Battery cell, battery device, and electric device

Abstract

The application relates to a battery monomer, a battery device and a power utilization device. The battery monomer comprises an electrode assembly and an electrolyte; a shell and a top cover assembly, the shell is formed with a containing cavity with an opening, the electrode assembly and the electrolyte are contained in the containing cavity, the top cover assembly covers the opening of the shell, and the top cover assembly is provided with an explosion-proof valve; wherein the electrolyte comprises dimethyl carbonate, a lithium salt containing fluorine and a sulfonic acid group, the mass percentage of the dimethyl carbonate is 16-30%, and the mass percentage of the lithium salt containing fluorine and the sulfonic acid group is 2-6%; the ratio of the area of the explosion-proof valve to the capacity of the battery monomer is 1.0-1.5 mm 2 / Ah. The battery monomer of the application is based on the above materials and structure, and has the characteristics of good energy efficiency and safety performance.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to a battery cell, a battery device, and an electrical device. Background Technology

[0002] With the booming development of new energy vehicles, battery drive systems have become an important factor affecting the performance and cost of new energy vehicles. Due to their high energy density, low memory effect, and high operating voltage, rechargeable batteries have become the preferred power source for battery drive systems.

[0003] Energy efficiency and safety are two critical performance indicators for rechargeable batteries. However, rechargeable batteries using electrolytes often require additives to improve kinetic performance and increase electrolyte conductivity, but this can also introduce the risk of thermal runaway. Therefore, it is difficult to simultaneously achieve optimal energy efficiency and safety performance in a battery. Summary of the Invention

[0004] The purpose of this application is to provide a battery cell, a battery device, and an electrical device, aiming to solve the technical problem of how to make a battery cell have both good energy efficiency and safety performance.

[0005] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0006] In a first aspect, this application provides a battery cell, comprising:

[0007] Electrode assembly and electrolyte;

[0008] A housing and a top cover assembly are provided. The housing has an open receiving cavity in which the electrode assembly and the electrolyte are housed. The top cover assembly covers the opening of the housing and is provided with an explosion-proof valve. The top cover assembly includes a top cover on which the explosion-proof valve is installed. A lower plastic part is provided on the side of the top cover facing the housing. Multiple vent holes are provided in the area of ​​the lower plastic part opposite to the explosion-proof valve. The lower plastic part includes a plastic body and a boss located in the middle of the plastic body. The boss is disposed opposite to the explosion-proof valve and has a gas cavity communicating with the multiple vent holes. The convex surface of the boss is away from the explosion-proof valve.

[0009] The electrolyte comprises dimethyl carbonate and lithium salts containing fluorine and sulfonic acid groups, wherein the mass percentage of dimethyl carbonate is 16%~30%, and the mass percentage of lithium salts containing fluorine and sulfonic acid groups is 2%~6%; the ratio of the area of ​​the explosion-proof valve to the capacity of the battery cell is 1.0~1.5 mm². 2 / Ah.

[0010] The electrolyte of the battery cell in this application contains a certain amount of dimethyl carbonate and lithium salts containing fluorine and sulfonic acid groups. Specifically, through the synergistic effect of 16%~30% dimethyl carbonate and 2%~6% lithium salts containing fluorine and sulfonic acid groups, on the one hand, the electrolyte not only has a lower viscosity but also improves its conductivity, thereby significantly improving the battery's kinetic performance and energy efficiency; on the other hand, the aforementioned proportions of dimethyl carbonate and lithium salts containing fluorine and sulfonic acid groups do not easily generate gas or heat in the electrolyte, thus effectively reducing the risk of thermal runaway. Furthermore, this is combined with the battery top cover assembly having a unit capacity area of ​​1.0~1.5 mm². 2 The explosion-proof valve ( / Ah) provides excellent structural strength and pressure relief / heat dissipation for the battery cell's outer packaging, further reducing the risk of thermal runaway. Therefore, based on the aforementioned materials and structural design, the battery cell of this application possesses both excellent energy efficiency and safety performance.

[0011] In some embodiments, the area of ​​the explosion-proof valve is 780~950 mm². 2 .

[0012] The explosion-proof valve of the above-mentioned area is easy to manufacture on the top cover of the battery cell, has little impact on the structural strength of the top cover, and plays a good role in rapid pressure relief and heat dissipation, so as to reduce the risk of runaway due to rapid heat accumulation inside the battery cell.

[0013] In some embodiments, the capacity of the battery cell is 520~950Ah.

[0014] The battery cells with the above-mentioned capacity are easy to manufacture and can well meet market demand.

[0015] In some embodiments, the electrolyte contains 20% to 26% dimethyl carbonate by mass, and the lithium salt containing fluorine and sulfonic acid groups by mass is 3% to 5%; the ratio of the area of ​​the explosion-proof valve to the capacity of the battery cell is 1.2 to 1.4 mm². 2 / Ah.

[0016] By combining the above-mentioned mass ratio of dimethyl carbonate and fluorinated lithium salt, along with the explosion-proof valve area per unit capacity, the battery cell can better balance energy efficiency and safety performance.

[0017] In some embodiments, the fluorine- and sulfonic acid-containing lithium salt includes at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium trifluoromethylsulfinate.

[0018] The lithium ions in the aforementioned lithium salts containing fluorine and sulfonic acid groups are easily dissociated, giving the electrolyte excellent ion transport properties and thus improving the battery's electrical performance.

[0019] In some embodiments, the top cover assembly includes a top cover on which the explosion-proof valve is mounted, and the top cover has a lower plastic portion disposed on the side facing the housing;

[0020] The area of ​​the lower plastic part opposite to the explosion-proof valve is provided with multiple vent holes.

[0021] By setting a lower plastic section with multiple vent holes on the side of the top cover's explosion-proof valve facing the housing, the heat generated by the battery cells can flow to the explosion-proof valve through the vent holes, allowing for rapid pressure relief and discharge.

[0022] In some embodiments, the total area of ​​the plurality of exhaust holes is 1000~1200 mm². 2 ;

[0023] And / or, the shape of the plurality of exhaust holes includes at least one of circular, elliptical, racetrack-shaped, and polygonal shapes.

[0024] The vents, with the aforementioned total vent area, are positioned on the lower plastic layer. This allows for better pressure relief, reducing the risk of physical explosion of the battery casing. Simultaneously, it enables rapid pressure relief and removes heat from the individual battery cells, thus delaying the escalation of the thermal runaway chain reaction and further mitigating the risk of thermal runaway. The aforementioned vent shape is easy to fabricate on the lower plastic layer, and the vent area can be well controlled.

[0025] In some embodiments, the lower plastic includes a plastic body and a boss located in the middle of the plastic body. The boss is disposed opposite to the explosion-proof valve and has an air chamber communicating with the plurality of vent holes. The convex surface of the boss is away from the explosion-proof valve.

[0026] By setting up protrusions with air chambers connected to the vents, the lower plastic part can construct a directional venting channel and form a guide cavity, allowing high-temperature gas to be concentrated and ejected along a preset path, reducing the risk of disordered diffusion and heat spread. At the same time, such a structure can also serve as physical protection, reducing the risk of solid substances splashed during the depressurization of the explosion-proof valve blocking the depressurization port, thus making it less likely for the temperature and pressure to rise and cause an explosion.

[0027] In some embodiments, the boss is a first boss and a second boss arranged side by side. The first boss has a first air chamber and the second boss has a second air chamber. The first boss and the second boss are arranged opposite each other along the vertical line of the explosion-proof valve and have symmetrical steps. The distance between the first boss and the second boss is 1~4mm.

[0028] The boss consists of a symmetrical first protrusion and a second protrusion, each with an air chamber. This symmetrically constructs an exhaust channel along the center of the explosion-proof valve. High-temperature and high-pressure airflow enters the air chamber from the exhaust port, flows to the explosion-proof valve, and is discharged from the explosion-proof valve. This allows for better uniform flow guidance. At the same time, the stepped boss is less prone to collapse, has a more stable physical structure, and provides a longer-lasting exhaust effect.

[0029] In some embodiments, the plurality of vent holes include a first vent hole, a second vent hole, and a third vent hole, wherein the first vent hole is symmetrically arranged on the convex surfaces of the first protrusion and the second protrusion, the second vent hole is symmetrically arranged on the inclined surfaces between the convex surfaces of the first protrusion and the second protrusion and the step surface, and the third vent hole is symmetrically arranged on the step surfaces of the first protrusion and the second protrusion.

[0030] By symmetrically arranging the first, second, and third vents at three symmetrical positions on the first and second protrusions (sequentially the convex surface, inclined surface, and stepped surface), these symmetrical vents allow the high-temperature gas directionally discharged along the symmetrical positions of the protrusions to be concentrated and ejected through these three types of symmetrical vents, thereby allowing it to flow effectively to the explosion-proof valve for pressure relief and release.

[0031] In some embodiments, the convex surfaces of the first protrusion and the second protrusion are symmetrically provided with a plurality of first air holes, and the area of ​​each first air hole is 40~50mm². 2 The distance between two adjacent first air holes on the same protrusion is 2.5~4mm;

[0032] And / or, the inclined surfaces between the convex surfaces of the first protrusion and the second protrusion and the step surface are symmetrically provided with a plurality of second air holes, each second air hole having an area of ​​14~22mm². 2 The distance between two adjacent second air holes on the same protrusion is 2.5~4mm;

[0033] And / or, the stepped surfaces of the first protrusion and the second protrusion are symmetrically provided with a plurality of the third air holes, each of the third air holes having an area of ​​10~14mm². 2 The distance between two adjacent third vents on the same protrusion is 1~3mm.

[0034] By setting the first, second, and third air holes in the above quantity and size, the impact on the overall mechanical structural strength of the lower plastic is small, and the hot gas that may be generated inside the battery can be evenly vented towards the explosion-proof valve area. By controlling and reducing the speed and intensity of gas ejection, the explosion-proof valve can stably release pressure.

[0035] Secondly, this application provides a battery device, including the battery cell provided in the first aspect of this application.

[0036] The battery device uses a battery cell unique to the embodiments of this application. Based on the characteristic that the battery cell can simultaneously take into account energy density and safety performance, the battery device of this application can store or provide electrical energy very well.

[0037] Thirdly, this application provides an electrical device, including a battery cell according to the first aspect of this application or a battery device according to the second aspect of this application, wherein the battery cell or the battery device is used to store or provide electrical energy.

[0038] The electrical device includes a battery cell or battery device that is unique to the embodiments of this application. Therefore, the electrical device of this application can simultaneously take into account energy density and safety performance, and can work well.

[0039] 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, the following are specific embodiments of this application. Attached Figure Description

[0040] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0041] Figure 1 This is a schematic diagram of the battery cell structure according to an embodiment of this application;

[0042] Figure 2 for Figure 1 The diagram shows an exploded view of a single battery cell.

[0043] Figure 3 This is a cross-sectional view of the top cover assembly in a battery cell according to an embodiment of this application;

[0044] Figure 4 This is a bottom plastic view of a battery cell from the casing toward the top cover assembly, according to an embodiment of this application.

[0045] Figure 5 This is a schematic diagram of one embodiment of the battery module of this application;

[0046] Figure 6 This is an exploded view of the battery pack according to an embodiment of this application;

[0047] Figure 7This is a schematic diagram of one embodiment of an electrical device that uses a secondary battery as a power source, as described in the present application.

[0048] Explanation of reference numerals in the attached figures:

[0049] 10-cell battery;

[0050] 11-Shell;

[0051] 12-Top cover assembly; 120-Top cover; 121-Explosion-proof valve; 122-Lower plastic; 1221-First vent; 1222-Second vent; 1223-Third vent; 1231-Negative electrode adapter; 1232-Positive electrode adapter; 124-Injection port;

[0052] 13-Electrode assembly;

[0053] 20-Battery Module;

[0054] 30 - Battery pack; 31 - Upper casing; 32 - Lower casing. Detailed Implementation

[0055] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0057] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0058] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0059] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0060] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces). "At least one" refers to one or more (including one, two, three, etc.).

[0061] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0062] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0063] With the dwindling availability of traditional energy resources, the development of new energy storage devices is receiving increasing attention. Among these, secondary batteries have garnered significant interest due to their high energy density, high theoretical capacity, excellent cycle stability, and environmental friendliness. Secondary batteries can be applied not only to energy storage systems in hydropower, thermal power, wind power, and solar power plants, but also widely in electric vehicles such as electric bicycles, electric motorcycles, and electric cars. As the application areas of secondary batteries as power batteries continue to expand, the market demand for them is also constantly increasing.

[0064] Lithium-ion batteries are a type of rechargeable battery, and their energy efficiency and safety performance are two crucial evaluation indicators. Battery energy efficiency refers to the percentage of discharged energy to charged energy during a charge-discharge cycle, and it is a core indicator for measuring battery performance. The formula is: (discharge energy / charged energy) × 100%. Thermal runaway is the root cause of lithium-ion battery safety accidents. Overcharging, internal short circuits, or external high temperatures can all trigger a violent chain of exothermic reactions within the battery. When the battery temperature exceeds a certain level, the rate of heat generation increases exponentially, far exceeding the rate of heat dissipation. For example, some batteries experience casing rupture when the temperature exceeds 150°C, leading to combustion and explosion, seriously threatening the safety of applications such as electric vehicles. Thermal runaway prevention requires multi-level coordination.

[0065] Currently, special additives and lithium salts are typically added to the electrolyte to improve the kinetics of individual battery cells and enhance energy efficiency. However, the addition of certain strong oxidizing substances can easily lead to a strong reduction reaction with the fully charged negative electrode when the battery is fully charged, releasing a large amount of heat, triggering thermal runaway, and deteriorating safety performance. Therefore, it is difficult to simultaneously achieve both energy efficiency and safety.

[0066] Based on this, this application develops a battery cell by adding a certain mass ratio of dimethyl carbonate and fluorine- and sulfonic acid-based lithium salts to the electrolyte, and simultaneously setting an explosion-proof valve of a certain area. Based on the above material and structural combination, the battery cell of this application possesses both excellent energy efficiency and safety performance. The specific technical solution is as follows.

[0067] [Battery cell]

[0068] The battery cell in this application embodiment includes a battery casing and electrode components and electrolyte encapsulated within the battery casing. The shape of the battery cell is not particularly limited; it can be cylindrical, square, or any other arbitrary shape. Figure 1 The battery cell 10 shown has a square structure. In this embodiment, the electrode sheets, separator, and negative electrode sheet contained in the battery cell can be formed into electrode assemblies through a winding process and / or a stacking process. The electrode assemblies are encapsulated in a receiving cavity, and the electrolyte is immersed in the electrode assemblies. The number of electrode assemblies contained in the battery cell 10 can be one or more, and can be adjusted according to actual needs.

[0069] In some embodiments, such as Figures 2-4 As shown, the outer packaging of the battery cell 10 may include a housing 11 and a top cover assembly 12. The housing 11 has an open receiving cavity in which the electrode assembly 13 and electrolyte are contained. The housing 11 has an opening communicating with the receiving cavity, and the top cover assembly 12 is used to cover the opening to close the receiving cavity. The top cover assembly 12 is provided with an explosion-proof valve 121, the area of ​​which is 1.0~1.5mm² to the capacity of the battery cell 10.2 / Ah. Specifically, the ratio of the area of ​​the explosion-proof valve 121 to the capacity of the battery cell 10 can be 1.0 mm². 2 / Ah, 1.1mm 2 / Ah, 1.2mm 2 / Ah, 1.3mm 2 / Ah, 1.4mm 2 / Ah, 1.5mm 2 / Ah or any of the above point values, or within the range formed by any two of them.

[0070] The electrolyte comprises dimethyl carbonate (DMC) and lithium salts containing fluorine and sulfonic acid groups. The mass percentage of dimethyl carbonate in the electrolyte is 16% to 30%, and the mass percentage of lithium salts containing fluorine and sulfonic acid groups is 2% to 6%. Specifically, the mass percentage of dimethyl carbonate can be any of the above values ​​or within any combination of 16%, 17%, 18%, 19%, 20%, 22%, 23%, 24%, 25%, 28%, 29%, 30%, etc., and the mass percentage of lithium salts containing fluorine and sulfonic acid groups can be any of the above values ​​or within any combination of 2%, 3%, 4%, 5%, 6%, etc., etc.

[0071] Dimethyl carbonate can reduce electrolyte viscosity, but it has poor thermal stability. Lithium ions in lithium salts containing fluorine and sulfonic acid groups are easily dissociated, but they generally have strong oxidizing defects. In order to make the battery cell have both good energy efficiency and safety performance, it is difficult to control the amount of both added to the electrolyte.

[0072] In this embodiment, dimethyl carbonate and fluorinated and sulfonic acid-based lithium salts not only synergistically reduce the viscosity of the electrolyte, increase the ionic conductivity of the electrolyte, and lower the lithium-ion transport barrier, thereby improving the kinetics of the battery cell and increasing the energy efficiency of the cell, but also minimize the release of large amounts of heat from the battery cell, reducing the risk of thermal runaway. Experiments in this application have shown that adding 16%–30% dimethyl carbonate and 2%–6% fluorinated and sulfonic acid-based lithium salts to the electrolyte of the battery cell can significantly improve the energy efficiency of the battery cell 10 while minimizing the risk of thermal runaway. Furthermore, the top cover assembly 12 of the battery cell 10 has a unit capacity area of ​​1.0–1.5 mm². 2 The explosion-proof valve 121 of / Ah provides excellent structural strength and pressure relief / heat dissipation for the outer packaging of the battery cell 10, thereby further reducing the risk of thermal runaway of the battery cell. Therefore, based on the above-mentioned materials and structural design, the battery cell 10 of this application embodiment possesses both excellent energy efficiency and safety performance.

[0073] The explosion-proof valve 121 is a battery safety protection device used to prevent the battery from exploding under abnormal conditions. It is an important component of the battery, automatically opening to release internal pressure when the internal pressure is too high. The ratio of the area of ​​the explosion-proof valve 121 to the capacity of the battery cell 10 refers to the ratio of the projected area S of the explosion-proof valve 121 along the height direction of the battery cell 10 to the capacity C of the battery cell 10, satisfying: 1.0 mm². 2 / Ah≤S / C≤1.5mm 2 / Ah. By combining the above-mentioned electrolyte with a suitable explosion-proof valve 121 per unit area, the pressure relief and rapid heat dissipation functions are effectively achieved, further reducing the risk of thermal runaway of the battery cell 10.

[0074] In some embodiments, the fluorinated and sulfonic acid-based lithium salt in the electrolyte includes at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium trifluoromethylsulfinate. The lithium ions in these fluorinated and sulfonic acid-based lithium salts readily dissociate, giving the electrolyte excellent ion transport properties and thus improving the battery's electrical performance. Furthermore, by combining this with the aforementioned dimethyl carbonate and the area-to-capacity ratio of the explosion-proof valve, the battery cell can achieve both excellent energy efficiency and safety performance.

[0075] Furthermore, the electrolyte may also contain a primary lithium salt, such as lithium hexafluorophosphate, with a concentration of 0.8~1.2 mol / L; while 2%~6% of the lithium salt containing fluorine and sulfonic acid groups in the electrolyte may be lithium bisfluorosulfonylimide (LiFSI), that is, lithium bisfluorosulfonylimide and lithium hexafluorophosphate are selected to form a lithium salt in the electrolyte.

[0076] In some embodiments, the area of ​​the explosion-proof valve 121 is 780~950 mm². 2 Specifically, the area of ​​the explosion-proof valve 121 can be 780 mm². 2 800mm 2 820mm 2 850mm 2 860mm 2 880mm 2 900mm 2 920mm 2 940mm 2 950mm 2 The value of any of the above points or within the range formed by any two of them.

[0077] The appropriate area of ​​the explosion-proof valve 121 has little impact on the structural strength of the top cover assembly 12; at the same time, the weld between the explosion-proof valve 121 and the top cover assembly 12 is appropriate and less prone to weld defects. Therefore, the embodiment of this application provides an explosion-proof valve 121 of the aforementioned area on the top cover assembly 12 of the battery cell 10, which has good manufacturability, minimal impact on the structural strength of the top cover, and plays a good role in rapid pressure relief and heat dissipation, which can effectively reduce the risk of runaway due to rapid heat accumulation inside the battery cell 10.

[0078] In some embodiments, the capacity of the battery cell 10 is 520~950Ah. Specifically, the capacity of the battery cell 10 can be any of the above values ​​or within any range of any combination thereof, such as 520Ah, 550Ah, 580Ah, 600Ah, 620Ah, 650Ah, 680Ah, 700Ah, 720Ah, 750Ah, 780Ah, 800Ah, 850Ah, 860Ah, 880Ah, 900Ah, 920Ah, 940Ah, and 950Ah. Battery cells with the above capacities are easy to manufacture and can well meet market demands.

[0079] In some embodiments, the electrolyte contains 20% to 26% dimethyl carbonate by mass, and 3% to 5% fluorinated lithium salts such as lithium bis(fluorosulfonyl)imide by mass; the ratio of the area of ​​the explosion-proof valve 121 to the capacity of the battery cell 10 is 1.2 to 1.4 mm². 2 / Ah. By further selecting the above-mentioned mass ratio of dimethyl carbonate and lithium bis(fluorosulfonyl)imide, and combining the above-mentioned explosion-proof valve area per unit capacity, the battery cell can better balance energy efficiency and safety performance.

[0080] In some embodiments, the top cover assembly 12 includes a top cover 120 on which an explosion-proof valve 121 is installed, and a lower plastic 122 is provided on the side of the top cover 120 facing the housing 11; wherein, a plurality of vent holes are provided in the area of ​​the lower plastic 122 opposite to the explosion-proof valve 121.

[0081] After the explosion-proof valve 121 is opened to release pressure, the high temperature and high pressure airflow generated by thermal runaway of the battery cell 10 are mainly concentrated in the area of ​​the explosion-proof valve 121. Multiple vent holes are provided in the area of ​​the lower plastic 122 opposite to the explosion-proof valve 121. These vent holes connect the inside of the battery and the explosion-proof valve 121, so that the heat generated by the battery cell 10 can flow to the explosion-proof valve 121 through the vent holes and be quickly released by the explosion-proof valve 121.

[0082] In some embodiments, the total area of ​​the plurality of vent holes in the lower plastic 122 is 1000~1200 mm². 2 Specifically, the total area of ​​the multiple vent holes is 1000 mm². 2 1020mm 21050mm 2 1080mm 2 1100mm 2 1120mm 2 1140mm 2 1150mm 2 1160mm 2 1180mm 2 1200mm 2 The value is equal to or falls within the range of any of the above points or any combination thereof. The total vent area refers to the sum of the vent areas of all vents arranged on the lower plastic 122. The vents are arranged on the lower plastic 122 with the total vent area, which can better relieve pressure and reduce the risk of physical explosion of the battery casing. At the same time, it can remove the internal heat of the battery cell 10 through rapid pressure relief, thereby delaying the expansion of the thermal runaway chain reaction and reducing the risk of thermal runaway.

[0083] In some embodiments, the vent shapes of the plurality of vent holes in the lower plastic 122 include at least one of circular, elliptical, racetrack-shaped, and polygonal shapes. These vent shapes are easily fabricated on the lower plastic and allow for good control of the ventilation area of ​​the vent holes.

[0084] In some embodiments, the lower plastic 122 includes a plastic body and a boss located in the middle of the plastic body. The boss is disposed opposite to the explosion-proof valve 121 and has a gas cavity communicating with multiple vent holes. The convex surface of the boss is away from the explosion-proof valve 121; that is, the boss protrudes away from the explosion-proof valve 121 and protrudes towards the electrode assembly 13 inside the battery cell 10. The protruding boss can form a gas cavity communicating with multiple vent holes. Through this boss, the lower plastic 122 can construct a directional exhaust channel and form a guide cavity, so that high-temperature gas can be concentrated and ejected along a preset path, reducing the risk of disordered diffusion and heat spread. At the same time, such a boss structure can also serve as physical protection, reducing the risk of solid substances splashed when the explosion-proof valve 121 is depressurized blocking the depressurization port, thereby making it less likely for the temperature and pressure to rise and cause an explosion.

[0085] Specifically, in this embodiment, an electrolyte with an area of ​​780~950 mm² is introduced based on the use of an electrolyte with a certain concentration of DMC and LiFSI. 2 The large-area explosion-proof valve 121 and the protrusion of the lower plastic 122 are used to construct a directional exhaust channel to achieve directional pressure relief and rapid heat dissipation, reduce heat spread, and thus significantly improve the safety of the battery.

[0086] In some embodiments, the boss consists of a first protrusion and a second protrusion arranged side by side. Each of the first and second protrusions has a gas chamber communicating with the exhaust port; that is, the first protrusion has a first gas chamber, and the second protrusion has a second gas chamber. The first and second protrusions are arranged opposite each other along the vertical line of the explosion-proof valve 121 and have symmetrical steps, and the distance t between the first and second protrusions is 1~4mm. The lower plastic 122 is a raised structure directly below the explosion-proof valve 121. The boss of the lower plastic 122 is composed of symmetrical first and second protrusions, each with a gas chamber. This symmetrically constructs an exhaust channel along the center of the explosion-proof valve. High-temperature and high-pressure airflow enters the gas chamber from the exhaust port, flows to the explosion-proof valve, and exits from the explosion-proof valve, thereby achieving better uniform flow guidance. At the same time, the stepped boss is less prone to collapse, has a more stable physical structure, and provides a longer-lasting exhaust effect. For example, the boss can be vertically divided into a first protrusion and a second protrusion arranged side by side along the vertical line of the explosion-proof valve 121.

[0087] In some embodiments, the plurality of vent holes of the lower plastic 122 include a first vent 1221, a second vent 1222 and a third vent 1223, wherein the convex surfaces of the first protrusion and the second protrusion are symmetrically provided with the first vent 1221, the inclined surfaces between the convex surfaces of the first protrusion and the second protrusion and the step surface are symmetrically provided with the second vent 1222, and the step surfaces of the first protrusion and the second protrusion are symmetrically provided with the third vent 1223.

[0088] The lower plastic 122 has a raised structure directly below the explosion-proof valve 121, consisting of a symmetrical first protrusion and a second protrusion. The first vent 1221, the second vent 1222, and the third vent 1223 are symmetrically arranged at three positions on the symmetrical first and second protrusions: the convex surface, the inclined surface, and the stepped surface. These symmetrical vents allow the high-temperature gas discharged along the protrusion to be concentrated and ejected through these three types of symmetrical vents, so that it can flow well to the explosion-proof valve 121 for pressure relief and release.

[0089] For example, the convex surface of the first convex body is provided with a row of first vent holes 1221, and the convex surface of the second convex body is provided with a row of first vent holes 1221. These two rows of first vent holes 1221 are symmetrically arranged, that is, they are the same size, shape, and spacing. The inclined surface of the first convex body is provided with a row of second vent holes 1222, and the inclined surface of the second convex body is provided with a row of second vent holes 1222. These two rows of second vent holes 1222 are symmetrically arranged, that is, they are the same size, shape, and spacing. The stepped surface area of ​​the first convex body is provided with a row of third vent holes 1223, and the stepped surface area of ​​the second convex body is provided with a row of third vent holes 1223. These two rows of third vent holes 1223 are symmetrically arranged, that is, they are the same size, shape, and spacing. The high-temperature gas generated inside the battery cell 10 is concentrated and ejected through these three types of symmetrical vent holes, so that it can flow effectively to the explosion-proof valve 121 for pressure relief and release.

[0090] In some embodiments, the top cover assembly 12 is further provided with electrode adapters for connecting the electrode tabs of the electrode assembly 13, specifically including a negative electrode adapter 1231 and a positive electrode adapter 1232. The top cover assembly 12 is also provided with an injection hole 124 for injecting electrolyte into the battery cell 10.

[0091] The shapes of the multiple vent holes include at least one of circular, elliptical, racetrack-shaped, and polygonal shapes. A racetrack-shaped vent resembles a racetrack, while a polygon can be irregular or regular. For ease of fabrication and control of the vent area, regular polygons such as equilateral triangles, squares, and rectangles can be used. The vent holes can be evenly arranged along the width of the battery cell 10 on the lower plastic 122. For ease of fabrication and control of the vent area, the vent holes are all circular. In some embodiments, to improve ventilation efficiency, the first vent 1221 can be racetrack-shaped, the second vent 1222 can be elliptical, and the third vent 1223 can be circular.

[0092] In some embodiments, the convex surfaces of the first protrusion and the second protrusion are symmetrically provided with a plurality of first air holes 1221, and the area of ​​each first air hole 1221 is 40~50mm². 2 The distance between two adjacent first air holes 1221 on the same convex body is 2.5~4mm. That is, the area of ​​each first air hole 1221 on the convex surface of the first convex body is 40~50mm². 2 The spacing between two adjacent first air holes 1221 is 2.5~4mm, and the area of ​​each first air hole 1221 on the convex surface of the second protrusion is 40~50mm². 2 The distance between two adjacent first air holes 1221 is 2.5~4mm, and the first air holes 1221 on the first protrusion and the first air holes 1221 on the second protrusion are symmetrically arranged.

[0093] In some embodiments, a plurality of second air holes 1222 are symmetrically provided on the inclined surfaces between the convex surfaces of the first and second protrusions and the stepped surfaces, and the area of ​​each second air hole 1222 is 14~22mm². 2 The spacing between two adjacent second vents 1222 on the same convex body is 2.5~4mm. That is, the area of ​​each second vent 1222 set on the inclined surface between the convex surface and the stepped surface of the first convex body is 14~22mm². 2 The spacing between two adjacent second vents 1222 is 2.5~4mm, and the area of ​​each second vent 1222 on the inclined surface between the convex surface and the step surface of the second protrusion is 14~22mm². 2The distance between two adjacent second air holes 1222 is 2.5~4mm, and the second air holes 1222 on the first protrusion and the second air holes 1222 on the second protrusion are symmetrically arranged.

[0094] In some embodiments, the stepped surfaces of the first protrusion and the second protrusion are symmetrically provided with a plurality of third vents 1223, and the area of ​​the third vents 1223 is 10~14mm². 2 The spacing between two adjacent third vents 1223 on the same protrusion is 1~3mm. That is, the area of ​​each third vent 1223 on the step surface of the first protrusion is 10~14mm². 2 The spacing between two adjacent third vents 1223 is 1~3mm, and the area of ​​each third vent 1223 on the platform surface of the second protrusion is 10~14mm². 2 The spacing between two adjacent third air holes 1223 is 1~3mm, and the third air holes 1223 on the first protrusion and the third air holes 1223 on the second protrusion are symmetrically arranged. The stepped surfaces of the first protrusion and the second protrusion can be small arc platforms, corresponding to the arc positions on both sides of the explosion-proof valve 121.

[0095] It should be noted that the spacing between pores mentioned above refers to the shortest distance between two points on the respective edges of two adjacent pores.

[0096] By setting the first vent 1221, the second vent 1222, and the third vent 1223 in the above quantity and size, the impact on the overall mechanical strength of the lower plastic is small, and the hot gas that may be generated inside the battery can be evenly vented towards the explosion-proof valve area. By controlling and reducing the speed and intensity of gas ejection, the explosion-proof valve can stably release pressure.

[0097] The electrolyte includes an organic solvent, which may further include one or more of the following: chain carbonates, cyclic carbonates, and carboxylic acid esters. There are no specific restrictions on the types of chain carbonates, cyclic carbonates, and carboxylic acid esters; they can be selected according to actual needs. The organic solvent may also include one or more of the following: diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethylene carbonate, butenyl carbonate, γ-butyrolactone, methyl formate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl propionate, and tetrahydrofuran.

[0098] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0099] For example, the electrolyte may also use other additives besides lithium salts containing fluorine and sulfonic acid groups (e.g., lithium difluorosulfonylimide), selected from at least one of cyclic carbonate compounds containing unsaturated bonds, halogen-substituted cyclic carbonate compounds, sulfate compounds, sulfite compounds, sulfonolactone compounds, disulfonic acid compounds, nitrile compounds, aromatic compounds, isocyanate compounds, phosphonitrile compounds, cyclic anhydride compounds, phosphite compounds, phosphate compounds, borate ester compounds, and carboxylic acid ester compounds.

[0100] This application provides a battery cell. The battery cell of this application 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 negative electrode film layer contains a negative electrode active material. As an example, the negative electrode active material can be a negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material can include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials can be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0101] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0102] In some embodiments, the negative electrode film layer of the negative electrode sheet may optionally include a conductive agent and 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). 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.

[0103] In some embodiments, the negative electrode film layer comprises the following weight percentages, based on the total weight of 100%: 92-99% negative electrode active material, 0.5-4% conductive agent, and 0.5-4% binder.

[0104] In some embodiments, a single battery cell includes a positive electrode and a negative electrode.

[0105] In some embodiments, 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 current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0106] In some embodiments, the positive electrode film contains a positive electrode active material, which may include positive electrode active materials known in the art for use in batteries. As an example, the positive electrode active material of a lithium-ion secondary battery may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. The positive electrode active material accounts for 90-99% by weight in the positive electrode film, based on the total weight of the positive electrode film.

[0107] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder in the positive electrode film layer may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of PVDF-tetrafluoroethylene-propylene, a terpolymer of PVDF-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorinated acrylate resin. The binder accounts for 0.5-5% by weight of the positive electrode film layer, based on the total weight of the positive electrode film layer.

[0108] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, carbon black (e.g., acetylene black or Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive agent accounts for 0.5-5% by weight of the positive electrode film, based on the total weight of the positive electrode film.

[0109] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0110] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0111] In one embodiment, the separator may be made of materials known in the art for battery separators. As an example, the separator base film may include one or more of polyethylene film, polypropylene film, and polyvinylidene fluoride film.

[0112] [Battery Device]

[0113] This application provides a battery device. Specifically, the battery device includes a single battery cell according to embodiments of this application.

[0114] The battery device uses a battery cell unique to the embodiments of this application. Based on the advantages of the battery cell in simultaneously achieving energy density and safety performance, the battery device of this application can effectively store or provide electrical energy.

[0115] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0116] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0117] In some embodiments, the battery device may include any one of a battery cell, a battery module, or a battery pack.

[0118] The method for preparing the battery cell 10 is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form the battery cell 10. As an example, the positive electrode, the separator, and the negative electrode can be formed into an electrode assembly 13 by a winding process or a stacking process. The electrode assembly 13 is placed in an outer packaging, dried, and then injected with an electrolyte. After vacuum sealing, settling, formation, and shaping processes, the battery cell 10 is obtained.

[0119] A battery module is assembled from the battery cell 10, which means it can contain multiple battery cells 10. The specific number can be adjusted according to the application and capacity of the battery module.

[0120] In some embodiments, Figure 5 This is a schematic diagram of battery module 20 as an example. (See diagram for example.) Figure 5 As shown, in the battery module 20, multiple battery cells 10 can be arranged sequentially along the length of the battery module 20. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 10 can be fixed in place using fasteners.

[0121] Optionally, the battery module 20 may also include a housing with a receiving space in which multiple battery cells 10 are received.

[0122] A battery pack refers to an assembly of the aforementioned battery cells 10, meaning it can contain multiple battery cells 10. These multiple battery cells 10 can be assembled into the aforementioned battery module 20. The specific number of battery cells 10 or battery modules 20 contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0123] As in the example, Figure 6 This is a schematic diagram of a battery pack 30 as an example. The battery pack 30 may include a battery compartment and multiple battery modules 20 disposed within the battery compartment. The battery compartment includes an upper compartment 31 and a lower compartment 32. The upper compartment 31 covers the lower compartment 32, forming a closed space for accommodating the battery modules 20. The multiple battery modules 20 can be arranged in any manner within the battery compartment.

[0124] Electrical appliances

[0125] This application provides an electrical device. Specifically, the electrical device includes a battery cell or a battery device according to embodiments of this application, wherein the battery cell or battery device is used to store or provide electrical energy.

[0126] The electrical device includes battery cells or battery devices unique to the embodiments of this application. Therefore, the electrical device of this application has the characteristic of high energy density and can work better.

[0127] Electrical devices can be, but are not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. The type of battery used in these devices can be selected from individual battery cells, battery modules, or battery packs based on their usage requirements.

[0128] Figure 7 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0129] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use rechargeable batteries as their power source.

[0130] Example

[0131] 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.

[0132] Example 1

[0133] A battery cell contains an electrode assembly and an electrolyte, and is packaged in a casing and a top cover assembly. The housing has an open receiving cavity in which the electrode assembly and electrolyte are housed. A top cover assembly covers the opening of the housing. The top cover assembly includes a top cover on which an explosion-proof valve is installed. A lower plastic part is provided on the side of the top cover facing the housing. The lower plastic part includes a plastic body and a boss. The boss is positioned opposite to the explosion-proof valve and protrudes away from the explosion-proof valve. The boss has a step, and the surface between the boss and the step is inclined. The boss is composed of a first protrusion and a second protrusion arranged side by side. The first protrusion has a first air chamber, and the second protrusion has a second air chamber. The first and second protrusions are positioned opposite each other along the vertical line of the explosion-proof valve and have symmetrical steps. The distance between the first and second protrusions is t=2mm. Multiple vent holes (communicating with the air chambers) are provided in the area of ​​the lower plastic part opposite to the explosion-proof valve: first vent holes symmetrically arranged on the convex surfaces of the first and second protrusions, second vent holes symmetrically arranged on the inclined surfaces of the first and second protrusions, and third vent holes symmetrically arranged on the step surfaces of the first and second protrusions. The specific number and dimensions are shown in Table 1.

[0134] The electrolyte consists of dimethyl carbonate and lithium bis(fluorosulfonyl)imide, with dimethyl carbonate accounting for 22% by mass and lithium bis(fluorosulfonyl)imide accounting for 4% by mass; the explosion-proof valve has an area of ​​840 mm². 2 The ratio of the capacity of the battery cell to the capacity of the individual cells is 1.3 mm. 2 / Ah.

[0135] The preparation steps of this battery cell are as follows:

[0136] (1) Positive electrode plate

[0137] The positive electrode active materials lithium iron phosphate, polyvinylidene fluoride and conductive carbon black are mixed in a weight ratio of 97:2.2:0.8 and then added to the solvent N-methylpyrrolidone. The mixture is stirred evenly and the viscosity is adjusted to form a positive electrode slurry. The positive electrode slurry is coated on both sides of the positive electrode current collector aluminum foil to form a positive electrode film layer. After drying, cold pressing and slitting, the positive electrode sheet is obtained.

[0138] (2) Negative electrode plate

[0139] A negative electrode active material (graphite), a conductive agent (Super P), a binder (styrene-butadiene rubber (SBR), and a thickener (sodium carboxymethyl cellulose (CMC-Na)) were mixed in a mass ratio of 95.5:1.0:2.0:1.5. Deionized water was added and stirred to disperse the mixture into a negative electrode slurry. The negative electrode slurry was then coated onto both sides of a Cu foil, and after drying, compaction, slitting, and sheet preparation, a negative electrode sheet was obtained.

[0140] (3) Separating membrane

[0141] A 7μm polyethylene-based membrane is used as a separator, with an inorganic ceramic coating and a dotted dispersed organic polymer coating on both sides.

[0142] (4) Electrolyte

[0143] In an argon-atmospheric glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed thoroughly. Lithium hexafluorophosphate and lithium difluorosulfonyl imide were then added and dissolved in the organic solvent. The mixture was stirred until the electrolyte contained 22% dimethyl carbonate, 4% lithium difluorosulfonyl imide, and 0.82 mol / L lithium hexafluorophosphate, yielding the electrolyte of Example 1.

[0144] (5) Battery assembly

[0145] The positive electrode, separator, and negative electrode are stacked in sequence and then wound to obtain an electrode assembly. One end of the positive electrode, negative electrode, and separator is fixed to the discharge roller, and the other end is stacked together and fixed to the winding shaft. The winding shaft is rotated by a motor to wind the positive electrode, negative electrode, and separator. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained.

[0146] Example 2-11

[0147] One type of battery cell differs from Example 1 in Table 1, but is otherwise identical to Example 1.

[0148] Comparative Examples 1-5

[0149] One type of battery cell differs from Example 1 in Table 1, but is otherwise identical to Example 1.

[0150] [Battery Performance Test]

[0151] (1) Energy efficiency test:

[0152] At 25℃ and normal pressure, the battery cell under test was charged to 3.65V at a power of 0.25P, allowed to stand for 10 minutes, and then discharged to 2.5V at a power of 0.25P, allowed to stand for 10 minutes, and this charge-discharge cycle was repeated 3 times. The energy efficiency of the last two cycles was calculated, and the average value was recorded as the energy efficiency of the cell at 0.25P.

[0153] Energy efficiency per cycle = (discharge energy / charge energy) × 100%.

[0154] (2) Thermal runaway test:

[0155] Thermal runaway testing was conducted according to GB / T-36276-2023: At 25℃ and normal pressure, the battery cells were charged at 0.33C to 3.65℃. Then, they were charged at a constant current of 0.5C while simultaneously heating the battery cells to trigger thermal runaway. After thermal runaway, charging and heating were terminated, and the cells were observed for 1 hour. The highest surface temperature of the battery cells was recorded, as well as whether the cells caught fire or exploded.

[0156] The results are shown in Table 1.

[0157] Table 1

[0158]

[0159] Table 1 shows that: in Comparative Example 1, the energy efficiency of the battery cell is relatively low because the mass percentage of dimethyl carbonate is 15%, which is lower than the 16%~30% range; in Comparative Example 2, the maximum temperature on the back side of the battery cell during thermal runaway is significantly increased because the mass percentage of dimethyl carbonate is 32%, which is higher than the 16%~30% range; in Comparative Example 3, the energy efficiency of the battery cell is relatively low because the mass percentage of lithium difluorosulfonylimide is 1%, which is lower than the 2%~6% range; in Comparative Example 4, the maximum temperature on the back side of the battery cell during thermal runaway is significantly increased because the mass percentage of lithium difluorosulfonylimide is 8%, which is higher than the 2%~6% range; and in Comparative Example 5, the ratio of the area of ​​the explosion-proof valve to the capacity of the battery cell is low, at 0.4 mm². 2 / Ah, the maximum temperature on the back of the battery cell increases significantly due to thermal runaway, and thermal runaway fire occurs. In Examples 1-12 of this application, the mass percentage of dimethyl carbonate in the electrolyte is in the range of 16% to 30%, the mass percentage of lithium bis(fluorosulfonyl)imide is in the range of 2% to 6%, and the ratio of the area of ​​the explosion-proof valve to the capacity of the battery cell is 1.0 to 1.5 mm². 2 Within the / Ah range, battery cells can achieve both excellent energy efficiency and safety performance. Furthermore, within this range, the mass ratio of dimethyl carbonate, the mass ratio of lithium bis(fluorosulfonyl)imide, the ratio of the explosion-proof valve area to the battery cell capacity, and even the number and size of the first, second, and third vents, as well as the total area of ​​the vent holes, can be optimized to further improve the energy efficiency and safety performance of the battery cells.

[0160] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A battery cell, characterized by, The battery monomer comprises: an electrode assembly and an electrolyte; a shell and a top cover assembly, the shell is formed with a containing cavity with an opening, the electrode assembly and the electrolyte are contained in the containing cavity, the top cover assembly covers the opening of the shell, the top cover assembly is provided with an explosion-proof valve; the top cover assembly comprises a top cover on which the explosion-proof valve is mounted, the top cover is provided with a lower plastic on the side facing the shell, a plurality of exhaust holes are arranged in the area opposite to the explosion-proof valve of the lower plastic; the lower plastic comprises a plastic body and a boss located in the middle of the plastic body, the boss is arranged opposite to the explosion-proof valve and has a gas cavity communicating with the plurality of exhaust holes, the convex surface of the boss is away from the explosion-proof valve; the boss is a first convex body and a second convex body arranged side by side, the first convex body has a first gas cavity, the second convex body has a second gas cavity, the first convex body and the second convex body are arranged opposite along the median line of the explosion-proof valve and have symmetrical steps, and the distance between the first convex body and the second convex body is 1-4mm. The electrolyte comprises dimethyl carbonate, fluorine-containing and sulfonic acid group lithium salt, the mass percentage of the dimethyl carbonate is 16-30%, the mass percentage of the fluorine-containing and sulfonic acid group lithium salt is 2-6%; the ratio of the area of the explosion-proof valve to the capacity of the battery monomer is 1.0-1.5 mm 2 / Ah.

2. The battery cell of claim 1, wherein, The area of the explosion-proof valve is 780-950 mm 2 .

3. The battery cell of claim 1, wherein, The capacity of the battery monomer is 520-950Ah.

4. The battery cell of claim 1, wherein, The mass percentage of the dimethyl carbonate in the electrolyte is 20-26%, and the mass percentage of the lithium salt containing fluorine and sulfonic acid group is 3-5%; the ratio of the area of the explosion-proof valve to the capacity of the battery monomer is 1.2-1.4 mm 2 / Ah.

5. The battery cell of claim 1, wherein, The lithium salt containing fluorine and sulfonic acid group comprises at least one of lithium bisfluorosulfonylimide, lithium bistrifluoromethylsulfonylimide and lithium trifluoromethylsulfinate.

6. The battery cell of any one of claims 1-5, wherein, The total hole area of the plurality of exhaust holes is 1000-1200mm 2 ; And / or, the hole shape of the plurality of exhaust holes comprises at least one of a circular shape, an elliptical shape, a racetrack shape and a polygonal shape.

7. The battery cell according to any one of claims 1-5, characterized in that, The plurality of exhaust holes comprises a first gas hole, a second gas hole and a third gas hole, wherein the convex surface of the first convex body and the second convex body is symmetrically provided with the first gas hole respectively, the inclined surface between the convex surface and the step surface of the first convex body and the second convex body is symmetrically provided with the second gas hole respectively, and the step surface of the first convex body and the second convex body is symmetrically provided with the third gas hole respectively.

8. The battery cell of claim 7, wherein the cathode comprises a lithium metal oxide. The convex surfaces of the first convex body and the second convex body are respectively symmetrically provided with a plurality of first air holes, and the area of each first air hole is 40-50 mm 2 The interval between the adjacent two first air holes of the same convex body is 2.5-4 mm. And / or, the slope between the convex surface of the first convex body and the second convex body and the step surface is respectively provided with a plurality of the second air holes, the area of each second air hole is 14-22mm 2 The interval between the adjacent two second air holes of the same convex body is 2.5-4mm. And / or, the stepped surface of the first convex body and the second convex body is respectively symmetrically provided with a plurality of third air holes, the area of each third air hole is 10-14 mm 2 The distance between the adjacent two third air holes of the same convex body is 1-3 mm.

9. A battery device characterized by comprising: The battery monomer comprises the battery monomer of any one of claims 1-8.

10. An electrical device, characterized by The battery monomer or the battery device of claim 9 is used for storing or providing electric energy.

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