Battery casing and individual cells

Abstract

This invention provides a battery casing and a single battery cell. The battery casing includes an inner shell, an outer shell, and a cover plate. The inner shell has a receiving cavity with an open end. The outer shell is fitted over the inner shell and connected to it, forming a cavity filled with a functional liquid between the outer shell and the inner shell. The cover plate is sealed to the open end of the inner shell. The cavity between the outer shell and the inner shell is filled with a functional liquid; and / or, the cover plate has an inner cavity filled with a functional liquid. The functional liquid includes a flame-retardant liquid and / or a thermally conductive liquid, which exchanges heat with the internal battery cell through the inner shell wall or the inner wall of the cover plate and is physically isolated from the electrolyte. This invention externalizes thermal management and flame-retardant functions from the electrochemical system to the battery casing structure, ensuring a high safety level for the single battery cell while avoiding the negative impact of traditional electrolyte additives on performance, thereby simultaneously improving battery rate performance, cycle life, and energy density.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a battery casing and a single battery cell. Background Technology

[0002] With the rapid development of the new energy industry, the requirements for battery safety performance have been elevated to an unprecedented strategic level. Currently, battery safety protection largely relies on system-level engineering design and external protection at the battery stack / pack and module levels. For example, high-strength aluminum alloy or composite material structural components are added to resist mechanical impact. Multi-channel liquid cooling or direct cooling thermal management systems are installed inside the battery stack / pack to suppress the propagation path of thermal runaway. Functional additives are added to create a more stable electrode / electrolyte interface to improve the thermal stability and flame retardancy of the electrolyte itself. However, adding structural components increases the overall weight of the battery stack / pack and module, reduces energy density, and increases system complexity and cost. Furthermore, installing thermal management systems inside the battery stack / pack not only occupies a large amount of space but also poses potential risks such as refrigerant leakage and pipeline blockage; the introduction of functional additives may affect the consistency of electrochemical performance and long-term cycle stability. Moreover, none of the above system-level protection measures can fundamentally improve the impact resistance and heat diffusion resistance of individual cells, resulting in the risk of safety failure under extreme operating conditions. Summary of the Invention

[0003] The main objective of this invention is to provide a battery casing and a single battery cell, aiming to solve the technical problem of how to ensure the performance of the single battery cell while improving its safety.

[0004] To achieve the above objectives, the present invention provides a battery casing suitable for accommodating battery cells, the battery casing comprising: The inner shell has a receiving cavity with an opening at one end for accommodating the battery cell; An outer shell is fitted over the inner shell and connected to the inner shell, and there is a cavity between the outer shell and the inner shell, which is filled with a functional liquid; A cover plate, which is sealed to the opening end of the inner shell, is used to close the receiving cavity; Wherein, a cavity exists between the outer shell and the inner shell, and at least one wall surface of the inner shell facing the outer shell contacts the cavity, the cavity being filled with a functional liquid; and / or The cover plate has an inner cavity filled with a functional liquid.

[0005] In some embodiments, the functional liquid includes a flame-retardant liquid and / or a thermally conductive liquid.

[0006] In some embodiments, the filling volume of the functional liquid in the cavity and / or the inner cavity is not less than 5% of the total volume of the cavity and / or the inner cavity.

[0007] In some embodiments, the cavity has a dimension of 0.1 mm to 15 mm in the direction from the inner shell to the outer shell; And / or, The inner cavity has a dimension of 0.1 mm to 15 mm along the direction from the cover plate toward the interior of the receiving cavity.

[0008] In some embodiments, a cavity is provided between the outer shell and the inner shell, and an inner cavity is provided inside the cover plate, wherein the cavity and the inner cavity are independently arranged.

[0009] In some embodiments, the battery housing is further provided with a liquid injection hole, which is disposed on the cover plate and communicates with the inner cavity. The liquid injection hole is also disposed on the outer shell and communicates with the cavity. The liquid injection hole is used to inject the functional liquid into the inner cavity and the cavity. The battery housing also includes a sealing structure for sealing the injection hole after the functional liquid is injected.

[0010] In some embodiments, the cover plate has an inner cavity, and the cover plate also has an electrode post for electrical connection with the battery cell. The electrode post passes through the cover plate and extends into the receiving cavity. An insulating seal is provided between the electrode post, the cover plate, and the functional liquid filled in the inner cavity. The insulating seal is used to block the electrical connection between the electrode post, the cover plate, and the functional liquid.

[0011] In some embodiments, the cavity is provided with a reinforcing structure, which is connected to the inner shell and / or the outer shell to enhance the structural rigidity between the inner shell and the outer shell.

[0012] In some embodiments, the outer shell has a port communicating with the opening, the inner shell includes a body portion and a mounting portion, the body portion defining the receiving cavity, and the mounting portion being connected to the body portion and disposed around the edge of the opening; The mounting portion includes a first connecting section, which is bent relative to the body portion away from the receiving cavity and connected to the edge of the port; or The mounting portion includes a first connecting segment and a second connecting segment. The first connecting segment is bent away from the body portion in a direction away from the receiving cavity and connected to the edge of the port. One end of the second connecting segment is connected to the first connecting segment and bent relative to the first connecting segment. The second connecting segment is welded to the surface of the outer shell away from the inner shell.

[0013] A second aspect of the present invention also provides a single-cell battery, comprising: Battery cell; Electrolyte; and In any of the above embodiments, the battery casing contains the battery cell and the electrolyte within the receiving cavity.

[0014] Compared with the prior art, the beneficial effects of the present invention are: In the technical solution of this invention, by providing a cavity / inner cavity filled with functional liquid (such as flame retardant liquid or thermal conductive liquid) between the inner shell and the outer shell, and / or inside the cover plate, an independent, efficient, and physically isolated safety barrier is added to the individual battery cell. This allows the individual battery cell to perform rapid thermal management (heat dissipation, temperature equalization) and / or flame retardant isolation through the internal functional liquid without relying on external systems when subjected to external impact or in the early stages of internal thermal runaway. This cuts off the thermal runaway chain reaction at the most basic unit level, greatly improving the intrinsic safety level of the battery.

[0015] Compared to related technologies that add flame retardants to the electrolyte to improve safety, the solution in this application separates the flame-retardant function from the electrolyte and places it in the outer casing layer. This allows the electrolyte to use a highly active formulation with no or significantly reduced flame-retardant additives. This directly improves the electrolyte ion mobility and enhances interface stability, thereby significantly improving the battery's rapid charge / discharge (rate) capability, low-temperature performance, and long-term cycle stability, achieving simultaneous optimization of safety and electrochemical performance.

[0016] In addition to the liquid cooling plates, air ducts, or phase change material layers added to ensure thermal management of battery packs or modules in related technologies, this invention fills the cavity and / or inner cavity with a thermally conductive liquid. This allows for direct, large-area heat exchange between the inner shell wall or cover plate and the battery cell, enabling rapid and uniform heat dissipation during charging and discharging. This effectively eliminates localized hot spots in areas such as the terminals and center, resulting in a highly uniform temperature distribution within the battery cell. This not only directly improves the battery's rate performance and power output but also significantly mitigates the accelerated degradation of cell materials (such as positive and negative electrodes and separators) during long-term use by suppressing localized overheating, thereby significantly extending the battery's cycle life. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 This is a first-view schematic diagram of a single battery cell in one embodiment of the present invention; Figure 2 This is a second-view schematic diagram of a single-cell battery in one embodiment of the present invention; Figure 3 This is a third-view schematic diagram of a single battery cell in one embodiment of the present invention; Figure 4 This is a schematic diagram of the battery casing structure in one embodiment of the present invention; Figure 5 The graph shows the rate charging performance test results for Comparative Example 1 and Example 1; the left side is a bar chart of the constant current ratio for both, and the right side is a temperature rise curve for both. Figure 6 The graph shows the rate discharge performance test results for Comparative Example 1 and Example 1; the left side is a bar chart of capacity retention for both, and the right side is a temperature rise curve for both. Figure 7 The graph shows the cell room temperature cycle retention test results for Comparative Example 1 and Example 1. Figure 8 The graph shows the rate charging performance test results for Comparative Example 2 and Example 2; the left side is a bar chart of the constant current ratio for both, and the right side is a temperature rise curve for both. Figure 9 The graph shows the rate discharge performance test results for Comparative Example 2 and Example 2; the left side is a bar chart of capacity retention rate for both, and the right side is a temperature rise curve for both. Figure 10 The graph shows the cell room temperature cycling retention test results for Comparative Example 2 and Example 2; Figure 11 The graph shows the rate charging performance test results for Comparative Example 3 and Example 3; the left side is a bar chart of the constant current ratio for both examples, and the right side is a temperature rise curve for both examples. Figure 12 The graph shows the rate discharge performance test results for Comparative Example 3 and Example 3; the left side is a bar chart of capacity retention rate for both, and the right side is a temperature rise curve for both. Figure 13 The graph shows the cell retention rate test results at room temperature for Comparative Example 3 and Example 3.

[0019] Explanation of icon numbers: 10 single cells; Battery casing 100; Inner shell 110; receiving cavity 111; opening 112; body part 113; mounting part 114; first connecting section 1141; second connecting section 1142; Casing 120; Port 121; Cavity 130; Cover plate 140; inner cavity 141; pole post 142; Battery cell 200; electrolyte 300.

[0020] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] In view of this, please refer to Figures 1 to 4 A first aspect of the present invention provides a battery housing 100, which includes an inner shell 110, an outer shell 120, and a cover plate 140. The inner shell 110 has a receiving cavity 111 with an opening 112 at one end for receiving a battery cell 200. The shape of the inner shell 110 matches the shape of the battery cell 200, including but not limited to a cuboid, cylindrical, or hexagonal prism shape. The inner shell 110 can be made of metal, including but not limited to aluminum, aluminum alloy, or stainless steel, to improve structural strength, sealing, and thermal conductivity. The outer shell 120 is fitted over the inner shell 110 and connected to the inner shell 110. A cavity 130 is formed between the outer shell 120 and the inner shell 110. The cavity 130 can be filled with a functional liquid. The functional liquid includes, but is not limited to, flame-retardant liquid, thermally conductive liquid, or liquid with both flame-retardant and thermally conductive functions. It is understood that the outer shell 120 may be made of the same or different materials as the inner shell 110, including but not limited to aluminum, aluminum alloy, stainless steel, engineering plastics or composite materials, in order to balance lightweight, insulation and molding process compatibility.

[0023] The inner shell 110 can be manufactured using a one-piece molding process or a separate welded structure to ensure structural integrity and sealing reliability. The outer shell 120 can be manufactured using a one-piece molding, stamping and stretching, or injection molding process. For ease of description, the following explanation assumes that both the inner shell 110 and the outer shell 120 are made of metal. The inner shell 110 and the outer shell 120 can be fixed using methods including but not limited to welding, riveting, or threaded connections, and a sealing structure can be provided at the connection point to ensure the airtightness and liquid tightness of the cavity 130. The sealing structure can employ methods including but not limited to O-rings, sealant, or laser sealing processes.

[0024] The cover plate 140 is sealed to the opening 112 of the inner shell 110 to close the receiving cavity 111. In some embodiments, the cover plate 140 has an inner cavity 141, which can be filled with a functional liquid to enhance the thermal management and flame-retardant protection of the upper surface of the battery cell 200. It is understood that in some embodiments, the battery casing 100 may simultaneously possess both a cavity 130 and an inner cavity 141, both containing functional liquids. The functional liquids filled in the two cavities may be the same or different, and each is independently controllable. It is understood that the inner cavity 141 and the cavity 130 can achieve liquid circulation through a communication structure to achieve thermal equilibrium or synergistic response. In some embodiments, the inner cavity 141 and the cavity 130 can be independently configured, i.e., the inner cavity 141 and the cavity 130 are not connected to each other, and the content ratio of the functional liquids contained in them may be the same or different.

[0025] In other embodiments, the inner cavity 141 and the cavity 130 can be selectively configured; that is, the battery housing 100 may include only the cavity 130 or only the inner cavity 141 to adapt to the safety, space utilization, and manufacturing cost requirements of different application scenarios. For example, the battery housing 100 may have the inner cavity 141 only inside the cover plate 140 or the cavity 130 only between the inner shell 110 and the outer shell 120 to simplify the structure and reduce production costs. For ease of description, the following description uses a square housing as an example. When only cavity 130 is provided, cavity 130 can be located in any one or more areas of the four sides and bottom of inner shell 110. In other words, cavity 130 is formed between at least one surface of inner shell 110 and outer shell 120, and cavity 130 can be continuously or intermittently distributed. The distribution area of ​​cavity 130 can also be adjusted accordingly to adapt to the actual installation orientation of battery in module or system. For example, when battery is installed vertically (terminal 142 facing upward), cavity 130 is preferentially arranged on the side wall and bottom of cell 200; when battery is installed horizontally (terminal 142 facing horizontally), cavity 130 is extended to the top surface and side wall for coordinated layout, thereby ensuring multi-directional blocking effect of heat and flame in the early stage of thermal runaway.

[0026] The cavity 130 and / or inner cavity 141 provide an independent, efficient safety barrier for the individual battery cell 10, physically isolated from the electrochemical system. This allows the individual battery cell 10 to immediately respond to the thermal runaway trigger signal when subjected to external impact or in the early stages of internal thermal runaway. Through the phase change heat absorption, convective heat transfer, or chemical inhibition of the functional liquid, it can suppress local temperature rise, dilute the concentration of flammable gases, and block the flame propagation path within milliseconds to seconds. This allows the individual battery cell 10 of this application to operate without relying on an external system. Its casing structure itself can achieve rapid thermal management (heat dissipation, temperature equalization) and / or flame retardant isolation through the internal functional liquid, thereby cutting off the thermal runaway chain reaction at the most basic unit level and greatly improving the intrinsic safety level of the battery.

[0027] Furthermore, compared to related technologies that add flame retardants to the electrolyte 300 to improve safety, this application separates the flame retardant function from the electrolyte 300 and externalizes it. This not only removes the coupling constraint between the electrolyte 300 formulation and safety functions, but also avoids the exacerbation of side reactions at the electrode material interface, the weakening of SEI / CEI film stability, and the sharp drop in ionic conductivity at low temperatures caused by flame retardant additives. Thus, the electrolyte 300 can use a highly active formulation with no or significantly reduced flame retardant additives, resulting in improved ion mobility and enhanced interface stability. This significantly improves the battery's rapid charge / discharge (rate) capability, low-temperature performance, and long-term cycle stability, achieving simultaneous optimization of safety and electrochemical performance.

[0028] In addition to the liquid cooling plates, air ducts, or phase change material layers added to ensure thermal management of battery packs or modules in related technologies, this invention fills the cavity 130 and / or inner cavity 141 with a thermally conductive liquid. This allows for direct, large-area heat exchange between the inner shell 110 wall or the inner wall of the cover plate 140 and the cell 200. This enables rapid and uniform heat dissipation from the cell 200 during charging and discharging, effectively eliminating localized hot spots in areas such as the electrode post 142 and the center, resulting in a highly uniform temperature distribution within the cell 200. This not only directly improves the battery's rate performance and power output but also significantly mitigates the accelerated degradation of cell 200 materials (such as positive and negative electrodes and separators) during long-term use by suppressing localized overheating, thereby significantly extending the battery's cycle life.

[0029] Flame retardant liquids can include, but are not limited to, organophosphorus flame retardants (triphenyl phosphate, tricresyl phosphate, dimethyl methylphosphonate), halogenated flame retardants (bromophosphate, chlorinated paraffin), and inorganic flame retardant liquid dispersion systems (nano-aluminum hydroxide, nano-magnesium hydroxide, modified silica dispersions). Thermally conductive liquids can include, but are not limited to, oil-based thermally conductive liquids (hydrogenated terphenyl, methyl silicone oil, perfluoropolyether oil), organically synthesized thermally conductive liquids (azeotropic mixtures of biphenyl and diphenyl ether, such as Dowtherm A, Therminol VP-1), and water-based thermally conductive liquids (vinyl glycol aqueous solution, alumina water-based nanofluids).

[0030] The filling volume of the functional liquid in the cavity 130 and / or inner cavity 141 is not less than 5% of the total volume of the corresponding cavity 130 or inner cavity 141. For example, the filling volume of the functional liquid can be 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or 100%. It is understood that the filling volume of the functional liquid can be adjusted according to actual thermal management, flame retardant requirements, or the type of functional liquid. For example, when the functional liquid is a volatile liquid and is mainly used for flame retardancy, the filling volume can be appropriately reduced to reserve expansion space; while when the functional liquid is a high-boiling-point, low-volatility heat-conducting liquid and needs to undertake the main heat dissipation function, the filling volume is preferably not less than 70%, more preferably 80% to 100%, to ensure continuous and efficient heat conduction performance.

[0031] The dimension of the cavity 130 along the direction from the inner shell 110 to the outer shell 120 is between 0.1 mm and 15 mm, and exemplary dimensions may be 0.1 mm, 0.5 mm, 1 mm, 2 mm, 5 mm, 10 mm, or 15 mm. This dimension can be optimized according to the capacity, power requirements, and thermal management objectives of the battery cell, ensuring structural strength while providing sufficient space for the functional liquid to flow and function, thereby balancing heat dissipation efficiency and lightweight requirements. The cross-sectional shape of the cavity 130 may be rectangular, circular, elliptical, or polygonal. In some embodiments, the inner wall of the cavity 130 is provided with a microstructure texture or a hydrophilic coating to enhance the spreadability and interfacial wettability of the functional liquid, improve the uniformity of heat conduction, and enhance the flame retardant coverage efficiency.

[0032] It is understood that the dimension of the inner cavity 141 along the direction from the cover plate 140 to the interior of the receiving cavity 111 is between 0.1 mm and 15 mm, and for example, it can be 0.1 mm, 0.5 mm, 1 mm, 2 mm, 5 mm, 10 mm, or 15 mm. It should be noted that this dimension of the inner cavity 141 is matched with the thickness of the cover plate 140, the sealing structure, and the static residence stability of the functional fluid, so as to avoid local enrichment or coverage blind areas of the functional fluid due to gravity settling or vibration, thereby ensuring rapid response and uniform coverage of the root of the electrode post 142, the weld area, and the key heat source points on the top of the cell 200 in the early stage of thermal runaway triggering.

[0033] In some embodiments, a cavity 130 is provided between the outer shell 120 and the inner shell 110, and the cover plate 140 is provided with an inner cavity 141, which communicates with the cavity 130 to form a continuous functional liquid flow path. Specifically, a connecting member is provided on the side of the cover plate 140 facing the opening 112, and the connecting member has a channel communicating with the inner cavity 141. When the cover plate 140 is assembled to the battery housing 100, the connecting member is inserted into the cavity 130, thereby enabling fluid communication between the inner cavity 141 and the cavity 130 through the channel.

[0034] To facilitate the injection of functional fluid, in some embodiments, the cover plate 140 is provided with an injection hole communicating with the inner cavity 141. This injection hole is used to inject functional fluid into the inner cavity 141, and the functional fluid entering the inner cavity 141 can flow into the cavity 130 through the channel of the connecting member. In addition, the cover plate 140 is provided with a sealing and plugging structure, which is used to seal the injection hole after injection to prevent functional fluid leakage and the intrusion of external contaminants. It is understood that this sealing and plugging structure can be achieved using methods including, but not limited to, laser welding, welded metal balls, sealing screws, etc.

[0035] In other embodiments, a cavity 130 is provided between the outer shell 120 and the inner shell 110, and an inner cavity 141 is provided within the cover plate 140. The inner cavity 141 and the cavity 131 are independently configured and do not communicate with each other. Therefore, to facilitate the injection of functional liquid, both the cover plate 140 and the outer shell 120 are provided with injection holes. The injection hole on the cover plate 140 communicates with the inner cavity 141 for injecting functional liquid into the inner cavity 141. The injection hole on the outer shell 120 communicates with the cavity 130 for injecting functional liquid into the cavity 130. Furthermore, the battery housing 100 has a sealing structure corresponding to the number of injection holes, which is used to seal the injection holes after the functional liquid has been injected.

[0036] When the cover plate 140 has an inner cavity 141, it also has a terminal post 142 for electrical connection with the battery cell 200. The terminal post 142 penetrates the cover plate 140 and extends into the receiving cavity 111 to connect to the electrode tab of the battery cell 200. Insulating seals are provided between the terminal post 142 and the cover plate 140, and between the terminal post 142 and the functional fluid. The insulating seals can be, but are not limited to, glass-to-metal seals, ceramic-to-metal seals, or high-performance engineering plastic injection molded seals. The insulating seals ensure electrical insulation, prevent leakage of the functional fluid, and guarantee the independence and reliability of the electrical connection channel.

[0037] To prevent deformation of the cavity 130 and ensure the stability and durability of the sandwich structure, in some embodiments, a reinforcing structure is provided within the cavity 130. This reinforcing structure can be connected to the inner wall surface of the inner shell 110 and / or the outer shell 120, and can be a dot matrix, ribs, corrugated support plates, or an irregular support column network structure. The reinforcing structure not only improves the mechanical strength of the battery casing 100, but also maintains the geometric integrity of the cavity 130 during the thermal runaway of the individual battery 10, thereby ensuring the directional flow and uniform spread of the functional liquid under high pressure conditions and avoiding blockage or coverage failure of the cavity 130 due to structural collapse. Similarly, a similar reinforcing structure can also be provided within the inner cavity 141 to enhance its resistance to deformation under injection pressure and thermal runaway impact, ensuring the stability of the cross-section of the inner cavity 141 and the unobstructed flow channels.

[0038] Understandably, the reinforced structure can also enhance the dynamic response of the functional liquid in the cavity 130 and / or inner cavity 141. The reinforced structure acts similarly to a flow guide, capillary channel array, or microporous baffle, guiding the liquid's directional flow and suppressing gas-liquid interface disturbances, thus enhancing the capillary drive effect and accelerating the response speed and distribution uniformity of the functional liquid under thermal stimulation. Furthermore, the cross-section of the reinforced structure can be triangular, trapezoidal, or semi-circular, and its dimensions along the direction from the inner shell 110 to the outer shell 120 are adapted to the dimensions of the cavity 130.

[0039] Please see Figure 4 In some embodiments, the outer shell 120 has a port 121 communicating with the opening 112, through which the inner shell 110 is inserted into the outer shell 120. The inner shell 110 includes a body portion 113 and a mounting portion 114. The body portion 113 defines a receiving cavity 111. The mounting portion 114 is connected to the body portion 113 and disposed around the edge of the opening 112. To ensure an effective seal of the cavity 130, in some embodiments, the mounting portion 114 includes a first connecting segment 1141, wherein the first connecting segment 1141 is bent relative to the body portion 113 in a direction away from the receiving cavity 111 and is laser-welded to the edge of the port 121 of the outer shell 120.

[0040] To ensure the connection strength between the inner shell 110 and the outer shell 120, in some embodiments, the mounting portion 114 includes a first connecting segment 1141 and a second connecting segment 1142. The first connecting segment 1141 is bent away from the receiving cavity 111 relative to the body portion 113 and is laser-welded to the edge of the port 121 of the outer shell 120. One end of the second connecting segment 1142 is connected to the first connecting segment 1141 and is further bent relative to the first connecting segment 1141 along the wall of the outer shell 120. The second connecting segment 1142 is fixed to the outer surface of the outer shell 120 away from the inner shell 110 by welding. The arrangement of the first connecting segment 1141 can effectively seal the cavity 130 and also increase the effective contact area between the battery housing 100 and the cover plate 140, thereby forming a more stable mechanical connection at the connection between the cover plate 140 and the battery housing 100. The second connecting section 1142 increases the welding area, further enhances the connection strength between the inner shell 110 and the outer shell 120, and improves the fatigue resistance of the overall structure under thermal cycling and vibration conditions.

[0041] Please see Figures 1 to 3A second aspect of the present invention also provides a single-cell battery 10, comprising a cell 200, an electrolyte 300, and a battery casing 100 as described in any of the preceding embodiments. The cell 200 and the electrolyte 300 are both housed within a receiving cavity 111, and the cell 200 may be a stacked or wound structure. It is understood that the battery casing 100 separates the flame-retardant and / or thermally conductive functions from the electrolyte 300, thereby allowing the electrolyte 300 to return to its purely electrochemical medium function, no longer undertaking the combined functions of thermal management or safety protection. This not only reduces the redundancy and compatibility risks in the electrolyte 300 formulation design but also provides the battery system with multiple optimization possibilities in terms of energy density, cycle life, and low-temperature performance.

[0042] To verify the beneficial effects achieved by the battery casing 100 and the single battery cell 10 provided by the present invention, specific embodiments and comparative examples are described below.

[0043] Comparative Example 1: A lithium iron phosphate battery with dimensions of 27*148*154mm and a capacity of 50Ah was used. The battery had a conventional aluminum casing and no inner shell 110 or cavity 130. The electrolyte 300 contained flame retardant additives and thermally conductive fillers.

[0044] Example 1: A lithium iron phosphate battery with dimensions of 27*148*154mm and a capacity of 50Ah is used, equipped with a composite shell with an inner shell 110 and a cavity 130 as described in this invention. The electrolyte 300 does not contain flame retardants or thermally conductive fillers. The cavity 130 has a dimension of 0.5mm in the direction from the inner shell 110 to the outer shell 120, and the cavity 130 is filled with 50% thermally conductive liquid and 50% flame retardant liquid, which occupy 50% of the volume of the cavity 130.

[0045] The batteries provided in Comparative Example 1 and Example 1 were subjected to cell 200 capacity testing, drop pass rate testing, crush pass rate testing, and needle penetration pass rate testing, respectively. The test results are shown in Table 1 below: Table 1 - Safety Performance Test Results

[0046] As shown in Table 1, Example 1 is superior to Comparative Example 1 in all aspects of safety performance indicators. It should be noted that in Example 1, the areal density of the battery cell can be increased by 8.1% compared to Comparative Example 1, resulting in nearly identical capacities for single-cell batteries of the same size. It is understood that in conventional technologies, electrolytes possess both flame-retardant and thermally conductive properties, thus exhibiting high viscosity. To ensure effective contact between the battery cell and the electrolyte, it is difficult to further increase the areal density of the battery cell while considering other performance aspects. However, by providing the cavity 130 and / or the inner cavity 141, the flame-retardant and thermally conductive functions of the electrolyte are stripped away, thereby breaking the limitations of traditional electrolytes on increasing battery areal density.

[0047] The batteries provided in Example 1 and Example 1 were subjected to rate charging performance tests, and the test results are as follows: Figure 5 As shown: The constant current ratio of the single cell 10 in Example 1 during 1C charging was improved by 1.4% compared to Comparative Example 1, and the temperature rise was reduced by 4.8℃. Under 5C fast charging conditions, the constant current ratio of Example 1 was improved by 18.6% compared to Comparative Example 1, and the temperature rise was reduced by 7.2℃.

[0048] The batteries provided in Example 1 and Example 1 were subjected to rate discharge performance tests. The test results are available in [reference]. Figure 6 Among them, at 1C discharge, the temperature rise of Example 1 was reduced by 5.3°C compared with Comparative Example 1, while at 5C discharge, the temperature rise was reduced by 6.7°C and the capacity retention was improved by 7.6%.

[0049] The batteries provided in Comparative Example 1 and Example 1 were subjected to cycle performance tests. The test results are available in [reference]. Figure 7 Among them, under 1C room temperature cycling for 800 cycles, the battery capacity retention rate of Example 1 was improved by 3.11% compared with that of Comparative Example 1.

[0050] Comparative Example 2: A lithium iron phosphate battery with dimensions of 50*160*119mm and a capacity of 100Ah was used. It had a conventional aluminum shell design and the electrolyte contained flame retardant and thermally conductive filler.

[0051] Example 2: A lithium iron phosphate battery with dimensions of 50*160*119mm and a capacity of 100Ah is used, equipped with a composite shell with an inner shell 110 and a cavity 130 as described in this invention. The electrolyte 300 does not contain flame retardants or thermally conductive fillers. The cavity 130 has a dimension of 0.5mm in the direction from the inner shell 110 to the outer shell 120. The cavity 130 is filled with 50% thermally conductive liquid and 50% flame retardant liquid, which occupy 50% of the volume of the cavity 130.

[0052] The batteries provided in Comparative Example 2 and Example 2 were subjected to cell 200 capacity testing, drop pass rate testing, crush pass rate testing, and needle penetration pass rate testing, respectively. The test results are shown in Table 2 below: Table 2 - Safety Performance Test Results

[0053] As can be seen from Table 2, Example 2 is superior to Comparative Example 2 in all aspects of safety performance indicators. It should be noted that in Example 2, the areal density of the battery cell can be increased by 5.3% compared with that of Comparative Example 2, so that the single cells of the same size provided by both have nearly the same capacity.

[0054] The batteries provided in Comparative Example 2 and Example 2 were subjected to rate charging performance tests, and the test results are as follows: Figure 8 As shown: The constant current ratio of the single cell 10 in Example 2 during 1C charging was improved by 2.8% compared to Comparative Example 2, and the temperature rise was reduced by 8.8°C. Under 6C fast charging conditions, the constant current ratio of Example 2 was improved by 78.1% compared to Comparative Example 2, and the temperature rise was reduced by 5.5°C.

[0055] The batteries provided in Example 2 and Example 2 were subjected to rate discharge performance tests. The test results are available in [reference]. Figure 9 Among them, at 1C discharge, the temperature rise of Example 2 was reduced by 10.1°C compared to Comparative Example 2, while at 6C discharge, the temperature rise was reduced by 5.1°C and the capacity retention was improved by 15.1%.

[0056] The batteries provided in Comparative Example 2 and Example 2 were subjected to cycle performance tests. The test results are available in [reference]. Figure 10 Among them, under 1C room temperature cycling for 300 cycles, the battery capacity retention rate of Example 2 was improved by 4.12% compared with that of Comparative Example 2.

[0057] Comparative Example 3: A ternary lithium battery with dimensions of 27*148*101mm and a capacity of 28Ah was used. It had a conventional aluminum shell design and the electrolyte 300 contained flame retardants and thermally conductive fillers.

[0058] Example 3: A ternary lithium battery with dimensions of 27*148*101mm and a capacity of 28Ah is used, equipped with a composite shell with an inner shell 110 and a cavity 130 as described in this invention. The electrolyte 300 does not contain flame retardants or thermally conductive fillers. The cavity 130 has a dimension of 0.5mm in the direction from the inner shell 110 to the outer shell 120, and is filled with 50% thermally conductive liquid and 50% flame retardant liquid, which occupy 50% of the volume of the cavity 130.

[0059] The batteries provided in Comparative Example 3 and Example 3 were subjected to cell 200 capacity testing, drop pass rate testing, crush pass rate testing, and needle penetration pass rate testing, respectively. The test results are shown in Table 3 below: Table 3 - Safety Performance Test Results

[0060] As can be seen from Table 3, Example 3 is superior to Comparative Example 3 in all aspects of safety performance indicators. It should be noted that in Example 3, the areal density of the battery cell can be increased by 7.6% compared with that of Comparative Example 3, so that the single cells of the same size provided by both can have nearly the same capacity.

[0061] The batteries provided in Example 3 and Example 3 will be tested for their rate charging performance. The test results are as follows: Figure 11 As shown: The constant current ratio of the single cell 10 in Example 3 during 1C charging was improved by 0.3% compared to Comparative Example 3, and the temperature rise was reduced by 2.2℃. Under 10C fast charging conditions, the constant current ratio of Example 3 was improved by 59.2% compared to Comparative Example 3, and the temperature rise was reduced by 11.7℃.

[0062] The batteries provided in Example 3 and Example 3 were subjected to rate discharge performance tests. The test results are available in [reference]. Figure 12 Among them, at 1C discharge, the temperature rise of Example 3 was reduced by 3.6°C compared with Comparative Example 3, while at 10C discharge, the temperature rise was reduced by 15.3°C and the capacity retention was improved by 1.49%.

[0063] The batteries provided in Comparative Example 3 and Example 3 were subjected to cycle performance tests. The test results are available in [reference]. Figure 13 Among them, under 1C room temperature cycling for 1000 cycles, the battery capacity retention rate of Example 3 was improved by 2.8% compared with that of Comparative Example 3.

[0064] Furthermore, while maintaining the same structural parameters, functional liquid types, and filling rates for the single cell 10, the dimensions of the cavity 130 were changed, and safety performance tests were conducted on Examples 4 to 26. The results are summarized in Table 4 below; where the dimensions of the cavity 130 refer to the dimensions of the cavity 130 along the direction from the inner shell 110 to the outer shell 120, in millimeters, and the volume ratio of the flame-retardant liquid and the thermally conductive liquid filling the cavity 130 is always 50% each.

[0065] Table 4 - Safety Performance Test Results

[0066] As can be seen, compared with the traditional solid shell (the cavity 130 has a size of 0.0 mm), the battery shell 100 provided by the present invention has a single cell 10 with a cavity 130, which significantly improves the pass rate of all key safety tests (drop, crush, and needle penetration) and also greatly extends the cycle life.

[0067] Furthermore, with all other structural parameters of the single cell 10 completely identical and the cavity 130 dimension unchanged (taken as 0.5 mm), the ratio of the functional liquid (the ratio of thermally conductive liquid to flame-retardant liquid) was changed, and safety performance tests were conducted on Examples 27 to 48. The results are summarized in Table 5 below: Table 5 - Safety Performance Test Results

[0068] Therefore, it can be seen that the use of pure flame-retardant liquids, pure thermally conductive liquids, and even compound liquids of any proportion in the single cell 10 of the present invention can significantly and comprehensively improve the overall performance (safety pass rate, cycle life, temperature rise control) of the single cell 10.

[0069] It should be noted that if directional indications (such as up, down, left, right, front, back, etc.) are involved in the embodiments of the present invention, these directional indications are only used to explain the relative positional relationships and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly. When a direction reference is introduced in a specific embodiment, unless the direction is specifically limited to unidirectional, the direction can be unidirectional or bidirectional (two parallel and opposite directions). Whether it is unidirectional or bidirectional depends on what those skilled in the art can achieve. When the direction reference is bidirectional, it should be considered that two parallel and different embodiments have been introduced simultaneously.

[0070] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or," "and / or," or "and / or" throughout the text implies three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0071] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural transformations made using the contents of the specification and drawings of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of patent protection of the present invention.

Claims

1. A battery casing suitable for accommodating battery cells, characterized in that, The battery casing includes: The inner shell has a receiving cavity with an opening at one end for accommodating the battery cell; An outer shell is fitted over the inner shell and connected to the inner shell, and there is a cavity between the outer shell and the inner shell, which is filled with a functional liquid; A cover plate, which is sealed to the opening end of the inner shell, is used to close the receiving cavity; Wherein, a cavity exists between the outer shell and the inner shell, and at least one wall surface of the inner shell facing the outer shell contacts the cavity, the cavity being filled with a functional liquid; and / or The cover plate has an inner cavity filled with a functional liquid.

2. The battery casing as described in claim 1, characterized in that, The functional liquids include flame-retardant liquids and / or thermally conductive liquids.

3. The battery casing as described in claim 1, characterized in that, The filling volume of the functional liquid in the cavity and / or the inner cavity is not less than 5% of the total volume of the cavity and / or the inner cavity.

4. The battery casing as described in claim 1, characterized in that, The cavity has a dimension of 0.1 mm to 15 mm in the direction from the inner shell to the outer shell; And / or, The inner cavity has a dimension of 0.1 mm to 15 mm along the direction from the cover plate toward the interior of the receiving cavity.

5. The battery casing as described in claim 1, characterized in that, There is a cavity between the outer shell and the inner shell, and the cover plate has an inner cavity. The cavity and the inner cavity are independently arranged.

6. The battery casing as described in claim 5, characterized in that, The battery casing is also provided with a liquid injection hole, which is located on the cover plate and communicates with the inner cavity. The liquid injection hole is also located on the outer shell and communicates with the cavity. The liquid injection hole is used to inject the functional liquid into the inner cavity and the cavity. The battery housing also includes a sealing structure for sealing the injection hole after the functional liquid is injected.

7. The battery casing as described in claim 1, characterized in that, The cover plate has an inner cavity and a terminal post for electrical connection with the battery cell. The terminal post passes through the cover plate and extends into the receiving cavity. An insulating seal is provided between the terminal post, the cover plate, and the functional liquid filled in the inner cavity. The insulating seal is used to block the electrical connection between the terminal post, the cover plate, and the functional liquid.

8. The battery casing as described in claim 1, characterized in that, The cavity is provided with a reinforcing structure, which is connected to the inner shell and / or the outer shell to enhance the structural rigidity between the inner shell and the outer shell.

9. The battery casing as described in claim 1, characterized in that, The outer shell has a port communicating with the opening, and the inner shell includes a body portion and a mounting portion. The body portion defines the receiving cavity, and the mounting portion is connected to the body portion and disposed around the edge of the opening. The mounting portion includes a first connecting section, which is bent relative to the body portion away from the receiving cavity and connected to the edge of the port; or The mounting portion includes a first connecting segment and a second connecting segment. The first connecting segment is bent away from the body portion in a direction away from the receiving cavity and connected to the edge of the port. One end of the second connecting segment is connected to the first connecting segment and bent relative to the first connecting segment. The second connecting segment is welded to the surface of the outer shell away from the inner shell.

10. A single-cell battery, characterized in that, include: Battery cell; Electrolyte; as well as The battery casing as described in any one of claims 1-9, wherein the battery cell and the electrolyte are housed within the housing cavity.

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