Patent Description:
A rechargeable battery, also referred to as a secondary battery, is a battery that can be charged and reused by activating an active material after the battery is discharged. The rechargeable batteries are widely used in electronic devices, for example, mobile phones, laptops, battery cars, electric cars, electric planes, electric ships, electric toy cars, electric toy ships, electric toy planes, electric tools, etc..

In the development of battery technology, apart from improvement to the performance of the battery, the safety is also non-negligible because the battery cannot be used unless the safety is guaranteed. Thus, how to enhance the safety of the battery is a technical problem to be solved urgently in the battery technology.

<CIT> relates to a secondary battery including a case configured to accommodate an electrode assembly, a safety vent on a first side of the case, and a film unit disposed on the first side of the case. The film unit includes a first film unit covering at least a part of the safety vent and including a break unit. The film unit further includes a second film unit extending from the first film unit and being adhered to the case.

<CIT> relates to an electric storage device that includes an electrode assembly, a case, and a sealing member. The case includes a gas exhaust portion that opens to exhaust internal gas when an internal pressure increases. The sealing member is affixed to the case. The sealing member includes a protective portion and at least one of a perforation and a thin section having a thickness smaller than another section of the sealing member. The protective portion covers the gas exhaust portion of the case.

<CIT> relates to a lithium ion secondary battery includes a protective film fixed to a battery case while covering a safety valve part including a breakable portion. This protective film has a first fixed portion located around a valve-corresponding unfixed portion and fixed to the battery case and a second fixed portion located more outside than the first fixed portion and fixed to the battery case through an intermediate unfixed portion.

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

In a first aspect, the embodiment of the application provides a battery cell. The battery cell includes: a battery box including a first wall and a pressure relief mechanism, where the pressure relief mechanism is arranged on the first wall, and the pressure relief mechanism is actuated to relieve internal pressure of the battery cell when the internal pressure or temperature of the battery cell reaches a threshold value; and a protective member positioned on an outer side of the first wall and including a body portion, a shielding portion and a weak portion, where the body portion is configured to be connected to the first wall, the shielding portion is configured to shield the pressure relief mechanism, the weak portion is configured to connect the body portion to the shielding portion, and the weak portion is configured to be broken when the pressure relief mechanism is actuated, so as to disconnect the body portion from the shielding portion.

In this embodiment of the application, the shielding portion of the protective member of the battery cell may block emissions released from other battery cells, so as to reduce possibility of melt-through of the pressure relief mechanism by the emissions released from other battery cells and reduce the safety risk. On the other hand, when thermal runaway occurs in the battery cell, the pressure relief mechanism is actuated to release a high-temperature and high-pressure substance from the battery cell, and meanwhile, the weak portion is broken under the action of the high-temperature and high-pressure substance, such that a channel for discharging the high-temperature and high-pressure substance is formed on the protective member, and the high-temperature and high-pressure substance is discharged in time, so as to reduce the safety risk.

In some embodiments, the battery cell further includes a bonding member, and the protective member is connected to the first wall by means of the bonding member.

In some embodiments, a surface, facing the first wall, of the body portion is provided with the bonding member, and a surface, facing the first wall, of the shielding portion and a surface, facing the first wall, of the weak portion are provided with no bonding member, so as to reduce the risk that the bonding member connects the shielding portion to the body portion when the weak portion is broken.

In some embodiments, a melting point of the protective member is greater than that of the pressure relief mechanism. The protective member with a higher melting point may bear higher temperature, so as to reduce the risk of melt-through by the emissions and improve safety performance.

In some embodiments, the melting point of the protective member is not less than <NUM> degrees Celsius.

In some embodiments, the protective member is made from materials that include at least one of mica, rubber and ceramic.

In some embodiments, a thickness of the shielding portion is less than that of the body portion.

In some embodiments, the pressure relief mechanism is provided with a first groove, the pressure relief mechanism is configured to be broken at the first groove to relieve the internal pressure of the battery cell when the internal pressure or temperature reaches the threshold value, and the shielding portion completely covers the first groove.

The shielding portion protrudes outward from the body portion in a direction perpendicular to the first wall. In this way, a distance between the shielding portion and the pressure relief mechanism may be increased in the direction perpendicular to the first wall, so as to prolong a heat transfer path between the shielding portion and the pressure relief mechanism and reduce heat transferred to the pressure relief mechanism.

An outer surface of the first wall is provided with a protrusion, and the shielding portion is positioned on one side, away from the pressure relief mechanism, of the protrusion in the direction perpendicular to the first wall.

The battery cell further includes a protective film arranged on a surface, facing the shielding portion, of the protrusion and covering the pressure relief mechanism. The protective film may block external dust, water vapor and other impurities to protect the pressure relief mechanism.

In some embodiments, the shielding portion compresses the protective film. The shielding portion and the protrusion clamp the protective film to reduce the risk of falling-off of the protective film.

A plurality of through open holes are provided between the body portion and the shielding portion, the weak portion includes a plurality of weak subareas, and the plurality of weak subareas and the plurality of open holes are alternately provided on the periphery of the shielding portion. The protective member is provided with the open hole, such that overall strength of the weak portion may be reduced, and when the shielding portion is impacted by the high-temperature and high-pressure substance, the weak subarea of the weak portion may be broken in time.

In some embodiments, a thickness of the weak subarea is less than or equal to that of the body portion; and/or the thickness of the weak subarea is less than or equal to that of the shielding portion.

In some embodiments, a second groove is provided in a surface of one side, away from the first wall, of the protective member, and the weak portion is a bottom wall of the second groove; and/or a second groove is provided in a surface of one side, close to the first wall, of the protective member, and the weak portion is a bottom wall of the second groove. By arranging the second groove, the strength of the weak portion may be reduced, and the weak portion may be timely broken when being impacted by the high-temperature and high-pressure substance.

In some embodiments, the second groove is an annular groove surrounding the shielding portion. Correspondingly, the weak portion is annular and is arranged around an edge of the shielding portion. When the shielding portion is impacted by the high-temperature and high-pressure substance, all parts of the weak portion may be broken, so as to increase a discharge rate of the high-temperature and high-pressure substance.

In some embodiments, a thickness of the weak portion is <NUM> to <NUM>.

In some embodiments, the battery box includes: a casing provided with an accommodation cavity and an opening; and an end cover assembly including a cover plate and an electrode terminal, where the cover plate covers the opening of the casing, the electrode terminal is arranged on the cover plate, and the first wall is the cover plate.

In some embodiments, the battery cell further includes an electrode assembly accommodated in the accommodation cavity.

In a second aspect, the embodiment of the application provides a battery including a box and at least one battery cell of the first aspect, the battery cell being received in the box.

In a third aspect, the embodiment of the application provides an electric device configured to receive electrical energy provided by the battery of the second aspect.

In order to describe the technical solutions in the embodiments of the application more clearly, the accompanying drawings required for describing the embodiments are briefly described below. Obviously, the accompanying drawings in the following description show merely some embodiments of the present disclosure, and a person of ordinary skill in the art would also be able to derive other accompanying drawings from these accompanying drawings without creative efforts.

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

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.

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.

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.

As used herein, "plurality" refers to two or more, and similarly, "plurality of sets" refers to two or more sets, and "plurality of pieces" refers to two or more pieces.

In the application, battery cells may include a lithium-ion secondary battery, a lithium-ion primary battery, a lithium-sulfur battery, a sodium lithium-ion battery, a sodium ion battery or a magnesium ion battery, etc., which is 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 is 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, where the electrode assembly is composed of a positive pole piece, a negative pole piece and a separator film. 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, the positive active material layer coating a surface of the positive current collector, a current collector not coated with the positive active material layer protrudes out of the current collector coated with the positive active material layer, and the current collector not coated with the positive active material layer serves as a positive tab. With a lithium-ion battery as an example, a positive current collector may be made from aluminum, and the positive active material may be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganate, etc. The negative pole piece includes a negative current collector and a negative active material layer, the negative active material layer coating a surface of the negative current collector, a current collector not coated with the negative active material layer protrudes out of the current collector coated with the negative active material layer, and the current collector not coated with the negative active material layer serves as a negative tab. The negative current collector may be made from copper, and the negative active material may be carbon, silicon, etc. 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 film may be made from PP, PE, etc. 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. For development of battery technology, various design factors should be considered simultaneously, such as energy density, cycle life, discharge capacity, charge-discharge rates and other performance parameters. In addition, safety of the battery needs to be further considered.

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 a switch element, selection of an appropriate separator film, and a pressure relief mechanism. 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 film is used for isolating the positive pole piece from the negative pole piece and may automatically dissolve micron-scale (even nano-scale) micropores attached to the separator film when the temperature rises to a certain value, such that metal ions may not pass through the separator film, and then reaction in the battery cell stops.

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 a positive pole piece, a negative pole piece, an electrolyte solution and a separator film in the battery cell. The pressure relief mechanism may be, for example, an explosion-proof valve, an air valve, a pressure relief valve, a safety valve, etc., and may specifically use a pressure-sensitive or temperature-sensitive element or structure. That is, when the internal pressure or temperature of the battery cell reaches a preset threshold value, the pressure relief mechanism executes action or a weak structure arranged in the pressure relief mechanism is broken, such that an opening or a channel through which internal pressure or temperature may be relieved is formed.

"Actuation" as referred to herein means that the pressure relief mechanism produces action or is activated to a state, so as to relieve the internal pressure and temperature of the battery cell. 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 may be relieved under the condition that the pressure or the temperature is controllable, and therefore more-serious potential accidents are avoided.

The emissions from the battery cell in this application include, but are not limited to, the electrolyte solutions, the dissolved or split positive and negative pole pieces, fragments of the separator film, high-temperature and high-pressure gas produced by reactions, flames, etc..

The pressure relief mechanism on the battery cell has important influence on the safety of the battery. For example, when a short circuit, overcharge, etc. occur, thermal runaway inside the battery cell may result in a sudden rise in pressure or temperature. Under the condition, the internal pressure and temperature may be released outwards by means of actuation of the pressure relief mechanism, such that the battery cell is protected from explosion and fire.

In an existing pressure relief mechanism design scheme, high pressure and high heat in the battery cell are released mainly, that is, the emissions are discharged to an outside of the battery cell. However, in order to ensure output voltage or current of the battery, the plurality of battery cells are often required to be electrically connected by means of a bus component. The emissions discharged from the interior of the battery cell may cause a short circuit of other battery cells. For example, the emissions are diffused to other normal battery cells all around, and under the action of high temperature, the emissions easily melt through a pressure relief mechanism of a normal battery cell and enter an electrode assembly, resulting in a short circuit and thermal runaway of the original normal battery cell, and further aggravating the safety problem.

In view of this, the embodiment of the application provides a technical solution. A protective member is arranged on the pressure relief mechanism of the battery cell to protect the pressure relief mechanism, prevent melt-through of the pressure relief mechanism, reduce short circuit risk, and improve the safety of the battery.

The technical solutions described in the embodiments of the application are applicable to various devices using batteries, such as mobile phones, portable devices, notebook computers, electromobiles, electric toys, electric tools, electric vehicles, ships and spacecrafts, for example, the spacecrafts include airplanes, rockets, space shuttles, spaceships, etc..

It should be understood that the technical solutions described in the embodiments of the application are not only applicable to the devices described above, but also applicable to all devices using batteries. However, for simplicity of description, the following embodiments will be described by taking an electric vehicle as an example.

For example, <FIG> is a structural schematic diagram of a vehicle <NUM> in one embodiment of the application. The vehicle <NUM> may be a fuel, gas or new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle, an extended range vehicle, etc. The vehicle <NUM> may be further internally provided with a battery <NUM>, a controller <NUM> and a motor <NUM>, where the controller <NUM> is used for controlling the battery <NUM> to energize the motor <NUM>. For example, the battery <NUM> may be arranged at a bottom, head or tail of the vehicle <NUM>. The battery <NUM> may be used for energizing the vehicle <NUM>, for example, the battery <NUM> may be used as an operating power source for the vehicle <NUM>, for circuitry of the vehicle <NUM>, for example, for operating power requirements during start-up, navigation and operation of the vehicle <NUM>. In another embodiment of the application, the battery <NUM> may not only be used as an operating power source for the vehicle <NUM>, but serve as a driving power source for the vehicle <NUM>, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle <NUM>.

For meeting different power use requirements, the battery may include a plurality of battery cells, wherein the plurality of battery cells may be connected in series, parallel or any combination, wherein a combination refers to a mixture of series connection and parallel connection. The battery may also refer to a battery pack. Optionally, the plurality of battery cells may be connected in series, in parallel or in a series-parallel mode to form a battery module, and then the plurality of battery modules may be connected in series, in parallel or in a series-parallel mode to form a battery. That is, the plurality of battery cells may form the battery directly, or may form the battery module first, and then the battery module forms the battery.

For example, <FIG> is a structural schematic diagram of a battery <NUM> in one embodiment of the application. The battery <NUM> may include a plurality of battery cells <NUM>. The battery <NUM> may further include a box (or called a cover), the interior of the box is of a hollow structure, and the plurality of battery cells <NUM> are accommodated in the box. As shown in <FIG>, the box may include two parts, referred to herein as a first part <NUM> and a second part <NUM> separately, which are buckled together. A shape of the first part <NUM> and the second part <NUM> may be determined according to a shape of combination of the plurality of battery cells <NUM>, and each of the first part <NUM> and the second part <NUM> may have one opening. For example, each of the first part <NUM> and the second part <NUM> may be a hollow cuboid with only one open face, the opening of the first part <NUM> and the opening of the second part <NUM> are oppositely arranged, and the first part <NUM> and the second part <NUM> are buckled to each other to form a box with a closed cavity. The plurality of battery cells <NUM> are connected to each other in parallel or in series or in a series-parallel mode and then arranged in the box formed by buckling the first part <NUM> and the second part <NUM>.

Optionally, the battery <NUM> may also include other structures, which are not repeated here. For example, the battery <NUM> may further include a bus component, and the plurality of battery cells <NUM> may be electrically connected to each other by means of the bus component, for example, in parallel or in series or in a series-parallel mode. Specifically, the bus component may connect electrode terminals of the battery cells <NUM> to achieve electrical connection between the battery cells <NUM>. Further, the bus component may be welded to the electrode terminal of the battery cell <NUM>. Electric energy of the plurality of battery cells <NUM> may be further led out through the box by means of an electric conduction mechanism. Optionally, the electric conduction mechanism may also belong to the bus component.

The number of battery cells <NUM> may be set to any number according to different power requirements. The plurality of battery cells <NUM> may be connected in series, in parallel, or in a series-parallel mode to achieve higher capacity or power. Since the number of battery cells <NUM> included in each battery <NUM> may be large, for ease of mounting, the battery cells <NUM> may be arranged in groups, each group of battery cells <NUM> constituting a battery module. The number of battery cells <NUM> included in the battery module is not limited and may be set as required. For example, <FIG> is an example of a battery module. The battery may include a plurality of battery modules, which may be connected in series, in parallel, or in a series-parallel mode.

<FIG> is a structural schematic diagram of a battery cell <NUM> in one embodiment of the application; <FIG> is a schematic exploded view of the battery cell <NUM> shown in <FIG>; and <FIG> is a schematic sectional view of the battery cell <NUM> shown in <FIG> along line A-A. <FIG> is an enlarged view of the battery cell <NUM> shown in <FIG> at box B.

As shown in <FIG>, the battery cell <NUM> includes an electrode assembly <NUM> and a battery box for accommodating the electrode assembly <NUM>, the battery box including an end cover assembly <NUM> and a casing <NUM>. The casing <NUM> is provided with an accommodation cavity and an opening, and the electrode assembly <NUM> is accommodated in the accommodation cavity. For example, when the casing <NUM> is a hollow cuboid or cube, one of planes of the casing <NUM> is an open surface, that is, the plane is provided with no wall, so as to communicate the interior to exterior of the casing <NUM>. When the casing <NUM> may be a hollow cylinder, an end face of the casing <NUM> is an open surface, that is, the end face is provided with no wall, so as to communicate the interior to the exterior of the casing <NUM>. The end cover assembly <NUM> includes a cover plate <NUM>, the cover plate <NUM> covering the opening and being connected to the casing <NUM>, thereby closing the opening of the casing <NUM> to place the electrode assembly <NUM> in the closed cavity. The casing <NUM> is filled with an electrolyte, for example, an electrolyte solution.

The end cover assembly <NUM> may also include two electrode terminals, which may be arranged on the cover plate <NUM>. The cover plate <NUM> is generally of a flat-plate shape, two electrode terminals are fixed to a flat-plate surface of the cover plate <NUM>, the two electrode terminals are a positive electrode terminal <NUM> and a negative electrode terminal <NUM>. Each electrode terminal is correspondingly provided with a connection member <NUM>, which may also be referred to as a current collecting member, located between the cover plate <NUM> and the electrode assembly <NUM> for electrically connecting the electrode assembly <NUM> and the electrode terminal.

Each electrode assembly <NUM> is provided with a first tab 101a and a second tab 101b. Polarities of the first tab 101a and the second tab 101b are opposite. For example, when the first tab 101a is a positive tab, the second tab 101b is a negative tab. The first tab 101a of one or more electrode assemblies <NUM> is connected to one electrode terminal by means of one connection member <NUM>, and the second tab 101b of the one or more electrode assemblies <NUM> is connected to the other electrode terminal by means of the other connection member <NUM>. For example, the positive electrode terminal <NUM> is connected to the positive tab by means of one connection member <NUM>, and the negative electrode terminal <NUM> is connected to the negative tab by means of the other connection member <NUM>.

In the battery cell <NUM>, one or more electrode assemblies <NUM> may be provided according to actual use requirements. In some examples, two separate electrode assemblies <NUM> are provided in the battery cell <NUM>.

In some embodiments, the end cover assembly <NUM> may further include a lower insulator <NUM>, where the lower insulator <NUM> is arranged on one side, facing the electrode assembly <NUM>, of the cover plate <NUM>, and the lower insulator <NUM> may separate the cover plate <NUM> from the connection member <NUM> and separate the cover plate <NUM> from the electrode assembly <NUM>, so as to reduce risk of short circuits.

The battery box includes a first wall and a pressure relief mechanism <NUM> arranged on the first wall. In some examples, the first wall may be one wall of the casing <NUM>, for example, the casing <NUM> includes four side walls and a bottom wall connected to the four side walls, and the first wall may be either the bottom wall or one side wall. In other examples, the first wall is the cover plate <NUM>. The pressure relief mechanism <NUM> may be part of the first wall or may be separate from the first wall, for example, welded to the first wall.

The cover plate <NUM> of the embodiment of the application is provided with a through hole <NUM>, and the through hole <NUM> penetrates the cover plate <NUM> in a thickness direction of the cover plate <NUM>. The pressure relief mechanism <NUM> is connected to the cover plate <NUM> and covers the through hole <NUM>. In the battery cell <NUM>, the pressure relief mechanism <NUM> may seal the through hole <NUM> to separate the spaces of an inner side and an outer side of the cover plate <NUM>, such that the electrolyte solution is prevented from flowing out of the through hole <NUM>, so as to improve sealing performance of the battery cell <NUM>.

The pressure relief mechanism <NUM> is configured to be actuated to relieve internal pressure of the battery cell <NUM> when the internal pressure or temperature reaches a preset threshold value. When internal pressure of the casing <NUM> rises and reaches a threshold value due to too much gas generated by the battery cell <NUM> or the internal temperature of the battery cell <NUM> rises and reaches a threshold value due to heat generated by internal reaction of the battery cell <NUM>, the pressure relief mechanism <NUM> executes action or a weak structure arranged in the pressure relief mechanism <NUM> is broken, and then gas pressure and temperature are released outwards by means of an opening cracked in the pressure relief mechanism <NUM> and the through hole <NUM>, so as to prevent the battery cell <NUM> from exploding.

The pressure relief mechanism <NUM> may be of a variety of possible pressure relief structures, which is not limited by the embodiments of the application. For example, the pressure relief mechanism <NUM> may be a temperature-sensitive pressure relief mechanism configured to melt when the internal temperature of the battery cell <NUM> provided with the pressure relief mechanism <NUM> reaches the threshold value; and/or, the pressure relief mechanism <NUM> may be a pressure-sensitive pressure relief mechanism configured to be broken when the internal gas pressure of the battery cell <NUM> provided with the pressure relief mechanism <NUM> reaches the threshold value.

The battery cell of the embodiment of the application further includes a protective member <NUM>. The protective member <NUM> is arranged on the outer side of the cover plate <NUM>, that is, the protective member <NUM> is arranged on one side, away from the electrode assembly <NUM>, of the cover plate <NUM>. The protective member <NUM> is configured to shield the pressure relief mechanism <NUM> and the through hole <NUM> from the outside. The protective member <NUM> may completely shield the through hole <NUM> or shield only part of the through hole <NUM>.

In the battery, when the pressure relief mechanism of a certain battery cell is actuated and releases the emissions, the emissions are diffused to other normal battery cells all around, the protective member <NUM> on the normal battery cell may block the emissions, accordingly, the risk that the emissions make contact with the pressure relief mechanism <NUM> and melt through the pressure relief mechanism <NUM> is reduced, and the emissions are reduced or prevented from entering the electrode assembly <NUM>, so as to reduce the safety risk.

The inventors have further discovered that although the protective member <NUM> of the battery cell <NUM> may shield the pressure relief mechanism <NUM> from the outside to reduce the risk of melt-through of the pressure relief mechanism <NUM> by the emissions released from other battery cells, the protective member <NUM> is difficult to open quickly when the battery cell <NUM> needs to release the high-temperature and high-pressure substance therein due to thermal runaway, accordingly, the high-temperature and high-pressure substance may not be discharged in time, causing the safety risk.

In view of this, the protective member <NUM> provided in an embodiment of the application includes a body portion <NUM>, a shielding portion <NUM>, and a weak portion <NUM>. The body portion <NUM> is configured to be connected to the cover plate <NUM> to fix the protective member <NUM> to the cover plate <NUM>. The shielding portion <NUM> is configured to shield the pressure relief mechanism <NUM> to block the emissions released from other battery cells, so as to reduce the risk of melt-through of the pressure relief mechanism <NUM> by the emissions released from the other battery cells. The weak portion <NUM> is configured to connect the body portion <NUM> to the shielding portion <NUM>, and the weak portion <NUM> is configured to be broken when the pressure relief mechanism <NUM> is actuated, so as to disconnect the body portion <NUM> from the shielding portion <NUM>.

The shielding portion <NUM> is configured to shield a portion, corresponding to the through hole <NUM>, of the pressure relief mechanism <NUM>. The shielding portion <NUM> may completely shield the through hole <NUM> or shield only part of the through hole <NUM>. In the thickness direction of the cover plate <NUM>, an orthogonal projection of the shielding portion <NUM> and an orthogonal projection of the through hole <NUM> at least partially overlap. The orthogonal projection of the through hole <NUM> refers to a region enclosed by the orthogonal projection of a hole wall of the through hole <NUM> in the thickness direction.

The weak portion <NUM> may be configured to be conveniently broken by the high-temperature and high-pressure substance, which is not limited in the embodiment of the application. The strength of the weak portion <NUM> is less than that of the shield portion <NUM> and that of the body portion <NUM>, such that the weak portion <NUM> may be broken when the pressure relief mechanism <NUM> is actuated, so as to disconnect the body portion <NUM> from the shielding portion <NUM>. The protective member <NUM> may reduce the strength of the weak portion <NUM> by providing a structure, for example, an opening, a groove, a score, etc. Certainly, the weak portion <NUM> may be made from a low-strength material.

When the pressure relief mechanism <NUM> is actuated, the weak portion <NUM> is broken under the action of the high-temperature and high-pressure substance, so as to disconnect the body portion <NUM> from the shielding portion <NUM>. The high-temperature and high-pressure substance may act directly on the weak portion <NUM>, or may transfer heat and pressure to the weak portion <NUM> by means of the shielding portion <NUM>. In some examples, the weak portion <NUM> may be broken entirely, and the shielding portion <NUM> is not restrained by the body portion <NUM> and is flushed away by the high-temperature and high-pressure substance, such that the shielding portion <NUM> does not block the high-temperature and high-pressure substance any more, and a channel for discharging the high-temperature and high-pressure substance is formed in the protective member <NUM>, so as to quickly discharge the high-temperature and high-pressure substance out of the battery cell <NUM>. In other examples, the weak portion <NUM> may be broken partially, and the protective member <NUM> may form a channel at a broken position of the weak portion <NUM>, and the high-temperature and high-pressure substance may be discharged by means of the channel. In addition, a connection force between the shielding portion <NUM> and the body portion <NUM> is reduced, and the shielding portion <NUM> is turned outwards under the impact of the high-temperature and high-pressure substance, such that a size of the channel is increased, and discharging efficiency of the high-temperature and high-pressure substance is increased.

On one hand, the shielding portion <NUM> of the protective member <NUM> of the battery cell <NUM> may block emissions released from other battery cells, so as to reduce the risk of melt-through of the pressure relief mechanism <NUM> by the emissions released from other battery cells. On the other hand, when thermal runaway occurs in the battery cell <NUM>, the pressure relief mechanism <NUM> is actuated to release a high-temperature and high-pressure substance in the battery cell, and meanwhile, the weak portion <NUM> is broken under the action of the high-temperature and high-pressure substance, such that a channel for discharging the high-temperature and high-pressure substance is formed on the protective member <NUM>, and the high-temperature and high-pressure substance is discharged in time, so as to reduce the safety risk.

In some embodiments of the application, a melting point of the protective member <NUM> is greater than that of the pressure relief mechanism <NUM>. Compared with the pressure relief mechanism <NUM>, the protective member <NUM> with a higher melting point may bear higher temperature, so as to reduce the risk of melt-through by the emissions and improve safety performance.

In one embodiment of the application, the melting point of the protective member <NUM> is not less than <NUM> degrees Celsius. In this way, the protective member <NUM> with the higher melting point is less likely to be melted through by the emissions. Optionally, the melting point of the protective member <NUM> is not less than <NUM> degrees Celsius.

In some embodiments of the application, the protective member <NUM> is made from materials that include at least one of mica, rubber and ceramic. Optionally, the protective member <NUM> is mica paper or a mica plate, which has insulating, high temperature resistant properties, and may effectively block the high-temperature emissions to protect the pressure relief mechanism <NUM>. The mica paper or the mica plate is thin and may be timely broken at the weak portion <NUM> when being impacted by the high-temperature and high-pressure substance; and moreover, the mica paper or the mica plate with a smaller thickness and lower weight has small influence on energy density of the battery cell.

In some embodiments of the application, the protective member <NUM> may also insulate heat. The protective member <NUM> may separate at least part of the emissions from the cover plate <NUM>, thereby reducing the heat transferred to the cover plate <NUM>, reducing a temperature rise of the battery cell <NUM>, making the electrode assembly <NUM> operate in a suitable temperature range, and improving charge and discharge performance of the electrode assembly <NUM>.

In some embodiments of the application, the shielding portion <NUM> completely covers the through hole <NUM> in the thickness direction of the cover plate <NUM>, such that the shielding portion <NUM> may block the emissions as much as possible, so as to reduce the risk that the emissions enter the through hole <NUM>.

The battery cell of the embodiment of the application further includes a bonding member <NUM>, and the protective member <NUM> is connected to the cover plate <NUM> by means of the bonding member <NUM>. The bonding member <NUM> may be gum. Before being fitted to the cover plate <NUM>, the protective member <NUM> may be bonded to release paper by means of the bonding member <NUM>; and when necessary, the protective member <NUM> and the bonding member <NUM> are striped from the release paper and then bonded to the cover plate <NUM>.

In some embodiments, a surface, facing the cover plate <NUM>, of the body portion <NUM> is provided with the bonding member <NUM>. The bonding member <NUM> fixes the body portion <NUM> to the cover plate <NUM>. The bonding member <NUM> has adhesiveness, becomes soft at a high temperature and is not easily broken, and under the condition that the bonding member <NUM> is also provided on the shielding portion <NUM> and the weak portion <NUM>, when the weak portion <NUM> is broken, the bonding member <NUM> may connect the shielding portion <NUM> to the body portion <NUM>, resulting in that the high-temperature and high-pressure substance may not be timely discharged, and thus, neither a surface, facing the cover plate <NUM>, of the shielding portion <NUM> nor a surface, facing the cover plate <NUM>, of the weak portion <NUM> is provided with the bonding member <NUM>.

In some embodiments, one bonding member <NUM> may be provided. In other embodiments, a plurality of bonding members <NUM> may be arranged discontinuously.

<FIG> is an enlarged view of <FIG> at box C. As shown in <FIG>, in some embodiments of the application, the pressure relief mechanism <NUM> is provided with a first groove <NUM>, the pressure relief mechanism <NUM> is configured to be broken at the first groove <NUM> to relieve the internal pressure of the battery cell when the internal pressure or temperature reaches a threshold value. A bottom wall of the first groove <NUM> is of a weak structure formed on the pressure relief mechanism <NUM>, when the internal pressure or temperature of the battery cell reaches the threshold value, the bottom wall of the first groove <NUM> is cracked to form an opening, and the gas pressure and temperature are released outwards by means of the opening cracked in the pressure relief mechanism <NUM> and the through hole <NUM>, so as to prevent the battery cell from exploding.

The bottom wall of the first groove <NUM> is weaker and is more easily melted through by the emissions. Thus, in some embodiments, the shielding portion <NUM> completely covers the first groove <NUM>, that is, the orthogonal projection of the shielding portion <NUM> completely covers the orthogonal projection of the first groove <NUM> in the thickness direction of the cover plate <NUM>, so as to reduce the risk that the emissions fall into the first groove <NUM> of the pressure relief mechanism <NUM>, further to reduce the possibility of melt-through of the pressure relief mechanism <NUM>.

The shielding portion <NUM> protrudes outward from the body portion <NUM> in a direction perpendicular to the cover plate <NUM>. In this way, a distance between the shielding portion <NUM> and the pressure relief mechanism <NUM> may be increased in the direction perpendicular to the cover plate <NUM> (that is, the thickness direction of the cover plate <NUM>), so as to prolong a heat transfer path between the shielding portion <NUM> and the pressure relief mechanism <NUM> and reduce heat transferred to the pressure relief mechanism <NUM>. Additionally, in some examples, when the internal pressure or temperature of the battery cell reaches the threshold value, the pressure relief mechanism <NUM> may be broken at the bottom wall of the first groove <NUM>, and a portion, arranged along the broken position, of the pressure relief mechanism <NUM> folds upward to form an opening to release the high-temperature and high-pressure substance. If the distance between the shielding portion <NUM> and the pressure relief mechanism <NUM> is too small, the shielding portion <NUM> may block folding of the pressure relief mechanism <NUM>, resulting in a small opening of the pressure relief mechanism <NUM>, and the shielding portion <NUM> may not be flushed away by the high-temperature and high-pressure substance in time. Therefore, the shielding portion <NUM> protrudes out of the body portion <NUM>, so as to increase the distance between the shielding portion <NUM> and the pressure relief mechanism <NUM>, and accordingly, the shielding portion <NUM> is prevented from blocking folding of the pressure relief mechanism <NUM>.

In some embodiments of the application, the weak portion <NUM> extends from an edge of the shielding portion <NUM> toward the cover plate <NUM> and is connected to the body portion <NUM>. The protective member <NUM> is provided with a recessed portion on one side, facing the cover plate <NUM>, of the shielding portion <NUM>. Each of the body portion <NUM> and the shielding portion <NUM> is of a flat-plate shape and is substantially perpendicular to the thickness direction of the cover plate <NUM>. The weak portion <NUM> is bent at a preset angle relative to the shielding portion <NUM>. As shown in <FIG>, the weak portion <NUM> is substantially perpendicular to the shielding portion <NUM>. Certainly, an included angle between the weak portion <NUM> and the shielding portion <NUM> may be set according to product requirements, for example, may be <NUM> degrees to <NUM> degrees, and specifically, may be <NUM> degrees, <NUM> degrees, <NUM> degrees, etc., which is not limited herein.

In some embodiments of the application, the cover plate <NUM> is also provided with a reception groove <NUM> recessed from a surface, facing the electrode assembly <NUM>, of the cover plate <NUM>, and the reception groove <NUM> is arranged around the through hole <NUM>. The pressure relief mechanism <NUM> is at least partially accommodated in the reception groove <NUM>. The reception groove <NUM> may serve a positioning function to facilitate fitting of the pressure relief mechanism <NUM> and the cover plate <NUM>.

In some embodiments of the application, the cover plate <NUM> includes a cover plate body <NUM> and a protrusion <NUM> connected to the cover plate body <NUM>. The shielding portion <NUM> is positioned on one side, away from the pressure relief mechanism <NUM>, of the protrusion <NUM> in the direction perpendicular to the cover plate <NUM>. In some examples, the protrusion <NUM> is positioned between the shielding portion <NUM> and the cover plate body <NUM>, and "between" refers to a spatial positional relationship of the protrusion <NUM>, the shielding portion <NUM>, and the cover plate body <NUM> in the thickness direction of the cover plate <NUM>, and does not require the shielding portion <NUM> and the protrusion <NUM> to overlap in the thickness direction. The cover plate body <NUM> is of a flat-plate shape substantially. The protrusion <NUM> protrudes out relative to a surface, facing the protective member <NUM>, of the cover plate body <NUM>. The through hole <NUM> penetrate the cover plate body <NUM> and the protrusion <NUM>. The through hole <NUM> includes an inner section penetrating the cover plate body <NUM> and an outer section penetrating the protrusion <NUM>, and the protrusion <NUM> includes a sidewall surrounding the outer section. The protrusion <NUM> extends into the recessed portion of the protective member <NUM>.

In some embodiments of the application, in a direction parallel to the cover plate body <NUM>, the weak portion <NUM> is positioned on one side, away from the through hole <NUM>, of the protrusion <NUM>, and the protrusion <NUM> may separate the weak portion <NUM> from the through hole <NUM>, and even if a portion of the weak portion <NUM> is melted through by the emissions, the protrusion <NUM> may block the emissions, so as to reduce or prevent the emissions from entering the through hole <NUM>.

The protrusion <NUM> may also strengthen strength of the cover plate <NUM> at the through hole <NUM>, and reduce deformation of the cover plate <NUM>. In some examples, the reception groove <NUM> may be formed by pressing the cover plate <NUM>, and after the cover plate <NUM> is pressed, the protrusion <NUM> is formed on the cover plate <NUM>.

In some embodiments of the application, the battery cell <NUM> further includes a protective film <NUM> arranged between the shielding portion <NUM> and the pressure relief mechanism <NUM> and covering the through hole <NUM> and the pressure relief mechanism <NUM>. In some examples, the protective film <NUM> is arranged on a surface, facing the shielding portion <NUM>, of the protrusion <NUM> and covers the through hole <NUM> and the pressure relief mechanism <NUM>. The protective film <NUM> may seal the through hole <NUM> to reduce impurities, for example, external dust and water vapor entering the through hole <NUM>. The protective film <NUM> is of a film structure, has low strength, is easily broken under impact of the high-temperature and high-pressure substance, and does not influence discharge of the high-temperature and high-pressure substance. Optionally, the protective film <NUM> is a transparent polyethylene terephthalate (PET) patch.

In some embodiments of the application, the shielding portion <NUM> compresses the protective film <NUM>. The shielding portion <NUM> and the protrusion <NUM> clamp the protective film <NUM>, thereby reducing the risk of falling off of the protective film <NUM>.

<FIG> is a schematic structural diagram of a protective member <NUM> in one embodiment of the application and illustrates a shape of the protective member <NUM> prior to fitting to the cover plate <NUM>. <FIG> is a schematic structural diagram of another protective member <NUM> in one embodiment of the application and illustrates a shape of the protective member <NUM> prior to fitting to the cover plate <NUM>.

With reference to <FIG>, in some embodiments, the protective member <NUM> is directly provided with the shielding portion <NUM> protruding out of the body portion <NUM> during manufacturing of the protective member <NUM>. The body portion <NUM> and the shielding portion <NUM> are each of a flat-plate shape substantially and are arranged parallel to each other, and the weak portion <NUM> is substantially perpendicular to the body portion <NUM> and the shielding portion <NUM>. The protective member <NUM> forms a recessed portion inside the shielding portion <NUM>. When the protective member <NUM> and the cover plate <NUM> are fitted, the body portion <NUM> is connected to the cover plate body <NUM>, and the recessed portion of the protective member <NUM> reserves an accommodating space for the protrusion <NUM> of the cover plate <NUM>.

With reference to <FIG>, in other embodiments, the protective member <NUM> may be manufactured into a flat-plate shape in advance. In this way, the body portion <NUM>, the shielding portion <NUM>, and the weak portion <NUM> are substantially in one plane. A forming process of the flat-plate-shaped protective member <NUM> is simple. When the protective member <NUM> and the cover plate <NUM> are fitted, the shielding portion <NUM> is attached to the protrusion <NUM> or the protective film <NUM>, and then the body portion <NUM> is pressed; and the strength of the weak portion <NUM> is smaller, and when the body portion <NUM> is pressed, the weak portion <NUM> may deform, thereby making the body portion <NUM> close to the cover plate <NUM>, so as to connect the body portion <NUM> to the cover plate body <NUM>. After the flat-plate-shaped protective member <NUM> is fitted to the cover plate <NUM>, the protrusion <NUM> may support the shielding portion <NUM>, such that the shielding portion <NUM> protrudes out of the body portion <NUM>.

The weak portion <NUM> may be formed in different ways as desired, as long as the strength of the weakened portion <NUM> may be reduced and the weak portion <NUM> may be broken when the pressure relief mechanism <NUM> is actuated.

<FIG> is an enlarged view of the protective member <NUM> shown in <FIG> at circle frame D. As shown in <FIG>, in some embodiments of the application, a plurality of through open holes <NUM> are provided between the body portion <NUM> and the shielding portion <NUM>, the weak portion <NUM> includes a plurality of weak subareas 153a, and the plurality of weak subareas 153a and the plurality of open holes <NUM> are alternately provided on the periphery of the shielding portion <NUM>. The protective member <NUM> is provided with the open hole <NUM>, such that overall strength of the weak portion <NUM> may be reduced. When the shielding portion <NUM> is impacted by the high-temperature and high-pressure substance, the weak subarea 153a of the weak portion <NUM> may be broken in time. In some examples, when thermal runaway occurs in the battery cell <NUM>, all of the weak subareas 153a are broken under the impact of the high-temperature and high-pressure substance, and the shielding portion <NUM> is not restrained by the body portion <NUM> any more and flushed away by the high-temperature and high-pressure substance. In other examples, it is possible that some of the weak subareas 153a are broken under impact of the high-temperature and high-pressure substance, and the other weak subareas 153a are still connected to the shielding portion <NUM> and the body portion <NUM>. In such a condition, the binding force of the body portion <NUM> to the shielding portion <NUM> is small, and the shielding portion <NUM> may deform under the impact of the high-temperature and high-pressure substance and may also turn outwards with the undamaged weak subarea 153a as an axis, such that a channel may be formed between the body portion <NUM> and the shielding portion <NUM> for rapidly discharging the high-temperature and high-pressure substance. When thermal runaway occurs in the battery cell <NUM>, the number of the broken weak subareas 153a depends on the capacity of the battery cell <NUM>, whether all weak subareas 153a are broken or some weak subareas 153a are broken, as long as the temperature and pressure inside the battery cell <NUM> may be relieved to within a safe range within a certain time.

In some embodiments, four weak subareas 153a are provided, two weak subareas 153a are oppositely arranged in a length direction of the protective member <NUM>, and the other two weak subareas 153a are oppositely arranged in a width direction of the protective member <NUM>.

In some embodiments, in a circumferential direction of the shielding portion <NUM>, a ratio of a size of a connection of the weak portion <NUM> with the shielding portion <NUM> to a circumference of the shielding portion <NUM> is less than <NUM>%; and when the shielding portion <NUM> is impacted by the high-temperature and high-pressure substance, the connection of the weak portion <NUM> and the shielding portion <NUM> is more likely to be broken.

In some embodiments, the thickness of the weak subarea 153a is less than or equal to that of the body portion <NUM>. When the thickness of the weak subarea 153a is less than that of the body portion <NUM>, the strength of a connection of the weak subarea 153a and the body portion <NUM> is lower, and when the high-temperature and high-pressure substance impacts the protective member <NUM>, the connection of the weak subarea 153a and the body portion <NUM> is more likely to be broken.

In some embodiments, the thickness of the weak subarea 153a is less than or equal to that of the shielding portion <NUM>. When the thickness of the weak subarea 153a is less than that of the shielding portion <NUM>, the strength of a connection of the weak subarea 153a and the shielding portion <NUM> is lower, and when the high-temperature and high-pressure substance impacts the protective member <NUM>, the connection of the weak subarea 153a and the shielding portion <NUM> is more likely to be broken.

In some embodiments, the thickness of the weak subarea 153a is less than that of the body portion <NUM> and also less than that of the shielding portion <NUM>.

In some examples, the thickness of the body portion <NUM> is equal to that of the shielding portion <NUM>. In other examples, the thickness of the shielding portion <NUM> may also be less than that of the body portion <NUM>.

In some embodiments, the thickness of the body portion <NUM>, the shielding portion <NUM>, and the weak subarea 153a is equal, such that the overall thickness of the protective member <NUM> is uniform, facilitating molding.

<FIG> is a structural schematic diagram of a protective member <NUM> in one embodiment of the application; <FIG> is a schematic sectional view of the protective member <NUM> shown in <FIG> along line E-E; and <FIG> is another schematic sectional view of the protective member <NUM> shown in <FIG> along line E-E. <FIG> is yet another schematic sectional view of the protective member <NUM> shown in <FIG> along line E-E.

In some embodiments, with reference to <FIG>, the protective member <NUM> is provided with a second groove <NUM>. A position of the second groove <NUM> may be set according to product requirements. In some examples, with reference to <FIG>, the second groove <NUM> is arranged on an inside surface of the protective member <NUM> (that is, a surface of one side, close to the cover plate <NUM>, of the protective member <NUM>). In other examples, with reference to <FIG>, the second groove <NUM> is arranged on an outside surface of the protective member <NUM> (that is, a surface of one side, away from the cover plate <NUM>, of the protective member <NUM>). In yet other examples, with reference to <FIG>, the second groove <NUM> is arranged on both the surface of an inner side and the surface of an outer side of the protective member <NUM>.

With reference to <FIG>, the weak portion <NUM> is a bottom wall of the second groove <NUM>. By arranging the second groove <NUM>, the thickness of the weak portion <NUM> may be reduced, that is, the strength of the weak portion <NUM> may be reduced, and the weak portion <NUM> may be broken rapidly when being impacted by the high-temperature and high-pressure substance.

In some embodiments, the second groove <NUM> is an annular groove surrounding the shielding portion <NUM>. Correspondingly, the weak portion <NUM> is annular and is arranged around an edge of the shielding portion <NUM>. When the shielding portion <NUM> is impacted by the high-temperature and high-pressure substance, all parts of the weak portion <NUM> may be broken, so as to increase a discharge rate of the high-temperature and high-pressure substance.

In some examples, one annular second groove <NUM> is provided. Optionally, a plurality of annular second grooves <NUM> may be provided and are arranged at intervals from the body portion <NUM> to the shielding portion <NUM>. The number of the second groove <NUM> may be set according to the capacity of the battery cell <NUM> as long as the temperature and pressure inside the battery cell <NUM> may be relieved to within the safe range within the certain time.

In some embodiments, the second grooves <NUM> are a plurality of strip-shaped grooves, and the plurality of second grooves <NUM> are arranged along the shielding portion <NUM> circumferentially at intervals.

The smaller the thickness of the weak portion <NUM> is, the lower the strength of the weak portion <NUM> is; and under the condition that the thickness of the weak portion <NUM> is too small, when the battery cell vibrates, the weak portion <NUM> is easily broken, resulting in failure of the protective member <NUM>. Conversely, the larger the thickness of the weak portion <NUM> is, the higher the strength of the weak portion <NUM> is; and under the condition that the thickness of the weak portion <NUM> is too large, when the high-temperature and high-pressure substance impacts the shielding portion <NUM>, the time required for the weak portion <NUM> to be broken is too long, influencing the discharge of the high-temperature and high-pressure substance. Thus, in some embodiments, a thickness of the weak portion <NUM> is <NUM> to <NUM>.

In some embodiments, a thickness of the body portion <NUM> may be equal to that of the shielding portion <NUM>. In other embodiments, a thickness of the shielding portion <NUM> may also be less than that of the body portion <NUM>.

As shown in <FIG>, the protective member <NUM> includes an inner second groove <NUM> and an outer second groove <NUM>, the inner second groove <NUM> and the outer second groove <NUM> at least partially overlapping in the thickness direction of the weak portion <NUM>, so as to reduce a minimum thickness of the weak portion <NUM>.

<FIG> shows a schematic flowchart of a manufacturing method for a battery cell in one embodiment of the application. As shown in <FIG>, the manufacturing method may include:.

The related structure of the battery cell manufactured by the manufacturing method of the embodiment may be referred to related contents described in the corresponding embodiments of <FIG>, and is not repeated here.

<FIG> shows a structural schematic diagram of a manufacturing system for a battery cell in one embodiment of the application. As shown in <FIG>, the manufacturing system <NUM> for a battery cell in the embodiment of the application may include a first supply device <NUM>, a second supply device <NUM>, a third supply device <NUM>, a fourth supply device <NUM>, a first assembly device <NUM>, a second assembly device <NUM>, and a third assembly device <NUM>.

The first supply device <NUM> is used for supplying an end cover assembly <NUM>, where the end cover assembly <NUM> includes a cover plate <NUM>, an electrode terminal, and a pressure relief mechanism <NUM>, the pressure relief mechanism <NUM> and the electrode terminal being arranged on the cover plate <NUM>, and the pressure relief mechanism <NUM> being actuated to relieve internal pressure of the battery cell when the internal pressure or temperature reaches a threshold value.

The second supply device <NUM> is used for supplying an electrode assembly <NUM>. The first assembly device <NUM> is used for connecting the electrode assembly <NUM> to the electrode terminal. The third supply device <NUM> is used for supplying a casing <NUM> provided with an accommodation cavity and an opening. The second assembly device <NUM> is used for placing the electrode assembly <NUM> connected to the electrode terminal into the accommodation cavity, and connecting the cover plate <NUM> to the casing <NUM> to close the opening of the casing <NUM>. The fourth supply device <NUM> is used for supplying a protective member <NUM>, where the protective member <NUM> includes a body portion <NUM>, a shielding portion <NUM>, and a weak portion <NUM>, the weak portion <NUM> being configured to connect the body portion <NUM> to the shielding portion <NUM>, and the weak portion <NUM> being configured to be broken when the pressure relief mechanism <NUM> is actuated, so as to disconnect the body portion <NUM> from the shielding portion <NUM>. The third assembly device <NUM> is used for arranging the protective member <NUM> on an outer side of the cover plate <NUM>, connecting the body portion <NUM> to the cover plate <NUM> and shielding the pressure relief mechanism <NUM> by the shielding portion <NUM>.

Claim 1:
A battery cell (<NUM>), comprising:
a battery box comprising a first wall and a pressure relief mechanism (<NUM>), wherein the pressure relief mechanism (<NUM>) is arranged on the first wall, and the pressure relief mechanism (<NUM>) is configured to be actuated to relieve internal pressure of the battery cell (<NUM>) when the internal pressure or temperature of the battery cell (<NUM>) reaches a threshold value;
a protective member (<NUM>) positioned on an outer side of the first wall and comprising a body portion (<NUM>), a shielding portion (<NUM>) and a weak portion (<NUM>), wherein the body portion (<NUM>) is configured to be connected to the first wall, the shielding portion (<NUM>) protrudes outward from the body portion (<NUM>) in a direction perpendicular to the first wall and is configured to shield the pressure relief mechanism (<NUM>), the weak portion (<NUM>) is configured to connect the body portion (<NUM>) to the shielding portion (<NUM>), and the weak portion (<NUM>) is configured to be broken when the pressure relief mechanism (<NUM>) is actuated, so as to disconnect the body portion (<NUM>) from the shielding portion (<NUM>), wherein an outer surface of the first wall is provided with a protrusion (<NUM>), and the shielding portion (<NUM>) is positioned on one side, away from the pressure relief mechanism (<NUM>), of the protrusion (<NUM>) in the direction perpendicular to the first wall, and wherein a plurality of through open holes (<NUM>) are provided between the body portion (<NUM>) and the shielding portion (<NUM>), the weak portion (<NUM>) comprises a plurality of weak subareas (153a), and the plurality of weak subareas (153a) and the plurality of open holes (<NUM>) are alternately provided on a periphery of the shielding portion (<NUM>); and
a protective film (<NUM>) arranged on a surface, facing the shielding portion (<NUM>), of the protrusion (<NUM>) and covering the pressure relief mechanism (<NUM>).