CN112768748A

CN112768748A - Battery monomer, battery, electric equipment and method and device for preparing battery monomer

Info

Publication number: CN112768748A
Application number: CN202110373649.8A
Authority: CN
Inventors: 许虎; 刘晓梅; 金海族; 梁成都
Original assignee: Jiangsu Contemporary Amperex Technology Ltd
Current assignee: Jiangsu Contemporary Amperex Technology Ltd
Priority date: 2021-04-07
Filing date: 2021-04-07
Publication date: 2021-05-07
Anticipated expiration: 2041-04-07
Also published as: CN112768748B

Abstract

The embodiment of the application discloses battery monomer, battery, consumer and preparation battery monomer's method and device, is equipped with the battery in the consumer, has one or more battery monomer in the battery, and wherein battery monomer includes: a housing having a cylindrical accommodation chamber; and the electrode assembly is arranged in the accommodating cavity, and the projection of the electrode assembly along the height direction of the battery cell is polygonal. Even if the electrode assembly in the single battery expands after charging and discharging, a remaining space still exists between the electrode assembly and the inner wall of the shell, so that the outer peripheral surface of the electrode assembly is prevented from being extruded by the shell, the electrode assembly can be allowed to expand, the problems that the performance of the single battery is degraded and the performance of the single battery is attenuated due to falling of active substances, difficult electrolyte infiltration, breakage of the pole pieces and the like caused by excessive extrusion of the pole pieces are prevented, and the problem that the performance of the single battery is attenuated and the cycle life of the single battery is influenced is further solved.

Description

Battery monomer, battery, electric equipment and method and device for preparing battery monomer

Technical Field

The application relates to the technical field of batteries, in particular to a battery monomer, a battery, electric equipment, and a method and a device for preparing the battery monomer.

Background

Batteries are widely applied in the field of new energy resources, such as electric vehicles, new energy vehicles and the like, and the new energy vehicles and the electric vehicles become new development trends of the automobile industry.

In applications where the cycle life of a battery is a non-negligible factor, degradation in battery performance can affect the cycle life of the battery.

Disclosure of Invention

The application aims to provide a single battery, a battery, electric equipment, a method and a device for preparing the single battery, so as to relieve the problem that the performance attenuation of the single battery affects the cycle life of the single battery.

The embodiment of the application is realized as follows:

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

a housing having a cylindrical accommodation chamber;

and the electrode assembly is arranged in the accommodating cavity, and the projection of the electrode assembly along the height direction of the battery cell is polygonal.

In the technical scheme of this application embodiment, because electrode assembly follows the projection of the free direction of height of battery is the polygon, and the chamber that holds of casing is cylindric, consequently electrode assembly expands even after charging and discharging, still there is the headroom between the inner wall of electrode assembly and casing to avoid electrode assembly's outer peripheral face to receive the extrusion of casing, this headroom can allow electrode assembly to take place the inflation, prevent that pole piece excessive extrusion from appearing active material and dropping, electrolyte infiltration is difficult, pole piece performance deterioration such as pole piece fracture leads to the problem of the free performance decay of battery, and then alleviate the free performance decay of battery and influence the free cycle life's of battery problem.

In one embodiment of the present application, the projection of the electrode assembly is pentagonal, hexagonal, octagonal, decagonal, or hexadecagonal.

Compare in electrode subassembly's projection for triangle-shaped, will electrode subassembly the projection is pentagon, hexagon, octagon, decagon or hexadecimal, can realize keeping under the prerequisite that has sufficient surplus space between the inner wall of assurance electrode subassembly and casing, improves the free energy density of battery to compromise and improve battery monomer cycle life and energy density.

In one embodiment of the present application, any one of cross sections of the electrode assembly perpendicular to a height direction of the battery cell has a polygonal shape.

Along the free direction of height of battery, any high position of electrode subassembly all has the surplus space, and any high position of electrode subassembly can both release stress, further prevents that the pole piece from excessively extrudeing and causing local stress concentration, alleviates the battery performance and reduces the problem that influences the cycle life of battery.

In one embodiment of the present application, the three-dimensional shape of the electrode assembly is a prism.

Any cross section of the prism in the direction perpendicular to the height direction of the prism (i.e., perpendicular to the height direction of the battery cell) is the same, and the electrode assembly having the three-dimensional shape of the prism is more convenient to manufacture than the electrode assembly having a partial cross section of a different shape.

In one embodiment of the present application, the three-dimensional shape of the electrode assembly is a regular prism.

The projection of the electrode assembly in the regular prism shape is a regular polygon, and the area of the regular polygon occupies a larger area of the circumscribed circle than a non-regular polygon having the same diameter of the circumscribed circle, so that the energy density of the battery cell is relatively greater when the electrode assembly is projected as the regular polygon. In addition, when the three-dimensional shape of the electrode assembly is a regular prism, the stress parts of the electrode assembly are uniformly distributed on the periphery of the electrode assembly at the side edges of the regular prism, namely at the top point of the projection of the electrode assembly, so that the stress of the electrode assembly is more uniform, and the local stress concentration caused by excessive extrusion of the electrode assembly is relieved, thereby further preventing the cycle life of a battery monomer from being influenced by the performance attenuation of the battery.

In one embodiment of the present application, the projected adjacent sides of the electrode assembly smoothly transition between each other.

When the electrode assembly expands, the positions of the vertexes of the polygons are mainly abutted against the inner wall of the shell, two adjacent sides of the polygons are in smooth transition, the vertexes form a fillet structure to increase the stress area and reduce the local stress at the positions of the vertexes, and further the excessive stress caused by excessive extrusion at the vertexes is prevented, so that the performance attenuation of the battery is prevented from influencing the cycle life of the battery monomer.

In one embodiment of the present application, a ratio of the projected circumscribed circle diameter of the electrode assembly to the diameter of the receiving cavity is 90% to 100%.

The ratio of the diameter of the circumscribed circle of the polygon formed by the projection of the electrode assembly to the diameter of the accommodating cavity is the group margin of the battery cells. The smaller the group margin is, the larger the gap is, and the smaller the energy density of the battery monomer is, but the electrode assembly is relatively easy to shell at the moment; conversely, the larger the group margin, the smaller the gap, and the greater the energy density of the battery cell, but in this case, it is relatively difficult to case the electrode assembly. When the group margin is configured to be 90% to 100%, the battery cell has a greater energy density while providing a surplus space for expansion of the electrode assembly, and also facilitates housing of the electrode assembly.

In one embodiment of the present application, a ratio of the projected circumscribed circle diameter of the electrode assembly to the diameter of the receiving cavity is 95% to 100%.

According to the technical scheme, on the premise that the residual space for releasing the stress of the electrode assembly is ensured, the energy density is further improved.

In one embodiment of the present application, the electrode assembly includes a first pole piece and a second pole piece of opposite polarity to the first pole piece, the first pole piece and the second pole piece being wound to form the electrode assembly;

defining a connecting line between any vertex of the projection of the electrode assembly and the center of a circumscribed circle of the projection of the electrode assembly as a first straight line, wherein the projection of the edge of the winding end of the first pole piece along the height direction of the battery cell is not on any first straight line, and the projection of the edge of the winding end of the second pole piece along the height direction of the battery cell is not on any first straight line.

The edge of the winding ending end of the first pole piece and the edge of the winding ending end of the second pole piece are not on the first straight line, so that the diameter of the circumscribed circle is not increased when the first pole piece or the second pole piece is ended, the energy density is improved under the condition of not increasing the group margin, the distances from all vertexes to the inner wall of the shell are approximately equal, the phenomenon that the local stress is too large to cause the performance attenuation of the battery due to the excessive extrusion of the individual vertexes is avoided, and the cycle life of the battery is prolonged.

defining a connecting line between any vertex of the projection of the electrode assembly and the center of a circumscribed circle of the projection of the electrode assembly as a first straight line, wherein the projection of the winding start end edge of the first pole piece along the height direction of the battery cell is not on any first straight line, and the projection of the winding start end edge of the second pole piece along the height direction of the battery cell is not on any first straight line.

When the winding start end is on the first straight line, the end face of the winding start end can abut against the surface of the pole piece of the adjacent area, so that the end face of the winding start end is easy to rub, the coating layer (namely the active material layer) near the end face is easy to fall off, the cycle life of the battery can be influenced by the falling off, and the lithium precipitation phenomenon can be caused. The edge of the winding starting end of the first pole piece and the edge of the winding starting end of the second pole piece are not on the first straight line, so that the problem that the end face of the winding starting end of the pole piece rubs with the pole piece surfaces of adjacent areas to cause powder falling of a coating layer can be effectively solved, and the cycle life of a battery is prevented from being influenced.

defining a connecting line between any vertex of the projection of the electrode assembly and the center of a circumscribed circle of the projection of the electrode assembly as a first straight line, wherein the projection of the electrode assembly is divided into a plurality of areas by a plurality of first straight lines, and the difference between the number of pole piece layers in any two areas is less than or equal to 1.

The difference between the number of layers of the pole pieces in any two regions is smaller than or equal to 1, the number of layers of winding in each region is smaller in difference or consistent in number of layers of winding, and therefore the utilization rate of the inner space of the accommodating cavity can be improved, the effect of prolonging the cycle life of the battery is considered, and the effect of increasing the energy density is also considered.

In an embodiment of the present application, a projection of a winding start end edge of the first pole piece along a height direction of the battery cell and a projection of a winding end edge of the first pole piece along the height direction of the battery cell are located in two adjacent regions, and a projection of a winding start end edge of the second pole piece along the height direction of the battery cell and a projection of a winding end edge of the second pole piece along the height direction of the battery cell are located in two adjacent regions.

When the winding start end and the winding tail end of the first pole piece and the second pole piece are in two adjacent areas, the number of winding turns of the first pole piece and the second pole piece can be an integer, the number of pole piece layers in any two areas is equal, and therefore the utilization rate of the inner space of the containing cavity is improved. And the phenomenon that the clearance between the outer peripheral surface of a certain area and the inner wall of the shell is relatively small due to the fact that the number of winding layers of the area is too large can be avoided, so that local stress is too large due to excessive extrusion of individual vertexes during expansion, and the cycle life of the battery is prevented from being influenced.

In one embodiment of the present application, the battery cell further includes:

a tie layer for wrapping the electrode assembly, the tie layer having elasticity to allow the electrode assembly to expand.

The binding layer not only tightly wraps the electrode assembly to enable the electrode assembly to keep the projected shape of the electrode assembly, but also prevents the battery performance from being influenced by the increase of internal resistance due to the over-loose of the wound pole piece.

In one embodiment of the present application, the constraining layer is a sleeve, and the constraining layer is sleeved outside the electrode assembly.

The telescopic binding layer has good integrity, good binding effect and easy assembly.

In one embodiment of the present application, the tie layer has a gap with an inner wall of the housing.

The space is formed between the binding layer and the inner wall of the case, so that more space is left for the expansion of the electrode assembly.

In one embodiment of the present application, the constraining layer provided on the outside of the electrode assembly has the same three-dimensional shape as the electrode assembly.

The three-dimensional shape of the constraint layer is the same as that of the electrode assembly, namely the projection of the whole formed by the electrode assembly and the constraint layer along the height direction of the battery cell is a polygon, so that a residual space is ensured between the constraint layer and the inner wall of the shell, and the electrode assembly can further release stress.

In a second aspect, an embodiment of the present application provides a battery, which includes the foregoing battery cell.

The battery provided by the embodiment has the advantages that the problem of pole piece performance deterioration caused by expansion of the internal electrode assembly is not easy to occur to the battery cell, the battery has better durability and long service life.

In a third aspect, an embodiment of the present application provides an electric device, which includes the foregoing battery.

The battery used by the electric equipment provided by the embodiment has better durability and longer service life, so that the electric equipment works stably.

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

providing a shell, wherein the shell is provided with a cylindrical accommodating cavity;

providing an electrode assembly, wherein the projection of the electrode assembly along the height direction of the battery cell is polygonal;

disposing the electrode assembly within the receiving cavity.

In a fourth aspect, an embodiment of the present application provides a device for preparing a battery cell, including:

the first providing device is used for providing a shell, and the shell is provided with a cylindrical accommodating cavity;

a second providing device for providing an electrode assembly, wherein the projection of the electrode assembly along the height direction of the battery cell is a polygon;

an assembly device for disposing the electrode assembly within the receiving cavity.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.

FIG. 1 is a schematic illustration of a vehicle provided in accordance with an embodiment of the present application;

FIG. 2 is a schematic diagram of a battery provided in accordance with an embodiment of the present application;

fig. 3 is an exploded view of a battery module provided in one embodiment of the present application;

fig. 4 is a schematic diagram of a battery cell provided in an embodiment of the present application;

fig. 5 is a schematic view illustrating an assembly of a battery cell according to an embodiment of the present application;

FIG. 6 is a schematic diagram of an electrode assembly provided in one embodiment of the present application projected as a regular pentagon;

FIG. 7 is a schematic illustration of an expansion process of an electrode assembly provided in accordance with an embodiment of the present application;

FIG. 8 is a schematic three-dimensional shape of any of the electrode assemblies of the present application having the same cross-sectional shape but different sizes according to one embodiment of the present application;

FIG. 9 is a schematic three-dimensional shape view of an electrode assembly having a prismatic three-dimensional shape according to one embodiment of the present application;

FIG. 10 is a schematic view of an electrode assembly provided in accordance with one embodiment of the present application having a non-regular hexagonal projection;

FIG. 11 is a schematic view of an electrode assembly provided in accordance with one embodiment of the present application having a regular hexagonal projection;

FIG. 12 is a schematic view of an electrode assembly provided in one embodiment of the present application projected as a regular octagon;

FIG. 13 is a schematic diagram of an electrode assembly provided in accordance with one embodiment of the present application as a regular decagon in projection;

FIG. 14 is a plot of the present application as the area division of the electrode assembly when the projection is a regular hexagon;

FIG. 15 is a schematic winding of the first and second pole pieces provided by an embodiment of the present application;

FIG. 16 is a schematic view of another winding of the first and second pole pieces provided in accordance with an embodiment of the present application;

FIG. 17 is a schematic view of another winding of the first and second pole pieces provided in accordance with an embodiment of the present application;

FIG. 18 is a schematic view of yet another winding of the first and second pole pieces provided in accordance with an embodiment of the present application;

FIG. 19 is a schematic view of an end edge of a pole piece at a start of winding and an end edge of a pole piece at an end of winding not aligned with a first line according to one embodiment of the present application;

FIG. 20 is a graph comparing smooth and non-smooth transitions between two adjacent sides of a projection of an electrode assembly according to one embodiment of the present application;

FIG. 21 is an electrode assembly formed by co-winding a first pole piece, a second pole piece, a first separator, and a second separator as provided in one embodiment of the present application;

FIG. 22 is a schematic view of an overall projection of a constraining layer disposed on the outside of an electrode assembly according to an embodiment of the present application;

FIG. 23 is a schematic view of an overall projection of another constraining layer provided in accordance with an embodiment of the present application, nested on the outside of an electrode assembly;

fig. 24 is an exploded view of a battery cell provided in accordance with an embodiment of the present application;

fig. 25 is a schematic flow chart of a method of making a battery cell provided in one embodiment of the present application;

fig. 26 is a schematic block diagram of a device for preparing a battery cell according to an embodiment of the present application.

In the drawings, the drawings are not necessarily to scale.

Icon: 1-a vehicle; 2-a motor; 3-a controller; 4-a battery; 41-a battery module; 42-a box body; 43-first part; 44-a second portion; 45-battery cell; 100-a housing; 110-a containment chamber; 200-an end cap assembly; 210-electrode terminals; 220-liquid injection hole; 300-an electrode assembly; 310-a first pole piece; 311-the winding start of the first pole piece; 312 — winding trailing end of first pole piece; 320-a second pole piece; 321-the winding start end of the second pole piece; 322-winding and ending of the second pole piece; 330-a first membrane; 340-a second membrane; 400-a tie-down layer; 500-a preparation device; 510-a first providing device; 520-a second providing means; 530-assembling the device; h-height direction of the battery monomer; ci-circumscribed circle.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the description of the application in the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "including" and "having," and any variations thereof, in the description and claims of this application and the description of the above figures are intended to cover non-exclusive inclusions. The terms "first," "second," and the like in the description and claims of this application or in the above-described drawings are used for distinguishing between different elements and not for describing a particular sequential or chronological order.

Reference in the specification to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the specification. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.

In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "attached" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

The term "and/or" in this application is only one kind of association relationship describing the associated object, and means that there may be three kinds of relationships, for example, a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" in this application generally indicates that the former and latter related objects are in an "or" relationship.

In the embodiments of the present application, like reference numerals denote like parts, and a detailed description of the same parts is omitted in different embodiments for the sake of brevity. It should be understood that the thickness, length, width and other dimensions of the various components in the embodiments of the present application and the overall thickness, length, width and other dimensions of the integrated device shown in the drawings are only exemplary and should not constitute any limitation to the present application.

The "plurality" in the present application means two or more (including two), and similarly, "plural" means two or more (including two) and "plural" means two or more (including two).

In this application, the battery cell 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, a magnesium ion battery, or the like, and may also be a solid-state battery or a semi-solid-state battery, and the embodiment of the present application is not limited thereto.

Reference to a battery in embodiments of the present application refers to a single physical module that includes one or more battery cells to provide higher voltage and capacity. For example, the battery referred to in the present application may include a battery module or a battery pack, etc. Batteries generally include a case for enclosing one or more battery cells. The box can avoid liquid or other foreign matters to influence the charging or discharging of battery monomer.

The battery cell includes an electrode assembly and an electrolyte. When the electrolyte is a solid electrolyte, the electrode assembly consists of a positive electrode plate and a negative electrode plate; when the electrolyte is a liquid electrolyte (i.e., an electrolyte), the electrode assembly is composed of a positive electrode tab, a negative electrode tab, and a separator. The battery cell mainly depends on metal ions to move between the positive pole piece and the negative pole piece to work. The positive pole piece includes anodal mass flow body and anodal active substance layer, and anodal active substance layer coats in anodal mass flow body's surface, and the mass flow body protrusion on the anodal active substance layer of uncoated positive active substance layer is in the mass flow body of coating anodal active substance layer, and the mass flow body on the anodal active substance layer of uncoated positive is as anodal utmost point ear. Taking a lithium ion battery as an example, the material of the positive electrode current collector may be aluminum, and the positive electrode active material may be lithium cobaltate, lithium iron phosphate, ternary lithium, lithium manganate, or the like. The negative pole piece includes negative current collector and negative active material layer, and the negative active material layer coats in the surface of negative current collector, and the mass flow body protrusion in the mass flow body of coating the negative active material layer of uncoated negative active material layer, the mass flow body of uncoated negative active material layer is as negative pole utmost point ear. The material of the negative electrode current collector may be copper, and the negative electrode active material may be carbon, silicon, or the like. In order to ensure that the fuse is not fused when a large current is passed, the number of the positive electrode tabs is multiple and the positive electrode tabs are stacked together, and the number of the negative electrode tabs is multiple and the negative electrode tabs are stacked together. The material of the diaphragm can be PP or PE, etc. In addition, the electrode assembly may have a winding structure or a lamination structure, and the embodiment of the present application is not limited thereto. The development of battery technology needs to consider various design factors, such as energy density, cycle life, discharge capacity, charge and discharge rate, and other performance parameters, and also needs to consider the safety of the battery.

For cells, the main safety hazard comes from the charging and discharging processes, and at the same time, with a suitable ambient temperature design, there are generally at least three protective measures for the cells in order to effectively avoid unnecessary losses. In particular, the protective measures comprise at least a switching element, selection of a suitable isolating membrane material and a pressure relief mechanism. The switching element is an element that can stop charging or discharging the battery when the temperature or resistance in the battery cell reaches a certain threshold value. The isolating film is used for isolating the positive pole piece and the negative pole piece, and can automatically dissolve the micron-scale (even nano-scale) micropores attached to the isolating film when the temperature rises to a certain value, so that metal ions cannot pass through the isolating film, and the internal reaction of the battery monomer is stopped. The pressure relief mechanism refers to an element or a component that is actuated to relieve the internal pressure or temperature of the battery cell when the internal pressure or temperature reaches a predetermined threshold. The threshold design varies according to design requirements. The threshold may depend on the material of one or more of the positive electrode sheet, the negative electrode sheet, the electrolyte and the separator in the battery cell.

In the use process of the single battery, the performance of the single battery sometimes attenuates or suddenly drops, and the inventor researches and discovers that the main reason causing the performance of the single battery to be poor is that the wetting effect of electrolyte on a pole piece is poor after the single battery is used for a period of time, and the poorer the wetting effect of the electrolyte on the pole piece is, the greater the performance attenuation of the single battery is, and the cycle life of the single battery is seriously influenced. However, the inventors have tried to improve the electrolyte wetting agent and the winding process of the electrode sheet, and the like, and the problem is not solved yet. The inventor further researches and discovers that the main reason of the poor infiltration effect of the pole piece is caused by the locking of the electrode component against the inner wall of the shell of the battery cell. The term "lock" in this embodiment means that the entire outer peripheral surface of the electrode assembly abuts against the inner wall of the case, and the electrode assembly cannot release stress.

Because the electrode assembly may slowly expand in the use process, after the outer peripheral surface of the electrode assembly is completely abutted to the inner wall of the shell, if the electrode assembly further expands, the pole piece is extruded, the porosity of the pole piece is reduced when the pole piece is excessively extruded, the amount of electrolyte absorbed by the pole piece is reduced, the infiltration effect of the electrolyte on the pole piece is poor, and once the pole piece is excessively extruded, the pole piece is permanently damaged, the extruded electrolyte cannot be completely absorbed again even if the compressive stress disappears, so that the performance of the battery cell is attenuated or suddenly reduced, and the cycle life of the battery cell is reduced.

In addition, the pole piece is excessively extruded, so that material particles of the pole piece are broken, at the moment, a film is formed on the surface of the material particles again, and at the moment, side reaction is accompanied, so that the attenuation is accelerated, therefore, no matter the battery monomer adopts the electrolyte or the solid electrolyte, the problem of performance attenuation is easy to occur when the pole piece is excessively extruded, and the cycle life of the battery monomer is influenced.

In view of this, in order to solve the problem of the reduction of the cycle life of the battery, the embodiments of the present application provide a technical solution, a cylindrical accommodation cavity is disposed in a housing of the battery cell, the accommodation cavity is used for accommodating an electrode assembly, and a projection of the electrode assembly along a height direction of the battery cell is a polygon. When the electrode assembly expands due to charging and discharging in the using process, the vertex position of the polygon is abutted against the inner wall of the shell, and a remaining space is left between the side of the polygon and the inner wall of the shell, so that the outer peripheral surface of the electrode assembly is prevented from being completely abutted against the inner wall of the shell and locked. This remaining space allows electrode assembly release stress in order to avoid the pole piece to be excessively extruded, avoids appearing the microcosmic damage that pole piece material granule breaks or the porosity reduces, and avoids the cracked macroscopic damage of pole piece to solve the problem that pole piece performance worsens and lead to the decay of battery monomer performance, and then solve the problem that the decay of battery monomer performance leads to the reduction of battery monomer's cycle life.

The technical scheme described in the embodiment of the application is applicable to various electric equipment using batteries, such as mobile phones, portable equipment, notebook computers, battery cars, electric toys, electric tools, electric vehicles, ships, spacecrafts and the like, and the spacecrafts comprise airplanes, rockets, space shuttles, spacecrafts and the like.

It should be understood that the technical solutions described in the embodiments of the present application are not limited to be applied to the above-described electric devices, but may also be applied to all electric devices using batteries, and for brevity of description, the following embodiments are all described by taking an electric vehicle as an example.

For example, as shown in fig. 1, in a vehicle 1 according to an embodiment of the present disclosure, the vehicle 1 may be a fuel automobile, a gas automobile, or a new energy automobile, and the new energy automobile may be a pure electric automobile, a hybrid electric automobile, or an extended range automobile. The vehicle 1 may be provided with a motor 2, a controller 3 and a battery 4, the controller 3 being configured to control the battery 4 to supply power to the motor 2. For example, the battery 4 may be provided at the bottom or the head or tail of the vehicle 1. The battery 4 may be used for power supply of the vehicle 1, for example, the battery 4 may be used as an operation power supply of the vehicle 1 for a circuit system of the vehicle 1, for example, for power demand for operation in starting, navigation, and running of the vehicle 1. In another embodiment of the present application, the battery 4 may be used not only as an operation power source of the vehicle 1 but also as a driving power source of the vehicle 1, instead of or in part replacing fuel or natural gas to provide driving power for the vehicle 1.

In order to meet different power requirements, the battery 4 may include a plurality of battery cells, wherein the plurality of battery cells may be connected in series or in parallel or in series-parallel, and the series-parallel refers to a mixture of series connection and parallel connection. The battery 4 may also be referred to as a battery pack. Alternatively, as shown in fig. 2 and fig. 3, a plurality of battery cells 45 may be connected in series or in parallel or in series-parallel to form a battery module 41, and a plurality of battery modules 41 may be connected in series or in parallel or in series-parallel to form a battery 4. That is, the plurality of battery cells 45 may be directly assembled into the battery 4, or the battery module 41 may be assembled first, and then the battery module 41 may be assembled into the battery 4.

The battery 4 may include a plurality of battery cells 45; the battery 4 may further include a case 42 (or a cover), the case 42 has a hollow structure, and the plurality of battery cells 45 are accommodated in the case 42. The housing 42 may comprise two parts, referred to herein as a first part 43 and a second part 44, respectively, the first part 43 and the second part 44 being snap-fitted together. The shape of the first and

second portions

43 and 44 may be determined according to the shape of a combination of a plurality of battery cells 45, and the first and

second portions

43 and 44 may each have one opening. For example, each of the first portion 43 and the second portion 44 may be a hollow rectangular parallelepiped and only one surface of each may be an opening surface, the opening of the first portion 43 and the opening of the second portion 44 are oppositely disposed, and the first portion 43 and the second portion 44 are fastened to each other to form the box body 42 having a closed chamber. One of the first portion 43 and the second portion 44 may be a rectangular parallelepiped having an opening, and the other may be a cover plate structure to close the opening of the rectangular parallelepiped. A plurality of battery cells 45 are connected in parallel or in series-parallel combination and then placed in the box 42 formed by buckling the first part 43 and the second part 44.

Alternatively, the battery 4 may also comprise other structures. For example, the battery 4 may further include a bus member for electrically connecting the plurality of battery cells 45, such as in parallel or in series-parallel. Specifically, the bus member may achieve electrical connection between the battery cells 45 by connecting electrode terminals of the battery cells 45. Further, the bus bar member may be fixed to the electrode terminals of the battery cells 45 by welding. The electric energy of the plurality of battery cells 45 can be further led out through the case 42 by the conductive mechanism. Alternatively, the conductive means may also belong to the bus bar member.

As will be described in detail below with respect to any one of the battery cells 45, fig. 4 and 5 illustrate one of the battery cells 45 according to one embodiment of the present disclosure, the battery cell 45 including a housing 100, an end cap assembly 200, and one or more electrode assemblies 300.

The case 100 may be a rectangular parallelepiped, or a square or a cylinder, the case 100 is hollow and has a cylindrical receiving chamber 110, and one of the faces of the case 100 has an opening so that one or more electrode assemblies 300 can be placed in the receiving chamber 110. For example, an end surface of the case 100 is a plane having an opening, that is, the end surface is configured without a wall such that the receiving chamber 110 communicates with the outside of the case 100. The cap assembly 200 covers the opening and is connected to the case 100 to close the receiving chamber 110, and the electrolyte is filled into the receiving chamber 110 through the injection hole 220 of the cap assembly 200.

The battery cell 45 further includes one or more electrode terminals 210, and the electrode terminals 210 are disposed on the end cap assembly 200. A connecting member, which may also be referred to as an adaptor (not shown), is connected to the electrode terminal 210 between the cap assembly 200 and the electrode assembly 300 for electrically connecting the electrode assembly 300 and the electrode terminal 210.

Each electrode assembly 300 has a first pole piece and a second pole piece, the first pole piece and the second pole piece being of opposite polarity. For example, when the first pole piece is a positive pole piece, the second pole piece is a negative pole piece. The tabs of the first pole piece of one or more electrode assemblies 300 are connected to an electrode terminal 210, e.g., a positive electrode terminal, via an adaptor; the tab of the second pole piece of one or more electrode assemblies 300 is connected to another electrode terminal 210, e.g., a negative electrode terminal, via another adapter. That is, the positive electrode terminal is connected to the tab of the positive electrode tab through one adapter, and the negative electrode terminal is connected to the tab of the negative electrode tab through the other adapter.

In the battery cell 45, one or more electrode assemblies 300 may be disposed according to actual use requirements, and as shown in fig. 5, one electrode assembly 300 is disposed in the accommodating cavity 110 of the battery cell 45.

The accommodating cavity 110 is configured to be cylindrical, a schematic projection diagram of the battery cell 45 along the height direction of the battery cell is illustrated by a regular pentagon in fig. 6, wherein a projection of the electrode assembly 300 and a projection of the accommodating cavity 110 can be seen, the projection of the accommodating cavity 110 along the height direction of the battery cell is circular, and the projection of the electrode assembly 300 along the height direction of the battery cell is polygonal.

All projections in this embodiment are "projections along the height direction of the battery cell", and are hereinafter referred to as projections for short. In addition, the projection of the electrode assembly in the drawings of the present application shows only the outline of the projection as a line to represent the shape of the projection, and does not represent that the electrode assembly must have a hollow structure.

After the electrode assembly 300 is enclosed in the accommodating cavity 110, the electrode assembly 300 expands during charging and discharging, fig. 7 illustrates the expansion process of the electrode assembly 300 by taking a projection of a regular pentagon as an example, and a dotted line in fig. 7 is a projection of the expanded electrode assembly 300. As the electrode assembly 300 is expanded, the vertex of the regular pentagon is gradually close to the inner wall of the case 100, and after the electrode assembly 300 is expanded until the vertex abuts against the inner wall of the case 100, a gap is still formed between the sides of the regular pentagon and the inner wall of the case 100, so that the electrode assembly 300 still has a space for releasing stress. When the electrode assembly continues to expand, the edges of the regular pentagon expand and bulge towards the inner wall of the shell 100 to deform, so that the expansion force of the pole pieces of the electrode assembly is fully released, the outer periphery of the electrode assembly 300 is prevented from being locked by the inner wall of the shell 100, and the pole pieces cannot be excessively extruded even if the electrode assembly 300 continues to expand.

In some embodiments, any one of the cross-sections of the electrode assembly 300 perpendicular to the height direction of the battery cell has a polygonal shape. That is, at any height position of the electrode assembly 300, a remaining space is formed between the outer circumferential surface of the electrode assembly 300 and the inner wall of the case 100, so that stress at any height position of the electrode assembly 300 can be released, thereby further preventing local stress concentration caused by excessive compression of the pole pieces and alleviating the problem that the cycle life of the battery is affected by the performance reduction of the battery.

In some embodiments, any portion of the cross-section may be different. For example, fig. 8 shows an electrode assembly 300 in which any cross-sectional shape of the electrode assembly 300 is hexagonal in the height direction H of a battery cell, but a part of the cross-section is relatively large and a part of the cross-section is relatively small. In other embodiments, any cross section along the height direction H of the battery cell may have a different shape, for example, the cross section of the electrode assembly at some heights may be quadrangular, the cross section at other heights may be pentagonal, and the like.

In some embodiments, for convenience of manufacturing, as shown in fig. 9, any cross-section of the electrode assembly 300 perpendicular to the height direction H of the battery cell has a polygonal shape with the same size, that is, the three-dimensional shape of the electrode assembly 300 is a prism. Along the height direction H of the battery monomer, the projection of the prism is the same as the section of any height position of the prism, and the prism is a polygon with the same shape and size.

The polygon in this embodiment is a planar figure formed by sequentially connecting three or more line segments end to end, and the number of sides of the polygon in this application is not limited, and may be a quadrangle, a hexagon, an octagon, a decagon, a hexadecgon, or the like.

The shape of the polygon may be a regular polygon or a non-regular polygon. For example, fig. 10 shows a battery cell 45 having a projection of the electrode assembly 300 that is not a regular hexagon.

In some embodiments, the projection of the electrode assembly 300 is a regular polygon. For example, fig. 11 shows a battery cell 45 in which the projection of the electrode assembly 300 is a regular hexagon.

When the regular polygon is expanded until each vertex abuts against the inner wall of the housing 100, the inner wall of the housing 100 exerts a reaction force on the polygon, and the acting portion of the reaction force is positioned at the vertex of the polygon. Because each vertex interval of regular polygon is even for the stress position of the electrode assembly 300 projected as regular polygon is evenly distributed on the periphery, so that the stress of the electrode assembly 300 is relatively even, the electrode assembly 300 can be prevented from excessively extruding the pole piece due to uneven stress and local stress concentration, the performance attenuation of the battery is further prevented, and the cycle life of the battery is prolonged.

Because the electrode assembly 300 is not easy to generate the condition of local stress concentration, and a residual space is still arranged between the electrode assembly 300 and the inner wall of the shell 100 to release internal stress, not only can the microscopic damage of porosity reduction or material particle fracture caused by excessive extrusion of the pole pieces of the electrode assembly 300 be prevented, but also the macroscopic damage of breakage and fracture of the pole pieces caused by excessive internal stress is not easy to generate.

Also, in the case where the circumscribed circles Ci have the same diameter, the area of the regular polygon is larger than the area of the non-regular polygon having the same number of sides, which results in a larger energy density of the battery cell.

In some embodiments, the projection of the electrode assembly 300 may be configured as a regular polygon of other number of sides, such as a regular octagon as shown in fig. 12, a regular decagon as shown in fig. 13, or a regular hexadecagon, in addition to being configured as a regular pentagon or a regular hexagon as previously described.

When the diameters of the circumscribed circles Ci are the same, the larger the number of sides of the regular polygon, the larger the area of the regular polygon, and increasing the number of sides of the regular polygon can effectively increase the energy density while ensuring that there is a sufficient remaining space between the electrode assembly and the inner wall of the case 100.

In the art, the energy density of a battery cell is often characterized by a group margin, as in the prior art cylindrical electrode assemblies, which is the ratio of the diameter of the cylindrical electrode assembly to the diameter of the cylindrical receiving cavity. In the present embodiment, the ratio of the diameter of the circumscribed circle Ci of the polygon formed by the projection of the electrode assembly 300 to the diameter of the receiving cavity 110 is defined as a cluster margin, and the larger the cluster margin is, the larger the energy density is.

In some embodiments, the group margin of the battery cell 45 is configured to be 90% to 100%, that is, the ratio of the diameter of the circumscribed circle Ci of the projection of the electrode assembly 300 to the diameter of the accommodating cavity 110 is 90% to 100%, so as to maximize the accommodating volume of the accommodating cavity 110, and provide a remaining space for the expansion of the pole piece, thereby avoiding the excessive stress inside the electrode assembly 300 caused by the locking of the electrode assembly 300 by the inner wall of the casing 100, preventing the pole piece from being deteriorated due to the dropping of active materials, the difficulty in soaking of electrolyte, the breaking of the pole piece and the like caused by the excessive squeezing of the pole piece, and further preventing the performance degradation of the battery cell from reducing the cycle life.

In other embodiments, the group margin of the battery cells 45 is configured to be 95% to 100%, that is, the ratio of the diameter of the circumscribed circle Ci of the projection of the electrode assembly 300 to the diameter of the receiving cavity 110 is 95% to 100%, so as to improve the energy density while ensuring that there is a remaining space for releasing the stress of the electrode assembly 300.

The group margin value referred to herein is a state in which the battery cell 45 is charged and discharged at a constant voltage to be activated. At this time, the electrode assembly 300 may have been expanded, even though the apex of the electrode assembly 300 is abutted against the inner wall of the case 100 and the group margin reaches 100%, because a remaining space still exists between the electrode assembly 300 and the inner wall of the case 100, the electrode assembly 300 is not easily locked, the pole pieces are not excessively pressed and damaged, the electrolyte is not easily extruded, the battery cell 45 can maintain a low internal resistance, and the condition of performance attenuation or sudden drop is not easily generated, thereby having a long cycle life.

As previously described, electrode assembly 300 in this embodiment includes first pole piece 310 and second pole piece 320. Electrode assembly 300 may be formed from a stack of materials including first and

second pole pieces

310 and 320, or may be formed by winding a stack of materials including first and

second pole pieces

310 and 320.

Here, the electrode assembly 300 is formed by winding the first pole piece 310 and the second pole piece 320, and the projection shape of the electrode assembly 300 is first set, for example, the electrode assembly 300 is set to be a prism, and the projection is a regular hexagon.

As shown in fig. 14, in order to facilitate description of the winding structure of the electrode assembly 300, a region division diagram when projected as a regular hexagon having A, B, C, D, E, F vertices is given in fig. 14, and a line defining the vertices of the projection of the electrode assembly 300 and a center O of a circumscribed circle of the projection of the electrode assembly 300 is a first line, i.e., the regular hexagon includes six first lines: AO, BO, CO, DO, EO, FO, six first straight lines divide the regular hexagon into six areas I, II, III, IV, V, VI, wherein area I is triangle AOB, area II is triangle BOC, area III is triangle COD, area IV is triangle DOE, area V is triangle EOF, area VI is triangle FOA. The first line and the area described below will be referred to herein.

Fig. 15 shows the projection of the first pole piece 310 and the second pole piece 320, in this embodiment, the first pole piece 310 is a positive pole piece, and the second pole piece 320 is a negative pole piece.

First pole piece 310 originates from one of the six regions and is wound in a clockwise or counterclockwise direction, and second pole piece 320 originates from one of the six regions and is wound in a clockwise or counterclockwise direction. Generally, first pole piece 310 and second pole piece 320 are stacked and then wound, and the winding directions of first pole piece 310 and second pole piece 320 are the same.

In the following description, the inner side is close to the center O of the circumscribed circle and the outer side is far from the center O of the circumscribed circle. For example, in fig. 15, first pole piece 310 and second pole piece 320 both start from region I and are wound from the inside to the outside in a counterclockwise direction.

In fig. 15, the winding start end 311 of the first pole piece is in the region I, and the winding end 312 of the first pole piece is in the region VI adjacent to the region I; the winding start end 321 of the second pole piece is in the region I, and the winding end 322 of the second pole piece is in the region VI adjacent to the region I. At this time, the number of winding turns of the first pole piece 310 is an integer, and the number of winding turns of the second pole piece 320 is also an integer. In other words, the number of times that the first pole piece 310 passes through the region I, the region II, the region III, the region IV, the region V, and the region VI is equal, and the number of layers of the first pole piece 310 stacked in each region is the same, and is two; similarly, the number of times that the second pole piece 320 passes through the region I, the region II, the region III, the region IV, the region V, and the region VI is equal, and the number of layers stacked in each region of the second pole piece 320 is the same, and is three. At the moment, the number of the pole piece layers in each area is equal and is five, and the difference of the number of the pole piece layers in any two areas is 0.

In fig. 15, the winding start end 311 of the first pole piece and the winding end 312 of the first pole piece are in adjacent regions, and the winding start end 321 of the second pole piece and the winding end 322 of the second pole piece are in adjacent regions, but the number of windings of the first pole piece 310 and the second pole piece 320 is different. The number of winding turns of the second pole piece 320 as the negative pole piece is greater than the number of winding turns of the first pole piece 310 as the positive pole piece, so that the innermost circle layer and the outermost circle layer of the electrode assembly 300 are both the second pole piece 320, it is ensured that the inner side surface and the outer side surface of the first pole piece 310 are both corresponding to the second pole piece 320 all the time, lithium ions can be embedded into the second pole piece 320 after being de-embedded from any one of the two surfaces of the first pole piece 310, and lithium precipitation due to insufficient allowance of the second pole piece 320 is effectively prevented.

In other embodiments, the number of windings of first pole piece 310 and second pole piece 320 may be the same. As shown in fig. 16, fig. 16 shows the projection of the first pole piece 310 and the second pole piece 320, the winding start end 311 of the first pole piece is in the region I, the winding end 312 of the first pole piece is in the region VI, the winding start end 321 of the second pole piece is in the region I, and the winding end 322 of the second pole piece is in the region VI, that is, the winding start end 311 of the first pole piece and the winding end 312 of the first pole piece are in adjacent regions, the winding start end 321 of the second pole piece and the winding end 322 of the second pole piece are in adjacent regions, and the number of winding turns of the first pole piece 310 and the second pole piece 320 are set to be the same, the number of layers of the first pole piece 310 and the second pole piece 320 overlapped in each region is two, and the number of pole pieces in each region is four. The innermost layer of the electrode assembly 300 is the second pole piece 320, the outermost layer is the first pole piece 310, in order to prevent lithium precipitation, at least the part of the outer side surface of the first pole piece 310 not covered by the second pole piece 320 is not coated with a coating layer, i.e. no active material is coated, and the edge of the winding end 322 of the second pole piece exceeds the edge of the winding end 312 of the first pole piece, so as to prevent the margin of the second pole piece 320 from being insufficient.

Each pole piece has two surfaces, and during winding, one of the two surfaces always faces the direction of the center O of the circumscribed circle, the other faces the direction of the inner wall of the casing 100, the surface facing the center O of the circumscribed circle is an inner side surface, and the surface facing the direction of the inner wall of the casing 100 is an outer side surface.

In other embodiments, there may be other winding patterns to make the difference in the number of pole pieces in any two regions 0.

For example, as shown in fig. 17, fig. 17 shows the projection of the first pole piece 310 and the second pole piece 320, the winding start end 311 of the first pole piece is in the region II, the winding end 312 of the first pole piece is in the region VI, the winding start end 321 of the second pole piece is in the region I, and the winding end 322 of the second pole piece is also in the region I, and it can be seen from fig. 17 that the number of pole piece layers in each region is equal, and all of them are five.

The number of pole pieces in a certain area is the sum of the number of first pole pieces 310 in the area and the number of second pole pieces 320 in the area. When first pole piece 310 reaches or passes through an area once, first pole piece 310 is overlapped by one layer in the area, and the number of layers of first pole piece 310 in the area is increased by one; similarly, each time the second pole piece 320 reaches or passes through an area, the second pole piece 320 is overlapped by one layer in the area, and the number of layers of the second pole piece 320 in the area is increased by one.

When the number of the pole pieces in each region is 0, the number of the pole pieces stacked in each region is the same, so that the distance between each vertex and the inner wall of the shell 100 is approximately equal, and the reaction force exerted on each vertex when the electrode assembly 300 expands is similar, so that the phenomenon that a certain vertex is relatively too close to the inner wall of the shell 100 to cause overlarge stress is avoided, and the phenomenon that the stress concentration of the vertex causes the overvoltage or breakage of the pole piece is avoided.

When the projection of the electrode assembly 300 is set to be a regular polygon, the electrode assembly 300, which is wound and formed, is relatively closer to the set regular polygon when the number of pole pieces in each region is the same, so that the utilization rate of the inner space of the receiving cavity 110 can be improved, and the energy density of the battery cell 45 can be increased.

In order to prevent the lithium separation phenomenon, after the first pole piece 310 is terminated, the second pole piece 320 is continuously wound to have enough negative pole piece margin, so as to prevent ions from being separated out from the first pole piece 310 and then being unable to be inserted into the second pole piece 320, and at this time, the difference between the number of pole piece layers in any two regions may not be 0. In other embodiments, the difference between the number of pole pieces in any two regions can be set to 1, for both the purpose of preventing the stress from being excessively concentrated and the purpose of ensuring the utilization rate of the internal space. For example, in fig. 18, fig. 18 shows the projection of the first pole piece 310 and the second pole piece 320, the winding start end 311 of the first pole piece and the winding start end 321 of the second pole piece are both in the region I, the winding end 312 of the first pole piece is in the region VI adjacent to the region I, and the winding end 322 of the second pole piece continues to wind to the region I after passing through the region VI and stops, at this time, the number of pole piece layers in the region I is one more than that in the other regions.

In other embodiments, there may be other winding forms so that the difference between the number of pole piece layers in any two regions is 0 or 1, and the region where the winding start end 311 of the first pole piece is located, the region where the winding start end 321 of the second pole piece is located, the region where the winding end 312 of the first pole piece is located, and the region where the winding end 322 of the second pole piece is located may be the same, may be different, or may be partially the same.

In some embodiments, the winding end 312 edge of the first pole piece is not on any first straight line and the winding end 322 edge of the second pole piece is not on any first straight line.

As shown in fig. 19, fig. 19 shows a projection of the first pole piece 310 and the second pole piece 320, and the edge of the winding trailing end 312 of the first pole piece and the edge of the winding trailing end 322 of the second pole piece are both in the region VI but not on the first straight line AO.

Since the first straight line increases the length of the thickness of one pole piece each time the first pole piece 310 or the second pole piece 320 reaches or passes through the first straight line when being wound, the projection of the electrode assembly 300 and the diameter of the circumscribed circle Ci thereof are correspondingly increased. Therefore, compared with the case that the edge of the winding ending end 312 of the first pole piece and the edge of the winding ending end 322 of the second pole piece are both on the first straight line AO, when the edge of the winding ending end 312 of the first pole piece and the edge of the winding ending end 322 of the second pole piece are not on the first straight line AO, the number of pole piece layers in each region is not changed (nine layers are still formed), the energy density is reduced less or even basically the same, but the distance from the vertex a to the inner wall of the casing 100 is relatively reduced, so that the diameter of the circumscribed circle Ci is relatively reduced, which is equivalent to improving the energy density without increasing the group margin, and further considering the purpose of facilitating assembly and the purpose of improving the energy density.

Under the condition that the difference between the pole piece layers of any two areas is 0, the edge of the winding ending end 312 of the first pole piece and the edge of the winding ending end 322 of the second pole piece are not on the first straight line, and the effect of ensuring that the distances from all the vertexes to the inner wall of the shell 100 are approximately equal is achieved. Taking fig. 19 as an example, since the number of layers is not increased at the vertex a at the time of ending, nine pole pieces are provided on each of the first straight line AO, the first straight line BO, the first straight line CO, the first straight line DO, the first straight line EO, and the first straight line FO, and the distances from the vertex a, the vertex B, the vertex C, the vertex D, the vertex E, and the vertex F to the inner wall of the case 100 are further ensured to be substantially equal, so that the reaction forces received at the vertex a, the vertex B, the vertex C, the vertex D, the vertex E, and the vertex F are ensured to be equal when the outer peripheral surface of the electrode assembly 300 abuts against the inner wall of the case 100, and damage due to excessive local stress at one vertex is.

In some embodiments, the winding start 311 edge of the first pole piece is not on any first straight line, and the winding start 321 edge of the second pole piece is not on any first straight line.

When the edge of the winding start end is on the first straight line, the end face of the winding start end can abut against the surface of the pole piece of the adjacent area, which causes the end face of the winding start end to be easily rubbed to cause powder falling of the coating layer near the end face or powder falling of the surface of the pole piece abutted by the end face. Taking fig. 19 as an example, in fig. 19, the distance between the pole pieces is enlarged for easy viewing, and the actual distance between the pole pieces is very small, since the winding start edge of the first pole piece 310 is on the first straight line AO, the end surface of the winding start end of the first pole piece 310 will contact the surface of the innermost second pole piece 320 in the region VI, and the end surface of the winding start end 311 of the first pole piece is easily rubbed to cause the coating layer near the contact part to fall off; similarly, assuming that the winding start edge of the second pole piece 320 is on the first straight line AO, the end face of the winding start end of the second pole piece 320 will contact the surface of the innermost second pole piece 320 in the region VI, and the end face of the winding start end 321 of the second pole piece is easily rubbed to cause the coating layer near the contact portion to fall off.

As shown in fig. 21, by making neither the edge of the winding start end 311 of the first pole piece nor the edge of the winding start end 321 of the second pole piece on the first straight line AO, neither the end surface of the winding start end 311 of the first pole piece nor the end surface of the winding start end 321 of the second pole piece abuts against the surface of the innermost second pole piece 320 in the region VI, and the coating layer near the end surface of the winding start end is not caused to fall off. The coating layer on the pole piece is generally an active material layer, and the coating layer powder falling can lead to the appearance of lithium precipitation and influence the cycle life of the battery monomer 45, so that the edge of the winding starting end 311 of the first pole piece and the edge of the winding starting end 321 of the second pole piece are not on the first straight line AO, the lithium precipitation can be prevented, and the cycle life of the battery monomer 45 can be effectively prolonged.

In some embodiments, the edge of the winding start end 311 of the first pole piece, the edge of the winding start end 321 of the second pole piece, the edge of the winding tail end 312 of the first pole piece, and the edge of the winding tail end 322 of the second pole piece are not on the same diameter of the circumscribed circle Ci, so that local stress concentration caused by overlapping of steps at a local position is avoided, and meanwhile, the thickness at the overlapping position of the steps is prevented from being larger than that at other positions, so that an internal space is better utilized, and the utilization rate of the internal space is improved to improve energy density.

In some embodiments, electrode assembly 300 is provided with a spool. Here, the winding drum is a polygonal cylinder disposed at the axial center of the electrode assembly 300 for facilitating the winding of the electrode assembly 300, the number of sides or the number of sides of the polygonal cylinder is the same as the number of sides of the set polygon, and the first pole piece 310 and the second pole piece 320 are wound around the winding drum to form the electrode assembly 300 having the same projection shape and the set polygon size.

When the electrode assembly 300 is coaxially provided with a winding drum for assisting winding, the winding start end edge of the pole piece has no play margin slightly deformed inward, and the length of the first straight line is also increased if the winding start end edge of the pole piece is on the first straight line. Therefore, in this case, the edge of the winding start end is not on the first straight line, and the length of the first straight line is not increased, so that the diameter of the circumscribed circle Ci is not increased, and the energy density is further improved without increasing the group margin; in some cases, it also has the effect of ensuring that the distances from each vertex to the inner wall of the casing 100 are substantially equal, so that the reaction forces experienced at each vertex are equal, and thus the pole piece is not overpressured due to excessive local stress at a certain vertex.

To further alleviate the problem of stress concentration at the apex, in some embodiments, the projected adjacent sides of the electrode assembly 300 transition smoothly between each other.

Smooth transition between two adjacent sides makes the vertex of the polygon be a fillet, forming an arc surface, and the contact area between the arc surface and the inner wall of the cylindrical case 100 is larger, as shown in fig. 20, fig. 20 shows a projection schematic diagram of the electrode assembly 300 when expanding by taking a regular hexagon as an example, the dotted line in fig. 20 is the projection of the expanded electrode assembly 300, the vertex a in fig. 20 is in non-smooth transition, and the vertices B, C, D, E, and F are in smooth transition, as can be seen by comparison: when the electrode assembly 300 expands to abut against the inner wall of the casing 100, the arc surface formed at the smooth transition position is basically in full contact with the inner wall of the cylindrical casing 100, in other words, the contact areas at the vertexes B, C, D, E and F are all larger than the contact area at the vertex a, so that the stress area at the vertexes of the smooth transition is increased to reduce the internal force in unit area, i.e., reduce stress, thereby alleviating the problem of local stress concentration, further preventing the pole piece from being excessively extruded, alleviating the performance attenuation of the battery cell caused by the excessively extruded pole piece, and further prolonging the cycle life of the battery cell.

During winding, as shown in fig. 21, fig. 21 shows the projection of first pole piece 310 and second pole piece 320, first pole piece 310 and second pole piece 320 are turned at a first straight line to change the winding direction, where changing the winding direction means that first pole piece 310 or second pole piece 320 turns to another side of the polygon along one side of the polygon, and first pole piece 310 and second pole piece 320 form a rounded corner at each turning so that each vertex is a circular arc surface. When the electrode assembly 300 is formed by processing the pole pieces in a manner other than winding, for example, stacking, the adjacent two sides of the projection of the electrode assembly 300 may be smoothly transited by other means such as hot pressing.

During the actual molding of the electrode assembly 300, the electrode assembly 300 may not be a complete regular polygon due to process fluctuations. The vertex angle of the polygon has a manufacturing tolerance of +/-10%, and when the vertex angle forms a fillet: phi is more than or equal to 0.9 (180-360 degrees/n) and less than or equal to 1.10 (180-360 degrees/n), wherein phi is the included angle of the extension lines of two adjacent sides of the polygon, and n is the number of the sides of the polygon.

When the electrolyte of the battery cell 45 is an electrolyte, an electronic insulating layer is further disposed between the first pole piece 310 and the second pole piece 320, and the electronic insulating layer may be a separator.

As shown in fig. 21, the lengths of the first and

second diaphragms

330 and 340 are respectively greater than the lengths of the first and

second pole pieces

310 and 320, the second diaphragm 340, the second pole piece 320, the first diaphragm 330, and the first pole piece 310 are sequentially stacked and then start to be wound, the edge of the winding start end 311 of the first pole piece after stacking exceeds the edge of the winding start end 321 of the second pole piece, and the edge of the winding start end of the first diaphragm 330 and the edge of the winding start end of the second diaphragm 340 respectively exceed the edge of the winding start end 311 of the first pole piece.

After winding, the second pole piece 320 is at the innermost turn layer and at least the second separator 340 covers the innermost turn layer. The inner side of first pole piece 310 and the outer side of second pole piece 320 are separated by a first membrane 330 and the outer side of first pole piece 310 and the inner side of second pole piece 320 are separated by a second membrane 340.

After the winding of first and

second pole pieces

310 and 320 is terminated, first and

second diaphragms

330 and 340 continue to be wound to cover winding

terminations

312 and 322 of the first and second pole pieces.

The more the number of turns of the diaphragm wound around the periphery of the electrode assembly 300, the better the binding performance of the electrode assembly 300, and the increase of internal resistance caused by the loosening of the pole pieces is prevented, so that the reduction of the battery performance caused by the increase of the internal resistance is avoided, and the cycle life of the battery is ensured. To better grip the electrode assembly 300 to prevent the first and

second pole pieces

310 and 320 from loosening and becoming too spaced apart, at least one of the first and

second separators

330 and 340 continues to be wound 0.25 to 5 turns after covering the winding trailing end 312 of the first pole piece and the winding trailing end 322 of the second pole piece.

However, the greater number of windings of the separator occupies space between the electrode assembly 300 and the inner wall of the case 100, and in order to achieve both the wrapping effect and the space occupation, in some embodiments, at least one of the first separator 330 and the second separator 340 is wound for 1.25 to 2 windings after covering the winding end 312 of the first pole piece and the winding end 322 of the second pole piece.

To further wrap the electrode assembly 300 to avoid poor interfaces while avoiding space usage due to a large number of membrane windings, in some embodiments, as shown in fig. 22, fig. 22 shows a projected view of the electrode assembly 300 with a tie layer 400 on the outside of the wound electrode assembly 300. Tie layer 400 serves to wrap electrode assembly 300 to prevent first and

second pole pieces

310 and 320 from being loosened and deformed due to the loosening, so that electrode assembly 300 maintains its set polygonal shape. Also, the constraining layer 400 has elasticity to allow the electrode assembly 300 to expand, i.e., as the electrode assembly 300 expands outward, the constraining layer 400 expands outward simultaneously, preventing the constraining layer 400 from pressing the pole pieces excessively while preventing the pole pieces from loosening.

The thickness of the tie layer 400 is exaggerated in the drawings of the present application for the convenience of observation, which is merely schematic and does not represent the actual thickness of the tie layer 400 nor the size ratio of the projection of the tie layer 400 to the projection of the electrode assembly 300.

In some embodiments, the elastic constraining layer 400 can be made of a condensation polymer of terephthalic acid and ethylene glycol, or a pressure sensitive adhesive with a bonding strength greater than 0.1N/mm.

In some embodiments, the constraining layer 400 is a sleeve that is disposed over the exterior of the electrode assembly 300.

To further prevent the electrode assembly 300 from being locked, in some embodiments, a gap is pre-set between the inner wall of the constraining layer 400 and the inner wall of the case 100, which may further provide more room for the electrode assembly 300 to expand.

After the electrode assembly 300 is expanded, the electrode assembly 300 indirectly contacts the inner wall of the case 100 through the constraining layer 400. To further prevent the electrode assembly 300 from being locked, as shown in fig. 23, fig. 23 shows a projection view of the electrode assembly 300, and the constraining layer 400 is fitted around the outside of the electrode assembly 300 to form a three-dimensional shape identical to that of the electrode assembly 300.

In some embodiments, the three-dimensional shape of the constraining layer 400 when it is not mounted on the outside of the electrode assembly 300 is different from the three-dimensional shape of the electrode assembly 300, and the elasticity of the constraining layer 400 makes the three-dimensional shape formed after it is mounted on the outside of the electrode assembly 300 the same as the three-dimensional shape of the electrode assembly 300.

In other embodiments, the three-dimensional shape of the constraining layer 400 when it is not fitted over the outside of the electrode assembly 300 is the same as the three-dimensional shape of the electrode assembly 300. As shown in fig. 24, fig. 24 is an exploded view of a battery cell 45, in which an electrode assembly 300 is a regular hexagonal prism and a constraining layer 400 is a regular hexagonal prism, and in other embodiments, when the electrode assembly 300 is in other three-dimensional shapes, the constraining layer 400 is in the same other three-dimensional shapes.

In some embodiments, as shown in fig. 24, the outer shape of the case 100 is configured as a cylinder, and accordingly, the projection of the end cap assembly 200 in the height direction H of the battery cell is circular.

When the projection of the external shape of the end cap assembly 200 along the height direction H of the battery cell is a polygon, at least the edge of the housing 100 at the opening is also the same polygon, and it is necessary to align the housing 100 and the end cap assembly 200 during assembly so that the projected vertex and the projected edge of the two overlap; after the alignment, the housing 100 and the end cap assembly 200 need to be welded and fixed, and when the welding is performed, the welding gun needs to be stopped and the welding direction needs to be changed every time the vertex of the polygon is reached. The cylindrical shell 100 and the end cover assembly 200 with the circular projection do not need to be aligned during assembly and can be directly covered, and the cylindrical shell and the end cover assembly can be welded along an annular path at one time during welding without pause, so that the assembly difficulty is reduced, the assembly efficiency is improved, and the working time cost is reduced.

The battery cell 45 and the battery 4 of the embodiment of the present application are described above, and the electric device is described by taking the vehicle 1 as an example, and the method and the apparatus for manufacturing the battery cell 45 of the embodiment of the present application will be described below, wherein the parts not described in detail can be referred to the foregoing embodiments.

Fig. 25 shows a schematic flow diagram of a method of manufacturing a battery cell 45 according to an embodiment of the present application, which may include:

s100, providing a shell 100, wherein the shell 100 is provided with a cylindrical accommodating cavity 110;

s200, providing an electrode assembly 300, wherein the projection of the electrode assembly 300 along the height direction H of the single battery is a polygon;

s300, the electrode assembly 300 is disposed in the receiving cavity 110.

Fig. 26 shows a schematic block diagram of a manufacturing apparatus 500 of a battery cell 45 according to an embodiment of the present application, and the manufacturing apparatus 500 may include: a first providing device 510, a second providing device 520, and an assembling device 530.

The first providing device 510 is used for providing the housing 100, and the housing 100 is provided with a cylindrical accommodating cavity 110;

the second providing device 520 is used for providing the electrode assembly 300, and the projection of the electrode assembly 300 along the height direction H of the battery cell is a polygon;

the assembling device 530 serves to dispose the electrode assembly 300 within the receiving cavity 110.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A battery cell, comprising:

a housing having a cylindrical accommodation chamber;

2. The battery cell of claim 1, wherein the projection of the electrode assembly is pentagonal, hexagonal, octagonal, decagonal, or hexadecagonal.

3. The battery cell according to claim 1, wherein any cross section of the electrode assembly perpendicular to the height direction of the battery cell is polygonal in shape.

4. The battery cell of claim 1, wherein the electrode assembly has a three-dimensional shape that is a prism.

5. The battery cell according to claim 4, wherein the three-dimensional shape of the electrode assembly is a regular prism.

6. The cell according to any one of claims 1 to 5, wherein the projected adjacent sides of the electrode assembly smoothly transition.

7. The battery cell according to claim 1, wherein a ratio of the projected circumscribed circle diameter of the electrode assembly to the diameter of the receiving cavity is 90% to 100%.

8. The battery cell according to claim 7, wherein a ratio of the projected circumscribed circle diameter of the electrode assembly to the diameter of the receiving cavity is 95% to 100%.

9. The battery cell of claim 1, wherein the electrode assembly comprises a first pole piece and a second pole piece of opposite polarity to the first pole piece, the first pole piece and the second pole piece being wound to form the electrode assembly;

10. The battery cell of claim 1, wherein the electrode assembly comprises a first pole piece and a second pole piece of opposite polarity to the first pole piece, the first pole piece and the second pole piece being wound to form the electrode assembly;

11. The battery cell of claim 1, wherein the electrode assembly comprises a first pole piece and a second pole piece of opposite polarity to the first pole piece, the first pole piece and the second pole piece being wound to form the electrode assembly;

12. The battery cell according to claim 11, wherein a projection of a winding start end edge of the first pole piece in a height direction of the battery cell and a projection of a winding end edge of the first pole piece in the height direction of the battery cell are located in two adjacent regions, and a projection of a winding start end edge of the second pole piece in the height direction of the battery cell and a projection of a winding end edge of the second pole piece in the height direction of the battery cell are located in two adjacent regions.

13. The battery cell of claim 1, further comprising:

14. The battery cell of claim 13, wherein the tie layer is a sleeve that is disposed over the electrode assembly.

15. The battery cell of claim 14, wherein a void is between the tie layer and an inner wall of the housing.

16. The battery cell as recited in claim 15 wherein the tie layer disposed around the electrode assembly defines a three-dimensional shape that is the same as the three-dimensional shape of the electrode assembly.

17. A battery comprising a cell according to any one of claims 1 to 16.

18. An electric device characterized by comprising the battery according to claim 17.

19. A method for preparing a battery cell, comprising:

disposing the electrode assembly within the receiving cavity.

20. A device for preparing a battery cell, comprising: