BATTERY CELL, MANUFACTURING METHOD AND MANUFACTURING SYSTEM THEREFOR, BATTERY AND ELECTRIC DEVICE

The application provides a battery cell, a manufacturing method and a manufacturing system therefor, a battery and an electric device. The battery cell in one embodiment of the application includes a casing having an opening and provided with a pressure relief mechanism which is actuated to relieve an internal pressure or temperature of the battery cell when the internal pressure or temperature reaches a threshold value; an electrode assembly accommodated in the casing, and including a body portion and a tab portion protruding therefrom; and a cover assembly for covering the opening. A first recessed portion is formed on one side, abutting against the body portion and facing the electrode assembly, of the cover assembly. The cover assembly is provided with at least one first channel. The first channel can reduce the gas accumulated between the electrode assembly and the cover assembly, thereby reducing the safety risk.

TECHNICAL FIELD

The application relates to the technical field of batteries, and in particular to a battery cell, a manufacturing method and a manufacturing system therefor, a battery and an electric device.

BACKGROUND ART

Battery cells are widely used in electronic devices such as mobile phones, laptops, battery cars, electric vehicles, electric aircrafts, electric boats, electric toy cars, electric toy boats, electric toy planes, electric tools, etc. Battery cells can include nickel-cadmium battery cells, nickel-hydrogen battery cells, lithium ion battery cells and secondary alkaline zinc-manganese battery cells.

In the development of battery technology, safety is also an issue that cannot be ignored in addition to improving the performance of battery cells. If the safety of battery cells cannot be guaranteed, the battery cells cannot be used. Therefore, how to improve the safety of battery cells is an urgent technical issue to be solved in battery technology.

SUMMARY OF THE INVENTION

The application provides a battery cell, a manufacturing method and a manufacturing system therefor, a battery and an electric device, which can improve the safety of the battery.

In a first aspect, an embodiment of the application provides a battery cell, which includes:

a casing having an opening and provided with a pressure relief mechanism which is actuated to relieve an internal pressure or temperature of the battery cell when the internal pressure or temperature reaches a threshold value;

an electrode assembly accommodated in the casing, and including a body portion and a tab portion protruding therefrom; and

a cover assembly for covering the opening, with a first recessed portion formed on one side, abutting against the body portion and facing the electrode assembly, of the cover assembly, and configured to accommodate at least part of the tab portion;

wherein, the cover assembly is provided with at least one first channel for communicating the space between the electrode assembly and the casing with the first recessed portion, so as to introduce the gas in the first recessed portion into the space between the electrode assembly and the casing and enable the same to act on the pressure relief mechanism.

In the above solution, with the first channel arranged on the cover assembly, the gas in the first recessed portion can be introduced into the space between the electrode assembly and the casing in case of thermal runaway of the battery cell, which effectively lowers an increasing rate of air pressure between the electrode assembly and the cover assembly, reduces the gas accumulated between the electrode assembly and the cover assembly, mitigates the risk of explosion of the battery cell at the cover assembly, and improves the safety performance. The first channel can introduce the gas in the first recessed portion into the space between the electrode assembly and the casing, and enable the same to act on the pressure relief mechanism, so that the pressure relief mechanism can be actuated in time to rapidly release the high-temperature and high-pressure substances from the battery cell, thereby reducing the explosion risk.

In some embodiments, the cover assembly includes two first protrusion portions protruding from the bottom wall of the first recessed portion, and the first recessed portion is located between the two first protrusion portions in a first direction. The first protrusion portion is configured to abut against the body portion. In the first direction, the at least one first protrusion portion is provided with at least one of the first channels, and each of the first channels penetrates through the first protrusion portion along the first direction and communicates with the space between the electrode assembly and the casing.

In the above solution, the two first protrusion portions abut against the body portion so that the body portion will not shake as violently as the battery cell vibrates, thus reducing the risk of active substances falling off. The two first protrusion portions may allow the body portion to be uniformly stressed, which reduces stress concentration and improves the stability of the electrode assembly.

In some embodiments, at least one second recessed portion is formed on one side, away from the body portion, of the first protrusion portion, and forms at least part of the first channel. According to an embodiment of the application, the second recessed portion is configured to reduce the weight of the cover assembly and the strength of the first protrusion portion, improve the elasticity of the first protrusion portion, and migrate the risk that the body portion is crushed by the first protrusion portion when the battery cell vibrates.

In some embodiments, the first channel includes a first through hole and/or a first groove.

In some embodiments, the cover assembly further includes a second protrusion portion protruding from the bottom wall of the first recessed portion, and the second protrusion portion abuts against the body portion and is located between the two first protrusion portions. The first recessed portion includes a first part and a second part which are respectively positioned on two sides of the second protrusion portion along the first direction.

In the above solution, the second protrusion portion may abut against the body portion, which may allow the body portion to be uniformly stressed, and thus reduce stress concentration and improve the stability of the electrode assembly. The second protrusion portion may further increase the overall strength of the cover assembly, reduce the risk of deformation and collapse of the cover assembly, and improve the stability. In case of thermal runaway of the electrode assembly, one part of gas is released through an end face, facing the cover assembly, of the body portion; and the second protrusion portion abuts against the end face of the body portion, which can play a blocking role, reduce the rate of gas entering the first recessed portion and migrate the safety risk.

In some embodiments, the second protrusion portion is provided with a second channel for communicating the first part with the second part. In this embodiment, the second channel is configured to allow gas between the first part and the second part to flow, thereby improving the consistency of the air pressure in the first part and the air pressure in the second part.

In some embodiments, the cover assembly further includes two third protrusion portions protruding from the bottom wall of the first recessed portion which is located between the two third protrusion portions in a second direction perpendicular to the first direction. The third protrusion portion is configured to abut against the body portion, and two ends of the third protrusion portion are respectively connected to the two second protrusion portions.

In the above solution, the two third protrusion portions abut against the body portion so that the body portion will not shake as violently as the battery cell vibrates, thus reducing the risk of active substances falling off. The two third protrusion portions may allow the body portion to be uniformly stressed, which reduces stress concentration and improves the stability of the electrode assembly. The third protrusion portion may act as a gas barrier to reduce the gas entering the first recessed portion, which is generated by an outer surface of the body portion after being punctured by particles and short-circuited, and partially released from the punctured position; correspondingly, the risk of explosion of the battery cell at the cover assembly is reduced and the safety performance is improved.

In some embodiments, the electrode assembly includes a positive pole piece, a negative pole piece, and a separator for separating the positive pole piece from the negative pole piece, and is of a winding structure or a laminated structure. The outer surface of the electrode assembly includes two wide surfaces and two narrow surfaces, the area of the wide surfaces is larger than that of the narrow surfaces, the two wide surfaces are arranged opposite to each other along the second direction, and the two narrow surfaces are arranged opposite to each other along the first direction perpendicular to the second direction.

In some embodiments, a first gap exists between the narrow surface and the casing, a second gap exists between the wide surface and the casing, and the size of the first gap is larger than that of the second gap. The pole piece will expand along the thickness direction in the charging and discharging process of the electrode assembly. The largest expansion amount of the winding electrode assembly and the laminated electrode assembly is seen in the direction perpendicular to the wide surface. The wide surface will squeeze the casing as the electrode assembly expands, resulting in a small second gap, and correspondingly a low gas flow rate in the second gap. The first gap has a larger size than the second gap, and the gas flow rate in the first gap is higher than that in the second gap.

In some embodiments, the first channel is configured to communicate the first gap with the first recessed portion. In this embodiment, in case of thermal runaway of the battery cell, the gas in the first recessed portion can be quickly released to the first gap via the first channel, which is large enough to release the gas to the outside of the battery cell timely via the pressure relief mechanism.

In some embodiments, the cover assembly includes an end cover for covering the opening, and an insulating part located on one side, facing the body portion, of the end cover, and the first recessed portion is formed on one side, abutting against the body portion and facing the body portion, of the separator. The insulating part can insulate the end cover from the electrode assembly.

In some embodiments, the battery cell further includes an insulating film for covering the body portion to insulate the body portion from the casing, and an end, facing the end cover, of the insulating film surrounds an outer side of the insulating part and is connected to the insulating part. The insulating film is provided with a second through hole which is arranged opposite to the first channel to communicate with the first channel.

In the above solution, the insulating film may insulate the body portion from the casing, in order that the pole piece in the body portion and the casing will not be turned on even if the separator of the body portion is punctured by particles remaining in the casing; correspondingly, the risk of short circuit is reduced. In this embodiment, the second through hole is arranged to bypass the first channel of the insulating part, thereby reducing the area of the first channel blocked by the insulating film and ensuring the exhaust rate.

In a second aspect, an embodiment of the application provides a battery, including the battery cell according to any one of the embodiments of the first aspect.

In a third aspect, an embodiment of the application provides an electric device, including the battery of the second aspect, the battery is configured to provide electrical energy.

In a fourth aspect, an embodiment of the application provides a method for manufacturing a battery cell, including:

providing a casing which has an opening and is provided with a pressure relief mechanism;

providing an electrode assembly which includes a body portion and a tab portion protruding therefrom;

providing a cover assembly, with a first recessed portion formed on one side of the cover assembly;

connecting the cover assembly to the electrode assembly; and

placing the electrode assembly into the casing, and covering the opening of the cover assembly;

wherein, a first recessed portion is formed on one side, abutting against the body portion and facing the electrode assembly, of the cover assembly, and is configured to accommodate at least part of the tab portion; the cover assembly is provided with at least one first channel for communicating the space between the electrode assembly and the casing with the first recessed portion, so as to introduce the gas in the first recessed portion into the space between the electrode assembly and the casing and enable the same to act on the pressure relief mechanism; and the pressure relief mechanism is actuated to relieve an internal pressure or temperature of the battery cell when the internal pressure or temperature reaches a threshold value.

In a fifth aspect, an embodiment of the application provides a system for manufacturing a battery cell, including:

a first supply device, configured to provide a casing which has an opening and is provided with a pressure relief mechanism;

a second supply device, configured to provide an electrode assembly which includes a body portion and a tab portion protruding therefrom;

a third supply device, configured to supply a cover assembly, with a first recessed portion formed on one side of the cover assembly;

a first assembly device, configured to connect the cover assembly to the electrode assembly; and

a second assembly device, configured to place the electrode assembly into the casing and cover the opening of the cover assembly;

wherein, a first recessed portion is formed on one side, abutting against the body portion and facing the electrode assembly, of the cover assembly, and is configured to accommodate at least part of the tab portion; the cover assembly is provided with at least one first channel for communicating the space between the electrode assembly and the casing with the first recessed portion, so as to introduce the gas in the first recessed portion into the space between the electrode assembly and the casing and enable the same to act on the pressure relief mechanism; and the pressure relief mechanism is actuated to relieve an internal pressure or temperature of the battery cell when the internal pressure or temperature reaches a threshold value.

In the drawings, the components are not drawn to actual scale.

SPECIFIC EMBODIMENTS

To make the objectives, technical solutions, and advantages of the embodiments of the application clearer, the following will clearly describe the technical solutions in the embodiments of the application with reference to the accompanying drawings in the embodiments of the application. Apparently, the described embodiments are some rather than all of the embodiments of the application. Based on the embodiments of the application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the application.

Unless otherwise defined, all technical and scientific terms used in the application have the same meanings as those commonly understood by those who belong to the technical field of the present application. In the application, the terms used in the specification of the application are merely for the purpose of describing specific embodiments, and are not intended to limit the application. The terms “including” and “having” and any variations thereof in the specification and claims of the application and the above accompanying drawings are intended to cover non-exclusive inclusion. The terms “first”, “second”, etc. in the specification and claims of the application or the above accompanying drawings are used to distinguish different objects, but not to describe a specific order or primary and secondary relationship.

Reference to an “embodiment” in the application means that a specific feature, structure or characteristic described in conjunction with an embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments.

In the description of the application, it should be noted that, unless otherwise explicitly specified and defined, the terms “mounting”, “connecting”, “connection” and “attachment” should be understood in a broad sense, for example, they may be a fixed connection, a detachable connection, or an integrated connection; and may be a direct connection, or an indirect connection via an intermediate medium, or communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the application could be understood according to specific circumstances.

As used herein, the term “and/or” is merely used to describe an associated relationship between associated objects and means three relationships, for example, A and/or B may mean A alone, A and B together, and B alone. In addition, the character “/” in the application generally indicates that the associated objects are an “or” relationship.

In the embodiments of the application, the same reference numerals refer to same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that a thickness, a length, a width and other dimensions of various components and an overall thickness, length, width and other dimensions of an integrated device shown in the accompanying drawings in the embodiments of the application are merely exemplary, and should not constitute any limitation on the application.

The term “plurality” in the application means two or more.

In the application, battery cells may include a lithium ion secondary battery cell, a lithium ion primary battery cell, a lithium-sulfur battery, a sodium lithium-ion battery cell, a sodium ion battery cell, a magnesium ion battery cell, etc., which are not limited by the embodiments of the application. The battery cell may be in cylindrical, flat, cuboid or other shapes, which is not limited by the embodiments of the application. Generally, the battery cells are divided into three types according to packaging manners: cylindrical battery cells, square battery cells and pouch battery cells, which are not limited by the embodiments of the application.

The battery mentioned in the embodiments of the application refers to a single physical module which includes one or a plurality of battery cells and therefore provides a higher voltage and capacity. For example, the battery mentioned in the application may include a battery module or a battery pack, etc. Generally, the battery includes a box for packaging one or a plurality of battery cells. The box may prevent liquid or other foreign matter from affecting charging or discharging of the battery cell.

The battery cell includes an electrode assembly and an electrolyte, and the electrode assembly includes a positive pole piece, a negative pole piece and a separator. The battery cell works mainly depending on movement of metal ions between the positive pole piece and the negative pole piece. The positive pole piece includes a positive current collector and a positive active material layer coated on a surface of the positive current collector; the positive current collector includes a positive current collecting portion and a positive protrusion portion protruding from the positive current collecting portion, the positive current collecting portion is coated with the positive active material layer, at least part of the positive protrusion portion is not coated with the positive active material layer, and the positive protrusion portion serves as a positive tab. Taking a lithium ion battery as an example, the positive current collector may be made of aluminum, and the positive active material layer includes a positive active material which may be lithium cobaltate, lithium iron phosphate, ternary lithium or lithium manganate. The negative pole piece includes a negative current collector and a negative active material layer coated on a surface of the negative current collector; the negative current collector includes a negative current collecting portion and a negative protrusion portion protruding from the negative current collecting portion, the negative current collecting portion is coated with the negative active material layer, at least part of the negative protrusion portion is not coated with the negative active material layer, and the negative protrusion portion serves as a negative tab. The negative current collector may be made of copper, and the negative active material layer includes a negative active material which may be carbon or silicon. In order to guarantee fusing does not occur during large current flow, a plurality of positive tabs are stacked together, and a plurality of negative tabs are stacked together. The separator may be made of polypropylene (PP) or polyethylene(PE). In addition, the electrode assembly may be in a winding structure or a laminated structure, which is not limited in the embodiments of the application.

The battery cell further includes a casing having an opening, and a cover assembly for covering the opening to form a sealed connection, so as to form an accommodating cavity for accommodating the electrode assembly and an electrolyte.

For a battery cell, the main safety hazard comes from charging and discharging processes, suitable ambient temperature design is also needed, and there are generally at least three protective measures for the battery cell for effectively avoiding unnecessary losses. Specifically, the protective measures at least include switching elements, appropriate materials of the separator and the pressure relief mechanisms. The switch element is an element capable of stopping charging or discharging the battery when a temperature or resistance in the battery cell reaches a certain threshold value. The separator is configured to separate the positive pole piece from the negative pole piece, and may automatically dissolve the micro-scale (even nano-scale) micropores attached to the separator when the temperature rises to a certain value, thereby preventing metal ions from passing through the separator and terminating the internal reaction of the battery cell.

The pressure relief mechanism refers to an element or component that is actuated to relieve internal pressure or temperature of the battery cell when the internal pressure or temperature reaches a preset threshold value. The threshold value is designed differently according to different design requirements. The threshold value may depend on one or more materials of the positive pole piece, the negative pole piece, the electrolyte and the separator in the battery cell. The pressure relief mechanism may be an explosion-proof valve, an air valve, a pressure relief valve or a safety valve, and specifically structured as pressure-sensitive elements, that is, when the internal pressure or temperature of the battery cell reaches a predetermined threshold value, the pressure relief mechanism will act or the weak structure provided in the pressure relief mechanism will break, thus forming an opening or channel for releasing the internal pressure or temperature.

The “actuation” mentioned in the application means that the pressure relief mechanism acts or is activated to a certain state, so that the internal pressure or temperature of the battery cell can be released. The action produced by the pressure relief mechanism may include, but is not limited to, at least a portion of the pressure relief mechanism breaking, crushing, being torn, or opened, etc. When the pressure relief mechanism is actuated, a high-temperature and high-pressure substance in the battery cell may be discharged outwards from an actuated portion as emissions. In this way, the pressure of the battery cell can be relieved under the condition of controllable pressure, thereby avoiding a potentially more serious accident.

Emissions from battery cells mentioned in the application include, but are not limited to, electrolyte, positive and negative pole pieces dissolved or split, fragments of separators, high-temperature and high-pressure gas and flame produced by reaction, and so on.

The pressure relief mechanism on the battery cell has an important influence on the safety of the battery cell. For example, the phenomena including short circuit and overcharge may lead to thermal runaway and sudden pressure rise inside the battery cell. In this case, the internal pressure may be released outward through the actuation of the pressure relief mechanism to prevent the battery cell from exploding and catching fire.

The pressure relief mechanism may be arranged on the cover assembly or the casing. The inventors found that, with the pressure relief mechanism arranged on the casing, in case of thermal runaway of the battery cell, the gas released from the battery cell is easy to accumulate between the cover assembly and the electrode assembly; blocked by the cover assembly, the gas cannot be released from the pressure relief mechanism in time, causing potential safety hazards.

In view of this, an embodiment of the application provides a technical solution, in which the battery cell includes a casing having an opening and provided with a pressure relief mechanism which is actuated to relieve an internal pressure or temperature of the batter cell when the internal pressure or temperature reaches a threshold value; an electrode assembly accommodated in the casing, and including a body portion and a tab portion protruding therefrom; and a cover assembly for covering the opening, with a first recessed portion formed on one side, abutting against the body portion and facing the electrode assembly, of the cover assembly, and configured to accommodate at least part of the tab portion. wherein, the cover assembly is provided with at least one first channel for communicating the space between the electrode assembly and the casing with the first recessed portion, so as to introduce the gas in the first recessed portion into the space between the electrode assembly and the casing and enable the same to act on the pressure relief mechanism. With the structure, the battery cell can lead out the gas between the cover assembly and the electrode assembly and release the same through the pressure relief mechanism in case of thermal runaway, thus improving the exhaust rate and safety performance.

The technical solution described in the embodiment of the application is applicable to batteries and electric devices using the batteries.

The electric devices may be vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys and electric tools. The vehicles may be fuel vehicles, gas vehicles or new energy vehicles, and the new energy vehicles may be battery electric vehicles, hybrid electric vehicles, extended-range vehicles, etc. The spacecrafts include airplanes, rockets, space shuttles, spaceships, etc. The electric toys include fixed or mobile electric toys, such as game machines, electric car toys, electric ship toys and electric airplane toys. The electric tools include metal cutting electric tools, electric grinding tools, electric assembling tools and electric tools for railways, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact electric drills, concrete vibrators, electric planers, etc. The embodiment of the application does not impose special restrictions on the above-mentioned electric devices.

For the sake of illustration, the following embodiments are illustrated with a vehicle as an electric device.

FIG.1is a schematic structural diagram of a vehicle provided in some embodiments of the application. As shown inFIG.1, a battery2is disposed inside a vehicle1, and the battery2may be disposed at the bottom, head or tail of the vehicle1. The battery2may be used for supplying electricity to the vehicle1, for example, the battery2may be used as an operating power source for the vehicle1.

The vehicle1may further include a controller3and a motor4, where the controller3is used for controlling the battery2to supply electricity to the motor4to be used for, for example, operating electricity requirements during start-up, navigation and running of the vehicle1.

In some embodiments of the application, the battery2may not only serve as the operating power source for the vehicle1, but also serve as a driving power source for the vehicle1, so as to replace or partially replace fuel or natural gas to provide driving power for the vehicle1.

FIG.2is an exploded view of a battery provided in some embodiments of the application. As shown inFIG.2, the battery2includes a box5and a battery cell (not shown inFIG.2), and the battery cell is accommodated in the box5.

The box5is used for accommodating the battery cell and may be of various structures. In some embodiments, the box5may include a first box portion51and a second box portion52, the first box portion51and the second box portion52may cover each other, and the first box portion51and the second box portion52define an accommodation space53for accommodating the battery cell together. The second box portion52may be of a hollow structure with an opening end, the first box portion51is of a plate-like structure, and the first box portion51covers an opening side of the second box portion52so as to form the box5with the accommodation space53. The first box portion51and the second box portion52may be both of hollow structures with opening sides, and an opening side of the first box portion51covers the opening side of the second box portion52so as to form the box5with the accommodation space53. Of course, the first box portion51and the second box portion52may be in various shapes, such as a cylinder or a cuboid.

In order to improve sealability after the first box portion51and the second box portion52are connected, a sealing member, such as a sealant or a sealing ring, may be arranged between the first box portion51and the second box portion52.

Assuming that the first box portion51covers a top portion of the second box portion52, the first box portion51may also be referred to as an upper box cover, and the second box portion52may also be referred to as a lower box.

There may be one or more battery cells in the battery2. If there are a plurality of battery cells, the plurality of battery cells may be connected in series, in parallel, or in a series-parallel manner. The plurality of battery cells may be directly connected in series, in parallel, or in a series-parallel manner, and then a whole formed by the plurality of battery cells is accommodated in the box5. Of course, the plurality of battery cells may be connected in series, in parallel, or in a series-parallel manner first to form a battery module6, and then a plurality of battery modules6are connected in series, in parallel, or in a series-parallel manner to form a whole to be accommodated in the box5.

FIG.3is a schematic structural diagram of the battery module shown inFIG.2. As shown inFIG.3, in some embodiments, a plurality of battery cells7are provided, and the plurality of battery cells7are connected in series, in parallel or in parallel-series to form battery modules6, then the plurality of battery modules6are connected in series, in parallel or in parallel-series to form a single unit, and are accommodated in the box.

The plurality of battery cells7in the battery module6may be electrically connected to each other by means of bus components, so as to be connected in series, in parallel, or in a series-parallel manner.

FIG.4is an exploded view of a battery cell provided in some embodiments of the application.

As shown inFIG.4, the battery cell7provided in one embodiment of the application includes an electrode assembly10, a casing20and a cover assembly30.

The casing20is a hollow structure with one side open, and the cover assembly30covers the opening of the casing20to form a sealed connection, so as to form an accommodating cavity for accommodating the electrode assembly10and electrolyte.

The housing20may take a variety of shapes, such as cylinder and cuboid. The shape of the housing20may be determined according to the specific shape of the electrode assembly10. For example, if the electrode assembly10is of a cylindrical structure, a cylindrical casing may be selected and used. If the electrode assembly10is of a cuboid structure, a cuboid casing may be selected and used.

In some embodiments, the cover assembly30includes an end cover31for covering the opening of the casing20. The end cover31may be of various structures, for example, a plate-like structure, a hollow structure with one end open, or the like. Exemplarily, inFIG.4, the housing20is a cuboid structure, and the end cover31is a plate-like structure and covers an opening at the top of the housing20.

The end cover31may be made of an insulating material (e.g. plastic) or a conductive material (e.g. metal). In case that the end cover31is made of conductive material, the cover assembly30may further include an insulating part32located on one side, facing the electrode assembly10, of the end cover31to insulate the end cover31from the electrode assembly10.

In some embodiments, the cover assembly30may further include an electrode terminal33mounted on the end cover31. Two electrode terminals33are provided and defined as a positive electrode terminal and a negative electrode terminal respectively which are electrically connected to the electrode assembly10to output the electric energy generated by the electrode assembly10.

In other embodiments, the battery cell7includes a casing20having a hollow structure with opposite sides open, and two cover assemblies30for covering two openings of the casing20correspondingly to form a sealed connection, so as to form an accommodating cavity for accommodating the electrode assembly10and an electrolyte. With the structure, one cover assembly30may be provided with two electrode terminals33while the other cover assembly30is not provided with an electrode terminal33; alternatively, both cover assemblies30may be provided with one electrode terminal33respectively.

In the battery cell7, there may be one or more electrode assemblies10accommodated in the housing20. Illustratively, inFIG.4, there are two electrode assemblies10.

FIG.5is a structural representation of an electrode assembly of a battery cell provided according to some embodiments of the application; andFIG.6is a structural representation of an electrode assembly of a battery cell provided according to other embodiments of the application.

As shown inFIG.5andFIG.6, the electrode assembly10includes a positive pole piece11, a negative pole piece12, and a separator13for separating the positive pole piece11from the negative pole piece12, and the electrode assembly10is of a winding structure or a laminated structure.

As shown inFIG.5, in some embodiments, the electrode assembly10is of a winding structure. The positive pole piece11, the negative pole piece12and the separator13are strip structures. In this embodiment of the application, the positive pole piece11, the separator13and the negative pole piece12may be sequentially laminated and wound for more than two turns to form an flat electrode assembly10. The electrode assembly10may be directly wound into a flat form, or firstly wound into a hollow cylindrical structure and then flattened.

FIG.5illustrates the outline of the winding electrode assembly10. The outer surface of the electrode assembly10includes two wide surfaces14with the flat surfaces arranged opposite to each other, and two narrow surfaces15arranged opposite to each other and connected to the two wide surfaces14substantially parallel to the winding axis of the electrode assembly10as a surface with the largest area. The wide surface14may be a relatively flat surface, and is not required to be purely flat. The narrow surface15is at least partially a circular arc surface. The area of the wide surface14is larger than that of the narrow surface15.

In an alternative embodiment, as shown inFIG.6, the electrode assembly10is a laminated structure. Specifically, the electrode assembly10includes a plurality of positive pole pieces11and a plurality of negative pole pieces12, which are alternately stacked. In the laminated structure, both the positive pole piece11and the negative pole piece12are in from of sheets, with the lamination direction generally parallel to the thickness direction of the positive pole piece11and the negative pole piece12.

FIG.6illustrates the outline of the laminated electrode assembly10. The outer surface of the electrode assembly10includes two wide surfaces14arranged opposite to each other, and two narrow surfaces15arranged opposite to each other and connected to the two wide surfaces14as a surface with the largest area. The wide surface14may be a relatively flat surface, and is not required to be purely flat. The narrow surface15is at least partially a circular arc surface. The area of the wide surface14is larger than that of the narrow surface15.

FIG.7is a sectional view of a battery cell provided in some embodiments of the application;FIG.8is an enlarged view of the battery cell shown inFIG.7at the round frame A; andFIG.9is a structural representation of an insulating part of a cover assembly of a battery cell provided in some embodiments of the application.

As shown inFIG.7toFIG.9, the battery cell7in one embodiment of the application includes a casing20having an opening21and provided with a pressure relief mechanism40which is actuated to relieve an internal pressure or temperature of the battery cell7when the internal pressure or temperature reaches a threshold value; an electrode assembly10accommodated in the casing20, and including a body portion16and a tab portion17protruding therefrom; and a cover assembly30for covering the opening21; and a first recessed portion321is formed on one side, abutting against the body portion16and facing the electrode assembly10, of the cover assembly30, and is configured to accommodate at least part of the tab portion17; wherein the cover assembly30is provided with at least one first channel322for communicating the space between the electrode assembly10and the casing20with the first recessed portion321, so as to introduce the gas in the first recessed portion321into the space between the electrode assembly10and the casing20and enable the same to act on the pressure relief mechanism40.

In terms of the shape, the electrode assembly10includes a body portion16and a tab portion17connected thereto. Exemplarily, the tab portion17extends from an end, near the cover assembly30, of the body portion16.

In some embodiments, two tab portions17are provided and defined as a positive tab portion and a negative tab portion respectively. The positive tab portion and the negative tab portion may extend from the same end of the body portion16, or may extend from opposite ends of the body portion16respectively.

As a core part of the electrode assembly10, the body portion16is designed to realize the charging and discharging function, and generates current led out by the tab portion17. The body portion16includes a positive current collecting portion of a positive current collector, a positive active material layer, a negative current collecting portion of a negative current collector, a negative active material layer and a separator13. The positive tab portion includes a plurality of positive tabs, and the negative tab portion includes a plurality of negative tabs.

By design, the tab portion17is electrically connected to the electrode terminals33, for example, by means of a welding method, or an indirect method featuring combination of other members. For instance, the battery cell7further includes a current collecting member50for electrically connecting the electrode terminal33and the tab portion17. Two current collecting members50are provided and respectively defined as a positive current collecting member for electrically connecting the positive electrode terminal and the positive tab portion, and a negative current collecting member for electrically connecting the negative electrode terminal and the negative tab portion.

The pressure relief mechanism40may be disposed in the casing20as a part or a separate structure of the casing20. The casing20is provided with a through pressure relief hole22which is sealed by the pressure relief mechanism40fixed to the casing20by means of a welding method, so as to separate the space between the inside and outside of the casing20and prevent electrolyte from flowing out through the pressure relief hole22during normal operation.

The casing20may include a bottom plate23located at one side, away from the cover assembly30, of the body portion16, and a side plate24for connecting the bottom plate23and the end cover31. The pressure relief mechanism40may be arranged on the bottom plate23or the side plate24.

By design, the pressure relief mechanism40is actuated to relieve an internal pressure or temperature of the battery cell7when the internal pressure or temperature reaches a threshold value. In case the gas generated by the battery cell7is excessive to increase the internal pressure or temperature inside the casing20to a threshold value, the pressure relief mechanism40will execute an action or the weak structure provided in the pressure relief mechanism40will be broken, enabling the gas and other high-temperature and high-pressure substances to be released outward through a cracked opening of the pressure relief mechanism40and the pressure relief hole22, and thus preventing an explosion of the battery cell7.

The pressure relief mechanism40may be of various possible pressure relief structures, which is not limited herein. For example, the pressure relief mechanism40may be a pressure-sensitive pressure relief mechanism or a temperature-sensitive pressure relief mechanism. The pressure-sensitive pressure relief mechanism is configured to break when the internal air pressure of the battery cell7provided with the pressure-sensitive pressure relief mechanism reaches a threshold value; while the temperature-sensitive pressure relief mechanism is configured to break when the internal temperature of the battery cell7provided with the temperature-sensitive pressure relief mechanism reaches a threshold value.

In some embodiments, nicks, grooves or other structures are made on the pressure relief mechanism40to reduce local strength and form a weak structure which will be broken as the internal pressure of the battery cell7reaches a threshold value, and along the broken part the pressure relief mechanism40is folded to form an opening for releasing the high-temperature and high-pressure substances.

The cover assembly30may directly abut against the end face, facing the cover assembly30, of the body portion16, or may indirectly abut against the body portion16by means of other members. The cover assembly30presses against one side of the body portion16so that the body portion16will not shake in the casing20as violently as the battery cell7vibrates, thus reducing the risk of active substances falling off the electrode assembly10.

The first recessed portion321may be made on one side, facing the electrode assembly10, of the end cover31in case the end cover31of the cover assembly30is made of an insulating material, or made on one side, facing the electrode assembly10, of the insulating part32in case the end cover31of the cover assembly30is made of a conductive material and the cover assembly30includes a separator32.

The first recessed portion321is configured to accommodate at least part of the tab portion17; namely, the tab portion17may be accommodated in the first recessed portion321in part or in whole. By providing the first recessed portion321, more space may be vacated for the electrode assembly10, which improves the energy density of the battery cell7. At least part of the current collecting member50may also be accommodated in the first recessed portion321.

According to an embodiment of the application, the first channel322of the cover assembly30may be made by removing part of the material of the cover assembly30. The shape of the first channel322is not limited in the application, for example, the first channel322can be formed by opening grooves and/or holes on the cover assembly30. The first channel322of the cover assembly30is a space not filled with solids, through which fluids (e.g. gas and liquid) can flow.

The first channel322communicates the space between the electrode assembly10and the casing20with the first recessed portion321, and the fluid in the first recessed portion321can flow into the space between the electrode assembly10and the casing20via the first channel322.

The space between the electrode assembly10and the casing20may be in direct communication with the first channel322, or may be in indirect communication therewith via holes, gaps or other spatial structures.

In case of short circuit or overcharge, the electrode assembly10is under thermal runaway and releases high-temperature and high-pressure substances such as high-temperature and high-pressure gas, which partially enters the first recessed portion321, or is introduced into the space between the electrode assembly10and the casing20by the first channel322. With the gradual increase of gas in the space between the electrode assembly10and the casing20, the pressure of the pressure relief mechanism40increases and finally reaches a threshold value. Afterwards, the pressure relief mechanism40is actuated to release gas and other high-temperature and high-pressure substances to the outside of the battery cell7, thereby releasing the internal pressure of the battery cell7and preventing explosion and fire of the battery cell7.

Exemplarily, with the pressure relief mechanism40actuated to open the pressure relief hole22, the space between the electrode assembly10and the casing20communicates with the pressure relief hole22. The gas in the first recessed portion321is released through the first channel322, the space between the electrode assembly10and the casing20, and the pressure relief hole22.

According to an embodiment of the application, the shape and position of the first channel322are not limited, as long as the space between the electrode assembly10and the casing20is in communication with the first recessed portion321via the first channel322. The first channel322may be a hole, a groove, a combination of holes and grooves, or other communication structures.

The first channel322may be made on the end cover31in case the end cover31of the cover assembly30is made of an insulating material; and the first recessed portion321may be made on the insulating part32when the end cover31of the cover assembly30is made of a conductive material and the cover assembly30includes the insulating part32.

According to an embodiment of the application, with the first channel322arranged on the cover assembly30, the gas in the first recessed portion321can be introduced into the space between the electrode assembly10and the casing20in case of thermal runaway of the battery cell7, which effectively lowers an increasing rate of air pressure between the electrode assembly10and the cover assembly30, reduces the gas accumulated between the electrode assembly10and the cover assembly30, mitigates the risk of explosion of the battery cell7at the cover assembly30, and improves the safety performance. The first channel322can introduce the gas in the first recessed portion321into the space between the electrode assembly10and the casing20, and enable the same to act on the pressure relief mechanism40, so that the pressure relief mechanism40can be actuated in time to rapidly release the high-temperature and high-pressure substances from the battery cell7, thereby reducing the explosion risk.

In some embodiments, the cover assembly30includes two first protrusion portions323protruding from the bottom wall of the first recessed portion321which is located between the two first protrusion portions323in the first direction X. The first protrusion portion323is configured to abut against the body portion16. In the first direction X, at least one first protrusion portion323is provided with at least one first channel322which passes through the first protrusion portion323along the first direction X and is in communication with the space between the electrode assembly10and the casing20.

The cover assembly30has a first inner surface32afor abutting against the body portion16; and the first recessed portion321is recessed in a direction away from the body portion16with respect to the first inner surface32a.The first inner surface32aincludes a surface, abutting against the body portion16, of the first protrusion portion323. Optionally, the first inner surface32ais a plane.

It should be noted that the at least one first protrusion portion323is provided with the at least one first channel322in the following ways: one first protrusion portion323is provided with one first channel322and the other first protrusion portion323is not provided with the first channel322; alternatively, one first protrusion portion323is provided with one first channel322and the other first protrusion portion323is provided with one first channel322;

alternatively, one first protrusion portion323is provided with one first channel322and the other first protrusion portion323is provided with a plurality of first channels322; alternatively, one first protrusion portion323is provided with a plurality of first channels322and the other first protrusion portion323is not provided with the first channel322; alternatively, the two first protrusion portions323are both provided with a plurality of first channels322.

The first protrusion portion323has two first side surfaces arranged opposite to each other along the first direction X, and having openings at both ends of the first channel322respectively. The openings at both ends of the first channel322may be aligned to the first direction X, or arranged in a staggered manner.

According to an embodiment of the application, the two first protrusion portions323abut against the body portion16so that the body portion16will not shake as violently as the battery cell7vibrates, thus reducing the risk of active substances falling off. The two first protrusion portions323may allow the body portion16to be uniformly stressed, which reduces stress concentration and improves the stability of the electrode assembly10.

In some embodiments, the first protrusion portion323and the casing20are arranged at an interval in the first direction X, so that the casing20does not block the first channel322and the gas in the first recessed portion321can be smoothly released through the first channel322.

Taking the cover assembly30(including the insulating part32) as an example, the first inner surface32ais the surface, facing the body portion16, of the separator32. The insulating part32includes a first recessed portion321and two first protrusion portions323. Exemplarily, the two first protrusion portions323are respectively located at both ends of the insulating part32along the first direction X.

In some embodiments, at least one second recessed portion324is formed on one side, facing away from the body portion16, of the first protrusion portion323, and forms at least part of the first channel322.

According to an embodiment of the application, the second recessed portion324is configured to reduce the weight of the cover assembly30and the strength of the first protrusion portion323, improve the elasticity of the first protrusion portion323, and migrate the risk that the body portion16is crushed by the first protrusion portion323when the battery cell7vibrates.

Taking the cover assembly30(including the insulating part32) as an example, the insulating part32includes a first inner surface32aand a first outer surface32bwhich are arranged opposite to each other, and the first outer surface32bfaces the end cover31. The second recessed portion324is recessed in a direction close to and away from the end cover31with respect to the first outer surface32b.The end cover31is attached to the first outer surface32band covers the second recessed portion324.

In some embodiments, the first channel322includes a first through hole322aand/or a first groove.

The first groove is recessed in a direction away from the body portion16with respect to the first inner surface32a.Two ends of the first groove extend to two first sides of the first protrusion portion323respectively along the first direction X.

The first through hole322apenetrates through the first protrusion portion323along the first direction X, that is, both ends of the first through hole322aextend to two first side surfaces of the first protrusion portion323respectively along the first direction X.

The first channel322may include only the first through hole322a,only the first groove, or both the first through hole322aand the first groove. Certainly, the first channel322may further include other communication structures, for example, the first channel322may further include a second recessed portion324.

In some embodiments, the first channel322includes the first through hole322aand the second recessed portion324in communication with the first through hole322a.

In some embodiments, the cover assembly30further includes a second protrusion portion325protruding from the bottom wall of the first recessed portion321, and the second protrusion portion325abuts against the body portion16and is located between the two first protrusion portions323. The first recessed portion321includes a first part321aand a second part321b,which are located on both sides of the second protrusion portion325along the first direction X, respectively.

The number of the second protrusion portion325may be one or more. If a plurality of second protrusion portions325are provided, the plurality of second protrusion portions325may be arranged at an interval along the first direction X. The second protrusion portion325divides the first recessed portion321into a plurality of parts.

The first part321aand the second part321bmay be communicated by other structures, or blocked from each other.

The second protrusion portion325may abut against the body portion16, so that the body portion16is uniformly stressed to reduce stress concentration and improve the stability of the electrode assembly10. The second protrusion portion325may also increase the overall strength of the cover assembly30, reduce the risk of deformation and collapse of the cover assembly30, and improve the stability.

In case of thermal runaway of the electrode assembly10, a part of gas is released via the end face, facing the cover assembly30, of the body portion16; and the second protrusion portion325abuts against the end face of the body portion16to play a blocking role, which further decreases the rate of gas entering the first recessed portion321, and reduces the safety risk.

In some embodiments, the second protrusion portion325is provided with a second channel326for communicating the first part321awith the second part321b.

In the application, with the second channel326arranged, the gas can flow between the first part321aand the second part321b,thereby improving the consistency of the air pressure in the first part321aand the air pressure in the second part321b.

In some embodiments, the second channel326includes a third through hole326awhich penetrates through the second protrusion portion325along the first direction X, and/or a second groove (not shown) which is recessed in a direction away from the body portion16with respect to the surface, abutting against the body portion16, of the second protrusion portion325; and the second groove penetrates through the second protrusion portion325in the first direction X.

In some embodiments, the second protrusion portion325is formed on the insulating part32which is further provided with a third recessed portion327located on one side, away from the body portion16, of the second protrusion portion325. The third recessed portion327is recessed in a direction close to the body portion16with respect to the first outer surface32b,and forms at least part of the second channel326.

FIG.10is a structural representation of an insulating part of a cover assembly provided in other embodiments of the application.

As shown inFIG.10, in some embodiments, the cover assembly further includes two third protrusion portions328protruding from the bottom wall of the first recessed portion321which is located between the two third protrusion portions328in the second direction Y perpendicular to the first direction X. The third protrusion portion328is configured to abut against the body portion, and both ends of the third protrusion portion328are connected to the two second protrusion portions325respectively.

According to an embodiment of the application, the third protrusion portions328abut against the body portion so that the body portion will not shake as violently as the battery cell vibrates, thus reducing the risk of active substances falling off. The two third protrusion portions328may allow the body portion to be uniformly stressed, which reduces stress concentration and improves the stability of the electrode assembly.

The third protrusion portion328may act as a gas barrier to reduce the gas entering the first recessed portion321, which is generated by an outer surface of the body portion after being punctured by particles and short-circuited, and partially released from the punctured position;

correspondingly, the risk of explosion of the battery cell at the cover assembly is reduced and the safety performance is improved.

Exemplarily, the two third protrusion portions328are located at both ends of the insulating part32along the second direction Y respectively.

In some embodiments, the first channel322includes a first through hole322aand a first groove322b.

FIG.11is another sectional view of a battery cell provided in some embodiments of the application.

As shown inFIG.11, in some embodiments, the electrode assembly10includes a positive pole piece, a negative pole piece, and a separator for separating the positive pole piece from the negative pole piece, and is of a winding structure or a laminated structure.

The outer surface of the electrode assembly10includes two wide surfaces14and two narrow surfaces15, the area of the wide surfaces14is larger than that of the narrow surfaces15, the two wide surfaces14are arranged opposite to each other along the second direction Y, and the two narrow surfaces15are arranged opposite to each other along the first direction X perpendicular to the second direction Y.

In some embodiments, a first gap G1exists between the narrow surface15and the casing20, a second gap G2exists between the wide surface14and the casing20, and the size of the first gap G1is larger than that of the second gap G2.

The pole piece10will expand along the thickness direction in the charging and discharging process of the electrode assembly. The largest expansion amount of the winding electrode assembly10and the laminated electrode assembly10is seen in the direction perpendicular to the wide surface14. The wide surface14will squeeze the casing20as the electrode assembly10expands, resulting in a small second gap G2, and correspondingly a low gas flow rate in the second gap G2. The first gap G1has a larger size than the second gap G2, and the gas flow rate in the first gap G1is higher than that in the second gap.

In some embodiments, the first channel is configured to communicate the first gap G1with the first recessed portion. In this way, in case of thermal runaway of the battery cell7, the gas in the first recessed portion can be quickly released to the first gap G1via the first channel, which is large enough to release the gas to the outside of the battery cell7timely via the pressure relief mechanism.

In some embodiments, referring toFIG.7andFIG.11, the casing20includes a bottom plate23, which, together with the cover assembly30, is respectively located on both sides of the electrode assembly10along the third direction Z. In the third direction Z, a third gap G3exists between the bottom plate23and the electrode assembly10, and is in communication with the second gap G2and the first gap G1respectively.

FIG.12is a sectional view of a battery cell provided in other embodiments of the application; andFIG.13is an enlarged view of a battery cell shown inFIG.12at the round frame B.

As shown inFIG.12andFIG.13, the cover assembly30includes an end cover31for covering the opening, and an insulating part32located on one side, facing the body portion16, of the end cover31, and the first recessed portion321is formed on one side, abutting against the body portion16and facing the body portion16, of the insulating part32.

In some embodiments, the battery cell7further includes an insulating film60for covering the body portion16to insulate the body portion16from the casing20, and an end, facing the end cover31, of the insulating film60surrounds an outer side of the insulating part32and is connected to the insulating part32. The insulating film60is provided with a second through hole61, which is arranged opposite to the first channel322to communicate with the first channel322.

The assembly of the battery cell7may produce particles (e.g., metal particles generated in the welding process), which will remain in the casing20. If adhering to the surface of the body portion16, particles may puncture the separator of the body portion16so that the casing20and the body portion16are electrically connected; alternatively, particles may also fall into the body portion16and allow the positive and negative pole pieces to be electrically connected, resulting in short circuit and safety risk.

In the application, the insulating film60may be configured to insulate the body portion16from the casing20, in order that the pole piece in the body portion16and the casing20will not be electrically connected even if the separator of the body portion16is punctured by particles remaining in the casing20; correspondingly, the risk of short circuit is reduced.

The second through hole61is configured to communicate the space (e.g. the first gap G1) between the casing20and the electrode assembly10with the first channel322. According to an embodiment of the application, the second through hole61is arranged to bypass the first channel322of the insulating part32, thereby reducing the area of the first channel322blocked by the insulating film60and ensuring the exhaust rate.

The insulating film60is provided with a plurality of pore structures (not shown) which can communicate spaces on both sides of the insulating film60, so that gas can flow smoothly on both sides of the insulating film60.

The insulating film60may be connected to the insulating part32by means of adhesion, welding and other methods, so as to fix the insulating film60. The insulating film60may be partially connected to the insulating part32(e.g., several points of the insulating film60are welded to the insulating part32), leaving gaps between other areas of the insulating film60and the insulating part32.

For example, a gap is left between the insulating film60and the first protrusion portion323, through which the gas in the first channel322can be discharged. At this time, the second through hole61may be omitted.

FIG.14is a schematic flow chart of the manufacturing method provided in some embodiments of the application.

As shown inFIG.14, the method for manufacturing the battery cell in the embodiments of the application includes:

S100. providing a casing, the casing having an opening and provided with a pressure relief mechanism;

S200. providing an electrode assembly, the electrode assembly comprising a body portion and a tab portion protruding therefrom;

S5300. providing a cover assembly, a first recessed portion being formed on one side of the cover assembly;

S400. connecting the cover assembly to the electrode assembly; and

S500. placing the electrode assembly into the casing, and covering the opening of the cover assembly.

A first recessed portion is formed on one side, abutting against the body portion and facing the electrode assembly, of the cover assembly, and is configured to accommodate at least part of the tab portion; the cover assembly is provided with at least one first channel for communicating the space between the electrode assembly and the casing with the first recessed portion, so as to introduce the gas in the first recessed portion into the space between the electrode assembly and the casing and enable the same to act on the pressure relief mechanism; and the pressure relief mechanism is actuated to relieve an internal pressure or temperature of the battery cell when the internal pressure or temperature reaches a threshold value.

It should be noted that for relevant structures of battery cells manufactured by the method for manufacturing the battery cell, refer to the battery cell provided in the above embodiments.

When assembling battery cells based on the method for manufacturing the battery cell, it is not necessary to follow the above steps sequentially, that is, the steps can be performed in the sequence mentioned in the embodiments, or in a sequence different from that mentioned in the embodiments, or several steps can be performed simultaneously. For example, steps S100, S200, and S300may be performed in no particular order, or at the same time.

FIG.15is a schematic block diagram of a system for manufacturing a battery cell provided in some embodiments of the application.

As shown inFIG.15, the manufacturing system8of the battery cell in one embodiment of the application includes a first supply device81configured to supply a casing which has an opening and is provided with a pressure relief mechanism; a second supply device82configured to supply an electrode assembly which includes a body portion and a tab portion protruding therefrom; a third supply device83configured to supply a cover assembly, with a first recessed portion formed on one side of the cover assembly; a first assembly device84configured to connect the cover assembly to the electrode assembly; and a second assembly device85configured to place the electrode assembly into the casing and cover the opening of the cover assembly. wherein, a first recessed portion is formed on one side, abutting against the body portion and facing the electrode assembly, of the cover assembly, and is configured to accommodate at least part of the tab portion; the cover assembly is provided with at least one first channel for communicating the space between the electrode assembly and the casing with the first recessed portion, so as to introduce the gas in the first recessed portion into the space between the electrode assembly and the casing and enable the same to act on the pressure relief mechanism; and the pressure relief mechanism is actuated to relieve an internal pressure or temperature of the battery cell when the internal pressure or temperature reaches a threshold value.

For relevant structures of battery cells manufactured by the manufacturing system, refer to the battery cell provided in the above embodiments.

It should be noted that the embodiments in the application and features in the embodiments may be combined with one another if there is no conflict.

Finally, it should be noted that the above embodiments are merely used to describe the technical solution of the application, rather than limiting the same. Although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solution described in the foregoing embodiments may still be modified, or some of the technical features therein may be equivalently replaced. However, these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of each embodiment of the application.