Battery cell, battery device, electric device, and energy storage device

Abstract

A battery cell, a battery device, an electric device, and an energy storage device. The battery cell comprises: a casing, an electrode assembly, and an electrolyte. The casing comprises a casing body and a top cover assembly. The top cover assembly comprises a top cover main body and an electrode terminal. The electrolyte comprises propylene carbonate at a mass ratio of 1% to 15%. The electrode assembly comprises a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet comprises a positive electrode film layer, and the negative electrode sheet comprises a negative electrode film layer. The negative electrode film layer comprises a negative electrode active material, and the degree of graphitization of the negative electrode film layer is 75% to 93%. The battery cell further comprises a first insulating member. The first insulating member is disposed between the top cover main body and the electrode terminal, and / or the first insulating member is disposed between the electrode assembly and the casing body, and the melting point of the first insulating member is greater than or equal to 200°C. Thus, high energy efficiency, long cycle life and good thermal safety performance of an energy storage battery are all achieved.

Description

Battery cells, battery packs, electrical devices and energy storage devices

[0001] Cross-references

[0002] This application incorporates, in its entirety, patent application number PCT / CN2025 / 085983, filed on March 28, 2025, entitled "Lithium-ion secondary battery, battery device, power device, method for preparing positive electrode active material and method for preparing positive electrode sheet".

[0003] This application incorporates, in its entirety, patent application number PCT / CN2025 / 140517, filed on December 5, 2025, entitled “Battery Cell, Battery Device, Power Consumption Device and Energy Storage Device”. Technical Field

[0004] This application relates to the field of battery technology, specifically to a battery cell, a battery device, an electrical device, and an energy storage device. Background Technology

[0005] In recent years, the application of high-capacity battery cells in energy storage devices has become increasingly widespread. In various energy storage application scenarios, high capacity and long cycle life have become key performance indicators for evaluating energy storage batteries. This is especially true for large-scale energy storage power stations, whose large-scale, long-cycle operation places higher demands on battery cycle life and safety performance. To effectively delay battery performance degradation and reduce replacement frequency and maintenance costs, there is an urgent need to further develop battery cells that combine high capacity, long cycle life, and good safety performance. Summary of the Invention

[0006] This application aims to at least solve one of the technical problems existing in the background art. To this end, one object of this application is to provide a battery cell, battery device, power consumption device, and energy storage device that achieves a balance of high energy efficiency, long cycle life, and good thermal safety performance of the energy storage battery.

[0007] To address the aforementioned problems, an embodiment of the first aspect of this application provides a battery cell, comprising a casing, an electrode assembly, and an electrolyte. The casing includes a housing and a top cover assembly. The housing includes a receiving cavity with an opening. The top cover assembly is configured to cover the opening of the housing and includes a top cover body and electrode terminals. The electrolyte includes propylene carbonate, and based on the mass of the electrolyte, the mass percentage of propylene carbonate is 1%-15%. The electrode assembly is disposed in the receiving cavity and includes a positive electrode and a negative electrode. The positive electrode includes a positive current collector and a positive electrode film disposed on at least one side of the positive current collector. The electrode film layer includes a positive electrode active material, which includes a lithium phosphate having an olivine structure. The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector. The negative electrode film layer includes a negative electrode active material, which includes graphite. The graphitization degree of the negative electrode film layer is 75%-93%. The battery cell further includes a first insulating element, which is disposed between the top cover body and the electrode terminals, and / or between the electrode assembly and the housing. The melting point of the first insulating element is greater than or equal to 200°C.

[0008] Adding propylene carbonate (PC) to the electrolyte can effectively improve the energy efficiency (RTE) of a battery cell. Current technology generally suggests that propylene carbonate co-intercalates with lithium ions into the interlayer spacing of the graphite anode active material, causing the graphite layered structure to peel off. Propylene carbonate needs to be paired with highly graphitized graphite to alleviate the co-intercalation problem and improve the cycle life of the battery cell.

[0009] However, the applicant discovered that energy storage batteries differ from general power batteries, requiring extremely high battery life (e.g., over 15,000 cycles, far exceeding the 3,000-5,000 cycles required for power batteries). High-graphitization negative electrode films exhibit significantly increased expansion forces in the later stages of cycling, playing a dominant role in cycle life degradation. Using a low-graphitization negative electrode is necessary to mitigate this expansion and improve cycle life. Furthermore, to adapt to the power grid, energy storage batteries require constant-power charging. Even as capacity decreases in the later stages of cycling, the charging current remains high, effectively increasing the current rate. This leads to increased local overpotential at the negative electrode, making lithium metal deposition more likely and causing cycle life degradation. Propylene carbonate has a high dielectric constant; adding 1%-15% propylene carbonate to the electrolyte not only improves the RTE of the energy storage battery but also reduces the risk of lithium deposition in the later stages of cycling, thus contributing to improved cycle life of individual battery cells.

[0010] While the combination of a low-graphitization negative electrode and 1%-15% propylene carbonate is beneficial for improving the energy efficiency and cycle life of individual energy storage battery cells, under abnormal battery operation conditions such as high temperature, overcharging, or thermal runaway, the side reactions between the low-graphitization graphite and propylene carbonate are more intense. This causes the insulation components (with a melting point of generally 160℃-170℃) typically installed in the battery cell to melt, leading to short circuits and exacerbating thermal runaway. In contrast, the high-melting-point primary insulation component can maintain electrical isolation under abnormal operating conditions, improving battery thermal safety.

[0011] In summary, the embodiments of this application use a negative electrode containing 1%-15% propylene carbonate with a low graphitization degree (75%-93%), and provide a first insulating component with a melting point greater than or equal to 200°C between the top cover body and the electrode terminals, and / or between the electrode assembly and the shell, thereby achieving a balance between high energy efficiency, long cycle life and good thermal safety performance of the energy storage battery, and realizing synergistic optimization of performance and safety.

[0012] In some embodiments, the melting point of the first insulating element is 200°C-400°C, optionally 260°C-350°C.

[0013] In this embodiment, the melting point of the first insulating element is within the above-mentioned range, which further improves the cycle life and safety performance of the high-capacity energy storage battery.

[0014] In some embodiments, the propylene carbonate accounts for 4%-6% of the total mass.

[0015] In this embodiment, the mass percentage of propylene carbonate is within the above range, which better balances the long cycle life, high RTE, and good safety performance of the energy storage battery.

[0016] In some embodiments, the graphitization degree of the negative electrode film is 81%-92%.

[0017] In this embodiment, the graphitization degree of the negative electrode film is within the above range, which better balances the long cycle life, high RTE and good safety performance of the energy storage battery.

[0018] In some embodiments, the top cover body is provided with an electrode lead-out hole, the electrode terminal includes a body portion and a flange portion, the body portion passes through the electrode lead-out hole, the flange portion protrudes from the outer peripheral surface of the body portion, the flange portion is located inside the top cover body, and along a first direction, at least a portion of the first insulating member is located between the top cover body and the flange portion, the first direction being parallel to the thickness direction of the top cover body; and / or the first insulating member is disposed on the side of the electrode assembly adjacent to the sidewall surface of the housing.

[0019] In this embodiment, the first insulating element is disposed at the aforementioned location, further improving the safety performance of the battery cell.

[0020] In some embodiments, the top cover assembly further includes a second insulating member, at least a portion of which is located between the top cover body and the flange along the first direction, and a first insulating member is in contact with the second insulating member, wherein the melting point of the first insulating member is higher than that of the second insulating member.

[0021] In this embodiment, the melting point of the first insulating component is higher than that of the second insulating component, so that the second insulating component melts before the first insulating component. After the second insulating component melts, it can also insulate and isolate the top cover body from the flange portion, thereby improving the safety performance of the battery cell.

[0022] In some embodiments, the thickness of the first insulating element along the first direction is 0.02 mm to 0.6 mm.

[0023] In this embodiment, the thickness of the first insulating element is within the above-mentioned range, which balances volumetric energy density and safety performance.

[0024] In some embodiments, in the cumulative distribution curve of the sphericity area of ​​the lithium phosphate-containing particles in the cross section along the thickness direction of the positive electrode sheet, the median LA50 of the sphericity of the lithium phosphate-containing particles is 0.60-0.85, and optionally 0.7-0.74.

[0025] The applicant discovered that during the rolling process of high-capacity energy storage batteries, the positive electrode sheets are at risk of wrinkling and breakage due to uneven stress distribution. This is particularly true for the larger tab sizes of high-capacity energy storage batteries, which, during coating, require a wider blank area (corresponding to the tab height after cutting), further exacerbating the uneven stress distribution during rolling. By ensuring that the median sphericity (LA50) of the lithium phosphate particles is within the aforementioned range, balancing the interlocking force and relative slippage ability between particles, the relative slippage between positive electrode active material particles is promoted, resulting in a more uniform stress distribution. This reduces the risk of stress concentration during long cycles, leading to particle breakage and electrode failure, while also balancing the flexibility and stability of the positive electrode film, thus further improving the cycle life of the battery cells.

[0026] In some embodiments, in the cumulative distribution curve of the spheroidal area of ​​the lithium phosphate particles in the cross section along the thickness direction of the positive electrode sheet, the concentration of spheroidal area of ​​the lithium phosphate particles (LA90-LA10) / LA50 is 0.45-0.535.

[0027] The (LA90-LA10) / LA50 ratio reflects not only the sphericity of most particles but also the asymmetry and width of the sphericity distribution within the cathode film. A smaller value indicates a more concentrated distribution. Combined with a high sphericity median, this reflects an overall near-spherical particle shape, which is conducive to close packing, increases interparticle contact, reduces local resistance, improves electron and ion transport efficiency, and further enhances the cycle life and energy efficiency of the battery cell.

[0028] In some embodiments, the median C of the graphitization degree in the cumulative distribution curve of the positive electrode film obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode is... 50 The value is 0.95-1.20, and can be selected as 0.98-1.15, where C 50 IG / ID, where IG represents the Raman spectrum at 1580±100 cm⁻¹. -1 The intensity of peak G at 1350 ± 100 cm⁻¹, where ID represents the Raman spectrum at 1350 ± 100 cm⁻¹. -1 The intensity of peak D at that location.

[0029] The applicant discovered that during the rolling process of large-capacity energy storage batteries, the positive electrode sheets are at risk of wrinkling and breakage due to uneven stress distribution. In particular, the larger size of the matching tabs in large-capacity energy storage batteries leads to a corresponding increase in the width of the blank area reserved for the tabs during coating (corresponding to the tab height after cutting), further exacerbating the problem of uneven stress on the electrode sheets during rolling. By ensuring the graphitization degree of the positive electrode film layer is within the aforementioned range, relative slippage between the positive electrode active material particles is promoted, resulting in a more uniform stress distribution. This reduces the risk of particle breakage and electrode failure due to stress concentration during long-life cycling of the battery cells, further improving the cycle life of the battery cells.

[0030] In some embodiments, the compaction density of the positive electrode film is 2.5 g / cm³. 3 -3g / cm 3 2.5g / cm³ is an option. 3 -2.8g / cm 3 .

[0031] In this embodiment, the compaction density of the positive electrode film is within the above-mentioned range, which further improves the cycle life of the large-capacity energy storage battery under the high energy density design.

[0032] In some embodiments, the thickness of the positive electrode film is 110 μm-230 μm.

[0033] In this embodiment, the thickness of the positive electrode film is within the above-mentioned range, which further improves the cycle life of the large-capacity energy storage battery under the high energy density design.

[0034] In some embodiments, the lithium phosphate particles include one or more of titanium, vanadium, aluminum, and magnesium.

[0035] In this embodiment, doping lithium phosphate with titanium and / or vanadium can stabilize its crystal structure, reduce lattice distortion caused by redox reactions during charging and discharging, thereby improving the structural stability of the positive electrode active material and thus increasing cycle life. Doping lithium phosphate with aluminum and / or magnesium can improve ion conduction pathways, increase lithium-ion diffusion rates, improve the rate performance of the material, reduce the risk of lithium plating in the later stages of cycling, and further improve the cycle life of the battery cell.

[0036] In some embodiments, the lithium phosphate-containing particles include titanium, and the mass content of the titanium is 0.01%-0.3% based on the total mass of the positive electrode active material, optionally 0.05%-0.1%.

[0037] In some embodiments, the lithium phosphate particles include vanadium, and the vanadium content is 0.05%-0.3% by mass, optionally 0.1%-0.2%, based on the total mass of the positive electrode active material.

[0038] In some embodiments, the battery cell includes an electrolyte, the electrolyte includes an additive, the additive includes one or more of vinylene carbonate, fluoroethylene carbonate, silicon-containing additives, and lithium difluorophosphate, wherein the silicon-containing additive includes one or more of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, and trimethylfluorosilane.

[0039] In this embodiment of the application, the cycle life and energy efficiency of the battery cells are further improved by adding the above-mentioned additives.

[0040] In some embodiments, the electrolyte comprises vinylene carbonate, and the mass percentage of vinylene carbonate is 0.5%-8%, optionally 0.6%-4%, based on the mass of the electrolyte.

[0041] In the embodiments of this application, when the content of vinylene carbonate is within the above range, it can effectively improve the interfacial stability of the low graphitization degree negative electrode. Vinylene carbonate is preferentially reduced on the surface of the negative electrode active material, promoting the formation of a dense and uniform SEI, thereby further improving the cycle life and energy efficiency of the battery cell.

[0042] In some embodiments, the electrolyte comprises fluoroethylene carbonate (FEC), and the mass percentage of the fluoroethylene carbonate is 0.1%-10%, optionally 0.1%-0.5%, based on the mass of the electrolyte.

[0043] In this embodiment, fluoroethylene carbonate can form a low-impedance, high-density SEI rich in LiF. When the mass percentage of the fluoroethylene carbonate is within the above range, it further improves the cycle performance and energy efficiency of the battery cell.

[0044] In some embodiments, the electrolyte includes the silicon-containing additive, and the silicon-containing additive accounts for 0.1%-1.5% of the mass of the electrolyte, optionally 0.3%-0.8%.

[0045] In this embodiment, the silicon-containing additive can form a stable interface film with a Si-O or Si-F structure on the electrode surface, reducing interface impedance and suppressing side reactions; when the mass percentage of the silicon-containing polymer is within the above range, it can further improve the cycle performance, energy efficiency and high-temperature stability of the battery cell.

[0046] In some embodiments, the electrolyte comprises lithium difluorophosphate, and the mass percentage of lithium difluorophosphate is 0.1%-1.0%, optionally 0.3%-0.8%, based on the mass of the electrolyte.

[0047] In this embodiment, lithium difluorophosphate can form a dense protective film rich in LiF and phosphate at the positive and negative electrode interfaces. When the mass ratio of lithium difluorophosphate is within the above range, the thermal stability and cycle life of the battery cell can be further improved, and gas generation can be effectively reduced.

[0048] In some embodiments, the electrolyte comprises a lithium-containing electrolyte salt, which includes lithium hexafluorophosphate and lithium difluorosulfonylimide.

[0049] In this embodiment of the application, by using lithium hexafluorophosphate and lithium difluorosulfonylimide together as lithium salts, the cycle life of the battery cell can be further improved.

[0050] In some embodiments, the lithium bisfluorosulfonylimide content is 1%-10% based on the total mass of the electrolyte, optionally 2%-7%.

[0051] In some embodiments, the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is 1-5, and optionally 2-4.

[0052] In the embodiments of this application, when the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is within the above range, the cycle life of the battery cell is further improved.

[0053] In some embodiments, the capacity of the battery cell is greater than or equal to 400Ah, optionally greater than or equal to 500Ah, and further optionally greater than or equal to 600Ah.

[0054] In some embodiments, the capacity of the battery cell is less than or equal to 3000Ah, optionally less than or equal to 1500Ah, and further optionally less than or equal to 1000Ah.

[0055] In some embodiments, the capacity of the battery cell is 500Ah-3000Ah, and optionally 550Ah-700Ah.

[0056] The battery cells provided in this application embodiment have high capacity while having long cycle life and good safety performance.

[0057] In some embodiments, the coating area of ​​the positive electrode film layer included in the battery cell is 11m². 2 -150m 2 11m is optional 2 -120m 2 Further options include 11m. 2 -100m 2 .

[0058] In some embodiments, the first insulating element comprises polyimide.

[0059] Polyimide (PI) has a high melting point and good thermal stability, which can maintain its structural integrity under high temperature conditions, effectively isolate heat conduction, and further improve the safety performance of battery cells.

[0060] In some embodiments, the second insulating element comprises polypropylene.

[0061] Polypropylene (PP) has a relatively low melting point and can melt and close its cells at abnormally high temperatures, thus automatically disconnecting the thermal pathway for protection.

[0062] An embodiment of the second aspect of this application provides a battery device including a battery cell as described in any of the embodiments of the first aspect above.

[0063] An embodiment of the third aspect of this application provides an electrical device, the electrical device including a battery device as described in any of the embodiments of the second aspect above, the battery device being used to provide electrical energy.

[0064] An embodiment of the fourth aspect of this application provides an energy storage device, the energy storage device including a battery device as described in any embodiment of the second aspect above, the battery device being used to store electrical energy.

[0065] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0066] 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.

[0067] Figure 1 is an exploded view of the structure of a single battery cell according to an embodiment of this application;

[0068] Figure 2 is a schematic diagram of the assembly of the top cover body and the electrode terminals according to an embodiment of this application;

[0069] Figure 3 is a magnified view of part A in Figure 2;

[0070] Figure 4 is a schematic diagram of a battery module according to an embodiment of this application;

[0071] Figure 5 is a schematic diagram of a battery pack according to an embodiment of this application;

[0072] Figure 6 is an exploded view of a battery pack according to an embodiment of this application, as shown in Figure 5.

[0073] Explanation of reference numerals in the attached drawings: 1-Battery pack; 2-Upper housing; 3-Lower housing; 4-Battery module; 20-Battery cell; 21-Outer casing; 21a-Housing shell; 21b-Top cover assembly; 211-Top cover body; 211a-Electrode lead-out hole; 22-Electrode terminal; 221-Main body; 222-Flange; 223-Conductive component; 23-Second insulating component; 24-First insulating component; 25-Electrode assembly; 25a-Taper; 5-Battery cell; Z-First direction. Detailed Implementation

[0074] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0075] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0076] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0077] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. In the description of the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0078] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0079] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0080] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0085] Energy storage batteries are primarily used in scenarios requiring long-term energy storage and release, such as working with energy storage power stations to store or release energy in emergencies, and serving roles in grid frequency regulation and emergency backup. Their performance directly impacts the sustainability and reliability of energy storage and release, as well as the overall system efficiency. Practical applications require batteries to maintain efficient and stable energy conversion and release, along with reliable safety assurance, during long-term charging and discharging. However, measures to improve real-time energy efficiency (RTE), such as optimizing charge-discharge strategies or material systems, often accelerate internal side reactions and structural degradation, thereby impairing cycle life and deteriorating safety performance. How to further improve the energy efficiency of individual battery cells while maintaining high cycle stability and safety performance is a pressing technical problem that needs to be solved in this field.

[0086] To address the aforementioned problems, an embodiment of the second aspect of this application provides a battery cell. Referring to FIG1, the battery cell 20 includes a housing 21, an electrode assembly 25, and an electrolyte. The housing 21 includes a shell 21a and a top cover assembly 21b. The shell 21a includes a receiving cavity with an opening. The top cover assembly 21b is configured to cover the opening of the shell 21a and includes a top cover body 211 and electrode terminals 22. The electrolyte includes propylene carbonate, and the mass percentage of propylene carbonate based on the mass of the electrolyte is 1%-15%. The electrode assembly 25 is disposed in the receiving cavity and includes a positive electrode and a negative electrode, wherein the positive electrode includes a positive current collector and a positive electrode disposed on at least one side of the positive current collector. The positive electrode layer includes a positive electrode active material, which includes a lithium phosphate having an olivine structure. The negative electrode includes a negative electrode current collector and a negative electrode film disposed on at least one side of the negative electrode current collector. The negative electrode film includes a negative electrode active material, which includes graphite. The graphitization degree of the negative electrode film is 75%-93%. The battery cell further includes a first insulating member 24, which is disposed between the top cover body 211 and the electrode terminal 22, and / or the first insulating member 24 is disposed between the electrode assembly 25 and the housing 21a (not shown in the figure). The melting point of the first insulating member 24 is greater than or equal to 200°C.

[0087] Adding propylene carbonate (PC) to the electrolyte can effectively improve the energy efficiency (RTE) of a battery cell. Current technology generally suggests that propylene carbonate co-intercalates with lithium ions into the interlayer spacing of the graphite anode active material, causing the graphite layered structure to peel off. Propylene carbonate needs to be paired with highly graphitized graphite to alleviate the co-intercalation problem and improve the cycle life of the battery cell.

[0088] However, the applicant discovered that energy storage batteries differ from general power batteries, requiring extremely high battery life (e.g., over 15,000 cycles, far exceeding the 3,000-5,000 cycles required for power batteries). High-graphitization negative electrode films exhibit significantly increased expansion forces in the later stages of cycling, playing a dominant role in cycle life degradation. Using a low-graphitization negative electrode is necessary to mitigate this expansion and improve cycle life. Furthermore, to adapt to the power grid, energy storage batteries require constant-power charging. Even as capacity decreases in the later stages of cycling, the charging current remains high, effectively increasing the current rate. This leads to increased local overpotential at the negative electrode, making lithium metal deposition more likely and causing cycle life degradation. Propylene carbonate has a high dielectric constant; adding 1%-15% propylene carbonate to the electrolyte not only improves the RTE of the energy storage battery but also reduces the risk of lithium deposition in the later stages of cycling, thus contributing to improved cycle life of individual battery cells.

[0089] While the combination of a low-graphitization negative electrode and 1%-15% propylene carbonate is beneficial for improving the energy efficiency and cycle life of individual energy storage battery cells, under abnormal battery operation conditions such as high temperature, overcharging, or thermal runaway, the side reactions between the low-graphitization graphite and propylene carbonate are more intense. This causes the insulation components (with a melting point of generally 160℃-170℃) typically installed in the battery cell to melt, leading to short circuits and exacerbating thermal runaway. In contrast, the high-melting-point primary insulation component can maintain electrical isolation under abnormal operating conditions, improving battery thermal safety.

[0090] In summary, the embodiments of this application use a negative electrode containing 1%-15% propylene carbonate with a low graphitization degree (75%-93%), and provide a first insulating component with a melting point greater than or equal to 200°C between the top cover body and the electrode terminals, and / or between the electrode assembly and the shell, thereby achieving a balance between high energy efficiency, long cycle life and good thermal safety performance of the energy storage battery, and realizing synergistic optimization of performance and safety.

[0091] In this article, "lithium-containing phosphates with an olivine structure" refers to phosphate materials containing lithium with an olivine crystal structure. As examples, lithium-containing phosphates include, but are not limited to, doped and coated modified materials such as lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt iron phosphate, and lithium nickel iron phosphate.

[0092] In this paper, the term "graphitization degree" refers to an index measuring the degree to which carbon atoms form a close-packed hexagonal graphite crystal structure. It reflects the integrity of the graphite crystal structure in the material, that is, the regularity of the arrangement of carbon atoms in the graphite structure. A low graphitization degree indicates that the graphite spacing is large and there is more disordered structure. Therefore, the material expands less during lithium intercalation, and the disordered structure can disperse local stress.

[0093] In this paper, the "degree of graphitization of the negative electrode film" can be tested using methods known in the art, such as X-ray diffractometer (e.g., Bruker D8 Discover), referring to GB / T 24533-2019. After discharging the battery cell to the discharge cutoff voltage, the battery is disassembled to obtain the negative electrode sheet. An ion beam is used to cut along the thickness direction of the electrode sheet, and the cross-section of the obtained negative electrode film along the thickness direction is scanned to obtain the average interlayer spacing d002 of the (002) crystal plane in the graphite material crystal structure of the negative electrode film. Then, the degree of graphitization is calculated according to the formula g = (0.344 - d002) / (0.344 - 0.3354) × 100%. In the above formula, d002 is the average interlayer spacing of the (002) crystal plane in the graphite material crystal structure expressed in nanometers (nm). As an example, the steps for discharging the battery cell to the discharge cutoff voltage are as follows: the battery is discharged at 25°C with a constant power of 0.125P to the discharge cutoff voltage of 2.5V.

[0094] In some embodiments, the degree of graphitization of the negative electrode film can be selected as 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, or any range between the two.

[0095] In this paper, the types and mass contents of each component in the electrolyte can be obtained by any method known to those skilled in the art. As an example, the composition and content of the electrolyte can be characterized by one or more of the following methods: gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), and gas chromatography-mass spectrometry (GC-MS). For example, referring to GB / T 9722 2023 "General Rules for Gas Chromatography of Chemical Reagents" and / or GB / T 6041 2020 "General Rules for Mass Spectrometry Analysis Methods", gas chromatography and mass spectrometry are coupled. After gas chromatography separates the components in the sample, the components are broken into ion fragments in mass spectrometry and separated according to mass-to-charge ratio (m / z) to form specific mass spectra, obtaining qualitative analysis of each organic component in the electrolyte. Then, the organic components in the electrolyte are separated in the chromatographic column, and detection signal spectra of each component are generated. The retention time is used for component qualitative analysis, and the peak area is corrected by standardization to achieve quantification, obtaining quantitative analysis of the organic components in the electrolyte. Referring to JY / T 020, the types of anions of electrolyte salts in the electrolyte are detected by ion chromatography and quantitatively analyzed. Referring to JY / T 0578 2020, nuclear magnetic resonance spectroscopy (NMR) is used to obtain qualitative and quantitative analysis of the components in the electrolyte.

[0096] The electrolyte referred to in this article can be either fresh electrolyte or electrolyte obtained from the disassembly of a battery cell. The electrolyte obtained from the disassembly of a battery cell can be either the free electrolyte in the battery casing or the electrolyte obtained by centrifugation from the electrodes.

[0097] In some embodiments, based on the mass of the electrolyte, the mass percentage of propylene carbonate can be selected as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any range between the two.

[0098] In this article, "insulating component" refers to a structural part that has electrical insulation properties and can block the flow of current along unintended paths; it is typically made of resin material. As an example, the electrical conductivity of the insulating component is less than or equal to 10. -12 S / cm.

[0099] In this paper, the melting point of the "first insulating component" can be tested using methods known in the art. As an example, differential scanning calorimetry (DSC) can be used, and the test method follows GB / T 19466.3-2004. Take 3-10 mg of the sample to be tested and heat it from room temperature to a temperature range above the target melting point at a rate of 10 °C / min under a nitrogen atmosphere. Record the onset temperature of the main melting peak in the heating curve as the melting point. For insulating component samples from battery disassembly, they can be cleaned with an organic solvent and vacuum dried at 60 °C for 12-24 h before testing.

[0100] In some embodiments, the melting point of the first insulating element may be selected as 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, or any range between the two.

[0101] In some embodiments, the insulating element is one or more of the following: resin film, resin sheet, resin block, resin plate, resin gasket, resin support, resin insert, resin sealing sheet, resin pad, resin liner, and resin protective plate.

[0102] In some embodiments, the melting point of the first insulating element is 200°C-400°C, optionally 260°C-350°C.

[0103] In this embodiment, the melting point of the first insulating element is within the above-mentioned range, which further improves the cycle life and safety performance of the high-capacity energy storage battery.

[0104] In some embodiments, the propylene carbonate accounts for 4%-6% of the total mass.

[0105] In this embodiment, the mass percentage of propylene carbonate is within the above range, which better balances the long cycle life, high RTE, and good safety performance of the energy storage battery.

[0106] In some embodiments, the graphitization degree of the negative electrode film is 81%-92%.

[0107] In this embodiment, the graphitization degree of the negative electrode film is within the above range, which better balances the long cycle life, high RTE and good safety performance of the energy storage battery.

[0108] In some embodiments, referring to Figures 1-3, the top cover body 211 is provided with an electrode lead-out hole 211a, and the electrode terminal 22 includes a main body portion 221 and a flange portion 222. The main body portion 221 passes through the electrode lead-out hole 211a, and the flange portion 222 protrudes from the outer peripheral surface of the main body portion 221. The flange portion 222 is located inside the top cover body 211 along a first direction (Z direction). At least a portion of the first insulating member 24 is located between the top cover body 211 and the flange portion 222. The first direction (Z direction) is parallel to the thickness direction of the top cover body 211; and / or the first insulating member 24 is disposed on the side of the electrode assembly 25 adjacent to the sidewall surface of the housing (not shown in the figures).

[0109] In this embodiment, the first insulating element is disposed at the aforementioned location, further improving the safety performance of the battery cell.

[0110] In some embodiments, referring to Figures 1-3, the top cover assembly 21b further includes a second insulating member 23. Along the first direction (Z direction), at least a portion of the second insulating member 23 is located between the top cover body 211 and the flange portion 222. A first insulating member 24 is in contact with the second insulating member 23, and the melting point of the first insulating member 24 is higher than the melting point of the second insulating member 23.

[0111] In this embodiment, the melting point of the first insulating component is higher than that of the second insulating component, so that the second insulating component melts before the first insulating component. After the second insulating component melts, it can also insulate and isolate the top cover body from the flange portion, thereby improving the safety performance of the battery cell.

[0112] In some embodiments, the thickness of the first insulating element along the first direction is 0.02 mm to 0.6 mm.

[0113] In some embodiments, the thickness of the first insulating element along the first direction can be selected as 0.02 mm, 0.03 mm, 0.05 mm, 0.07 mm, 0.10 mm, 0.12 mm, 0.15 mm, 0.18 mm, 0.20 mm, 0.25 mm, 0.30 mm, 0.35 mm, 0.40 mm, 0.45 mm, 0.50 mm, 0.55 mm, 0.58 mm, 0.60 mm, or any value range between the two.

[0114] In this embodiment, the thickness of the first insulating element is within the above-mentioned range, which balances volumetric energy density and safety performance.

[0115] In some embodiments, in the cumulative distribution curve of the sphericity area of ​​the lithium phosphate-containing particles in the cross section along the thickness direction of the positive electrode sheet, the median LA50 of the sphericity of the lithium phosphate-containing particles is 0.60-0.85, and optionally 0.7-0.74.

[0116] In this application, the term "particle" refers to a particle in the positive electrode film layer that has a recognizable complete boundary in the field of view at a certain magnification, such as 10,000x. Defects and scratches may exist inside the particle, but a complete boundary sufficient to divide the particle cannot be identified inside the particle.

[0117] The identification method for "the lithium phosphate-containing particles" in this paper is as follows: The positive electrode sheet is cut along its thickness direction using an argon ion beam (for example, a Leica EM TIC 3X CP device can be used, operating voltage: 6kV, operating time: 6h). After exposing the cut surface, a scanning electron microscope (for example, a Hitachi SU8230 device can be used, operating voltage: 3kV, beam current: high, probe model: U (LA100), working distance <5mm) is used to observe the cut surface of the positive electrode film along its thickness direction. Images are acquired using a field emission scanning electron microscope at a non-edge location within the cut surface of the positive electrode film (after observing the electrode edge under the scanning electron microscope, the field of view is adjusted to the center of the sample) in secondary electron mode. Electron micrographs are taken at 10kx magnification, and the particles in the electron micrographs are analyzed using ImageJ software (1.46r, win64 version). The specific steps for using ImageJ software are as follows: Load the scanning electron microscope (SEM) image to be analyzed; use the Cellpose plugin to identify particles, and then perform manual corrections; use ImageJ to read and analyze data. The specific method for using the Cellpose plugin to identify particles is as follows: Set the segmentation diameter parameter (diameter in the Segmentation module) to 15 pixels, click "run cyto3" to identify particles; manually mark particles in the image that were not identified by the software, were not fully identified, or were identified incorrectly. Particles that were not identified by the software, were not fully identified, or were identified incorrectly mainly include the following: 1. Particles that are too large or have scratches on their surface, making them unidentifiable or incompletely identifiable; 2. During argon ion beam cutting, scratches may be generated on the particle surface, and the software may misinterpret these scratches as particle boundaries, leading to identification errors; 3. Particles that are too small and were not successfully identified; 4. Particles located at the edge of the SEM field of view, with the particle's interior penetrated by the edge, preventing a complete view of the morphology, resulting in identification errors due to partial identification replacing the whole.For the unidentified or misidentified particles mentioned above, manual calibration is performed as follows: Particles located at the edges of the scanning electron microscope that are not fully displayed are deleted; It is determined whether other unidentified or misidentified particles have internal cracks or scratches. If no cracks or scratches are found, the particle is considered a single particle, and its boundary is manually marked based on observation; If cracks or scratches are found within the particle, it is determined whether the cracks or scratches penetrate the particle. If not, it is considered a single particle and manually marked; If the cracks or scratches penetrate the particle, it is determined whether the cracks or scratches are linear or irregular; If the cracks or scratches are irregular, they are considered the boundary between particles, and particles are divided along this boundary; If the cracks or scratches are linear, contrast is compared; If the contrast is not obvious and there is no crack-like appearance, it is considered a scratch and marked as a single particle; If the contrast is strong and there is a crack-like appearance, it is considered the boundary between particles and marked as two particles. After manual marking, irrelevant information from the automatic image processing is deleted, thus completing the particle identification and marking in the image.

[0118] In this paper, the test method for "sphericity of lithium phosphate particles" is as follows: Images of particles after identification and labeling are imported into ImageJ software for analysis to obtain sphericity. Scale settings are completed based on the scanning electron microscope images. According to the software manual (ImageJ User Guide IJ1.46r), the "Round" parameter obtained from the analysis represents the ratio of the pixel area of ​​the particle to the area of ​​a circle with the fitted major axis as its diameter, and can be used to characterize the sphericity of the particles. The closer the particle is to a sphere, the closer the ratio of the pixel area to the area of ​​the circle with the fitted major axis as its diameter is to 1. Therefore, the "Round" parameter obtained from the analysis is used to characterize the sphericity of the particles.

[0119] The sphericity of at least 5000 particles was arranged in ascending order. A cumulative distribution curve of the sphericity area of ​​the particles in the positive electrode film was obtained, with sphericity as the horizontal axis and cumulative area percentage as the vertical axis. LA50 is the sphericity L-value corresponding to a cumulative area percentage of 50% on the vertical axis of the cumulative distribution curve of sphericity L-value.

[0120] Those skilled in the art can control the sphericity of particles using any known process. For example, the sphericity of particles can be adjusted through processes such as grinding, polishing, chemical etching, mechanical stirring, extrusion, coating, granulation, and adding surfactants, as well as by adjusting the parameters of each process.

[0121] Particles with a median sphericity LA50 within the above range are approximately spherical and are prone to slippage between particles under external force.

[0122] In some embodiments, in the cumulative distribution curve of the sphericity area of ​​the lithium phosphate particles in the cross section along the thickness direction of the positive electrode sheet, the median LA50 of the sphericity of the lithium phosphate particles can be selected as 0.60, 0.62, 0.64, 0.66, 0.68, 0.70, 0.72, 0.74, 0.76, 0.78, 0.80, 0.82, 0.84, 0.85, or any value range between the two.

[0123] The applicant discovered that during the rolling process of high-capacity energy storage batteries, the positive electrode sheets are at risk of wrinkling and breakage due to uneven stress distribution. This is particularly true for the larger tab sizes of high-capacity energy storage batteries, which, during coating, require a wider blank area (corresponding to the tab height after cutting), further exacerbating the uneven stress distribution during rolling. By ensuring that the median sphericity (LA50) of the lithium phosphate particles is within the aforementioned range, balancing the interlocking force and relative slippage ability between particles, the relative slippage between positive electrode active material particles is promoted, resulting in a more uniform stress distribution. This reduces the risk of stress concentration during long cycles, leading to particle breakage and electrode failure, while also balancing the flexibility and stability of the positive electrode film, thus further improving the cycle life of the battery cells.

[0124] In some embodiments, in the cumulative distribution curve of the spheroidal area of ​​the lithium phosphate particles in the cross section along the thickness direction of the positive electrode sheet, the concentration of spheroidal area of ​​the lithium phosphate particles (LA90-LA10) / LA50 is 0.45-0.535.

[0125] In some embodiments, in the cumulative distribution curve of the spheroidal area of ​​the lithium phosphate particles in the cross section along the thickness direction of the positive electrode sheet, the concentration of spheroidal area (LA90-LA10) / LA50 of the lithium phosphate particles can be selected as 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.523, 0.526, 0.528, 0.53, 0.534, 0.535, or any value range between the two.

[0126] In this paper, the test method for "sphericity concentration (LA90-LA10) / LA50" is as follows: Referring to the sphericity test method above, LA90 is the L value corresponding to 90% of the cumulative area on the vertical axis of the cumulative distribution curve of sphericity L value, and LA10 is the L value corresponding to 10% of the cumulative area on the vertical axis of the cumulative distribution curve of sphericity L value. The sphericity concentration is represented by (LA90-LA10) / LA50. (LA90-LA10) / LA50 can reflect not only the sphericity of most particles, but also the asymmetry and width of the sphericity distribution of particles in the positive electrode film layer. The smaller the value, the more concentrated the distribution. Combined with the high sphericity median, it reflects that the particles are approximately spherical overall, which is conducive to the formation of close packing, increases the contact between particles, thereby reducing local resistance, improving electron and ion transport efficiency, and further improving the cycle life and energy efficiency of the battery cell.

[0127] In some embodiments, the median C of the graphitization degree in the cumulative distribution curve of the positive electrode film obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode is... 50 The value is 0.95-1.20, and can be selected as 0.98-1.15, where C 50 IG / ID, where IG represents the Raman spectrum at 1580±100 cm⁻¹. -1 The intensity of peak G at 1350 ± 100 cm⁻¹, where ID represents the Raman spectrum at 1350 ± 100 cm⁻¹. -1 The intensity of peak D at that location.

[0128] In this paper, the graphitization degree C value of the positive electrode film can be obtained by surface scanning mode of a laser confocal Raman spectrometer. As an example, specifically, a laser confocal Raman spectrometer (high-precision Renishaw laser confocal Raman spectrometer) is used, with an excitation wavelength of 532 nm. An appropriate amount of the positive electrode film is taken and surface scanned on its surface or along the thickness direction of the electrode. The scanning area is 45 μm × 45 μm, divided into 10 × 10 grids, with grid vertices as test points, a step size of 5 μm, and a total of 100 scan points. Thus, the C values ​​at different sites and the cumulative distribution curve of the C values ​​in the surface scan area are obtained.

[0129] The graphitization degree C of the positive electrode film was obtained by the ratio of the peak intensities of the G-band and D-band in the Raman spectrum. The position of the G-band peak was 1585±100 cm⁻¹. -1 Its characterization of carbon sp 2 Hybrid structure; D peak position is 1350±50 cm. -1 It characterizes a disordered structure, where disorder refers to the irregular arrangement of carbon atoms within the structure. In graphite crystals, carbon atoms in the same layer arrange themselves in an sp... 2Hybridization forms covalent bonds, while interlayer bonding is facilitated by van der Waals forces, making the carbon in the graphite structure prone to slippage. Therefore, the C value can characterize the degree of graphitization of the positive electrode active material. It is understandable that the degree of graphitization of the lithium phosphate-containing positive electrode active material in this application mainly comes from its surface carbon coating material. Although rich in sp... 2 Hybridized carbon nanotube conductive agents also have relatively high I0 G / I D However, due to its low content and small tube diameter, its addition to the positive electrode film results in an extreme value in the Raman surface scan test of the positive electrode film, and does not affect the graphitization degree C in the positive electrode film. 50 This has an impact. Therefore, the degree of graphitization of the positive electrode film can also be used to characterize the degree of graphitization of the positive electrode active material.

[0130] The cumulative distribution curve of graphitization degree C value refers to the curve obtained by arranging at least 100 C values ​​in ascending order, with graphitization degree as the horizontal axis and the cumulative percentage as the vertical axis. 50 This represents the C value corresponding to a cumulative percentage of 50% on the vertical axis of the cumulative distribution curve of graphitization degree C. The median C value of graphitization degree. 50 Compared to point values, it can reflect the overall graphitization degree of particles in the positive electrode film, i.e., the degree of slippage; compared to the mean value, it can reduce the influence of extreme values ​​during the test and improve the confidence of the test results.

[0131] The higher the degree of graphitization of carbon on the surface of the positive electrode active material, the higher the proportion of graphite-structured carbon in the positive electrode film layer, and the easier it is for particles to slip by means of the highly graphitized carbon structure in the coating material.

[0132] Those skilled in the art can control the degree of graphitization of active material particles using any known process. As an example, adjusting the carbon source (which can be a polymer carbon source, such as PEG), sintering temperature, sintering time, sintering pressure, sintering atmosphere, and nucleation process can all achieve the adjustment of the degree of graphitization of active material particles.

[0133] In some embodiments, the median C of the graphitization degree C in the cumulative distribution curve of the positive electrode film obtained in laser microscopy confocal Raman spectroscopy instrument scanning mode is... 50 The value can be selected from 0.95, 0.96, 0.97, 0.98, 0.984, 0.99, 1, 1.01, 1.012, 1.015, 1.016, 1.02, 1.025, 1.03, 1.032, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11, 1.12, 1.123, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.20, or any value range between the two.

[0134] The applicant discovered that during the rolling process of large-capacity energy storage batteries, the positive electrode sheets are at risk of wrinkling and breakage due to uneven stress distribution. In particular, the larger size of the matching tabs in large-capacity energy storage batteries leads to a corresponding increase in the width of the blank area reserved for the tabs during coating (corresponding to the tab height after cutting), further exacerbating the problem of uneven stress on the electrode sheets during rolling. By ensuring the graphitization degree of the positive electrode film layer is within the aforementioned range, relative slippage between the positive electrode active material particles is promoted, resulting in a more uniform stress distribution. This reduces the risk of particle breakage and electrode failure due to stress concentration during long-life cycling of the battery cells, further improving the cycle life of the battery cells.

[0135] In some embodiments, the compaction density of the positive electrode film is 2.5 g / cm³. 3 -3g / cm 3 2.5g / cm³ is an option. 3 -2.8g / cm 3 .

[0136] In this paper, the compaction density of the positive electrode film can be tested using methods known in the art. As an example, at 25°C, the battery cell is discharged to the discharge cutoff voltage, the battery is disassembled, the positive electrode sheet is obtained, the residual electrolyte is treated with dimethyl carbonate solvent, the electrode sheet is dried, and it is cut into small circular pieces with an area of ​​S, obtaining a mass of W1. The thickness T1 of the positive electrode sheet is measured using a micrometer. Then, the positive electrode film layer of the weighed electrode sheet is wiped off, the mass of the current collector is weighed and recorded as W2, and the thickness T2 of the current collector is measured using a micrometer. The compaction density of the positive electrode film is then calculated as PD = (W1 - W2) / [(T1 - T2) × S]. As an example, the steps for discharging the battery cell to the discharge cutoff voltage are as follows: the battery is discharged at 25°C with a constant power of 0.125P to the discharge cutoff voltage of 2.5V.

[0137] In some embodiments, the compaction density of the positive electrode film may be selected as 2.5 g / cm³. 3 2.55g / cm 3 2.6g / cm 3 2.65g / cm 3 2.7g / cm 3 2.75g / cm 3 2.8g / cm 3 2.85g / cm 3 2.9g / cm 3 2.95g / cm 3 3g / cm 3 , or the range of values ​​between any two.

[0138] In this embodiment, the compaction density of the positive electrode film is within the above-mentioned range, which further improves the cycle life of the large-capacity energy storage battery under the high energy density design.

[0139] In some embodiments, the thickness of the positive electrode film is 110 μm-230 μm.

[0140] In some embodiments, the thickness of the positive electrode film can be selected as 110μm, 115μm, 120μm, 125μm, 130μm, 135μm, 140μm, 145μm, 150μm, 155μm, 160μm, 165μm, 170μm, 175μm, 180μm, 185μm, 190μm, 195μm, 200μm, 205μm, 210μm, 215μm, 220μm, 225μm, 230μm, or any value range between the two.

[0141] In this embodiment, the thickness of the positive electrode film is within the above-mentioned range, which further improves the cycle life of the large-capacity energy storage battery under the high energy density design.

[0142] In some embodiments, the lithium phosphate particles include one or more of titanium, vanadium, aluminum, and magnesium.

[0143] In this embodiment, doping lithium phosphate with titanium and / or vanadium can stabilize its crystal structure, reduce lattice distortion caused by redox reactions during charging and discharging, thereby improving the structural stability of the positive electrode active material and thus increasing cycle life. Doping lithium phosphate with aluminum and / or magnesium can improve ion conduction pathways, increase lithium-ion diffusion rates, improve the rate performance of the material, reduce the risk of lithium plating in the later stages of cycling, and further improve the cycle life of the battery cell.

[0144] In some embodiments, the lithium phosphate-containing particles include titanium, and the mass content of the titanium is 0.01%-0.3% based on the total mass of the positive electrode active material, optionally 0.05%-0.1%.

[0145] In some embodiments, the lithium phosphate-containing particles include titanium, and the mass content of the titanium, based on the total mass of the positive electrode active material, may be selected as 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 0.1%, or any range between the two.

[0146] In some embodiments, the lithium phosphate particles include vanadium, and the vanadium content is 0.05%-0.3% by mass, optionally 0.1%-0.2%, based on the total mass of the positive electrode active material.

[0147] In some embodiments, the lithium phosphate particles include vanadium, and the mass content of the vanadium is optionally 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, or any range between the two, based on the total mass of the positive electrode active material.

[0148] In some embodiments, the battery cell includes an electrolyte, the electrolyte includes an additive, the additive includes one or more of vinylene carbonate, fluoroethylene carbonate, silicon-containing additives, and lithium difluorophosphate, wherein the silicon-containing additive includes one or more of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, and trimethylfluorosilane.

[0149] In this embodiment of the application, the cycle life and energy efficiency of the battery cells are further improved by adding the above-mentioned additives.

[0150] In some embodiments, the electrolyte comprises vinylene carbonate, and the mass percentage of vinylene carbonate is 0.5%-8%, optionally 0.6%-4%, based on the mass of the electrolyte.

[0151] In some embodiments, based on the mass of the electrolyte, the mass percentage of vinylene carbonate (VC) can be selected as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, or any range between the two.

[0152] In the embodiments of this application, when the content of vinylene carbonate is within the above range, it can effectively improve the interfacial stability of the low graphitization degree negative electrode. Vinylene carbonate is preferentially reduced on the surface of the negative electrode active material, promoting the formation of a dense and uniform SEI, thereby further improving the cycle life and energy efficiency of the battery cell.

[0153] In some embodiments, the electrolyte comprises fluoroethylene carbonate (FEC), and the mass percentage of the fluoroethylene carbonate is 0.1%-10%, optionally 0.1%-0.5%, based on the mass of the electrolyte.

[0154] In some embodiments, based on the mass of the electrolyte, the mass percentage of the fluoroethylene carbonate can be selected as 0.05%, 0.1%, 0.25%, 0.5%, 0.75%, 1%, 1.25%, 1.5%, 1.75%, 2%, 2.25%, 2.5%, 2.75%, 3%, 3.25%, 3.5%, 3.75%, 4%, 4.25%, 4.5%, 4.75%, 5%, 5.25%, 5.5%, 5.75%, 6%, 6.25%, 6.5%, 6.75%, 7%, 7.25%, 7.5%, 7.75%, 8%, 8.25%, 8.5%, 8.75%, 9%, 9.25%, 9.5%, 9.75%, 10%, or any range between the two.

[0155] In this embodiment, fluoroethylene carbonate can form a low-impedance, high-density SEI rich in LiF. When the mass percentage of the fluoroethylene carbonate is within the above range, it further improves the cycle performance and energy efficiency of the battery cell.

[0156] In some embodiments, the electrolyte includes the silicon-containing additive, and the silicon-containing additive accounts for 0.1%-1.5% of the mass of the electrolyte, optionally 0.3%-0.8%.

[0157] In some embodiments, the electrolyte includes the silicon-containing additive, and the mass percentage of the silicon-containing additive, based on the mass of the electrolyte, can be selected as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, or any range between the two.

[0158] In this embodiment, the silicon-containing additive can form a stable interface film with a Si-O or Si-F structure on the electrode surface, reducing interface impedance and suppressing side reactions; when the mass percentage of the silicon-containing polymer is within the above range, it can further improve the cycle performance, energy efficiency and high-temperature stability of the battery cell.

[0159] In some embodiments, the electrolyte comprises lithium difluorophosphate, and the mass percentage of lithium difluorophosphate is 0.1%-1.0%, optionally 0.3%-0.8%, based on the mass of the electrolyte.

[0160] In some embodiments, the electrolyte comprises lithium difluorophosphate, and the mass percentage of lithium difluorophosphate, based on the mass of the electrolyte, can be selected as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or any range between the two.

[0161] In this embodiment, lithium difluorophosphate can form a dense protective film rich in LiF and phosphate at the positive and negative electrode interfaces. When the mass ratio of lithium difluorophosphate is within the above range, the thermal stability and cycle life of the battery cell can be further improved, and gas generation can be effectively reduced.

[0162] In some embodiments, the electrolyte comprises a lithium-containing electrolyte salt, which includes lithium hexafluorophosphate and lithium difluorosulfonylimide.

[0163] In this embodiment of the application, by using lithium hexafluorophosphate and lithium difluorosulfonylimide together as lithium salts, the cycle life of the battery cell can be further improved.

[0164] In some embodiments, the lithium bisfluorosulfonylimide content is 1%-10% based on the total mass of the electrolyte, optionally 2%-7%.

[0165] In some embodiments, the mass content of lithium bis(fluorosulfonyl)imide, based on the total mass of the electrolyte, can be selected as 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.6%, 8%, 8.5%, 9%, 9.5%, 10%, or any range between the two.

[0166] In some embodiments, the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is 1-5, and optionally 2-4.

[0167] In some embodiments, the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide can be selected as 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5, or any range between the two.

[0168] In the embodiments of this application, when the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is within the above range, the cycle life of the battery cell is further improved.

[0169] In some embodiments, the capacity of the battery cell is greater than or equal to 400Ah, optionally greater than or equal to 500Ah, and further optionally greater than or equal to 600Ah.

[0170] In some embodiments, the capacity of the battery cell is less than or equal to 3000Ah, optionally less than or equal to 1500Ah, and further optionally less than or equal to 1000Ah.

[0171] In some embodiments, the capacity of the battery cell is 500Ah-3000Ah, and optionally 550Ah-700Ah.

[0172] In this article, the "capacity of a single battery cell" can be tested using methods known in the art. As an example, at 25°C, the battery cell is charged to 3.65V at a constant power of 0.125P and left to stand for 30 minutes; then discharged to 2.5V at a constant power of 0.125P, and the discharge capacity A0 is recorded as the battery capacity, in Ah.

[0173] In some embodiments, the capacity of the battery cell can be selected as 400Ah, 450Ah, 500Ah, 550Ah, 600Ah, 650Ah, 700Ah, 750Ah, 800Ah, 850Ah, 900Ah, 950Ah, 1000Ah, 1100Ah, 1200Ah, 1300Ah, 1400Ah, 1500Ah, 1600Ah, 1700Ah, 1800Ah, 1900Ah, 2000Ah, 2100Ah, 2200Ah, 2300Ah, 2400Ah, 2500Ah, 2600Ah, 2700Ah, 2800Ah, 2900Ah, 3000Ah, or any value range between the two.

[0174] The battery cells provided in this application embodiment have high capacity while having long cycle life and good safety performance.

[0175] In some embodiments, the coating area of ​​the positive electrode film layer included in the battery cell is 11m². 2 -150m 2 11m is optional 2 -120m 2 Further options include 11m. 2 -100m 2 .

[0176] In this article, a single battery cell may include one or more electrode components. "The coating area of ​​the positive electrode film in a single battery cell" refers to the sum of the coating areas of the positive electrode film in all electrode components within the single battery cell. The "coating area" of the positive electrode film is calculated by multiplying the length of the positive electrode active material covering the positive electrode current collector by its width. For double-sided coated positive electrode films, the areas on both sides of the positive electrode film need to be calculated separately and then summed to calculate the total coating area of ​​the positive electrode film.

[0177] In some embodiments, the coating area of ​​the positive electrode film layer included in the battery cell may be 11m². 2 13m 2 15m 2 17m 2 19m2 、21m 2 、23m 2 、25m 2 、27m 2 、29m 2 、31m 2 、33m 2 、35m 2 、37m 2 、39m 2 、41m 2 、43m 2 、45m 2 、47m 2 、49m 2 、51m 2 、53m 2 、55m 2 、57m 2 、59m 2 、61m 2 、63m 2 、65m 2 、67m 2 、69m 2 、71m 2 、73m 2 、75m 2 、77m 2 、79m 2 、81m 2 、83m 2 、85m 2 、87m 2 、89m 2 、91m 2 、93m 2 、95m 2 、97m 2 、99m 2 、101m 2 、103m 2 、105m 2 、107m 2 、109m 2 、111m 2 、113m 2 、115m 2 、117m 2 、119m 2 、121m 2 、123m 2 、125m 2 、127m 2 、129m 2 、131m 2 、133m 2135m 2 137m 2 139m 2 141m 2 143m 2 145m 2 147m 2 149m 2 150m 2 , or a range of values ​​between any two.

[0178] In some embodiments, the first insulating element comprises polyimide.

[0179] Polyimide (PI) has a high melting point and good thermal stability, which can maintain its structural integrity under high temperature conditions, effectively isolate heat conduction, and further improve the safety performance of battery cells.

[0180] In some embodiments, the second insulating element comprises polypropylene.

[0181] Polypropylene (PP) has a relatively low melting point and can melt and close its cells at abnormally high temperatures, thus automatically disconnecting the thermal pathway for protection.

[0182] An embodiment of the second aspect of this application provides a battery device including a battery cell as described in any of the embodiments of the first aspect above.

[0183] An embodiment of the third aspect of this application provides an electrical device, the electrical device including a battery device as described in any of the embodiments of the second aspect above, the battery device being used to provide electrical energy.

[0184] An embodiment of the fourth aspect of this application provides an energy storage device, the energy storage device including a battery device as described in any embodiment of the second aspect above, the battery device being used to store electrical energy.

[0185] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0186] [Positive electrode plate]

[0187] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

[0188] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0189] 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.).

[0190] In some embodiments, examples of lithium phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0191] 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.

[0192] 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.

[0193] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0194] [Negative electrode plate]

[0195] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0196] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0197] 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.).

[0198] In some embodiments, the negative electrode film layer may optionally include a binder. The binder 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).

[0199] 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.

[0200] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0201] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0202] [Electrolytes]

[0203] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0204] 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.

[0205] [Isolation membrane]

[0206] In some embodiments, the battery cell also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0207] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0208] The embodiments of this application do not impose any particular restrictions on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape.

[0209] In some embodiments, referring to FIG1, the housing may include a housing 21 and an electrode assembly 25. The housing 21 includes a shell 21a and a cover assembly 21b. The shell 21a and the cover assembly 21b enclose a receiving cavity. The shell 21a has an opening communicating with the receiving cavity, and the cover assembly 21b is capable of covering the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator may be formed into the electrode assembly 25 through a winding process or a stacking process. The electrode assembly 25 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 25. The number of electrode assemblies 25 contained in the battery cell 20 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0210] This application also provides a battery device, which includes the battery cell provided in this application. In some embodiments, the battery device is one or more of a battery module and a battery pack.

[0211] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0212] Figure 4 shows a battery module 4 as an example. Referring to Figure 4, in the battery module 4, multiple battery cells 20 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 20 can be fixed in place using fasteners.

[0213] 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 one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0214] As an example, a battery pack may include a battery box and multiple battery modules disposed within the battery box. The battery box includes an upper body and a lower body, the upper body covering the lower body to form a closed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0215] Figures 5 and 6 show a battery pack 1 as an example. Referring to Figures 5 and 6, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0216] This application also provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack provided in this application. The battery cell, battery module, or battery pack serves as the energy storage unit of the electrical device.

[0217] As the electrical device, a single battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0218] 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.

[0219] I. Implementation Examples

[0220] Example 1

[0221] (1) Preparation of positive electrode sheet

[0222] Preparation of positive electrode active materials:

[0223] Lithium dihydrogen phosphate, ferrous oxalate, polyethylene glycol, and titanium dioxide were mixed evenly in methanol and then ground to obtain a mixed raw material. The ratio of lithium dihydrogen phosphate to ferrous oxalate resulted in an atomic molar ratio of lithium to iron of 1.03.

[0224] The spray-dried slurry yields a dried precursor powder, which is light yellow in appearance and uniform in color.

[0225] The precursor powder was placed in a sintering furnace and heated from 25°C to 350°C at a rate of 2°C / min under a nitrogen atmosphere and held at that temperature for 3 hours. Then, the temperature was increased to a second temperature of 770°C at a rate of 5°C / min and held at that temperature for 10 hours. After the process, the temperature was lowered and cooled.

[0226] The obtained material was crushed using an airflow pulverization method with a staged frequency of 22Hz and a pulverizing airflow of 0.55MPa to obtain carbon-coated lithium iron phosphate cathode active material.

[0227] The prepared positive electrode active material has a carbon content of 1.177% by mass, a lithium iron antisite defect concentration of 0.53%, and a powder tap density of 1.19 g / cm³. 3 The compacted density of the powder under 3T pressure is 2.57 g / cm³. 3 The powder resistivity at 8 MPa is 6.3 Ω·cm; the discharge capacity at a 1C discharge rate is 142.3 mAh / g; there is a discharge plateau in the voltage range of 2.5V to 2.9V, and the discharge capacity of the 3.2V discharge plateau accounts for 92.1%.

[0228] The above-mentioned positive electrode active materials, lithium iron phosphate, carbon nanotubes, conductive carbon black, polyvinylidene fluoride, and lithium carboxymethyl cellulose, were mixed in a mass ratio of 97:0.3:2:0.5:0.2, and then N-methylpyrrolidone solvent was added and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry was transferred and coated onto a current collector aluminum foil, dried, hot-pressed, die-cut, and slit to obtain the positive electrode sheet.

[0229] (2) Preparation of negative electrode sheet

[0230] A negative electrode slurry was prepared by mixing graphite (anode active material), carbon nanotubes (conductive agent), styrene-butadiene rubber (binder), and sodium carboxymethyl cellulose (thickener) in a ratio of 98:0.3:1:0.7 with deionized water and stirring. The slurry was then coated onto both sides of a copper foil. After coating both sides, the foil was dried, compacted, slit, and sheeted to obtain the negative electrode sheet.

[0231] (3) Separating membrane

[0232] A polyethylene film with a thickness of 5 μm was used as the base film, and both sides of the base film were coated with a coating containing alumina ceramic particles and polyvinylidene fluoride.

[0233] (4) Preparation of electrolyte

[0234] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and fluoroethylene carbonate (FEC) were mixed evenly in a mass ratio of 30:30:31:5:4, and 3% lithium bis(fluorosulfonyl)imide (LiFSI) and 9% lithium hexafluorophosphate (LiPF6) were added.

[0235] Based on the total mass of the electrolyte, the mass percentages of each component are as follows: DMC 26.4%, EMC 26.4%, EC 27.28%, PC 4.4%, FEC 3.52% (DMC:EMC:EC:PC:FEC = 30:30:31:5:4), LiFSI 3%, and LiPF6 9%.

[0236] 5) Preparation of battery cells

[0237] The positive electrode, separator, and negative electrode are stacked in sequence. The separator must be able to isolate the anode and cathode. The bare cell is obtained by winding. The bare cell is placed in the outer packaging, electrolyte is injected, and after processes such as encapsulation, formation, and degassing, a lithium-ion battery is finally obtained.

[0238] Battery disassembly and testing revealed:

[0239] The battery cell has a capacity of 532 Ah and a volumetric energy density of 401 Wh / L; the positive electrode film has a compaction density of 2.65 g / cm³. 3 The thickness of the positive electrode film is 162 μm, and the coating area of ​​the positive electrode active material is 16 m². 2 The median C of the graphitization degree C in the cumulative distribution curve of the positive electrode film obtained by laser microscopy confocal Raman spectroscopy instrument scanning mode is... 50 The median LA50 of the sphericity of lithium phosphate particles is 0.7; the concentration of sphericity of lithium phosphate particles (LA90-LA10) / LA50 is 0.45; and the graphitization degree of the negative electrode film is 83%. A first insulating element (polyimide) is disposed between the top cover body and the flange, and on the side of the electrode assembly adjacent to the housing sidewall. A second insulating element (polypropylene) is disposed between the top cover body and the flange, and contacts the first insulating element.

[0240] Examples 2-3 and Comparative Example 1

[0241] The battery cells of Examples 2-3 and Comparative Example 1 are similar to those of Example 1, except for the arrangement of the first insulating element, as shown in Table 1 below.

[0242] Example 4

[0243] The battery cell in Example 4 is similar to that in Example 1, except that the size of the battery cell is different. The coating area of ​​the positive electrode film in the battery cell of Example 4 is 35m². 2 .

[0244] Examples 5-8 and Comparative Example 2

[0245] The battery cells of Examples 5-8 and Comparative Example 2 are similar to those of Example 1, except that the degree of graphitization of the negative electrode film is different, as shown in Table 2 below.

[0246] Examples 9-20

[0247] The battery cells of Examples 9-20 are similar to those of Example 1, except that the electrolytes are different, as shown in Table 3 below.

[0248] Examples 21-24

[0249] The battery cells in Examples 21-24 are similar to those in Example 1, except that the positive electrode active material is different, as shown in Table 4 below.

[0250] II. Battery Performance Testing

[0251] (1) Battery cycle performance test

[0252] The constant power cycling capacity retention was tested in steps (i) and (ii) at 25°C.

[0253] (i) Initial capacity calibration

[0254] a. Charge at a constant power of 0.5P to the upper limit voltage (3.65V); let stand for 10 minutes.

[0255] b. Discharge at a constant power of 0.5P to the lower limit voltage (2.5V) and record the discharge capacity Q0; repeat 3 times and take the average value as the reference capacity, with a deviation ≤2%.

[0256] (ii) Formal Cycle

[0257] a. Let stand for 5-10 minutes.

[0258] b. 0.5P constant power charging to the upper limit voltage (3.65V).

[0259] c. Let stand for 5 minutes.

[0260] d. Constant power discharge: 0.5P constant power discharge to the lower limit voltage (2.5V).

[0261] e. Return to step a and repeat the process.

[0262] Loop termination condition

[0263] Once the target number of cycles (7000) is reached, record the discharge capacity Q of the last cycle. n .

[0264] Cyclic capacity retention rate = (Q n / Q0)×100%

[0265] (2) Battery capacity and volumetric energy density testing

[0266] At 25℃, the battery cell is charged to 3.65V at a constant power of 0.125P and left to stand for 30 minutes; then discharged to 2.5V at a constant power of 0.125P, and the discharge capacity A0 at this point is recorded as the battery capacity in Ah. At the same time, the discharge energy E is recorded in Wh. The length, width, and height of the battery cell are measured with calipers, and the volume of the battery cell V0 is calculated in L. The volumetric energy density of the battery cell VED = E / V0 in Wh / L.

[0267] (3) Energy efficiency (RTE) test

[0268] At 25℃, the battery cells were discharged at a constant power of 0.125P until the voltage of the battery cells reached 2.5V, and then allowed to stand for 30 minutes. Next, the battery cells were charged and discharged at a constant power of 0.125P: the battery cells were charged to 3.65V at a constant power of 0.125P, and the charging voltage-charging capacity curve was recorded; after standing for 30 minutes, they were discharged to 2.5V at a constant power of 0.25P, and the discharging voltage-discharging capacity curve was recorded.

[0269] In the charging voltage-charging capacity curve, the charging energy W1 is obtained by integrating the charging voltage relative to the charging capacity in the range of 2.5V to 3.65V; in the discharging voltage-discharging capacity curve, the discharging energy W2 is obtained by integrating the discharging voltage relative to the discharging capacity in the range of 2.5V to 3.65V; RTE = W2 / W1 × 100%.

[0270] (4) Safety performance test

[0271] According to UL 9540A:2019 "Test Method for Thermal Runaway Fire Propagation in Battery Energy Storage Systems", after thermal runaway of a single battery cell is triggered, the highest surface temperature T1 of adjacent battery cells is measured.

[0272] According to UL 9540A:2019 "Test method for thermal runaway fire propagation in battery energy storage systems", the battery cells were heated and the temperature T2 when the explosion-proof valve of the battery cell was opened was tested.

[0273] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0274] The parameters of the battery cells prepared in Examples 1-24 and Comparative Examples 1-3 were tested according to the methods described herein, and the results are shown in Tables 1-4 below.

[0275] This application provides a battery cell, including a casing, an electrode assembly, and an electrolyte. The casing includes a housing and a top cover assembly. The housing includes a receiving cavity with an opening. The top cover assembly is configured to cover the opening of the housing and includes a top cover body and electrode terminals. The electrolyte includes propylene carbonate, and based on the mass of the electrolyte, the mass percentage of propylene carbonate is 1%-15%. The electrode assembly is disposed in the receiving cavity and includes a positive electrode and a negative electrode. The positive electrode includes a positive current collector and a positive electrode film disposed on at least one side of the positive current collector. The positive electrode film includes a positive active electrode. The materials include a positive electrode active material comprising a lithium phosphate with an olivine structure, and a negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector. The negative electrode film layer comprises a negative electrode active material, which includes graphite, and the graphitization degree of the negative electrode film layer is 75%-93%. The battery cell further includes a first insulating component disposed between the top cover body and the electrode terminals, and / or between the electrode assembly and the housing. The melting point of the first insulating component is greater than or equal to 200°C. Through the above technical solution, a balance is achieved between high energy efficiency, long cycle life, and good thermal safety performance in the energy storage battery, realizing synergistic optimization of performance and safety.

[0276] Table 1

[0277] Table 2

[0278] Table 3

[0279] According to Tables 1-3 above, comparing Examples 1-20 with Comparative Examples 1-3, it can be seen that when the mass percentage of propylene carbonate is 1%-15%, the graphitization degree of the negative electrode film is 75%-93%, the battery cell also includes a first insulating component, the first insulating component is disposed between the top cover body and the electrode terminal, and / or the first insulating component is disposed between the electrode assembly and the housing, and the melting point of the first insulating component is greater than or equal to 200°C, the energy storage battery can achieve a balance of high energy efficiency, long cycle life and good thermal safety performance.

[0280] According to Table 1 above, comparing Embodiment 1 with Embodiments 2-3, it can be seen that the first insulating element is simultaneously disposed between the top cover body and the electrode terminal, and between the electrode assembly and the housing, which further improves the safety performance of the battery cell.

[0281] According to Table 2 above, comparing Examples 1 and 6-7 with Examples 5 and 8, it can be seen that when the graphitization degree of the negative electrode film is 81%-92%, the battery cell can achieve a better balance between increased capacity, long cycle life, and good safety performance.

[0282] As shown in Table 3 above, when the mass percentage of lithium difluorosulfonylimide is 1%-10%, the battery cell has both good safety performance and cycle performance.

[0283] According to Table 3 above, comparing Examples 1 and 10-13 with Example 9, it can be seen that when the mass percentage of lithium difluorosulfonylimide is 2%-7%, the cycle performance of the battery cell is further improved.

[0284] According to Table 3 above, comparing Example 14 with Example 1 and Examples 15-17, it can be seen that when the mass percentage of fluoroethylene carbonate (FEC) is 0.1%-0.5%, the mass percentage of tris(trimethylsilyl)phosphate (TMSP) is 0.3%-0.8%, and the mass percentage of lithium difluorophosphate (LiPO2F2) is 0.3%-0.8%, the safety performance and cycle performance of the battery cell are further improved simultaneously.

[0285] According to Table 3 above, comparing Examples 1 and 19 with Examples 18 and 20, it can be seen that when the mass percentage of propylene carbonate (PC) is 4%-6%, the energy storage battery better balances high energy efficiency, long cycle life, and good safety performance.

[0286] Table 4

[0287] According to Table 4 above, comparing Example 1 with Examples 21-24, it can be seen that when the median graphitization degree C50 of the positive electrode film is 0.98-1.15 and the concentration of spheroidal density of lithium phosphate particles (LA90-LA10) / LA50 is 0.45-0.535, the cycle performance of the battery cell is further improved.

[0288] 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

A battery cell, characterized in that, include: Casing, electrode assembly, and electrolyte, The outer casing includes a housing and a top cover assembly. The housing includes a receiving cavity with an opening. The top cover assembly is configured to cover the opening of the housing and includes a top cover body and electrode terminals. The electrolyte includes propylene carbonate, and the mass percentage of propylene carbonate based on the mass of the electrolyte is 1%-15%. The electrode assembly is disposed in the receiving cavity and includes a positive electrode and a negative electrode. The positive electrode includes a positive current collector and a positive electrode film disposed on at least one side of the positive current collector. The positive electrode film includes a positive active material, which includes a lithium phosphate having an olivine structure. The negative electrode includes a negative current collector and a negative electrode film disposed on at least one side of the negative current collector. The negative electrode film includes a negative active material, which includes graphite. The graphitization degree of the negative electrode film is 75%-93%. The battery cell further includes a first insulating member, which is disposed between the top cover body and the electrode terminals, and / or between the electrode assembly and the housing. The melting point of the first insulating member is greater than or equal to 200°C. The battery cell according to claim 1 is characterized in that, The melting point of the first insulating component is 200℃-400℃, and can be selected as 260℃-350℃. The battery cell according to claim 1 or 2 is characterized in that, The propylene carbonate content is 4%-6% by mass. The battery cell according to any one of claims 1 to 3 is characterized in that, The graphitization degree of the negative electrode film is 81%-92%. The battery cell according to any one of claims 1 to 4 is characterized in that, The top cover body is provided with an electrode lead-out hole. The electrode terminal includes a main body and a flange. The main body passes through the electrode lead-out hole. The flange protrudes from the outer peripheral surface of the main body and is located inside the top cover body. Along a first direction, at least a portion of the first insulating member is located between the top cover body and the flange. The first direction is parallel to the thickness direction of the top cover body. And / or the first insulating member is disposed on the side of the electrode assembly adjacent to the side wall surface of the housing. The battery cell according to any one of claims 1 to 5 is characterized in that, The top cover assembly further includes a second insulating member, at least a portion of which is located between the top cover body and the flange along the first direction. The first insulating member is in contact with the second insulating member, and the melting point of the first insulating member is higher than that of the second insulating member. The battery cell according to any one of claims 1 to 6 is characterized in that, Along the first direction, the thickness of the first insulating element is 0.02mm-0.6mm. The battery cell according to any one of claims 1 to 7 is characterized in that, In the cumulative distribution curve of the sphericity area of ​​the lithium phosphate particles in the cross section along the thickness direction of the positive electrode sheet, the median LA50 of the sphericity of the lithium phosphate particles is 0.60-0.85, and can be selected as 0.7-0.

74. The battery cell according to any one of claims 1 to 8 is characterized in that, In the cumulative distribution curve of graphitization degree obtained by laser microscopy confocal Raman spectroscopy in instrument scanning mode, the median C of the graphitization degree is... 50 The value is 0.95-1.20, and can be selected as 0.98-1.15, where C 50 IG / ID, where IG represents the Raman spectrum at 1580±100 cm⁻¹. -1 The intensity of peak G at 1350 ± 100 cm⁻¹, where ID represents the Raman spectrum at 1350 ± 100 cm⁻¹. -1 The intensity of peak D at that location. The battery cell according to any one of claims 1 to 9 is characterized in that, The compaction density of the positive electrode film is 2.5 g / cm³. 3 -3g / cm 3 2.5g / cm³ is an option. 3 -2.8g / cm 3 . The battery cell according to any one of claims 1 to 10 is characterized in that, The thickness of the positive electrode film is 110μm-230μm. The battery cell according to any one of claims 1 to 11 is characterized in that, The lithium phosphate particles include one or more of the following elements: titanium, vanadium, aluminum, and magnesium. The battery cell according to any one of claims 1 to 12 is characterized in that, The lithium phosphate particles include titanium, and the mass content of the titanium is 0.01%-0.3% based on the total mass of the positive electrode active material, optionally 0.05%-0.1%. The battery cell according to any one of claims 1 to 13 is characterized in that, The lithium phosphate particles include vanadium, and the vanadium content is 0.05%-0.3% by mass, optionally 0.1%-0.2%, based on the total mass of the positive electrode active material. The battery cell according to any one of claims 1 to 14 is characterized in that, The battery cell includes an electrolyte, and the electrolyte includes additives, which include one or more of vinylene carbonate, fluoroethylene carbonate, silicon-containing additives, and lithium difluorophosphate, wherein the silicon-containing additives include one or more of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, and trimethylfluorosilane. The battery cell according to claim 15 is characterized in that, The electrolyte includes vinylene carbonate, and the mass percentage of vinylene carbonate is 0.5%-8%, optionally 0.6%-4%, based on the mass of the electrolyte. The battery cell according to claim 15 or 16 is characterized in that, The electrolyte includes fluoroethylene carbonate (FEC), and the mass percentage of the fluoroethylene carbonate is 0.1%-10%, optionally 0.1%-0.5%, based on the mass of the electrolyte. The battery cell according to any one of claims 15 to 17 is characterized in that, The electrolyte includes the silicon-containing additive, and the silicon-containing additive accounts for 0.1%-1.5% of the mass of the electrolyte, optionally 0.3%-0.8%. The battery cell according to any one of claims 15 to 18 is characterized in that, The electrolyte includes lithium difluorophosphate, and the mass percentage of lithium difluorophosphate is 0.1%-1.0%, optionally 0.3%-0.8%, based on the mass of the electrolyte. The battery cell according to any one of claims 1 to 19 is characterized in that, The electrolyte includes a lithium-containing electrolyte salt, which includes lithium hexafluorophosphate and lithium difluorosulfonylimide. The battery cell according to claim 20 is characterized in that, Based on the total mass of the electrolyte, the mass content of the lithium bis(fluorosulfonyl)imide is 1%-10%, optionally 2%-7%. The battery cell according to claim 20 or 21 is characterized in that, The mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is 1-5, and can be selected as 2-4. The battery cell according to any one of claims 1 to 22 is characterized in that, The capacity of the battery cell is greater than or equal to 400Ah, optionally greater than or equal to 500Ah, and further optionally greater than or equal to 600Ah. The battery cell according to any one of claims 1 to 23 is characterized in that, The capacity of the battery cell is less than or equal to 3000Ah, optionally less than or equal to 1500Ah, and further optionally less than or equal to 1000Ah. The battery cell according to any one of claims 1 to 24 is characterized in that, The capacity of the battery cell is 500Ah-3000Ah, and can be selected as 550Ah-700Ah. The battery cell according to any one of claims 1 to 25 is characterized in that, The coating area of ​​the positive electrode film layer contained in the battery cell is 11m². 2 -150m 2 11m is optional 2 -120m 2 Further options include 11m. 2 -100m 2 . The battery cell according to any one of claims 1 to 26 is characterized in that, The first insulating element comprises polyimide. The battery cell according to any one of claims 1 to 27 is characterized in that, The second insulating element comprises polypropylene. A battery device, characterized in that, Includes the battery cell as described in any one of claims 1 to 28. An electrical device, characterized in that, The electrical device includes the battery device as described in claim 29, the battery device being used to provide electrical energy. An energy storage device, characterized in that, The energy storage device includes the battery device as described in claim 29, the battery device being used to store electrical energy.

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