is a soft package material; the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator, the positive electrode sheet and the negative electrode sheet are alternately stacked, and the separator is arranged between adjacent positive electrode sheets and negative electrode sheets; the four sides of the negative electrode sheet are provided with chamfers; the projection of the positive electrode sheet along the sheet stacking direction completely falls into the projection of the adjacent negative electrode sheet along the sheet stacking direction; the negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, and the single-side coating area density of the negative electrode film layer is 170 mg / 1540.25 mm 2 -200 mg / 1540.25 mm 2 , the compacted density is 1.4 g / cm 3 -1.6 g / cm 3 .

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery monomer, in particular to a battery monomer, a battery device and a power utilization device. BACKGROUND

[0002] In recent years, battery monomers are widely used in energy storage power supply systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, aerospace, etc.

[0003] With the rapid iteration and update of national standards and industry standards for energy storage batteries and power batteries, the requirements for energy density, safety and cycle performance of battery monomers are also increasing year by year. It is difficult to simultaneously improve the above-mentioned performances in the prior art, which has become a technical problem to be solved in the field. SUMMARY

[0004] In view of the above problems, the present application provides a battery monomer, a battery device and a power utilization device, which are described below respectively.

[0005] The first aspect of the present application provides a battery monomer, comprising an electrode assembly, an electrolyte and a shell, the electrode assembly is contained in the shell, the material of the shell is a soft package material; the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator, the positive electrode sheet and the negative electrode sheet are alternately stacked, and the separator is arranged between adjacent positive electrode sheets and negative electrode sheets; the negative electrode sheet is provided with a chamfer around; the projection of the positive electrode sheet along the sheet stacking direction completely falls within the projection of the adjacent negative electrode sheet along the sheet stacking direction; the negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, the negative electrode film layer has a single-sided coating surface density of 170 mg / 1540.25 mm 2 - 200mg / 1540.25mm 2 , and a compacted density of 1.4g / cm 3 -1.6g / cm 3 .

[0006] By using a soft package material as the shell, the positive electrode sheet and the negative electrode sheet are stacked, and a thick coating process is adopted in the film layer, the negative electrode film layer has a single-sided coating surface density of 170 mg / 1540.25 mm 2 - 200mg / 1540.25mm 2, which is beneficial to the improvement of the volumetric energy density of the battery. However, this process improvement also brings new technical challenges: on the one hand, the soft package material is used for hot-press packaging of the stacked electrode assembly, and the soft package material will shrink and plastically deform at high temperature, thus stress concentration will occur at the edges and corners of the electrode assembly, which will cause abnormal spacing between the stacked electrode plates at the edges of the electrode assembly, especially at the corners, and thus cause lithium precipitation, and deteriorate the long-term safety of the battery; on the other hand, the thick coating process increases the lithium ion transmission path, and the ion transmission resistance increases, which may cause local overpolarization of the electrode, the negative electrode potential decreases, and the deposition of metallic lithium on the negative electrode surface is promoted, which also affects the use safety and cycle life of the battery.

[0007] In the present application, the projection of the positive electrode plate along the direction of the plate stacking falls completely within the projection of the adjacent negative electrode plate along the direction of the plate stacking, and the non-projection area reduces the lithium precipitation phenomenon generated during the charging process as overhang; further, by setting chamfers around the larger negative electrode plate, on the one hand, the stress concentration caused by the shrinkage of the soft package material can be dispersed, and on the other hand, the stress at the edges mainly acts on the overhang area, reducing the influence on the overlapping area of the positive and negative electrode plates, so that the overlapping area is closely fitted and the interface is complete, thereby inhibiting the safety risk caused by stress and lithium precipitation at the edges and corners. Compared with hard-shell batteries, soft-shell batteries have less space for containing electrolyte in the shell, so a lower compaction density is used for the negative electrode film layer to increase the porosity of the negative electrode film layer and improve the liquid retention rate of the negative electrode film layer, which on the one hand reduces the risk of lithium precipitation caused by the long lithium ion transmission path of the thick coating film layer, and on the other hand reduces the risk of liquid depletion of the soft package stacked battery during long cycle, and improves the cycle life of the battery. Generally, the specific capacity of the negative active material is much larger than that of the positive active material, so the compaction density of the negative electrode film layer has little effect on the energy density of the battery, while the energy density of the battery is also considered.

[0008] In any embodiment, the single-sided thickness of the negative electrode film layer in the full discharge state is 70-90 μm, which can be 75-90 μm.

[0009] Studies have shown that in the full discharge state, when the single-sided thickness of the negative electrode film layer is too small, the battery capacity is difficult to meet the growing market demand, and when the thickness is too large, it is easy to cause kinetic decline, lithium precipitation and other problems. The single-sided thickness of the negative electrode film layer in the above range is beneficial to further improve the battery capacity and consider the problem of lithium precipitation.

[0010] In any embodiment, the chamfer includes one of a C-shaped chamfer and an R-shaped chamfer, which can be an R-shaped chamfer.

[0011] The R-type chamfer is a round chamfer, which can make the stress uniformly distributed by smooth transition and reduce stress concentration points, but requires the use of a special radius of a round tool for processing, the tool cost is higher, and the replacement of the tool to adapt to different radii of the round corner may increase the production cost and time; the C-type chamfer is a 45° bevel, and the same size is cut off from the adjacent two surfaces, which can be completed by a standard bevel tool or by adjusting the feed angle of the tool, the tool has strong universality, and the cost is relatively low, and the effect of reducing stress concentration is not as significant as the R-type chamfer.

[0012] In any embodiment, the radius of the R-type chamfer is 0.5%-2.5% of the width of the negative current collector, which can be selected as 0.8%-2%.

[0013] The radius of the R-type chamfer is selected in the above range, which can not only disperse the edge stress and reduce the probability of edge lithium precipitation, but also maximize the coating area as much as possible, so that the battery has high energy density and capacity.

[0014] In any embodiment, the size of the C-type chamfer is 0.5%-1.5% of the width of the negative current collector.

[0015] When the size of the C-type chamfer is in the above range, the probability of edge lithium precipitation can be reduced, and the coating area of the negative film layer can be increased, so that the battery has high energy density and cycle performance.

[0016] In any embodiment, the ratio of the size difference between any adjacent negative electrode sheet and positive electrode sheet in any direction of length or width to the size of the negative electrode sheet in the direction is 0.5%-1.5%.

[0017] When the ratio of the length or width of the negative electrode sheet and the positive electrode sheet is in the above range, the negative electrode sheet has an overhang region, which reduces lithium precipitation during charging, and the area of the positive electrode sheet, that is, the coating area, is also considered, which further improves the capacity and energy density of the battery monomer.

[0018] In any embodiment, the CB value of the battery monomer is 1.05-1.15, which can be selected as 1.08-1.15, wherein the CB value represents the ratio of the capacity of the negative electrode sheet to the capacity of the positive electrode sheet per unit area.

[0019] By designing the CB value of the battery monomer to be 1.05-1.15, the high lithium precipitation risk in the battery is further reduced, and the initial efficiency and cycle life of the battery are also improved.

[0020] In any embodiment, the negative electrode film layer comprises a negative electrode active material, the negative electrode active material comprises a graphite material, the graphite material has an OI value of 1.7-5, optionally 2.5-3.5, wherein the OI value = I 004 / I 110 , I 004 is the integral area of the diffraction peak of the 004 crystal face in X-ray diffraction analysis, I 110 is the integral area of the diffraction peak of the 110 crystal face.

[0021] The OI value represents the order degree of the material in the 004 crystal face or the 110 crystal face direction. A high OI value indicates that the graphite material is more anisotropic, and the expansion and contraction in a certain direction are more concentrated, which is not conducive to the stability of the structure and the uniformity of lithium ion intercalation / deintercalation. A low OI value indicates that the negative electrode active material has high lithium intercalation consistency, increasing the effective lithium intercalation end face in the negative electrode film layer. The OI value of the graphite material in the above range means that the graphite material tends to be isotropic, so the volume change is more uniform during charging and discharging, thereby prolonging the cycle life of the battery, and better ensuring sufficient electrolyte at the interface, while improving the solid-liquid transport rate of lithium ions, thereby inhibiting lithium precipitation during long-term cycling, balancing the long-term safety and life of the battery.

[0022] In any embodiment, the injection coefficient of the battery monomer is 2.5 g / Ah-4 g / Ah, optionally 2.7 g / Ah-3.2 g / Ah.

[0023] The injection coefficient refers to the ratio of the mass (g) of the injected electrolyte to the capacity (Ah) of the battery monomer. Controlling the injection coefficient of the lithium ion battery within the above range reduces the risk of lithium precipitation caused by the internal partial "drying" of the electrode sheet due to the small inhibiting effect of the soft package battery on the expansion during long-term cycling.

[0024] In any embodiment, along the stacking direction of the electrode sheets in the electrode assembly, the size of the negative electrode current collector in any one direction of length or width independently decreases by ΔL1 in turn, wherein 15 μm≤ΔL1≤120 μm.

[0025] In any embodiment, along the stacking direction of the electrode sheets in the electrode assembly, the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, and the size of the positive electrode current collector in any one direction of length or width independently decreases by ΔL2 in turn, wherein 15 μm≤ΔL2≤120 μm.

[0026] The length and / or width of the negative current collector and the positive current collector decrease in turn along the stacking direction. This makes the soft package material have better uniformity when sealed, reduces the probability of edge wrinkle of the current collector, covers not only the surface of the outermost electrode sheet but also the electrode sheet in the middle of the stack, further reduces lithium precipitation at the edge and corner of the electrode assembly, and improves the safety and cycle life of the battery.

[0027] In any embodiment, the projection of the battery monomer on the first projection plane is a first projection trapezoid, which can be an isosceles trapezoid; the first projection plane refers to the plane defined by the width direction and the stacking direction of the electrode assembly.

[0028] In any embodiment, the projection of the battery monomer on the second projection plane is a second projection trapezoid, which can be an isosceles trapezoid; the second projection plane refers to the plane defined by the length direction and the stacking direction of the electrode assembly.

[0029] The projection of the electrode assembly on the first projection plane is a trapezoid, and / or the projection of the electrode assembly on the second projection plane is a trapezoid, which can effectively disperse the stress applied to the electrode assembly, especially the edge and corner, by the soft package material shell during the heat sealing process; the isosceles trapezoidal battery monomer structure balances the stress received by different sides, further reducing the possibility of lithium precipitation due to stress concentration.

[0030] In any embodiment, the two angles formed by the leg of the first projection trapezoid and the longer base of the first projection trapezoid are α1 and α2, respectively, wherein 70°≤α1≤85°, 75°≤α2≤85°, and optionally α1=α2.

[0031] In any embodiment, the two angles formed by the leg of the second projection trapezoid and the longer base of the second projection trapezoid are β1 and β2, respectively, wherein 70°≤β1≤85°, 70°≤β2≤85°, and optionally β1=β2.

[0032] The two angles formed by the leg of the first projection trapezoid and the base of the first projection trapezoid, and / or the two angles formed by the leg of the second projection trapezoid and the longer base of the second projection trapezoid, are within the above range, which not only optimizes the stress distribution but also reduces the influence of excessive angle on the coating area of the active material, and balances the energy density of the battery.

[0033] In any embodiment, the positive electrode sheet is also provided with a chamfer around the periphery.

[0034] The design of no chamfer around the positive electrode tab makes the positive electrode tab not need to go through the cutting process, avoiding the problem that the burrs or active material shedding of the positive current collector caused by cutting expose the positive current collector directly to the electrolyte. However, in the case of matching with the chamfer around the negative electrode tab, to avoid the problem of lithium precipitation or short circuit caused by the straight angle of the positive electrode tab exceeding the range of the negative electrode tab, the size of the positive electrode tab is restricted, which wastes a lot of area. By setting chamfer around the positive electrode tab, the stress of the tab corner is further reduced, and the size of the positive electrode tab is increased, maximizing the overlapping area of the projection of the negative electrode tab, and improving the energy density of the battery monomer.

[0035] In any embodiment, the thickness of the negative current collector is 6-10 μm.

[0036] In any embodiment, the positive electrode tab includes a positive current collector and a positive film layer arranged on at least one side of the positive current collector, and the thickness of the positive current collector is 12-15 μm.

[0037] The thickness of the current collector is in the above range, which on the one hand is conducive to improving the mechanical strength of the soft pack laminated battery and improving the ability of the battery to resist swelling, and on the other hand can increase the overcurrent area, thereby reducing the internal resistance of the tab and inhibiting the internal heating of the tab, improving the safety and long-term life of the battery.

[0038] In any embodiment, the positive electrode tab includes a positive current collector and a positive film layer arranged on at least one side of the positive current collector, and the length of the positive current collector and / or the negative current collector is 520-570 mm.

[0039] In any embodiment, the positive electrode tab includes a positive current collector and a positive film layer arranged on at least one side of the positive current collector, and the width of the positive current collector and / or the negative current collector is 100-130 mm.

[0040] The length and width of the positive current collector and / or the negative current collector are in the above range, which on the one hand is conducive to enhancing heat dissipation and improving the cycle life of the battery, and on the other hand, the battery monomer with the current collector having the above size can adapt to the existing module and battery pack space, and improve the grouping efficiency, achieving higher energy density at the module and battery pack level.

[0041] The second aspect of the present application provides a battery device comprising the battery monomer of the first aspect of the present application.

[0042] The third aspect of the present application provides a power utilization device comprising at least one of the battery monomer of the first aspect of the present application and the battery device of the second aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0043] In the drawings, like reference numerals refer to like elements throughout the various figures. The drawings are not necessarily to scale, and the emphasis is on the functional relationships between elements. It should be understood that these drawings are merely schematic and are not intended to portray true dimensions of the application.

[0044] Figure 1 is a schematic plan view of an electrode assembly in an embodiment of the application;

[0045] Figure 2 is a schematic front view of an electrode assembly in an embodiment of the application;

[0046] Figure 3 is a schematic perspective view of an electrode assembly in an embodiment of the application;

[0047] Figure 4 is a schematic perspective view of a battery cell in an embodiment of the application;

[0048] Figure 5 is a schematic view of an electrical device in an embodiment of the application.

[0049] BRIEF DESCRIPTION OF DRAWINGS

[0050] 1 electrode assembly, 11 separator, 12 positive electrode tab, 121 first positive electrode tab, 13 negative electrode tab, 131 first negative electrode tab, 132 second negative electrode tab, 14 positive electrode tab, 15 negative electrode tab, 5 battery cell. DETAILED DESCRIPTION

[0051] Hereinafter, embodiments of a battery cell, a battery device, and an electrical device according to the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there can be cases where unnecessary detailed description is omitted. For example, there can be cases where detailed description of matters well known, repeated description of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0052] The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges are also intended to include any and all sub-ranges of the same, wherein each sub-range is inclusive of the end values. For example, if a range is from 1 to 10, then the range includes any and all sub-ranges between (and including) the minimum of 1 and the maximum of 10, that is, any of 1 to 3, 4 to 6, 7 to 9, and 10 to 10, etc. Also, it is specifically intended that the minimum and maximum values of the ranges are included in the ranges. For example, if a range is from 1 to 10, then it is specifically intended that the value 1 and the value 10 are part of the range. Further, it is specifically intended that the values 1 and 10 are part of the range even if the actual value used or provided is not a whole number. For example, it is intended that the value 1. 1 is part of the range while it is not intended that values like 1.1 1, 1. 11, etc. are to be included in the range of 1 to 10 unless otherwise specifically indicated. It is also intended that the value 10 is part of the range even if the actual value used or provided is not a whole number. For example, it is intended that the value 10. 1 is part of the range while it is not intended that values like 10. 1 1, 10. 11, etc. are to be included in the range of 1 to 10 unless otherwise specifically indicated. It is intended that the number of integers in a range is inclusive of the end values. For example, if a range is from 2 to 10, then the range includes integers 2, 3, 4, 5, 6, 7, 8, 9, and 10. It is intended that the number of integers in a range is inclusive of the end values even if the actual number used or provided is not a whole number. For example, it is intended that the value 2. 1 is part of the range while it is not intended that values like 2. 1 1, 2. 11, etc. are to be included in the range of 2 to 10 unless otherwise specifically indicated. It is intended that the number of integers in a range is inclusive of the end values even if the actual number used or provided is not a whole number. For example, it is intended that the value 10. 1 is part of the range while it is not intended that values like 10. 1 1, 10. 11, etc. are to be included in the range of 2 to 10 unless otherwise specifically indicated.

[0053] Unless otherwise indicated, all embodiments and optional embodiments of the present application can be combined together to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0054] Unless otherwise indicated, all technical features of the present application and optional technical features can be combined together to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0055] Unless otherwise indicated, all steps of the present application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0056] In the present application, the terms "a plurality of" and "a plurality of" refer to two or more.

[0057] Unless otherwise indicated, the terms used in the present application have the commonly understood meanings understood by those skilled in the art.

[0058] Unless otherwise stated, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in the embodiments of this application. Unless otherwise stated, the test temperature for each parameter is 25°C.

[0059] The battery mentioned in the embodiments of this application can be a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application can include battery cells, battery modules, or battery packs.

[0060] A single battery cell is the smallest unit that makes up a battery, and it can independently perform the functions of charging and discharging.

[0061] A single battery cell includes electrode components and an electrolyte.

[0062] Electrode assemblies typically include positive and negative electrodes. The negative electrode is the electrode that absorbs or lithiates lithium ions during charging and releases or delithiates lithium during discharging. The positive electrode is the electrode that absorbs or delithiates lithium ions during charging and absorbs or lithiates lithium during discharging.

[0063] In some implementations, such as Figure 1 As shown, the electrode assembly of a single battery cell includes a positive electrode 12, a negative electrode 13, a separator 11, a positive electrode tab 14, and a negative electrode tab 15. The X direction represents the length direction of the electrode assembly. The Y direction represents the width direction of the electrode assembly. The Z direction represents the stacking direction of the electrode assembly.

[0064] The battery cell may also include an outer packaging, which can be used to encapsulate the electrode assembly and electrolyte. The outer packaging is a pouch, such as a bag-type pouch. The pouch material can be one or more of plastics, such as polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0065] The number of electrode assemblies 1 contained in a single battery cell can be one or more, and can be adjusted as needed. When there are multiple battery cells, the multiple battery cells are connected in series, parallel, or mixed through a busbar. In some embodiments, the battery can be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery can be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed in the housing. In some embodiments, the housing can be part of the vehicle's chassis structure. For example, a portion of the housing can be at least a part of the vehicle's floor, or a portion of the housing can be at least a part of the vehicle's crossbeams and longitudinal beams.

[0066] In some embodiments, the battery can be an energy storage device. The energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0067] In some embodiments, the battery cells can be assembled into a battery module, and the number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. In the battery module, the plurality of battery cells can be arranged in sequence along the length direction of the battery module. Of course, other arbitrary arrangements can also be used. Further, the plurality of battery cells can be fixed by fasteners.

[0068] Optionally, the battery module can further include a housing having an accommodation space, and the plurality of battery cells are accommodated in the accommodation space.

[0069] In some embodiments, the battery module described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0070] The battery pack can include a box body and a plurality of battery modules arranged in the box body. The box body can include an upper box body and a lower box body, and the upper box body is used to cover the lower box body and form a closed space for accommodating the battery modules. The plurality of battery modules can be arranged in the box body in any manner.

[0071] With the development of the battery industry, the requirements for battery cells are constantly improving, and the standards for the energy density of energy storage batteries and power batteries are increasing year by year. In the prior art, the following technical paths are mainly used for improvement: adopting a laminated electrode assembly design, which can improve the space utilization rate by 5%-8% compared with the traditional winding structure, increase the load of active materials in the battery cell, and adopt a soft package shell, which is lighter, further improves the battery load and the energy density of the battery. In the electrode preparation link, a thick coating process is used to increase the surface density of active materials and relatively reduce the proportion of non-active materials such as current collectors and separators, thereby improving the volume energy density. However, research shows that the probability of lithium precipitation in battery cells using the above methods increases significantly, which affects the cycle life and safety of the battery. Therefore, how to balance the cycle life and safety of the battery while maintaining high energy density is still a technical problem that needs to be solved urgently.

[0072] The first aspect of the present application provides a battery cell, characterized in that it comprises an electrode assembly, an electrolyte and a shell, the electrode assembly is accommodated in the shell, the material of the shell is a soft package material; the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator, the positive electrode sheet and the negative electrode sheet are alternately stacked, and the separator is arranged between adjacent positive electrode sheets and negative electrode sheets; the negative electrode sheet is provided with a chamfer around the periphery; the projection of the positive electrode sheet along the sheet stacking direction completely falls within the projection of the adjacent negative electrode sheet along the sheet stacking direction; the negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, the negative electrode film layer has a single-sided coating area density of 170mg / 1540.25mm 2 -200mg / 1540.25mm 2 , and a compacted density of 1.4g / cm 3 -1.6g / cm 3 .

[0073] By using a soft package material as the shell, the positive electrode sheet and the negative electrode sheet are stacked, and a thick coating process is adopted in the film layer, the negative electrode film layer has a single-sided coating area density of 170mg / 1540.25mm 2 -200mg / 1540.25mm 2 in the full discharge state, which is beneficial to the improvement of the battery volume energy density. However, this process improvement also brings new technical challenges: on the one hand, the soft package material will shrink and plastically deform at high temperature when the laminated electrode assembly is hot-pressed and packaged, so stress concentration will occur at the edges and corners of the electrode assembly, causing the spacing between the stacked sheets at the edges of the electrode assembly, especially at the corners, to be abnormal, which will cause lithium precipitation and worsen the long-term safety of the battery; on the other hand, the thick coating process increases the lithium ion transmission path, and the ion transmission resistance increases, which may cause local overpolarization of the electrode, the negative electrode potential decreases, and metal lithium is deposited on the surface of the negative electrode, which also affects the use safety and cycle life of the battery.

[0074] In the present application, the projection of the positive electrode tab along the tab stacking direction completely falls into the projection of the adjacent negative electrode tab along the tab stacking direction, and the non-projection area reduces the lithium precipitation phenomenon generated during charging as overhang; further by setting chamfer around the larger negative electrode tab, on the one hand, the corner stress concentration caused by the shrinkage of the soft package material can be dispersed, and on the other hand, the stress of the edge mainly acts on the overhang area, reduces the influence on the overlapping area of the positive and negative electrode tabs, so that the overlapping area is tightly attached and the interface is complete, thereby inhibiting the safety risk of lithium precipitation caused by stress at the edge and corner. Compared with hard-shell batteries, soft package batteries have less space for containing electrolyte in the shell, so a lower compaction density is used for the negative electrode film layer, which can increase the porosity of the negative electrode film layer and improve the liquid retention rate of the negative electrode film layer, on the one hand, reducing the risk of lithium precipitation caused by long lithium ion transmission path of thick coated film layer, on the other hand, reducing the risk of liquid depletion of soft package tab battery during long cycle process, and improving the cycle life of the battery. Generally, the specific capacity of the negative electrode active material is much larger than that of the positive electrode active material, so the compaction density of the negative electrode film layer has little effect on the energy density of the battery, while the energy density of the battery is also considered.

[0075] In some embodiments, the single-sided coating area density of the negative electrode film layer in the full discharge state can be selected as 170 mg / 1540.25 mm 2 , 175 mg / 1540.25 mm 2 , 180 mg / 1540.25 mm 2 , 185 mg / 1540.25 mm 2 , 190 mg / 1540.25 mm 2 , 195 mg / 1540.25 mm 2 , 200 mg / 1540.25 mm 2 or a numerical range between any two of the above.

[0076] In the present application, the single-sided coating area density of the negative electrode film layer is the meaning known in the art, which can be tested by known methods in the art. For example, a single-sided coated and compacted negative electrode tab (if it is a double-sided coated negative electrode tab, the negative electrode film layer on one side can be wiped off first) is punched into a small disc with an area of S1, weighed and recorded as M1. Then the negative electrode film layer of the above weighed negative electrode tab is wiped off, the weight of the current collector is weighed and recorded as M0. The single-sided coating area density of the negative electrode film layer is (M1-M0) / S1. In order to ensure the accuracy of the test results, multiple groups (for example, 10 groups) of test samples can be tested, and the average value is calculated as the test result.

[0077] In some embodiments, the compaction density of the negative electrode film layer in the full discharge state can be selected as 1.4 g / cm 3 , 1.41 g / cm3 1.42 g / cm3 3 1.43 g / cm3 3 1.44 g / cm3 3 1.45 g / cm3 3 1.46 g / cm3 3 1.47 g / cm3 3 1.48 g / cm3 3 1.49 g / cm3 3 1.50 g / cm3 3 1.51 g / cm3 3 1.52 g / cm3 3 1.53 g / cm3 3 1.54 g / cm3 3 1.55 g / cm3 3 1.56 g / cm3 3 1.57 g / cm3 3 1.58 g / cm3 3 1.59 g / cm3 3 1.6 g / cm3 3 or a numerical range between any two of the above.

[0078] In the present application, the full discharge state refers to the following state: the battery is placed in a 25°C oven environment and left for 2h, and the battery temperature is maintained at 25°C. After the battery is discharged at 1 / 3C constant current to 2.0V, it is left for half an hour, and then discharged at 0.04C constant current to 2.0V.

[0079] The compaction density of the negative electrode film layer can be tested by methods known in the art. As an example, the battery is placed in a 25°C oven environment and left for 2h, and the battery temperature is maintained at 25°C. After the battery is discharged at 1 / 3C constant current to 2.0V, it is left for half an hour, and then discharged at 0.04C constant current to 2.0V. The battery is disassembled, the negative electrode sheet is obtained, the residual electrolyte is treated with dimethyl carbonate solvent, the sheet is dried, cut into small round pieces with an area of S, the mass W1 is obtained, and the thickness T1 of the negative electrode sheet is measured using a micrometer. Then the negative electrode film layer of the above weighed sheet is wiped off, the mass of the current collector is weighed and recorded as W2, and the thickness T2 of the current collector is measured using a micrometer. The compaction density PD of the negative electrode film layer is (W1-W2) / [(T1-T2)×S].

[0080] In some embodiments, the single-sided thickness of the negative electrode film layer in the full discharge state is 70-90μm, which can be 75-90μm.

[0081] In some embodiments, the single-side thickness of the negative electrode film layer in the full discharge state can be selected as 70 μm, 71 μm, 72 μm, 73 μm, 74 μm, 75 μm, 75.1 μm, 76 μm, 76.1 μm, 77 μm, 78 μm, 79 μm, 80 μm, 81 μm, 82 μm, 82.8 μm, 83 μm, 84 μm, 85 μm, 85.8 μm, 86 μm, 87 μm, 88 μm, 89 μm, 89.6 μm, 90 μm, or a numerical range between any two of the above.

[0082] Research shows that, in the full discharge state, when the single-side thickness of the negative electrode film layer is too small, the battery capacity is difficult to meet the growing market demand, and when the thickness is too large, it is easy to cause kinetic decline, lithium precipitation and other problems. The single-side thickness of the negative electrode film layer within the above range is beneficial to further improve the battery capacity and take into account the problem of lithium precipitation.

[0083] In some embodiments, the chamfer includes one of a C-shaped chamfer and an R-shaped chamfer, which can be an R-shaped chamfer.

[0084] The R-shaped chamfer is a circular chamfer, which can smoothly transition and uniformly distribute stress, reducing stress concentration points, but requires the use of a special radius of circular corner tool for processing, which has a higher tool cost, and replacing the tool to adapt to different radii of the circular corner can increase production cost and time; the C-shaped chamfer is a 45° bevel, and adjacent two faces are cut by the same size, which can be completed by a standard bevel tool or by adjusting the feed angle of the tool, and the tool has strong versatility and relatively low cost, but the effect of reducing stress concentration is not as significant as the R-shaped chamfer.

[0085] In some embodiments, the radius of the R-shaped chamfer is 0.5%-2.5% of the width of the negative electrode current collector, which can be 0.8%-2%.

[0086] In some embodiments, the radius of the R-shaped chamfer can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5% of the width of the negative electrode tab, or a numerical range between any two of the above.

[0087] The selection of the radius of the R-shaped chamfer within the above range can not only disperse edge stress and reduce the probability of edge lithium precipitation, but also maximize the coating area as much as possible, so that the battery has high energy density and capacity.

[0088] In some embodiments, the size of the C-shaped chamfer is 0.5%-1.5% of the width of the negative electrode current collector.

[0089] In some embodiments, the size of the C-shaped chamfer can be selected to be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5% or a numerical range between any two of the above of the width of the negative current collector.

[0090] When the size of the C-shaped chamfer is within the above range, the probability of lithium precipitation at the edge is also reduced, and the coating area of the negative film layer is increased, so that the battery has both high energy density and cycle performance.

[0091] In some embodiments, along the stacking direction of the electrode assembly, the size difference between any adjacent negative electrode tab and positive electrode tab in either length or width direction and the size of the negative electrode tab in that direction can be 0.5%-1.5%.

[0092] In some embodiments, along the stacking direction of the electrode assembly, the size difference between any adjacent negative electrode tab and positive electrode tab in either length or width direction and the size of the negative electrode tab in that direction can be selected to be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, or a numerical range between any two of the above.

[0093] In this application, as an example, the ratio of the size difference between any adjacent negative electrode tab and positive electrode tab in either length or width direction and the size of the negative electrode tab in that direction can be calculated as follows: Figure 2 As shown, it includes a first positive electrode tab 121, a first negative electrode tab 131 adjacent to the first positive electrode tab 121, and a second negative electrode tab 132 adjacent to the first positive electrode tab 121. P1 L is the length of the first positive electrode tab 121 in the figure. N1 L is the length of the first negative electrode tab 131 in the figure. N2 L is the length of the second negative electrode tab in the figure; the ratio of the size difference between the adjacent negative electrode tab and the positive electrode tab in the length direction and the size of the negative electrode tab in that direction includes (L N1 -L P1 ) / L N1 and (L N2 -L P1 ) / L N2 Both of the above ratios are within the range of 0.5%-1.5%.

[0094] When the length and width ratio of the negative electrode tab and the positive electrode tab is within the above range, the negative electrode tab has an overhang region, reducing lithium precipitation during charging, and taking into account the area of the positive electrode tab, i.e. the coating area, further improving the capacity and energy density of the battery cell.

[0095] In some embodiments, the CB value of the battery cell is in the range of 1.05-1.15, and optionally in the range of 1.08-1.15, wherein the CB value represents the ratio of the capacity of the negative electrode tab to the capacity of the positive electrode tab per unit area.

[0096] In some embodiments, the CB value of the battery cell is optionally 1.05, 1.06, 70.7, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, 1.15, or a numerical range between any two of the above values.

[0097] In the present application, the CB value of the battery cell is designed to be in the range of 1.05-1.15, which further reduces the high risk of lithium precipitation in the battery, and improves the initial efficiency and cycle life of the battery.

[0098] In some embodiments, the negative electrode film layer comprises a negative electrode active material, and the negative electrode active material comprises a graphite material, and the OI value of the graphite material is in the range of 1.7-5, and optionally in the range of 2.5-3.5, wherein the OI value = I 004 / I 110 , I 004 is the integral area of the diffraction peak of the 004 crystal face in X-ray diffraction analysis, and I 110 is the integral area of the diffraction peak of the 110 crystal face.

[0099] In some embodiments, the OI value of the graphite material is optionally 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 4, 4.5, 5, or a numerical range between any two of the above values.

[0100] The OI value represents the order degree of the material in the 004 crystal face or the 110 crystal face direction. A high OI value indicates that the graphite material is more anisotropic, and the expansion and contraction in a certain direction are more concentrated, which is not conducive to the stability of the structure and the uniformity of lithium ion intercalation / deintercalation. A low OI value indicates that the negative electrode active material has high lithium intercalation consistency, and increases the effective lithium intercalation end face in the negative electrode film layer. The OI value of the graphite material in the above range means that the graphite material tends to be isotropic, so the volume change is more uniform during charging and discharging, thereby prolonging the cycle life of the battery, and better ensuring sufficient electrolyte at the interface, while improving the solid-liquid transport rate of lithium ions, thereby inhibiting lithium precipitation under long-term cycling, and balancing the long-term safety and life of the battery.

[0101] In some embodiments, the battery cell has a liquid injection coefficient of 2.5 g / Ah-4 g / Ah, optionally 2.7 g / Ah-3.2 g / Ah.

[0102] In some embodiments, the battery cell has a liquid injection coefficient of 2.5 g / Ah, 2.6 g / Ah, 2.7 g / Ah, 2.8 g / Ah, 2.9 g / Ah, 3.0 g / Ah, 3.1 g / Ah, 3.2 g / Ah, 3.3 g / Ah, 3.4 g / Ah, 3.5 g / Ah, 3.6 g / Ah, 3.7 g / Ah, 3.8 g / Ah, 3.9 g / Ah, 4 g / Ah, or a numerical range between any two of the above.

[0103] The liquid injection coefficient refers to the ratio of the mass (g) of the injected electrolyte to the capacity (Ah) of the battery cell. Controlling the liquid injection coefficient of the lithium ion battery within the above range reduces the risk of lithium precipitation caused by the internal partial "drying" of the electrode sheet due to the small inhibiting effect of the soft package battery on the expansion during long-term cycling.

[0104] In some embodiments, along the stacking direction of the electrode assembly, the size of the negative current collector in either length or width direction independently decreases by ΔL1 in sequence, where 15 μm≤ΔL1≤120 μm.

[0105] In some embodiments, ΔL1 can be 15 μm, 20 μm, 22 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 91 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, or a numerical range between any two of the above.

[0106] In some embodiments, the positive electrode sheet includes a positive current collector and a positive film layer arranged on at least one side of the positive current collector, and along the stacking direction of the electrode assembly, the size of the positive current collector in either length or width direction independently decreases by ΔL2 in sequence, where 15 μm≤ΔL2≤120 μm.

[0107] In some embodiments, ΔL2 can be 15 μm, 20 μm, 22 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 91 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, or a numerical range between any two of the above.

[0108] The length and / or width of the negative current collector and the positive current collector decrease sequentially in the stacking direction, as shown in Figure 3 The soft package material is better uniform when sealed, and the probability of edge wrinkle of the current collector is reduced. Not only the surface of the outermost electrode sheet is covered, but also the intermediate electrode sheet participates in stress dispersion, further reducing lithium precipitation at the edge and corner of the electrode assembly, and improving the safety and cycle life of the battery.

[0109] In some embodiments, the projection of the battery monomer on the first projection plane is a first projection trapezoid, which can be an isosceles trapezoid; the first projection plane refers to the plane defined by the width direction and the stacking direction of the electrode assembly.

[0110] In some embodiments, the projection of the battery monomer on the second projection plane is a second projection trapezoid, which can be an isosceles trapezoid; the second projection plane refers to the plane defined by the length direction and the stacking direction of the electrode assembly.

[0111] The projection of the electrode assembly on the first projection plane is a trapezoidal cross section, and / or the projection of the electrode assembly on the second projection plane is a trapezoidal cross section, which can effectively disperse the stress applied to the electrode assembly, especially the edge and corner, by the soft package material shell during heat sealing; the isosceles trapezoidal battery monomer structure balances the stress received by different sides, further reducing the possibility of lithium precipitation due to stress concentration.

[0112] In some embodiments, the two angles formed by the leg of the first projection trapezoid and the longer base of the first projection trapezoid are α1 and α2, respectively, wherein 70°≤α1≤85°, 70°≤α2≤85°, and optionally α1=α2.

[0113] In some embodiments, α1 can be 70°, 71°, 72°, 73°, 74°, 75°, 76°, 77°, 75°, 79°, 80°, 81°, 82°, 83°, 84°, 85°, or a numerical range between any two of the above.

[0114] In some embodiments, α2 can be 70°, 71°, 72°, 73°, 74°, 75°, 76°, 77°, 75°, 79°, 80°, 81°, 82°, 83°, 84°, 85°, or a numerical range between any two of the above.

[0115] In some embodiments, the two angles formed by the leg of the second projection trapezoid and the longer base of the second projection trapezoid are β1 and β2, respectively, wherein 70°≤β1≤85°, 70°≤β2≤85°, and optionally β1=β2.

[0116] In some embodiments, β1 can be selected from 70°, 71°, 72°, 73°, 74°, 75°, 76°, 77°, 75°, 79°, 80°, 81°, 82°, 83°, 84°, 85°, or a numerical range between any two of the above.

[0117] In some embodiments, β2 can be selected from 70°, 71°, 72°, 73°, 74°, 75°, 76°, 77°, 75°, 79°, 80°, 81°, 82°, 83°, 84°, 85°, or a numerical range between any two of the above.

[0118] In the present application, the "longer base of the projected trapezoid" means that the projected trapezoid has two parallel bases, and the longer one is selected. The two angles formed by the waist of the first projected trapezoid and the longer base of the first projected trapezoid are α1 and α2, respectively, and the two angles formed by the waist of the second projected trapezoid and the longer base of the second projected trapezoid are β1 and β2, respectively, as shown in Figure 4

[0119] The two angles formed by the waist of the first projected trapezoid and the longer base of the first projected trapezoid, and / or the two angles formed by the waist of the second projected trapezoid and the longer base of the second projected trapezoid are within the above range, which optimizes the stress distribution and reduces the impact of excessive angles on the coating area of the active material, and takes into account the energy density of the battery.

[0120] In some embodiments, the four corners of the positive electrode tab are also provided with chamfers.

[0121] The design of no chamfer on the four corners of the positive electrode tab makes the positive electrode tab not need to go through the cutting process, avoiding the problem that the burrs or active material falling off of the positive current collector caused by cutting directly expose the positive current collector to the electrolyte. However, in the case of matching the chamfered corners of the negative electrode tab, to avoid the problem of lithium precipitation or short circuit caused by the straight corners of the positive electrode tab exceeding the range of the negative electrode tab, the size of the positive electrode tab is restricted, which wastes a lot of area. By providing chamfers on the four corners of the positive electrode tab, the stress of the corners of the tab is further reduced, and the size of the positive electrode tab is increased, maximizing the overlapping area of the projection of the negative electrode tab, and improving the energy density of the battery monomer.

[0122] In some embodiments, the chamfer type of the four corners of the positive electrode tab is the same as the chamfer type of the four corners of the negative electrode tab.

[0123] The positive electrode tab has the same chamfer type as the negative electrode tab, which is beneficial to further uniformly disperse the stress and reduce the stress-induced lithium precipitation at the edges.

[0124] ​In some embodiments, the positive electrode tab has an R-shaped chamfer around the periphery, the positive electrode tab comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, and the radius of the R-shaped chamfer is 0.5%-2.5% of the width of the positive electrode current collector.

[0125] The positive electrode tab has an R-shaped chamfer around the periphery, and the radius of the R-shaped chamfer is selected within the above range, which can reduce edge lithium precipitation while maximizing the coating area as much as possible, so that the battery has high energy density and capacity.

[0126] In some embodiments, the thickness of the negative electrode current collector is 6-10 μm.

[0127] In some embodiments, the thickness of the negative electrode current collector can be selected as 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a numerical range between any two of the above.

[0128] In some embodiments, the positive electrode tab comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, and the thickness of the positive electrode current collector is 12-15 μm.

[0129] In some embodiments, the thickness of the positive electrode current collector can be selected as 12 μm, 13 μm, 14 μm, 15 μm, or a numerical range between any two of the above.

[0130] The thickness of the current collector within the above range is beneficial on the one hand to improve the mechanical strength of the soft package laminated battery and improve the battery's ability to resist swelling, and on the other hand to increase the current-carrying area, thereby reducing the internal resistance of the tab and inhibiting the internal heating of the tab, improving the safety and long-term life of the battery.

[0131] In some embodiments, the positive electrode tab comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, and the length of the positive electrode current collector and / or the negative electrode current collector is 520-570 mm.

[0132] In some embodiments, the length of the positive electrode current collector and / or the negative electrode current collector can be selected as 520 mm, 530 mm, 540 mm, 550 mm, 560 mm, 570 mm, or a numerical range between any two of the above.

[0133] In some embodiments, the positive electrode tab comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, and the width of the positive electrode current collector and / or the negative electrode current collector is 100-130 mm.

[0134] In some embodiments, the width of the positive current collector and / or the negative current collector can be selected to be 100 mm, 110 mm, 120 mm, 130 mm, or a range of values between any of the foregoing.

[0135] The length and width of the positive current collector and / or the negative current collector within the above ranges, on the one hand, is conducive to enhancing heat dissipation and improving the cycle life of the battery, and on the other hand, the battery cell with the current collector having the above dimensions can be adapted to the existing module and battery pack space and improve the grouping efficiency, and achieve higher energy density at the module and battery pack level.

[0136] [Positive electrode sheet]

[0137] In some embodiments, the positive current collector can be a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0138] In some embodiments, the positive film layer includes a positive active material. The positive active material can use a positive active material for a battery known in the art. As an example, the positive active material can include at least one of the following materials: at least one of lithium cobaltate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium vanadate, and lithium manganate. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive active material for a battery can also be used. These positive active materials can be used only one kind alone, or two or more kinds in combination.

[0139] In some embodiments, the positive film layer can further optionally include a conductive agent. As an example, the conductive agent can include at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0140] In some embodiments, the positive film layer can further optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin.

[0141] In some embodiments, the positive electrode sheet can be prepared by dispersing the components for preparing the positive electrode film layer, such as the positive electrode active material, the conductive agent, the polymer binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one side surface of the positive electrode current collector; and subjecting the positive electrode current collector to drying, cold pressing, or the like to obtain the positive electrode sheet.

[0142] [Anode sheet]

[0143] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, or the like) on a polymer material base layer (such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), or the like).

[0144] In some embodiments, the negative electrode film layer can further optionally include a binder. The binder can be selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0145] In some embodiments, the negative electrode film layer can further optionally include a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0146] In some embodiments, the negative electrode film layer can further optionally include other auxiliary agents, such as a thickening agent (such as sodium carboxymethyl cellulose (CMC-Na)) or the like.

[0147] In some embodiments, the negative electrode sheet can be prepared by dispersing the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector; and subjecting the negative electrode current collector to drying, cold pressing, or the like to obtain the negative electrode sheet.

[0148] [Electrolyte]

[0149] The electrolyte serves to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of the electrolyte is not specifically limited in the present application and can be selected as needed. For example, the electrolyte can be in a liquid state, a gel state, or a full solid state.

[0150] In some embodiments, the electrolyte employs an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0151] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bistrifluoromethylsulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorobisoxalate phosphate.

[0152] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0153] In some embodiments, the electrolyte solution can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include an additive capable of improving certain properties of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0154] [Separator]

[0155] The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0156] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0157] [Battery cell]

[0158] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly through a stacking process.

[0159] In some embodiments, the battery cell can include an outer package. The outer package can be used to package the above-described electrode assembly and electrolyte.

[0160] [Battery device]

[0161] The battery device provided by the embodiments of the present application can be used as a power source of the electric device or an energy storage unit of the electric device. The electric device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0162] [Electric device]

[0163] In addition, the embodiments of the present application also provide an electric device, which includes at least one of the battery cell, the battery module or the battery pack provided by the embodiments of the present application. The battery cell, the battery module or the battery pack can be used as a power source of the electric device or an energy storage unit of the electric device. The electric device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0164] As the electric device, the battery cell, the battery module or the battery pack can be selected according to the use requirement of the electric device.

[0165] Figure 5 The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the battery cell for the electric device, the battery pack or the battery module can be used.

[0166] The embodiments of the present application also provide an energy storage device, which includes the battery device provided by the embodiments of the present application.

[0167] The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the battery cell for the electric device, the battery pack or the battery module can be used.

[0168] Embodiments

[0169] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application. If a specific technology or condition is not mentioned in the embodiments, the technology or condition is performed according to the technology or condition described in the literature in the art or according to the product instruction. If the reagent or instrument used is not mentioned by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0170] Embodiment 1

[0171] 1) Preparation of the positive electrode sheet

[0172] Preparation of the positive electrode film layer slurry: lithium iron phosphate positive electrode active material, conductive carbon black, and binder PVDF were mixed in a mass ratio of 98:1:1, and solvent NMP was added. The system was stirred under the action of a vacuum stirrer until it became uniform, and a positive electrode film layer slurry was obtained.

[0173] The positive electrode film layer slurry was uniformly coated on both sides of an aluminum foil current collector with a thickness of 15 μm, and the single-sided coating density was 385 mg / 1540.25 mm 2 After air drying at room temperature, the positive electrode film layer slurry was transferred to an oven for further drying, and then cold-pressed to obtain a positive electrode sheet. The compaction density of the positive electrode film layer was 2.45 g / cm 3 ; wherein the length of the aluminum foil current collector was 544 mm, and the width was 120.5 mm.

[0174] In the stacking direction, the length and width of the aluminum foil current collector in the positive electrode sheet did not change.

[0175] 2) Preparation of the negative electrode sheet

[0176] Preparation of the negative electrode film layer slurry: artificial graphite negative electrode active material, polyvinyl alcohol binder, and SP-Li conductive agent were mixed in a mass ratio of 90:5:5 in a deionized water solvent system and ball-milled to obtain a negative electrode slurry; wherein the OI value of the artificial graphite negative electrode active material was 5.

[0177] The negative electrode film layer slurry was uniformly coated on both sides of a copper foil current collector with a thickness of 8 μm, and the single-sided coating density was 180 mg / 1540.25 mm 2 After vacuum drying at a temperature of 110°C overnight, the negative electrode film layer slurry was cold-pressed and chamfered to obtain a negative electrode sheet. The compaction density of the negative electrode film layer was 1.53 g / cm 3 ; wherein the length of the copper foil current collector was 548 mm, and the width was 122 mm; the chamfering process included cutting the four corners of the cold-pressed negative electrode sheet to obtain an R-shaped chamfer with a chamfer radius of 1.5% of the width of the negative electrode current collector.

[0178] In the stacking direction, the length and width of the copper foil current collector in the negative electrode sheet did not change.

[0179] 3) Preparation of the separator

[0180] A polyethylene film with a thickness of 11 μm was used as the separator.

[0181] 4) Preparation of the electrolyte

[0182] Lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonylimide (LiFSI) were dissolved in ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) with a volume ratio of 1:1:1 to form a uniform solution, obtaining an electrolyte with a LiPF6 concentration of 0.7 mol / L and a LiFSI concentration of 0.3 mol / L.

[0183] 5) Assembly of the battery

[0184] The positive and negative electrode sheets obtained by cutting were stacked according to the Z-type stacking method, and the stacking order was "positive electrode sheet-separator-negative electrode sheet-separator" to form an electrode assembly. The baked electrode assembly was placed in an aluminum plastic film, injected, vacuumed, and heat-pressed to seal to form airtight packaging, and finally a stacked soft-pack battery monomer was obtained. The injection coefficient of the battery monomer was 2.5 g / Ah, and the CB value was 1.05.

[0185] The preparation method of Example 2 was basically the same as that of Example 1, except that the single-sided coating area density of the negative electrode slurry in the preparation of the negative electrode sheet was adjusted. The negative electrode slurry was double-sided coated on the double-sided surface of a copper foil with a thickness of 8 μm according to a single-sided coating area density of 170 mg / 1540.25 mm 2 .

[0186] The preparation method of Example 3 was basically the same as that of Example 1, except that the single-sided coating area density of the negative electrode slurry in the preparation of the negative electrode sheet was adjusted. The negative electrode slurry was double-sided coated on the double-sided surface of a copper foil with a thickness of 8 μm according to a single-sided coating area density of 200 mg / 1540.25 mm 2 .

[0187] The preparation method of Example 4 was basically the same as that of Example 1, except that in the preparation of the negative electrode sheet, the compaction density of the negative electrode sheet obtained after cold pressing was 1.46 g / cm 3 by adjusting the pressure, rolling speed, roll gap, pressure holding time and rolling times in the compaction process.

[0188] The preparation method of Example 5 was basically the same as that of Example 1, except that in the preparation of the negative electrode sheet, the compaction density of the negative electrode sheet obtained after cold pressing was 1.69 g / cm 3 by adjusting the pressure, rolling speed, roll gap, pressure holding time and rolling times in the compaction process.

[0189] The preparation method of Example 6 was basically the same as that of Example 1, except that the type of the chamfer of the negative electrode sheet was adjusted. In the preparation of the negative electrode sheet, the chamfer process included: cutting the four corners of the cold-pressed negative electrode sheet to obtain a C-shaped chamfer, and the cutting size was 1.5% of the width of the negative electrode current collector.

[0190] The preparation method of Example 7 is basically the same as that of Example 1, except that the chamfer radius of the negative current collector in the preparation of the negative electrode sheet is adjusted, and the chamfer radius is 0.5% of the width of the negative current collector.

[0191] The preparation method of Example 8 is basically the same as that of Example 1, except that the chamfer radius of the negative current collector in the preparation of the negative electrode sheet is adjusted, and the chamfer radius is 0.8% of the width of the negative current collector.

[0192] The preparation method of Example 9 is basically the same as that of Example 1, except that the chamfer radius of the negative current collector in the preparation of the negative electrode sheet is adjusted, and the chamfer radius is 2% of the width of the negative current collector.

[0193] The preparation method of Example 10 is basically the same as that of Example 1, except that in the preparation of the positive electrode sheet, a chamfering process is performed after cold pressing, and the chamfering process includes: cutting the four corners of the cold-pressed positive electrode sheet to obtain an R-type chamfer, and the chamfer radius is 2.5% of the width of the positive current collector.

[0194] The preparation method of Example 11 is basically the same as that of Example 1, except that the type of graphite in the preparation of the negative electrode sheet is adjusted, and the OI value of the artificial graphite negative active material is 1.7.

[0195] The preparation method of Example 12 is basically the same as that of Example 1, except that the type of graphite in the preparation of the negative electrode sheet is adjusted, and the OI value of the artificial graphite negative active material is 2.5.

[0196] The preparation method of Example 13 is basically the same as that of Example 1, except that the type of graphite in the preparation of the negative electrode sheet is adjusted, and the OI value of the artificial graphite negative active material is 2.95.

[0197] The preparation method of Example 14 is basically the same as that of Example 1, except that the type of graphite in the preparation of the negative electrode sheet is adjusted, and the OI value of the artificial graphite negative active material is 3.5.

[0198] The preparation method of Example 15 is basically the same as that of Example 1, except that the injection coefficient in the assembly of the battery is adjusted, and the injection coefficient of the battery monomer is 2.7 g / Ah.

[0199] The preparation method of Example 16 is basically the same as that of Example 1, except that the injection coefficient in the assembly of the battery is adjusted, and the injection coefficient of the battery monomer is 3 g / Ah.

[0200] The preparation method of Example 17 is basically the same as that of Example 1, except that the injection coefficient in the assembly of the battery is adjusted, and the injection coefficient of the battery monomer is 3.2 g / Ah.

[0201] The preparation method of Example 18 is basically the same as that of Example 1, except that the injection coefficient in the assembly of the battery is adjusted, and the injection coefficient of the battery cell is 4 g / Ah.

[0202] The preparation method of Example 19 is basically the same as that of Example 1, except that the size of the current collector in the preparation of the negative electrode sheet and the positive electrode sheet is adjusted, and the size of the negative current collector in the length and width directions is sequentially reduced by 22 μm along the stacking direction of the electrode assembly; the size of the positive current collector in the length and width directions is sequentially reduced by 22 μm along the stacking direction of the electrode assembly.

[0203] The preparation method of Example 20 is basically the same as that of Example 1, except that the size of the current collector in the preparation of the negative electrode sheet and the positive electrode sheet is adjusted, and the size of the negative current collector in the length and width directions is sequentially reduced by 91 μm along the stacking direction of the electrode assembly; the size of the positive current collector in the length and width directions is sequentially reduced by 91 μm along the stacking direction of the electrode assembly.

[0204] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that the preparation of the positive electrode sheet and the preparation of the negative electrode sheet do not have a chamfering process step.

[0205] The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that in the preparation of the positive electrode sheet and the preparation of the negative electrode sheet, the chamfering process is only processed on the negative electrode sheet along the length direction of the electrode assembly and away from the end of the tab.

[0206] The preparation method of Comparative Example 3 is basically the same as that of Example 1, except that the single-sided coating area density of the negative electrode slurry in the preparation of the negative electrode sheet is adjusted, and the negative electrode slurry is double-sided coated on the double-sided surface of the copper foil with a thickness of 8 μm according to a single-sided coating area density of 155 mg / 1540.25 mm 2 .

[0207] The preparation method of Comparative Example 4 is basically the same as that of Example 1, except that the single-sided coating area density of the negative electrode slurry in the preparation of the negative electrode sheet is adjusted, and the negative electrode slurry is double-sided coated on the double-sided surface of the copper foil with a thickness of 8 μm according to a single-sided coating area density of 220 mg / 1540.25 mm 2 .

[0208] The preparation method of Comparative Example 5 is basically the same as that of Example 1, except that in the preparation of the negative electrode sheet, by adjusting the pressure size, the rolling speed, the roll gap, the pressure holding time, and the rolling times in the compaction process, the compaction density of the negative electrode sheet obtained after cold pressing is 1.33 g / cm 3 .

[0209] The preparation method of Comparative Example 6 is basically the same as that of Example 1, except that in the preparation of the negative electrode sheet, the compaction density of the negative electrode sheet obtained through cold pressing is 1.80 g / cm by adjusting the pressure size, the calendering speed, the roll gap, the pressure holding time and the calendering times in the compaction process. 3 .

[0210] Performance test

[0211] 1. OI value test

[0212] In the present application, the OI value can be tested by using an X-ray diffractometer (such as Bruker D8 Discover), and can be obtained according to JIS K0131-1996, JB / T 4220-2011, to obtain the X-ray diffraction pattern of the negative electrode film layer, and the OI value of the negative electrode film layer is calculated according to OI value = I 004 / I 110 . I 004 is the integral area of the diffraction peak of the crystalline carbon 004 crystal plane in the negative electrode film layer, and I 110 is the integral area of the diffraction peak of the 110 crystal plane of the crystalline carbon in the negative electrode film layer. In the X-ray diffraction analysis test of the present application, a copper target can be used as an anode target, Cu K a ray is used as the radiation source, the wavelength of the ray is = 1.5418 Å, the scanning 2 theta angle range is 20°-80°, and the scanning rate is 4° / min.

[0213] 2. Battery energy density test method

[0214] The battery cells prepared in each example and comparative example are placed at 25°C for 2h to ensure that the temperature of the battery cell is 25°C. After charging the battery cell to a charge cut-off voltage of 3.75V at 1 / 3C at 25°C, constant voltage charging is continued at the charge cut-off voltage until the current is 0.05C, and the charge cut-off (wherein C represents the rated capacity of the battery cell). After the battery cell is placed at 25°C for 1h, the battery cell is discharged to a discharge cut-off voltage of 2.0V at 0.33C at 25°C, and the total discharge energy of the battery cell is recorded as E0.

[0215] The volume of the battery cell is measured as V0, and the unit is L.

[0216] The volume energy density of the battery cell = the discharge energy E0 of the battery cell / the volume V0 of the battery cell, and the unit is Wh / L.

[0217] 3. Cycle performance test method

[0218] The battery cell prepared in each example and comparative example was charged at 25℃ with 1C constant current to 50% SOC, then charged with 0.87C to 80% SOC, and then charged to 3.75V cut-off voltage with 0.33C, and then continued to be charged at the cut-off voltage until the current was 0.05C, and then discharged to 2.0V discharge cut-off voltage with 1C constant current, which was one charge-discharge process. At this time, the discharge capacity of the battery cell was recorded as the discharge capacity E1 of the first cycle of the battery. The charging and discharging were repeated in this way, and after 1000 times, the discharge capacity of the battery cell at this time was recorded as E2. The cycle life @1000Cls = E2 / E1 x 100%.

[0219] 4. Discharge K value test method

[0220] After the cycle, the battery cell was charged at 25℃ with 0.33C constant current to 3.75V, and then continued to be charged at constant voltage until the charging current was less than 0.05C; it was rested for 2h, and the OCV1 was recorded, with the unit of mV, and it was rested for 24h; the voltage was tested, and the OCV2 was recorded, with the unit of mV; K value = (OCV1-OCV2) / 24h, with the unit of mV / h.

[0221] The battery cell of each example and comparative example was prepared according to the above method, and the specific parameters and various performances are shown in Table 1 and Table 2.

[0222] Table 1

[0223]

[0224] Through the comparison of the examples and the comparative examples, it can be seen that the battery cell of the application comprises an electrode assembly, an electrolyte and a shell, the electrode assembly is accommodated in the shell, the material of the shell is a soft package material; the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator, the positive electrode sheet and the negative electrode sheet are alternately stacked, and the separator is arranged between adjacent positive electrode sheets and negative electrode sheets; the negative electrode sheet is provided with a chamfer around the periphery; the projection of the positive electrode sheet along the electrode sheet stacking direction completely falls into the projection of the adjacent negative electrode sheet along the electrode sheet stacking direction; the negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector; the negative electrode film layer has a single-sided coating area density of 170mg / 1540.25mm 2 - 200mg / 1540.25mm 2 , and a compacted density of 1.4g / cm 3 - 1.6cm 3 . At the same time with higher energy density, it has smaller discharge K value after cycle, which means reducing the phenomenon of lithium precipitation of the battery during cycle.

[0225] It can be seen from the comparison of Example 1 and Example 6 that the chamfering of C chamfering or R chamfering can reduce lithium precipitation, and the R chamfering is better for stress dispersion, and the K value after cycling is lower.

[0226] It can be seen from the comparison of Example 1 and Example 7-9, Example 10 that when the radius of the R chamfering is 0.5%-2.5% of the width of the negative electrode sheet, and further 0.8%-2%, the energy density of the battery and the inhibition of lithium precipitation are considered.

[0227] Table 2

[0228]

[0229] It can be seen from the comparison of Example 1-3 that when the CB value of the battery cell is 1.05-1.15, and further 1.08-1.15, the phenomenon of lithium precipitation during cycling is reduced, the K value after cycling is lower, and the cycle life and energy density are higher.

[0230] It can be seen from the comparison of Example 1 and Example 11-14 that when the OI value of the graphite material is 1.7-5, and further 2.5-3.5, the energy density and cycle performance of the battery are improved.

[0231] It can be seen from the comparison of Example 1 and Example 15-18 that when the injection coefficient of the battery cell is 2.5g / Ah-4g / Ah, and further 2.7g / Ah-3.2g / Ah, the cycle performance of the battery is improved while maintaining a high energy density.

[0232] It can be seen from the comparison of Example 1 and Example 19, 20 that when the length and width of the positive current collector are sequentially reduced in the direction of the electrode sheet stacking in the electrode assembly, 70°≤α1≤85°, 70°≤α2≤85°, and the length and width of the negative current collector are sequentially reduced, 70°≤β1≤85°, 70°≤β2≤85°, the degree of lithium precipitation and the K value after cycling are further reduced.

[0233] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solution of the present application are included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications of the embodiments that can be thought of by those skilled in the art, and other ways constructed by combining part of the components of the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized by, The battery monomer comprises an electrode assembly, an electrolyte and a shell, the electrode assembly is contained in the shell, and the material of the shell is a soft package material; The electrode assembly comprises positive electrode sheets, negative electrode sheets and separators, the positive electrode sheets and the negative electrode sheets are alternately stacked, and the separators are arranged between adjacent positive electrode sheets and negative electrode sheets; The negative electrode sheet is provided with a chamfer around the periphery; The projection of the positive electrode sheet along the sheet stacking direction completely falls within the projection of the adjacent negative electrode sheet along the sheet stacking direction; The projection of the electrode assembly on a first projection plane is a first projection trapezoid, and the first projection plane refers to a plane defined by the width direction and the stacking direction of the electrode assembly; The projection of the electrode assembly on a second projection plane is a second projection trapezoid, and the second projection plane refers to a plane defined by the length direction and the stacking direction of the electrode assembly; The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector, the negative electrode film layer having a single-sided coating surface density of 170 mg / 1540.25 mm 2 - 200 mg / 1540.25 mm 2 ; The compacted density of the negative electrode film layer in a full state is 1.4 g / cm 3 -1.6 g / cm 3 .

2. The battery cell of claim 1, wherein, In the full discharge state, the single-side thickness of the negative electrode film layer is 70-90 mu m.

3. The battery cell of claim 1, wherein, In the full discharge state, the single-side thickness of the negative electrode film layer is 75-90 mu m.

4. The battery cell of claim 1, wherein, The chamfer comprises a C-shaped chamfer.

5. The battery cell of claim 1, wherein, The chamfer comprises an R-shaped chamfer.

6. The battery cell of claim 5, wherein, The radius of the R-shaped chamfer is 0.5-2.5% of the width of the negative electrode current collector.

7. The battery cell of claim 5, wherein, The radius of the R-shaped chamfer is 0.8-2% of the width of the negative electrode current collector.

8. The battery cell of claim 4, wherein, The size of the C-shaped chamfer is 0.5-1.5% of the width of the negative electrode current collector.

9. The battery cell of claim 1, wherein, The ratio of the size difference between any adjacent negative electrode sheet and positive electrode sheet in the length or width direction to the size of the negative electrode sheet in the direction is 0.5-1.5%.

10. The battery cell of claim 1, wherein, The CB value of the battery monomer is 1.05-1.15, wherein the CB value represents the ratio of the capacity of the negative electrode sheet to the capacity of the positive electrode sheet per unit area.

11. The battery cell of claim 1, wherein, The CB value of the battery monomer is 1.08-1.15, wherein the CB value represents the ratio of the capacity of the negative electrode sheet to the capacity of the positive electrode sheet per unit area.

12. The battery cell of claim 1, wherein, The negative electrode film layer includes a negative electrode active material including a graphite material having an OI value of 1.7 to 5, wherein the OI value = I 004 / I 110 , I 004 is an integral area of a diffraction peak of a 004 crystal plane in X-ray diffraction analysis, I 110 is an integral area of a diffraction peak of a 110 crystal plane.

13. The battery cell of claim 1, wherein, The negative electrode film layer includes a negative electrode active material including a graphite material, the graphite material having an OI value of 2.5-3.5, wherein OI value = I 004 / I 110 , I 004 is an integral area of a diffraction peak of a 004 crystal plane in X-ray diffraction analysis, I 110 is an integral area of a diffraction peak of a 110 crystal plane.

14. The battery cell of claim 1, wherein, The injection coefficient of the battery monomer is 2.5-4 g / Ah.

15. The battery cell of claim 1, wherein, The injection coefficient of the battery monomer is 2.7-3.2 g / Ah.

16. The battery cell of claim 1, wherein, Along the sheet stacking direction in the electrode assembly, the size of the negative electrode current collector in the length or width direction is sequentially decreased by ΔL1, respectively, wherein 15 mu m≤ΔL1≤120 mu m.

17. The battery cell of claim 16, wherein, The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, and along the sheet stacking direction in the electrode assembly, the size of the positive electrode current collector in the length or width direction is sequentially decreased by ΔL2, respectively, wherein 15 mu m≤ΔL2≤120 mu m.

18. The battery cell of claim 1, wherein, The first projection trapezoid is an isosceles trapezoid.

19. The battery cell of claim 1, wherein, The second projection trapezoid is an isosceles trapezoid.

20. The battery cell of claim 1, wherein, The two included angles formed by the leg of the first projection trapezoid and the longer base of the first projection trapezoid are respectively alpha1 and alpha2, wherein 70°≤alpha1≤85°, and 75°≤alpha2≤85°.

21. The battery cell of claim 20, wherein, α1=α2。 22. The battery cell of claim 1, wherein, Two angles formed by the waist of the second projected trapezoid and the longer base of the second projected trapezoid are β1 and β2 respectively, wherein 70°≤β1≤85°, 70°≤β2≤85°.

23. The battery cell of claim 22, wherein, β1=β2。 24. The battery cell of claim 1, wherein, The positive pole piece is also provided with a chamfer around.

25. The battery cell of claim 1, wherein, The thickness of the negative pole current collector is 6-10 μm.

26. The battery cell of claim 1, wherein, The positive pole piece includes a positive pole current collector and a positive pole film layer arranged on at least one side of the positive pole current collector, and the thickness of the positive pole current collector is 12-15 μm.

27. The battery cell of claim 1, wherein, The positive pole piece includes a positive pole current collector and a positive pole film layer arranged on at least one side of the positive pole current collector, and the length of the positive pole current collector is 520-570 mm.

28. The battery cell of claim 1, wherein, The length of the negative pole current collector is 520-570 mm.

29. The battery cell of claim 1, wherein, The positive pole piece includes a positive pole current collector and a positive pole film layer arranged on at least one side of the positive pole current collector, and the width of the positive pole current collector is 100-130 mm.

30. The battery cell of claim 1, wherein, The width of the negative pole current collector is 100-130 mm.

31. A battery device, characterized by The battery device includes the battery cell of any one of claims 1-30.

32. The battery device of claim 31, wherein, The battery device includes at least one of a battery module, a battery pack, and an energy storage device.

33. An electrical device, comprising: The battery device includes the battery cell of any one of claims 1-30 or the battery device of claim 31.

Images