Battery cell, battery device, power consuming device, and energy storage device

Abstract

The application provides a battery monomer, a battery device, a power consumption device and an energy storage device. The battery monomer comprises an electrode assembly 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 a positive electrode sheet and a negative electrode sheet, the positive electrode sheet and the negative electrode sheet are alternately and laminatedly arranged; the negative electrode current collector comprises a negative electrode current collecting part, and a chamfer is arranged around the negative electrode current collecting part; the positive electrode current collector comprises a positive electrode current collecting part and a positive electrode tab; the positive electrode film layer comprises a positive electrode active material layer and first and second insulating layers, the first insulating layer is arranged on one side of the positive electrode active material layer close to the positive electrode tab, the second insulating layer is arranged on the other side of the positive electrode active material layer away from the positive electrode tab, and the single-sided surface density of the positive electrode active material layer is greater than or equal to 320 mg / 1540.25 mm 2 The battery monomer provided by the application has good cycle performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery cell, battery device, power consumption device, and energy storage device. Background Technology

[0002] 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, military equipment, and aerospace.

[0003] As the market demands longer driving ranges and longer battery lifespans, higher requirements are being placed on battery manufacturing yield and cycle performance. However, current technologies struggle to simultaneously improve these performance characteristics, making it crucial to address this critical technical challenge. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell that balances processing yield and good cycle stability.

[0005] The first aspect of this application provides a battery cell, including an electrode assembly and a housing. The electrode assembly is housed within the housing, and the housing is made of a soft-pack material. The electrode assembly includes a positive electrode and a negative electrode, which are alternately stacked. The negative electrode includes a negative current collector, which includes a negative current collection portion with chamfered edges around its perimeter. The positive electrode includes a positive current collector, which includes a positive current collection portion and a positive electrode tab disposed on one side of the positive current collection portion extending along a first direction perpendicular to the battery cell. In the thickness direction, the positive electrode sheet also includes a positive electrode film layer disposed on at least one side of the positive current collector along the thickness direction of the battery cell. The positive electrode film layer includes a positive electrode active material layer and a first insulating layer and a second insulating layer disposed on opposite sides of the positive electrode active material layer in a first direction. The first insulating layer is disposed on the side of the positive electrode active material layer closer to the positive electrode tab, and the second insulating layer is disposed on the side of the positive electrode active material layer away from the positive electrode tab. When the battery cell is fully discharged, the single-sided density of the positive electrode active material layer is greater than or equal to 320 mg / 1540.25 mm². 2 .

[0006] In the prior art, the insulating layer is generally only set on the tab side to reduce the risk during tab processing. In the embodiments of this application, an insulating layer is also set on the side of the positive electrode active material layer away from the positive electrode tab to reduce the impact of stress concentration at the corner of the electrode on the spacing between the positive electrode active material layers. This allows the risk of lithium plating in the battery to be reduced without setting a chamfer on the positive electrode, so that the battery cell can achieve both processing yield and good cycle stability.

[0007] The presence of a positive electrode active material layer within the aforementioned range indicates that the positive electrode sheet has a high active material loading, which helps to improve the volumetric energy density of the battery cell. However, the applicant has found that if the positive electrode sheet with a high active material loading is chamfered to reduce stress concentration, the positive electrode active material in the chamfered area will loosen or even fall off under external force, thereby further increasing the probability of leakage of current collectors from the positive electrode sheet and affecting the cycle performance of the battery. Therefore, in the embodiments of this application, the positive electrode sheet is not chamfered, and the positive electrode film layer includes a positive electrode active material layer and an insulating layer disposed on opposite sides of the positive electrode active material layer along the first direction. This is particularly suitable for battery cells with a high active material loading, and can balance the high volumetric energy density, processing yield, and good cycle stability of the battery cell.

[0008] In any embodiment, the dimension D1 of the first insulating layer in the first direction is 1mm-2.5mm.

[0009] The first insulating layer has a dimension D1 in the first direction within the range of 1mm-2.5mm. On the one hand, this helps to effectively reduce the risk during electrode processing and improve the battery processing yield; on the other hand, the first insulating layer helps to share the stress at the corner, thereby improving the cycle stability of the battery cell.

[0010] In any embodiment, the dimension D1 of the first insulating layer in the first direction is 1mm-2mm.

[0011] A D1 value in the range of 1mm-2mm helps to further improve the processing yield and cycle performance of battery cells; at the same time, it helps to reduce the space occupied by the first insulating layer on the positive electrode active material layer and improve the volumetric energy density of the battery cells.

[0012] In any embodiment, the dimension D2 of the second insulating layer in the first direction is 1mm-4.5mm.

[0013] The second insulating layer has a dimension D2 in the first direction ranging from 1mm to 4.5mm, which helps to effectively share the stress of the casing on the positive electrode current collector, alleviate the abnormal spacing caused by stress concentration at the corners and edges of the positive electrode sheet, and thus improve the cycle performance of the battery cell.

[0014] In any embodiment, the dimension D2 of the second insulating layer in the first direction is 2mm-3mm.

[0015] A D2 range of 2mm-3mm helps to further improve the cycle performance of battery cells; at the same time, it helps to reduce the space occupied by the second insulating layer on the positive electrode active material layer, thereby increasing the volumetric energy density of battery cells.

[0016] In any embodiment, the materials of the first insulating layer and the second insulating layer each independently include one or more of alumina, zirconium oxide, and titanium oxide.

[0017] The materials of the first and second insulating layers include the aforementioned materials. On the one hand, they help reduce stress concentration at right-angle corners and edges of the electrode assembly; on the other hand, the aforementioned materials are insulating materials, which help reduce the probability of burrs generated after the negative electrode sheet is chamfered and overlapping with the positive electrode sheet, thereby improving the battery cycle performance and safety performance.

[0018] In any embodiment, the materials of both the first insulating layer and the second insulating layer include aluminum oxide.

[0019] In any implementation, the chamfer includes either an R-type chamfer or a C-type chamfer.

[0020] 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.

[0021] In any implementation, the chamfer is an R-shaped chamfer.

[0022] In this embodiment, the chamfer of the negative electrode sheet includes an R-shaped chamfer, which helps to further reduce stress concentration at right-angle corners and edges of the negative electrode sheet, reduce the probability of lithium plating on the negative electrode sheet, and thus further improve the cycle performance of the battery cell.

[0023] In any embodiment, the negative electrode sheet further includes a negative electrode film layer disposed on at least one side of the negative electrode current collector in the thickness direction of the battery cell, wherein the size difference OH1 between the negative electrode film layer and the positive electrode active material layer in the first direction satisfies 2mm≤OH1≤6mm.

[0024] The size difference OH1 between the negative electrode film layer and the positive electrode active material layer in the first direction helps to provide a suitable space at the positive electrode sheet for setting the first insulating layer and the second insulating layer, thereby helping to further improve the cycle performance of the battery cell. At the same time, the size of the negative electrode film layer is larger than that of the positive electrode film layer, which helps to provide a sufficient number of lithium insertion sites on the negative electrode sheet, reduce the probability of lithium plating on the negative electrode sheet, and further improve the cycle performance of the battery cell. In addition, if OH1 is too large, it will affect the loading of the positive electrode active material. In the embodiments of this application, OH1 is within the above range, which helps to improve the cycle performance of the battery cell while taking into account the energy density.

[0025] In any embodiment, the negative electrode sheet further includes a negative electrode film layer disposed on at least one side of the negative electrode current collector in the thickness direction of the battery cell, wherein the size difference OH1 between the negative electrode film layer and the positive electrode active material layer in the first direction satisfies 2mm≤OH1≤5mm.

[0026] In the embodiments of this application, OH1 is within the above-mentioned range, which helps to further improve the cycle performance of the battery while taking into account the energy density.

[0027] In any embodiment, the size difference OH1 between the negative electrode film layer and the positive electrode active material layer satisfies OH1-(D1+D2)=0mm, where D1 is the size of the first insulating layer in the first direction and D2 is the size of the second insulating layer in the first direction.

[0028] In existing technologies, a common approach is to chamfer the positive electrode to reduce stress concentration at the corners of the positive electrode sheet. However, this approach results in the loss of some positive electrode active material, thereby reducing the volumetric energy density of the battery. In the embodiments of this application, the size difference OH1 between the negative electrode film layer and the positive electrode active material layer satisfies OH1-(D1+D2)=0mm, meaning that the sizes of the negative electrode film layer and the positive electrode film layer are equal. This size difference is used to set the first insulating layer and the second insulating layer. On one hand, this structure helps improve the space utilization within the battery assembly and increases the energy density of the individual battery cells. On the other hand, the negative electrode current collector has a chamfer, while the positive electrode current collector does not, and the sizes of the negative electrode film layer and the positive electrode film layer are equal. This allows the first and second insulating layers in the positive electrode film layer to effectively share the stress generated by the shell shrinkage, reducing stress concentration at the edges of the negative electrode sheet, and further contributing to improving the cycle performance of the individual battery cells.

[0029] In any embodiment, the size difference OH2 between the negative electrode film layer and the positive electrode active material layer in the second direction satisfies 1mm≤OH2≤3mm, wherein any two of the first direction, the second direction and the thickness direction of the battery cell are perpendicular to each other.

[0030] In this embodiment, the size difference OH2 between the negative electrode film layer and the positive electrode active material layer in the second direction is within the above-mentioned range, which helps to provide sufficient lithium insertion sites on the negative electrode sheet, thereby helping to reduce the probability of lithium plating on the negative electrode sheet, and thus helping to improve the cycle performance of the battery cell.

[0031] In any embodiment, when the battery cell is fully discharged, the lateral surface density of the positive electrode active material layer is 320 mg / 1540.25 mm². 2 -400mg / 1540.25mm 2 .

[0032] In any embodiment, the compaction density of the positive electrode active material layer of the battery cell in a fully discharged state is greater than or equal to 2.3 g / cm³. 3 .

[0033] High compaction density helps increase the loading of positive electrode active material on the positive electrode sheet; low compaction density helps increase the porosity of the film layer and improve liquid retention performance. In the embodiments of this application, when the battery cell is in a fully discharged state, the compaction density of the positive electrode film layer is within the above-mentioned range, which helps to balance a high loading of active material with a suitable pore structure, improve the liquid retention rate of the electrode sheet, reduce polarization resistance, and thus improve the cycle performance and capacity utilization of the battery.

[0034] In any embodiment, the compaction density of the positive electrode film layer in the fully discharged state of the battery cell is 2.3 g / cm³. 3 -2.6g / cm 3 .

[0035] In any embodiment, the positive electrode active material layer includes a positive electrode active material, which includes lithium-containing transition metal oxide particles and lithium-containing transition metal phosphate particles.

[0036] Lithium-containing transition metal oxides have high specific capacity. In this embodiment, including lithium-containing transition metal oxides as the positive electrode active material helps to improve the energy density of the battery cell. Lithium-containing transition metal phosphates have good cycle performance. In this embodiment, including lithium-containing transition metal phosphates as the positive electrode active material helps to improve the cycle performance of the battery cell.

[0037] In any embodiment, the mass ratio of lithium transition metal oxide particles to lithium transition metal phosphate particles is 5:5-9:1.

[0038] In the embodiments of this application, the mass ratio of lithium transition metal oxide particles to lithium transition metal phosphate particles is within the above-mentioned range, which helps to improve the cycle performance of the battery cell while taking into account the energy density.

[0039] In any embodiment, the mass ratio of lithium-containing transition metal oxide particles to lithium-containing transition metal phosphate particles is 6:4-8:2.

[0040] In the embodiments of this application, the mass ratio of lithium transition metal oxide particles to lithium transition metal phosphate particles is within the above-mentioned range, which helps to further improve the cycle performance of the battery cell while taking into account the energy density.

[0041] In any embodiment, the lithium-containing transition metal oxide particles comprise components represented by the following general formula:

[0042] Li a1 Ni x1 Coy1 M1 z1 M2 w1 O 2-b1 Formula I,

[0043] Wherein, M1 includes one or more of Mn and Al, M2 includes one or more of Zr, B, Mg, Ti, W, Mo, Nb, Ta, Sr, Sb, and K, 0.8≤a1≤1.2, 0≤x1≤1, 0≤y1≤1, 0≤z1≤1, 0≤w1≤0.1, and -0.1≤b1≤0.1.

[0044] When the positive electrode active material layer includes the above-mentioned lithium-containing transition metal oxides, the specific capacity of the positive electrode active material can be further improved, thereby further improving the energy density of the battery cell.

[0045] In any embodiment, the lithium transition metal phosphate particles comprise components represented by the following general formula:

[0046] Li x A y Me a M b P 1-c X c Y z Formula II,

[0047] Wherein, 0.1≤x≤1.3, 0≤y≤1.3, and 0.8≤x+y≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; Y includes one or more of O and F.

[0048] Lithium-containing transition metal phosphates, including the components shown in the above general formula, have good thermal stability and cycle stability, which helps to improve the safety and cycle performance of batteries.

[0049] In any embodiment, the lithium-containing transition metal phosphate particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium vanadium fluoride phosphate, lithium manganese iron phosphate, lithium fluoride iron phosphate, lithium manganese iron phosphate, and their modified materials.

[0050] In any embodiment, the lithium-containing transition metal phosphate particles include one or more of lithium manganese iron phosphate and its modified materials.

[0051] Compared to other lithium-containing transition metal phosphates, lithium manganese iron phosphate has a higher voltage plateau and a smaller voltage difference with lithium-containing transition metal oxides, which is beneficial for the specific capacity of lithium-containing transition metal phosphates and thus further improves the volumetric energy density of battery cells.

[0052] In any embodiment, the negative electrode sheet further includes a negative electrode film layer disposed on at least one side of the negative electrode current collector in the thickness direction of the battery cell, wherein the density of the negative electrode film layer on one side is greater than or equal to 160 mg / 1540.25 mm² when the battery cell is fully discharged. 2 .

[0053] The fact that the negative electrode active material layer is within the above range indicates that the negative electrode sheet has a high active material loading, which helps to improve the volumetric energy density of the battery cell.

[0054] In any embodiment, the negative electrode sheet further includes a negative electrode film layer disposed on at least one side of the negative electrode current collector in the thickness direction of the battery cell, wherein the one-sided density of the negative electrode film layer is 180 mg / 1540.25 mm² when the battery cell is fully discharged. 2 -200mg / 1540.25mm 2 .

[0055] In any embodiment, the compaction density of the negative electrode film layer in the fully discharged state of the battery cell is greater than or equal to 1.4 g / cm³. 3 .

[0056] In any embodiment, the compaction density of the negative electrode film layer in the fully discharged state of the battery cell is 1.4 g / cm³. 3 -1.6g / cm 3 .

[0057] High compaction density helps increase the loading of negative electrode active material on the negative electrode sheet; while low compaction density helps increase the porosity of the film layer and improve liquid retention performance. In the embodiments of this application, when the battery cell is in a fully discharged state, the compaction density of the negative electrode film layer is within the above-mentioned range, which helps to balance a high loading of active material with a suitable pore structure, improve the liquid retention rate of the electrode sheet, reduce polarization resistance, and thus improve the cycle performance and capacity utilization of the battery.

[0058] In any embodiment, the negative electrode film layer includes a negative electrode active material, which includes graphite.

[0059] In any embodiment, the negative electrode active material includes one or more of natural flake graphite, artificial graphite, and microcrystalline graphite.

[0060] In any embodiment, the orientation degree (OI) of the negative electrode active material is 1.3-5.5, where OI value = I004 / 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.

[0061] A low OI value indicates poor orientation and high internal disorder in the material, affecting its structural stability. Conversely, a high OI value indicates highly ordered crystal arrangement, reduced porosity, and reduced liquid retention capacity, thus increasing polarization resistance. In the embodiments of this application, the OI value of the negative electrode active material is within the aforementioned range, which helps to balance structural stability and liquid retention capacity, thereby contributing to improved cycle performance of the battery cell.

[0062] In any embodiment, the orientation degree (OI) value of the negative electrode active material is 2.5-4.

[0063] In this embodiment, the OI value of the negative electrode active material is within the above range, which helps to further improve the structural stability and liquid retention capacity of the negative electrode active material and improve the cycle performance of the battery cell.

[0064] In any embodiment, the volume particle size distribution D of the negative electrode active material V 50 is 16μm-22μm.

[0065] In this embodiment of the application, the D of the negative electrode active material V Within the above range, 50 helps to reduce the polarization impedance of the battery and further improve the cycle performance of the battery.

[0066] A second aspect of this application provides a battery device, including the battery cell provided in the first aspect of this application.

[0067] A third aspect of this application provides an electrical device, which includes the battery device provided in the second aspect, the battery device being used to provide electrical energy.

[0068] The fourth aspect of this application provides an energy storage device, which includes the battery device provided in the second aspect, the battery device being used to store electrical energy. Attached Figure Description

[0069] 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.

[0070] Figure 1 This is a schematic diagram of the positive electrode sheet in one embodiment of this application;

[0071] Figure 2 This is a schematic diagram of the negative electrode sheet in one embodiment of this application;

[0072] Figure 3 This is a schematic diagram of an electrical device provided in some embodiments of this application.

[0073] The accompanying drawings are not necessarily drawn to scale.

[0074] Explanation of reference numerals in the attached figures:

[0075] 1 Positive electrode sheet; 11 Positive electrode film layer; 111 Positive electrode active material layer; 112 First insulating layer; 113 Second insulating layer; 12 Positive electrode current collector; 121 Positive electrode current collector; 122 Positive electrode tab; 21 Negative electrode film layer; 221 Negative electrode current collector; X First direction; Y Second direction; Z Thickness direction of the battery cell. Detailed Implementation

[0076] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell, battery device, power consumption device, and energy storage 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 the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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 mention that the method may also include step (c) indicates 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.

[0081] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0082] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0083] In this application, the terms "multiple" or "various" refer to two or more kinds of things.

[0084] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0085] 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.

[0086] 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.

[0087] A single battery cell is the smallest unit that makes up a battery, and it can independently perform the functions of charging and discharging.

[0088] When there are multiple battery cells, they are connected in series, parallel, or mixed via a busbar. In some embodiments, the battery can be a battery module; when there are multiple battery cells, they 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 within 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 part of the vehicle's floor, or a portion of the housing can be at least part of the vehicle's crossbeams and longitudinal beams.

[0089] In some embodiments, the battery can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0090] In some embodiments, 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 arbitrary manner. Furthermore, the multiple battery cells can be secured using fasteners.

[0091] Optionally, the battery module may also include a housing with a receiving space in which multiple battery cells are housed.

[0092] 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.

[0093] The battery pack may include a housing and multiple battery modules disposed within the housing. The housing includes 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.

[0094] The battery provided in this application embodiment may include a lithium-ion battery.

[0095] A single battery cell includes an electrode assembly. The electrode assembly typically includes a positive electrode and a negative electrode. The negative electrode is the electrode that undergoes the reaction of absorbing or lithiating lithium ions during battery charging and releasing or delithiating lithium during battery discharging. The positive electrode is the electrode that undergoes the reaction of releasing or delithiating lithium ions during battery charging and absorbing or lithiating lithium during battery discharging.

[0096] With the development of the battery industry, the requirements for battery cells are constantly increasing, and the energy density standards for energy storage batteries and power batteries are rising year by year. Current technologies typically employ the following approaches to improve the energy density of battery cells: using stacked electrode assemblies to increase the loading of active materials in the battery cell, which can improve space utilization by 5%-8% compared to the traditional wound structure; in addition, using soft-pack materials for the battery cell casing, which are lighter and help improve the volumetric energy density of the battery cell. However, research shows that soft-pack battery cells require vacuum sealing. During the battery sealing process, the casing material is prone to stress concentration at the corners of the electrodes, making the spacing between electrodes at the corners larger than at other locations. This difference in lithium-ion transport paths easily leads to lithium plating at the electrode corners, causing a sharp drop in battery cycle performance. Therefore, current technologies often incorporate chamfering designs around both the positive and negative electrode plates. However, with the increasing requirements for battery energy density, higher demands are placed on the compactness and areal density of the battery electrodes. Chamfering around the positive electrode plate is more likely to cause burr problems, reducing product yield. Therefore, how to improve the energy density of individual battery cells while taking into account cycle performance and processing yield has become an urgent technical problem to be solved.

[0097] To address the aforementioned problems, a first aspect of this application provides a battery cell, including an electrode assembly and a housing. The electrode assembly is housed within the housing, and the housing is made of a soft-pack material. The electrode assembly includes a positive electrode and a negative electrode, which are alternately stacked. The negative electrode includes a negative current collector, such as... Figure 2 As shown, the negative electrode current collector includes a negative electrode current collector section 21, and the negative electrode current collector section 21 has chamfers around its perimeter; as Figure 1As shown, the positive electrode 1 includes a positive current collector 12, which includes a positive current collector portion 121 and a positive electrode tab 122 disposed on one side of the positive current collector portion 121 extending along a first direction X, the first direction X being perpendicular to the thickness direction Z of the battery cell. The positive electrode 1 also includes a positive electrode film layer 11 disposed on at least one side of the positive current collector portion 121 along the thickness direction Z of the battery cell. The positive electrode film layer 11 includes a positive active material layer 111 and a first insulating layer 112 and a second insulating layer 113 disposed on opposite sides of the positive active material layer 111 in the first direction X. The first insulating layer 112 is disposed on the side of the positive active material layer 111 closer to the positive electrode tab 122, and the second insulating layer 113 is disposed on the side of the positive active material layer 111 away from the positive electrode tab 122. When the battery cell is fully discharged, the unilateral density of the positive active material layer is greater than or equal to 320 mg / 1540.25 mm². 2 .

[0098] In the prior art, the insulating layer is generally only set on the tab side to reduce the risk during tab processing. In the embodiments of this application, an insulating layer is also set on the side of the positive electrode active material layer away from the positive electrode tab to reduce the impact of stress concentration at the corner of the electrode on the spacing between the positive electrode active material layers. This allows the risk of lithium plating in the battery to be reduced without setting a chamfer on the positive electrode, so that the battery cell can achieve both processing yield and good cycle stability.

[0099] It is worth noting that the first direction is perpendicular to the thickness direction of the battery cell. The first direction can be the length direction or the width direction of the battery cell, and the first direction is the direction in which the tab extends. Figure 1 This is merely an example and does not imply that the first direction is necessarily the longer side.

[0100] The presence of a positive electrode active material layer within the aforementioned range indicates that the positive electrode sheet has a high active material loading, which helps to improve the volumetric energy density of the battery cell. However, the applicant has found that if the positive electrode sheet with a high active material loading is chamfered to reduce stress concentration, the positive electrode active material in the chamfered area will loosen or even fall off under external force, thereby further increasing the probability of leakage of current collectors from the positive electrode sheet and affecting the cycle performance of the battery. Therefore, in the embodiments of this application, the positive electrode sheet is not chamfered, and the positive electrode film layer includes a positive electrode active material layer and an insulating layer disposed on opposite sides of the positive electrode active material layer along the first direction. This is particularly suitable for battery cells with a high active material loading, and can balance the high volumetric energy density, processing yield, and good cycle stability of the battery cell.

[0101] 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 2.5V and left to stand for 30 minutes. Finally, it is discharged at a constant voltage of 2.5V to 0.05C.

[0102] In this application, the areal density of the positive electrode active material layer on one side has a meaning known in the art and can be tested using methods known in the art. As an example, take a positive electrode sheet that has been coated on one side and cold-pressed (if it is a double-sided coated positive electrode sheet, the positive electrode film layer on one side can be wiped off first), cut it into small circular pieces with an area of ​​S1, weigh them, and record their weight as M1. Then wipe off the positive electrode film layer of the weighed positive electrode sheet, weigh the current collector, and record its weight as M0. The areal density of the positive electrode film layer = (M1 - M0) / S1. To ensure the accuracy of the test results, multiple sets (e.g., 10 sets) of samples can be tested, and the average value can be calculated as the test result.

[0103] In some embodiments, the unilateral surface density of the positive electrode active material layer in a fully discharged state of the battery cell can be 320 mg / 1540.25 mm². 2 320mg / 1540.25mm 2 325mg / 1540.25mm 2 330mg / 1540.25mm 2 335mg / 1540.25mm 2 340mg / 1540.25mm 2 345mg / 1540.25mm 2 350mg / 1540.25mm 2 355mg / 1540.25mm 2 360mg / 1540.25mm 2 365mg / 1540.25mm 2 370mg / 1540.25mm 2 375mg / 1540.25mm 2 380mg / 1540.25mm 2 385mg / 1540.25mm 2 390mg / 1540.25mm 2 395mg / 1540.25mm 2 400mg / 1540.25mm 2 405mg / 1540.25mm 2 410mg / 1540.25mm 2 415mg / 1540.25mm2 420mg / 1540.25mm 2 Or the range of values ​​between any two.

[0104] In some implementations, such as Figure 1 As shown, the dimension D1 of the first insulating layer 112 in the first direction X is 1mm-2.5mm.

[0105] In this application, the dimension D1 of the first insulating layer in the first direction refers to the dimension of the first insulating layer on the surface of the positive current collector in the first direction, i.e. Figure 1 D1 in the figure can be measured using methods and instruments known in the art. As an example, it can be measured using a micrometer (e.g., a Mitutoyo 293-100 with an accuracy of 0.1 μm).

[0106] In some embodiments, the dimension D1 of the first insulating layer in the first direction can be 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, or any value between the two.

[0107] The first insulating layer has a dimension D1 in the first direction within the range of 1mm-2.5mm. On the one hand, this helps to effectively reduce the risk during electrode processing and improve the battery processing yield; on the other hand, the first insulating layer helps to share the stress at the corner, thereby improving the cycle stability of the battery cell.

[0108] In some embodiments, the dimension D1 of the first insulating layer in the first direction is 1mm-2mm.

[0109] A D1 value in the range of 1mm-2mm helps to further improve the processing yield and cycle performance of battery cells; at the same time, it helps to reduce the space occupied by the first insulating layer on the positive electrode active material layer and improve the volumetric energy density of the battery cells.

[0110] In some implementations, such as Figure 1 As shown, the second insulating layer 113 has a dimension D2 of 1mm-4.5mm in the first direction X.

[0111] In this application, the dimension D2 of the second insulating layer in the first direction can be measured using methods and instruments known in the art. As an example, it can be measured using a micrometer (e.g., a Mitutoyo 293-100 model with an accuracy of 0.1 μm).

[0112] In some embodiments, the dimension D2 of the second insulating layer in the first direction can be selected as 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm, 4.0 mm, 4.1 mm, 4.2 mm, 4.3 mm, 4.4 mm, 4.5 mm, or any value range between the two.

[0113] The second insulating layer has a dimension D2 in the first direction ranging from 1mm to 4.5mm, which helps to effectively share the stress of the casing on the positive electrode current collector, alleviate the abnormal spacing caused by stress concentration at the corners and edges of the positive electrode sheet, and thus improve the cycle performance of the battery cell.

[0114] In some embodiments, the dimension D2 of the second insulating layer in the first direction is 2mm-3mm.

[0115] A D2 range of 2mm-3mm helps to further improve the cycle performance of battery cells; at the same time, it helps to reduce the space occupied by the second insulating layer on the positive electrode active material layer, thereby increasing the volumetric energy density of battery cells.

[0116] In some embodiments, the materials of the first insulating layer and the second insulating layer each independently include one or more of alumina, zirconium oxide, and titanium oxide.

[0117] The materials of the first and second insulating layers include the aforementioned materials. On the one hand, they help reduce stress concentration at right-angle corners and edges of the electrode assembly; on the other hand, the aforementioned materials are insulating materials, which help reduce the probability of burrs generated after the negative electrode sheet is chamfered and overlapping with the positive electrode sheet, thereby improving the battery cycle performance and safety performance.

[0118] In some embodiments, both the first insulating layer and the second insulating layer are made of aluminum oxide.

[0119] In some implementations, the chamfer includes either an R-shaped chamfer or a C-shaped chamfer.

[0120] R-shaped chamfers are rounded chamfers, such as... Figure 2As shown, a smooth transition can distribute stress evenly and reduce stress concentration points, but it requires the use of a fillet tool with a specific radius, which increases tool cost. Changing tools to adapt to fillets with different radii may increase production costs and time. A C-type chamfer is a 45° bevel angle where two adjacent faces are removed by the same dimension. It can be completed using a standard bevel tool or by adjusting the tool's feed angle. The tool is more versatile and the cost is relatively low. However, it is not as effective as the R-type chamfer in reducing stress concentration.

[0121] In this embodiment, the chamfer of the negative electrode sheet includes an R-shaped chamfer or a C-shaped chamfer, which helps to reduce stress concentration at right-angle corners and edges of the negative electrode sheet, reduce the probability of lithium plating on the negative electrode sheet, and thus help to improve the cycle performance of the battery cell.

[0122] In some implementations, the chamfer is an R-shaped chamfer.

[0123] In this embodiment, the chamfer of the negative electrode sheet includes an R-shaped chamfer, which helps to further reduce stress concentration at right-angle corners and edges of the negative electrode sheet, reduce the probability of lithium plating on the negative electrode sheet, and thus further improve the cycle performance of the battery cell.

[0124] In some embodiments, the negative electrode sheet further includes a negative electrode film layer disposed on at least one side of the negative electrode current collector in the thickness direction of the battery cell, wherein the size difference OH1 between the negative electrode film layer and the positive electrode active material layer in the first direction satisfies 2mm≤OH1≤6mm.

[0125] In this application, the size difference OH1 between the negative electrode film layer and the positive electrode active material layer in the first direction can be measured using methods and instruments known in the art. As an example, a micrometer can be used to measure the dimensions of the negative electrode film layer and the positive electrode active material layer in the first direction, and the difference between the measured dimensions of the negative electrode film layer and the positive electrode active material layer is OH1.

[0126] In some embodiments, the negative electrode sheet further includes a negative electrode film layer disposed on at least one side of the negative electrode current collector in the thickness direction of the battery cell. The size difference OH1 between the negative electrode film layer and the positive electrode active material layer in the first direction can be 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3.0mm, 3.1mm, 3.2mm, 3.3mm, or 3.4mm. 3.5mm, 3.6mm, 3.7mm, 3.8mm, 3.9mm, 4.0mm, 4.1mm, 4.2mm, 4.3mm, 4.4mm, 4.5mm, 4.6mm, 4.7mm, 4.8mm, 4.9mm, 5.0mm, 5.1mm, 5.2mm, 5.3mm, 5.4mm, 5.5mm, 5.6mm, 5.7mm, 5.8mm, 5.9mm, 6mm, or any range of two.

[0127] The size difference OH1 between the negative electrode film layer and the positive electrode active material layer in the first direction helps to provide a suitable space at the positive electrode sheet for setting the first insulating layer and the second insulating layer, thereby helping to further improve the cycle performance of the battery cell. At the same time, the size of the negative electrode film layer is larger than that of the positive electrode film layer, which helps to provide a sufficient number of lithium insertion sites on the negative electrode sheet, reduce the probability of lithium plating on the negative electrode sheet, and further improve the cycle performance of the battery cell. In addition, if OH1 is too large, it will affect the loading of the positive electrode active material. In the embodiments of this application, OH1 is within the above range, which helps to improve the cycle performance of the battery cell while taking into account the energy density.

[0128] In some embodiments, the negative electrode sheet further includes a negative electrode film layer disposed on at least one side of the negative electrode current collector in the thickness direction of the battery cell, wherein the size difference OH1 between the negative electrode film layer and the positive electrode active material layer in the first direction satisfies 2mm≤OH1≤5mm.

[0129] In the embodiments of this application, OH1 is within the above-mentioned range, which helps to further improve the cycle performance of the battery while taking into account the energy density.

[0130] In some embodiments, the size difference OH1 between the negative electrode film layer and the positive electrode active material layer satisfies OH1-(D1+D2)=0mm.

[0131] In existing technologies, a common approach is to chamfer the positive electrode to reduce stress concentration at the corners of the positive electrode sheet. However, this approach results in the loss of some positive electrode active material, thereby reducing the volumetric energy density of the battery. In the embodiments of this application, the size difference OH1 between the negative electrode film layer and the positive electrode active material layer satisfies OH1-(D1+D2)=0mm, meaning that the sizes of the negative electrode film layer and the positive electrode film layer are equal. This size difference is used to set the first insulating layer and the second insulating layer. On one hand, this structure helps improve the space utilization within the battery assembly and increases the energy density of the individual battery cells. On the other hand, the negative electrode current collector has a chamfer, while the positive electrode current collector does not, and the sizes of the negative electrode film layer and the positive electrode film layer are equal. This allows the first and second insulating layers in the positive electrode film layer to effectively share the stress generated by the shell shrinkage, reducing stress concentration at the edges of the negative electrode sheet, and further contributing to improving the cycle performance of the individual battery cells.

[0132] In some embodiments, the size difference OH2 between the negative electrode film layer and the positive electrode active material layer in the second direction satisfies 1mm≤OH2≤3mm, wherein any two of the first direction, the second direction, and the thickness direction of the battery cell are perpendicular to each other.

[0133] In this application, the dimensions of the negative electrode film layer in the second direction and the dimensions of the positive electrode active material layer in the second direction can be measured using methods and instruments known in the art. As an example, they can be measured using a micrometer (e.g., a Mitutoyo 293-100 model with an accuracy of 0.1 μm).

[0134] In this application, any two of the first direction, the second direction, and the thickness direction of the battery cell are perpendicular to each other. The first direction can be either the length direction or the thickness direction of the battery cell. When the first direction (X) is the length direction of the battery cell, the second direction (Y) is the width direction of the battery cell, as shown below. Figure 1 As shown; when the first direction is the width direction of the battery cell, the second direction is the length direction of the battery cell.

[0135] In some embodiments, the size difference OH2 between the negative electrode film layer and the positive electrode active material layer in the second direction can be 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3 mm, or any value between the two.

[0136] In this embodiment, the size difference OH2 between the negative electrode film layer and the positive electrode active material layer in the second direction is within the above-mentioned range, which helps to provide sufficient lithium insertion sites on the negative electrode sheet, thereby helping to reduce the probability of lithium plating on the negative electrode sheet, and thus helping to improve the cycle performance of the battery cell.

[0137] [Positive electrode plate]

[0138] In some embodiments, the lateral surface density of the positive electrode active material layer in a fully discharged state of the battery cell is 320 mg / 1540.25 mm². 2 -400mg / 1540.25mm 2 .

[0139] In some embodiments, the compaction density of the positive electrode active material layer of a single battery cell in a fully discharged state is greater than or equal to 2.3 g / cm³. 3 .

[0140] In this application, the compaction density of the positive electrode active material layer can be measured using methods and instruments known in the art. As an example, the battery is placed in a 25°C oven and left to stand for 2 hours. Once the battery temperature is maintained at 25°C, it is discharged at a constant current of 1 / 3C to 2.5V and left to stand for 30 minutes. Then, it is discharged at a constant voltage of 2.5V to 0.05C. The battery is disassembled to obtain the positive electrode sheet. The residual electrolyte is treated with dimethyl carbonate solvent, the electrode sheet is dried, and cut into pieces with an area of ​​S (in cm²). 2 Take a small circular sheet and obtain its mass as W1 (in g). Measure the thickness of the positive electrode sheet as T1 (in cm) using a micrometer. Then, wipe off the positive electrode film layer of the weighed electrode sheet, weigh the current collector, and record the mass as W2 (in g). Measure the thickness of the current collector as T2 using a micrometer. The compaction density of the positive electrode film layer is then calculated as PD = (W1 - W2) / [(T1 - T2) × S], in g / cm³. 3 .

[0141] In some embodiments, the compaction density of the positive electrode film layer in a fully discharged state of a single battery cell can be 2.3 g / cm³. 3 2.31 g / cm 3 2.32 g / cm 3 2.33 g / cm 3 2.34 g / cm 3 2.35g / cm 3 2.36 g / cm 3 2.37 g / cm 3 2.38g / cm 3 2.39 g / cm 3 2.40 g / cm 3 2.41 g / cm3 2.42 g / cm 3 2.43 g / cm 3 2.44 g / cm 3 2.45g / cm 3 2.46 g / cm 3 2.47 g / cm 3 2.48 g / cm 3 2.49 g / cm 3 2.5g / cm 3 2.51g / cm 3 2.52g / cm 3 2.53g / cm 3 2.54 g / cm 3 2.55g / cm 3 2.56 g / cm 3 2.57g / cm 3 2.58g / cm 3 2.59g / cm 3 2.6g / cm 3 2.61 g / cm 3 2.62 g / cm 3 2.63 g / cm 3 2.64 g / cm 3 2.65g / cm 3 Or the range of values ​​between any two.

[0142] High compaction density helps increase the loading of positive electrode active material on the positive electrode sheet; low compaction density helps increase the porosity of the film layer and improve liquid retention performance. In the embodiments of this application, when the battery cell is in a fully discharged state, the compaction density of the positive electrode film layer is within the above-mentioned range, which helps to balance a high loading of active material with a suitable pore structure, improve the liquid retention rate of the electrode sheet, reduce polarization resistance, and thus improve the cycle performance and capacity utilization of the battery.

[0143] In some embodiments, the compaction density of the positive electrode film layer in the fully discharged state of the battery cell is 2.3 g / cm³. 3 -2.6g / cm 3 .

[0144] In some embodiments, the positive electrode active material layer includes a positive electrode active material, which includes lithium-containing transition metal oxide particles and lithium-containing transition metal phosphate particles.

[0145] Lithium-containing transition metal oxides have high specific capacity. In this embodiment, including lithium-containing transition metal oxides as the positive electrode active material helps to improve the energy density of the battery cell. Lithium-containing transition metal phosphates have good cycle performance. In this embodiment, including lithium-containing transition metal phosphates as the positive electrode active material helps to improve the cycle performance of the battery cell.

[0146] In some embodiments, the mass ratio of lithium transition metal oxide particles to lithium transition metal phosphate particles is 5:5-9:1.

[0147] In some embodiments, the mass ratio of lithium transition metal oxide particles to lithium transition metal phosphate particles can be 5:5, 5.5:4.5, 6:4, 6.5:3.5, 7:3, 7.5:2.5, 8:2, 8.5:1.5, 9:1, or any range between the two.

[0148] In the embodiments of this application, the mass ratio of lithium transition metal oxide particles to lithium transition metal phosphate particles is within the above-mentioned range, which helps to improve the cycle performance of the battery cell while taking into account the energy density.

[0149] In some embodiments, the mass ratio of lithium transition metal oxide particles to lithium transition metal phosphate particles is 6:4-8:2.

[0150] In the embodiments of this application, the mass ratio of lithium transition metal oxide particles to lithium transition metal phosphate particles is within the above-mentioned range, which helps to further improve the cycle performance of the battery cell while taking into account the energy density.

[0151] In some embodiments, the lithium-containing transition metal oxide particles comprise components represented by the following general formula:

[0152] Li a1 Ni x1 Co y1 M1 z1 M2 w1 O 2-b1 Formula I,

[0153] Wherein, M1 includes one or more of Mn and Al, M2 includes one or more of Zr, B, Mg, Ti, W, Mo, Nb, Ta, Sr, Sb, and K, 0.8≤a1≤1.2, 0≤x1≤1, 0≤y1≤1, 0≤z1≤1, 0≤w1≤0.1, and -0.1≤b1≤0.1.

[0154] In some implementations, a1 can be selected as 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2 or any range between the two.

[0155] In some implementations, x1 can be selected as 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, or any range between the two.

[0156] In some implementations, y1 can be selected as 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, or any range between the two.

[0157] In some implementations, z1 can be selected as 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, or any range between the two.

[0158] In some implementations, w1 can be selected as 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or any range between the two.

[0159] In some implementations, b1 can be selected as -0.1, -0.05, 0, 0.05, 0.1, or any range between the two.

[0160] When the positive electrode active material layer includes the above-mentioned lithium-containing transition metal oxides, the specific capacity of the positive electrode active material can be further improved, thereby further improving the energy density of the battery cell.

[0161] In some embodiments, the lithium transition metal phosphate particles comprise components represented by the following general formula:

[0162] Li x A y Me a M b P 1-c X c Y z Formula II,

[0163] Wherein, 0.1≤x≤1.3, 0≤y≤1.3, and 0.8≤x+y≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; Y includes one or more of O and F.

[0164] In some implementations, x can be selected as 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3, or any range between the two.

[0165] In some implementations, y can be selected as 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3, or any range between the two.

[0166] In some implementations, x+y can be selected as 0.8, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3 or any range between the two.

[0167] In some implementations, 'a' can be selected as 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.3, 1.4, 1.5 or any range between the two.

[0168] In some implementations, b can be selected as 0, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, or any range between the two.

[0169] In some implementations, a+b can be selected as 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.3, 1.4, 1.5 or any range between the two.

[0170] In some implementations, c can be selected as 0, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, or any range between the two.

[0171] In some implementations, z can be selected as 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5, or any range between the two.

[0172] Lithium-containing transition metal phosphates, including the components shown in the above general formula, have good thermal stability and cycle stability, which helps to improve the safety and cycle performance of batteries.

[0173] In some embodiments, the lithium transition metal phosphate particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium vanadium fluoride phosphate, lithium manganese iron phosphate, lithium fluoride iron phosphate, lithium manganese iron phosphate, and modified materials thereof.

[0174] In some embodiments, the lithium-containing transition metal phosphate particles include one or more of lithium manganese iron phosphate and its modified materials.

[0175] Compared to other lithium-containing transition metal phosphates, lithium manganese iron phosphate has a higher voltage plateau and a smaller voltage difference with lithium-containing transition metal oxides, which is beneficial for the specific capacity of lithium-containing transition metal phosphates and thus further improves the volumetric energy density of battery cells.

[0176] 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.).

[0177] 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.

[0178] 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.

[0179] [Negative electrode plate]

[0180] In some embodiments, the negative electrode sheet further includes a negative electrode film layer disposed on at least one side of the negative electrode current collector in the thickness direction of the battery cell, wherein the density of the negative electrode film layer on one side is greater than or equal to 160 mg / 1540.25 mm² when the battery cell is fully discharged. 2 .

[0181] In this application, the one-sided density of the negative electrode film layer can be tested using methods and instruments known in the art. As an example, the one-sided density test method for the positive electrode active material layer can be referred to.

[0182] In some embodiments, the negative electrode sheet further includes a negative electrode film layer disposed on at least one side of the negative electrode current collector in the thickness direction of the battery cell. When the battery cell is fully discharged, the unilateral density of the negative electrode film layer can be 160 mg / 1540.25 mm². 2 165mg / 1540.25mm 2 170mg / 1540.25mm 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 205mg / 1540.25mm 2 210mg / 1540.25mm 2 215mg / 1540.25mm 2 220mg / 1540.25mm 2 Or the range of values ​​between any two.

[0183] The fact that the negative electrode active material layer is within the above range indicates that the negative electrode sheet has a high active material loading, which helps to improve the volumetric energy density of the battery cell.

[0184] In some embodiments, the negative electrode sheet further includes a negative electrode film layer disposed on at least one side of the negative electrode current collector in the thickness direction of the battery cell, wherein the one-sided density of the negative electrode film layer is 180 mg / 1540.25 mm² when the battery cell is fully discharged.2 -200mg / 1540.25mm 2 .

[0185] In some embodiments, the compaction density of the negative electrode film layer in a fully discharged state of the battery cell is greater than or equal to 1.4 g / cm³. 3 .

[0186] In this application, the compaction density of the negative electrode film layer can be tested using methods and instruments known in the art. As an example, the compaction density test method for the positive electrode active material layer can be referred to.

[0187] In some embodiments, the compaction density of the negative electrode film layer in a fully discharged state of the battery cell can be 1.4 g / cm³. 3 1.41 g / cm 3 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 1.60g / cm 3 1.61 g / cm 3 1.62g / cm 3 1.63g / cm 3 1.64 g / cm 3 1.65g / cm 3 Or the range of values ​​between any two.

[0188] In some embodiments, the compaction density of the negative electrode film layer in the fully discharged state of the battery cell is 1.4 g / cm³. 3 -1.6g / cm 3 .

[0189] High compaction density helps increase the loading of negative electrode active material on the negative electrode sheet; while low compaction density helps increase the porosity of the film layer and improve liquid retention performance. In the embodiments of this application, when the battery cell is in a fully discharged state, the compaction density of the negative electrode film layer is within the above-mentioned range, which helps to balance a high loading of active material with a suitable pore structure, improve the liquid retention rate of the electrode sheet, reduce polarization resistance, and thus improve the cycle performance and capacity utilization of the battery.

[0190] In some embodiments, the negative electrode film layer includes a negative electrode active material, which includes graphite.

[0191] In some embodiments, the negative electrode active material includes one or more of natural flake graphite, artificial graphite, and microcrystalline graphite.

[0192] In some implementations, the negative electrode active material includes artificial graphite.

[0193] In some embodiments, the orientation degree of the negative electrode active material (OI) is 1.3-5.5, 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.

[0194] Orientation degree (OI) has a well-known meaning in the art; it represents the degree of order in the arrangement of crystals or particles in a material.

[0195] In this application, the orientation degree (OI) value of the negative electrode active material can be tested using methods and instruments known in the art. As an example, an X-ray diffractometer (such as a Bruker D8 Discover) can be used for testing, and the testing can be performed according to JISK0131-1996 and JB / T 4220-2011, obtaining the X-ray diffraction pattern of the material. Based on the formula OI value = I... 004 / I 110 The OI value of the material was calculated. 004 I is the integrated area of ​​the diffraction peaks of the crystalline carbon 004 crystal plane in the material. 110 This represents the integrated area of ​​the peak on the 110 crystal plane of crystalline carbon in the material. 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 2 = 1.5418 Å, a scanning 2θ angle range of 20°-80°, and a scanning rate of 4° / min.

[0196] In some embodiments, the orientation degree (OI) value of the negative electrode active material can be selected as 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, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, or any value range between the two.

[0197] A low OI value indicates poor orientation and high internal disorder in the material, affecting its structural stability. Conversely, a high OI value indicates highly ordered crystal arrangement, reduced porosity, and reduced liquid retention capacity, thus increasing polarization resistance. In the embodiments of this application, the OI value of the negative electrode active material is within the aforementioned range, which helps to balance structural stability and liquid retention capacity, thereby contributing to improved cycle performance of the battery cell.

[0198] In some implementations, the orientation degree (OI) of the negative electrode active material is 2.5-4.

[0199] In this embodiment, the OI value of the negative electrode active material is within the above range, which helps to further improve the structural stability and liquid retention capacity of the negative electrode active material and improve the cycle performance of the battery cell.

[0200] In some embodiments, the volumetric particle size distribution D of the negative electrode active material V 50 is 16μm-22μm.

[0201] In this application, the volumetric particle size distribution D V The value of 50 has a well-known meaning in the art, representing the particle size corresponding to a cumulative volumetric distribution percentage of 50%, which can be tested using methods and instruments known in the art. As an example, particle size distribution can be conveniently determined using a laser particle size analyzer, referring to GB / T 19077-2016, Laser Diffraction Method. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0202] In some embodiments, the volumetric particle size distribution D of the negative electrode active material V 50 can be 16μm, 16.5μm, 17μm, 17.5μm, 18μm, 18.5μm, 19μm, 19.5μm, 20μm, 20.5μm, 21μm, 21.5μm, 22μm or any value between the two.

[0203] In this embodiment of the application, the D of the negative electrode active material VWithin the above range, 50 helps to reduce the polarization impedance of the battery and further improve the cycle performance of the battery.

[0204] 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.).

[0205] 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).

[0206] 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.

[0207] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0208] [Septum]

[0209] In some implementations, the battery cell also includes a separator.

[0210] 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.

[0211] 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.

[0212] [Electrolytes]

[0213] In some implementations, the battery cell also includes an electrolyte.

[0214] 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.

[0215] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0216] 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.

[0217] 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.

[0218] 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.

[0219] Battery device

[0220] This application also provides a battery device, which includes the battery cell provided in this application.

[0221] Battery devices include one or more of the following: battery modules, battery packs, and energy storage batteries.

[0222] Electrical appliances

[0223] This application also provides an electrical device, which includes a battery device provided in this application embodiment. The battery device is used to provide electrical energy. The battery can be used as the power source for the electrical device. The electrical device can be, but is not limited to, mobile devices (such as mobile phones, tablets, laptops, etc.), electric vehicles (such as 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.

[0224] Electrical devices can choose the specific type of battery according to their usage needs, such as individual battery cells, battery modules, or battery packs.

[0225] Energy storage devices

[0226] This application also provides an energy storage device, which includes the battery device provided in this application embodiment. The battery device is used to store electrical energy. The battery device can be used as an energy storage unit of the energy storage device. The energy storage unit can be, but is not limited to, an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system, etc.

[0227] Figure 3 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0228] Another example of an electrical 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.

[0229] Example

[0230] 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.

[0231] I. Preparation Method

[0232] Example 1

[0233] (1) Preparation of positive electrode sheet

[0234] Preparation of positive electrode active material layer slurry: LiNi 0.92 Co 0.04 Mn 0.04 O2, LiMn 0.3 Fe 0.7 PO4, conductive carbon black, and binder PVDF are mixed in a mass ratio of 68.6:29.4:1:1, NMP solvent is added, and the mixture is stirred under vacuum until the system is homogeneous to obtain the positive electrode film slurry.

[0235] The positive electrode active material slurry was uniformly coated onto both sides of an aluminum foil with a thickness of 13 μm. After air drying at room temperature, it 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 2.55 g / cm³. 3;

[0236] Preparation of insulating layer slurry: ceramic particles Al2O3 (purchased from Keliansheng New Materials Co., Ltd., model L30), polyvinylidene fluoride PVDF, and dispersant ammonium polyacrylate are mixed at a mass ratio of 62:25:3. NMP solvent is added and the mixture is stirred in a vacuum mixing tank until homogeneous to obtain insulating ceramic slurry. It is then coated on both sides of the electrode sheet together with the positive electrode film layer.

[0237] Aluminum foil is laser-cut to obtain the positive electrode tab.

[0238] (2) Preparation of negative electrode sheet

[0239] Preparation of negative electrode film slurry: Artificial graphite negative electrode active material, polyvinyl alcohol binder, and SP-Li conductive agent are thoroughly mixed and ball-milled in a deionized water solvent system at a mass ratio of 90:5:5 to obtain a negative electrode slurry; wherein, the OI value of the artificial graphite negative electrode active material is 3, and D... V 50 is 19.5μm;

[0240] The negative electrode film slurry was uniformly coated onto both sides of an 8 μm thick copper foil, vacuum dried overnight at 110°C, and then cold-pressed to obtain the negative electrode sheet. The compaction density of the negative electrode film was 1.6 g / cm³. 3 The copper foil is then laser-cut to obtain the negative electrode tab. Next, the electrode sheet is die-cut, sliced, and chamfered. The chamfering process includes cutting the four corners of the negative current collector of the negative current collector to obtain an R-shaped chamfer with a chamfer radius of 1.5% of the width of the negative current collector. The chamfered electrode sheet is then sliced ​​to obtain the negative electrode sheet.

[0241] (3) Diaphragm

[0242] Porous alumina was added to NMP (N-methylpyrrolidone) solvent, stirred evenly, and then sprayed onto both sides of a polyethylene base film and dried. PVDF was dissolved in NMP (N-methylpyrrolidone) solvent, stirred evenly, and then sprayed onto the two surfaces of the porous alumina layer away from the base film. After drying, a membrane with a porous, continuous morphology of the adhesive layer was obtained.

[0243] The polyethylene film has a thickness of 11 μm, the porous alumina layer has a thickness of 1.5 μm on one side, and the PVDF layer has a thickness of 0.5 μm on one side.

[0244] (4) Electrolyte

[0245] 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.

[0246] (5) Battery manufacturing

[0247] The cut positive and negative electrode sheets are stacked in a Z-shaped stacking method, with the stacking order being "positive electrode sheet - separator - negative electrode sheet - separator" to form an electrode assembly. The baked electrode assembly is placed in an aluminum-plastic film, liquid is injected, vacuum is applied, and the film is hot-pressed to form an airtight package, finally obtaining a stacked soft-pack battery cell.

[0248] In Example 1, the prepared battery cell, under fully discharged state, had a one-sided lateral density of 330 mg / 1540.25 mm² for the positive electrode active material layer. 2 The single-sided coating surface density of the negative electrode film is 185 mg / 1540.25 mm. 2 The positive electrode current collector has a length of 545 mm and a width of 118 mm; the negative electrode current collector has a length of 545 mm and a width of 119.5 mm; the positive electrode active material layer has a dimension of 541 mm in the length direction and 118 mm in the width direction of the battery cell; the negative electrode film layer has a dimension of 545 mm in the length direction and 119.5 mm in the width direction of the battery cell; the dimension difference OH1 between the negative electrode film layer and the positive electrode active material layer in the length direction of the battery cell is 4 mm; the dimension difference OH2 between the negative electrode film layer and the positive electrode active material layer in the width direction of the battery cell is 1.5 mm; the first insulating layer and the second insulating layer are disposed on opposite sides of the positive electrode active material layer along the length direction of the battery cell; the dimension D1 of the first insulating layer is 1.5 mm and the dimension D2 of the second insulating layer is 2.5 mm in the length direction of the battery cell.

[0249] Example 2

[0250] The preparation method of Example 2 is basically the same as that of Example 1, except that the size D2 of the second insulating layer in the length direction of the battery cell is reduced by 0.5 mm, that is, D2 is adjusted to 2 mm; at the same time, the size of the positive electrode active material layer in the length direction of the battery cell is increased by 0.5 mm.

[0251] Example 3

[0252] The preparation method of Example 3 is basically the same as that of Example 1, except that the size D2 of the second insulating layer in the length direction of the battery cell is increased by 1 mm, that is, D2 is adjusted to 3.5 mm; at the same time, the size of the positive electrode active material layer in the length direction of the battery cell is reduced by 1 mm.

[0253] Example 4

[0254] The preparation method of Example 4 is basically the same as that of Example 1, except that the size D2 of the second insulating layer in the length direction of the battery cell is reduced by 1.5 mm, that is, D2 is adjusted to 1 mm; at the same time, the size of the positive electrode active material layer in the length direction of the battery cell is increased by 1.5 mm.

[0255] Example 5

[0256] The preparation method of Example 5 is basically the same as that of Example 1, except that the size D2 of the second insulating layer in the length direction of the battery cell is increased by 2 mm, that is, D2 is adjusted to 4.5 mm; at the same time, the size of the positive electrode active material layer in the length direction of the battery cell is decreased by 2 mm.

[0257] Example 6

[0258] The preparation method of Example 6 is basically the same as that of Example 1, except that the size D1 of the first insulating layer in the length direction of the battery cell is increased by 1 mm, that is, D1 is adjusted to 2.5 mm; at the same time, the size of the positive electrode active material layer in the length direction of the battery cell is decreased by 1 mm.

[0259] Example 7

[0260] The preparation method of Example 7 is basically the same as that of Example 1, except that the size D1 of the first insulating layer in the length direction of the battery cell is reduced by 0.5 mm, that is, D1 is adjusted to 1 mm; at the same time, the size of the positive electrode active material layer in the length direction of the battery cell is increased by 0.5 mm.

[0261] Example 8

[0262] The preparation method of Example 8 is basically the same as that of Example 1, except that artificial graphite with an orientation degree OI value of 1.3 is selected as the negative electrode active material.

[0263] Example 9

[0264] The preparation method of Example 9 is basically the same as that of Example 1, except that artificial graphite with an orientation degree OI value of 5.5 is selected as the negative electrode active material.

[0265] Example 10

[0266] The preparation method of Example 10 is basically the same as that of Example 1, except that the D of the negative electrode active material is...V 50 is 26μm.

[0267] Example 11

[0268] The preparation method of Example 11 is basically the same as that of Example 1, except that the D of the negative electrode active material is... V 50 is 11μm.

[0269] Example 12

[0270] The preparation method of Example 12 is basically the same as that of Example 1, except that when preparing the positive electrode active material layer slurry, LiNi is used. 0.92 Co 0.04 Mn 0.04 O2, LiMn 0.3 Fe 0.7 The mass ratio of PO4, conductive carbon black, and PVDF binder is adjusted to 49:49:1:1.

[0271] Example 13

[0272] The preparation method of Example 13 is basically the same as that of Example 1, except that when preparing the positive electrode active material layer slurry, LiNi is used. 0.92 Co 0.04 Mn 0.04 O2, LiMn 0.3 Fe 0.7 The mass ratio of PO4, conductive carbon black, and PVDF binder is adjusted to 88.2:9.8:1:1.

[0273] Example 14

[0274] The preparation method of Example 14 is basically the same as that of Example 1, except that the coating weight of the positive electrode active material layer slurry and the negative electrode film layer slurry is adjusted so that the single-sided density of the positive electrode film layer in the fully discharged state is 400 mg / 1540.25 mm. 2 The single-sided density of the negative electrode film is 215 mg / 1540.25 mm. 2 .

[0275] Comparative Example 4

[0276] The preparation method of Comparative Example 4 is basically the same as that of Example 1, except that the coating weight of the positive electrode active material layer slurry and the negative electrode film layer slurry is adjusted so that the single-sided density of the positive electrode film layer in the fully discharged state is 300 mg / 1540.25 mm. 2 The single-sided density of the negative electrode film is 160 mg / 1540.25 mm. 2 .

[0277] Comparative Example 1

[0278] The preparation method of Comparative Example 1 is basically the same as that of Comparative Example 4, except that a second insulating layer is not set; at the same time, the size of the positive electrode active material layer in the length direction of the battery cell is increased by 2.5 mm.

[0279] Comparative Example 2

[0280] The preparation method of Comparative Example 2 is basically the same as that of Comparative Example 4. The difference is that the size of the positive electrode current collector is 542.5 mm along the length of the battery; no second insulating layer is provided; and the four corners of the positive electrode current collector are chamfered in an R-shape with a chamfer radius of 1.5% of the width of the positive electrode current collector.

[0281] Comparative Example 3

[0282] The preparation method of Comparative Example 3 is basically the same as that of Comparative Example 1, except that the coating weight of the positive electrode active material layer slurry and the negative electrode film layer slurry is adjusted so that the single-sided density of the positive electrode film layer in the fully discharged state is 330 mg / 1540.25 mm. 2 The single-sided density of the negative electrode film is 185 mg / 1540.25 mm. 2 .

[0283] II. Performance Testing

[0284] 1. Cyclic capacity retention

[0285] At 25℃, the battery is charged to 4.25V at a charging rate of 0.33C (the nominal capacity), then charged to 0.05C at 4.25V, left to stand for 10 minutes, and then discharged to 2.5V at a discharging rate of 1C, left to stand for 10 minutes. 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 is repeated 1000 times, and the discharge capacity of the battery cell at this point is recorded as E2. The cycle capacity retention rate @1000Cls = E2 / E1 × 100%.

[0286] 2. Volumetric energy density

[0287] Let the battery stand at 25℃ for 2 hours to ensure the battery temperature remains at 25℃. Charge the battery at 0.33C at 25℃ to the charging cutoff voltage of 4.25V, then continue constant voltage charging at this cutoff voltage until the current reaches 0.05C, at which point charging stops (where C represents the battery's rated capacity). Let the battery stand at 25℃ for 1 hour, then discharge it at 0.33C at 25℃ to the discharge cutoff voltage of 2.5V, recording the total discharge energy as E0. Measure the battery's length, width, and height, and calculate the battery's volume V0 = length × width × height. The battery's volumetric energy density = battery discharge energy E0 / battery volume V0, in Wh / L.

[0288] III. Test Results

[0289] The test results of the above embodiments and comparative examples are shown in Tables 1-7.

[0290] Table 1

[0291]

[0292] Table 2

[0293]

[0294] As can be seen from the comparison of the embodiments and comparative examples, the battery cell includes an electrode assembly and a housing. The electrode assembly is housed in the housing, and the housing material is a soft-pack material. The electrode assembly includes a positive electrode sheet and a negative electrode sheet, which are alternately stacked. The negative electrode sheet includes a negative current collector, which includes a negative current collection portion, and the negative current collection portion has chamfers around its perimeter. The positive electrode sheet includes a positive current collector, which includes a positive current collection portion and a positive electrode tab disposed on one side of the positive current collection portion extending along a first direction, which is perpendicular to the battery cell. The thickness direction of the positive electrode sheet; the positive electrode sheet also includes a positive electrode film layer disposed on at least one side of the positive electrode current collector along the thickness direction of the battery cell. The positive electrode film layer includes a positive electrode active material layer and a first insulating layer and a second insulating layer disposed on opposite sides of the positive electrode active material layer in a first direction. The first insulating layer is disposed on the side of the positive electrode active material layer closer to the positive electrode tab, and the second insulating layer is disposed on the side of the positive electrode active material layer away from the positive electrode tab. When the battery cell is fully discharged, the single-sided density of the positive electrode active material layer is greater than or equal to 320 mg / 1540.25 mm. 2 This helps to balance high volumetric energy density, processing yield, and good cycle stability of battery cells.

[0295] As can be seen from the comparison between Examples 1 and Examples 8-9, the orientation degree OI value of the negative electrode active material is in the range of 2.5-4, which helps to further improve the cycle performance of the battery cell.

[0296] As can be seen from the comparison between Example 1 and Examples 10-11, the volume particle size distribution D of the negative electrode active material is... V The 50 μm range of 16-22 μm helps to further improve the cycle performance of battery cells.

[0297] Table 3

[0298]

[0299] As can be seen from the comparison between Examples 1-2 and Examples 3-5, the size D2 of the second insulating layer in the first direction is in the range of 2mm-3mm, which helps to further improve the cycle performance and volumetric energy density of the battery.

[0300] Table 4

[0301]

[0302] As can be seen from the comparison of Examples 1, 7 and 6, the dimension D1 of the first insulating layer in the first direction is 1mm-2mm, which helps to further improve the cycle performance of the battery while taking into account the volumetric energy density.

[0303] Table 5

[0304]

[0305] As can be seen from the comparison between Examples 1 and Examples 12-13, a mass ratio of lithium transition metal oxide particles to lithium transition metal phosphate particles in the range of 6:4-8:2 helps to further improve the cycle performance of the battery cell while taking into account the energy density.

[0306] Table 6

[0307]

[0308] As can be seen from the comparison between Comparative Example 1 and Comparative Example 3, when no insulating layer is provided on the side of the positive electrode active material layer away from the positive electrode tab, the single-sided density of the positive electrode active material layer in the fully discharged state of the battery cell is greater than or equal to 320mg / 1540.25mm². 2 The single-sided surface density of the negative electrode active material is greater than or equal to 160 mg / 1540.25 mm². 2 The battery's cycle performance deteriorates.

[0309] As can be seen from the comparison between Example 1 and Comparative Examples 2-3, the battery cell includes an electrode assembly and a housing. The electrode assembly is housed within the housing, and the housing is made of a soft-pack material. The electrode assembly includes a positive electrode and a negative electrode, which are alternately stacked. The negative electrode includes a negative current collector, which includes a negative current collection portion with chamfered edges around its perimeter. The positive electrode includes a positive current collector, which includes a positive current collection portion and a positive electrode tab disposed on one side of the positive current collection portion extending along a first direction. The first direction is perpendicular to the thickness direction of the battery cell; the positive electrode sheet also includes a positive electrode film layer disposed along the thickness direction of the battery cell on at least one side of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material layer and a first insulating layer and a second insulating layer disposed on opposite sides of the positive electrode active material layer in the first direction. The first insulating layer is disposed on the side of the positive electrode active material layer closer to the positive electrode tab, and the second insulating layer is disposed on the side of the positive electrode active material layer away from the positive electrode tab, which helps to improve the cycle performance of the battery cell while taking into account the volumetric energy density.

[0310] A comparison of Examples 1 and 14-15 shows that, under fully discharged conditions, the single-sided density of the positive electrode active material layer is greater than or equal to 320 mg / 1540.25 mm². 2 Furthermore, the single-sided density of the positive electrode active material layer is 320 mg / 1540.25 mm². 2 -400 mg / 1540.25 mm 2 Within this range, it helps to further improve the cycle performance of individual battery cells while also taking into account volumetric energy density.

[0311] Table 7

[0312]

[0313] As can be seen from the comparison between Comparative Example 4 and Comparative Example 2, the positive electrode sheet is not chamfered. The positive electrode sheet includes a first insulating layer and a second insulating layer, and OH1-(D1+D2)=0mm, which helps to improve the cycle performance of the battery cell and take into account the volumetric energy density.

[0314] 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 and a housing, wherein the electrode assembly is housed in the housing, and the housing is made of a soft-pack material; The electrode assembly includes a positive electrode and a negative electrode, wherein the positive electrode and the negative electrode are alternately stacked. The negative electrode sheet includes a negative electrode current collector, the negative electrode current collector includes a negative electrode current collection section, and the negative electrode current collection section has chamfers around its perimeter; The positive electrode sheet includes a positive current collector, the positive current collector includes a positive current collector portion and a positive electrode tab disposed on one side of the positive current collector portion extending along a first direction, the first direction being perpendicular to the thickness direction of the battery cell. The positive electrode sheet further includes a positive electrode film layer disposed along the thickness direction of the battery cell on at least one side of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material layer and a first insulating layer and a second insulating layer disposed on opposite sides of the positive electrode active material layer in the first direction. The first insulating layer is disposed on the side of the positive electrode active material layer closer to the positive electrode tab, and the second insulating layer is disposed on the side of the positive electrode active material layer away from the positive electrode tab. When the battery cell is fully discharged, the unilateral density of the positive electrode active material layer is greater than or equal to 320 mg / 1540.25 mm². 2 .

2. The battery cell according to claim 1, characterized in that, The dimension D1 of the first insulating layer in the first direction is 1mm-2.5mm.

3. The battery cell according to claim 1, characterized in that, The dimension D1 of the first insulating layer in the first direction is 1mm-2mm.

4. The battery cell according to claim 1, characterized in that, The dimension D2 of the second insulating layer in the first direction is 1mm-4.5mm.

5. The battery cell according to claim 1, characterized in that, The dimension D2 of the second insulating layer in the first direction is 2mm-3mm.

6. The battery cell according to claim 1, characterized in that, The materials of the first insulating layer and the second insulating layer each independently include one or more of alumina, zirconium oxide, and titanium oxide.

7. The battery cell according to claim 1, characterized in that, Both the first insulating layer and the second insulating layer are made of aluminum oxide.

8. The battery cell according to claim 1, characterized in that, The chamfer includes either an R-type chamfer or a C-type chamfer.

9. The battery cell according to claim 1, characterized in that, The chamfer is an R-type chamfer.

10. The battery cell according to claim 1, characterized in that, The negative electrode sheet further includes a negative electrode film layer disposed on at least one side of the negative electrode current collector in the thickness direction of the battery cell. In the first direction, the size difference OH1 between the negative electrode film layer and the positive electrode active material layer satisfies 2mm≤OH1≤6mm, and the size of the negative electrode film layer is larger than the size of the positive electrode active material layer in the first direction.

11. The battery cell according to claim 10, characterized in that, The size difference OH1 between the negative electrode film layer and the positive electrode active material layer in the first direction satisfies 2mm≤OH1≤5mm.

12. The battery cell according to claim 10, characterized in that, The size difference OH1 between the negative electrode film layer and the positive electrode active material layer in the first direction satisfies OH1-(D1+D2)=0mm, where D1 is the size of the first insulating layer in the first direction and D2 is the size of the second insulating layer in the first direction.

13. The battery cell according to claim 10, characterized in that, In the second direction, the size difference OH2 between the negative electrode film layer and the positive electrode active material layer satisfies 1mm≤OH2≤3mm, wherein any two of the first direction, the second direction and the thickness direction of the battery cell are perpendicular to each other, and in the second direction, the size of the negative electrode film layer is larger than the size of the positive electrode active material layer.

14. The battery cell according to claim 1, characterized in that, When the battery cell is fully discharged, the lateral density of the positive electrode active material layer is 320 mg / 1540.25 mm². 2 -400mg / 1540.25mm 2 .

15. The battery cell according to claim 1, characterized in that, When the battery cell is fully discharged, the compaction density of the positive electrode active material layer is greater than or equal to 2.3 g / cm³. 3 .

16. The battery cell according to claim 1, characterized in that, When the battery cell is fully discharged, the compaction density of the positive electrode active material layer is 2.3 g / cm³. 3 -2.6g / cm 3 .

17. The battery cell according to claim 1, characterized in that, The positive electrode active material layer includes a positive electrode active material, which includes lithium transition metal oxide particles and lithium transition metal phosphate particles.

18. The battery cell according to claim 17, characterized in that, The mass ratio of the lithium-containing transition metal oxide particles to the lithium-containing transition metal phosphate particles is 5:5-9:

1.

19. The battery cell according to claim 17, characterized in that, The mass ratio of the lithium-containing transition metal oxide particles to the lithium-containing transition metal phosphate particles is 6:4-8:

2.

20. The battery cell according to claim 17, characterized in that, The lithium-containing transition metal oxide particles comprise components represented by the following general formula: Li a1 Ni x1 Co y1 M1 z1 M2 w1 O 2-b1 Formula I Wherein, M1 includes one or more of Mn and Al, M2 includes one or more of Zr, B, Mg, Ti, W, Mo, Nb, Ta, Sr, Sb, and K, 0.8≤a1≤1.2, 0≤x1≤1, 0≤y1≤1, 0≤z1≤1, 0≤w1≤0.1, and -0.1≤b1≤0.

1.

21. The battery cell according to claim 17, characterized in that, The lithium-containing transition metal phosphate particles comprise components represented by the following general formula: Li x A y Me a M b P 1-c X c Y z Formula II Wherein, 0.1≤x≤1.3, 0≤y≤1.3, and 0.8≤x+y≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; Y includes one or more of O and F.

22. The battery cell according to claim 17, characterized in that, The lithium-containing transition metal phosphate particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium vanadium fluoride phosphate, lithium manganese iron phosphate, lithium fluoride iron phosphate, lithium manganese iron phosphate, and their modified materials.

23. The battery cell according to claim 17, characterized in that, The lithium-containing transition metal phosphate particles include one or more of lithium manganese iron phosphate and its modified materials.

24. The battery cell according to claim 1, characterized in that, The negative electrode sheet further includes a negative electrode film layer disposed on at least one side of the negative electrode current collector in the thickness direction of the battery cell. When the battery cell is fully discharged, the density of the negative electrode film layer on one side is greater than or equal to 160 mg / 1540.25 mm². 2 .

25. The battery cell according to claim 24, characterized in that, The single-sided density of the negative electrode film is 180 mg / 1540.25 mm. 2 -200mg / 1540.25mm 2 .

26. The battery cell according to claim 24, characterized in that, When the battery cell is fully discharged, the compaction density of the negative electrode film layer is greater than or equal to 1.4 g / cm³. 3 .

27. The battery cell according to claim 24, characterized in that, When the battery cell is fully discharged, the compaction density of the negative electrode film is 1.4 g / cm³. 3 -1.6g / cm 3 .

28. The battery cell according to claim 24, characterized in that, The negative electrode film layer includes a negative electrode active material, which includes graphite.

29. The battery cell according to claim 24, characterized in that, The negative electrode film layer includes a negative electrode active material, which includes one or more of natural flake graphite, artificial graphite, and microcrystalline graphite.

30. The battery cell according to claim 28, characterized in that, The orientation degree of the negative electrode active material is 1.3-5.5, 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.

31. The battery cell according to claim 30, characterized in that, The orientation degree (OI) of the negative electrode active material is 2.5-4.

32. The battery cell according to any one of claims 28-31, characterized in that, The volume particle size distribution D of the negative electrode active material V 50 is 16μm-22μm.

33. A battery device, characterized in that, Includes the battery cell as described in any one of claims 1-32.

34. An electrical appliance, characterized in that, The electrical device includes the battery device as described in claim 33, the battery device being used to provide electrical energy.

35. An energy storage device, characterized in that, The energy storage device includes the battery device as described in claim 33, the battery device being used to store electrical energy.

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