Secondary battery and electric device

Abstract

The application discloses a secondary battery and an electric device. The secondary battery comprises a first shell, a second shell and an electric core. The first shell and the second shell are insulatedly connected and form an accommodating cavity. The electric core is arranged in the accommodating cavity and is composed of a plurality of positive electrode sheets, a plurality of separators and a plurality of negative electrode sheets which are alternately stacked. The separators isolate adjacent positive electrode sheets and negative electrode sheets. Each positive electrode sheet contains a first current collector. The plurality of first current collectors are electrically connected with each other and are welded to the first shell. Each negative electrode sheet contains a second current collector. The plurality of second current collectors are electrically connected with each other and are welded to the second shell. The application improves the connection strength of the electrode sheet current collector and the shell, avoids relative displacement and loose connection of the battery under long-term charge-discharge cycle, vibration or high-low temperature environment, directly welds the current collector bus to the shell after the current collector bus, eliminates the connection gap, reduces the generation of the oxide layer, effectively reduces the contact resistance, reduces the battery energy consumption and improves the discharge efficiency, simultaneously avoids the aggravation of local heating, and reduces the risk of thermal runaway.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, and in particular to a secondary battery and electrical equipment. Background Technology

[0002] With the rapid development of new energy vehicles, portable electronic devices, and large-scale energy storage power stations, increasingly higher demands are being placed on the energy density, power performance, safety, and manufacturing cost of lithium-ion batteries. As the core component of a battery, the structural design of the cell directly affects its overall performance.

[0003] In traditional cylindrical or square steel / aluminum-cased lithium batteries, the positive and negative electrodes inside the cell are connected to the battery terminals via metal tabs. The terminals then pass through the battery casing and are insulated and sealed with a sealing ring. However, this structure has several inherent drawbacks: 1. Energy density limitations: The tabs, terminals, and necessary accessories for fixing and insulation (such as sealing rings) occupy internal space and weight, severely restricting further improvements in the energy density of individual battery cells. 2. High internal resistance and heat dissipation issues: The current path is long and there are many connection points. Current must be collected from the current collector through the tabs to the terminals. Each welded interface and the long tabs introduce additional contact resistance and ohmic resistance, leading to an increase in the overall internal resistance of the battery. Increased internal resistance not only causes energy loss during charging and discharging (reducing efficiency) but also generates more Joule heat, exacerbating battery temperature rise, adversely affecting cycle life and fast charging performance, and even creating a potential safety hazard of thermal runaway.

[0004] Therefore, there is an urgent need for an innovative battery structure design to simplify internal connections, reduce internal resistance, and ultimately achieve a comprehensive improvement in battery energy density, power performance, and reliability. Utility Model Content

[0005] The main purpose of this application is to propose a secondary battery and electrical device, which aims to solve the technical problems of limited energy density, high internal resistance and poor heat dissipation of existing secondary batteries.

[0006] To achieve the above objectives, this application proposes a secondary battery, comprising:

[0007] First shell;

[0008] The second housing, the first housing and the second housing together form a receiving cavity, and the first housing and the second housing are insulated from each other;

[0009] A battery cell is disposed in the receiving cavity. The battery cell includes a plurality of positive electrode plates, a plurality of separators and a plurality of negative electrode plates arranged in alternating layers. The separators are located between adjacent positive electrode plates and negative electrode plates.

[0010] Each of the positive electrode plates includes a first current collector, the first current collectors of the plurality of positive electrode plates are electrically connected to each other and are welded to the first housing; each of the negative electrode plates includes a second current collector, the second current collectors of the plurality of negative electrode plates are electrically connected to each other and are welded to the second housing.

[0011] In some embodiments, the first current collector includes a first main body and a first connecting portion, wherein the first connecting portion is connected to one side of the first main body;

[0012] The first main body portions of the plurality of positive electrode sheets are arranged sequentially along the thickness direction of the battery cell, and the first connecting portions of the plurality of positive electrode sheets are electrically connected to each other and welded to the first housing.

[0013] In some embodiments, the second current collector includes a second main body and a second connecting part, wherein the second connecting part is connected to one side of the second main body;

[0014] The second main body portions of the plurality of negative electrode sheets are arranged sequentially along the thickness direction of the battery cell, and the second connecting portions of the plurality of negative electrode sheets are electrically connected to each other and welded to the second housing.

[0015] In some embodiments, the first connecting portions of the plurality of positive electrode plates are electrically connected to each other to form a first bus terminal, and the first bus terminal is welded to the first housing; and / or,

[0016] The second connecting portions of the plurality of negative electrode plates are electrically connected to each other to form a second bus terminal, and the second bus terminal is welded to the second housing.

[0017] In some embodiments, the outermost positive electrode plate of the battery cell is a first positive electrode plate, which is disposed facing the first housing, and the first current collector of the first positive electrode plate is welded to the inner wall of the first housing;

[0018] The outermost negative electrode plate of the battery cell is the first negative electrode plate, which is disposed facing the second housing, and the second current collector of the first negative electrode plate is welded to the inner wall of the second housing.

[0019] In some embodiments, the surface of the first positive electrode facing the first housing is a first empty foil area, and the first empty foil area is welded to the first housing.

[0020] The surface of the first negative electrode facing the second housing is the second empty foil area, which is welded to the second housing.

[0021] In some embodiments, the first housing is provided with a first slot corresponding to the first empty foil area, the opening of the first slot is away from the first empty foil area, and the first empty foil area is welded to the bottom wall of the first slot.

[0022] The second housing has a second slot corresponding to the second empty foil area. The opening of the second slot is away from the second empty foil area, and the second empty foil area is welded to the bottom wall of the second slot.

[0023] In some embodiments, the secondary battery further includes a first cover plate, which covers the first slot and is sealed to the outer wall of the first housing.

[0024] The secondary battery also includes a second cover plate, which covers the second slot and is sealed to the outer wall of the second housing.

[0025] In some embodiments, a first step is provided at the first slot, the first cover plate abuts against the first step, and the surface of the first cover plate is not higher than the surface of the first housing.

[0026] The second groove is provided with a second step, the second cover plate abuts against the second step, and the surface of the second cover plate is not higher than the surface of the second housing.

[0027] The secondary battery provided in this application connects multiple positive electrode plates to a first current collector and then welds them directly to a first housing, and connects multiple negative electrode plates to a second current collector and then welds them directly to a second housing, so that the first housing and the second housing become the positive and negative output terminals of the battery, respectively. This design eliminates redundant structures such as metal tabs, terminals, and sealing rings found in traditional batteries. On one hand, by eliminating the space occupied and weight increased by these structures, the amount of active material loaded in the cavity is significantly increased, effectively breaking through the bottleneck of limited energy density in traditional batteries. This better meets the long-range requirements of new energy vehicles, portable electronic devices, and other scenarios. On the other hand, the current does not need to be collected from the tabs to the terminals but is directly conducted from the current collector to the casing, greatly shortening the current conduction path. At the same time, it reduces resistance introduction points such as welding interfaces, lowering the overall internal resistance of the battery. This not only reduces energy loss during charging and discharging and improves energy conversion efficiency but also reduces the amount of Joule heat generated, effectively alleviating the battery temperature rise problem. This improves the battery's cycle life and fast-charging performance, while avoiding the safety hazards of thermal runaway caused by excessive temperature rise. It enhances the overall performance of the battery while ensuring safety in use. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a secondary battery according to an embodiment of the present invention.

[0029] Explanation of icon numbers:

[0030] 100 Secondary batteries 10 First shell 20 Second shell 101 Receiving cavity 31 Positive electrode film 32 diaphragm 33 negative electrode sheet 311 First fluid collector 331 Second fluid 3111 First Main Body 3112 First connecting part 3311 Second Main Body 3312 Second connecting part 310 First junction 330 Second junction Detailed Implementation

[0031] The solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments in this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0032] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0033] It should also be noted that when a component is described as "fixed to" or "set on" another component, it can be directly on the other component or there may be an intervening component present. When a component is described as "connected to" another component, it can be directly connected to the other component or there may be an intervening component present.

[0034] Furthermore, the use of terms such as "first" and "second" in this application is 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 as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0035] Please refer to Figure 1 An embodiment of this application provides a secondary battery 100, including a first housing 10, a second housing 20, and a battery cell; the first housing 10 and the second housing 20 enclose a receiving cavity 101, and the first housing 10 and the second housing 20 are insulated from each other; the battery cell is disposed in the receiving cavity 101, and the battery cell includes a plurality of positive electrode plates 31, a plurality of separators 32, and a plurality of negative electrode plates 33 alternately stacked, with the separators 32 located between adjacent positive electrode plates 31 and negative electrode plates 33;

[0036] Each positive electrode 31 includes a first current collector 311, the first current collectors 311 of the multiple positive electrode 31s are electrically connected to each other and are welded to the first housing 10; each negative electrode 33 includes a second current collector 331, the second current collectors 331 of the multiple negative electrode 33s are electrically connected to each other and are welded to the second housing 20.

[0037] In this embodiment, the first housing 10 and the second housing 20 enclose a cavity 101, creating a stable internal environment for the battery cell and ensuring the normal progress of the internal chemical reactions in the secondary battery 100. This provides physical protection for the battery cell and other internal components, preventing the intrusion of foreign objects and simultaneously withstanding certain mechanical stresses to maintain the integrity of the battery structure. Furthermore, the first housing 10 and the second housing 20 are insulated from each other, effectively preventing short circuits between the positive and negative electrodes and ensuring the safety and reliability of the battery operation.

[0038] Furthermore, the first housing 10, serving as the positive electrode casing of the secondary battery 100, is welded to the first current collector 311 of the plurality of positive electrode plates 31, undertaking the crucial function of collecting and conducting positive electrode current. The welding connection ensures a good electrical connection between the positive electrode plates 31 and the first housing 10, effectively reducing contact resistance and improving the battery's charging and discharging efficiency.

[0039] The second housing 20, serving as the negative electrode casing of the battery, is welded to the second current collector 331 of multiple negative electrode plates 33. It is responsible for collecting and conducting the negative electrode current, ensuring that electrons can flow smoothly from the negative electrode during battery discharge, thus achieving electrical energy output. The welding connection ensures a good electrical connection between the negative electrode plates 33 and the second housing 20, effectively reducing contact resistance and improving the battery's charging and discharging efficiency.

[0040] The secondary battery 100 provided in this application embodiment is directly welded to the first housing 10 after the first current collectors 311 of multiple positive electrode plates 31 are electrically connected to each other, and directly welded to the second housing 20 after the second current collectors 331 of multiple negative electrode plates 33 are electrically connected to each other, so that the first housing 10 and the second housing 20 become the positive and negative output terminals of the battery, respectively. This design eliminates redundant structures such as metal tabs, terminals, and sealing rings found in traditional batteries. On one hand, by eliminating the space occupied and weight increased by these structures, the amount of active material loaded in the housing 101 is significantly increased, effectively breaking through the bottleneck of limited energy density in traditional batteries. This better meets the long-range requirements of new energy vehicles, portable electronic devices, and other scenarios. On the other hand, the current does not need to be collected from the tabs to the terminals but is directly conducted from the current collector to the casing, greatly shortening the current conduction path. At the same time, it reduces resistance introduction points such as welding interfaces, lowering the overall internal resistance of the battery. This not only reduces energy loss during charging and discharging and improves energy conversion efficiency but also reduces the amount of Joule heat generated, effectively alleviating the battery temperature rise problem. This improves the battery's cycle life and fast-charging performance, while avoiding the safety hazard of thermal runaway caused by excessive temperature rise. It enhances the overall performance of the battery while ensuring safety in use.

[0041] Furthermore, compared to existing riveting, crimping, and other connection methods, the welding connection adopted in this application embodiment can significantly improve the connection strength between the electrode current collector and the shell, effectively avoiding the problems of relative displacement and loosening of the electrode and the shell during long-term charge-discharge cycles, vibration, or high and low temperature environments. At the same time, the direct welding of multiple current collectors to the shell after converging can eliminate connection gaps, reduce the risk of oxide layer formation, effectively reduce contact resistance, and thus reduce battery energy consumption and improve discharge efficiency. In addition, the low impedance characteristic can also avoid the aggravation of local heat generation, reduce the risk of thermal runaway, and ensure the reliability and safety of the battery for long-term use.

[0042] In some embodiments, the welding connection between the first current collector 311 of the positive electrode 31 and the first housing 10, and the second current collector 331 of the negative electrode 33 and the second housing 20, can preferably be achieved using ultrasonic welding. Ultrasonic welding, utilizing the localized heat generated by high-frequency mechanical vibration, enables a solid-state connection between the current collector and the housing at low temperatures and without external solder. This avoids damage to the current collector and housing materials caused by high-temperature welding, ensuring the structural integrity and conductivity of the conductive carrier. Furthermore, the resulting weld joint has high strength and good sealing properties, further improving the stability of the connection between the electrode and the housing, effectively resisting stress impacts during battery cycling, reducing the risk of oxide layer formation at the connection point, and maintaining low contact resistance characteristics.

[0043] In some embodiments, the first current collector 311 includes a first main body portion 3111 and a first connecting portion 3112, wherein the first connecting portion 3112 is connected to one side of the first main body portion 3111;

[0044] The first main body portion 3111 of the plurality of positive electrode plates 31 is arranged sequentially along the thickness direction of the battery cell, and the first connecting portion 3112 of the plurality of positive electrode plates 31 is electrically connected to each other and welded to the first housing 10.

[0045] In this embodiment, the first main body 3111 serves as a supporting structure for the positive electrode 31. Its surface is coated with a positive electrode active material (such as ternary materials, lithium iron phosphate, etc.) to provide a storage and reaction site for lithium ions, which is the basis for realizing the electrochemical performance of the battery. During charging and discharging, on the one hand, lithium ions are allowed to migrate between the active material and the electrolyte, and on the other hand, the current generated by the active material is conducted to the first connection part 3112 to ensure effective output of electrical energy.

[0046] The first connecting part 3112 is connected to one side of the first main body part 3111, which can conduct the current of a single positive electrode 31, and through the mutual electrical connection of multiple first connecting parts 3112, concentrate the dispersed current of the multi-layer positive electrode 31 into a unified current, avoiding the loss caused by the dispersion of current conduction between the multi-layer electrodes.

[0047] Preferably, the first connecting part 3112 can be uniformly connected to one side of the first main body part 3111, which can realize the centralized arrangement of multiple first connecting parts 3112, avoid the displacement of the internal structure of the battery cell caused by the dispersion of the connecting parts, and ensure the neatness and stability of the battery cell stack.

[0048] During assembly, the first connecting parts 3112 of multiple positive electrode plates 31 can be connected to each other to form a busbar group, and then the whole assembly can be welded to the first housing 10, which improves the battery assembly efficiency and reduces the risk of welding error caused by connecting them one by one.

[0049] The current-combining design of the first connecting portion 3112 in this embodiment avoids the path differences when the current of each positive electrode 31 is conducted to the casing individually, reducing mutual interference and loss during the current conduction process, and making the overall current conduction on the positive electrode side more uniform and efficient. Moreover, the segmented design of the first main body portion 3111 and the first connecting portion 3112 allows for flexible adjustment of their size and connection method according to the cell stack thickness and casing structure (e.g., the first connecting portion 3112 faces the casing side uniformly), adapting to different battery structures.

[0050] In some embodiments, the second current collector 331 includes a second main body portion 3311 and a second connecting portion 3312, wherein the second connecting portion 3312 is connected to one side of the second main body portion 3311;

[0051] The second main body portion 3311 of the plurality of negative electrode plates 33 is arranged sequentially along the thickness direction of the battery cell, and the second connecting portion 3312 of the plurality of negative electrode plates 33 is electrically connected to each other and welded to the second housing 20.

[0052] In this embodiment, the second main body 3311 serves as a substrate supporting the negative electrode active material, providing a uniform adhesion interface for the negative electrode active material (such as graphite). This ensures that the active material does not peel off or detach during repeated lithium ion insertion / extraction, maintaining the structural stability and cycle performance of the negative electrode sheet 33. During charging and discharging, it allows lithium ions to migrate efficiently between the electrolyte and the negative electrode active material, while simultaneously conducting the current generated by the active material to the second connection part 3312, ensuring a stable output of the negative electrode current to the external circuit.

[0053] The second connecting part 3312 is connected to one side of the second main body part 3311, which can lead out the current of a single negative electrode 33. Through the centralized electrical connection of multiple second connecting parts 3312, the dispersed current of the multilayer negative electrode 33 is integrated into a unified current, avoiding the loss caused by the dispersion of current between negative electrode layers and ensuring the conductivity efficiency of the negative electrode.

[0054] During assembly, the second connecting parts 3312 of multiple negative electrode sheets 33 can be connected to form a busbar group, and then the whole assembly can be welded to the second housing 20 to reduce assembly time and error rate, while avoiding thermal damage to the negative electrode active material caused by repeated welding and improving production yield.

[0055] The centralized current-collecting design of the second connection portion 3312 in this embodiment eliminates the path differences when electrons from each negative electrode 33 are individually conducted to the casing, avoiding mutual interference and loss of electrons during conduction, and making electron conduction on the negative electrode side more uniform. Moreover, the segmented structure of the second main body portion 3311 and the second connection portion 3312 can be flexibly adjusted according to the cell stacking thickness and the size of the second casing 20: for example, the thickness of the second main body portion 3311 can be reduced for thin cells, and the bending angle of the second connection portion 3312 can be adjusted for irregularly shaped casings, thus expanding the battery structure design space.

[0056] In some embodiments, the first connecting portions 3112 of a plurality of positive electrode plates 31 are electrically connected to each other to form a first bus terminal 310, and the first bus terminal 310 is welded to the first housing 10; and / or,

[0057] The second connecting portions 3312 of multiple negative electrode plates 33 are electrically connected to each other to form a second bus terminal 330, and the second bus terminal 330 is welded to the second housing 20.

[0058] Among them, the first connection part 3112 of multiple positive electrode plates 31 achieves electrical conduction through physical connection (such as stacking and pressurizing, laser welding), and is integrated into a first bus terminal 310 with a unified conductive interface; similarly, the second connection part 3312 of multiple negative electrode plates 33 is integrated into a second bus terminal 330 through the same logic, transforming the dispersed electrode conductive units into a single, centralized conductive module.

[0059] In this embodiment, the centralized design of the first busbar 310 and the second busbar 330 avoids the problem of impedance differences at multiple interfaces when the multi-layer connection parts are welded to the casing separately. This ensures the impedance consistency of the positive and negative conductive paths, reduces local voltage fluctuations caused by impedance unevenness, improves battery charging and discharging stability, and reduces overall conductive loss, thus optimizing energy output efficiency. Furthermore, compared to welding the multi-layer connection parts to the casing separately (requiring multiple welding operations), the single-point welding mode between the busbar and the casing significantly reduces the number of welding interfaces (e.g., the multi-layer positive electrode 31 only requires one welding interface at the first busbar 310), reducing the risk of interface oxidation, poor soldering, and other failures due to excessive welding operations, and improving battery connection reliability.

[0060] In some embodiments, the outermost positive electrode 31 of the battery cell is a first positive electrode 31, which is disposed facing the first housing 10, and the first current collector 311 of the first positive electrode 31 is welded to the inner wall of the first housing 10.

[0061] The negative electrode 33 located on the outermost side of the cell is the first negative electrode 33. The first negative electrode 33 is disposed facing the second housing 20, and the second current collector 331 of the first negative electrode 33 is welded to the inner wall of the second housing 20.

[0062] The first positive electrode 31 serves as the direct conductive medium between the positive electrode and the first housing 10. Its first current collector 311 is welded to the inner wall of the first housing 10, directly conducting the current of itself and the adjacent positive electrode 31 to the first housing 10, eliminating the intermediate current collection link and reducing conductive loss.

[0063] The first negative electrode 33 serves as the direct conductive medium between the negative electrode and the second housing 20. Its second current collector 331 is welded to the inner wall of the second housing 20, directly conducting the current of itself and the adjacent negative electrode 33 to the second housing 20, forming the shortest conductive path corresponding to the positive electrode, and ensuring the balance of positive and negative electrode currents.

[0064] In this embodiment, the welding connection between the outermost electrode and the shell provides bidirectional fixation for the battery cell, making the battery cell more firmly fixed in the receiving cavity 101. This can effectively resist vibration, impact, and expansion and contraction stress during charge and discharge cycles, and avoid conductive failure caused by battery cell displacement or loosening of intermediate components, thereby extending the battery cycle life and overall service life.

[0065] In some embodiments, the surface of the first positive electrode 31 facing the first housing 10 is a first empty foil area, and the first empty foil area is welded to the first housing 10.

[0066] The surface of the first negative electrode 33 facing the second housing 20 is the second empty foil area, which is welded to the second housing 20.

[0067] The first empty foil area serves as the welding area between the first positive electrode 31 and the first housing 10. The material of its first current collector 311 (such as aluminum foil) can form a stable metal welding joint with the first housing 10 (such as an aluminum alloy housing), ensuring welding strength and conductivity efficiency, and avoiding high-temperature damage to the active material.

[0068] The second empty foil area serves as the welding area between the first negative electrode 33 and the second housing 20. The material of its second current collector 331 (such as copper foil) is adapted to the second housing 20 (such as stainless steel housing or nickel-plated housing) for welding, forming a low-resistance, high-strength welding joint, while avoiding the pulverization and shedding of the negative electrode active material (such as silicon-based material) due to the high welding temperature.

[0069] In this embodiment, the empty foil area provides a metal welding interface between the current collector and the shell. Compared with the composite interface of the active material covering area and the current collector, it can significantly improve the metal bonding of the weld joint, reduce defects such as porosity and incomplete welding caused by active material inclusions, and at the same time ensure the high conductivity of the welding area and avoid the influence of the insulating properties of the active material on the conductive path.

[0070] In some embodiments, the first housing 10 is provided with a first slot corresponding to the first empty foil area, the opening of the first slot is away from the first empty foil area, and the first empty foil area is welded to the bottom wall of the first slot.

[0071] The second housing 20 has a second slot corresponding to the second empty foil area. The opening of the second slot is away from the second empty foil area, and the second empty foil area is welded to the bottom wall of the second slot.

[0072] In this embodiment, the first housing 10 has an opening in the first empty foil area and a first slot opposite to the empty foil area, and the second housing 20 has an opening in the second empty foil area and a second slot opposite to the empty foil area. The bottom wall of the slot forms a planar support structure that matches the empty foil area, so that the empty foil area and the bottom wall fit tightly together, avoiding gaps caused by insufficient flatness of the housing surface during welding.

[0073] In some embodiments, the secondary battery 100 further includes a first cover plate, which covers the first slot and is sealed to the outer wall of the first housing 10.

[0074] The secondary battery 100 also includes a second cover plate, which covers the second slot and is sealed to the outer wall of the second housing 20.

[0075] Because the openings of the first and second slots are away from the empty foil area, their slot openings are exposed to the outer wall of the shell, making them susceptible to external impacts and the intrusion of impurities. In this embodiment, the first and second cover plates respectively cover the first and second slots, forming a physical barrier that can isolate external dust, moisture, and mechanical collisions from damaging the welded joints inside the slots.

[0076] In this embodiment, the cover plate and the outer wall of the housing are connected by a sealed connection (such as laser welding seal or sealing ring seal). On the one hand, it can prevent foreign objects from entering the receiving cavity 101 through the slot gap, damaging the cell or causing a short circuit. On the other hand, it can enhance the overall sealing performance of the housing, avoid electrolyte leakage in the receiving cavity 101, and maintain a dry and inert environment inside the battery to ensure stable electrochemical performance.

[0077] In some embodiments, a first step is provided at the first slot, a first cover plate abuts against the first step, and the surface of the first cover plate is not higher than the surface of the first housing 10;

[0078] A second step is provided at the second slot, and the second cover plate abuts against the second step, and the surface of the second cover plate is not higher than the surface of the second housing 20.

[0079] In this embodiment, the first step and the second step form raised support structures in the first slot and the second slot, respectively. When the cover plate abuts against the step, the side of the step can restrict the horizontal displacement of the cover plate, so as to achieve automatic and accurate alignment between the cover plate and the slot and avoid misalignment.

[0080] The height of the step matches the thickness of the cover plate. After the cover plate abuts against the step, its surface is flush with or slightly lower than the surface of the casing. The physical limit of the step prevents the cover plate from bulging due to assembly pressure or dimensional deviation, ensuring that the outer wall of the battery is flat.

[0081] The design of the openings of the first and second slots in this application being opposite to the empty foil area provides a convenient operating space for ultrasonic welding between the bottom wall of the slot and the empty foil area: during welding operations, the ultrasonic welding probe can be directly inserted through the opening of the first slot, so that the probe can accurately act on the contact surface between the bottom wall of the first slot and the first empty foil area, and achieve solid connection between the two through high-frequency vibration; similarly, ultrasonic welding between the bottom wall of the second slot and the second empty foil area can be completed through the opening of the second slot, without the need to disassemble the shell or adjust the position of the battery cell, which greatly simplifies the welding operation.

[0082] After the welding process is completed and the welded joint cools and solidifies, the first cover plate is directly abutted against the side of the first step, so that the first cover plate is accurately positioned and covers the opening of the first slot, while ensuring that the surface of the first cover plate is not higher than the surface of the first housing 10; the second cover plate abuts against the second step and covers the opening of the second slot according to the same logic, and finally the cover plate is fixed by sealing connection (such as laser welding, sealing ring pressing).

[0083] This application also provides an electrical device, including the secondary battery 100 as described above. Specifically, the electrical device can be a new energy vehicle, a storage device, a computer, a mobile phone, or other electrical equipment. This electrical device can possess all the technical features and corresponding beneficial effects of the aforementioned secondary battery 100, which will not be elaborated further here.

[0084] The above are only some or preferred embodiments of this application. Neither the text nor the drawings should limit the scope of protection of this application. All equivalent structural transformations made using the content of this application's specification and drawings under the overall concept of this application, or direct / indirect applications in other related technical fields, are included within the scope of protection of this application.

Claims

1. A secondary battery, characterized in that, include: First shell; The second housing, the first housing and the second housing together form a receiving cavity, and the first housing and the second housing are insulated from each other; A battery cell is disposed in the receiving cavity. The battery cell includes a plurality of positive electrode plates, a plurality of separators and a plurality of negative electrode plates arranged in alternating layers. The separators are located between adjacent positive electrode plates and negative electrode plates. Each of the positive electrode plates includes a first current collector, the first current collectors of the plurality of positive electrode plates are electrically connected to each other and are welded to the first housing; each of the negative electrode plates includes a second current collector, the second current collectors of the plurality of negative electrode plates are electrically connected to each other and are welded to the second housing.

2. The secondary battery according to claim 1, characterized in that, The first current collector includes a first main body and a first connecting part, wherein the first connecting part is connected to one side of the first main body; The first main body portions of the plurality of positive electrode sheets are arranged sequentially along the thickness direction of the battery cell, and the first connecting portions of the plurality of positive electrode sheets are electrically connected to each other and welded to the first housing.

3. The secondary battery according to claim 2, characterized in that, The second current collector includes a second main body and a second connecting part, wherein the second connecting part is connected to one side of the second main body; The second main body portions of the plurality of negative electrode sheets are arranged sequentially along the thickness direction of the battery cell, and the second connecting portions of the plurality of negative electrode sheets are electrically connected to each other and welded to the second housing.

4. The secondary battery according to claim 3, characterized in that, The first connecting portions of the plurality of positive electrode plates are electrically connected to each other to form a first bus terminal, and the first bus terminal is welded to the first housing; and / or, The second connecting portions of the plurality of negative electrode plates are electrically connected to each other to form a second bus terminal, and the second bus terminal is welded to the second housing.

5. The secondary battery according to any one of claims 1 to 4, characterized in that, The outermost positive electrode plate of the battery cell is the first positive electrode plate, which is disposed facing the first housing, and the first current collector of the first positive electrode plate is welded to the inner wall of the first housing; The outermost negative electrode plate of the battery cell is the first negative electrode plate, which is disposed facing the second housing, and the second current collector of the first negative electrode plate is welded to the inner wall of the second housing.

6. The secondary battery according to claim 5, characterized in that, The surface of the first positive electrode facing the first housing is a first empty foil area, and the first empty foil area is welded to the first housing. The surface of the first negative electrode facing the second housing is the second empty foil area, which is welded to the second housing.

7. The secondary battery according to claim 6, characterized in that, The first housing has a first slot corresponding to the first empty foil area, the opening of the first slot is away from the first empty foil area, and the first empty foil area is welded to the bottom wall of the first slot. The second housing has a second slot corresponding to the second empty foil area. The opening of the second slot is away from the second empty foil area, and the second empty foil area is welded to the bottom wall of the second slot.

8. The secondary battery according to claim 7, characterized in that, The secondary battery also includes a first cover plate, which covers the first slot and is sealed to the outer wall of the first housing. The secondary battery also includes a second cover plate, which covers the second slot and is sealed to the outer wall of the second housing.

9. The secondary battery according to claim 8, characterized in that, A first step is provided at the first slot, the first cover plate abuts against the first step, and the surface of the first cover plate is not higher than the surface of the first shell. The second groove is provided with a second step, the second cover plate abuts against the second step, and the surface of the second cover plate is not higher than the surface of the second housing.

10. An electrical appliance, characterized in that, Includes the secondary battery as described in any one of claims 1 to 9.

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