Battery cell, battery device and electric device

Abstract

The invention provides a battery monomer, a battery device and a power utilization device, the battery monomer comprises an electrode assembly, an electrolyte and a shell, the electrode assembly is accommodated in the shell, and the material of the shell is a soft package material; the electrode assembly comprises positive pole pieces, negative pole pieces and diaphragms, the positive pole pieces and the negative pole pieces are alternately stacked, and the diaphragms are arranged between the adjacent positive pole pieces and negative pole pieces; chamfers are arranged on the periphery of the negative pole piece; the projection of the positive pole piece in the pole piece lamination direction completely falls into the projection of the adjacent negative pole piece in the pole piece lamination direction; the positive pole piece comprises a positive pole piece and a negative pole piece, the negative pole piece comprises a negative pole current collector and a negative pole film layer arranged on at least one side of the negative pole current collector, the single-side coating surface density is 170 mg / 1540.25 mm < 2 >-200 mg / 1540.25 mm < 2 >, and the ratio of the size difference value of any adjacent negative pole piece and positive pole piece in any length or width direction to the size of the negative pole piece in the direction is 0.5%-1.5%.

Description

[0001] This application is a divisional application based on the invention with application number 202510781738.4, application date June 12, 2025, applicant CATL, and invention title "Battery Cell, Battery Device and Power Consumption Device". Technical Field

[0002] This application relates to the field of battery cell technology, and more particularly to a battery cell, a battery device, and an electrical device. Background Technology

[0003] In recent years, battery cells have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, and aerospace.

[0004] With the rapid iteration and updates of national and industry standards for energy storage batteries and power batteries, the requirements for energy density, safety and cycle performance of battery cells are increasing year by year. Existing technologies cannot simultaneously improve these performances, which has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of the above problems, this application provides a battery cell, a battery device, and an electrical device, which are described below.

[0006] The first aspect of this application provides a battery cell, including an electrode assembly, an electrolyte, and a housing. The electrode assembly is housed within the housing, and the housing is made of a flexible pack material. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The positive and negative electrode are alternately stacked, and the separator is disposed between adjacent positive and negative electrode sheets. Each negative electrode has chamfered edges on all four sides. The projection of the positive electrode along the electrode stacking direction completely falls within the projection of the adjacent negative electrode along the electrode stacking direction. The negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer, in a fully loaded state, has a single-sided coating surface density of 170 mg / 1540.25 mm². 2 - 200mg / 1540.25mm 2 The compacted density is 1.4 g / cm³. 3 -1.6g / cm 3 .

[0007] Using a flexible packaging material as the shell, positive and negative electrode sheets are stacked. A thick coating process is adopted in the film layer. When the negative electrode film is fully loaded, the coating surface density on one side is 170mg / 1540.25mm. 2 -200mg / 1540.25mm 2This process improvement is beneficial for increasing the volumetric energy density of batteries. However, it also brings new technical challenges: On the one hand, the stacked electrode assembly uses soft-pack materials for thermo-press packaging. The soft-pack materials shrink and undergo plastic deformation at high temperatures, which can lead to stress concentration at the edges and corners of the electrode assembly. This can cause abnormal spacing between the stacked electrodes, especially at the corners, leading to lithium plating and deteriorating the long-term safety of the battery. On the other hand, the thick coating process increases the lithium-ion transport path, which increases the resistance to ion transport. This can lead to local over-polarization of the electrode, a decrease in the negative electrode potential, and promote the deposition of metallic lithium on the negative electrode surface, which also affects the battery's safety and cycle life.

[0008] In this application, the projection of the positive electrode sheet along the electrode stacking direction completely falls within the projection of the adjacent negative electrode sheet along the electrode stacking direction. The non-projection area, acting as an overhang, reduces lithium plating during charging. Furthermore, by setting chamfers around the larger negative electrode sheet, the stress concentration at the corners caused by the shrinkage of the pouch material can be dispersed. On the other hand, the edge stress mainly acts on the overhang area, reducing the impact on the overlapping area of ​​the positive and negative electrode sheets. This ensures a tight fit and complete interface in the overlapping area, thereby suppressing the safety risks caused by stress-induced lithium plating at the edges and corners. Compared to hard-shell batteries, pouch batteries have less space for electrolyte in the casing. Therefore, using a lower compaction density in the negative electrode film layer can increase the porosity of the negative electrode film layer and improve its liquid retention rate. This reduces the risk of lithium plating due to the long lithium-ion transport path in thick coating layers and also reduces the risk of low electrolyte levels in pouch stacked batteries during long cycles, thus improving the battery's cycle life. Under normal circumstances, the specific capacity of the negative electrode active material is much greater than that of the positive electrode active material. Therefore, the compaction density of the negative electrode film has little impact on the energy density of the battery, while taking into account the energy density of the battery.

[0009] In any embodiment, under full discharge state, the thickness of the negative electrode film layer on one side is 70μm-90μm, and can be selected as 75μm-90μm.

[0010] Studies have shown that under fully discharged conditions, if the thickness of the negative electrode film on one side is too small, the battery capacity will be unable to meet the growing market demand; if the thickness is too large, it will easily lead to problems such as decreased kinetics and lithium plating. A negative electrode film thickness within the aforementioned range is beneficial for further improving battery capacity while also addressing the lithium plating issue.

[0011] In any embodiment, the chamfer includes one of a C-type chamfer and an R-type chamfer, and may be selected as an R-type chamfer.

[0012] R-type chamfers are circular chamfers that achieve a smooth transition, resulting in uniform stress distribution and reducing stress concentration points. However, they require the use of fillet tools with specific radii, leading to higher tool costs. Furthermore, changing tools to accommodate fillets with different radii may increase production costs and time. C-type chamfers are 45° bevels where adjacent faces are removed by the same dimension. They can be achieved using standard bevel tools or by adjusting the tool's feed angle. They offer greater tool versatility and relatively lower costs, but their effect on reducing stress concentration is not as significant as that of R-type chamfers.

[0013] In any embodiment, the radius of the R-shaped chamfer is 0.5%-2.5% of the width of the negative electrode current collector, and can be selected as 0.8%-2%.

[0014] Choosing the radius of the R-shaped chamfer within the above range can both disperse edge stress and reduce the probability of edge lithium plating, while maximizing the coating area to give the battery high energy density and capacity.

[0015] In any embodiment, the size of the C-shaped chamfer is 0.5%-1.5% of the width of the negative electrode current collector.

[0016] When the size of the C-shaped chamfer is within the above range, the probability of edge lithium plating can also be reduced, and the coating area of ​​the negative electrode film can be increased, so that the battery has both high energy density and cycle performance.

[0017] In any embodiment, the ratio of the dimensional difference between any adjacent negative electrode and positive electrode in any direction of length or width to the dimensional difference of the negative electrode in that direction is 0.5%-1.5%.

[0018] The ratio of the length or width of the negative electrode and the positive electrode is within the above range. The negative electrode has an overhang region, which reduces lithium plating during charging and takes into account the area of ​​the positive electrode, i.e. the coating area, further improving the capacity and energy density of the battery cell.

[0019] In any embodiment, the CB value of the battery cell ranges from 1.05 to 1.15, and can be selected as 1.08 to 1.15, where the CB value represents the ratio of the capacity of the negative electrode to the capacity of the positive electrode per unit area.

[0020] The embodiments of this application further reduce the high lithium plating risk in the battery by designing the CB value of the battery cell to be 1.05-1.15, while also improving the battery's first efficiency and cycle life.

[0021] In any embodiment, the negative electrode film layer includes a negative electrode active material, which includes graphite material, wherein the OI value of the graphite material is 1.7-5, optionally 2.5-3.5, wherein the OI value = I 004 / I 110 I 004 I represents the integrated area of ​​the diffraction peak of the 004 crystal plane in X-ray diffraction analysis. 110 The integral area of ​​the diffraction peak on the 110 crystal plane.

[0022] The OI value represents the degree of order of a material along the 004 or 110 crystal plane. A high OI value indicates that the graphite material is more anisotropic, with more concentrated expansion and contraction in a certain direction, which is detrimental to structural stability and the uniformity of lithium-ion insertion / extraction. A low OI value indicates that the negative electrode active material has higher lithium insertion uniformity, increasing the effective lithium insertion end faces in the negative electrode film. When the OI value of the graphite material is within the above range, it means that the graphite material tends to be isotropic, thus exhibiting more uniform volume change during charge and discharge, thereby extending the battery's cycle life. It also better ensures sufficient electrolyte residue at the interface, while improving the solid-liquid transport rate of lithium ions, thereby suppressing lithium plating under long-term cycling and balancing the long-term safety and lifespan of the battery.

[0023] In any embodiment, the electrolyte injection coefficient of the battery cell is 2.5g / Ah-4g / Ah, and can be selected as 2.7g / Ah-3.2g / Ah.

[0024] The electrolyte injection coefficient refers to the ratio of the mass (g) of injected electrolyte to the capacity (Ah) of a single battery cell. Controlling the electrolyte injection coefficient of lithium-ion batteries within the above-mentioned range reduces the risk of lithium plating caused by localized "drying out" of the electrode surface due to the limited expansion suppression effect of pouch cells during long-term cycling, which can lead to insufficient electrolyte and subsequent lithium plating.

[0025] In any embodiment, along the electrode stacking direction in the electrode assembly, the dimensions of the negative electrode current collector decrease independently by ΔL1 in either the length or width direction, wherein 15μm≤ΔL1≤120μm.

[0026] In any embodiment, along the electrode stacking direction in the electrode assembly, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, wherein the size of the positive current collector decreases independently by ΔL2 in either the length or width direction, wherein 15μm≤ΔL2≤120μm.

[0027] Along the stacking direction, the length and / or width of the negative electrode current collector and the positive electrode current collector decrease sequentially. This results in better uniformity when the soft-pack material is sealed, reduces the probability of wrinkles at the edges of the current collector, and not only covers the surface of the outermost electrode sheet, but also participates in stress dispersion in the middle of the stack, further reducing lithium plating at the edges and corners of the electrode assembly, and improving battery safety and cycle life.

[0028] In any embodiment, the projection of the battery cell onto the first projection plane is a first projection trapezoid, which may 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.

[0029] In any embodiment, the projection of the battery cell onto the second projection plane is a second projection trapezoid, which may 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.

[0030] The cross-section of the electrode assembly projected on the first projection plane is trapezoidal, and / or the cross-section of the electrode assembly projected on the second projection plane is trapezoidal. This can effectively disperse the stress applied to the electrode assembly, especially the edges and corners, by the soft-pack material shell during the heat sealing process. The isosceles trapezoidal battery cell structure balances the stress on different sides, further reducing the possibility of lithium plating due to stress concentration.

[0031] In any embodiment, the angles formed by the waist of the first projected trapezoid and the longer base of the first projected trapezoid are α1 and α2, respectively, wherein 70°≤α1≤85°, 75°≤α2≤85°, and α1=α2 can be selected.

[0032] In any embodiment, the 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° and 70°≤β2≤85°, and β1=β2 can be selected.

[0033] The two included angles formed by the waist of the first projected trapezoid and the base of the first projected trapezoid, and / or the two included angles formed by the waist of the second projected trapezoid and the longer base of the second projected trapezoid, are within the above range. This optimizes the stress distribution and reduces the impact of excessively large angles on the coating area of ​​the active material, thus taking into account the energy density of the battery.

[0034] In any embodiment, the positive electrode sheet is also provided with chamfers around its perimeter.

[0035] The absence of chamfers on the positive electrode eliminates the need for a cutting process, preventing burrs or active material shedding from the current collector and direct exposure to the electrolyte. However, this lack of chamfers, when combined with chamfered negative electrodes, restricts the size of the positive electrode to avoid right angles extending beyond the negative electrode's perimeter, which could lead to lithium plating or short circuits due to puncture of the separator. This results in wasted area. Chamfering the positive electrode not only reduces stress at the corners but also increases its size, maximizing the overlap between its projection and that of the negative electrode, thus improving the energy density of the battery cell.

[0036] In any embodiment, the thickness of the negative electrode current collector is 6μm-10μm.

[0037] In any embodiment, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, wherein the thickness of the positive current collector is 12μm-15μm.

[0038] The thickness of the current collector within the above range is beneficial to improving the mechanical strength of the pouch cell and enhancing its resistance to expansion. On the other hand, it can increase the current flow area, thereby reducing the internal resistance of the electrode and suppressing internal heating, thus improving the safety and long lifespan of the battery.

[0039] In any embodiment, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed 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 520mm-570mm.

[0040] In any embodiment, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed 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 100mm-130mm.

[0041] The length and width of the positive electrode current collector and / or negative electrode current collector are within the above range. On the one hand, this is beneficial to enhance heat dissipation and improve the cycle life of the battery. On the other hand, battery cells with current collectors of the above dimensions can be adapted to the space of existing modules and battery packs, and improve the packing efficiency, achieving higher energy density at the module and battery pack levels.

[0042] A second aspect of this application provides a battery device including the battery cell of the first aspect of this application.

[0043] A third aspect of this application provides an electrical device, including at least one of the battery cell of the first aspect of this application and the battery device of the second aspect of this application. Attached Figure Description

[0044] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0045] Figure 1 This is a top view of an electrode assembly according to one embodiment of this application; Figure 2 This is a front view schematic diagram of an electrode assembly according to one embodiment of this application; Figure 3 This is a three-dimensional schematic diagram of the electrode assembly in one embodiment of this application; Figure 4 This is a three-dimensional schematic diagram of a battery cell according to one embodiment of this application; Figure 5 This is a schematic diagram of an electrical device according to one embodiment of this application.

[0046] Explanation of reference numerals in the attached figures: 1. Electrode assembly, 11. Separator, 12. Positive electrode, 121. First positive electrode, 13. Negative electrode, 131. First negative electrode, 132. Second negative electrode, 14. Positive electrode tab, 15. Negative electrode tab, 5. Cell battery. Detailed Implementation

[0047] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery device, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0048] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0049] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0050] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0051] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0052] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0053] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0054] 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.

[0055] 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.

[0056] A single battery cell is the smallest unit that makes up a battery, and it can independently perform the functions of charging and discharging.

[0057] A single battery cell includes electrode components and an electrolyte.

[0058] 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.

[0059] 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.

[0060] 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).

[0061] 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.

[0062] In some implementations, the battery can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0063] In some implementations, individual battery cells can be assembled into a battery module. The number of battery cells in a battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. Within the battery module, the multiple battery cells can be arranged sequentially along the length of the battery module. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells can be secured using fasteners.

[0064] Optionally, the battery module may also include a housing with a receiving space in which multiple battery cells are housed.

[0065] In some embodiments, the battery modules 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.

[0066] The battery pack may include a housing and multiple battery modules disposed within the housing. The housing may include an upper housing and a lower housing, with the upper housing covering the lower housing and forming a closed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the housing.

[0067] With the development of the battery industry, the requirements for individual battery cells are constantly increasing, and the energy density standards for energy storage batteries and power batteries are rising year by year. Current technologies mainly improve upon these requirements through the following technical paths: adopting a stacked electrode assembly design, which can improve space utilization by 5%-8% compared to traditional wound structures, and increasing the loading of active materials in the battery cell; using a soft-pack casing, which is lighter and further increases battery loading and energy density; and employing a thick coating process in electrode fabrication to increase the areal density of active materials and relatively reduce the proportion of inactive materials such as current collectors and separators, thereby improving volumetric energy density. However, research shows that the probability of lithium plating in battery cells using these methods increases significantly, affecting the battery's cycle life and safety. Therefore, how to simultaneously ensure high energy density while maintaining good cycle life and safety remains a pressing technical problem that needs to be solved.

[0068] The first aspect of this application provides a battery cell, characterized in that it includes an electrode assembly, an electrolyte, and a housing, wherein the electrode assembly is housed within the housing, and the housing is made of a flexible material; the electrode assembly includes a positive electrode, a negative electrode, and a separator, wherein the positive and negative electrode are alternately stacked, and the separator is disposed between adjacent positive and negative electrode sheets; each negative electrode has chamfered edges on all four sides; the projection of the positive electrode along the electrode stacking direction completely falls within the projection of the adjacent negative electrode along the electrode stacking direction; the negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, wherein the negative electrode film layer, in a fully loaded state, has a single-sided coating surface density of 170 mg / 1540.25 mm². 2 -200mg / 1540.25mm 2 The compacted density is 1.4 g / cm³. 3 -1.6g / cm 3 .

[0069] Using a flexible packaging material as the shell, positive and negative electrode sheets are stacked. A thick coating process is adopted in the film layer. When the negative electrode film is fully loaded, the coating surface density on one side is 170mg / 1540.25mm. 2 -200mg / 1540.25mm 2 This process improvement is beneficial for increasing the volumetric energy density of batteries. However, it also brings new technical challenges: On the one hand, the stacked electrode assembly uses soft-pack materials for thermo-press packaging. The soft-pack materials shrink and undergo plastic deformation at high temperatures, which can lead to stress concentration at the edges and corners of the electrode assembly. This can cause abnormal spacing between the stacked electrodes, especially at the corners, leading to lithium plating and deteriorating the long-term safety of the battery. On the other hand, the thick coating process increases the lithium-ion transport path, which increases the resistance to ion transport. This can lead to local over-polarization of the electrode, a decrease in the negative electrode potential, and promote the deposition of metallic lithium on the negative electrode surface, which also affects the battery's safety and cycle life.

[0070] In this application, the projection of the positive electrode sheet along the electrode stacking direction completely falls within the projection of the adjacent negative electrode sheet along the electrode stacking direction. The non-projection area, acting as an overhang, reduces lithium plating during charging. Furthermore, by setting chamfers around the larger negative electrode sheet, the stress concentration at the corners caused by the shrinkage of the pouch material can be dispersed. On the other hand, the edge stress mainly acts on the overhang area, reducing the impact on the overlapping area of ​​the positive and negative electrode sheets. This ensures a tight fit and complete interface in the overlapping area, thereby suppressing the safety risks caused by stress-induced lithium plating at the edges and corners. Compared to hard-shell batteries, pouch batteries have less space for electrolyte in the casing. Therefore, using a lower compaction density in the negative electrode film layer can increase the porosity of the negative electrode film layer and improve its liquid retention rate. This reduces the risk of lithium plating due to the long lithium-ion transport path in thick coating layers and also reduces the risk of low electrolyte levels in pouch stacked batteries during long cycles, thus improving the battery's cycle life. Under normal circumstances, the specific capacity of the negative electrode active material is much greater than that of the positive electrode active material. Therefore, the compaction density of the negative electrode film has little impact on the energy density of the battery, while taking into account the energy density of the battery.

[0071] In some embodiments, the surface area density of the negative electrode film layer in the fully discharged state can be selected as 170 mg / 1540.25 mm². 2 175mg / 1540.25mm 2 180mg / 1540.25mm 2 185mg / 1540.25mm 2 190mg / 1540.25mm 2 195mg / 1540.25mm 2 200mg / 1540.25mm 2 Or the range of values ​​between any two of the above.

[0072] In this application, the areal density of the negative electrode film layer on one side has a meaning known in the art and can be tested using methods known in the art. For example, take a negative electrode sheet that has been coated on one side and compacted (if it is a negative electrode sheet with double-sided coating, the negative electrode film layer on one side can be wiped off first), cut it into a small circular piece with an area of ​​S1, weigh it, and record its weight as M1. Then wipe off the negative electrode film layer of the above-weighed negative electrode sheet, weigh the current collector, and record it as M0. The areal density of the negative electrode film layer on one side = (M1-M0) / S1. To ensure the accuracy of the test results, multiple groups (e.g., 10 groups) of test samples can be tested, and the average value can be calculated as the test result.

[0073] In some embodiments, the compaction density of the negative electrode film layer in its fully loaded state can be selected as 1.4 g / cm³. 3 1.41 g / cm3 1.42g / cm 3 1.43 g / cm 3 1.44 g / cm 3 1.45g / cm 3 1.46 g / cm 3 1.47 g / cm 3 1.48g / cm 3 1.49 g / cm 3 1.50g / cm 3 1.51g / cm 3 1.52g / cm 3 1.53g / cm 3 1.54g / cm 3 1.55g / cm 3 1.56g / cm 3 1.57g / cm 3 1.58g / cm 3 1.59g / cm 3 1.6g / cm 3 Or the range of values ​​between any two of the above.

[0074] In this application, the fully discharged state refers to the state after the battery is placed in a 25°C oven environment, left to stand for 2 hours, and the battery temperature is maintained at 25°C. The battery is then discharged at a constant current of 1 / 3C to 2.0V, left to stand for half an hour, and then discharged at a constant current of 0.04C to 2.0V.

[0075] The compaction density of the negative electrode film can be tested using methods known in the art. As an example, the battery is placed in a 25°C oven environment and left to stand for 2 hours. After the battery temperature is maintained at 25°C, the battery is discharged at a constant current of 1 / 3C to 2.0V, left to stand for half an hour, and then discharged at a constant current of 0.04C to 2.0V. The battery is then disassembled to obtain the negative electrode sheet. The residual electrolyte is treated with dimethyl carbonate solvent, the electrode sheet is dried, and it is cut into small circular pieces with an area of ​​S. The mass of the circular pieces is obtained as W1, and the thickness of the negative electrode sheet is measured using a micrometer. Then, the negative electrode film layer of the weighed electrode sheet is wiped off, the mass of the current collector is weighed and recorded as W2, and the thickness of the current collector is measured using a micrometer. The compaction density of the negative electrode film layer is then PD = (W1-W2) / [(T1-T2)×S].

[0076] In some embodiments, under full discharge conditions, the thickness of the negative electrode film layer on one side is 70μm-90μm, and can be selected as 75μm-90μm.

[0077] In some embodiments, under full discharge conditions, the thickness of one side of the negative electrode film can be selected as 70μm, 71μm, 72μm, 73μm, 74μm, 75μm, 75.1μm, 76μm, 76.1μm, 77μm, 78μm, 79μm, 80μm, 81μm, 82μm, 82.8μm, 83μm, 84μm, 85μm, 85.8μm, 86μm, 87μm, 88μm, 89μm, 89.6μm, 90μm, or any value range between the above two.

[0078] Studies have shown that under fully discharged conditions, if the thickness of the negative electrode film on one side is too small, the battery capacity will be unable to meet the growing market demand; if the thickness is too large, it will easily lead to problems such as decreased kinetics and lithium plating. A negative electrode film thickness within the aforementioned range is beneficial for further improving battery capacity while also addressing the lithium plating issue.

[0079] In some embodiments, the chamfer includes one of a C-shaped chamfer and an R-shaped chamfer, and may be selected as an R-shaped chamfer.

[0080] R-type chamfers are circular chamfers that achieve a smooth transition, resulting in uniform stress distribution and reducing stress concentration points. However, they require the use of fillet tools with specific radii, leading to higher tool costs. Furthermore, changing tools to accommodate fillets with different radii may increase production costs and time. C-type chamfers are 45° bevels where adjacent faces are removed by the same dimension. They can be achieved using standard bevel tools or by adjusting the tool's feed angle. They offer greater tool versatility and relatively lower costs, but their effect on reducing stress concentration is not as significant as that of R-type chamfers. In some embodiments, the radius of the R-shaped chamfer is 0.5%-2.5% of the width of the negative electrode current collector, and can be selected as 0.8%-2%.

[0081] In some embodiments, the radius of the chamfer R can be selected as 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 sheet, or a value range between any two of the above.

[0082] Choosing the radius of the R-shaped chamfer within the above range can both disperse edge stress and reduce the probability of edge lithium plating, while maximizing the coating area to give the battery high energy density and capacity.

[0083] In some embodiments, the size of the C-shaped chamfer is 0.5%-1.5% of the width of the negative electrode current collector.

[0084] In some embodiments, the size of the C-shaped chamfer can be selected as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5% of the width of the negative electrode current collector, or a value range between any two of the above.

[0085] When the size of the C-shaped chamfer is within the above range, the probability of edge lithium plating can also be reduced, and the coating area of ​​the negative electrode film can be increased, so that the battery has both high energy density and cycle performance.

[0086] In some embodiments, along the electrode stacking direction in the electrode assembly, the ratio of the dimensional difference between any adjacent negative electrode and positive electrode in either the length or width direction to the dimensional difference of the negative electrode in that direction is 0.5%-1.5%.

[0087] In some embodiments, along the electrode stacking direction in the electrode assembly, the ratio of the dimensional difference between any adjacent negative electrode and positive electrode in either the length or width direction to the dimensional value of the negative electrode in that direction can be selected as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, or any value range between the two.

[0088] In this application, as an example, the ratio of the dimensional difference between any adjacent negative electrode and positive electrode in any direction of length or width to the dimension of the negative electrode in that direction can be calculated as follows: Figure 2 As shown, it includes a first positive electrode 121, a first negative electrode 131 adjacent to the first positive electrode 121, and a second negative electrode 132 adjacent to the first positive electrode 121. P1 L represents the length of the first positive electrode 121 in the diagram. N1 L represents the length of the first negative electrode plate 131 in the diagram. N2 The length of the second negative electrode in the figure; the ratio of the dimensional difference between adjacent negative and positive electrodes in the length direction to the dimension of the negative electrode 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%.

[0089] Within the above-mentioned range, the ratio of the length to the width of the negative electrode and the positive electrode is within the range. The negative electrode has an overhang region, which reduces lithium plating during the charging process, and also takes into account the area of ​​the positive electrode, i.e. the coating area, further improving the capacity and energy density of the battery cell.

[0090] In some embodiments, the CB value of the battery cell ranges from 1.05 to 1.15, and can be selected as 1.08 to 1.15, where the CB value represents the ratio of the capacity of the negative electrode to the capacity of the positive electrode per unit area.

[0091] In some embodiments, the CB value of the battery cell can be selected from 1.05, 1.06, 70.7, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, 1.15 or any two of the above.

[0092] The embodiments of this application further reduce the high lithium plating risk in the battery by designing the CB value of the battery cell to be 1.05-1.15, while also improving the battery's first efficiency and cycle life.

[0093] In some embodiments, the negative electrode film layer includes a negative electrode active material, which includes a graphite material, wherein the OI value of the graphite material is 1.7-5, optionally 2.5-3.5, wherein the OI value = I. 004 / I 110 I 004 I represents the integrated area of ​​the diffraction peak of the 004 crystal plane in X-ray diffraction analysis. 110 The integral area of ​​the diffraction peak on the 110 crystal plane.

[0094] In some embodiments, the OI value of the graphite material may be selected as 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 any value range between the above two.

[0095] The OI value represents the degree of order of a material along the 004 or 110 crystal plane. A high OI value indicates that the graphite material is more anisotropic, with more concentrated expansion and contraction in a certain direction, which is detrimental to structural stability and the uniformity of lithium-ion insertion / extraction. A low OI value indicates that the negative electrode active material has higher lithium insertion uniformity, increasing the effective lithium insertion end faces in the negative electrode film. When the OI value of the graphite material is within the above range, it means that the graphite material tends to be isotropic, thus exhibiting more uniform volume change during charge and discharge, thereby extending the battery's cycle life. It also better ensures sufficient electrolyte residue at the interface, while improving the solid-liquid transport rate of lithium ions, thereby suppressing lithium plating under long-term cycling and balancing the long-term safety and lifespan of the battery.

[0096] In some embodiments, the electrolyte injection coefficient of the battery cell is 2.5g / Ah-4g / Ah, and can be selected as 2.7g / Ah-3.2g / Ah.

[0097] In some embodiments, the electrolyte injection coefficient of the battery cell can be selected as 2.5g / Ah, 2.6g / Ah, 2.7g / Ah, 2.8g / Ah, 2.9g / Ah, 3.0g / Ah, 3.1g / Ah, 3.2g / Ah, 3.3g / Ah, 3.4g / Ah, 3.5g / Ah, 3.6g / Ah, 3.7g / Ah, 3.8g / Ah, 3.9g / Ah, 4g / Ah, or any value range between the above two.

[0098] The electrolyte injection coefficient refers to the ratio of the mass (g) of injected electrolyte to the capacity (Ah) of a single battery cell. Controlling the electrolyte injection coefficient of lithium-ion batteries within the above-mentioned range reduces the risk of lithium plating caused by localized "drying out" of the electrode surface due to the limited expansion suppression effect of pouch cells during long-term cycling, which can lead to insufficient electrolyte and subsequent lithium plating.

[0099] In some embodiments, along the electrode stacking direction in the electrode assembly, the dimensions of the negative electrode current collector decrease independently by ΔL1 in either the length or width direction, wherein 15μm≤ΔL1≤120μm.

[0100] In some implementations, ΔL1 can be selected as a value range between any two of the following: 15μm, 20μm, 22μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 91μm, 95μm, 100μm, 105μm, 110μm, 115μm, and 120μm.

[0101] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. Along the electrode stacking direction in the electrode assembly, the size of the positive current collector decreases independently by ΔL2 in either the length or width direction, wherein 15μm≤ΔL2≤120μm.

[0102] In some implementations, ΔL2 can be selected as a value range between any two of the following: 15μm, 20μm, 22μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 91μm, 95μm, 100μm, 105μm, 110μm, 115μm, and 120μm.

[0103] Along the stacking direction, the length and / or width of the negative electrode current collector and the positive electrode current collector decrease sequentially, such as... Figure 3 As shown, this results in better uniformity when the soft-pack material is sealed, reducing the probability of wrinkles at the edges of the current collector. It not only covers the surface of the outermost electrode, but also participates in stress dispersion in the middle electrode, further reducing lithium plating at the edges and corners of the electrode assembly, and improving battery safety and cycle life.

[0104] In some embodiments, the projection of the battery cell onto the first projection plane is a first projection trapezoid, which may 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.

[0105] In some embodiments, the projection of the battery cell onto the second projection plane is a second projection trapezoid, which may 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.

[0106] The cross-section of the electrode assembly projected on the first projection plane is trapezoidal, and / or the cross-section of the electrode assembly projected on the second projection plane is trapezoidal. This can effectively disperse the stress applied to the electrode assembly, especially the edges and corners, by the soft-pack material shell during the heat sealing process. The isosceles trapezoidal battery cell structure balances the stress on different sides, further reducing the possibility of lithium plating due to stress concentration.

[0107] In some embodiments, the angles formed by the waist of the first projected trapezoid and the longer base of the first projected trapezoid are α1 and α2, respectively, wherein 70°≤α1≤85° and 70°≤α2≤85°, and α1=α2 can be selected.

[0108] In some implementations, α1 can be selected as 70°, 71°, 72°, 73°, 74°, 75°, 76°, 77°, 75°, 79°, 80°, 81°, 82°, 83°, 84°, 85° or any value range between the above two.

[0109] In some implementations, α2 can be selected as 70°, 71°, 72°, 73°, 74°, 75°, 76°, 77°, 75°, 79°, 80°, 81°, 82°, 83°, 84°, 85° or any value range between the two above.

[0110] In some embodiments, the 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° and 70°≤β2≤85°, and β1=β2 can be selected.

[0111] In some implementations, β1 can be selected as 70°, 71°, 72°, 73°, 74°, 75°, 76°, 77°, 75°, 79°, 80°, 81°, 82°, 83°, 84°, 85° or any value range between the two above.

[0112] In some implementations, β2 can be selected as 70°, 71°, 72°, 73°, 74°, 75°, 76°, 77°, 75°, 79°, 80°, 81°, 82°, 83°, 84°, 85° or any range between the two above.

[0113] In this application, "the longer base of the projected trapezoid" means that the projected trapezoid has the longer of two parallel bases. The angles formed by the legs of the first projected trapezoid and its longer base are α1 and α2, respectively, and the angles formed by the legs of the second projected trapezoid and its longer base are β1 and β2, respectively. Figure 4 As shown.

[0114] The two included angles formed by the waist of the first projected trapezoid and the longer base of the first projected trapezoid, and / or the two included angles formed by the waist of the second projected trapezoid and the longer base of the second projected trapezoid, are within the above range. This optimizes the stress distribution and reduces the impact of excessively large angles on the coating area of ​​the active material, thus taking into account the energy density of the battery.

[0115] In some embodiments, the positive electrode sheet is also chamfered around all four sides.

[0116] The absence of chamfers on the positive electrode eliminates the need for a cutting process, preventing burrs or active material shedding from the current collector and direct exposure to the electrolyte. However, this lack of chamfers, when combined with chamfered negative electrodes, restricts the size of the positive electrode to avoid right angles extending beyond the negative electrode's perimeter, which could lead to lithium plating or short circuits due to puncture of the separator. This results in wasted area. Chamfering the positive electrode not only reduces stress at the corners but also increases its size, maximizing the overlap between its projection and that of the negative electrode, thus improving the energy density of the battery cell.

[0117] In some embodiments, the chamfer type around the positive electrode is the same as the chamfer type around the negative electrode.

[0118] The positive electrode has the same chamfer type as the negative electrode, which helps to further distribute stress evenly and reduce stress lithium deposition at the edges.

[0119] In some embodiments, the positive electrode sheet has an R-shaped chamfer around its perimeter. The positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The radius of the R-shaped chamfer is 0.5%-2.5% of the width of the positive current collector.

[0120] The positive electrode has an R-shaped chamfer around its perimeter, and the radius of the R-shaped chamfer is selected within the above range. This can reduce edge lithium plating and maximize the coating area, so that the battery has high energy density and capacity.

[0121] In some embodiments, the thickness of the negative electrode current collector is 6 μm-10 μm.

[0122] In some embodiments, the thickness of the negative electrode current collector can be selected as 6μm, 7μm, 8μm, 9μm, 10μm or any value range between the two above.

[0123] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, wherein the thickness of the positive current collector is 12μm-15μm.

[0124] In some embodiments, the thickness of the positive current collector can be selected as 12 μm, 13 μm, 14 μm, 15 μm or any value range between the two mentioned above.

[0125] The thickness of the current collector within the above range is beneficial to improving the mechanical strength of the pouch cell and enhancing its resistance to expansion. On the other hand, it can increase the current flow area, thereby reducing the internal resistance of the electrode and suppressing internal heating, thus improving the safety and long lifespan of the battery.

[0126] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, wherein the length of the positive current collector and / or the negative current collector is 520mm-570mm.

[0127] In some embodiments, the length of the positive current collector and / or the negative current collector may be selected as 520 mm, 530 mm, 540 mm, 550 mm, 560 mm, 570 mm or any value range between the above two.

[0128] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, wherein the width of the positive current collector and / or the negative current collector is 100mm-130mm.

[0129] In some embodiments, the width of the positive current collector and / or the negative current collector may be selected as 100mm, 110mm, 120mm, 130mm or any value range between the two above.

[0130] The length and width of the positive electrode current collector and / or negative electrode current collector are within the above range. On the one hand, this is beneficial to enhance heat dissipation and improve the cycle life of the battery. On the other hand, battery cells with current collectors of the above dimensions can be adapted to the space of existing modules and battery packs, and improve the packing efficiency, achieving higher energy density at the module and battery pack levels. [Positive electrode plate] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0131] In some embodiments, the positive electrode film layer includes a positive electrode active material. The positive electrode active material may be any known positive electrode active material for batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium vanadium oxide, and lithium manganese oxide. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.

[0132] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0133] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0134] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode film layer, such as positive electrode active material, conductive agent, 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 obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0135] [Negative electrode plate] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0136] In some embodiments, the negative electrode film layer may optionally include an adhesive. The adhesive may 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).

[0137] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0138] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0139] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0140] [Electrolytes] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0141] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0142] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0143] In some embodiments, the solvent may 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, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0144] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0145] [Septum] This application does not impose any particular restrictions on the type of diaphragm; any well-known porous diaphragm with good chemical and mechanical stability can be selected.

[0146] In some embodiments, the diaphragm material can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The diaphragm can be a single-layer film or a multi-layer composite film, without particular limitation. When the diaphragm is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0147] [Battery cell] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a lamination process.

[0148] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0149] [Battery Device] This application also provides a battery device, which includes the battery cell provided in this application. In some embodiments, the battery device is one or more of a battery module, a battery pack, and an energy storage device.

[0150] [Electrical appliances] In addition, this application embodiment also provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack provided in this application embodiment. The battery cell, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0151] As the electrical device, a single battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0152] Figure 5 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of individual battery cells, a battery pack or battery module can be used.

[0153] This application also provides an energy storage device, which includes the battery device provided in this application.

[0154] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0155] Example The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0156] Example 1 1) Preparation of positive electrode sheet Preparation of positive electrode film slurry: Lithium iron phosphate positive electrode active material, conductive carbon black and binder PVDF are mixed at a mass ratio of 98:1:1, solvent NMP is added, and the mixture is stirred under vacuum until the system is homogeneous to obtain positive electrode film slurry. The positive electrode film slurry was uniformly coated on both sides of an aluminum foil current collector with a thickness of 15 μm, and the coating density on one side was 385 mg / 1540.25 mm. 2 After being air-dried at room temperature, the material was transferred to an oven for further drying, and then cold-pressed to obtain the positive electrode sheet. The compaction density of the positive electrode film layer was 2.45 g / cm³.3 The aluminum foil current collector has a length of 544 mm and a width of 120.5 mm.

[0157] Along the stacking direction, the length and width of the aluminum foil current collector in the positive electrode do not change.

[0158] 2) Preparation of negative electrode sheet Preparation of negative electrode film slurry: Artificial graphite negative electrode active material, polyvinyl alcohol binder, and SP-Li conductive agent are fully mixed and ball-milled in a deionized water solvent system at a mass ratio of 90:5:5 to obtain negative electrode slurry; wherein, the OI value of the artificial graphite negative electrode active material is 5; The negative electrode film slurry was uniformly coated on both sides of an 8μm thick copper foil current collector, with a single-side coating density of 180mg / 1540.25mm. 2 The material was vacuum dried overnight at 110℃, and then cold-pressed and chamfered to obtain the negative electrode sheet. The compaction density of the negative electrode film was 1.53 g / cm³. 3 The copper foil current collector has a length of 548 mm and a width of 122 mm. The chamfering process includes 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.

[0159] Along the stacking direction, the length and width of the copper foil current collector in the negative electrode sheet do not change.

[0160] 3) Preparation of the diaphragm A polyethylene film with a thickness of 11 μm was used as the diaphragm.

[0161] 4) Preparation of electrolyte Lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonylimide (LiFSI) were dissolved in ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) in a volume ratio of 1:1:1 to form a homogeneous solution, resulting in an electrolyte with a LiPF6 concentration of 0.7 mol / L and a LiFSI concentration of 0.3 mol / L.

[0162] 5) Battery assembly The cut positive and negative electrode sheets are stacked using a Z-shaped stacking method, with the stacking sequence being "positive electrode sheet - separator - negative electrode sheet - separator" to form an electrode assembly. The baked electrode assembly is then placed in an aluminum-plastic film, liquid is injected, vacuum is applied, and the film is heat-sealed to form an airtight package, finally yielding a stacked soft-pack battery cell. The liquid injection coefficient of the battery cell is 2.5 g / Ah, and the CB value is 1.05.

[0163] The preparation method of Example 2 is basically the same as that of Example 1, except that the single-sided coating density of the negative electrode slurry in the preparation of the negative electrode sheet is adjusted. The negative electrode slurry is prepared at a density of 170 mg / 1540.25 mm. 2 The single-sided coating surface density is double-sided coated on both sides of an 8μm thick copper foil.

[0164] The preparation method of Example 3 is basically the same as that of Example 1, except that the single-sided coating density of the negative electrode slurry in the preparation of the negative electrode sheet is adjusted. The negative electrode slurry is prepared at a density of 200 mg / 1540.25 mm. 2 The single-sided coating surface density is double-sided coated on both sides of an 8μm thick copper foil.

[0165] The preparation method of Example 4 is basically the same as that of Example 1, except that in the preparation of the negative electrode sheet, by adjusting the pressure, rolling speed, roll gap, holding time, and number of rolling cycles in the compaction process, the compaction density of the negative electrode sheet obtained after cold pressing is 1.46 g / cm³. 3 .

[0166] The preparation method of 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, rolling speed, roll gap, holding time, and number of rolling cycles in the compaction process, the compaction density of the negative electrode sheet obtained after cold pressing is 1.69 g / cm³. 3 .

[0167] The preparation method of Example 6 is basically the same as that of Example 1, except that the chamfer type of the negative electrode sheet is adjusted. In the preparation of the negative electrode sheet, the chamfering process includes: cutting the four corners of the cold-pressed negative electrode sheet to obtain a C-shaped chamfer, with the cutting size being 1.5% of the width of the negative current collector.

[0168] 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 to 0.5% of the width of the negative current collector.

[0169] 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 to 0.8% of the width of the negative current collector.

[0170] 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 to 2% of the width of the negative current collector.

[0171] 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. The chamfering process includes cutting the four corners of the cold-pressed positive electrode sheet to obtain an R-shaped chamfer, with the chamfer radius being 2.5% of the width of the positive current collector.

[0172] The preparation method of Example 11 is basically the same as that of Example 1, except that the type of graphite is adjusted during the preparation of the negative electrode sheet, and the OI value of the artificial graphite negative electrode active material is 1.7.

[0173] The preparation method of Example 12 is basically the same as that of Example 1, except that the type of graphite is adjusted during the preparation of the negative electrode sheet, and the OI value of the artificial graphite negative electrode active material is 2.5.

[0174] The preparation method of Example 13 is basically the same as that of Example 1, except that the type of graphite is adjusted during the preparation of the negative electrode sheet, and the OI value of the artificial graphite negative electrode active material is 2.95.

[0175] The preparation method of Example 14 is basically the same as that of Example 1, except that the type of graphite is adjusted during the preparation of the negative electrode sheet, and the OI value of the artificial graphite negative electrode active material is 3.5.

[0176] The preparation method of Example 15 is basically the same as that of Example 1, except that the liquid injection coefficient in the battery assembly is adjusted and the liquid injection coefficient of the battery cell is 2.7 g / Ah.

[0177] The preparation method of Example 16 is basically the same as that of Example 1, except that the liquid injection coefficient in the battery assembly is adjusted and the liquid injection coefficient of the battery cell is 3g / Ah.

[0178] The preparation method of Example 17 is basically the same as that of Example 1, except that the liquid injection coefficient in the battery assembly is adjusted and the liquid injection coefficient of the battery cell is 3.2 g / Ah.

[0179] The preparation method of Example 18 is basically the same as that of Example 1, except that the liquid injection coefficient in the battery assembly is adjusted and the liquid injection coefficient of the battery cell is 4g / Ah.

[0180] The preparation method of Example 19 is basically the same as that of Example 1, except that the size of the current collector during the preparation of the negative electrode and the positive electrode is adjusted. Along the electrode stacking direction in the electrode assembly, the size of the negative electrode current collector decreases by 22 μm in both the length and width directions; along the electrode stacking direction in the electrode assembly, the size of the positive electrode current collector decreases by 22 μm in both the length and width directions.

[0181] The preparation method of Example 20 is basically the same as that of Example 1, except that the size of the current collector during the preparation of the negative electrode and the positive electrode is adjusted. Along the electrode stacking direction in the electrode assembly, the size of the negative electrode current collector decreases by 91 μm in both length and width directions; along the electrode stacking direction in the electrode assembly, the size of the positive electrode current collector decreases by 91 μm in both length and width directions.

[0182] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that there is no chamfering process step in the preparation of the positive electrode and the negative electrode.

[0183] The preparation method of Comparative Example 2 is basically the same as that of Example 1. The difference is that in the preparation of the positive electrode sheet and the negative electrode sheet, the chamfering process is only performed on the end of the negative electrode sheet along the length of the electrode assembly and away from the tab.

[0184] The preparation method of Comparative Example 3 is basically the same as that of Example 1, except that the single-sided coating density of the negative electrode slurry in the preparation of the negative electrode sheet is adjusted. The negative electrode slurry is prepared at a density of 155 mg / 1540.25 mm. 2 The single-sided coating surface density is double-sided coated on both sides of an 8μm thick copper foil.

[0185] The preparation method of Comparative Example 4 is basically the same as that of Example 1, except that the single-sided coating density of the negative electrode slurry in the preparation of the negative electrode sheet is adjusted. The negative electrode slurry is prepared at a density of 220 mg / 1540.25 mm. 2 The single-sided coating surface density is double-sided coated on both sides of an 8μm thick copper foil.

[0186] 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, rolling speed, roll gap, holding time, and number of rolling cycles in the compaction process, the compaction density of the negative electrode sheet obtained after cold pressing is 1.33 g / cm³. 3 .

[0187] 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, by adjusting the pressure, rolling speed, roll gap, holding time, and number of rolling cycles in the compaction process, the compaction density of the negative electrode sheet obtained after cold pressing is 1.80 g / cm³. 3 .

[0188] Performance testing 1. OI value test In this application, the OI value can be measured using an X-ray diffractometer (such as a Bruker D8 Discover). Refer to JISK0131-1996 and JB / T 4220-2011 to obtain the X-ray diffraction pattern of the negative electrode film. Based on OI value = I...004 / I 110 The OI value of the negative electrode film was calculated. 004 I is the integrated area of ​​the diffraction peaks of the crystalline carbon 004 plane in the negative electrode film. 110 This represents the integrated area of ​​the peak on the 110 crystal plane of crystalline carbon in the negative electrode film. In the X-ray diffraction analysis test of this application, a copper target can be used as the anode target, with CuK α rays as the radiation source, a wavelength of 1.5418 Å, a scanning 2θ angle range of 20°-80°, and a scanning rate of 4° / min.

[0189] 2. Battery Energy Density Test Method The battery cells prepared in each embodiment and comparative example were left to stand at 25°C for 2 hours to ensure the temperature of the battery cells remained at 25°C. The battery cells were then charged at 1 / 3C at 25°C to the charging cutoff voltage of 3.75V, and then continued to be charged at this charging cutoff voltage under constant voltage until the current reached 0.05C, at which point charging was stopped (where C represents the rated capacity of the battery cell). After the battery cells were left to stand at 25°C for 1 hour, they were discharged at 0.33C at 25°C to the discharge cutoff voltage of 2.0V, and the total discharge energy of the battery cells was recorded as E0.

[0190] The volume of a single battery cell is measured as V0, in liters (L).

[0191] The volumetric energy density of a battery cell = discharge energy of the battery cell E0 / volume of the battery cell V0, with the unit being Wh / L.

[0192] 3. Cyclic performance testing method At 25°C, the battery cells prepared in each embodiment and comparative example were charged at a constant current of 1C to 50% SOC, then charged at 0.87C to 80% SOC, and then charged at 0.33C to a cutoff voltage of 3.75V. Constant voltage charging was then continued at this cutoff voltage until the current reached 0.05C. Finally, constant current charging at 1C was performed to a discharge cutoff voltage of 2.0V. This constitutes one charge-discharge cycle. The discharge capacity of the battery cell at this point is recorded as the discharge capacity E1 of the battery's first cycle. This charging and discharging process was repeated 1000 times, and the discharge capacity of the battery cell at this point is recorded as E2. Cycle life @1000Cls = E2 / E1 × 100%.

[0193] 4. Discharge K-value test method After cycling, the battery cell was left to stand at 25°C for 2 hours, then charged at a constant current of 0.33C to 3.75V, and continued to be charged at a constant voltage until the charging current was less than 0.05C. After standing for 2 hours, the value was recorded as OCV1 in mV. After standing for 24 hours, the voltage was tested and recorded as OCV2 in mV. The K value is calculated as (OCV1-OCV2) / 24h in mV / h.

[0194] Battery cells for each embodiment and comparative example were prepared according to the above method. The specific parameters and performance characteristics are shown in Tables 1 and 2 below.

[0195] Table 1

[0196] Through comparison of the embodiments and comparative examples, it can be seen that the battery cell of this application includes an electrode assembly, an electrolyte, and a casing. The electrode assembly is housed in the casing, and the casing is made of a soft-pack material. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The positive and negative electrode are alternately stacked, and the separator is disposed between adjacent positive and negative electrode sheets. The negative electrode has chamfers on all four sides. The projection of the positive electrode along the electrode stacking direction completely falls within the projection of the adjacent negative electrode along the electrode stacking direction. The negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer, in its fully loaded state, has a single-sided coating surface density of 170 mg / 1540.25 mm². 2 - 200mg / 1540.25mm 2 The compacted density is 1.4 g / cm³. 3 -1.6cm 3 At the same time, it has a high energy density and a low post-cycle discharge K value, which means that the phenomenon of lithium plating during battery cycling is reduced.

[0197] By comparing Examples 1 and 6, it can be seen that both C-shaped and R-shaped chamfers reduce lithium plating. R-shaped chamfers are better for stress dispersion and result in a lower K value after cycling.

[0198] By comparing Examples 1, 7-9, and 10, it can be seen that when the radius of the chamfer R is 0.5%-2.5% of the width of the negative electrode sheet, and further 0.8%-2%, both the energy density of the battery and the suppression of lithium plating are taken into account.

[0199] Table 2

[0200] By comparing Examples 1-3, it can be seen that when the CB value of the battery cell is in the range of 1.05-1.15, and further in the range of 1.08-1.15, the phenomenon of lithium plating during cycling is reduced, the K value after cycling is lower, and it has higher cycle life and energy density.

[0201] By comparing Examples 1 and Examples 11-14, it can be seen that when the OI value of the graphite material is 1.7-5, and further 2.5-3.5, it is beneficial to improve the energy density and cycle performance of the battery.

[0202] By comparing Examples 1 and Examples 15-18, it can be seen that when the electrolyte 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.

[0203] By comparing Examples 1 and 19 and 20, it can be seen that when the length and width of the positive current collector decrease independently in the electrode stacking direction of the electrode assembly, 70°≤α1≤85°, 70°≤α2≤85°, and the length and width of the negative current collector decrease independently in the same order, 70°≤β1≤85°, 70°≤β2≤85°, the degree of lithium plating and the K value after cycling are further reduced.

[0204] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, It includes an electrode assembly, an electrolyte, and a housing, wherein the electrode assembly is housed within the housing, and the housing is made of a flexible material; The electrode assembly includes a positive electrode, a negative electrode, and a separator. The positive electrode and the negative electrode are stacked alternately, and the separator is disposed between adjacent positive electrode and negative electrode. The negative electrode sheet has chamfers on all four sides; the projection of the positive electrode sheet along the electrode stacking direction falls completely into the projection of the adjacent negative electrode sheet along the electrode stacking direction. The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, with a single-sided coating surface density of 170 mg / 1540.25 mm². 2 - 200mg / 1540.25mm 2 The ratio of the dimensional difference between any adjacent negative electrode and positive electrode in any direction of length or width to the dimensional difference of the negative electrode in that direction is 0.5%-1.5%.

2. The battery cell according to claim 1, characterized in that, The negative electrode film layer has a compaction density of 1.4 g / cm³ when fully expanded. 3 -1.6g / cm 3 .

3. The battery cell according to claim 1 or 2, characterized in that, In the fully discharged state, the thickness of the negative electrode film on one side is 70μm-90μm.

4. The battery cell according to any one of claims 1 to 3, characterized in that, In the fully discharged state, the thickness of the negative electrode film on one side is 75μm-90μm.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The chamfer includes an R-shaped chamfer.

6. The battery cell according to claim 5, characterized in that, 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 according to claim 5 or 6, characterized in that, The radius of the R-shaped chamfer is 0.8%-2% of the width of the negative electrode current collector.

8. The battery cell according to any one of claims 1 to 4, characterized in that, The chamfer includes a C-shaped chamfer.

9. The battery cell according to claim 8, characterized in that, The size of the C-shaped chamfer is 0.5%-1.5% of the width of the negative electrode current collector.

10. The battery cell according to any one of claims 1 to 9, characterized in that, The CB value of the battery cell ranges from 1.05 to 1.15, where the CB value represents the ratio of the capacity of the negative electrode to the capacity of the positive electrode per unit area.

11. The battery cell according to any one of claims 1 to 10, characterized in that, The CB value of the battery cell ranges from 1.08 to 1.15, where the CB value represents the ratio of the capacity of the negative electrode to the capacity of the positive electrode per unit area.

12. The battery cell according to any one of claims 1 to 11, characterized in that, The negative electrode film layer includes a negative electrode active material, which includes graphite material. The OI value of the graphite material is 1.7-5, where OI value = I. 004 / I 110 I 004 I represents the integrated area of ​​the diffraction peak of the 004 crystal plane in X-ray diffraction analysis. 110 The integral area of ​​the diffraction peak on the 110 crystal plane.

13. The battery cell according to any one of claims 1 to 12, characterized in that, The negative electrode film layer includes a negative electrode active material, which includes graphite material. The OI value of the graphite material is 2.5-3.5, where OI value = I. 004 / I 110 I 004 I represents the integrated area of ​​the diffraction peak of the 004 crystal plane in X-ray diffraction analysis. 110 The integral area of ​​the diffraction peak on the 110 crystal plane.

14. The battery cell according to any one of claims 1 to 13, characterized in that, The electrolyte injection coefficient of the battery cell is 2.5g / Ah-4g / Ah.

15. The battery cell according to any one of claims 1 to 14, characterized in that, The electrolyte injection coefficient of the battery cell is 2.7 g / Ah-3.2 g / Ah.

16. The battery cell according to any one of claims 1 to 15, characterized in that, Along the electrode stacking direction in the electrode assembly, the dimensions of the negative electrode current collector decrease independently by ΔL1 in either the length or width direction, wherein 15μm≤ΔL1≤120μm.

17. The battery cell according to claim 15, characterized in that, The positive electrode includes a positive current collector and a positive film layer disposed on at least one side of the positive current collector. Along the electrode stacking direction in the electrode assembly, the size of the positive current collector decreases independently by ΔL2 in either the length or width direction, wherein 15μm≤ΔL2≤120μm.

18. The battery cell according to any one of claims 1 to 17, characterized in that, The projection of the battery cell onto the first projection plane is a first projection trapezoid, and the first projection plane refers to the plane defined by the width direction and the stacking direction of the electrode assembly.

19. The battery cell according to claim 18, characterized in that, The first projected trapezoid is an isosceles trapezoid.

20. The battery cell according to any one of claims 1 to 19, characterized in that, The projection of the battery cell onto the second projection plane is a second projection trapezoid; the second projection plane refers to the plane defined by the length direction and the stacking direction of the electrode assembly.

21. The battery cell according to claim 20, characterized in that, The second projected trapezoid is an isosceles trapezoid.

22. The battery cell according to claim 18 or 19, characterized in that, The angles formed by the waist of the first projected trapezoid and the longer base of the first projected trapezoid are α1 and α2, respectively, where 70°≤α1≤85° and 75°≤α2≤85°.

23. The battery cell according to claim 22, characterized in that, α1=α2。 24. The battery cell according to claim 20 or 21, characterized in that, The angles formed by the waist of the second projected trapezoid and the longer base of the second projected trapezoid are β1 and β2, respectively, where 70°≤β1≤85° and 70°≤β2≤85°.

25. The battery cell according to claim 24, characterized in that, β1=β2。 26. The battery cell according to any one of claims 1 to 25, characterized in that, The positive electrode plate is also chamfered around all four sides.

27. The battery cell according to any one of claims 1 to 26, characterized in that, The thickness of the negative electrode current collector is 6μm-10μm.

28. The battery cell according to any one of claims 1 to 27, characterized in that, The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, wherein the thickness of the positive current collector is 12μm-15μm.

29. The battery cell according to any one of claims 1 to 28, characterized in that, The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, wherein the length of the positive current collector is 520mm-570mm.

30. The battery cell according to any one of claims 1 to 29, characterized in that, The length of the negative electrode current collector is 520mm-570mm.

31. The battery cell according to any one of claims 1 to 30, characterized in that, The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, wherein the width of the positive current collector is 100mm-130mm.

32. The battery cell according to any one of claims 1 to 31, characterized in that, The width of the negative electrode current collector is 100mm-130mm.

33. A battery device, characterized in that, The battery device comprises the battery cell according to any one of claims 1 to 32.

34. The battery device according to claim 33, characterized in that, The battery device includes at least one of a battery module, a battery pack, and an energy storage device.

35. An electrical appliance, characterized in that, Includes the battery cell according to any one of claims 1 to 32 or the battery device according to claim 33.

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