Electrode assembly, method for preparing electrode assembly, battery cell, battery, and electric device

Abstract

Provided are an electrode assembly, a method for preparing an electrode assembly, a battery cell, a battery, and an electric device. The electrode assembly comprises a plurality of electrode sheet groups. The plurality of electrode sheet groups are sequentially arranged at intervals from an inner ring to an outer ring of the electrode assembly, and each electrode sheet group is formed by winding a positive electrode sheet, a first separator, a negative electrode sheet and a second separator for a preset number of turns. The plurality of electrode sheet groups comprise a first electrode sheet group and a second electrode sheet group adjacent to each other, and a gap between the first electrode sheet group and the second electrode sheet group is configured to provide an expansion space for the first electrode sheet group and the second electrode sheet group. Thus, the probability of inner ring collapse of the electrode assembly caused by insufficient expansion space can be reduced.

Description

Electrode assembly, method for preparing electrode assembly, battery cell, battery and electrical device

[0001] This application claims priority to the invention application filed with the Patent Office of China on July 20, 2023, with application number 202310900002.5 and titled “Electrode assembly, method for preparing electrode assembly, battery cell, battery and electrical device,” all contents of which are incorporated into this application by application. Technical Field

[0002] The present application relates to the field of battery technology, and in particular, to an electrode assembly, a method for preparing an electrode assembly, a battery cell, a battery, and an electrical device. Background Art

[0003] Currently, lithium-ion battery electrode assemblies are primarily manufactured using two processes: winding and lamination. After electrode assembly fabrication, the electrode sheets expand during recycling. However, wound electrode assemblies are susceptible to inner coil collapse, creating the risk of lithium deposition.

[0004] Summary of the Invention

[0005] In view of this, embodiments of the present application provide an electrode assembly, a method for preparing an electrode assembly, a battery cell, a battery, and an electrical device, which can reduce the probability of inner ring collapse of the electrode assembly due to insufficient expansion space.

[0006] In a first aspect, an electrode assembly is provided, comprising: a plurality of electrode plate groups, the plurality of electrode plate groups being spaced apart in sequence from the inner ring to the outer ring of the electrode assembly, the electrode plate groups being formed by winding a positive electrode plate, a first isolation membrane, a negative electrode plate and a second isolation membrane a preset number of turns; the plurality of electrode plate groups comprising adjacent first electrode plate groups and second electrode plate groups, the interval between the first electrode plate group and the second electrode plate group being configured to provide expansion space for the first electrode plate group and the second electrode plate group.

[0007] In this embodiment, the electrode assembly is divided into multiple electrode sheet groups, and the spacing between adjacent first and second electrode sheet groups in the multiple electrode sheet groups is configured to provide expansion space for the first and second electrode sheet groups. This allows the spacing between the first and second electrode sheet groups to absorb the expansion of the first and second electrode sheet groups during the battery charge and discharge cycle. This can, on the one hand, reduce the probability of inner circle collapse of the electrode assembly due to insufficient expansion space. On the other hand, it can also reduce the possibility of electrode sheet bending due to insufficient strength of the electrode assembly caused by expansion.

[0008] In a possible implementation, the electrode assembly further includes an insulating buffer portion, which is disposed between the first pole piece group and the second pole piece group, and is used to provide expansion space for the first pole piece group and the second pole piece group.

[0009] In this embodiment, by providing an insulating buffer portion between the first electrode plate group and the second electrode plate group, expansion space can be provided for the first electrode plate group and the second electrode plate group without affecting the performance of the electrode assembly, thereby reducing the probability of inner ring collapse of the electrode assembly due to insufficient expansion space.

[0010] In a possible implementation, the first pole piece group is closer to the inner circle of the electrode assembly than the second pole piece group, and the insulating buffer portion is formed by winding an insulating layer along the outer side of the first pole piece group.

[0011] In this embodiment, the insulating buffer portion is formed by winding the insulating layer along the outer side of the first pole piece group, so that there is an insulating buffer portion everywhere between the first pole piece group and the second pole piece group, reducing the possibility of deformation of the first pole piece group and the second pole piece group when the electrode assembly expands.

[0012] In one possible implementation, the positive pole pieces in the first pole piece group and the second pole piece group are discontinuous, the negative pole pieces in the first pole piece group and the second pole piece group are discontinuous, and the insulating buffer portion is formed by winding the first isolation film and / or the second isolation film along the outer side of the first pole piece group.

[0013] In this embodiment, the insulating buffer portion is formed by winding the first isolation film and / or the second isolation film along the outer side of the first electrode group, which can simplify the preparation process of the electrode assembly and reduce the impact on the performance of the electrode assembly.

[0014] In a possible implementation, the expanded size of the positive electrode sheet in the electrode sheet group is smaller than the expanded size of the negative electrode sheet in the electrode sheet group.

[0015] In this embodiment, by controlling the expanded size of the positive electrode sheet in the electrode sheet group to be smaller than the expanded size of the negative electrode sheet in the electrode sheet group, the risk of excessive movement of lithium ions in the positive electrode sheet to the negative electrode and formation of lithium plating at the negative electrode can be reduced.

[0016] In a possible implementation, the first isolation membrane and / or the second isolation membrane is in a wrinkled shape in the unfolded state.

[0017] In this embodiment, the use of a corrugated first isolation membrane and / or second isolation membrane is conducive to forming gaps between layers of the electrode assembly, further providing expansion space for the electrode assembly and reducing the risk of central hole collapse.

[0018] In a second aspect, a method for preparing an electrode assembly is provided, comprising: winding a positive electrode sheet, a first isolation membrane, a negative electrode sheet and a second isolation membrane a first preset number of turns to form a first electrode sheet group; winding the positive electrode sheet, the first isolation membrane, the negative electrode sheet and the second isolation membrane again a second preset number of turns along the outer side of the first electrode sheet group to form a second electrode sheet group; wherein the interval between the first electrode sheet group and the second electrode sheet group is configured to provide expansion space for the first electrode sheet group and the second electrode sheet group.

[0019] In one possible implementation, the method further includes: providing an insulating buffer portion on the outside of the first pole piece group; winding the positive pole piece, the first isolation film, the negative pole piece and the second isolation film again along the outside of the first pole piece group for a second preset number of turns to form a second pole piece group, including: winding the positive pole piece, the first isolation film, the negative pole piece and the second isolation film again along the outside of the insulating buffer portion for the second preset number of turns to form the second pole piece group; wherein the insulating buffer portion is used to provide expansion space for the first pole piece group and the second pole piece group.

[0020] In a possible implementation, providing the insulating buffer portion on the outer side of the first pole piece group includes: winding an insulating layer multiple times along the outer side of the first pole piece group to form the insulating buffer portion.

[0021] In one possible implementation, the method further includes: after winding the positive electrode sheet, the first isolation film, the negative electrode sheet and the second isolation film for the first preset number of turns, cutting off the positive electrode sheet and the negative electrode sheet; providing an insulating buffer portion on the outside of the first electrode sheet group, including: after forming the first electrode sheet group, continuing to wind the first isolation film and / or the second isolation film for at least one turn to form the insulating buffer portion.

[0022] In one possible implementation, the cutting off of the positive electrode sheet and the negative electrode sheet includes: cutting off the positive electrode sheet and the negative electrode sheet when the unfolded size of the positive electrode sheet of the first preset number of turns is smaller than the unfolded size of the negative electrode sheet of the first preset number of turns.

[0023] In a possible implementation, the first isolation membrane and / or the second isolation membrane is in a wrinkled shape in the unfolded state.

[0024] In a third aspect, a battery cell is provided, comprising the electrode assembly according to the first aspect and any possible implementation of the first aspect.

[0025] In a fourth aspect, a battery is provided, comprising the battery cell provided in the third aspect.

[0026] In a fifth aspect, an electrical device is provided, comprising the battery according to the fourth aspect, wherein the battery is used to provide electrical energy to the electrical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0028] FIG1 is a schematic structural diagram of a vehicle disclosed in an embodiment of the present application.

[0029] FIG2 is a schematic structural diagram of a battery disclosed in an embodiment of the present application.

[0030] FIG3 is a schematic structural diagram of a battery cell disclosed in an embodiment of the present application.

[0031] FIG4 shows a schematic cross-sectional view of an electrode assembly disclosed in an embodiment of the present application.

[0032] FIG5 shows another schematic cross-sectional view of the electrode assembly disclosed in an embodiment of the present application.

[0033] FIG6 shows another schematic cross-sectional view of the electrode assembly disclosed in an embodiment of the present application.

[0034] FIG7 shows a schematic cross-sectional view of another electrode assembly disclosed in an embodiment of the present application.

[0035] FIG8 is a schematic diagram showing the electrode assembly in an expanded state according to an embodiment of the present application.

[0036] FIG9 shows a schematic block diagram of a method for preparing an electrode assembly according to an embodiment of the present application.

[0037] FIG10 shows another schematic block diagram of a method for preparing an electrode assembly according to an embodiment of the present application.

[0038] 11 to 14 are schematic diagrams showing a process for preparing an electrode assembly according to an embodiment of the present application. DETAILED DESCRIPTION

[0039] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0040] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first" and "second" in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary-secondary relationship.

[0041] The directional words appearing in the following description are all directions shown in the figures, and do not limit the specific structure of this application. In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0042] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the 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 refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0043] The term "and / or" in this application simply describes an association between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this application generally indicates that the related objects are in an "or" relationship.

[0044] The term "multiple" in this application refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0045] In the embodiment of the present application, the battery cell may be a secondary battery. A secondary battery refers to a battery cell that can be continuously used by activating active materials by charging after the battery cell is discharged.

[0046] The battery cells can be lithium-ion batteries, sodium-ion batteries, sodium-lithium-ion batteries, lithium metal batteries, sodium metal batteries, lithium-sulfur batteries, magnesium-ion batteries, nickel-hydrogen batteries, nickel-cadmium batteries, lead-acid batteries, etc., which are not limited in the embodiments of the present application.

[0047] A battery cell typically includes an electrode assembly. This assembly includes a positive electrode, a negative electrode, and a separator. During the charge and discharge process of a battery cell, active ions (such as lithium ions) are inserted and removed between the positive and negative electrodes. The separator, placed between the positive and negative electrodes, prevents short circuits between the positive and negative electrodes while allowing the active ions to pass through.

[0048] In some embodiments, the positive electrode may be a positive electrode sheet, which may include a positive electrode current collector and a positive electrode active material disposed on at least one surface of the positive electrode current collector.

[0049] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0050] As an example, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum or stainless steel with a silver surface treatment, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel or titanium, etc. may be used. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0051] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0052] In some embodiments, the negative electrode may be a negative electrode sheet, and the negative electrode sheet may include a negative electrode current collector.

[0053] As an example, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum or stainless steel with a silver surface treatment, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel or titanium, etc. may be used. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0054] As an example, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector.

[0055] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material is provided on either or both of the two facing surfaces of the negative electrode current collector.

[0056] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.

[0057] In some embodiments, the negative electrode may be a metal foam. The metal foam may be nickel foam, copper foam, aluminum foam, alloy foam, or carbon foam. When the metal foam is used as the negative electrode, the surface of the metal foam may or may not be provided with a negative electrode active material.

[0058] As an example, the negative electrode current collector may be filled with or / and deposited with a lithium source material, potassium metal, or sodium metal, where the lithium source material is lithium metal and / or a lithium-rich material.

[0059] In some embodiments, the material of the positive electrode current collector may be aluminum, and the material of the negative electrode current collector may be copper.

[0060] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode and the negative electrode.

[0061] In some embodiments, the separator is a separator. The present application has no particular limitation on the type of separator, and any known separator with a porous structure having good chemical and mechanical stability can be selected.

[0062] As an example, the main material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramics.

[0063] In some embodiments, the separator is a solid electrolyte, which is disposed between the positive electrode and the negative electrode and serves to transport ions and isolate the positive and negative electrodes.

[0064] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected based on needs. The electrolyte can be liquid, gel, or solid.

[0065] In some embodiments, the electrode assembly is a wound structure, wherein the positive electrode sheet and the negative electrode sheet are wound into a wound structure.

[0066] In some embodiments, the electrode assembly is a laminate structure.

[0067] As an example, multiple positive electrode sheets and multiple negative electrode sheets can be provided respectively, and the multiple positive electrode sheets and the multiple negative electrode sheets can be alternately stacked.

[0068] As an example, multiple positive electrode sheets may be provided, and the negative electrode sheet is folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0069] As an example, both the positive electrode sheet and the negative electrode sheet are folded to form a plurality of stacked folded segments.

[0070] As an example, multiple separators may be provided, each of which is provided between any adjacent positive electrode sheets or negative electrode sheets.

[0071] As an example, the separator may be provided continuously, and may be provided between any adjacent positive electrode sheets or negative electrode sheets by folding or winding.

[0072] In some embodiments, the shape of the electrode assembly can be cylindrical, flat, or polygonal.

[0073] In some embodiments, the electrode assembly is provided with tabs that can conduct current from the electrode assembly. The tabs include a positive tab and a negative tab.

[0074] In some embodiments, a battery cell may include a housing. The housing is used to encapsulate components such as the electrode assembly and electrolyte. The housing may be a steel housing, an aluminum housing, a plastic housing (e.g., polypropylene), a composite metal housing (e.g., a copper-aluminum composite housing), or an aluminum-plastic film. The housing includes a shell and a cover.

[0075] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a soft-pack battery cell or a battery cell of other shapes. The prismatic battery cell includes a square-shell battery cell, a blade-shaped battery cell, and a polygonal battery. The polygonal battery is, for example, a hexagonal battery, etc. There is no special limitation in this application.

[0076] The battery mentioned in the embodiments of the present application may include one or more battery cells to provide a single physical module with higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, in parallel or in hybrid through a busbar.

[0077] In some embodiments, the battery may be a battery module. When there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0078] In some embodiments, the battery may be a battery pack, which includes a case and battery cells, wherein the battery cells or battery modules are housed in the case.

[0079] In some embodiments, the box body can be used as a part of the chassis structure of the vehicle. For example, part of the box body can become at least a part of the floor of the vehicle, or part of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0080] Lithium-ion batteries have high energy density, high safety, long service life, and are green and environmentally friendly to the social environment. They are widely used in passenger cars, commercial vehicles, electric bicycles, heavy trucks, energy storage facilities, battery swap stations, engineering manufacturing, smart devices, etc., and also promote technological development and research in communications, medical equipment, energy development, etc.

[0081] At present, the electrode assemblies of lithium-ion batteries are mainly made using two processes, one is the winding process and the other is the lamination process. The existing wound electrode assembly is made by placing the positive electrode sheet, the separator and the negative electrode sheet in an alternating manner, and successively entering the winding equipment to tightly wind the positive electrode sheet, the separator and the negative electrode sheet together. However, with the charge and discharge cycle, the electrode sheet is always in a state of expansion and contraction, and the strength of the electrode sheet in the inner circle of the wound electrode assembly will be lacking, causing the central hole of the electrode assembly to collapse. After the collapse occurs, it is easy to cause lithium deposition, and the lithium deposition and collapse will cyclically worsen each other, causing the battery to be dangerous.

[0082] In view of this, an embodiment of the present application provides an electrode assembly, which divides the electrode assembly into multiple electrode groups, and the intervals between adjacent first electrode groups and second electrode groups in the multiple electrode groups are configured to provide expansion space for the first electrode group and the second electrode group, so that during the battery charge and discharge cycle, the interval between the first electrode group and the second electrode group can absorb the expansion of the first electrode group and the second electrode group, thereby reducing the probability of inner ring collapse of the electrode assembly due to insufficient expansion space.

[0083] The technical solutions described in the embodiments of this application are applicable to various electrical devices using batteries.

[0084] Electrical devices may include vehicles, mobile phones, portable devices, laptop computers, ships, spacecraft, electric toys, and electric tools, etc. Vehicles may include fuel vehicles, gas vehicles, or new energy vehicles. New energy vehicles may include pure electric vehicles, hybrid vehicles, or extended-range vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical devices.

[0085] For the convenience of description, the following embodiments are described by taking a vehicle as an example of an electrical device.

[0086] For example, as shown in FIG1 , it is a structural schematic diagram of a vehicle 1 according to an embodiment of the present application. The vehicle 1 may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A motor 40, a controller 30 and a battery 10 may be provided inside the vehicle 1. The controller 30 is used to control the battery 10 to supply power to the motor 40. For example, a battery 10 may be provided at the bottom, front or rear of the vehicle 1. The battery 10 may be used to power the vehicle 1. For example, the battery 10 may be used as an operating power source for the vehicle 1, for the circuit system of the vehicle 1, for example, for the working power requirements during the start-up, navigation and operation of the vehicle 1. In another embodiment of the present application, the battery 10 may not only be used as an operating power source for the vehicle 1, but also as a driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0087] For example, as shown in FIG2 , it is a schematic structural diagram of a battery 10 according to an embodiment of the present application. The battery 10 may include a plurality of battery cells 20. In addition to the battery cells 20, the battery 10 may also include a case 11, the interior of the case 11 being a hollow structure, and a plurality of battery cells 20 may be accommodated in the case 11. As shown in FIG2 , the case 11 may include two parts, referred to herein as a first case portion 111 and a second case portion 112, the first case portion 111 and the second case portion 112 being snapped together. The shapes of the first case portion 111 and the second case portion 112 may be determined according to the shape of the combination of the plurality of battery cells 20, and at least one of the first case portion 111 and the second case portion 112 may have an opening. For example, as shown in FIG2 , only one of the first case portion 111 and the second case portion 112 is a hollow cuboid with an opening, while the other is in the shape of a plate to cover the opening. Here, for example, the second housing portion 112 is a hollow rectangular parallelepiped with only one open face, and the first housing portion 111 is plate-shaped. The first housing portion 111 covers the opening of the second housing portion 112 to form a housing 11 having a closed chamber. This chamber can be used to accommodate multiple battery cells 20. Multiple battery cells 20 are connected in parallel, series, or in a mixed series arrangement and then placed within the housing 11 formed by the first housing portion 111 and the second housing portion 112 being fastened together.

[0088] For another example, unlike that shown in FIG2 , the first and second housing portions 111, 112 can each be a hollow cuboid with only one open face. The opening of the first and second housing portions 111, 112 are positioned opposite each other, and the first and second housing portions 111, 112 are engaged with each other to form a housing having a closed chamber. Multiple battery cells 20 are connected in parallel, series, or in a mixed series arrangement and then placed within the housing 11 formed by the engagement of the first and second housing portions 111, 112.

[0089] In some embodiments, the battery 10 may further include other structures, which will not be described in detail here. For example, the battery 10 may further include a busbar component (not shown in the figure), which is used to realize electrical connection between multiple battery cells 20. Specifically, the busbar component can realize electrical connection between the battery cells 20 by connecting the electrode terminals of the battery cells 20. In some embodiments, the busbar component can be fixed to the electrode terminals of the battery cells 20 by welding. The electrical energy of the multiple battery cells 20 can be further led out through the box through a conductive mechanism. In some embodiments, the conductive mechanism may also belong to the busbar component.

[0090] In order to meet different power requirements, the number of battery cells 20 can be multiple, and multiple battery cells can be connected in series, in parallel, or in hybrid, where hybrid refers to a mixture of series and parallel connections. The battery 10 can also be called a battery pack. In some embodiments, multiple battery cells can first be connected in series, in parallel, or in hybrid to form a battery module, and multiple battery modules can then be connected in series, in parallel, or in hybrid to form the battery 10. In other words, multiple battery cells can directly form the battery 10, or they can first form a battery module, and then the battery module can form the battery 10.

[0091] For ease of explanation, the technical solution of the present application is described below using the cylindrical battery cell 20 shown in FIG2 as an example. However, it should be understood that the battery cell 20 of the present embodiment can be a cylindrical battery cell, a square shell battery cell, a blade-shaped battery cell, etc.

[0092] Figure 3 is a schematic diagram of the structure of a battery cell according to an embodiment of the present application. As shown in Figure 3, the battery cell 20 includes a housing 210, an electrode assembly 220, and an end cap assembly 230. The housing 210 and the end cap assembly 230 form an outer shell or battery case. The housing 210 is formed of a metal, such as aluminum. The shape of the housing 210 is determined by the combination of one or more electrode assemblies 220. For example, the housing 210 can be a hollow cylinder as shown in Figure 3.

[0093] The housing 210 has an opening, and the electrode assembly 220 is accommodated in the housing 210. The end cap assembly 230 is used to cover the opening to accommodate the electrode assembly 220 in the housing 210. The housing 210 and the end cap assembly 230 accommodate and protect the electrode assembly 220 and other components. The housing 210 is filled with an electrolyte, such as an electrolyte solution.

[0094] As shown in Figure 3, the end cap assembly 230 includes a negative end cap assembly 2301 and a positive end cap assembly 2302. The negative end cap assembly 2301 and the positive end cap assembly 2302 respectively cover the opening of the housing 210 from both ends to cover the electrode assembly 220 within the housing 210. The negative end cap assembly 2301 is used to provide a negative electrode terminal, and the positive end cap assembly 2302 is used to provide a positive electrode terminal. The electrode assembly 220 is provided with a tab 221, wherein the positive electrode terminal is electrically connected to the positive tab of the electrode assembly 220, and the negative electrode terminal is electrically connected to the negative tab of the electrode assembly 220. The number of positive and negative electrode terminals can be any number. For example, the battery cell 20 can have two positive electrode terminals and two negative electrode terminals, with the two positive electrode terminals provided on the positive end cap assembly 2302 and the two negative electrode terminals provided on the negative end cap assembly 2301. The positive end cap assembly 2302 has the same structure as the negative end cap assembly 2301. Hereinafter, the end cap assembly 230 described may be any one of the positive end cap assembly 2302 and the negative end cap assembly 2301 .

[0095] In the battery cell 20 , the electrode assembly 220 may be provided as a single one or multiple ones according to actual use requirements. For example, as shown in FIG. 3 , one electrode assembly 220 is provided in the battery cell 20 .

[0096] Figure 4 shows a schematic cross-sectional view of an electrode assembly. As shown in Figure 4, the electrode assembly 220 includes multiple electrode sheet groups, which are spaced sequentially from the inner circle to the outer circle of the electrode assembly 220. The electrode sheet groups are formed by winding a positive electrode sheet 2201, a first separator 2203, a negative electrode sheet 2202, and a second separator 2204 for a predetermined number of turns. The multiple electrode sheet groups include adjacent first electrode sheet groups 221 and second electrode sheet groups 222. The spacing between the first electrode sheet groups 221 and the second electrode sheet groups 222 is configured to provide expansion space for the first electrode sheet groups 221 and the second electrode sheet groups 222.

[0097] It should be noted that the technical solution provided in the embodiment of the present application is mainly aimed at a wound electrode assembly, but those skilled in the art understand that it does not exclude that the technical solution is applicable to a laminated electrode assembly.

[0098] Optionally, the materials of the first isolation film 2203 and the second isolation film 2204 may be the same or different. The first isolation film 2203 and the second isolation film 2204 are alternately sandwiched between the positive electrode sheet 2201 and the negative electrode sheet 2202 .

[0099] In addition, for traditional wound electrode assemblies, the positive electrode sheet, the first separator, the negative electrode sheet, and the second separator are tightly wound together, that is, the layers are bonded to each other. Therefore, during the cycle, when the electrode sheet expands, it is very likely to be squeezed toward the center hole of the electrode assembly. As the cycle intensifies, the strength of the electrode sheet in the inner circle will be insufficient, resulting in collapse at the center hole. The electrode assembly 220 in the embodiment of the present application can be divided into multiple electrode sheet groups, each of which is formed by the normal winding of the positive electrode sheet 2201, the first separator 2203, the negative electrode sheet 2202, and the second separator 2204. There is a certain distance between two adjacent electrode sheet groups, that is, the outer layer of the electrode sheet group in the inner circle of the electrode assembly 220 and the inner layer of the electrode sheet group in the outer circle of the electrode assembly 220 are not bonded to each other, but are separated by a certain distance. For example, there is a distance H between the first electrode sheet group 221 and the second electrode sheet group 222 in Figure 4. The existence of the gap H allows the first electrode set 221 and the second electrode set 222 to move closer to each other when they expand, thereby reducing the force on the electrode located in the inner circle of the electrode assembly 220.

[0100] Optionally, the electrode assembly 220 in the embodiment of the present application may include two or more electrode sheet groups. When the electrode assembly 220 includes two or more electrode sheet groups, the spacing between each two adjacent electrode sheet groups may be configured to provide expansion space for the two adjacent electrode sheet groups. In other words, any two adjacent electrode sheet groups in the electrode assembly 220 may be the first electrode sheet group 221 and the second electrode sheet group 222.

[0101] Optionally, the positive electrode sheet 221, the first separator 2203, the negative electrode sheet 2202, and the second separator 2204 in different electrode sheet groups can be wound with the same number of turns or with different numbers of turns. In other words, the preset number of turns can include one preset value or multiple preset values, which is not limited in this embodiment of the application.

[0102] In addition, the interval H can be determined according to various factors during the design stage. For example, the layer gap (gap) between the positive electrode sheet 2201 and the negative electrode sheet 2202 can be calculated based on one or more factors including the thickness of the positive electrode sheet 2201, the thickness of the negative electrode sheet 2202, the thickness of the first isolation film 2203, the thickness of the second isolation film 2204, the expansion rate, and the residual space in the electrode assembly 220, and the required reserved expansion space can be confirmed before further confirming the interval H.

[0103] In some embodiments, the multiple electrode groups can be coaxially arranged. For example, the positive electrode 2201, the first isolation membrane 2203, the negative electrode 2202 and the second isolation membrane 2204 in each electrode group are all wound around the central hole of the electrode assembly 220.

[0104] In this embodiment, the electrode assembly 220 is divided into a plurality of electrode sheet groups, and the interval H between adjacent first electrode sheet groups 221 and second electrode sheet groups 222 in the plurality of electrode sheet groups is configured to provide expansion space for the first electrode sheet group 221 and the second electrode sheet group 222. Therefore, during the charge and discharge cycle of the battery, the interval H between the first electrode sheet group 221 and the second electrode sheet group 222 can absorb the expansion of the first electrode sheet group 221 and the second electrode sheet group 222. On the one hand, the probability of collapse of the inner ring of the electrode assembly 220 due to insufficient expansion space can be reduced. On the other hand, the possibility of bending of the electrode sheet due to insufficient strength of the electrode assembly 220 caused by expansion can also be reduced.

[0105] Figure 5 shows another schematic cross-sectional view of an electrode assembly according to an embodiment of the present application. As shown in Figure 5, the electrode assembly 220 further includes an insulating buffer portion 223, which is disposed between the first electrode assembly 221 and the second electrode assembly 222. The insulating buffer portion 223 is used to provide expansion space for the first electrode assembly 221 and the second electrode assembly 222.

[0106] It should be noted that the insulating buffer portion 223 is not only an insulating material, but also an elastic material. For example, the insulating buffer portion 223 can be the above-mentioned isolation film 2203. For another example, the insulating buffer portion 223 can also be at least one of polyethylene (PE) material, polypropylene (PT) material, polyethylene terephthalate (PET) material or biaxially oriented polypropylene film (BOPP) material. In addition, the insulating buffer portion 223 also needs to be resistant to electrolyte. Those skilled in the art understand that as long as the material does not affect the performance of the battery, it can be used as the insulating buffer portion 223 in the embodiment of the present application.

[0107] That is to say, in the embodiment of the present application, an insulating buffer portion 223 is provided between the first pole piece group 221 and the second pole piece group 222, so that a gap H is provided between the first pole piece group 221 and the second pole piece group 222, and since the insulating buffer portion 223 can be an elastic material, that is, it can be compressed, the insulating buffer portion 223 can provide expansion space for the first pole piece group 221 and the second pole piece group 22.

[0108] In this embodiment, by providing an insulating buffer portion 223 between the first electrode group 221 and the second electrode group 222, expansion space can be provided for the first electrode group 221 and the second electrode group 222 without affecting the performance of the electrode assembly, thereby reducing the probability of inner ring collapse of the electrode assembly 220 due to insufficient expansion space.

[0109] In other embodiments, the insulating buffer portion 223 may not be provided between the first electrode set 221 and the second electrode set 222 , that is, an air gap is provided between the two.

[0110] Optionally, as shown in Figures 4 and 5, the first pole piece group 221 is closer to the inner circle of the electrode assembly 220 than the second pole piece group 222, wherein the insulating buffer portion 223 is formed by winding the insulating layer along the outer side of the first pole piece group 221.

[0111] In some embodiments, the insulating buffer portion 223 formed by winding the insulating layer may also be coaxially disposed with the first electrode assembly 221 and / or the second electrode assembly 222. For example, the insulating buffer portion 223 is also wound around the central hole of the electrode assembly 220.

[0112] In this embodiment, the insulating buffer portion 223 is formed by winding an insulating layer along the outer side of the first pole piece group 221, so that the insulating buffer portion 223 is provided everywhere between the first pole piece group 221 and the second pole piece group 222, thereby reducing the possibility of deformation of the first pole piece group 221 and the second pole piece group 222 when the electrode assembly 220 expands.

[0113] In one example, as shown in Figures 6 and 7, the positive electrode sheets 2201 in the first electrode sheet group 221 and the second electrode sheet group 222 are discontinuous, and the negative electrode sheets 2202 in the first electrode sheet group 221 and the second electrode sheet group 222 are discontinuous. The insulating buffer portion 223 is formed by winding the first isolation film 2203 and / or the second isolation film 2204 along the outer side of the first electrode sheet group 221.

[0114] It should be understood that the electrode assembly 220 shown in FIG. 6 can be applied to a cylindrical battery cell, and the electrode assembly 220 shown in FIG. 7 can be applied to a square battery cell, but this embodiment of the present application is not limited thereto.

[0115] In one embodiment, after the positive electrode sheet 2201, the first isolation film 2203, the negative electrode sheet 2202 and the second isolation film 2204 are wound a preset number of times, the positive electrode sheet 2201 and the negative electrode sheet 2202 can be cut off without cutting the first isolation film 2203 and the second isolation film 2204, that is, the first isolation film 2203 and the second isolation film 2204 continue to be wound a few times to form an insulating buffer portion 223. After that, the positive electrode sheet 2201 and the negative electrode sheet 2202 are added in turn and wound together with the first isolation film 2203 and the second isolation film 2204 for a preset number of times to form a second electrode sheet group 222.

[0116] In another embodiment, after the positive electrode sheet 2201, the first isolation film 2203, the negative electrode sheet 2202 and the second isolation film 2204 are wound a preset number of times, the positive electrode sheet 2201 and the negative electrode sheet 2202 can be cut off, and the first isolation film 2203 (or the second isolation film 2204) can be cut off at the same time, and the second isolation film 2204 (or the first isolation film 2203) is retained and continued to be wound for several turns to form an insulating buffer portion 223. Thereafter, the positive electrode sheet 2201, the negative electrode sheet 2202 and the first isolation film 2203 (or the second isolation film 2204) are added in and wound together with the second isolation film 2204 (or the first isolation film 2203) for a preset number of turns to form a second electrode sheet group 222.

[0117] In this embodiment, the insulating buffer portion 223 is formed by winding the first isolation film 2203 and / or the second isolation film 2204 along the outer side of the first pole piece group 221, which can simplify the preparation process of the electrode assembly 220 and reduce the impact on the performance of the electrode assembly 220.

[0118] In another example, after the positive electrode sheet 2201, the first isolation film 2203, the negative electrode sheet 2202 and the second isolation film 2204 are wound a preset number of times, the positive electrode sheet 2201, the first isolation film 2203, the negative electrode sheet 2202 and the second isolation film 2204 are all cut off, and then an insulating layer of other materials is added and wound several times to form an insulating buffer portion 223. After that, the positive electrode sheet 2201, the first isolation film 2203, the negative electrode sheet 2202 and the second isolation film 2204 are added in turn and wound together for a preset number of times to form a second electrode group 222.

[0119] Optionally, the expanded size of the positive electrode sheet in the electrode sheet group is smaller than the expanded size of the negative electrode sheet in the electrode sheet group. For example, as shown in FIG8 , the expanded size L1 of the positive electrode sheet 2201 in the first electrode sheet group 221 and / or the second electrode sheet group 222 is smaller than the expanded size L2 of the negative electrode sheet 2202 in the first electrode sheet group 221 and / or the second electrode sheet group 222.

[0120] In this embodiment, by controlling the expanded size of the positive electrode plate 2201 in the electrode plate group to be smaller than the expanded size of the negative electrode plate 2202 in the electrode plate group, the risk of excessive movement of lithium ions in the positive electrode plate to the negative electrode and formation of lithium plating at the negative electrode can be reduced.

[0121] In some examples, the first isolation film 2203 and / or the second isolation film 2204 are wrinkled in the unfolded state.

[0122] In this embodiment, the use of a corrugated first isolation membrane 2203 and / or second isolation membrane 2204 is conducive to forming gaps between layers of the electrode assembly 220, further providing expansion space for the electrode assembly 220 and reducing the risk of central hole collapse.

[0123] In other examples, the first isolation membrane 2203 and / or the second isolation membrane 2204 are planar in the unfolded state.

[0124] In other embodiments, the problem of central hole collapse of the electrode assembly 220 may be improved by preparing the electrode assembly 220 using only the corrugated first isolation film 2203 and / or the second isolation film 2204 .

[0125] The present application also provides a method for preparing an electrode assembly. This method can prepare the electrode assembly 220 described in the various embodiments above. As shown in FIG9 , the method 300 includes some or all of the following.

[0126] S310 , winding the positive electrode sheet 2201 , the first isolation film 2203 , the negative electrode sheet 2202 and the second isolation film 2204 by a first preset number of turns to form a first electrode assembly 221 .

[0127] S320 , winding the positive electrode sheet 2201 , the first isolation film 2203 , the negative electrode sheet 2202 and the second isolation film 2204 again along the outer side of the first electrode sheet assembly 221 for a second preset number of turns to form a second electrode sheet assembly 222 .

[0128] The interval H between the first electrode set 221 and the second electrode set 222 is configured to provide expansion space for the first electrode set 221 and the second electrode set 222 .

[0129] As an example, as shown in FIG10 , the method 300 may further include: S315 , disposing an insulating buffer portion 223 on the outer side of the first pole piece group.

[0130] Optionally, S320, i.e., winding the positive electrode sheet 2201, the first isolation film 2203, the negative electrode sheet 2202 and the second isolation film 2204 again along the outer side of the first electrode sheet group 221 for a second preset number of turns to form a second electrode sheet group 222, includes: winding the positive electrode sheet 2201, the first isolation film 2203, the negative electrode sheet 2202 and the second isolation film 2204 again along the outer side of the insulating buffer part 223 for a second preset number of turns to form a second electrode sheet group 222.

[0131] As an example, S315 , ie, providing an insulating buffer portion 223 on the outer side of the first pole piece group, includes: winding an insulating layer multiple times along the outer side of the first pole piece group 221 to form the insulating buffer portion 223 .

[0132] As an example, method 300 further includes: after winding the positive electrode sheet 2201, the first separator 2203, the negative electrode sheet 2202, and the second separator 2204 a first predetermined number of turns, cutting the positive electrode sheet 2201 and the negative electrode sheet 2202. S315, i.e., providing an insulating buffer 223 on the outer side of the first electrode sheet assembly, includes: after forming the first electrode sheet assembly 221, continuing to wind the first separator 2203 and / or the second separator 2204 at least one more turn to form the insulating buffer 223.

[0133] As an example, cutting off the positive electrode sheet 2201 and the negative electrode sheet 2202 includes: cutting off the positive electrode sheet 2201 and the negative electrode sheet 2202 when the unfolded size of the positive electrode sheet 2201 of the first preset number of turns is smaller than the unfolded size of the negative electrode sheet 2202 of the first preset number of turns.

[0134] In some examples, the first isolation film 2203 and / or the second isolation film 2204 are wrinkled in the unfolded state.

[0135] The method 300 for preparing an electrode assembly according to an embodiment of the present application will be described in detail below with reference to Figures 11 to 14. It should be noted that the following description is based on an example in which the electrode assembly 220 includes two electrode sheet groups, namely, a first electrode sheet group 221 and a second electrode sheet group 222. However, those skilled in the art will appreciate that if the electrode assembly 220 includes more than two electrode sheet groups, the steps in Figures 12 and 13 can be repeated.

[0136] Specifically, during the initial winding process, the positive electrode sheet 2201, the first separator 2203, the negative electrode sheet 2202, and the second separator 2204 are sequentially fed into the winding needle for normal winding. When the winding needle winds the electrode to a preset number of inner turns, and under conditions that ensure relevant parameters, for example, the unfolded size of the positive electrode sheet 2201 wound into the winding needle is smaller than the unfolded size of the negative electrode sheet 2202, the positive electrode sheet cutter cuts the positive electrode sheet 2201, and the negative electrode sheet cuts the negative electrode sheet 2202, forming the first electrode sheet assembly 221 shown in FIG11. The winding needle then continues winding, stopping the feeding of the positive electrode sheet 2201 and the negative electrode sheet 2202, while continuing to feed the first separator 2203 and the second separator 2204, until the winding reaches the preset number of turns, forming the insulating buffer portion 223 shown in FIG12. Then, the positive electrode sheet 2201 and the negative electrode sheet 2202 are fed in, and the winding needle continues to wind the preset number of turns to form the second electrode sheet assembly 222 as shown in Figure 13. Finally, the finishing glue 224 is applied to the outside of the second electrode sheet assembly 222 to form the electrode assembly 220 as shown in Figure 14.

[0137] In addition, during the design stage, the required gap between the positive electrode sheet 2201 and the negative electrode sheet 2202 can be calculated in advance based on the thickness of the positive electrode sheet 2201, the thickness of the negative electrode sheet 2202, the thickness of the first isolation film 2203, the thickness of the second isolation film 2204, the preset number of turns, the expansion rate, and the residual space, so as to confirm the required reserved thickness of the first isolation film 2203 and the second isolation film 2204 and the number of winding layers.

[0138] For example, the larger the preset number of turns, the greater the expansion, the larger the required gap, and the more turns of the first isolation film 2203 and the second isolation film 2204 that need to be wound around the first electrode assembly 221 and the second electrode assembly 222.

[0139] In this embodiment, by stopping winding the positive electrode sheet 2201 and the negative electrode sheet 2202 between the first electrode sheet group 221 and the second electrode sheet group 222, and continuing to wind the first isolation film 2203 and the second isolation film 2204 for several turns, sufficient expansion space is reserved for the first electrode sheet group 221 and the second electrode sheet group 222, thereby reducing problems such as inner ring collapse and lithium deposition caused by insufficient expansion space during the cycle, and improving the yield and quality rate of the electrode assembly.

[0140] The embodiment of the present application further provides a battery cell, including the electrode assembly 220 provided in the various embodiments described above.

[0141] An embodiment of the present application further provides a battery, including the battery described in the various embodiments above.

[0142] An embodiment of the present application further provides an electrical device, comprising the battery described in the various embodiments above, wherein the battery is used to provide electrical energy to the electrical device.

[0143] The electric device may be a vehicle as shown in FIG1 , or may be any device using a battery.

[0144] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. An electrode assembly, characterized in that: include: A plurality of electrode sheet groups, wherein the plurality of electrode sheet groups are sequentially arranged from the inner circle to the outer circle of the electrode assembly, and the electrode sheet groups are formed by winding a positive electrode sheet, a first separator, a negative electrode sheet, and a second separator for a preset number of turns; The plurality of pole piece groups include adjacent first pole piece groups and second pole piece groups, and the interval between the first pole piece group and the second pole piece group is configured to provide expansion space for the first pole piece group and the second pole piece group.

2. The electrode assembly according to claim 1, characterized in that: The electrode assembly further includes an insulating buffer portion, which is disposed between the first pole piece group and the second pole piece group, and is used to provide expansion space for the first pole piece group and the second pole piece group.

3. The electrode assembly according to claim 2, characterized in that: The first pole piece group is closer to the inner circle of the electrode assembly than the second pole piece group, and the insulating buffer portion is formed by winding an insulating layer along the outer side of the first pole piece group.

4. The electrode assembly according to claim 3, characterized in that: The positive pole sheets in the first pole sheet group and the second pole sheet group are discontinuous, the negative pole sheets in the first pole sheet group and the second pole sheet group are discontinuous, and the insulating buffer portion is formed by winding the first isolation film and / or the second isolation film along the outer side of the first pole sheet group.

5. The electrode assembly according to any one of claims 1 to 4, characterized in that: The unfolded size of the positive electrode sheet in the electrode sheet group is smaller than the unfolded size of the negative electrode sheet in the electrode sheet group.

6. The electrode assembly according to any one of claims 1 to 5, characterized in that: The first isolation film and / or the second isolation film is in a wrinkled shape in an unfolded state.

7. A method for preparing an electrode assembly, characterized in that: include: Winding the positive electrode sheet, the first separator, the negative electrode sheet and the second separator by a first preset number of turns to form a first electrode sheet group; The positive electrode sheet, the first separator, the negative electrode sheet and the second separator Winding the first pole piece group again for a second preset number of turns along the outer side of the first pole piece group to form a second pole piece group; Wherein, the interval between the first pole piece group and the second pole piece group is configured to provide expansion space for the first pole piece group and the second pole piece group.

8. The method according to claim 7, characterized in that The method further comprises: An insulating buffer portion is provided on the outer side of the first pole piece group; The step of winding the positive electrode sheet, the first separator, the negative electrode sheet and the second separator again for a second preset number of turns along the outer side of the first electrode sheet group to form a second electrode sheet group includes: Winding the positive electrode sheet, the first separator, the negative electrode sheet and the second separator again along the outer side of the insulating buffer portion for a second preset number of turns to form the second electrode sheet group; Wherein, the insulating buffer portion is used to provide expansion space for the first pole piece group and the second pole piece group.

9. The method according to claim 8, characterized in that The insulating buffer portion is provided on the outer side of the first pole piece group, comprising: The insulating layer is wound multiple times along the outer side of the first pole piece group to form the insulating buffer portion.

10. The method according to claim 8 or 9, characterized in that: The method further comprises: After the positive electrode sheet, the first separator, the negative electrode sheet and the second separator are wound by the first preset number of turns, the positive electrode sheet and the negative electrode sheet are cut off; The insulating buffer portion is provided on the outer side of the first pole piece group, comprising: After forming the first pole piece group, the first isolation film and / or the second isolation film is further wound for at least one turn to form the insulating buffer portion.

11. The method according to claim 10, characterized in that The cutting of the positive electrode sheet and the negative electrode sheet comprises: When the unfolded size of the positive electrode sheet after the first preset number of turns is smaller than the unfolded size of the negative electrode sheet after the first preset number of turns, the positive electrode sheet and the negative electrode sheet are cut off.

12. The method according to any one of claims 7 to 11, characterized in that The first isolation film and / or the second isolation film is in a wrinkled shape in an unfolded state.

13. A battery cell, characterized in that: The electrode assembly comprises the electrode assembly as claimed in any one of claims 1 to 6.

14. A battery, characterized in that: Comprising the battery cell as claimed in claim 13.

15. An electrical device, characterized in that: The battery as claimed in claim 14 is used to provide electrical energy to the electrical device.

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