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 an electrode assembly and an electrolyte. The electrode assembly comprises a positive electrode sheet. The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector. The positive electrode film layer comprises a positive electrode active material and an additive. The compaction density of the positive electrode film layer is 2.4 g / cm3 to 3.0 g / cm3. The additive comprises one or more of lithium carbonate, a transition metal metallocene, a polypyridine-transition metal complex, and thianthrene and a derivative thereof. The electrolyte comprises dimethyl carbonate. Based on the total mass of the electrolyte, the mass content of the dimethyl carbonate is 15% to 80%.

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 / 085988, 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”, which is hereby incorporated by reference.

[0003] This application incorporates, in its entirety, patent application number PCT / CN2025 / 140513, 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, and in particular to a battery cell, battery device, power supply device, and 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 indicators for evaluating the performance of energy storage batteries. This is especially true for large-scale energy storage power stations, whose large-scale, long-term operation places higher demands on battery cycle life. 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 and long cycle life. Summary of the Invention

[0006] This application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell with high capacity and good cycle performance.

[0007] An embodiment of the first aspect of this application provides a battery cell, the battery cell including an electrode assembly and an electrolyte, the electrode assembly including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer including a positive electrode active material and additives, and the compaction density of the positive electrode film layer being 2.4 g / cm³. 3 -2.9g / cm 3 The additives include one or more of lithium carbonate, transition metal cyclohexane, polypyridine-transition metal complex, thiazoline and its derivatives, and the electrolyte includes dimethyl carbonate, wherein the mass content of dimethyl carbonate is 15%-80% based on the total mass of the electrolyte.

[0008] Unlike power batteries, energy storage batteries need to operate in conjunction with power station systems to meet the requirements of constant power charging. This means that the charging current of an energy storage battery does not decrease as its capacity decays throughout its entire lifespan. Power batteries, on the other hand, are typically charged at a constant rate, meaning the charging current is adapted to the battery capacity. As the capacity of individual battery cells decreases during use, the charging current of the power battery also decreases accordingly. This fundamental difference forces energy storage batteries to withstand higher charging rates after capacity decay, leading to uneven current density distribution within individual battery cells, lithium plating, and a deterioration in the cycle life of individual battery cells. Furthermore, because power station systems continuously supply power, the charging voltage of individual battery cells in the battery module is prone to exceeding their charging cut-off voltage, i.e., overcharging. This is detrimental to the long-term safe and stable operation of energy storage batteries, limiting further improvements in their safety performance and cycle life.

[0009] The applicant's research found that adding additives such as lithium carbonate, transition metal cyclohexane, polypyridine-transition metal complex, thiamethoxam and its derivatives to the high-density positive electrode film can preferentially decompose and undergo redox reactions when the monomer is overcharged, inhibiting the occurrence of heat-generating chain reactions during overcharging, thereby improving the overcharge safety performance of the energy storage battery module and enhancing the cycle life and safety performance of the energy storage battery module.

[0010] However, research shows that compared to the positive electrode active material in the positive electrode film, additives such as lithium carbonate have poorer ionic and electronic conductivity. Although they can improve the safety performance of energy storage batteries, they increase the impedance of the high-density positive electrode sheet, worsen its kinetic performance, further deteriorate the uniformity of the current density distribution in the positive electrode film, induce concentration polarization within the battery, and easily cause a performance drop after long-cycle charging under constant power conditions, thus limiting further improvements in the cycle life of energy storage batteries. Further research by the applicant found that dimethyl carbonate has a short linear carbon chain in its molecular structure, resulting in lower viscosity. Adding 15%-50% dimethyl carbonate to the electrolyte helps reduce the overall viscosity of the electrolyte, improves the wettability of the electrolyte under high-density conditions, helps improve the lithium-ion transport efficiency in the positive electrode sheet, improves the impedance of the positive electrode sheet and the uniformity of the current density distribution in the positive electrode film, reduces concentration polarization, and thus further improves the cycle life of energy storage batteries.

[0011] In any embodiment, the mass content of dimethyl carbonate is 15%-50% based on the total mass of the electrolyte.

[0012] In any embodiment, the mass content of the additive is 0.1%-5% based on the total mass of the positive electrode film.

[0013] In any embodiment, the mass content of the additive is 0.5%-3% based on the total mass of the positive electrode film.

[0014] When the mass content of additives in the high-density positive electrode film meets the above range, it can improve the safety performance of the energy storage battery while reducing the space occupied by the active material in the positive electrode film and the deterioration of the uniformity of the current density distribution in the positive electrode film, thus improving the capacity and cycle life of the battery cells.

[0015] In any embodiment, the coating area of ​​the positive electrode film in the battery cell is 11m². 2 -150m 2 .

[0016] In any embodiment, the coating area of ​​the positive electrode film in the battery cell is 11m². 2 -120m 2 In any embodiment, the coating area of ​​the positive electrode film in the battery cell is 11m². 2 -100m 2 .

[0017] In any embodiment, the capacity of the battery cell is greater than or equal to 400Ah.

[0018] In any embodiment, the capacity of the battery cell is 400Ah-3000Ah. In any embodiment, the capacity of the battery cell is 500Ah-1500Ah. In any embodiment, the capacity of the battery cell is 600Ah-1000Ah.

[0019] In any embodiment, the dimension of the battery cell along the first direction is T, the dimension of the battery cell along the second direction is H, and the dimension of the battery cell along the third direction is L, where 50mm≤T≤100mm, 200mm≤H≤240mm, and 250mm≤L≤350mm, and the first direction, the second direction, and the third direction are perpendicular to each other.

[0020] In any embodiment, the dimension T of the battery cell along the first direction satisfies 60mm≤T≤90mm.

[0021] In any embodiment, the dimension H of the battery cell along the second direction satisfies 210mm≤H≤230mm.

[0022] In any embodiment, the dimension L of the battery cell along a third direction satisfies 260mm≤L≤290mm.

[0023] Large-size, high-capacity battery cells have a high active material load, which helps meet the high-capacity requirements of energy storage power systems. However, large-size, high-capacity battery cells are prone to lithium plating and heat accumulation when overcharged, posing a high risk of triggering a thermal runaway chain, which is detrimental to improving the safety performance and cycle life of energy storage battery module systems. The technical solution provided in this application is particularly suitable for large-size, high-capacity battery cells, and can effectively improve the safety performance of the high-density positive electrode film in large-size, high-capacity battery cells during overcharge, further improving the safety performance and cycle life of energy storage batteries.

[0024] In any implementation, the second direction is parallel to the direction of gravity.

[0025] The second direction is parallel to the direction of gravity of the battery cell in use. It can be understood that when the energy storage device is placed on a horizontal surface, the direction of gravity of the battery cell is parallel to the first direction, which is parallel to the height direction of the battery cell when it is loaded into the energy storage device.

[0026] In any embodiment, the positive electrode film layer includes a one-dimensional conductive agent, and the mass content of the one-dimensional conductive agent is 0.1%-2% based on the total mass of the positive electrode film layer.

[0027] The applicant's research found that the positive electrode film contains a one-dimensional conductive agent, which can form a linearly intersecting mesh conductive network inside the positive electrode film. This is beneficial to improving the conductivity of the positive electrode sheet, improving the uniformity of current distribution in the high-density positive electrode film containing additives such as lithium carbonate, and simultaneously improving the safety and cycle performance of the battery cell.

[0028] In any embodiment, the mass content of the one-dimensional conductive agent is 0.2%-1% based on the total mass of the positive electrode film.

[0029] The content of one-dimensional conductive agent in the positive electrode film layer within the above range can effectively reduce the excessive space occupied by the one-dimensional conductive agent in the positive electrode active material, while improving the battery's capacity, safety performance and cycle performance.

[0030] In any embodiment, the specific surface area of ​​the one-dimensional conductive agent is 100 m². 2 / g-220m 2 / g.

[0031] In any embodiment, the oil absorption value of the one-dimensional conductive agent is 100mL / 100g-200mL / 100g.

[0032] The fact that the specific surface area and oil absorption value of the one-dimensional conductive agent meet the above range indicates that the one-dimensional conductive agent has a suitable pore structure, which effectively reduces the probability of the one-dimensional conductive agent agglomerating and entangled in the positive electrode film, thereby forming a good conductive network. This is beneficial to improving the conductivity of the positive electrode sheet, improving the current distribution in the high-density positive electrode film, and further improving the cycle performance of the battery cell.

[0033] In any embodiment, the powder resistivity of the one-dimensional conductive agent is less than or equal to 50 mΩ·cm.

[0034] The resistivity of the one-dimensional conductive agent powder meets the above range, which is beneficial to improve the conductivity of the positive electrode sheet, thereby improving the uniformity of the current density distribution in the high-density positive electrode film and improving the cycle performance of the battery cell.

[0035] In any embodiment, the one-dimensional conductive agent includes one or more of single-arm carbon nanotubes, multi-arm carbon nanotubes, and carbon nanofibers.

[0036] The positive electrode film includes the above-mentioned types that can form a good conductive network in the high-density positive electrode film, thereby improving the conductivity of the positive electrode sheet and the cycle performance of the energy storage battery cell.

[0037] In any embodiment, the electrolyte comprises a first cyclic carbonate, which comprises one or more of fluoroethylene carbonate and vinylene carbonate.

[0038] The applicant's research indicates that the conductive network formed by the one-dimensional conductive agent has a rigid structure, which restricts the volume change of the positive electrode active material in the battery cell during cycling. This makes the positive electrode active material prone to particle pulverization and cracking under large expansion forces in the middle and later stages of the battery's long cycle life. The exposed fresh material interface can undergo side reactions with the electrolyte, exacerbating lithium consumption and limiting further improvement in the cycle life of the battery cell in the later stages of long-cycle operation. The battery cell provided in this application further incorporates first cyclic esters such as fluoroethylene carbonate and vinylene carbonate into the electrolyte, thereby further improving the cycle life of the battery cell, including the high-density positive electrode film layer. Although the mechanism is not yet clear, it is speculated that the first cyclic carbonate can form a stable electrolyte interface film (CEI film) on the exposed interface of the positive electrode active material, which helps reduce the probability of side reactions between the fresh interface exposed by the active material particles due to pulverization and cracking and the electrolyte, thereby reducing lithium consumption.

[0039] In any embodiment, the mass content of the fluoroethylene carbonate is 0.05%-8% based on the total mass of the electrolyte.

[0040] In any embodiment, the mass content of the fluoroethylene carbonate is 0.1%-5% based on the total mass of the electrolyte.

[0041] The mass content of fluoroethylene carbonate in the electrolyte meets the above range, which is conducive to the formation of a positive electrode interface CEI film with a suitable thickness on the surface of the positive electrode particles. This reduces the probability of phenomena such as excessive CEI film thickness and increased lithium-ion transport impedance, thereby improving the uniformity of current distribution in the positive electrode film layer and further enhancing the cycle performance of the energy storage battery cell.

[0042] In any embodiment, the mass content of vinylene carbonate is 0.5%-8% based on the total mass of the electrolyte.

[0043] In any embodiment, the mass content of vinylene carbonate is 0.6%-4% based on the total mass of the electrolyte.

[0044] The electrolyte includes vinylene carbonate, which can be oxidized when the battery charging voltage increases to form a positive electrode interface film. This helps to alleviate the direct contact between the fresh interface exposed by the pulverization and cracking of the positive electrode active material particles and the electrolyte, thereby reducing the occurrence of internal side reactions, lowering lithium consumption, and further improving the cycle performance of the battery cell. At the same time, vinylene carbonate can form an SEI film on the surface of the negative electrode active material particles, reducing the probability of side reactions between the electrolyte and the negative electrode during battery cycling, and further improving the cycle performance of the battery cell.

[0045] In any embodiment, the electrolyte comprises a second cyclic carbonate, which includes one or more of ethylene carbonate, propylene carbonate, butenyl carbonate, hexenyl carbonate, and γ-butyrolactone.

[0046] In any embodiment, the mass content of the second cyclic carbonate is 1%-10% based on the total mass of the electrolyte, optionally 3%-7%.

[0047] The electrolyte contains the aforementioned types of second cyclic carbonates, and the mass content of the second cyclic carbonates meets the above-mentioned range. This enables the electrolyte to have suitable viscosity and ionic conductivity, improves the uniformity of current density distribution in the high-density cathode film, reduces the probability of lithium plating, and further enhances the cycle performance of the battery cell.

[0048] In any embodiment, the electrolyte further includes one or more of methyl ethyl carbonate and diethyl carbonate.

[0049] The electrolyte also includes the aforementioned linear carbonates, which can give the electrolyte a suitable viscosity, improve the wettability of the electrolyte in the high-density cathode film, improve the uniformity of current density distribution, reduce the probability of lithium plating, and further improve the cycle performance of the battery cell.

[0050] In any embodiment, the electrolyte comprises lithium sulfonamide salt, and the mass content of the lithium sulfonamide salt is 1%-10% based on the total mass of the electrolyte.

[0051] In any embodiment, the mass content of the lithium sulfonamide salt is 2%-7% based on the total mass of the electrolyte.

[0052] The electrolyte contains lithium sulfonylimide salt and the mass content of lithium sulfonylimide salt within the above-mentioned range, which enables the electrolyte to have suitable ionic conductivity, helps to improve the uniformity of current distribution in the high-density cathode film, and enhances the cycle performance of the battery cell. Simultaneously, it can reduce the probability of corrosion reaction between sulfonylimide anions and the current collector metal, further improving the cycle performance of the battery cell.

[0053] In any embodiment, the lithium salt further includes lithium hexafluorophosphate, and the mass ratio of the lithium hexafluorophosphate to the lithium sulfonamide salt in the electrolyte is 1-10.

[0054] In any embodiment, the mass ratio of lithium hexafluorophosphate to lithium sulfonamide salt in the electrolyte is 2-4.

[0055] When the mass ratio of lithium sulfonylimide salt to lithium hexafluorophosphate in the electrolyte meets the above-mentioned range, the electrolyte can have a suitable ionic conductivity, improve the uniformity of current distribution in the positive electrode film, and thus enhance the cycle performance of the battery cell.

[0056] In any embodiment, the lithium sulfonamide salt includes one or more of lithium bisfluorosulfonamide and lithium bistrifluoromethanesulfonate.

[0057] Electrolytes containing the aforementioned types of sulfonylimide lithium salts exhibit higher lithium-ion mobility, enabling the electrolyte to possess suitable ionic conductivity. This helps improve the uniformity of current distribution in the positive electrode film, further enhancing the cycle performance of the battery cell.

[0058] In any embodiment, the powder compaction density of the positive electrode active material at 3T is 2.2 g / cm³. 3 -3.2g / cm 3 .

[0059] In any embodiment, the powder compaction density of the positive electrode active material at 3T is 2.5 g / cm³. 3 -2.9g / cm3 .

[0060] Meeting the above-mentioned range of powder compaction density of positive electrode active material is beneficial to increasing the compaction density of positive electrode film, increasing the loading of active material in positive electrode film, and thus further improving the capacity of battery cell.

[0061] In any embodiment, the compaction density of the positive electrode film is 2.5 g / cm³. 3 -2.8g / cm 3 .

[0062] Meeting the above-mentioned range in terms of compaction density of the positive electrode film layer is beneficial to increasing the loading of active materials in the positive electrode film layer, thereby further improving the capacity of the battery cell.

[0063] In any embodiment, the thickness of the positive electrode film on either side is 40 μm-400 μm.

[0064] In any embodiment, the thickness of the positive electrode film on either side is 100μm-200μm.

[0065] If the thickness of either side of the positive electrode film meets the above range, it can increase the loading of active materials in the battery cell and increase the battery capacity. At the same time, it is also beneficial to improve the wettability of the electrolyte in the positive electrode film, so that the lithium ion transport path in the positive electrode film has a suitable distance, which is beneficial to improve the uniformity of the current density distribution of the positive electrode film and improve the cycle life of the energy storage battery.

[0066] In any embodiment, the electrode assembly includes a negative electrode sheet, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, wherein the thickness of the negative electrode film layer on any side is 30μm-300μm.

[0067] In any embodiment, the thickness of the negative electrode film on either side is 80μm-180μm.

[0068] The thickness of the negative electrode film on either side meets the above range, which ensures that the lithium ion transport path in the negative electrode film has a suitable distance, which helps to reduce the probability of lithium plating on the negative electrode and further improves the cycle life of the energy storage battery cell.

[0069] In any embodiment, the positive electrode active material comprises a lithium-containing transition metal phosphate with an olivine structure, the lithium-containing transition metal phosphate comprising a dopant element Q, the dopant element Q comprising one or more of Ti, V, Al, Mg, W, Na, K, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, B, S, Si, N, F, Cl, Br, and Zr.

[0070] Lithium-containing transition metal phosphates with an olivine structure exhibit excellent cycle life, thermal stability, and safety performance. The use of lithium-containing transition metal phosphates as the positive electrode active material in the battery cells of this application embodiment helps improve the reliability of the battery cells during long-term cycle operation in energy storage scenarios. Doping the lithium-containing transition metal phosphate with element Q can improve the stability of the crystal structure and the rate performance of the positive electrode active material, which is beneficial for improving the uniformity of the current density distribution in a large-area positive electrode film, reducing the probability of particle pulverization and cracking, and further improving the cycle life of the energy storage battery.

[0071] In any embodiment, the lithium-containing transition metal phosphate has components of the following general formula:

[0072] LimFexPyOjQq,

[0073] Wherein, Q includes one or more of W, Al, Na, K, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, Br, and Zr, with 0.8≤m≤1.15, 0.9≤x≤1, 0.95≤y≤1, 3.5≤j≤4, and 0≤q≤0.1.

[0074] In any embodiment, the median L of the sphericity in the cumulative distribution curve of the particle sphericity area obtained from a cross-section of the positive electrode film along the electrode thickness direction is... A50 It is 0.70-0.85.

[0075] In any embodiment, the median L of the sphericity in the cumulative distribution curve of the particle sphericity area obtained from a cross-section of the positive electrode film along the electrode thickness direction is... A50 It is 0.70-0.76.

[0076] In the cumulative distribution curve of the spheroidal area of ​​the particles obtained by the cross section of the positive electrode film along the thickness direction of the electrode sheet, the median of spheroidal area within the above range means that the particles occupying most of the area and space in the positive electrode film are also relatively rounded and the material morphology is relatively uniform. Under the action of external force, they can effectively slip and participate in the connection and reconstruction of the force chain, thereby helping to improve the compaction density of the positive electrode film and the capacity of the battery cell.

[0077] In any embodiment, the median C of the graphitization degree C value 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 ranges from 0.98 to 1.20, where the degree of graphitization C is I. G / I D I G This indicates that the Raman spectrum is at 1580±100 cm⁻¹ -1The intensity of peak G at I D This indicates that the Raman spectrum is at 1350±100 cm⁻¹ -1 The intensity of peak D at that location.

[0078] In any embodiment, the median C of the graphitization degree C value in the cumulative distribution curve of the positive electrode film obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode is... 50 It is 1.02-1.10.

[0079] The higher the degree of graphitization of carbon on the surface of the positive electrode active material, the higher the proportion of graphite structure carbon in the positive electrode film layer. The particles are more likely to slip during the rolling process by means of the highly graphitized carbon structure in the coating material. This can further reduce the possibility of stress concentration and increase the compaction density of the positive electrode film layer. Furthermore, the high degree of graphitization of the coating material can improve the electronic conductivity of the positive electrode sheet and improve the current distribution of the large-area coating positive electrode film layer, thereby improving the cycle performance of the battery cell.

[0080] In any embodiment, the thickness of the positive current collector is 10μm-17μm.

[0081] In any embodiment, the thickness of the positive current collector is 12μm-15μm.

[0082] High-density positive electrode film can increase the loading of active material and improve battery capacity. However, during the compaction process of the positive electrode sheet, the high rolling pressure acts on the thickness direction of the current collector, causing it to extend in the direction perpendicular to the thickness, resulting in thinner current collector. This increases the probability of cracks and breakage in the later stages of long-cycle energy storage batteries. In the embodiments of this application, the thickness of the current collector in the battery cell is controlled to meet the above range, which can effectively reduce the probability of cracks and breakage in the positive electrode sheet during cycling, and further improve the cycle performance of the energy storage battery.

[0083] An embodiment of the second aspect of this application provides a battery device that includes the battery cell described in the above embodiments.

[0084] An embodiment of the third aspect of this application provides an electrical device that includes the battery cell described in the above embodiments.

[0085] An embodiment of the fourth aspect of this application provides an energy storage device comprising the battery cells described in the above embodiments.

[0086] 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

[0087] 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.

[0088] Figure 1 is a schematic diagram of a battery cell according to an embodiment of this application;

[0089] Figure 2 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 1;

[0090] Figure 3 is a schematic diagram of a battery module according to an embodiment of this application;

[0091] Figure 4 is a schematic diagram of a battery pack according to an embodiment of this application;

[0092] Figure 5 is an exploded view of the battery pack of one embodiment of this application shown in Figure 4;

[0093] Figure 6 is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to an embodiment of this application.

[0094] Explanation of reference numerals in the attached figures:

[0095] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate. Detailed Implementation

[0096] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell, battery assembly, power consumption device, and energy storage device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0097] 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.

[0098] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0099] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0100] 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.

[0101] 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.

[0102] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0103] In recent years, battery cells have been increasingly used in energy storage systems. To meet market demand for high capacity, it is necessary to increase the load of positive electrode active material per unit volume in battery cells to achieve high capacity, improve the energy storage capacity of energy storage systems, and meet the application and functional requirements of energy storage systems such as "continuous operation and energy transfer". However, the applicant has found that when large-capacity energy storage battery cells are continuously charged beyond their individual charging cutoff voltage (i.e., "overcharging"), lithium plating and overheating are likely to occur, triggering thermal runaway and thermal propagation, making it difficult to further improve the safety performance and cycle life of energy storage batteries.

[0104] Based on this, this application provides a battery cell, the battery cell including an electrode assembly and an electrolyte, the electrode assembly including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer including a positive electrode active material and additives, and the compaction density of the positive electrode film layer being 2.4 g / cm³. 3 -2.9g / cm 3 The additives include one or more of lithium carbonate, transition metal cyclohexane, polypyridine-transition metal complex, thiazoline and its derivatives, and the electrolyte includes dimethyl carbonate, wherein the mass content of dimethyl carbonate is 15%-80% based on the total mass of the electrolyte.

[0105] Unlike power batteries, energy storage batteries need to operate in conjunction with power station systems to meet the requirements of constant power charging. This means that the charging current of an energy storage battery does not decrease as its capacity decays throughout its entire lifespan. Power batteries, on the other hand, are typically charged at a constant rate, meaning the charging current is adapted to the battery capacity. As the capacity of individual battery cells decreases during use, the charging current of the power battery also decreases accordingly. This fundamental difference forces energy storage batteries to withstand higher charging rates after capacity decay, leading to uneven current density distribution within individual battery cells, lithium plating, and a deterioration in the cycle life of individual battery cells. Furthermore, because power station systems continuously supply power, the charging voltage of individual battery cells in the battery module is prone to exceeding their charging cut-off voltage, i.e., overcharging. This is detrimental to the long-term safe and stable operation of energy storage batteries, limiting further improvements in their safety performance and cycle life.

[0106] The applicant's research found that adding additives such as lithium carbonate, transition metal cyclohexane, polypyridine-transition metal complex, thiamethoxam and its derivatives to the high-density positive electrode film can preferentially decompose and undergo redox reactions when the monomer is overcharged, inhibiting the occurrence of heat-generating chain reactions during overcharging, thereby improving the overcharge safety performance of the energy storage battery module and enhancing the cycle life and safety performance of the energy storage battery module.

[0107] However, research shows that compared to the positive electrode active material in the positive electrode film, additives such as lithium carbonate have poorer ionic and electronic conductivity. Although they can improve the safety performance of energy storage batteries, they increase the impedance of the high-density positive electrode sheet, worsen its kinetic performance, further deteriorate the uniformity of the current density distribution in the positive electrode film, induce concentration polarization within the battery, and easily cause a performance drop after long-cycle charging under constant power conditions, thus limiting further improvements in the cycle life of energy storage batteries. Further research by the applicant found that dimethyl carbonate has a short linear carbon chain in its molecular structure, resulting in lower viscosity. Adding 15%-80% dimethyl carbonate to the electrolyte helps reduce the overall viscosity of the electrolyte, improves the wettability of the electrolyte under high-density conditions, helps improve the lithium-ion transport efficiency in the positive electrode sheet, improves the impedance of the positive electrode sheet and the uniformity of the current density distribution in the positive electrode film, reduces concentration polarization, and thus further improves the cycle life of energy storage batteries.

[0108] In some embodiments, the compaction density of the positive electrode film layer may be selected as 2.40 g / cm³. 3 2.45g / cm 3 2.50g / cm 3 2.55g / cm 3 2.60g / cm 3 2.65g / cm 3 2.70 g / cm 3 2.75g / cm 3 2.80g / cm 3 2.85g / cm 3 2.90g / cm 3 2.95g / cm 3 3.00g / cm 3 Or the range of values ​​between any two.

[0109] In this application, the compaction density of the positive electrode film can be determined by instruments and methods known in the art. For example, after discharging the battery cell to a fully discharged state (approximately 0% SOC), the positive electrode sheet at full discharge is disassembled, and the residual electrolyte is cleaned with an organic solvent (the organic solvent can be a conventional solvent in the art that can clean the electrolyte, including but not limited to dimethyl carbonate, etc.). After removing the residual electrolyte, the electrode sheet is dried, and the compaction density of the positive electrode film is measured. The compaction density of the positive electrode film is the density of any side of the positive electrode film measured after disassembly / the thickness of any side of the positive electrode film.

[0110] In this application, the fully discharged state refers to placing the battery cell at 25°C and letting it stand for 2 hours until the battery temperature is maintained at 25°C, then discharging the battery at a constant power of 0.5P until the discharge cutoff voltage is reached.

[0111] In this application, the density of any side of the positive electrode film layer has a meaning known in the art and can be tested using methods known in the art. For example, take a positive electrode sheet that has been coated on one side and cold-pressed, or take out the positive electrode sheet from a fully discharged battery cell (if it is a double-sided coated positive electrode sheet, the positive electrode film layer on one side can be wiped off first), cut it into a small circular piece with an area of ​​S1, weigh it, and record its weight as M1. Then wipe off the positive electrode film layer of the above-weighed positive electrode sheet, weigh the current collector, and record it as M0. The density of any side of the positive electrode film layer = (M1-M0) / S1. To ensure the accuracy of the test results, multiple groups (e.g., 10 groups) of samples can be tested, and the average value can be calculated as the test result, with the unit being g / 1540.25mm. 2 .

[0112] The thickness of either side of the positive electrode film layer has a meaning known in the art and can be tested using methods known in the art, such as a micrometer (e.g., a Mitutoyo 293-100 with an accuracy of 0.1 μm). It is understood that when a battery cell is fully discharged, the compaction density of the positive electrode film layer differs from the design value of the battery cell's compaction density. Due to practical operational factors, when disassembling a fully discharged battery cell to test the compaction density of the positive electrode film layer, the measured value is often slightly lower than the design value.

[0113] In this application, the term "transition metallocene" has the meaning known in the art, referring to organometallic coordination compounds formed by transition metals and cyclopentadiene or substituted cyclopentadiene ligands. In this application, the term "polypyridine-transition metal complex" has the meaning known in the art, referring to complexes formed by transition metal ions and polypyridine ligands (e.g., pyridine, bipyridine, etc.) through coordination bonds. It is understood that transition metals include, but are not limited to, Fe, Co, Ni, Ti, Zr, V, etc. In this application, the term "thiaanthracene and its derivatives" has the meaning known in the art, referring to diaromatic sulfur heterocyclic compounds formed by two benzene rings bridged by two sulfur atoms; derivatives refer to compounds formed by substituent modification of the thiaanthracene molecule.

[0114] In some embodiments, the dimethyl carbonate content is 15%-50% based on the total mass of the electrolyte.

[0115] In some embodiments, the mass content of dimethyl carbonate, based on the total mass of the electrolyte, is 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any range between the two.

[0116] In some embodiments, the mass content of the additive is 0.1%-5% based on the total mass of the positive electrode film.

[0117] In some embodiments, the mass content of the additive is 0.5%-3% based on the total mass of the positive electrode film.

[0118] When the mass content of additives in the high-density positive electrode film meets the above range, it can improve the safety performance of the energy storage battery while reducing the space occupied by the active material in the positive electrode film and the deterioration of the uniformity of the current density distribution in the positive electrode film, thus improving the capacity and cycle life of the battery cells.

[0119] In some embodiments, the coating area of ​​the positive electrode film in the battery cell is 11m². 2 -150m 2 .

[0120] In some embodiments, the coating area of ​​the positive electrode film in the battery cell may be selected as 11m². 2 15m 2 18m 2 20m 2 30m 2 40m 2 50m 2 60m 2 70m 280m 2 90m 2 100m 2 110m 2 120m 2 130m 2 140m 2 150m 2 Or the range of values ​​between any two.

[0121] In some embodiments, the coating area of ​​the positive electrode film in the battery cell is 11m². 2 -120m 2 In some embodiments, the coating area of ​​the positive electrode film in the battery cell is 11m². 2 -100m 2 .

[0122] In this application, the term "positive electrode film" has the meaning known in the art, referring to the area of ​​the positive electrode active material covering the positive electrode current collector. "Coating area of ​​the positive electrode film" refers to the area calculated by multiplying the length and width of the area of ​​the positive electrode active material covering the positive electrode current collector.

[0123] Understandably, the coating area of ​​the positive electrode film in a single battery cell refers to the area of ​​the positive active material covering the positive current collector in all electrode components within the battery cell. It should be noted that for a single-sided coated positive electrode, the coating area is calculated by statistically analyzing the area of ​​the positive active material covering the positive current collector on that side; for a double-sided coated positive electrode, the coating area is calculated by summing the areas of the positive active material covering the positive current collector on both sides separately.

[0124] In some embodiments, the capacity of the battery cell is greater than or equal to 400 Ah.

[0125] In some embodiments, the capacity of the battery cell can be selected as 400Ah, 500Ah, 600Ah, 700Ah, 800Ah, 900Ah, 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.

[0126] In some embodiments, the capacity of the battery cell is 400Ah-3000Ah. In some embodiments, the capacity of the battery cell is 500Ah-1500Ah. In some embodiments, the capacity of the battery cell is 600Ah-1000Ah.

[0127] In this application, the term "capacity of a single battery cell" refers to the maximum amount of charge that a single battery cell can store.

[0128] In this application, the capacity of a single battery cell can be tested using equipment and methods known in the art. For example, at 25°C, the battery cell is discharged at a constant power of 0.5P to its discharge cutoff voltage and allowed to stand for 30 minutes. Then, the battery cell is subjected to a charge-discharge cycle test at a constant power of 0.5P: First charge-discharge cycle: The battery cell is charged at a constant power of 0.5P to its charging cutoff voltage, allowed to stand for 30 minutes, and then discharged at a constant power of 0.5P to its discharge cutoff voltage. The discharge capacity Q1 is recorded, where Q1 is the capacity of the battery cell, in Ah.

[0129] In this application, those skilled in the art can reasonably adjust the discharge cut-off voltage and charge cut-off voltage according to the different types of positive electrode active materials and the operating conditions of the battery cells. As an example, if lithium iron phosphate is used as the positive electrode active material, the discharge cut-off voltage can be set to 2.5V and the charge cut-off voltage can be set to 3.65V.

[0130] In some embodiments, the dimension of the battery cell along the first direction is T, the dimension of the battery cell along the second direction is H, and the dimension of the battery cell along the third direction is L, where 50mm≤T≤100mm, 200mm≤H≤240mm, and 250mm≤L≤350mm, and the first direction, the second direction, and the third direction are perpendicular to each other.

[0131] In some embodiments, the dimension T of the battery cell along the first direction can be selected as 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, 85mm, 90mm, 95mm, 100mm, or any value range between two of these. In some embodiments, the dimension T of the battery cell along the first direction satisfies 60mm ≤ T ≤ 90mm.

[0132] In some embodiments, the dimension H of the battery cell along the second direction can be selected as 200mm, 205mm, 210mm, 215mm, 220mm, 225mm, 230mm, 235mm, 240mm, or any value range between two of these. In some embodiments, the dimension H of the battery cell along the second direction satisfies 210mm ≤ H ≤ 230mm.

[0133] In some embodiments, the dimension L of the battery cell along a third direction can be selected as 250mm, 260mm, 270mm, 280mm, 290mm, 300mm, 310mm, 320mm, 330mm, 340mm, 350mm, or any value between two of these. In some embodiments, the dimension L of the battery cell along a third direction satisfies 260mm ≤ L ≤ 290mm.

[0134] Large-size, high-capacity battery cells have a high active material load, which helps meet the high-capacity requirements of energy storage power systems. However, large-size, high-capacity battery cells are prone to lithium plating and heat accumulation when overcharged, posing a high risk of triggering a thermal runaway chain, which is detrimental to improving the safety performance and cycle life of energy storage battery module systems. The technical solution provided in this application is particularly suitable for large-size, high-capacity battery cells, and can effectively improve the safety performance of the high-density positive electrode film in large-size, high-capacity battery cells during overcharge, further improving the safety performance and cycle life of energy storage batteries.

[0135] In some implementations, the second direction is parallel to the direction of gravity.

[0136] The second direction is parallel to the direction of gravity of the battery cell in use. It can be understood that when the energy storage device is placed on a horizontal surface, the direction of gravity of the battery cell is parallel to the first direction, which is parallel to the height direction of the battery cell when it is loaded into the energy storage device.

[0137] In some embodiments, the positive electrode film layer includes a one-dimensional conductive agent, and the mass content of the one-dimensional conductive agent is 0.1%-2% based on the total mass of the positive electrode film layer.

[0138] The applicant's research found that the positive electrode film contains a one-dimensional conductive agent, which can form a linearly intersecting mesh conductive network inside the positive electrode film. This is beneficial to improving the conductivity of the positive electrode sheet, improving the uniformity of current distribution in the high-density positive electrode film containing additives such as lithium carbonate, and simultaneously improving the safety and cycle performance of the battery cell.

[0139] In some embodiments, based on the total mass of the positive electrode film, the mass content of the one-dimensional conductive agent 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%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, or any value range between the two.

[0140] In some embodiments, the mass content of the one-dimensional conductive agent is 0.2%-1% based on the total mass of the positive electrode film.

[0141] The content of one-dimensional conductive agent in the positive electrode film layer within the above range can effectively reduce the excessive space occupied by the one-dimensional conductive agent in the positive electrode active material, while improving the battery's capacity, safety performance and cycle performance.

[0142] In some embodiments, the specific surface area of ​​the one-dimensional conductive agent is 100 m². 2 / g-220m 2 / g.

[0143] In some embodiments, the specific surface area of ​​the one-dimensional conductive agent may be selected as 100 m². 2 / g、110m 2 / g、120m 2 / g、130m 2 / g, 140m 2 / g, 150m 2 / g、160m 2 / g、170m 2 / g、180m 2 / g、190m 2 / g、200m 2 / g、210m 2 / g、220m 2 / g or any value between the two.

[0144] In some embodiments, the oil absorption value of the one-dimensional conductive agent is 100mL / 100g-200mL / 100g.

[0145] In some embodiments, the oil absorption value of the one-dimensional conductive agent can be selected as 100mL / 100g, 110mL / 100g, 120mL / 100g, 130mL / 100g, 140mL / 100g, 150mL / 100g, 160mL / 100g, 170mL / 100g, 180mL / 100g, 190mL / 100g, 200mL / 100g, or any value range between the two.

[0146] The fact that the specific surface area and oil absorption value of the one-dimensional conductive agent meet the above range indicates that the one-dimensional conductive agent has a suitable pore structure, which effectively reduces the probability of the one-dimensional conductive agent agglomerating and entangled in the positive electrode film, thereby forming a good conductive network. This is beneficial to improving the conductivity of the positive electrode sheet, improving the current distribution in the high-density positive electrode film, and further improving the cycle performance of the battery cell.

[0147] In this paper, the specific surface area of ​​one-dimensional conductive agents can be determined by any method known in the art. As an example, the following method can be used: Referring to GB / T 19587-2017, the specific surface area of ​​the one-dimensional conductive agent sample is tested using the nitrogen adsorption specific surface area analysis method, and the result is calculated using the BET (Brunauer Emmett Teller) method. The testing instrument can be a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, USA.

[0148] In this paper, the oil absorption value of the one-dimensional conductive agent can be determined by any method known in the art. As an example, the following method can be used: The oil absorption value of the one-dimensional conductive agent is tested using the paraffin oil + torque method: A DABS-H model oil absorbent meter is selected, and the oil absorption value of the one-dimensional conductive agent is tested according to the national standard "Carbon Black Part 2: Determination of Oil Absorption Value" (GB / T3780.2—2007). The sample is added to the mixing tank of the oil absorbent meter, and paraffin oil is added to the sample at a rate of 4 mL / min using a titrator. As the oil absorption value of the sample increases, the mixture changes from a free-flowing state to a semi-plastic agglomerate, and the viscosity of the mixture continuously increases. This viscosity is transmitted to the torque sensing system of the oil absorbent meter. When the viscosity of the mixture reaches a predetermined torque value, the oil absorbent meter and the titrator automatically shut off simultaneously. The volume of oil added is read directly from the burette; the volume of oil absorbed per unit mass of sample is the oil absorption value of the sample.

[0149] In some embodiments, the powder resistivity of the one-dimensional conductive agent is less than or equal to 50 mΩ·cm. In some embodiments, the powder resistivity of the one-dimensional conductive agent can be selected from 5 mΩ·cm, 10 mΩ·cm, 15 mΩ·cm, 20 mΩ·cm, 25 mΩ·cm, 30 mΩ·cm, 35 mΩ·cm, 40 mΩ·cm, 45 mΩ·cm, 50 mΩ·cm, or any value range between the two.

[0150] The resistivity of the one-dimensional conductive agent powder meets the above range, which is beneficial to improve the conductivity of the positive electrode sheet, thereby improving the uniformity of the current density distribution in the high-density positive electrode film and improving the cycle performance of the battery cell.

[0151] In this paper, the powder resistivity of one-dimensional conductive agents can be determined by any method known in the art. As an example, the following method can be used for testing: using a PRCD1100 powder resistivity meter, referring to the national standard GB / T30835-2014.

[0152] In some embodiments, the one-dimensional conductive agent includes one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, and carbon nanofibers.

[0153] The positive electrode film includes the above-mentioned types that can form a good conductive network in the high-density positive electrode film, thereby improving the conductivity of the positive electrode sheet and the cycle performance of the energy storage battery cell.

[0154] In some embodiments, the electrolyte comprises a first cyclic carbonate, which includes one or more of fluoroethylene carbonate and vinylene carbonate.

[0155] The applicant's research indicates that the conductive network formed by the one-dimensional conductive agent has a rigid structure, which restricts the volume change of the positive electrode active material in the battery cell during cycling. This makes the positive electrode active material prone to particle pulverization and cracking under large expansion forces in the middle and later stages of the battery's long cycle life. The exposed fresh material interface can undergo side reactions with the electrolyte, exacerbating lithium consumption and limiting further improvement in the cycle life of the battery cell in the later stages of long-cycle operation. The battery cell provided in this application further incorporates first cyclic esters such as fluoroethylene carbonate and vinylene carbonate into the electrolyte, thereby further improving the cycle life of the battery cell, including the high-density positive electrode film layer. Although the mechanism is not yet clear, it is speculated that the first cyclic carbonate can form a stable electrolyte interface film (CEI film) on the exposed interface of the positive electrode active material, which helps reduce the probability of side reactions between the fresh interface exposed by the active material particles due to pulverization and cracking and the electrolyte, thereby reducing lithium consumption.

[0156] When used in this document, the composition and proportion of the first cyclic ester in the electrolyte can be determined using methods or instruments known in the art. As an example, the following method can be referenced: Disassemble the battery cell to obtain the electrolyte to be tested. Refer to GB / T9722-2023 "General Rules for Gas Chromatography of Chemical Reagents" for qualitative and quantitative analysis of the solvent in the electrolyte using gas chromatography to obtain the identification and proportion of the first cyclic ester.

[0157] In some embodiments, the mass content of the fluoroethylene carbonate is 0.05%-8% based on the total mass of the electrolyte.

[0158] In some embodiments, based on the total mass of the electrolyte, the mass content of the fluoroethylene carbonate can be selected as 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 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.

[0159] In some embodiments, the mass content of the fluoroethylene carbonate is 0.1%-5% based on the total mass of the electrolyte.

[0160] The mass content of fluoroethylene carbonate in the electrolyte meets the above range, which is conducive to the formation of a positive electrode interface CEI film with a suitable thickness on the surface of the positive electrode particles. This reduces the probability of phenomena such as excessive CEI film thickness and increased lithium-ion transport impedance, thereby improving the uniformity of current distribution in the positive electrode film layer and further enhancing the cycle performance of the energy storage battery cell.

[0161] In some embodiments, the vinylene carbonate content is 0.5%-8% based on the total mass of the electrolyte.

[0162] In some embodiments, based on the total mass of the electrolyte, the mass content of the vinylene carbonate can be selected as 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, or any range between the two.

[0163] In some embodiments, the vinylene carbonate content is 0.6%-4% based on the total mass of the electrolyte.

[0164] The electrolyte includes vinylene carbonate, which can be oxidized when the battery charging voltage increases to form a positive electrode interface film. This helps to alleviate the direct contact between the fresh interface exposed by the pulverization and cracking of the positive electrode active material particles and the electrolyte, thereby reducing the occurrence of internal side reactions, lowering lithium consumption, and further improving the cycle performance of the battery cell. At the same time, vinylene carbonate can form an SEI film on the surface of the negative electrode active material particles, reducing the probability of side reactions between the electrolyte and the negative electrode during battery cycling, and further improving the cycle performance of the battery cell.

[0165] In some embodiments, the electrolyte comprises a second cyclic carbonate, which includes one or more of ethylene carbonate, propylene carbonate, butenyl carbonate, hexenyl carbonate, and γ-butyrolactone.

[0166] In some embodiments, the mass content of the second cyclic carbonate is 1%-10% based on the total mass of the electrolyte, optionally 3%-7%.

[0167] The electrolyte contains the aforementioned types of second cyclic carbonates, and the mass content of the second cyclic carbonates meets the above-mentioned range. This enables the electrolyte to have suitable viscosity and ionic conductivity, improves the uniformity of current density distribution in the high-density cathode film, reduces the probability of lithium plating, and further enhances the cycle performance of the battery cell.

[0168] In some embodiments, the electrolyte further includes one or more of methyl ethyl carbonate and diethyl carbonate.

[0169] The electrolyte also includes the aforementioned linear carbonates, which can give the electrolyte a suitable viscosity, improve the wettability of the electrolyte in the high-density cathode film, improve the uniformity of current density distribution, reduce the probability of lithium plating, and further improve the cycle performance of the battery cell.

[0170] In some embodiments, the electrolyte comprises lithium sulfonamide salt, wherein the mass content of lithium sulfonamide salt is 1%-10% based on the total mass of the electrolyte.

[0171] In some embodiments, based on the total mass of the electrolyte, the mass content of the lithium sulfonamide salt can be selected as 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, or any range between the two.

[0172] In some embodiments, the mass content of the lithium sulfonamide salt is 2%-7% based on the total mass of the electrolyte.

[0173] The electrolyte contains lithium sulfonylimide salt and the mass content of lithium sulfonylimide salt within the above-mentioned range, which enables the electrolyte to have suitable ionic conductivity, helps to improve the uniformity of current distribution in the high-density cathode film, and enhances the cycle performance of the battery cell. Simultaneously, it can reduce the probability of corrosion reaction between sulfonylimide anions and the current collector metal, further improving the cycle performance of the battery cell.

[0174] In this application, the mass content of lithium sulfonylimide salt in the battery cell can be determined using instruments and methods known in the art. As an example, the following method can be used for testing: disassemble the battery cell, remove the electrolyte, and perform qualitative or quantitative analysis of the inorganic components / electrolyte lithium salt in the electrolyte using ion chromatography, referring to standard JY / T 0575-2020 "General Rules for Ion Chromatography Analysis," to determine the mass content of lithium sulfonylimide.

[0175] In some embodiments, the lithium salt further includes lithium hexafluorophosphate, and the mass ratio of the lithium hexafluorophosphate to the lithium sulfonamide salt in the electrolyte is 1-10.

[0176] In some embodiments, the mass ratio of lithium hexafluorophosphate to lithium sulfonamide salt in 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, 7.5, 8, 8.5, 9, 9.5, 10 or any range between the two.

[0177] In some embodiments, the mass ratio of lithium hexafluorophosphate to lithium sulfonamide salt in the electrolyte is 2-4.

[0178] When the mass ratio of lithium sulfonylimide salt to lithium hexafluorophosphate in the electrolyte meets the above-mentioned range, the electrolyte can have a suitable ionic conductivity, improve the uniformity of current distribution in the positive electrode film, and thus enhance the cycle performance of the battery cell.

[0179] In some embodiments, the lithium sulfonamide salt includes one or more of lithium bisfluorosulfonamide and lithium bistrifluoromethanesulfonate.

[0180] Electrolytes containing the aforementioned types of sulfonylimide lithium salts exhibit higher lithium-ion mobility, enabling the electrolyte to possess suitable ionic conductivity. This helps improve the uniformity of current distribution in the positive electrode film, further enhancing the cycle performance of the battery cell.

[0181] In some embodiments, the powder compaction density of the positive electrode active material at 3T is 2.2 g / cm³. 3 -3.2g / cm 3 .

[0182] In some embodiments, the powder compaction density of the positive electrode active material at 3T can be selected as 2.2 g / cm³. 3 2.3g / cm 3 2.4g / cm 3 2.5g / cm 3 2.6g / cm 3 2.7g / cm 3 2.8g / cm 3 2.9g / cm 3 3.0g / cm 3 3.1g / cm 3 3.2g / cm 3 Or the range of values ​​between any two.

[0183] In some embodiments, the powder compaction density of the positive electrode active material at 3T is 2.5 g / cm³. 3 -2.9g / cm 3 .

[0184] Meeting the above-mentioned range of powder compaction density of positive electrode active material is beneficial to increasing the compaction density of positive electrode film, increasing the loading of active material in positive electrode film, and thus further improving the capacity of battery cell.

[0185] In this application, the term "powder compaction density" refers to the density of a compacted compact with a certain density and strength, formed during the external force compression process. This density is measured in g / cm³, as the powder moves and deforms, larger voids are filled, the contact area between particles increases, resulting in attractive forces between atoms and enhanced mechanical cohesion between particles. 3 .

[0186] The compacted density of the positive electrode active material powder can be measured using methods and equipment known in the art. For example, it can be measured using a compaction density instrument, referring to GB / T 24533-2009. Specifically, a certain amount of positive electrode active material is placed on a compaction mold (the mold diameter is known). The mold is hollow in the middle and has a metal disc at the top and bottom. The positive electrode active material is placed between the metal discs, and a metal cylinder is placed on top. The mold is placed on a compaction density instrument, and the pressure is set to 3T. The thickness of the positive electrode active material under 3T pressure can be read on the instrument. The compacted density of the positive electrode active material powder is ρ = m / v, where v = (S × H), m is the mass of the positive electrode active material, and S is the bottom area of ​​the mold (1.327 cm²). 2 H represents the thickness of the positive electrode active material after compaction.

[0187] In some embodiments, the compaction density of the positive electrode film is 2.5 g / cm³. 3 -2.8g / cm 3 .

[0188] Meeting the above-mentioned range in terms of compaction density of the positive electrode film layer is beneficial to increasing the loading of active materials in the positive electrode film layer, thereby further improving the capacity of the battery cell.

[0189] In some embodiments, the thickness of the positive electrode film on either side is 40 μm-400 μm.

[0190] In some embodiments, the thickness of the positive electrode film on either side can be selected as 40 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm, 300 μm, 320 μm, 340 μm, 360 μm, 380 μm, 400 μm or any value range between the two.

[0191] In some embodiments, the thickness of the positive electrode film on either side is 100 μm-200 μm.

[0192] If the thickness of either side of the positive electrode film meets the above range, it can increase the loading of active materials in the battery cell and increase the battery capacity. At the same time, it is also beneficial to improve the wettability of the electrolyte in the positive electrode film, so that the lithium ion transport path in the positive electrode film has a suitable distance, which is beneficial to improve the uniformity of the current density distribution of the positive electrode film and improve the cycle life of the energy storage battery.

[0193] In some embodiments, the electrode assembly includes a negative electrode sheet, the negative electrode sheet including a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, wherein the thickness of the negative electrode film layer on any side is 30 μm-300 μm.

[0194] In some embodiments, the thickness of the negative electrode film on either side can be selected as 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm, 210μm, 220μm, 230μm, 240μm, 250μm, 260μm, 270μm, 280μm, 290μm, 300μm or any value range between the two.

[0195] In some embodiments, the thickness of the negative electrode film on either side is 80 μm-180 μm.

[0196] The thickness of the negative electrode film on either side meets the above range, which ensures that the lithium ion transport path in the negative electrode film has a suitable distance, which helps to reduce the probability of lithium plating on the negative electrode and further improves the cycle life of the energy storage battery cell.

[0197] In some embodiments, the positive electrode active material comprises a lithium-containing transition metal phosphate with an olivine structure, wherein the lithium-containing transition metal phosphate comprises a dopant element Q, and the dopant element Q comprises one or more of Ti, V, Al, Mg, W, Na, K, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, B, S, Si, N, F, Cl, Br, and Zr.

[0198] Lithium-containing transition metal phosphates with an olivine structure exhibit excellent cycle life, thermal stability, and safety performance. The use of lithium-containing transition metal phosphates as the positive electrode active material in the battery cells of this application embodiment helps improve the reliability of the battery cells during long-term cycle operation in energy storage scenarios. Doping the lithium-containing transition metal phosphate with element Q can improve the stability of the crystal structure and the rate performance of the positive electrode active material, which is beneficial for improving the uniformity of the current density distribution in a large-area positive electrode film, reducing the probability of particle pulverization and cracking, and further improving the cycle life of the energy storage battery.

[0199] In this application, the type and content of dopant element Q in the positive electrode active material can be tested using any method known in the art. As an example, inductively coupled plasma atomic emission spectrometry (ICP-AES) is used to test the dopant element Q and its content, referring to Appendix C of GB / T 33822-2017.

[0200] In some embodiments, the lithium-containing transition metal phosphate has components of the following general formula:

[0201] LimFexPyOjQq,

[0202] Wherein, Q includes one or more of W, Al, Na, K, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, Br, and Zr, 0.8≤m≤1.15, 0.9≤x≤1, 0.95≤y≤1, 3.5≤j≤4, and 0<q≤0.1.

[0203] In some embodiments, m can be 0.8, 0.85, 0.9, 0.95, 0.98, 1.00, 1.03, 1.05, 1.08, 1.10, 1.13, 1.15, or any value between two of these. In some embodiments, x can be 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, or any value between two of these. In some embodiments, y can be 0.95, 0.98, 1.0, or any value between two of these. In some embodiments, j can be 3.5, 3.6, 3.7, 3.8, 3.9, 4, or any value between two of these. In some implementations, q can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or any value between the two.

[0204] In some embodiments, the median L of the spheroidal area distribution curve of the particles obtained from the cross-section of the positive electrode film along the electrode thickness direction is... A50It is 0.70-0.85.

[0205] In some embodiments, the median L of the spheroidal area distribution curve of the particles obtained from the cross-section of the positive electrode film along the electrode thickness direction is... A50 The value can be selected as 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85 or any range between the two.

[0206] In some embodiments, the median L of the spheroidal area distribution curve of the particles obtained from the cross-section of the positive electrode film along the electrode thickness direction is... A50 It is 0.70-0.76.

[0207] In the cumulative distribution curve of the spheroidal area of ​​the particles obtained by the cross section of the positive electrode film along the thickness direction of the electrode sheet, the median of spheroidal area within the above range means that the particles occupying most of the area and space in the positive electrode film are also relatively rounded and the material morphology is relatively uniform. Under the action of external force, they can effectively slip and participate in the connection and reconstruction of the force chain, thereby helping to improve the compaction density of the positive electrode film and the capacity of the battery cell.

[0208] 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.

[0209] The particle identification method is as follows: The positive electrode film layer is cut along the thickness direction of the electrode sheet 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 (SEM) is used (for example, a Hitachi SU8230 device can be used, operating voltage: 3kV, beam current: high, probe model: U (LA100), working distance <5mm) to observe the cut surface along the thickness direction of the electrode sheet. Images are acquired using a field emission scanning electron microscope at a non-edge location in the cut surface of the positive electrode film layer (after observing the electrode edge under the SEM, 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 image to be analyzed, as shown in Figure 1; use the Cellpose plugin software to identify particles, and then perform manual corrections; use ImageJ to read and analyze data. The specific method for identifying particles using the Cellpose plugin software 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 by the software, or had identification errors. Particles that were not identified by the software, were not fully identified by the software, or had identification errors mainly include the following: 1. Particles that are too large or have scratches on their surface, making them unidentifiable or incompletely recognizable; 2. During argon ion beam cutting, scratches may be generated on the particle surface, and the software may misjudge 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 electron microscope's field of view, with the particle's interior penetrated by the edge, preventing a complete display of the morphology, and resulting in identification errors due to partial identification replacing the whole.For the unidentified or misidentified particles mentioned above, manual calibration is performed. The specific process is as follows: 1. Delete large particles located around the edges of the scanning electron microscope that are not fully displayed. 2. Determine if any unidentified or misidentified particles have internal cracks or scratches. If no cracks or scratches are found, classify it as a single particle and manually mark it based on the observed particle boundary. 3. If cracks or scratches are found inside the particle, determine if they penetrate the particle. If not, classify it as a single particle and manually mark it. 4. If cracks or scratches penetrate the particle, determine if they are linear or irregular. 5. If the cracks or scratches are irregular, classify them as the boundary between particles and divide the particles along this boundary. 6. If the cracks or scratches are linear, perform contrast comparison. 7. If the contrast is not obvious and there is no crack-like appearance, classify it as a scratch and mark it as a single particle. 8. If the contrast is strong and there is a crack-like appearance, classify it as the boundary between particles and mark it as two particles. After manual marking, delete information irrelevant to the particles from the automatic image processing, thus completing the particle identification and marking in the image.

[0210] The specific method for statistical analysis of particles in the positive electrode film is as follows: Images after particle identification and labeling are imported into ImageJ software for analysis. Scale settings are completed based on the scanning electron microscope (SEM) images. The particle size and area in the cross-section along the electrode thickness direction of the positive electrode film are analyzed using the "Feret Diameter," "Area," "Round," and "Solidity" analysis functions. According to the software manual (ImageJ User Guide IJ1.46r), the "Feret" parameter obtained from the analysis represents the maximum spacing between all parallel lines in the two-dimensional projection of the particle, thus characterizing the particle size. Since particles with a diameter less than 50 nm present significant errors during the statistical process and are difficult to accurately identify, and since the particle size of conductive agents is generally less than 50 nm, it will introduce significant errors into the statistical results. Therefore, in this application, particles with a diameter less than 50 nm are not counted in the particle size statistics process, and the statistical data for particles with AR, Round, or Solidity values ​​displayed as "NaN" are deleted. Following the above method, to ensure a statistically significant sample size, at least 10 non-overlapping scanning electron microscope images were acquired for each electrode, and the particle size of at least 5000 particles was statistically analyzed.

[0211] Unlike the state of the positive electrode active material in Malvern laser scattering, and also unlike the state of the positive electrode active material when directly observed by scanning electron microscopy, the particles in the positive electrode film exhibit a well-dispersed state under the action of roller pressure. Observing the positive electrode film is beneficial for effectively characterizing the particle size and distribution within it.

[0212] During the compaction process, the positive electrode film is compacted in the thickness direction. The cross-section of the positive electrode film along the thickness direction is more reflective of the actual compaction of the particles inside the film in a spatial scale than the surface of the positive electrode film.

[0213] It is understandable that the particles in the cross-section of the positive electrode film along the thickness direction of the electrode sheet, especially those larger than 50 nm, mainly originate from the positive electrode active material. Therefore, the embodiments of this application can accurately and objectively reflect the distribution of lithium-containing transition metal phosphate particles in the electrode sheet by observing and statistically analyzing the particle size in the cross-section of the positive electrode film.

[0214] In this application, the median test method for the sphericity of particles obtained from the cumulative distribution curve of particle sphericity area along the thickness direction of the positive electrode film is as follows: Particles in the cross-section of the positive electrode film are identified using the method described above. While using the "Feret" function in ImageJ to identify the particle size, the "Shape Description" and "Area" analysis functions are used to analyze the morphology and area of ​​the particles in the cross-section along the thickness direction of the positive electrode film. According to the software manual (ImageJ User Guide IJ1.46r), the "Area" parameter obtained from the analysis represents the pixel area of ​​the particle, and the "Round" parameter represents the ratio of the pixel area of ​​the particle to the area of ​​a circle with the fitted major axis as its diameter. 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 of the particle obtained from the analysis characterizes the sphericity of the particle. The sphericity of particles in the cross-section along the thickness direction of the obtained positive electrode film is arranged in ascending order. A cumulative distribution curve of the sphericity area of ​​particles in the positive electrode film is obtained with sphericity as the horizontal axis and cumulative area percentage as the vertical axis. The median sphericity refers to the sphericity corresponding to a cumulative area percentage of 50% on the vertical axis of the cumulative area distribution curve.

[0215] 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 ranges from 0.98 to 1.20, where the degree of graphitization C is I. G / I D I G This indicates that the Raman spectrum is at 1580±100 cm⁻¹ -1 The intensity of peak G at I D This indicates that the Raman spectrum is at 1350±100 cm⁻¹ -1 The intensity of peak D at that location.

[0216] 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 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.20, or any value range between the two.

[0217] 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 It is 1.02-1.10.

[0218] In this application, 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.

[0219] 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 1580±100 cm⁻¹. -1 Its characterization of carbon sp 2 Hybrid structure; D peak position is 1350±100 cm⁻¹ -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... 2 Hybridization 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 cathode film. A higher C value indicates a higher degree of graphitization of the carbon material. It is understandable that the degree of graphitization in the cathode film mainly originates from the graphitized carbon material within the film, i.e., the carbon coating material of the cathode active material. Although rich in sp... 2 One-dimensional conductive agents with hybrid structures (such as carbon nanotubes) also have relatively high I0. G / I DHowever, 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.

[0220] The higher the degree of graphitization of carbon on the surface of the positive electrode active material, the higher the proportion of graphite structure carbon in the positive electrode film layer. The particles are more likely to slip during the rolling process by means of the highly graphitized carbon structure in the coating material. This can further reduce the possibility of stress concentration and increase the compaction density of the positive electrode film layer. Furthermore, the high degree of graphitization of the coating material can improve the electronic conductivity of the positive electrode sheet and improve the current distribution of the large-area coating positive electrode film layer, thereby improving the cycle performance of the battery cell.

[0221] 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.

[0222] 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 cross-linked 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.

[0223] In some embodiments, the thickness of the positive current collector is 10 μm-17 μm.

[0224] In some embodiments, the thickness of the positive current collector can be selected as 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm or any value range between the two.

[0225] In some embodiments, the thickness of the positive current collector is 12μm-15μm.

[0226] High-density positive electrode film can increase the loading of active material and improve battery capacity. However, during the compaction process of the positive electrode sheet, the high rolling pressure acts on the thickness direction of the current collector, causing it to extend in the direction perpendicular to the thickness, resulting in thinner current collector. This increases the probability of cracks and breakage in the later stages of long-cycle energy storage batteries. In the embodiments of this application, the thickness of the current collector in the battery cell is controlled to meet the above range, which can effectively reduce the probability of cracks and breakage in the positive electrode sheet during cycling, and further improve the cycle performance of the energy storage battery.

[0227] [Positive electrode plate]

[0228] 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 a positive electrode active material.

[0229] 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.

[0230] In some embodiments, the positive electrode active material 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.

[0231] In some embodiments, the positive electrode active material layer 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.

[0232] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components used to prepare the positive electrode film layer, such as positive electrode active material, conductive agent, binder and any other components, in a solvent 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.

[0233] [Negative electrode plate]

[0234] 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.

[0235] 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.

[0236] 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.).

[0237] 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).

[0238] 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.

[0239] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0240] 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.

[0241] [Isolation membrane]

[0242] 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.

[0243] 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.

[0244] [Battery cell]

[0245] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0246] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0247] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0248] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 shows a square battery cell 5 as an example.

[0249] In some embodiments, referring to FIG2, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. A positive electrode sheet, a negative electrode sheet, and a separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0250] [Battery Device]

[0251] This application also provides a battery device, which includes the battery cell provided in this application. In some embodiments, the battery device is one or more of a battery module, a battery pack, and an energy storage device.

[0252] 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.

[0253] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in the battery module 4, multiple battery cells 5 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 5 can be fixed in place using fasteners.

[0254] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0255] 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.

[0256] Figures 4 and 5 show a battery pack 1 as an example. Referring to Figures 4 and 5, 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.

[0257] [Electrical appliances]

[0258] In addition, 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 can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0259] As the electrical device, a single battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0260] Figure 6 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the individual battery cells, a battery pack or battery module can be used.

[0261] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0262] This application also provides an energy storage device that uses a battery device as a power source. The energy storage device can be, but is not limited to, an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system.

[0263] Example

[0264] 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.

[0265] I. Preparation Method

[0266] Example 1

[0267] (1) Preparation of positive electrode active material

[0268] S1, lithium carbonate, iron phosphate, glucose and titanium dioxide are added to water and mixed in a premixing tank at 1800 rpm. The mixture is demagnetized by a demagnetizing rod with a magnetic field strength of 8000-12000 Gs. The ratio of lithium carbonate to iron phosphate is such that the molar ratio of iron to phosphorus is 0.975. The mass content of glucose relative to the total amount of iron phosphate is 5.7%. The titanium dioxide doping amount is such that the mass content of titanium doped in the carbon-coated lithium iron phosphate positive electrode active material product is 5000 ppm.

[0269] S2, the mixed raw materials are subjected to two grinding-demagnetization cycles in a sand mill. The first grinding is performed using 0.6mm diameter zirconia balls at 500rpm for 1 hour, with a grinding chamber pressure of less than 0.3MPa. After the first grinding, the raw materials are demagnetized using a permanent magnet separator with a demagnetization intensity greater than or equal to 8000Gs. The demagnetized raw materials are then ground a second time to obtain a mixed slurry. The particle size D of the mixed slurry is... V50 It is 0.40μm ± 0.10μm;

[0270] S3, the mixed slurry is spray-dried to obtain precursor powder.

[0271] S4, the precursor powder is sintered to obtain lithium iron phosphate cathode material. The sintering process includes:

[0272] First sintering: The precursor powder is sintered in a nitrogen atmosphere, heated from 25°C to 760°C at a heating rate of 5°C / min, and held at that temperature for 10 hours. After cooling, the first sintered product is obtained.

[0273] Grinding and mixing: Add 1.5% glucose and 3.0% polyethylene glycol (by weight of the first sintered product) to the first sintered product; divide into two groups and grind (third grinding), wherein the particle size of the first group is... V50Grinding was stopped when the particle size reached 1.0 μm ± 0.20 μm (grinding conditions: 550 rpm ± 50 rpm, grinding time 1 h), yielding the first group of ground products; the particle size D of the second group... V50 Grinding was stopped when the particle size reached 0.38μm±0.05μm (grinding conditions: 500rpm±50rpm, grinding time 4h), and a second set of grinding products was obtained; the first set of grinding products and the second set of grinding products were mixed at a mass ratio of 70:30 to obtain a mixed intermediate product; the mixed intermediate product was spray-dried.

[0274] Second sintering: The dried mixed intermediate product is sintered in a nitrogen atmosphere, heated from 25°C to 800°C at a heating rate of 5°C / min, and held at that temperature for 10 hours. After cooling, the second sintered product is obtained.

[0275] S5. After sintering, the product is cooled to below 100°C and then crushed using an air jet milling method to obtain carbon-coated lithium iron phosphate cathode active material. The air jet milling stage frequency is 25Hz and the milling pressure is 0.55MPa.

[0276] The prepared positive electrode active material has a carbon content of 1.248% by mass and a powder compaction density of 2.62 g / cm³ under a pressure of 3T. 3 .

[0277] (2) Preparation of the positive electrode sheet:

[0278] A mixture of 95.6 wt% positive electrode active material, 0.8 wt% conductive carbon black, 0.6 wt% one-dimensional conductive agent single-arm carbon nanotubes, 1.5 wt% lithium carbonate, and 1.5 wt% PVDF was prepared by mixing, followed by the addition of N-methylpyrrolidone and stirring to disperse the mixture. This positive electrode slurry was then coated onto a 13 μm thick aluminum foil, dried, and cold-pressed to obtain a single-sided surface density of 320 mg / 1540.25 mm. 2 The compacted density is 2.68 g / cm³. 3 The positive electrode. The one-dimensional conductive agent has a specific surface area of ​​150 m². 2 / g, oil absorption value of 155mL / 100g, powder resistivity of 10mΩ·cm.

[0279] The median C of the graphitization degree of the prepared positive electrode film obtained in laser microscopy confocal Raman spectroscopy instrument scanning mode. 50 The value is 1.04. In the cumulative distribution curve of the particle spheroidity area obtained from a cross-section along the electrode thickness direction, the median L of spheroidity is... A50 It is 0.725.

[0280] (3) Preparation of negative electrode sheet

[0281] The negative electrode film is formed by uniformly coating a negative electrode slurry (using deionized water as the solvent) onto the surface of a negative electrode current collector (a copper foil with a thickness of 5 μm), followed by drying and cold pressing. The negative electrode film comprises a negative electrode active material in a mass ratio of 96.1:0.7:1.2:2, a conductive agent acetylene black, a dispersant sodium carboxymethyl cellulose, and a binder styrene-butadiene rubber (SBR).

[0282] The single-sided density of the negative electrode film is 150 mg / 1540.25 mm. 2 When the battery cell is fully discharged, the compaction density of the negative electrode film is 1.6 g / cm³. 3 The porosity of the negative electrode sheet is 25%.

[0283] (4) Preparation of the separating membrane

[0284] The separator is made of polyethylene film with a thickness of 5μm and a porosity of 36%.

[0285] (5) Preparation of electrolyte

[0286] The electrolyte comprises 50% dimethyl carbonate (DMC), 10% ethyl methyl carbonate (EMC), 11% ethylene carbonate (EC), 10% propylene carbonate (PC), 3% lithium bis(fluorosulfonyl)imide (LiFSI), 6% lithium hexafluorophosphate (LiPF6), 2% fluoroethylene carbonate (FEC), and 8% vinylene carbonate (VC) by mass.

[0287] (6) Battery assembly

[0288] The negative electrode, separator, and positive electrode are arranged in sequence, with the separator positioned between the negative and positive electrodes to provide isolation. The bare cell is obtained by winding, placed in a casing, and filled with electrolyte. After encapsulation, formation, and venting, a battery cell is obtained. The battery cell has a capacity of 600 Ah, a length L of 271 mm, a height H of 213 mm, a thickness T of 71 mm, and a positive electrode film coating area of ​​20 m². 2 .

[0289] Example 2-3

[0290] The preparation of battery cells in Examples 2-3 is similar to that in Example 1, except that the mass content of dimethyl carbonate (DMC) in the electrolyte is adjusted. Specific parameters are shown in Table 1.

[0291] Examples 4-5

[0292] The preparation of the battery cells in Examples 4-5 is similar to that in Example 1, except that the mass content of dimethyl carbonate (DMC) in the electrolyte and the mass content of lithium carbonate in the positive electrode film are adjusted. The specific parameters are shown in Table 1.

[0293] Examples 6-8

[0294] The preparation of the battery cells in Examples 6-8 is similar to that in Example 1, except that the mass content of the one-dimensional conductive agent in the positive electrode film is adjusted. The specific parameters are shown in Table 1.

[0295] Examples 9-11

[0296] The preparation of the battery cells in Examples 9-11 is similar to that in Example 1, except that the preparation of the positive electrode active material is adjusted, specifically:

[0297] Example 9: In step S4, the D of the particles in the first group V50 Grinding was stopped when the particle size reached 1.50μm±0.20μm; grinding was stopped when the particle size Dv50 in the second group reached 0.50μm±0.05μm.

[0298] Example 10: In step S2, the particle size D of the mixed slurry V50 The thickness is 0.35μm ± 0.10μm; in step S4, after obtaining the first sintering product, a second sintering is performed directly, and the holding time for the second sintering is 12h.

[0299] Example 11: In step S4, the D of the particles in the first group V50 Grinding was stopped when the particle size reached 0.80μm ± 0.20μm; the D of the particles in the second group... V50 Stop grinding when the thickness reaches 0.30μm±0.05μm.

[0300] This alters the median C of the graphitization degree of the positive electrode film obtained in laser microscopy confocal Raman spectroscopy instrument scanning mode. 50 And in the cumulative distribution curve of particle spheroidity area obtained from the cross-section along the thickness direction of the positive electrode film, the median L of spheroidity is... A50 Specific parameters are shown in Table 2.

[0301] Comparative Example 1

[0302] The preparation of the battery cell in Comparative Example 1 is similar to that in Example 1, except that lithium carbonate is not added to the positive electrode film. Specific parameters are shown in Table 1.

[0303] Comparative Example 2

[0304] The preparation of the battery cell in Comparative Example 2 was similar to that in Example 1, except that the content of dimethyl carbonate in the electrolyte did not meet the requirement of 15%-80%. The specific parameters are shown in Table 1.

[0305] II. Performance Testing

[0306] 1. Battery cell overcharge safety performance test

[0307] At 25°C, the battery cell is charged to 5.475V at a constant current of 293.5A and held for 60 minutes. If the battery cell does not catch fire or explode, it is considered to have passed the overcharge safety test.

[0308] 2. Battery cell DC resistance (DCR) performance test

[0309] At 25℃, the voltage is charged to 3.65V at a constant current of 0.33C, then charged at a constant voltage to a current of 0.05C, and then discharged to 50% SOC at 0.33C. After resting for 2 hours, the voltage is pulsed at 0.5C for 30 seconds. The voltage is recorded before and after the pulse discharge, and the DCR is calculated. The calculation formula is DCR = (voltage before pulse discharge - voltage after pulse discharge) / pulse current.

[0310] 3. Battery cell capacity testing method

[0311] At 25℃, the battery cell is discharged at a constant power of 0.5P until the voltage of the battery cell is 2.5V, and then left to stand for 30 minutes. Then, the battery cell is subjected to charge-discharge cycle test at a constant power of 0.5P: First charge-discharge: The battery cell is charged at a constant power of 0.5P to 3.65V, left to stand for 30 minutes, and then discharged at a constant power of 0.5P to 2.5V. The discharge capacity Q1 is recorded. Q1 is the capacity of the battery cell, in Ah.

[0312] 4. Cycle performance test of individual battery cells at 25℃

[0313] At 25℃, the battery cells were discharged at a constant power of 0.5P until the voltage of the battery cells reached 2.5V, and then allowed to stand for 30 minutes. Then, the battery cells were subjected to charge-discharge cycle tests at a constant power of 0.5P: First charge-discharge: The battery cells were charged at a constant power of 0.5P to 3.65V, allowed to stand for 30 minutes, and then discharged at a constant power of 0.5P to 2.5V. The discharge capacity Q1 was recorded. After that, the battery cells were allowed to stand for 30 minutes, and the first charge-discharge steps were repeated. The charge-discharge test was carried out in this cycle, and the discharge capacity Qn was recorded until the discharge capacity Qn decayed to 70% of Q1. The number of cycles of the battery cells was then recorded.

[0314] 5. Cycle performance test of individual battery cells at 45℃

[0315] At 45℃, the battery cells were discharged at a constant power of 0.5P until the voltage of the battery cells reached 2.5V, and then allowed to stand for 30 minutes. Then, the battery cells were subjected to charge-discharge cycle tests at a constant power of 0.5P: First charge-discharge test: The battery cells were charged at a constant power of 0.5P to 3.65V, allowed to stand for 30 minutes, and then discharged at a constant power of 0.5P to 2.5V, and the discharge capacity Q1 was recorded. After that, the battery cells were allowed to stand for 30 minutes, and the first charge-discharge test was repeated. The charge-discharge test was repeated in this manner, and the discharge capacity Qn was recorded until the discharge capacity Qn decayed to 70% of Q1, at which point the number of cycles of the battery cells was recorded.

[0316] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0317] Battery cells for each embodiment and comparative example were prepared according to the above method, and various performance parameters were measured. The results are shown in the table below.

[0318] Table 1

[0319] The results show that, without the addition of safety additives such as lithium carbonate, the battery cells in Comparative Example 1 caught fire and exploded during the overcharge safety performance test, failing the test. As can be seen from the results of Comparative Example 2 in Table 1, while the addition of additives such as lithium carbonate to the positive electrode film can improve the safety performance of the battery cells, it also increases the impedance of the battery cells and worsens their cycle life.

[0320] As can be seen from the results of Examples 1-3 in Table 1, controlling the mass content of dimethyl carbonate in the electrolyte to be between 15% and 80% is beneficial to reducing the overall viscosity of the electrolyte. With the increase of dimethyl carbonate content, the wettability of the electrolyte in high compaction density is improved, which reduces the impedance of the battery cell and further improves the cycle life. In addition, as can be seen from the results of Examples 4 and 5 and Examples 1-3, simultaneously controlling the mass content of lithium carbonate in the positive electrode film and the mass content of dimethyl carbonate in the electrolyte, through their synergistic effect, can effectively reduce the impedance of the battery cell including additives such as lithium carbonate while improving the battery safety performance, thus giving the battery cell a better cycle life.

[0321] As can be seen from the results of Examples 1 and 6-8 in Table 1, the positive electrode film layer includes a one-dimensional conductive agent with a mass content of 0.1%-2%, and further 0.2%-1%, which can form a linear cross-shaped conductive network inside the positive electrode film layer, reduce the impedance of the battery cell including additives such as lithium carbonate, and improve the safety performance and cycle life of the battery cell.

[0322] Table 2

[0323] As can be seen from the results of Examples 1 and 9-11 in Table 2, the median L of the sphericity of the particles in the positive electrode film layer is... A50 A value of 0.70-0.76 indicates that the material has a relatively uniform and rounded morphology, and can effectively slip under external force, participating in the connection and reconstruction of the force chain, thereby helping to improve the compaction density of the positive electrode film. At the same time, in the later stages of battery cell cycling, the effective slippage of particles helps to alleviate the expansion of particles inside the positive electrode film, reduce the probability of particle breakage and pulverization, and further improve the cycle life of the battery cell.

[0324] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, which 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 electrode active material and additives. The compaction density of the positive electrode film is 2.4 g / cm³. 3 -3.0g / cm 3 The additives include one or more of lithium carbonate, transition metal cyclohexenes, polypyridine-transition metal complexes, thiazoline and their derivatives. The electrolyte includes dimethyl carbonate, and the mass content of the dimethyl carbonate is 15%-80% based on the total mass of the electrolyte.

2. The battery cell according to claim 1, characterized in that, Based on the total mass of the electrolyte, the mass content of dimethyl carbonate is 15%-50%.

3. The battery cell according to claim 1 or 2, characterized in that, Based on the total mass of the positive electrode film, the mass content of the additive is 0.1%-5%, optionally 0.5%-3%.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The total area of ​​the positive electrode film layer projected along the thickness direction of the positive electrode current collector is 11m². 2 -150m 2 11m is optional 2 -120m 2 Further options include 11m. 2 -100m 2 .

5. The battery cell according to any one of claims 1 to 4, characterized in that, The capacity of the battery cell is greater than or equal to 400Ah, and can be selected from 400Ah to 3000Ah, further selected from 500Ah to 1500Ah, and even further selected from 600Ah to 1000Ah.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The dimension of the battery cell along the first direction is T, the dimension of the battery cell along the second direction is H, and the dimension of the battery cell along the third direction is L. 50mm≤T≤100mm, 200mm≤H≤240mm, 250mm≤L≤350mm, the first direction, the second direction and the third direction are perpendicular to each other; optionally, the second direction is parallel to the direction of gravity.

7. The battery cell according to claim 6, characterized in that, The battery cell satisfies: 60mm≤T≤90mm or 210mm≤H≤230mm or 260mm≤L≤290mm.

8. The battery cell according to any one of claims 1 to 7, characterized in that, The positive electrode film layer includes a one-dimensional conductive agent, and the mass content of the one-dimensional conductive agent is 0.1%-2%, optionally 0.2%-1%, based on the total mass of the positive electrode film layer.

9. The battery cell according to claim 8, characterized in that, The one-dimensional conductive agent satisfies at least one of the following conditions: (1) The specific surface area of ​​the one-dimensional conductive agent is 100 m². 2 / g-220m 2 / g; (2) The oil absorption value of the one-dimensional conductive agent is 100mL / 100g-200mL / 100g; (3) The resistivity of the powder of the one-dimensional conductive agent is less than or equal to 50 mΩ·cm.

10. The battery cell according to claim 8 or 9, characterized in that, The one-dimensional conductive agent includes one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, and carbon nanofibers.

11. The battery cell according to any one of claims 1 to 10, characterized in that, The electrolyte includes a first cyclic carbonate, which includes one or more of fluoroethylene carbonate and vinylene carbonate.

12. The battery cell according to claim 11, characterized in that, Based on the total mass of the electrolyte, the mass content of the fluoroethylene carbonate is 0.05%-8%, optionally 0.1%-5%; and / or Based on the total mass of the electrolyte, the mass content of vinylene carbonate is 0.5%-8%, optionally 0.6%-4%.

13. The battery cell according to any one of claims 1 to 12, characterized in that, The electrolyte includes a second cyclic carbonate, which includes one or more of ethylene carbonate, propylene carbonate, butene carbonate, hexene carbonate, and γ-butyrolactone.

14. The battery cell according to claim 13, characterized in that, Based on the total mass of the electrolyte, the mass content of the second cyclic carbonate is 1%-10%, optionally 3%-7%.

15. The battery cell according to any one of claims 1 to 14, characterized in that, The electrolyte also includes one or more of methyl ethyl carbonate and diethyl carbonate.

16. The battery cell according to any one of claims 1 to 15, characterized in that, The electrolyte comprises lithium sulfonamide salt, and the mass content of the lithium sulfonamide salt is 1%-10% based on the total mass of the electrolyte, optionally 2%-7%.

17. The battery cell according to claim 16, characterized in that, The electrolyte also includes lithium hexafluorophosphate, and the mass ratio of lithium hexafluorophosphate to lithium sulfonamide salt is 1-10, optionally 2-4.

18. The battery cell according to claim 16 or 17, characterized in that, The lithium sulfonylimide salt includes one or more of lithium bisfluorosulfonylimide and lithium bistrifluoromethylsulfonate imide.

19. The battery cell according to any one of claims 1 to 18, characterized in that, The compacted density of the positive electrode active material at 3T is 2.2 g / cm³. 3 -3.2g / cm 3 2.5g / cm³ is an option. 3 -2.9 g / cm 3 .

20. The battery cell according to any one of claims 1 to 19, characterized in that, The compaction density of the positive electrode film is 2.5 g / cm³. 3 -2.8g / cm 3 .

21. The battery cell according to any one of claims 1 to 20, characterized in that, The thickness of the positive electrode film on either side is 40μm-400μm, and can be selected as 100μm-200μm.

22. The battery cell according to any one of claims 1 to 21, characterized in that, The electrode assembly includes a negative electrode sheet, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, the thickness of the negative electrode film layer on any side is 30μm-300μm, and can be selected as 80μm-180μm.

23. The battery cell according to any one of claims 1 to 22, characterized in that, The positive electrode active material comprises a lithium-containing transition metal phosphate with an olivine structure, wherein the lithium-containing transition metal phosphate comprises a dopant element Q, and the dopant element Q comprises one or more of Ti, V, Al, Mg, W, Na, K, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, B, S, Si, N, F, Cl, Br, and Zr.

24. The battery cell according to claim 23, characterized in that, The lithium-containing transition metal phosphate has the following general formula: LimFexPyOjQq, Wherein, Q includes one or more of W, Al, Na, K, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, Br, and Zr, 0.8≤m≤1.15, 0.9≤x≤1, 0.95≤y≤1, 3.5≤j≤4, and 0<q≤0.

1.

25. The battery cell according to any one of claims 1 to 24, characterized in that, In the cumulative distribution curve of particle sphericity area obtained from the cross-section of the positive electrode film along the electrode thickness direction, the median L of sphericity is... A50 The value is 0.70-0.85, and can be selected as 0.70-0.

76.

26. The battery cell according to any one of claims 1 to 25, characterized in that, In the cumulative distribution curve of the graphitization degree C value of the positive electrode film obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode, the median C of the graphitization degree is... 50 The value is 0.98-1.20, and can be selected as 1.02-1.10, where the graphitization degree C value is I. G / I D I G This indicates that the Raman spectrum is at 1580±100 cm⁻¹ -1 The intensity of peak G at I D This indicates that the Raman spectrum is at 1350±100 cm⁻¹ -1 The intensity of peak D at that location.

27. The battery cell according to any one of claims 1 to 26, characterized in that, The thickness of the positive electrode current collector is 10μm-17μm, and can be selected as 12μm-15μm.

28. A battery device, characterized in that, The battery device comprises the battery cell according to any one of claims 1 to 27.

29. An electrical appliance, characterized in that, The electrical device includes a battery cell as described in any one of claims 1 to 27 or a battery device as described in claim 28.

30. An energy storage device, characterized in that, The energy storage device includes a battery cell as described in any one of claims 1 to 27 or a battery device as described in claim 28.

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