Battery cells, battery packs and electrical devices

Abstract

A battery cell (20), a battery device (100), and an electrical device (1000) are provided. The battery cell includes: a housing assembly (21); an electrode assembly (22) disposed within the housing assembly and including a first electrode (221), a second electrode (222), and a separator (223), the separator being disposed between the first electrode and the second electrode, the electrode assembly including a winding axis, the electrode assembly being a core-shaped structure wound around the winding axis, and including a plurality of winding layers perpendicular to the winding axis, the winding layers including the first electrode, the separator, and the second electrode stacked together; and a buffer (23) disposed within at least one winding layer, wherein the first electrode and / or the second electrode are provided with receiving grooves (224), and a portion of the buffer is located within the receiving grooves.

Description

Battery cell, battery device and electric device TECHNICAL FIELD

[0001] The present application relates to the technical field of battery, in particular to a battery cell, a battery device and an electric device. BACKGROUND

[0002] In recent years, new energy vehicles have made a great leap in development. In the field of electric vehicles, power batteries, as the power source of electric vehicles, play an irreplaceable important role. The battery is composed of a box body and a plurality of battery cells contained in the box body. Among them, the battery as a core component of new energy vehicles has high requirements in terms of safety and service life. However, the battery cells in the battery are prone to swelling during the cycle charging and discharging process, which affects the reliability of the battery cell.

[0003] SUMMARY

[0004] The embodiments of the present application provide a battery cell, a battery device and an electric device, which can effectively alleviate the swelling problem of the electrode sheet inside the battery cell, and can improve the reliability of the battery cell and the battery device.

[0005] In a first aspect, the embodiments of the present application provide a battery cell, comprising: a shell assembly; an electrode assembly arranged in the shell assembly and comprising a first electrode sheet, a second electrode sheet and a separator film, the separator film being arranged between the first electrode sheet and the second electrode sheet, the electrode assembly comprising a winding axial direction, the electrode assembly being a winding core structure wound around the winding axial direction and comprising a plurality of winding layers perpendicular to the winding axial direction, the winding layer comprising the first electrode sheet, the separator film and the second electrode sheet arranged in layers; and a buffer member arranged in at least one winding layer, wherein the first electrode sheet and / or the second electrode sheet is provided with a receiving groove, and part of the buffer member is located in the receiving groove.

[0006] In the above technical solution, since the buffer member is arranged in at least one winding layer, the buffer member can undertake the buffering effect between the outer electrode sheet and the inner electrode sheet of the electrode assembly, can provide swelling force release space for the inner electrode sheet and the outer electrode sheet at the same time, effectively alleviate the situation that the swelling force of the inner electrode sheet is accumulated to the outer electrode sheet, is conducive to reducing the tensile force received by the outer electrode sheet, reducing the probability of fracture of the outer electrode sheet, and improving the reliability of the battery cell. Moreover, since the buffer member is arranged in the winding layer, the buffer member can be assembled into the shell together with the electrode assembly, which can make the assembly of the buffer member in the battery cell simpler and is conducive to reducing the overall assembly difficulty of the battery cell.

[0007] By providing the accommodating groove in the first and / or second pole piece at the position of the buffer piece, and locating the buffer piece in the accommodating groove, the gap between the first and second pole pieces at the position of the buffer piece can be reduced, the risk of metal ion precipitation of the positive pole piece between the first and second pole pieces can be reduced, the loss of active metal ions can be reduced, the capacity retention rate can be improved, the stability of the electrode assembly and reaction kinetics can be improved, the battery internal resistance can be reduced, the charging and discharging efficiency can be improved, the risk of irreversible damage to the internal structure of the battery can be reduced, the stability of the electrode assembly can be improved, and the reliability of the battery cell as a whole can be improved.

[0008] In some embodiments of the present application, the accommodating groove comprises a bottom groove wall and side groove walls provided at least at two ends of the bottom groove wall, and the buffer piece is provided at least on the bottom groove wall.

[0009] In the above technical solution, the first and / or second pole piece can be formed by partially cutting in the thickness direction to form the accommodating groove, which can not only provide a mounting position for the buffer piece and reduce the gap between the first and second pole pieces, but also ensure the integrity of the first and / or second pole piece at the position of the buffer piece, which is conducive to the winding of the first and second pole pieces and the separator into the core, reduces the difficulty of core forming, and thus improves the core quality. The first and / or second pole piece is partially cut to form the accommodating groove, which is also conducive to positioning the buffer piece before winding, can improve the position accuracy of the buffer piece in the winding layer, enhance the buffering effect of the buffer piece on the expected position of the electrode assembly, and reduce the risk of swelling and fracture of the outer pole piece.

[0010] In some embodiments of the present application, the first and second pole pieces each comprise a current collector and an active material layer coated on the surface of the current collector, and the accommodating groove is provided on the active material layer.

[0011] In the above technical solution, by providing the accommodating groove on the active material layer, the thickness of the current collector can remain consistent, which is conducive to ensuring the integrity of the current collector and improving the strength of the current collector, facilitating the winding of the first and second pole pieces into the core, improving the core quality, and thus improving the reliability of the electrode assembly as a whole.

[0012] In some embodiments of the present application, the first and second pole pieces each comprise a current collector and an active material layer coated on the surface of the current collector, and the accommodating groove is provided on the current collector and penetrates the active material layer.

[0013] In the above technical solution, by providing the accommodating groove on the current collector and penetrating the active material layer, the accommodating groove can have a larger groove depth and provide a larger accommodating space, which is conducive to reducing the gap between the first and second pole pieces, thereby further reducing the risk of metal ion precipitation in the winding layer at the position of the buffer piece, improving the reliability of the electrode assembly, and thus improving the reliability of the battery cell.

[0014] In some embodiments of the present application, the accommodation groove is arranged on the first tab and penetrates the first tab along the thickness direction of the first tab; or the accommodation groove is arranged on the second tab and penetrates the second tab along the thickness direction of the second tab.

[0015] In the above technical solution, the accommodation groove completely penetrates the first tab or the second tab at the location, so that the accommodation groove can have a larger groove depth, thereby further reducing the gap between the first tab and the second tab, and further reducing the risk of metal ion precipitation in the winding layer at the location of the buffer, improving the reliability of the electrode assembly, and further improving the overall reliability of the battery cell. The above scheme can also make the internal structure of the electrode assembly more compact, so that the electrode assembly can have a larger size in the shell assembly, thereby improving the volumetric energy density of the battery cell.

[0016] In some embodiments of the present application, the electrode assembly includes a main body portion and a tab connected to each other, the main body portion includes a flat portion and an arc-shaped portion connected to each other, and the accommodation groove is arranged on the arc-shaped portion.

[0017] In the above technical solution, since the arc-shaped portion of the main body portion is an arc-shaped structure and has a change in curvature, stress concentration phenomenon is more likely to occur during the cyclic expansion of the electrode assembly, and the arc-shaped portion bears a larger expansion tensile force than other positions of the main body portion. By arranging the accommodation groove on the arc-shaped portion, the buffer is also arranged on the arc-shaped portion correspondingly. When the first tab and / or the second tab at the position corresponding to the arc-shaped portion expands, the buffer can be compressed to absorb energy, reduce the expansion tensile force, and provide space required for the expansion of the first tab and / or the second tab, which is conducive to reducing the risk of tab fracture at the position of the arc-shaped portion. Also, it can reduce the probability of overall expansion fracture of the electrode assembly, thereby improving the reliability of the battery cell. Since the accommodation groove is arranged on the arc-shaped portion, the size of the accommodation groove around the winding direction of the electrode assembly is smaller, and the buffer is arranged in the accommodation groove. Therefore, the setting area of the buffer in the main body portion can be reduced, the material can be saved, the cost can be reduced, the volume of the buffer can be reduced, the internal space of the shell assembly can be saved, and the weight of the buffer can be reduced. In turn, the overall weight of the battery cell can be reduced, thereby improving the volumetric energy density of the battery cell.

[0018] In some embodiments of the present application, the opposite ends of the flat portion are provided with arc-shaped portions, and the two arc-shaped portions are each provided with a receiving groove and a buffer. In this technical solution, the two arc-shaped portions are each provided with a receiving groove and a buffer, the buffer can provide the space required for expansion for the arc-shaped portion at each end of the flat portion, the two buffers together can provide greater space for expansion release, and can also provide timely buffering and the space required for expansion for each arc-shaped portion, which can reduce the risk of expansion rupture of the outer pole piece at the position of the arc-shaped portion, further improve the reliability of the electrode assembly, and further improve the reliability of the battery cell.

[0019] In some embodiments of the present application, the receiving grooves and buffers of the two arc-shaped portions are arranged in the same winding layer or in different winding layers.

[0020] In the above technical solution, the receiving grooves and buffers of the two arc-shaped portions are arranged in the same winding layer, so that the buffer can buffer the stress generated in the layer, can timely absorb and disperse the stress, effectively reduce the risk of stress concentration in a local area, better protect the first pole piece or the second pole piece in the layer, reduce the risk of rupture of the pole piece in the layer, and help the consistency of the winding layer in the layer, which is conducive to improving the overall consistency of the battery cell. The receiving grooves and buffers of the two arc-shaped portions are arranged in different winding layers, which can buffer the stress generated inside the electrode assembly from multiple aspects. Since the stress inside the electrode assembly is a complex system, the stresses from different winding layers will superimpose and affect each other. By arranging the buffers in different winding layers, it is conducive to comprehensively buffering the stress of each layer, reducing the accumulation and transmission of stress inside the electrode assembly, and better protecting the entire electrode assembly and improving the overall reliability of the battery cell.

[0021] In some embodiments of the present application, the receiving groove and the buffer are centrally arranged on the arc-shaped portion in the winding direction of the arc-shaped portion.

[0022] In the above technical solution, since the position of the arc-shaped portion of the electrode assembly itself has the problem of stress concentration, and the middle position of the arc-shaped portion is a relatively large stress point, the receiving groove and the buffer are centrally arranged on the arc-shaped portion, thereby targetedly relieving the stress concentration of the arc-shaped portion, which is conducive to better absorbing and dispersing the stress by the buffer and reducing the stress size borne by the middle position of the arc-shaped portion. Secondly, the central arrangement of the buffer on the arc-shaped portion is also conducive to balancing the stress distribution inside the entire electrode assembly, can diffuse the stress originally concentrated in the middle position of the arc-shaped portion to the periphery, makes the stress of each part of the electrode assembly more uniform, thereby reducing the risk of expansion rupture of the outer pole piece caused by local large stress, and is conducive to improving the reliability of the electrode assembly and further improving the overall reliability of the battery cell.

[0023] In some embodiments of the present application, a plurality of buffer members are arranged in the accommodation grooves, and the plurality of buffer members are symmetrically arranged along the winding direction of the arc-shaped portion. In this technical solution, the size of the buffer member in the winding direction can be further reduced, thereby further reducing the volume of the buffer member, so as to further save space, which is conducive to improving the volume ratio of the electrode assembly in the shell assembly, and the weight of the buffer member can be further reduced, thereby reducing the overall weight of the battery monomer, so as to further improve the volume energy density of the battery monomer.

[0024] In some embodiments of the present application, the buffer member has a central surface in the winding direction of the arc-shaped portion, and two buffer members are arranged in the accommodation grooves, and the central surface of the buffer member is close to or coincides with the quarter division line of the arc length of the arc-shaped portion.

[0025] In the above technical solution, the position of the quarter division line of the arc length of the arc-shaped portion is close to the position of the two end edges of the arc-shaped portion, and the position of the two end edges of the arc-shaped portion is a key point of stress dispersion. By making the central surface of the buffer member close to or coincide with the quarter division line, the buffer member can better adapt to the direction of stress transmission, disperse the stress to a wider area, and reduce the degree of local stress concentration. When the electrode assembly is bent and deformed, the two end positions of the arc-shaped portion first bear the bending stress. The above scheme can effectively absorb and buffer the bending stress, reduce the risk of damage to the internal structure of the electrode assembly due to excessive bending, improve the reliability of the electrode assembly, and further improve the overall reliability of the battery monomer. Moreover, the above scheme can also make the first electrode sheet or the second electrode sheet form a certain gap at the middle position of the arc-shaped portion in the winding layer where the buffer member is located, which can provide the space required for the expansion of the middle position of the arc-shaped portion, is also conducive to reducing the probability of stress concentration at the middle position of the arc-shaped portion, and can improve the reliability of the battery monomer.

[0026] On the other hand, since the arc-shaped portion has an arc-shaped structure and the shell assembly generally has a square shape, a certain space will be formed between the two ends of the arc-shaped portion in the winding direction and the shell assembly. By making the central surface of the two buffer members close to or coincide with the quarter division line of the arc length of the arc-shaped portion, the space formed between the arc-shaped portion and the shell assembly can be fully utilized to arrange the buffer members, which can improve the space ratio of the electrode assembly in the shell assembly, make the internal structure of the battery monomer more compact, and be conducive to making the battery monomer have a higher volume energy density.

[0027] In some embodiments of the present application, in the winding layer where the buffer member is located, the accommodation grooves penetrate the first electrode sheet and / or the second electrode sheet along the thickness direction of the winding layer and the winding axis of the electrode assembly, and the first end portion and the second end portion are formed on the first electrode sheet or the second electrode sheet.

[0028] In the technical solution, the first tab and / or the second tab can form the accommodation groove by disconnection, which can reduce the manufacturing difficulty of the accommodation groove, improve the manufacturability, reduce the cost, and improve the forming quality of the accommodation groove. Moreover, the technical solution can also reduce the size of the gap formed between the first tab and the second tab in the winding direction of the electrode assembly and the thickness direction of the winding layer, further reduce the risk of metal ion precipitation in the winding layer at the position of the buffer, and further improve the reliability of the battery cell.

[0029] In some embodiments of the present application, the electrode assembly includes a main body part and a tab connected to each other, the main body part includes a flat part and an arc-shaped part, the arc-shaped part is connected to both ends of the flat part in a first direction, and the first end part and the second end part are arranged on the arc-shaped part.

[0030] In the technical solution, the first end part and the second end part are arranged on the arc-shaped part, so that the accommodation groove is located on the arc-shaped part, and the buffer can be arranged on the arc-shaped part. In this way, the buffer can play a buffering role at the position where the stress is relatively concentrated in the electrode assembly, and the expansion tensile force on the first tab or the second tab at the position of the arc-shaped part can be reduced, thereby reducing the probability of expansion rupture of the outer tab and reducing the risk of expansion rupture of the entire electrode assembly, and improving the reliability of the battery cell.

[0031] In some embodiments of the present application, the arc-shaped part has a joint line connected to the flat part, and in the winding direction of the arc-shaped part, the distance between the first end part and the second end part and the adjacent joint line is less than or equal to one-fourth of the arc length of the arc-shaped part.

[0032] In the technical solution, the distance between the first end part and the second end part and the buffer can be appropriately adjusted, the size of the gap formed between the first tab and the second tab in the winding direction and the thickness direction of the winding layer can be further reduced, the condition of the gap between the first tab and the second tab can be effectively improved, the probability of metal ion precipitation can be reduced when the buffer is arranged in the winding layer, the stability of the electrode assembly can be improved, and the reliability of the battery cell can be improved.

[0033] In some embodiments of the present application, the distance between the first end part or the second end part and the buffer is greater than or equal to 3 mm. By setting the distance between the first end part or the second end part and the buffer within the above range, the size of the gap formed between the first tab and the second tab in the winding direction and the thickness direction of the winding layer can be reduced to a more optimal value, the effect of improving the gap between the first tab and the second tab is better, the effect of reducing the metal ion precipitation condition is also better, the stability of the electrode assembly can be further improved, and the reliability of the battery cell can be improved.

[0034] In some embodiments of the present application, the first or second pole piece of each of the two arc-shaped portions is provided with a receiving groove, and is provided with a first end portion and a second end portion.

[0035] In the above technical solution, the sum of the sizes of the disconnected portions of the two first or second pole pieces in the winding direction of the winding layer is relatively small, which can reduce the size of the disconnected area of the first or second pole piece, reduce the cutting loss of the pole piece, that is, reduce the capacity loss, and help to maintain a high capacity of the battery monomer as a whole, so that the battery monomer has a higher volumetric energy density.

[0036] In some embodiments of the present application, the plurality of winding layers includes a first winding layer and a second winding layer connected to each other, the first winding layer includes a first arc-shaped portion located at one end of the first direction, the second winding layer includes a first flat portion and a second arc-shaped portion located at the other end of the first direction, the first flat portion connects the second arc-shaped portion and the first arc-shaped portion, the first arc-shaped portion and the second arc-shaped portion are each provided with a buffer, the receiving groove extends along the first arc-shaped portion, the first flat portion and the second arc-shaped portion, the first end portion is arranged in the first arc-shaped portion and located on the side of the buffer away from the first flat portion, and the second end portion is arranged in the second arc-shaped portion and located on the side of the buffer away from the first flat portion.

[0037] In the above technical solution, the part of the first or second pole piece located in the first arc-shaped portion, the first flat portion and the second arc-shaped portion is cut to form the receiving groove, which makes the first or second pole piece form a gap only on the side away from the first flat portion, so that the position where the first or second pole piece can form a gap is relatively small, the size of the gap in the winding direction of the winding layer can be reduced, the probability of metal ion precipitation of the electrode assembly can be reduced, and the reliability of the battery monomer can be improved. Moreover, the above solution can form the receiving groove at both ends of the first direction of the flat portion after winding with only one cutting of the first or second pole piece, which helps to reduce the manufacturing process of the electrode assembly and the assembly composed of the buffer, thereby reducing the manufacturing difficulty, improving the work efficiency, improving the forming quality of the electrode assembly and the assembly composed of the buffer, and improving the reliability of the battery monomer.

[0038] In some embodiments of the present application, the plurality of winding layers comprises a first winding layer and a second winding layer connected to each other, the first winding layer comprises a first arc-shaped portion located at one end of the first direction, the second winding layer comprises a first flat portion, a second arc-shaped portion, a second flat portion and a third arc-shaped portion, the first flat portion connects the first arc-shaped portion and the second arc-shaped portion, the second flat portion connects the second arc-shaped portion and the third arc-shaped portion, the first arc-shaped portion and the second arc-shaped portion are both provided with a buffer, the accommodation groove extends along the first arc-shaped portion, the first flat portion, the second arc-shaped portion, the second flat portion and the third arc-shaped portion, the first end portion is arranged in the first arc-shaped portion and located at a side of the center of the first arc-shaped portion away from the first flat portion, and the second end portion is arranged in the third arc-shaped portion and located at a side of the center of the third arc-shaped portion close to the second flat portion.

[0039] In the above technical solution, the part of the first or second pole piece located at the first arc-shaped portion, the first flat portion, the second arc-shaped portion, the second flat portion and the third arc-shaped portion is cut to form the accommodation groove, which makes the first pole piece and the second pole piece form a gap only at a side away from the first flat portion and the second arc-shaped portion, so that the position where the first pole piece and the second pole piece can form a gap is less, the size of the gap in the winding direction of the winding layer can be further reduced, the probability of metal ion precipitation of the electrode assembly is reduced, and the reliability of the battery cell is improved. Moreover, the above solution can form the accommodation groove at both ends of the flat portion in the first direction after winding under the condition that the first or second pole piece is cut only once, which is conducive to reducing the manufacturing process of the electrode assembly and the assembly composed of the buffer, thereby reducing the manufacturing difficulty, improving the manufacturability, improving the work efficiency, and improving the forming quality of the electrode assembly and the assembly composed of the buffer, thereby improving the reliability of the battery cell.

[0040] In some embodiments of the present application, the first end portion and the second end portion are staggered with each other in the winding direction of the third arc-shaped portion. In this technical solution, the first end portion and the second end portion are staggered with each other in the winding direction of the third arc-shaped portion, so that the first end portion and the second end portion can have a certain distance therebetween, the probability of stress concentration of the pole piece between the first end portion and the second end portion is reduced, the risk of fracture or damage of the pole piece between the first end portion and the second end portion is reduced, the reliability of the electrode assembly is improved, and the reliability of the battery cell is improved.

[0041] In some embodiments of the present application, the first pole piece is an anode piece, the second pole piece is a cathode piece, and the accommodation groove is arranged. In this technical solution, since the cathode piece has a relatively high cost, the material amount of the cathode piece in the electrode assembly can be reduced by cutting the cathode piece to form the accommodation groove and installing the buffer, which is conducive to reducing the cost.

[0042] In some embodiments of the present application, the buffer is provided with an adhesive piece on the side away from the first tab, and the two ends of the adhesive piece exceed the buffer in the winding direction of the electrode assembly and are bonded to the first tab.

[0043] In the above technical solution, the adhesive piece is a separate component and can be mass-produced, which is conducive to ensuring controllable adhesion, thereby making the adhesion force more uniform when the adhesive piece is bonded to the first tab, improving the reliability of the buffer fixed on the first tab, and the fixing method is relatively simple and easy to operate, which is conducive to improving the assembly efficiency. Since the second tab is a cathode tab, the adhesive piece can be easily bonded to the cathode tab through the above scheme, and the adhesion of the adhesive piece and the cathode tab is ensured, which is conducive to improving the fixing reliability of the buffer, thereby improving the buffering effect of the buffer on the arc-shaped part, reducing the risk of stress concentration, and reducing the probability of expansion and fracture of the outer tab at the position of the arc-shaped part, thereby improving the reliability of the battery cell. Secondly, the adhesive piece can also separate the first tab and the second tab at the position of the buffer, so that the first tab and the second tab at the position of the gap do not react as much as possible, thereby reducing the possibility of metal ion migration, and reducing the risk of metal ion precipitation caused by the existence of the gap, thereby improving the reliability of the electrode assembly and the battery cell.

[0044] In some embodiments of the present application, the buffer is bonded to the first tab on the side close to the first tab.

[0045] In the above technical solution, the buffer can be bonded to the first tab only on the side close to the first tab, and the buffer is fixed on the first tab in this way. The fixing method is relatively simple, which can reduce costs and improve work efficiency. The buffer can also be bonded to the first tab on the side close to the first tab, and an adhesive piece is provided on the other side away from the first tab, and the adhesive piece is bonded to the first tab. In this way, the two sides of the adhesive piece can be limited and fixed, which can make the fixation of the buffer more reliable, and is conducive to reducing the probability of the buffer separating from the first tab and improving the reliability of the buffering effect of the buffer on the electrode assembly.

[0046] In some embodiments of the present application, the buffer includes any one of a rectangular shape, a T shape, and an arc shape. In this technical solution, by providing the buffer with the above shapes, more design options can be provided for the buffer. According to the size of the winding core of the electrode assembly, selecting a buffer with a different shape can adjust the size of the gap between the first tab and the second tab in the winding layer and the size of the electrode assembly, so as to make a trade-off between the buffering effect and the battery capacity as needed, which is conducive to meeting flexible design requirements.

[0047] In some embodiments of the present application, the buffer is arranged between the separator films at the two ends of the thickness direction of the winding layer where the second tab is located, and the buffer is provided with an adhesive piece, the two ends of the adhesive piece extend beyond the buffer, and one end is bonded to the first end portion and the other end is bonded to the second end portion.

[0048] In the above technical solution, the buffer is arranged in the space formed by the disconnection position of the second tab, thereby not needing to additionally increase space for arranging the buffer, which can improve the structural compactness of the electrode assembly, improve the unit volume density of the electrode assembly, and further improve the volume energy density of the battery cell. Although there is a gap between the two separator films where the buffer is located, the gap is located at the two ends of the thickness direction of the winding layer, and only the first tab is present, without the second tab, which can reduce the probability of chemical reaction at the position of the gap and the migration of metal ions, further reduce the risk of metal ion precipitation of the positive tab, and improve the reliability of the battery cell. The buffer connects the first end portion and the second end portion through the adhesive piece, which can connect the two disconnected parts of the second tab before the electrode assembly is wound into a core, which is conducive to winding the electrode assembly into a core, reduces the winding difficulty, reduces the manufacturing cost, and improves the product yield. The above solution can also fix the buffer in the winding layer, reduce the probability of displacement of the buffer and deviation from the expected position, improve the position reliability of the buffer in the electrode assembly, and facilitate the buffer to maintain stable and reliable buffering effect.

[0049] In some embodiments of the present application, the adhesive piece is arranged at the two ends of the thickness direction of the buffer and connects the first end portion and the second end portion.

[0050] In the above technical solution, the adhesive piece is arranged at the two ends of the thickness direction of the buffer and connects the first end portion and the second end portion, which can limit the two ends of the thickness direction of the buffer, improve the connection strength of the buffer and the second tab, and further improve the position reliability of the buffer in the electrode assembly. Moreover, the above solution can more firmly connect the two disconnected parts of the buffer and the second tab, which can improve the rigidity of the buffer and the second tab as a whole, facilitate the second tab to be more smoothly bent during winding, reduce the difficulty of winding the electrode assembly into a core, and improve the quality and reliability of the core. In addition, when the second tab is cut to form the first end portion and the second end portion, burrs and other structures are easily formed, and the adhesive piece in the above solution can play a separation role between the first end portion, the second end portion, and the separator film, which can reduce the risk of the burrs and other structures piercing the separator film, and improve the reliability of the electrode assembly.

[0051] In some embodiments of the present application, the electrode assembly comprises a main body portion and a tab connected to each other, the main body portion comprises a flat portion and an arc-shaped portion connected to each other, the accommodating groove is arranged on the arc-shaped portion, and the length of the part of the second tab between the buffer and the arc-shaped portion is greater than or equal to 5 mm.

[0052] In the technical solution, the second tab has a proper length in the arc-shaped part for connecting the adhesive piece, which improves the manufacturability, the connection strength and reliability of the second tab and the adhesive piece, and reduces the risk of the adhesive piece entering the flat part, the stress concentration and damage of the first tab and the second tab in the flat part when compressed during the flattening process after winding, and the reliability of the electrode assembly.

[0053] In some embodiments of the present application, the distance between the first end or the second end and the buffer is greater than or equal to 3 mm. In the technical solution, the distance between the first end or the second end and the buffer is properly left, which facilitates the adhesion of the adhesive piece, improves the manufacturability, ensures the forming quality of the electrode assembly, provides a certain space for the compression and expansion of the buffer, ensures the functionality of the buffer, reduces the risk of the outer tab expanding and breaking, and improves the reliability of the battery cell.

[0054] In some embodiments of the present application, the thickness of the buffer is greater than the thickness of the second tab.

[0055] In the technical solution, the thickness of the buffer is greater than the thickness of the second tab, the buffer can provide a larger buffer space for the expansion deformation of the first tab, thereby reducing the expansion tensile force of the first tab on the outer tab, which is conducive to reducing the risk of the outer tab expanding and breaking, further improving the reliability of the electrode assembly, and improving the reliability of the battery cell.

[0056] In a second aspect, the embodiments of the present application also provide a battery device, which comprises the battery cell according to any one of the preceding embodiments.

[0057] In the technical solution, the buffer in the battery cell can be arranged in the accommodation groove of at least one winding layer, which reduces the risk of the outer tab breaking, reduces the risk of metal ions being precipitated from the positive tab, improves the reliability of the battery cell as a whole, improves the reliability of the battery device comprising the battery cell, improves the use performance of the battery device, and prolongs the service life of the battery device.

[0058] In a third aspect, the embodiments of the present application also provide a power consumption device, which comprises the battery cell according to any one of the preceding embodiments, or the battery device according to the preceding embodiments, the battery cell or the battery device is used for storing or providing electric energy.

[0059] In the technical solution, the battery cell and the battery device have high reliability, so the power consumption device comprising the battery cell or the battery device also has high reliability, which is conducive to the reliable operation of the power consumption device. BRIEF DESCRIPTION OF DRAWINGS

[0060] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be considered as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0061] Fig. 1 is a structural schematic diagram of a vehicle provided by some embodiments of the present application;

[0062] Fig. 2 is a structural exploded view of a battery device provided by some embodiments of the present application;

[0063] Fig. 3 is a schematic diagram of the internal structure of a battery cell provided by some embodiments of the present application;

[0064] Fig. 4 is a schematic diagram of the structure of an electrode assembly provided by some embodiments of the present application;

[0065] Fig. 5 is a schematic diagram of the partial structure of an electrode assembly provided by some embodiments of the present application;

[0066] Fig. 6 is a schematic diagram of the structure of a first tab provided with a receiving groove according to some embodiments of the present application;

[0067] Fig. 7 is a schematic diagram of the structure of a first tab provided with a receiving groove according to another embodiment of the present application;

[0068] Fig. 8 is a schematic diagram of the structure of an electrode assembly according to another embodiment of the present application;

[0069] Fig. 9 is a schematic diagram of the structure of an electrode assembly according to yet another embodiment of the present application;

[0070] Fig. 10 is a schematic diagram of the assembly of a buffer member and a first tab according to some embodiments of the present application;

[0071] Fig. 11 is a schematic diagram of the assembly of a buffer member and a first tab according to another embodiment of the present application;

[0072] Fig. 12 is a schematic diagram of the assembly of a buffer member and a first tab according to yet another embodiment of the present application;

[0073] Fig. 13 is a schematic diagram of the formation of a buffer member according to some embodiments of the present application;

[0074] Fig. 14 is a schematic diagram of the assembly of a T-shaped buffer member and a first tab according to some embodiments of the present application;

[0075] Fig. 15 is a schematic diagram of the assembly of an arc-shaped buffer member and a first tab according to some embodiments of the present application;

[0076] Fig. 16 is a structural schematic diagram of an electrode assembly according to some embodiments of the present application;

[0077] Fig. 17 is a structural schematic diagram of an electrode assembly according to some embodiments of the present application;

[0078] Fig. 18 is a schematic diagram of a buffer connected to a second tab through an adhesive sheet according to some embodiments of the present application;

[0079] Fig. 19 is a schematic diagram of a buffer connected to a second tab through an adhesive sheet according to some embodiments of the present application.

[0080] Fig. 20 is a schematic diagram of a battery device according to some embodiments of the present application. DETAILED DESCRIPTION

[0081] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0082] Unless otherwise defined, 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 specification herein is for describing particular embodiments only and is not intended to be limiting of the application. Unless otherwise defined, all terms (including 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. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure and will not be interpreted in an overly literal sense unless expressly so defined herein.

[0083] Reference throughout this application to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrase "in an embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily all directed to the same embodiment, nor are they necessarily all mutually exclusive or alternative embodiments.

[0084] In the description of the application, it is necessary to explain that, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting", "attachment" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0085] The term "and / or" in the application is only to describe the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. In addition, the character " / " in the application generally represents that the front and rear associated objects have an "or" relationship.

[0086] In the embodiments of the application, the same reference signs represent the same components, and for the sake of brevity, the detailed description of the same components is omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the application shown in the drawings, as well as the overall thickness, length, width and other dimensions of integrated devices, are only exemplary and should not constitute any limitation on the application.

[0087] "Multiple" appearing in the application means two or more (including two).

[0088] In this application, the battery cell can include lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-hydrogen battery, nickel-cadmium battery, lead-acid battery, etc. The embodiments of the present application are not limited thereto. The battery cell can be in the shape of a cylinder, a flat body, a cuboid or other shapes, etc. The embodiments of the present application are not limited thereto. The battery cell is generally divided into three types according to the packaging method: cylindrical battery cell, square battery cell and soft package battery cell, and the embodiments of the present application are not limited thereto.

[0089] The battery apparatus mentioned in the embodiments of the present application can refer to one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly can include a plurality of battery cells connected in series, parallel or mixed connection through a busbar component. In some embodiments, the battery cell assembly is generally formed by arranging a plurality of battery cells.

[0090] As an example, the battery cell assembly can be a battery module, which is formed by arranging and fixing a plurality of battery cells into an independent module. As an example, the battery module can be formed by bundling a plurality of battery cells with a cable tie.

[0091] In some embodiments, the battery apparatus can be a battery pack, which includes a box and one or more battery cell assemblies accommodated in the box. As an example, the battery cell assembly can be a battery module, which can be accommodated in the box by fixing the battery module in the box. As an example, the battery cell assembly can also be accommodated in the box by directly fixing a plurality of battery cells in the box. The box can prevent liquid or other foreign matter from affecting the charging or discharging of the battery cell.

[0092] The battery cell includes a shell, an electrode assembly, and an electrolyte, the shell being used to accommodate the electrode assembly and the electrolyte. The electrode assembly is composed of a positive electrode tab, a negative electrode tab, and a separator film. The battery cell mainly relies on the movement of metal ions between the positive electrode tab and the negative electrode tab to work. The positive electrode tab includes a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer being coated on the surface of the positive electrode current collector, the positive electrode current collector without the positive electrode active material layer protruding from the positive electrode current collector with the positive electrode active material layer, and the positive electrode current collector without the positive electrode active material layer serving as a positive electrode tab. Taking a lithium ion battery as an example, the material of the positive electrode current collector can be aluminum, and the positive electrode active material can be lithium cobaltate, lithium iron phosphate, ternary lithium, or lithium manganate, etc. The negative electrode tab includes a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer being coated on the surface of the negative electrode current collector, the negative electrode current collector without the negative electrode active material layer protruding from the negative electrode current collector with the negative electrode active material layer, and the negative electrode current collector without the negative electrode active material layer serving as a negative electrode tab. The material of the negative electrode current collector can be copper, and the negative electrode active material can be carbon or silicon, etc. In order to ensure that no fusing occurs when passing a large current, the number of positive electrode tabs is multiple and stacked together, and the number of negative electrode tabs is multiple and stacked together.

[0093] The material of the separator film can be PP (polypropylene) or PE (polyethylene), etc. In addition, the electrode assembly can be a roll type structure or a laminated type structure, and the embodiments of the present application are not limited thereto.

[0094] In recent years, new energy vehicles have made a leap in development. In the field of electric vehicles, power batteries, as the power source of electric vehicles, play an irreplaceable important role. The battery is composed of a box body and a plurality of battery cells accommodated in the box body. Among them, the battery as a core part of new energy vehicles has high requirements in terms of safety and service life. However, in the winding core type battery cell, the tabs of the electrode assembly will swell during the cycle charging and discharging process, and the tabs will swell more severely as the cycle number increases. Therefore, the outer tabs are prone to be stretched and broken in the later cycle. After the tabs are broken, on the one hand, it will cause problems such as capacity reduction, internal resistance increase, and voltage instability, affecting the performance of the battery cell; on the other hand, it will also increase the risk of thermal runaway and short circuit, affecting the safety of the battery cell. That is, the swelling and breaking of the tabs inside the battery cell will affect the reliability of the battery cell.

[0095] In a general jelly-roll type battery cell, in order to alleviate the expansion of the electrode sheet inside the battery cell, a ring of silica gel pad is usually arranged outside the outer electrode sheet of the electrode assembly. However, since the electrode sheet of the electrode assembly is a multi-layer structure from inside to outside, the expansion of each layer of electrode sheet is accumulated and leads to the largest expansion of the outer electrode sheet, and the outer electrode sheet is more prone to expansion. Therefore, by arranging the silica gel pad outside the outer electrode sheet as described above, on the one hand, the expansion of the inner multi-layer electrode sheet of the electrode assembly is still accumulated and affects the expansion of the outer electrode sheet, and cannot effectively alleviate the problem of large expansion of the outer electrode sheet, thereby improving the reliability of the battery cell; on the other hand, the arrangement of the silica gel pad outside the outer electrode sheet is not conducive to the entry of the silica gel pad into the shell, which may increase the installation difficulty and is not conducive to the assembly of the battery cell, and may also lead to a large space occupied by the silica gel pad, affecting the volume energy density of the battery cell.

[0096] Based on the above considerations, in order to solve the problem that the electrode sheet of the battery cell is prone to expansion during the cycle process, and the outer electrode sheet of the electrode assembly is prone to breakage, affecting the reliability of the battery cell. The applicant designs a battery cell, which comprises: a shell assembly, an electrode assembly and a buffer; the electrode assembly is arranged in the shell assembly, and comprises a first electrode sheet, a second electrode sheet and a separator, the separator is arranged between the first electrode sheet and the second electrode sheet, the electrode assembly comprises a winding axial direction, the electrode assembly is a jelly-roll structure wound around the winding axial direction, and comprises a plurality of winding layers perpendicular to the winding axial direction, the winding layer comprises the first electrode sheet, the separator and the second electrode sheet arranged in layers; the buffer is arranged in at least one winding layer, wherein the first electrode sheet and / or the second electrode sheet is provided with a receiving groove, and part of the buffer is located in the receiving groove.

[0097] In the battery cell with such a structure, since the buffer is arranged in at least one winding layer, the buffer can play a buffering role between the outer electrode sheet and the inner electrode sheet of the electrode assembly, and can provide a space for releasing the expansion force of the inner electrode sheet and the outer electrode sheet at the same time, effectively alleviate the situation that the expansion force of the inner electrode sheet is accumulated to the outer electrode sheet, and is conducive to reducing the tensile force acting on the outer electrode sheet, reducing the probability of breakage of the outer electrode sheet, and improving the reliability of the battery cell. Moreover, since the buffer is arranged in the winding layer, the buffer can be assembled into the shell together with the electrode assembly, which can make the assembly of the buffer in the battery cell simpler and conducive to reducing the overall assembly difficulty of the battery cell.

[0098] Meanwhile, since the first pole piece and / or the second pole piece in the winding layer at the position of the buffer member is provided with the accommodating groove, at least part of the buffer member is located in the accommodating groove, thereby reducing the gap between the first pole piece and the second pole piece at the position of the buffer member, reducing the risk of metal ion precipitation of the positive pole piece between the first pole piece and the second pole piece, facilitating to reduce the loss of active metal ions, improve the capacity retention rate, also helping to make the electrode assembly and the reaction kinetics more stable, reduce the battery internal resistance, improve the charging and discharging efficiency, and reduce the risk of causing irreversible damage to the internal structure of the battery, improve the stability of the electrode assembly, and further improve the overall reliability of the battery monomer.

[0099] The battery disclosed in the embodiments of the present application can be used in, but is not limited to, an electric device such as a vehicle, a ship or an aircraft. An electric device composed of the battery monomer, the battery device and the like disclosed in the present application can be used.

[0100] The embodiments of the present application provide an electric device using the battery device as a power supply. The electric device can be, but is not limited to, a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, an electric vehicle, an electric car, a ship, a spacecraft and the like. The electric toy can include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy and an electric aircraft toy and the like. The spacecraft can include an airplane, a rocket, a space shuttle and a spacecraft and the like.

[0101] The following embodiments are described by taking a vehicle as an example for convenience of description.

[0102] Please refer to FIG. 1, which is a structural schematic diagram of a vehicle provided by some embodiments of the present application. The vehicle can be a fuel automobile, a gas automobile or a new energy automobile, and the new energy automobile can be a pure electric automobile, a hybrid electric automobile or a range extended automobile. The vehicle is internally provided with a battery device 100, which can be arranged at the bottom, the head or the tail of the vehicle. The battery device 100 can be used for power supply of the vehicle, for example, the battery device 100 can be used as an operating power supply of the vehicle. The vehicle can further include a controller 200 and a motor 300, and the controller 200 is used to control the battery device 100 to supply power to the motor 300, for example, to meet the working power demand of the vehicle during starting, navigation and driving.

[0103] In some embodiments of the present application, the battery device 100 can not only be used as an operating power supply of the vehicle, but also be used as a driving power supply of the vehicle, instead of or partially instead of fuel or natural gas to provide driving power for the vehicle.

[0104] Please refer to FIG. 2, which is an exploded view of the battery device 100 according to some embodiments of the present application. The battery device 100 includes a box 10 and a plurality of battery cells 20, which are accommodated in the box 10. The box 10 is configured to provide a mounting space for the battery cells 20, and can have various structures. In some embodiments, the box 10 can include a first box body 11 and a second box body 12, which are coupled to each other to define a mounting space for the battery cells 20. The second box body 12 can be a hollow structure with one end open, and the first box body 11 can be a plate structure, which is coupled to the open end of the second box body 12 to define the mounting space together with the second box body 12. Alternatively, the first box body 11 and the second box body 12 can both be hollow structures with one side open, and the open side of the first box body 11 is coupled to the open side of the second box body 12. Of course, the box 10 formed by the first box body 11 and the second box body 12 can have various shapes, such as a cylinder or a cuboid.

[0105] In the battery device 100, the plurality of battery cells 20 can be connected in series, in parallel, or in a mixed manner. The mixed manner means that some of the plurality of battery cells 20 are connected in series and some are connected in parallel. The plurality of battery cells 20 can be directly connected in series, in parallel, or in a mixed manner, and then accommodated in the box 10. Alternatively, the plurality of battery cells 20 can be first connected in series, in parallel, or in a mixed manner to form a battery module, and then a plurality of battery modules are connected in series, in parallel, or in a mixed manner to form a whole, which is accommodated in the box 10. The battery device 100 can further include other structures, for example, the battery device 100 can further include a busbar component for electrically connecting the plurality of battery cells 20.

[0106] Please refer to FIG. 2, which is an exploded view of the battery device 100 according to some embodiments of the present application. The battery device 100 includes a plurality of rows of battery cells 20, which are arranged along the length direction of the box 10. Each row of battery cells 20 includes a plurality of battery cells 20 arranged along the width direction of the box 10. Alternatively, the plurality of rows of battery cells 20 are arranged along the width direction of the box 10, and each row of battery cells 20 includes a plurality of battery cells 20 arranged along the length direction of the box 10.

[0107] Each battery cell 20 can be a secondary battery or a primary battery, where the secondary battery refers to a battery cell 20 that can be used continuously by activating the active material through charging after the battery cell is discharged; it can also be a lithium ion battery, a sodium ion battery, a sodium lithium ion battery, a lithium metal battery, a sodium metal battery, a lithium sulfur battery, a magnesium ion battery, a nickel-hydrogen battery, a nickel-cadmium battery, a lead-acid battery, etc., and the present application is not limited thereto. The battery cell 20 can be in the shape of a cylinder, a flat body, a cuboid, or other shapes, etc. For example, in FIG. 2, the shape of the battery cell 20 is a cuboid.

[0108] According to some embodiments of the present application, referring to FIG. 3, the present application provides a battery cell 20, comprising: a housing assembly 21, an electrode assembly 22, and a buffer 23. The electrode assembly 22 is arranged in the housing assembly 21, and comprises a first electrode sheet 221, a second electrode sheet 222, and a separator 223 arranged between the first electrode sheet 221 and the second electrode sheet 222. The electrode assembly 22 comprises a winding axial direction, and the electrode assembly 22 is in the form of a winding core structure wound around the winding axial direction, and comprises a plurality of winding layers perpendicular to the winding axial direction, and the winding layers comprise the first electrode sheet 221, the separator 223, and the second electrode sheet 222 arranged in layers. The buffer 23 is arranged in at least one winding layer, wherein the first electrode sheet 221 and / or the second electrode sheet 222 is provided with a receiving groove 224, and at least part of the buffer 23 is arranged in the receiving groove 224.

[0109] The housing assembly 21 can refer to a component that accommodates the electrode assembly 22 and the electrolyte, and protects the internal electrode assembly 22 and the electrolyte. For example, referring to FIG. 3, the housing assembly 21 can include, but is not limited to, a housing 211 and a cover plate 212, etc., wherein the housing 211 and the cover plate 212 can be, but are not limited to, metal or plastic, etc. The metal material can be, but is not limited to, steel or aluminum, etc. The plastic material can be, but is not limited to, polycarbonate, polypropylene, etc.

[0110] The explanation of the electrode assembly 22 can refer to the foregoing, and will not be specifically explained here. One of the first electrode sheet 221 and the second electrode sheet 222 can refer to an anode sheet, and the other can refer to a cathode sheet. For example, the first electrode sheet 221 can be an anode sheet (negative electrode sheet), and the second electrode sheet 222 can be a cathode sheet (positive electrode sheet).

[0111] The electrode assembly 22 comprises a winding axial direction, and the electrode assembly 22 is in the form of a winding core structure wound around the winding axial direction. It can be understood that the electrode assembly 22 referred to in the present application is a winding core, and the winding axial direction can refer to a direction perpendicular to the winding plane of the winding core. For example, referring to FIG. 3, the winding axial direction can refer to the third direction Z of FIG. 3.

[0112] In the electrode assembly 22 of the embodiment of the present application, when being wound, the first electrode sheet 221, the separator 223 and the second electrode sheet 222 can be sequentially arranged from bottom to top, and a layer of the separator 223 can be additionally arranged on the first electrode sheet 221 or the second electrode sheet 222 for winding. In the electrode assembly 22, a plurality of winding layers can be arranged from inside to outside.

[0113] The buffer 23 can be a component capable of deforming to absorb energy when subjected to an external force. When the first electrode sheet 221 and / or the second electrode sheet 222 expands, the buffer 23 can absorb the expansion force by deforming and provide a space required for the expansion of the first electrode sheet 221 or the second electrode sheet 222, thereby playing a buffering role. Alternatively, the buffer 23 can be a structure or component capable of being compressed and restoring to its original state after the external force is removed, and the material of the buffer 23 does not chemically react with the electrolyte. The buffer 23 can be, but is not limited to, a polypropylene material, a polyethylene material, foam, a silica gel component or a rubber component, etc. As an example, the buffer 23 can be foam.

[0114] When the buffer 23 is of a compressible material, the compressible material of the buffer 23 can meet the following conditions: when the pressure is less than 0.2 Mpa, the compression amount is 0%; when the pressure is between 0.2 Mpa and 0.6 Mpa, the buffer 23 is gradually compressed, and the maximum compression amount is 50%; when the pressure is 0.8 Mpa, the compressible material reaches the maximum compression degree, and the compression amount can be more than 80%. Further, the thickness of the buffer 23 can be 0.5 mm to 3.0 mm.

[0115] The buffer 23 can be arranged in one winding layer or in two, three or any number of winding layers. When the buffer 23 is arranged in a plurality of winding layers, the buffer 23 can be arranged in the outermost winding layer, the intermediate winding layer, the innermost winding layer, between the outermost winding layer and the intermediate winding layer, between the intermediate winding layer and the innermost winding layer, etc., which is not specifically limited herein.

[0116] The buffer 23 can be arranged between the separator 223 and the first electrode sheet 221 of each winding layer, or between the separator 223 and the second electrode sheet 222, which is not specifically limited herein. As an example, referring to FIG. 4, the buffer 23 can be arranged between the separator 223 and the first electrode sheet 221.

[0117] It should be noted that in the above embodiment, the cross-sectional shape of the electrode assembly 22 perpendicular to the winding axis can be, but is not limited to, a cylindrical shape, a racetrack shape or a rectangular shape, etc., and accordingly, the shape of the shell assembly 21 can be, but is not limited to, a cylindrical shell, a square shell, etc., which is not specifically limited herein.

[0118] Since the electrode assembly 22 is in a jelly-roll shape, according to the above analysis, the electrode assembly 22 includes at least only the arc-shaped portion 2012, for example, the electrode assembly 22 is a cylindrical jelly-roll; or the electrode assembly 22 can include the arc-shaped portion 2012 and a non-arc-shaped portion (see the flat portion 2011 in FIG. 4), for example, the electrode assembly 22 is a racetrack-shaped jelly-roll. It can be understood that the buffer member 23 can be provided in the winding layer at the position of the arc-shaped portion 2012, or in the winding layer at the position of the non-arc-shaped portion, or in the winding layer at the positions of both the arc-shaped portion 2012 and the non-arc-shaped portion, which is not limited here.

[0119] The accommodation groove 224 can refer to an accommodation space with a certain formation and size formed on the first tab 221 or the second tab 222. The accommodation groove 224 can be a groove formed by a part structure dug out on the first tab 221 or the second tab 222 (see FIGS. 5 to 7), or can refer to a groove penetrating through in the thickness direction of the first tab 221 or the second tab 222, or can refer to a groove formed by the first tab 221 or the second tab 222 being partially disconnected (see FIGS. 4, 8, 9, 16 and 17), which is not specifically limited here.

[0120] It can be understood that, in the winding layer at the position of the buffer member 23, the accommodation groove 224 can be provided only on the first tab 221, or the accommodation groove 224 can be provided only on the second tab 222, or the first tab 221 and the second tab 222 can both be provided with the accommodation groove 224.

[0121] For example, if the buffer member 23 is located between the separation film 223 and the first tab 221, the first tab 221 can be provided with the accommodation groove 224, and the buffer member 23 can be directly installed in the accommodation groove 224, or the second tab 222 can be provided with the accommodation groove 224 (see FIG. 4), and the buffer member 23 can be placed in the accommodation groove 224 together with the separation film 223 at the position. If the buffer member 23 is located between the separation film 223 and the second tab 222, the second tab 222 can be provided with the accommodation groove 224, and the buffer member 23 can be directly installed in the accommodation groove 224 (see FIGS. 16 and 17), or the first tab 221 can be provided with the accommodation groove 224, and the buffer member 23 can be placed in the accommodation groove 224 together with the separation film 223 at the position.

[0122] It can be understood that at least part of the buffer member 23 protrudes from the accommodation groove 224, so that the buffer member 23 can contact the first tab 221 or the second tab 222 when the first tab 221 or the second tab 222 swells, thereby buffering the swelling force and providing the space required for swelling.

[0123] In the related art, the first electrode sheet and / or the second electrode sheet can swell during the cyclic swelling process, and the first electrode sheet and / or the second electrode sheet can swell more severely as the cycle number increases, eventually causing the electrode assembly to tightly contact the shell wall of the shell at both ends of the second direction Y, at which time a tensile force can be formed on the first electrode sheet and / or the second electrode sheet, and the tensile force of the outermost first electrode sheet and / or second electrode sheet can be more obvious and more prone to swelling and breaking. Referring to FIG. 4, the second direction Y can refer to the width direction of the cross section of the electrode assembly 22 perpendicular to the winding axis, or the width direction of the shell assembly 21.

[0124] In the above technical solution, since the buffer member 23 is arranged in at least one winding layer, the buffer member 23 can play a buffering role between the outer electrode sheet and the inner electrode sheet of the electrode assembly 22, can simultaneously provide swelling force release space for the inner electrode sheet and the outer electrode sheet, effectively alleviate the swelling force accumulation of the inner electrode sheet to the outer electrode sheet, be beneficial to reducing the tensile force of the outer electrode sheet, reduce the probability of breaking of the outer electrode sheet, and improve the reliability of the battery monomer 20. Moreover, since the buffer member 23 is arranged in the winding layer, the buffer member 23 can be assembled into the shell together with the electrode assembly 22, which can make the assembly of the buffer member 23 in the battery monomer 20 simpler, and be beneficial to reducing the overall assembly difficulty of the battery monomer 20.

[0125] Due to the need to provide space for the expansion of the pole pieces in the winding layer, the first pole piece 221 and the second pole piece 222 on both sides of the buffer piece 23 can form a certain gap. During the charging and discharging process of the battery monomer 20, metal ions in the positive pole piece are removed and need to migrate to the negative pole through the electrolyte. If the gap between the first pole piece 221 and the second pole piece 222 is large, the path of the metal ions removed by the positive pole in the migration process will be long and uneven, which may cause the local area to have too high a concentration of metal ions, and the speed of metal ion insertion at some positions of the negative pole cannot keep up with the speed. On the other hand, the large gap formed between the first pole piece 221 and the second pole piece 222 also affects the distribution of the electrolyte inside the battery monomer 20. The electrolyte may be locally excessive or insufficient at the gap. If the local electrolyte is excessive, it may cause abnormal ion conductivity in the local area, affecting the normal insertion or removal of metal ions; if the local electrolyte is insufficient, the migration resistance of the metal ions will increase, which is also easy to cause the accumulation and precipitation of metal ions on the negative electrode surface. That is, the formation of a certain gap between the first pole piece 221 and the second pole piece 222 may increase the risk of active metal ion precipitation in the electrode assembly 22, and the larger the gap, the higher the risk of active metal ion precipitation. As an example, if the battery monomer 20 is a lithium battery, there is a risk of lithium precipitation. In the technical solution of the present application, the battery monomer 20 can be but is not limited to a lithium battery, a nickel-hydrogen battery, a lead-acid battery, and the like, which is not specifically limited here.

[0126] In the above technical solution, by providing the accommodation groove 224 for the first pole piece 221 and / or the second pole piece 222 in the winding layer at the position of the buffer piece 23, part of the buffer piece 23 is located in the accommodation groove 224, and the accommodation groove 224 can provide part of the mounting space for the buffer piece 23, thereby reducing the gap between the first pole piece 221 and the second pole piece 222 at the position of the buffer piece 23, reducing the risk of metal ion precipitation of the positive pole piece between the first pole piece 221 and the second pole piece 222, and being beneficial to reducing the loss of active metal ions, improving the capacity retention rate, and also helping to make the electrode assembly 22 and the reaction kinetics more stable, reduce the battery internal resistance, improve the charging and discharging efficiency, and reduce the risk of causing irreversible damage to the internal structure of the battery, improve the stability of the electrode assembly 22, and further improve the overall reliability of the battery monomer 20.

[0127] In addition, since the accommodation groove 224 is formed by removing part of the first or second tab 221 or 222, the weight of the first or second tab 221 or 222 can be reduced, thereby reducing the overall weight of the battery cell 20, improving the volumetric energy density of the battery cell 20, and also enabling the electrode assembly 22 to have a larger size in the case of limited internal space of the casing assembly 21, which is also conducive to improving the volumetric energy density of the battery cell 20.

[0128] In some embodiments of the present application, referring to FIG. 5, the accommodation groove 224 includes a bottom groove wall 2241 and side groove walls 2242 arranged at least at two ends of the bottom groove wall 2241, and the buffer 23 is arranged at least on the bottom groove wall 2241.

[0129] In the above technical solution, the accommodation groove 224 can be a groove with a groove depth less than the thickness of the first or second tab 221 or 222, so that the accommodation groove 224 has a bottom groove wall 2241. The side groove walls 2242 can be arranged at two ends, three ends or four ends of the bottom groove wall 2241. For example, referring to FIG. 5, the accommodation groove 224 can penetrate the first or second tab 221 or 222 along the third direction Z of FIG. 3, so that the bottom groove wall 2241 is provided with the side groove walls 2242 at both ends of the second direction Y. For another example, the accommodation groove 224 penetrates the first or second tab 221 or 222 at one end along the third direction Z, so that the bottom groove wall 2241 is provided with the side groove walls 2242 at both ends of the second direction Y and the other end of the third direction Z. For another example, the accommodation groove 224 is a rectangular groove opened on the first or second tab 221 or 222, so that the bottom groove wall 2241 is provided with the side groove walls 2242 at both ends of the second direction Y and both ends of the third direction Z.

[0130] The “buffer 23 is arranged at least on the bottom groove wall 2241” means that the buffer 23 can be fixed on the bottom groove wall 2241, or the buffer 23 is fixed on both the bottom groove wall 2241 and the side groove wall 2242.

[0131] In the above technical solution, the first or second tab 221 or 222 can form the accommodation groove 224 by being partially cut in the thickness direction, which can not only provide a mounting position for the buffer 23 and reduce the gap between the first and second tabs 221 and 222, but also ensure the integrity of the first or second tab 221 or 222 at the position of the buffer 23, which is conducive to winding the first and second tabs 221 and 222 and the separator 223 into a core, reduces the difficulty of forming the core, and thus improves the quality of the core. The first or second tab 221 or 222 is partially cut to form the accommodation groove 224, which is also conducive to positioning the buffer 23 before winding, can improve the position accuracy of the buffer 23 in the winding layer, enhances the buffering effect of the buffer 23 on the expected position of the electrode assembly 22, and reduces the risk of swelling and fracture of the outer tab.

[0132] In some embodiments of the present application, referring to FIG. 6, the first tab 221 and the second tab 222 each include a current collector 2201 and an active material layer 2202 coated on the surface of the current collector 2201, and the accommodation groove 224 is arranged on the active material layer 2202.

[0133] One of the first tab 221 and the second tab 222 can be an anode tab (negative electrode tab), and the other can be a cathode tab (positive electrode tab). For the cathode tab, the current collector 2201 can refer to a positive electrode current collector, and the active material layer 2202 can refer to a positive electrode active material layer coated on the surface of the positive electrode current collector. For the anode tab, the current collector 2201 can refer to a negative electrode current collector, and the active material layer 2202 can refer to a negative electrode active material layer coated on the surface of the negative electrode current collector. The explanations of the positive electrode current collector, the positive electrode active material layer, the negative electrode current collector, and the negative electrode active material layer can be referred to the foregoing, and will not be described here.

[0134] Taking the first tab 221 provided with the accommodation groove 224 as an example, referring to FIG. 6, the accommodation groove 224 can be arranged on the active material layer 2202. Wherein, referring to the foregoing, in the thickness direction of the first tab 221, the depth of the accommodation groove 224 can be less than the thickness of the active material layer 2202, that is, the bottom groove wall 2241 of the accommodation groove 224 is located in the active material layer 2202, or the depth of the accommodation groove 224 is equal to the thickness of the active material layer 2202, and the bottom groove wall 2241 of the accommodation groove 224 is just located on the current collector 2201.

[0135] In the above technical solution, by arranging the accommodation groove 224 on the active material layer 2202, the thickness of the current collector 2201 can be kept consistent all the time, which is conducive to ensuring the integrity of the current collector 2201, and the current collector 2201 can have higher strength, which is conducive to winding the first tab 221 and the second tab 222 into a core, improving the quality of the core, and further improving the reliability of the whole electrode assembly 22.

[0136] In some embodiments of the present application, referring to FIG. 7, the first tab 221 and the second tab 222 each include a current collector 2201 and an active material layer 2202 coated on the surface of the current collector 2201, and the accommodation groove 224 is arranged on the current collector 2201 and penetrates through the active material layer 2202.

[0137] Taking the first tab 221 provided with the accommodation groove 224 as an example, referring to FIG. 7, the accommodation groove 224 can also be arranged on the current collector 2201 and penetrates through the active material layer 2202. That is, in the thickness direction of the first tab 221, the depth of the accommodation groove 224 is less than the sum of the thicknesses of the current collector 2201 and the active material layer 2202.

[0138] In the technical solution, the accommodation groove 224 is arranged on the current collector 2201 and penetrates the active material layer 2202, so that the accommodation groove 224 has a large groove depth and can provide a larger accommodation space, which is beneficial to make the gap between the first pole piece 221 and the second pole piece 222 smaller, thereby further reducing the risk of metal ion precipitation in the winding layer at the position of the buffer 23, improving the reliability of the electrode assembly 22, and further improving the reliability of the battery cell 20.

[0139] In some embodiments of the present application, referring to FIG. 4, the accommodation groove 224 is arranged on the first pole piece 221 and penetrates the first pole piece 221 along the thickness direction of the first pole piece 221, or the accommodation groove 224 is arranged on the second pole piece 222 and penetrates the second pole piece 222 along the thickness direction of the second pole piece 222.

[0140] Referring to FIG. 4, the "thickness direction of the first pole piece 221" and the "thickness direction of the second pole piece 222" can refer to the size of the pole piece at the position of the buffer 23 in the first direction X in FIG. 4. The first direction X can refer to the length direction of the cross section of the electrode assembly 22 perpendicular to the winding axis, or the length direction of the shell assembly 21.

[0141] In the technical solution, the accommodation groove 224 completely penetrates the first pole piece 221 or the second pole piece 222 at the position, so that the accommodation groove 224 has a larger groove depth, thereby further reducing the gap between the first pole piece 221 and the second pole piece 222, and further reducing the risk of metal ion precipitation in the winding layer at the position of the buffer 23, improving the reliability of the electrode assembly 22, and further improving the reliability of the battery cell 20 as a whole. The above-mentioned solution can also make the internal structure of the electrode assembly 22 more compact, so that the electrode assembly 22 can have a larger size in the shell assembly 21, thereby improving the volumetric energy density of the battery cell 20.

[0142] In some embodiments of the present application, referring to FIGS. 3 and 4, the electrode assembly 22 includes a main body part 201 and a tab 202 connected to each other, the main body part 201 includes a flat part 2011 and an arc-shaped part 2012 connected to each other, and the accommodation groove 224 is arranged on the arc-shaped part 2012.

[0143] The tab 202 can refer to a metal structure in the electrode assembly 22 for leading out current. Referring to the above, in the electrode assembly 22, the first electrode tab 221 in the plurality of winding layers can be partially extended and gathered to form a tab 202, and the second electrode tab 222 in the plurality of winding layers can also be partially extended and gathered to form another tab 202. According to the polarity difference between the first electrode tab 221 and the second electrode tab 222, the polarity of the tabs 202 formed by the two is also different. As an example, the first electrode tab 221 can be an anode tab, and correspondingly, the first electrode tab 221 forms a negative tab; the second electrode tab 222 can be a cathode tab, and correspondingly, the second electrode tab 222 forms a positive tab.

[0144] The body part 201 can refer to the main structure of the electrode assembly 22 excluding the tab 202.

[0145] The "body part 201 includes the connected flat part 2011 and the arc-shaped part 2012" can be understood as the body part 201 can have a flat structure and an arc-shaped part. Among them, the flat part 2011 can be connected with the arc-shaped part 2012 at one end, or both ends are connected with the arc-shaped part 2012, which is not specifically limited here.

[0146] For example, referring to FIG. 4, the shape of the body part 201 in the cross section perpendicular to the winding direction can be a racetrack shape, the flat part 2011 extends along the first direction X, and the flat part 2011 is provided with the arc-shaped part 2012 at both ends of the first direction X. For another example, the shape of the body part 201 in the cross section perpendicular to the winding direction can also be a rectangle, and the arc-shaped part 2012 is located at the four corners of the rectangle, and the flat part 2011 is located at the four edges of the rectangle.

[0147] In the technical solution, the arc-shaped portion 2012 of the main body portion 201 has an arc-shaped structure and a curvature change, and stress concentration is more likely to occur during the cyclic expansion of the electrode assembly 22. The arc-shaped portion 2012 bears greater expansion tensile force than other positions of the main body portion 201. The receiving groove 224 is arranged on the arc-shaped portion 2012, and the buffer 23 is correspondingly arranged on the arc-shaped portion 2012. When the first electrode tab 221 and / or the second electrode tab 222 at the position corresponding to the arc-shaped portion 2012 expand, the buffer 23 can be compressed to absorb energy, reduce the expansion tensile force, and provide space required for the expansion of the first electrode tab 221 and / or the second electrode tab 222. This is beneficial to reduce the risk of fracture of the electrode tab at the position of the arc-shaped portion 2012, and thus reduce the probability of overall expansion fracture of the electrode assembly 22 and improve the reliability of the battery monomer 20. Since the receiving groove 224 is arranged on the arc-shaped portion 2012, the size of the receiving groove 224 around the winding direction of the electrode assembly 22 is small, and the buffer 23 is arranged in the receiving groove 224. Therefore, the setting area of the buffer 23 in the main body portion 201 can be reduced, the material can be saved, the cost can be reduced, the volume of the buffer 23 can be reduced, the internal space of the shell assembly 21 can be saved, and the weight of the buffer 23 can be reduced. Thus, the volume energy density of the battery monomer 20 can be improved.

[0148] In some embodiments of the present application, referring to FIG. 4, the opposite ends of the flat portion 2011 are provided with arc-shaped portions 2012, and the two arc-shaped portions 2012 are each provided with a receiving groove 224 and a buffer 23.

[0149] Referring to FIG. 4, the opposite ends of the flat portion 2011 can refer to the two ends along the first direction X. The opposite ends of the flat portion 2011 are provided with arc-shaped portions 2012, so that the cross-sectional shape of the electrode assembly 22 perpendicular to the winding axis is a racetrack shape. This kind of winding core structure is relatively simple, and the manufacturing process and production cost can be reduced.

[0150] In the technical solution, the two arc-shaped portions 2012 are each provided with a receiving groove 224 and a buffer 23. The buffer 23 can provide space required for the expansion of the arc-shaped portion 2012 at the opposite ends of the flat portion 2011, respectively. The two buffers 23 together can provide greater expansion release space, and can provide timely buffering effect and space required for the expansion of each arc-shaped portion 2012. This can reduce the risk of expansion fracture of the outer electrode tab at the position of the arc-shaped portion 2012, further improve the reliability of the electrode assembly 22, and thus improve the reliability of the battery monomer 20.

[0151] In some embodiments of the present application, the receiving grooves 224 and the buffers 23 of the two arc-shaped portions 2012 are arranged in the same winding layer or different winding layers.

[0152] In the technical solution, the accommodating groove 224 and the buffer 23 of the two arc-shaped portions are arranged in the same winding layer, so that the buffer 23 can buffer the stress generated in the layer, can timely absorb and disperse the stress, effectively reduces the risk of stress concentration in a local area, better protects the first pole piece 221 or the second pole piece 222 in the layer, reduces the risk of fracture of the pole piece in the layer, and helps the consistency of the winding layer in the layer, which is beneficial to improve the overall consistency of the battery monomer 20. The accommodating groove 224 and the buffer 23 of the two arc-shaped portions 2012 are arranged in different winding layers, so that the stress generated in the electrode assembly 22 can be buffered from multiple aspects. Since the stress inside the electrode assembly 22 is a complex system, the stresses from different winding layers will superimpose and affect each other. By arranging the buffers 23 in different winding layers, the stress of each layer can be comprehensively buffered, the stress accumulation and transmission in the electrode assembly 22 can be reduced, the entire electrode assembly 22 can be better protected, and the overall reliability of the battery monomer 20 can be improved.

[0153] In some embodiments of the present application, referring to FIG. 4, the accommodating groove 224 and the buffer 23 are arranged centrally on the arc-shaped portion 2012 in the winding direction F1 of the arc-shaped portion 2012.

[0154] The winding direction F1 can be seen from FIG. 4, and the “accommodating groove 224 and the buffer 23 are arranged centrally on the arc-shaped portion 2012” can be understood as that the center of the buffer 23 is on the half-arc length dividing line of the arc-shaped portion 2012 (see FIG. 4 for details).

[0155] In the technical solution, since the arc-shaped portion 2012 of the electrode assembly 22 itself has a stress concentration problem, and the middle position of the arc-shaped portion 2012 is a relatively large stress point, the accommodating groove 224 and the buffer 23 are arranged centrally on the arc-shaped portion 2012, thereby targetedly relieving the stress concentration phenomenon of the arc-shaped portion 2012, which is beneficial to the buffer 23 to better absorb and disperse the stress and reduce the stress size borne by the middle position of the arc-shaped portion 2012. Secondly, the central arrangement of the buffer 23 on the arc-shaped portion 2012 is also beneficial to balance the stress distribution inside the entire electrode assembly 22, can diffuse the stress originally concentrated in the middle position of the arc-shaped portion 2012 to the periphery, so that the stress of each part of the electrode assembly 22 is more uniform, thereby reducing the risk of swelling and fracture of the outer pole piece caused by local large stress, and is beneficial to improve the reliability of the electrode assembly 22 and further improve the overall reliability of the battery monomer 20.

[0156] In some embodiments of the present application, referring to FIG. 17, a plurality of buffers 23 are arranged in the accommodating groove 224, the plurality of buffers 23 are arranged at intervals along the winding direction F1 of the arc-shaped portion 2012, and are symmetrically arranged.

[0157] The number of the buffer pieces 23 arranged on the arc-shaped portion 2012 can be, but is not limited to, two, three, four, and the like. As an example, referring to FIG. 17, the buffer pieces 23 can be arranged as two on the arc-shaped portion 2012.

[0158] In the above technical solution, the above scheme can further reduce the size of the buffer piece 23 in the winding direction F1, thereby further reducing the volume of the buffer piece 23, thereby further saving space, which is conducive to improving the volume ratio of the electrode assembly 22 in the shell assembly 21, and further reducing the weight of the buffer piece 23, thereby reducing the overall weight of the battery monomer 20, thereby further improving the volume energy density of the battery monomer 20.

[0159] In some embodiments of the present application, referring to FIG. 17, the buffer piece 23 has a center surface in the winding direction F1 of the arc-shaped portion 2012, and two buffer pieces 23 are arranged in the accommodating groove 224, and the center surface of the buffer piece 23 is close to or coincides with the quarter division line 2012a of the arc length of the arc-shaped portion 2012.

[0160] The "center surface of the buffer piece 23" can refer to a plane that equally divides the buffer piece 23 along the winding direction F1. Referring to FIG. 17, the center surface of the buffer piece 23 coincides with the quarter division line 2012a of the arc length of the arc-shaped portion 2012.

[0161] The "quarter division line 2012a of the arc length of the arc-shaped portion 2012" can refer to a division line that cuts one quarter of the arc length of the arc-shaped portion 2012 from the end of the arc-shaped portion 2012.

[0162] The "center surface of the buffer piece 23 and the quarter division line 2012a of the arc length of the arc-shaped portion 2012 are close to or coincide", which can be understood as that the center surface of the buffer piece 23 can be arranged next to the quarter division line 2012a of the arc length of the arc-shaped portion 2012, or the center surface of the buffer piece 23 coincides with the quarter division line 2012a of the arc length of the arc-shaped portion 2012, that is, the quarter division line 2012a of the arc length of the arc-shaped portion 2012 is located on the center surface of the buffer piece 23.

[0163] In the technical solution, the position of the quarter division line 2012a of the arc length of the arc-shaped portion 2012 is close to the two end edge positions of the arc-shaped portion 2012, and the two end edge positions of the arc-shaped portion 2012 are key points of stress dispersion. By making the center surface of the buffer 23 close to or coincide with the quarter division line 2012a, the buffer 23 can better adapt to the transmission direction of the stress, disperse the stress to a wider area, and reduce the degree of local stress concentration. When the electrode assembly 22 is bent and deformed, the two end positions of the arc-shaped portion 2012 first bear the bending stress. The above scheme can effectively absorb and buffer the bending stress, reduce the risk of damage to the internal structure of the electrode assembly 22 due to excessive bending, improve the reliability of the electrode assembly 22, and further improve the overall reliability of the battery monomer 20. Moreover, the above scheme can also make the first electrode sheet 221 or the second electrode sheet 222 form a certain gap (see FIG. 17) at the middle position of the arc-shaped portion 2012 in the winding layer where the buffer 23 is located, which can provide the space required for the middle position of the arc-shaped portion 2012 to expand, is also conducive to reducing the probability of stress concentration at the middle position of the arc-shaped portion 2012, and can improve the reliability of the battery monomer 20.

[0164] On the other hand, since the arc-shaped portion 2012 has an arc-shaped structure and the shell assembly 21 generally has a square shape, a certain space will be formed between the arc-shaped portion 2012 at both ends of the winding direction F1 and the shell assembly 21. By making the center surface of the two buffers 23 close to or coincide with the quarter division line 2012a of the arc length of the arc-shaped portion 2012, the space formed between the arc-shaped portion 2012 and the shell assembly 21 can be fully utilized to arrange the buffer 23, thereby reducing the probability of increasing the size of the electrode assembly 22 in the first direction X and the second direction Y due to the arrangement of the buffer 23 in the winding layer (see FIG. 17), improving the space ratio of the electrode assembly 22 in the shell assembly 21, and making the internal structure of the battery monomer 20 more compact, which is conducive to making the battery monomer 20 have a higher volumetric energy density.

[0165] In some embodiments of the present application, the center surface of the buffer 23 and the quarter division line 2012a of the arc length of the arc-shaped portion 2012 are close to each other, and the included angle between the center surface of the buffer 23 and the quarter division line 2012a of the arc length of the arc-shaped portion 2012 is θ, where 0 degrees ≤ θ ≤ 20 degrees.

[0166] A quarter division line 2012a of the arc length of the arc-shaped portion 2012 can be referred to FIG. 17. The center plane of the buffer 23 can be located on one side of the quarter division line 2012a close to the middle of the arc-shaped portion 2012, or the center plane of the buffer 23 can be located on one side of the quarter division line 2012a close to the straight portion 2011. In the above two examples, the included angle θ between the center plane of the buffer 23 and the quarter division line 2012a of the arc length of the arc-shaped portion 2012 satisfies 0 degrees ≤ θ ≤ 20 degrees.

[0167] Wherein, θ can be but not limited to 0 degrees, 1 degree, 3 degrees, 5 degrees, 8 degrees, 10 degrees, 12 degrees, 13 degrees, 14 degrees, 15 degrees, 16 degrees, 17 degrees, 18 degrees, 19 degrees, 20 degrees, etc.

[0168] In the above technical solution, by setting the included angle between the center plane of the buffer 23 and the quarter division line 2012a of the arc length of the arc-shaped portion 2012 in the above range, more choices can be provided for the setting of the buffer 23, which is conducive to reducing the manufacturing difficulty and reducing the cost.

[0169] In some embodiments of the present application, referring to FIG. 4, in the winding layer where the buffer 23 is located, the accommodation groove 224 penetrates the first electrode sheet 221 and / or the second electrode sheet 222 along the thickness direction of the winding layer and the winding axis of the electrode assembly 22, and the first end portion 2203 and the second end portion 2204 are formed on the first electrode sheet 221 or the second electrode sheet 222.

[0170] That is, the first electrode sheet 221 and / or the second electrode sheet 222 can form the accommodation groove 224 by partially disconnecting, and in the winding layer where the buffer 23 is located, only the first electrode sheet 221 can be partially disconnected to form the accommodation groove 224, one end of the disconnected portion of the first electrode sheet 221 is the first end portion 2203, and the other end is the second end portion 2204; only the second electrode sheet 222 can be partially disconnected to form the accommodation groove 224, one end of the disconnected portion of the second electrode sheet 222 is the first end portion 2203, and the other end is the second end portion 2204; or both the first electrode sheet 221 and the second electrode sheet 222 can be partially disconnected to form the accommodation groove 224, one end of the disconnected portion of the first electrode sheet 221 and the second electrode sheet 222 is the first end portion 2203, and the other end is the second end portion 2204.

[0171] Since the first tab 221 or the second tab 222 forms the accommodation groove 224 in a partially disconnected manner, in the winding layer at the position of the buffer 23, one side of the buffer 23 has a tab, and the other side of the buffer 23 does not have a tab. For example, referring to FIG. 4, the second tab 222 is partially disconnected to form the accommodation groove 224, and in the winding layer at the position of the buffer 23, the buffer 23 is arranged on the first tab 221, and the other side of the buffer 23 away from the first tab 221 does not have the second tab 222. The probability of chemical reaction at both ends of the buffer 23 in the thickness direction is low, and the probability of metal ion migration is also low. Although there is still a gap between the first tab 221 and the second tab 222 at both ends of the buffer 23 in the winding direction F1, the size of the gap between the first tab 221 and the second tab 222 in the winding direction F1 of the electrode assembly 22 is small, and since the first end 2203 and the second end 2204 formed on the first tab 221 are away from the buffer 23, the size of the gap between the first tab 221 and the second tab 222 in the thickness direction of the winding layer is also small, so the risk of metal ion precipitation of the positive electrode tab is also low.

[0172] In the above technical solution, the first tab 221 and / or the second tab 222 are formed by partially disconnecting to form the accommodation groove 224. This can reduce the manufacturing process difficulty of the accommodation groove 224, enhance the manufacturability, reduce the cost, and also improve the forming quality of the accommodation groove 224. Moreover, the above solution can also reduce the size of the gap formed between the first tab 221 and the second tab 222 in the winding direction F1 of the electrode assembly 22 and in the thickness direction of the winding layer, further reduce the risk of metal ion precipitation in the winding layer at the position of the buffer 23, and further improve the reliability of the battery monomer 20.

[0173] In some embodiments of the present application, referring to FIGS. 4, 8 and 9, the electrode assembly 22 includes the main body part 201 and the tab 202 connected to each other, the main body part 201 includes the flat part 2011 and the arc-shaped part 2012, the arc-shaped part 2012 is connected to both ends of the flat part 2011 in the first direction X, and the first end 2203 and the second end 2204 are arranged on the arc-shaped part 2012.

[0174] Referring to FIG. 4, each arc-shaped portion 2012 can be provided with a first end portion 2203 and a second end portion 2204, that is, the first pole piece 221 or the second pole piece 222 of each arc-shaped portion 2012 is formed with a cut-off area, which can refer to a space area formed between the first end portion 2203 and the second end portion 2204 in the first pole piece 221 or the second pole piece 222. Referring to FIG. 8, the first end portion 2203 and the second end portion 2204 can be respectively arranged on the two arc-shaped portions 2012, that is, the size of the cut-off area in the winding direction F1 of the winding layer is large, and the two arc-shaped portions 2012 can share one accommodating groove 224, and the part of the cut-off area where the two arc-shaped portions 2012 are located is used to accommodate the buffer member 23. Referring to FIG. 9, the first end portion 2203 and the second end portion 2204 are arranged on one of the two arc-shaped portions 2012 at the same time, at this time, compared with the example of FIG. 8, the size of the cut-off area is larger, and the two arc-shaped portions 2012 can also form the accommodating groove 224 at the positions where the two arc-shaped portions 2012 are located. In the above embodiment, this is not specifically limited.

[0175] In the above technical solution, the first end portion 2203 and the second end portion 2204 are arranged on the arc-shaped portion 2012, so that the accommodating groove 224 is located on the arc-shaped portion 2012, so that the buffer member 23 can be arranged on the arc-shaped portion 2012, which can play a buffering role at the position where the stress of the electrode assembly 22 is concentrated, reduce the expansion tensile force of the first pole piece 221 or the second pole piece 222 at the position where the arc-shaped portion 2012 is located, and further reduce the probability of expansion rupture of the outer pole piece, which is beneficial to reduce the risk of expansion rupture of the whole electrode assembly 22 and improve the reliability of the battery monomer 20.

[0176] In some embodiments of the present application, referring to FIG. 4, the arc-shaped portion 2012 has a connecting line 2012b connecting the straight portion 2011, and the distance between the first end portion 2203 and the second end portion 2204 and the adjacent connecting line 2012b in the winding direction F1 of the arc-shaped portion 2012 is less than or equal to one quarter of the arc length of the arc-shaped portion 2012.

[0177] The connecting line 2012b can refer to a virtual line formed at the connecting position of the arc-shaped portion 2012 and the straight portion 2011, and the connecting line 2012b is not a real line on the arc-shaped portion 2012. For the convenience of understanding, referring to FIG. 4, the connecting line 2012b can be represented by a dashed line in the figure.

[0178] The distance between the first end portion 2203 or the second end portion 2204 and the adjacent connecting line 2012b is less than or equal to one-fourth of the arc length of the arc portion 2012. It can be understood that, due to the large thickness of the buffer 23, the buffer 23 can play a buffering role and provide space for the expansion of the first pole piece 221 or the second pole piece 222. Therefore, when the buffer 23 is arranged in the winding layer, a large gap is formed. However, since the electrode assembly 22 is a winding core, the farther the gap in the winding layer is from the buffer 23, the smaller the size of the gap in the thickness direction of the winding layer is. By arranging the distance between the first end portion 2203 and the adjacent connecting line 2012b to be less than or equal to one-fourth of the arc length of the arc portion 2012, or the distance between the second end portion 2204 and the adjacent connecting line 2012b to be less than or equal to one-fourth of the arc length of the arc portion 2012, the distance between the first end portion 2203 and the second end portion 2204 and the buffer 23 is farther, and the size of the gap between the first pole piece 221 and the second pole piece 222 in the thickness direction of the winding layer is smaller. In this way, the migration path length of the metal ions released from the positive pole piece can be reduced, the risk of excessive metal ion concentration in the local area can be reduced, the uneven distribution of the electrolyte can be alleviated, the migration resistance of the metal ions can be reduced, and the risk of metal ion precipitation can be reduced.

[0179] In the above technical solution, the distance between the first end portion 2203 and the second end portion 2204 and the buffer 23 is appropriate, and the size of the gap between the first pole piece 221 and the second pole piece 222 in the winding direction and the thickness direction of the winding layer is further reduced. The condition of the gap between the first pole piece 221 and the second pole piece 222 is effectively improved, which is beneficial to reducing the probability of metal ion precipitation when the buffer 23 is arranged in the winding layer. The stability of the electrode assembly 22 can be improved, and the reliability of the battery cell 20 can be improved.

[0180] In some embodiments of the present application, referring to FIG. 4, the distance between the first end portion 2203 or the second end portion 2204 and the buffer 23 is greater than or equal to 3 mm.

[0181] Referring to FIG. 4, the distance between the first end portion 2203 and the buffer 23 can be L1, where L1 can be, but is not limited to, 3 mm, 5 mm, 6 mm, 7 mm, 10 mm, 12 mm, 14 mm, 16 mm, 20 mm, 30 mm, and the like. As the size of the electrode assembly 22 increases, the value of L1 can be increased accordingly, but L1 is always greater than or equal to 3 mm. If the distance L1 between the first end portion 2203 and the buffer 23 is less than 3 mm, the portion of the first tab 221 or the second tab 222 extending into the arc-shaped portion 2012 is relatively long. Referring to FIG. 4, since the buffer 23 has a certain thickness, the closer the first end portion 2203 is to the buffer 23, the larger the size of the gap between the second tab 222 and the first tab 221 in the thickness direction of the winding layer. The effect of improving the gap between the first tab 221 and the second tab 222 is poor, and the metal ion precipitation in the winding layer is also poor. Similarly, the case of the second end portion 2204 is the same as that of the first end portion 2203, which will not be described here.

[0182] In the above technical solution, by setting the distance between the first end portion 2203 or the second end portion 2204 and the buffer 23 within the above range, the size of the gap formed between the first tab 221 and the second tab 222 in the winding direction and the thickness direction of the winding layer can be reduced to a more optimal value. The effect of improving the gap between the first tab 221 and the second tab 222 is better, and the effect of reducing metal ion precipitation is also better. This is conducive to further improving the stability of the electrode assembly 22 and improving the reliability of the battery monomer 20.

[0183] In some embodiments of the present application, referring to FIG. 4, the first tab 221 or the second tab 222 of the two arc-shaped portions 2012 is provided with a receiving groove 224, and is provided with a first end portion 2203 and a second end portion 2204.

[0184] In the above technical solution, the sum of the sizes of the disconnected portions of the first tab 221 or the second tab 222 in the winding direction F1 of the winding layer is relatively small. This can reduce the size of the disconnected area of the first tab 221 and / or the second tab 222, reduce the cutting loss of the tab, that is, reduce the capacity loss. This is conducive to maintaining a relatively high capacity of the battery monomer 20 as a whole, so that the battery monomer 20 has a higher volumetric energy density.

[0185] In some embodiments of the present application, referring to FIG. 8, the plurality of winding layers includes a first winding layer 203 and a second winding layer 204 connected to each other, the first winding layer 203 includes a first arc-shaped portion 2031 located at one end of the first direction X, the second winding layer 204 includes a first straight portion 2041 and a second arc-shaped portion 2042 located at the other end of the first direction X, the first straight portion 2041 connects the second arc-shaped portion 2042 and the first arc-shaped portion 2031, the first arc-shaped portion 2031 and the second arc-shaped portion 2042 are both provided with a buffer 23, the accommodation groove 224 extends along the first arc-shaped portion 2031, the first straight portion 2041 and the second arc-shaped portion 2042, the first end portion 2203 is arranged in the first arc-shaped portion 2031 and located at a side of the buffer 23 away from the first straight portion 2041, and the second end portion 2204 is arranged in the second arc-shaped portion 2042 and located at a side of the buffer 23 away from the first straight portion 2041.

[0186] The first winding layer 203 and the second winding layer 204 can refer to two adjacent winding layers in the plurality of winding layers, the first arc-shaped portion 2031 can be the outermost winding layer, the second winding layer 204 can be the innermost winding layer, and the first winding layer 203 and the second winding layer 204 can also be winding layers in the middle position, which is not specifically limited here.

[0187] In the above technical solution, the part of the first pole piece 221 or the second pole piece 222 located at the first arc-shaped portion 2031, the first straight portion 2041 and the second arc-shaped portion 2042 is cut to form the accommodation groove 224, which makes the first pole piece 221 and the second pole piece 222 form a gap only at a side away from the first straight portion 2041, so that the position where the first pole piece 221 and the second pole piece 222 can form a gap is relatively small, which can reduce the size of the gap in the winding direction F1 of the winding layer, reduce the probability of metal ion precipitation of the electrode assembly 22, and improve the reliability of the battery monomer 20. Moreover, the above solution can form the accommodation groove 224 at both ends of the first direction X of the straight portion 2011 after winding under the condition that the first pole piece 221 or the second pole piece 222 is cut only once, which is beneficial to reduce the manufacturing process of the electrode assembly 22 and the assembly composed of the buffer 23, thereby reducing the manufacturing difficulty, improving the manufacturability, improving the work efficiency, and improving the forming quality of the electrode assembly 22 and the assembly composed of the buffer 23, thereby improving the reliability of the battery monomer 20.

[0188] In some embodiments of the present application, referring to FIG. 9, the plurality of winding layers include a first winding layer 203 and a second winding layer 204 connected to each other, the first winding layer 203 includes a first arc-shaped portion 2031 located at one end of the first direction X, the second winding layer 204 includes a first flat portion 2041, a second arc-shaped portion 2042, a second flat portion 2043, and a third arc-shaped portion 2044, the first flat portion 2041 connects the first arc-shaped portion 2031 and the second arc-shaped portion 2042, the second flat portion 2043 connects the second arc-shaped portion 2042 and the third arc-shaped portion 2044, the first arc-shaped portion 2031 and the second arc-shaped portion 2042 are both provided with a buffer 23, the accommodation groove 224 extends along the first arc-shaped portion 2031, the first flat portion 2041, the second arc-shaped portion 2042, the second flat portion 2043, and the third arc-shaped portion 2044, the first end portion 2203 is arranged in the first arc-shaped portion 2031 and located at a side of the center of the first arc-shaped portion 2031 away from the first flat portion 2041, and the second end portion 2204 is arranged in the third arc-shaped portion 2044 and located at a side of the center of the third arc-shaped portion 2044 close to the second flat portion 2043.

[0189] In the above technical solution, the part of the first pole piece 221 or the second pole piece 222 located at the first arc-shaped portion 2031, the first flat portion 2041, the second arc-shaped portion 2042, the second flat portion 2043, and the third arc-shaped portion 2044 is cut to form the accommodation groove 224, which makes the first pole piece 221 and the second pole piece 222 form the gap only at the side away from the first flat portion 2041 and the second arc-shaped portion 2042, so that the position where the first pole piece 221 and the second pole piece 222 can form the gap is less, which can further reduce the size of the gap in the winding direction F1 of the winding layer, reduce the probability of metal ion precipitation of the electrode assembly 22, and improve the reliability of the battery monomer 20. Moreover, the above solution can form the accommodation groove 224 at both ends of the first direction X of the flat portion 2011 after winding under the condition that the first pole piece 221 or the second pole piece 222 is cut only once, which is conducive to reducing the manufacturing process of the electrode assembly 22 and the assembly composed of the buffer 23, thereby reducing the manufacturing difficulty, improving the manufacturability, improving the work efficiency, and improving the forming quality of the electrode assembly 22 and the assembly composed of the buffer 23, thereby improving the reliability of the battery monomer 20.

[0190] In some embodiments of the present application, referring to FIG. 9, the first end portion 2203 and the second end portion 2204 are staggered with each other in the winding direction F1 of the third arc-shaped portion 2044.

[0191] Since the first end 2203 is located on the first arc-shaped portion 2031, and the second end 2204 is located on the third arc-shaped portion 2044 which is on the same side of the flat portion 2011, if the first end 2203 and the second end 2204 are located on the same longitudinal extension line of the first arc-shaped portion 2031, for example, as shown in FIG. 9, stress concentration may occur between the second pole piece 222 between the first end 2203 and the second end 2204, and the second pole piece 222 is more likely to be broken under the action of shear force, for example, the second pole piece 222 is more likely to be broken under the action of pressure during the flattening process of the electrode assembly 22 after winding. Moreover, the above-mentioned situation may also increase the resistance of the metal ion migration process, affect the extraction or intercalation of metal ions, and further affect the reliability of the electrode assembly 22.

[0192] In the above technical solution, the first end 2203 and the second end 2204 are arranged staggered in the winding direction F1 of the third arc-shaped portion 2044, so that the first end 2203 and the second end 2204 can have a certain distance, reducing the probability of stress concentration of the pole piece between the first end 2203 and the second end 2204, and further reducing the risk of breakage or damage of the pole piece between the first end 2203 and the second end 2204, which can improve the reliability of the electrode assembly 22, and further improve the reliability of the battery cell 20.

[0193] In some embodiments of the present application, referring to FIG. 4, the first pole piece 221 is an anode piece, the second pole piece 222 is a cathode piece, and the accommodation groove 224 is provided.

[0194] In the electrode assembly 22, for example, in a common lithium ion battery, the material of the cathode piece, such as ternary material, lithium cobaltate, etc., may contain relatively valuable metal elements such as cobalt and nickel, and the material of the anode piece is usually graphite, etc., which is relatively low in price. In the above technical solution, since the manufacturing cost of the cathode piece is relatively high, by cutting the cathode piece to form the accommodation groove 224, the amount of material of the cathode piece in the electrode assembly 22 can be reduced, which is beneficial to reduce the cost.

[0195] In some embodiments of the present application, referring to FIG. 10, the side of the buffer piece 23 away from the first pole piece 221 is provided with an adhesive piece 24, and the two ends of the adhesive piece 24 exceed the buffer piece 23 in the winding direction F1 of the electrode assembly 22, and are bonded with the first pole piece 221.

[0196] The adhesive piece 24 can refer to a sheet-shaped component with adhesive function. The material of the adhesive piece 24 can be, but is not limited to, organic polymer or rubber, etc. The organic polymer can include, but is not limited to, acrylate, polyurethane, etc. The rubber can include, but is not limited to, natural rubber or synthetic rubber, etc. As an example, the adhesive piece 24 can be an adhesive tape.

[0197] The "two ends of the bonding piece 24 protrude beyond the buffer piece 23" can be understood as, in the winding direction F1, the size of the bonding piece 24 is greater than the size of the buffer piece 23, and the two ends protrude relative to the two ends of the buffer piece 23, and the buffer piece 23 can be fixed on the first pole piece 221 by the bonding piece 24 and the first pole piece 221.

[0198] In addition, since the cathode sheet (positive pole sheet) is usually composed of a positive active material, a conductive agent, and a binder, coated on a current collector (usually an aluminum foil), the binder used by the cathode sheet is usually more prone to intermolecular interaction with the adhesive and the like bonding piece, which is conducive to the bonding of the buffer piece 23. Moreover, the active material and the conductive agent of the cathode sheet are evenly distributed in particles, and the surface is relatively flat, so the contact surface between the buffer piece 23 and the cathode sheet is large, which is conducive to the better filling of the adhesive and the like in the gap between the buffer piece 23 and the cathode sheet. That is, the second pole piece 222 is a cathode sheet, which can facilitate the fixing of the buffer piece 23 on the second pole piece 222 by bonding.

[0199] In the above technical solution, the bonding piece 24 is a separate component, which can be mass-produced, and is conducive to ensuring controllable adhesion, so that the bonding force is more uniform when the bonding piece 24 is bonded to the first pole piece 221, thereby improving the reliability of the fixing of the buffer piece 23 on the first pole piece 221, and the fixing method is relatively simple and easy to operate, which is conducive to improving the assembly efficiency. Since the second pole piece 222 is a cathode sheet, the bonding piece 24 can be easily bonded to the cathode sheet through the above-mentioned solution, and the firmness of the bonding piece 24 and the cathode sheet is ensured, which is conducive to improving the fixing reliability of the buffer piece 23, thereby improving the buffering effect of the buffer piece 23 on the arc-shaped portion 2012, reducing the risk of stress concentration, and reducing the probability of swelling and rupture of the outer pole sheet at the position of the arc-shaped portion 2012, thereby improving the reliability of the battery monomer 20. Secondly, the bonding piece 24 can also separate the first pole piece 221 and the second pole piece 222 at the position of the buffer piece 23, so that the first pole piece 221 and the second pole piece 222 at the position of the gap do not react as much as possible, thereby reducing the possibility of metal ion migration, and also reducing the risk of metal ion precipitation caused by the existence of the gap, thereby improving the reliability of the electrode assembly 22 and the battery monomer 20.

[0200] In some embodiments of the present application, referring to FIGS. 11 and 12, the side of the buffer piece 23 close to the first pole piece 221 is bonded to the first pole piece 221.

[0201] Referring to FIG. 11, the side of the buffer piece 23 close to the first pole piece 221 can be bonded with the first pole piece 221, wherein the buffer piece 23 can be bonded with the first pole piece 221 by self-adhesive glue, or the buffer piece 23 can be bonded with the first pole piece 221 by the double-sided adhesive tape 25. Referring to FIG. 12, the side of the buffer piece 23 close to the first pole piece 221 can be bonded with the first pole piece 221, wherein the buffer piece 23 can be bonded with the first pole piece 221 by self-adhesive glue, or the buffer piece 23 can be bonded with the first pole piece 221 by the double-sided adhesive tape 25, and then the other side of the buffer piece 23 away from the first pole piece 221 is provided with the bonding piece 24, and the bonding piece 24 is bonded on the first pole piece 221.

[0202] In the above technical solution, the buffer piece 23 can be bonded with the first pole piece 221 only by the side close to the first pole piece 221, and in this way, the way of fixing the buffer piece 23 on the first pole piece 221 is relatively simple, the cost can be reduced, and the work efficiency can be improved. The buffer piece 23 can also be bonded with the first pole piece 221 by the side close to the first pole piece 221, and the other side away from the first pole piece 221 is provided with the bonding piece 24, and the bonding piece 24 is bonded on the first pole piece 221, and in this way, the two sides of the bonding piece 24 can be limited and fixed, the fixing of the buffer piece 23 can be more reliable, and the probability of the buffer piece 23 being separated from the first pole piece 221 can be reduced, and the reliability of the buffering effect of the buffer piece 23 on the electrode assembly 22 can be improved.

[0203] In some embodiments of the present application, referring to FIG. 13, the buffer piece 23 includes any one of a rectangular shape, a T-shaped, and an arc-shaped.

[0204] Referring to FIG. 13(a), the buffer piece 23 is rectangular, and this rectangular structure is relatively simple in shape, easy to manufacture, and conducive to reducing the cost. Referring to FIG. 10, the rectangular buffer piece 23 can be fixed by being bonded with the first pole piece 221 by the bonding piece 24; or referring to FIG. 11, the rectangular buffer piece 23 can be directly bonded with the first pole piece 221 by the double-sided adhesive tape 25 for fixing; or referring to FIG. 12, the rectangular buffer piece 23 can be bonded with the first pole piece 221 by the bonding piece 24 and the double-sided adhesive tape 25 for fixing.

[0205] Referring to FIG. 13(b), the buffer 23 can also be T-shaped. In this case, the wider end of the T-shaped buffer 23 is closer to the inner side of the electrode assembly 22 in the direction from the inside to the outside of the roll core-shaped electrode assembly 22, and the narrower end of the T-shaped buffer 23 is closer to the outer side of the electrode assembly 22. In this arrangement, the gap between the first and second electrode tabs 221 and 222 gradually decreases in the direction away from the buffer 23 at the end of the electrode assembly 22 in the winding direction F1, and thus the overall space of the gap is also smaller. This is advantageous in reducing the risk of metal ion precipitation from the positive electrode tab and in making the structure of the electrode assembly 22 more compact and improving the volumetric energy density of the battery cell 20.

[0206] In this case, referring to FIG. 14(a), the T-shaped buffer 23 can be fixed by being bonded to the first electrode tab 221 with the adhesive sheet 24. Alternatively, referring to FIG. 14(b), the T-shaped buffer 23 can be fixed by being directly bonded to the first electrode tab 221 with the double-sided tape 25. Alternatively, referring to FIG. 14(c), the T-shaped buffer 23 can be fixed by being bonded to the first electrode tab 221 with both the adhesive sheet 24 and the double-sided tape 25.

[0207] Referring to FIG. 13(c), the buffer 23 can also be arc-shaped. In this case, referring to the explanation of the T-shaped buffer, the width of the arc-shaped buffer 23 gradually decreases from the middle to the ends, which is also advantageous in reducing the gap between the first and second electrode tabs 221 and 222, reducing the risk of metal ion precipitation from the positive electrode tab, and making the structure of the electrode assembly 22 more compact and improving the volumetric energy density of the battery cell 20. In addition, the arc-shaped surface of the arc-shaped buffer 23 is relatively smooth, which can better adapt to the roll core-shaped electrode assembly 22, especially when the buffer 23 is arranged on the arc-shaped portion 2012.

[0208] In this case, referring to FIG. 15(a), the arc-shaped buffer 23 can be fixed by being bonded to the first electrode tab 221 with the adhesive sheet 24. Alternatively, referring to FIG. 15(b), the arc-shaped buffer 23 can be fixed by being directly bonded to the first electrode tab 221 with the double-sided tape 25. Alternatively, referring to FIG. 15(c), the arc-shaped buffer 23 can be fixed by being bonded to the first electrode tab 221 with both the adhesive sheet 24 and the double-sided tape 25.

[0209] In the above technical solutions, the buffer 23 is provided in the above shapes, which provides more design options for the buffer 23. According to the size of the roll core of the electrode assembly 22, the size of the gap between the first and second electrode tabs 221 and 222 in the winding layer and the size of the electrode assembly 22 can be adjusted by selecting a buffer 23 with a different shape, so that the buffer effect and the battery capacity can be traded off as needed, which is advantageous in meeting flexible design requirements.

[0210] In some embodiments of the present application, referring to FIGS. 16 and 17, the buffer 23 is arranged between the isolation films 223 at the two ends of the thickness direction of the winding layer where the second tab 222 is located, and the buffer 23 is provided with the adhesive piece 24, the two ends of the adhesive piece 24 exceeding the buffer 23, and one end adhering to the first end portion 2203 and the other end adhering to the second end portion 2204.

[0211] It can be understood that the buffer 23 can be directly arranged in the accommodating groove 224 formed by the disconnection position of the second tab 222, and since the cathode tab is more easily connected with the adhesive member such as the adhesive tape (the principle is referred to the foregoing), the buffer 23 can be more easily and firmly connected to the second tab 222 by the adhesive piece 24 connected to the first end portion 2203 and the second end portion 2204 formed on the second tab 222.

[0212] Among them, the buffer 23 between the first end portion 2203 and the second end portion 2204 can be one or more, for example, referring to FIG. 16, one buffer 23 can be arranged between the first end portion 2203 and the second end portion 2204; referring to FIG. 17, two buffers 23 can be arranged between the first end portion 2203 and the second end portion 2204, which is not limited here.

[0213] In the above technical solution, the space formed by the disconnection position of the second tab 222 can be fully utilized to arrange the buffer 23 by the above-mentioned scheme, so that no additional space is needed for arranging the buffer 23, which can improve the compactness of the electrode assembly 22, improve the unit volume density of the electrode assembly 22, and further improve the volume energy density of the battery monomer 20. Although there is a gap between the two isolation films 223 where the buffer 23 is located, the gap is located at the two ends of the thickness direction of the winding layer only with the first tab 221 and without the second tab 222, which can reduce the probability of chemical reaction at the position of the gap and cause metal ion migration, and further reduce the risk of metal ion precipitation of the positive tab, and improve the reliability of the battery monomer 20. The buffer 23 connects the first end portion 2203 and the second end portion 2204 through the adhesive piece 24, so that the buffer 23 can be connected to the two disconnected parts of the second tab 222 before the electrode assembly 22 is wound, which is conducive to winding the electrode assembly 22 into a roll core, reduces the winding difficulty, reduces the manufacturing cost, and improves the product yield. The above-mentioned scheme can also fix the buffer 23 in the winding layer, reduce the probability of displacement of the buffer 23 from the expected position, improve the position reliability of the buffer 23 in the electrode assembly 22, and facilitate the buffer 23 to maintain stable and reliable buffering effect.

[0214] In some embodiments of the present application, referring to FIGS. 16-19, the adhesive pieces 24 are arranged at both ends of the thickness direction of the buffer piece 23, and are connected to the first end portion 2203 and the second end portion 2204.

[0215] The buffer piece 23 between the first end portion 2203 and the second end portion 2204 can be one or more, for example, referring to FIG. 16, one buffer piece 23 can be arranged between the first end portion 2203 and the second end portion 2204; referring to FIG. 17, two buffer pieces 23 can be arranged between the first end portion 2203 and the second end portion 2204, which is not limited here.

[0216] In the above technical solution, the adhesive pieces 24 are arranged at both ends of the thickness direction of the buffer piece 23, and are connected to the first end portion 2203 and the second end portion 2204, which can limit both ends of the thickness direction of the buffer piece 23, improve the connection strength of the buffer piece 23 and the second tab 222, and further improve the position reliability of the buffer piece 23 in the electrode assembly 22. Moreover, the above solution can make the connection of the two parts of the buffer piece 23 and the second tab 222 more firm, thereby also improving the rigidity of the buffer piece 23 and the second tab 222 as a whole, which is more conducive to the second tab 222 bending more smoothly during winding, reduces the difficulty of winding the electrode assembly 22 into a core, and is conducive to improving the quality and reliability of the core. Secondly, when the second tab 222 is cut to form the first end portion 2203 and the second end portion 2204, burrs and other structures are easily formed. In the above solution, the adhesive pieces 24 can play an isolation role between the first end portion 2203 and the second end portion 2204 and the separator 223, reducing the risk of the burrs and other structures piercing the separator 223, and improving the reliability of the electrode assembly 22.

[0217] In some embodiments of the present application, referring to FIGS. 16 and 17, the adhesive pieces 24 are bonded to the part of the second tab 222 located on the arc-shaped portion 2012. In this technical solution, the adhesive pieces 24 do not extend to the flat portion 2011 of the electrode assembly 22, thereby reducing the risk of the adhesive pieces 24 extending to the winding layer where the flat portion 2011 is located, causing stress concentration on the first tab 221 or the second tab 222 due to the presence of steps, thereby reducing the probability of damage to the first tab 221 or the second tab 222, further reducing the risk of damage to the active material layer of the first tab 221 or the second tab 222, and improving the reliability of the electrode assembly 22, thereby improving the reliability of the battery monomer 20.

[0218] In some embodiments of the present application, referring to FIG. 16, the electrode assembly 22 comprises a main body portion 201 and a tab 202 connected to each other, the main body portion 201 comprises a flat portion 2011 and an arc-shaped portion 2012 connected to each other, a receiving groove 224 is arranged on the arc-shaped portion 2012, and the length of the second tab 222 between the buffer 23 and the arc-shaped portion 2012 is greater than or equal to 5 mm.

[0219] The length of the second tab 222 between the buffer 23 and the arc-shaped portion 2012 can be L2, which can be, but is not limited to, 5 mm, 6 mm, 7 mm, 10 mm, 15 mm, 20 mm, etc. If the length L2 of the second tab 222 between the buffer 23 and the arc-shaped portion 2012 is less than 5 mm, the length of the second tab 222 extending into the arc-shaped portion 2012 is short, which is not convenient for bonding the adhesive sheet 24, and the adhesive sheet 24 is easy to enter the flat portion 2011, which is easy to cause a step between the second tab 222 and the first tab 221 in the flat portion 2011, increasing the risk of stress concentration.

[0220] In the above technical solution, the above structure is beneficial to leaving a suitable length of the second tab 222 in the arc-shaped portion 2012 for connecting the adhesive sheet 24, which is beneficial to improving the manufacturability and improving the connection strength and reliability of the second tab 222 and the adhesive sheet 24, and can also reduce the risk of the adhesive sheet 24 entering the flat portion 2011, reduce the probability of the first tab 221 and the second tab 222 in the flat portion 211 causing stress concentration and damage, and improve the reliability of the electrode assembly 22.

[0221] In some embodiments of the present application, referring to FIG. 16, the distance between the first end portion 2203 or the second end portion 2204 and the buffer 23 is greater than or equal to 3 mm.

[0222] For convenience of understanding, referring to FIG. 16, the distance between the first end portion 2203 and the buffer 23 can be L3, which can be, but is not limited to, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 10 mm, etc. If the distance L3 between the first end portion 2203 and the buffer 23 is less than 3 mm, the first end portion 2203 is close to the buffer 23, which is not convenient for bonding the adhesive sheet 24, and is not conducive to the expansion of the buffer 23 in the winding direction F1 when the buffer 23 is compressed and deformed. Similarly, the explanation between the second end portion 2204 and the buffer 23 refers to the first end portion 2203, which will not be repeated here.

[0223] In the technical solution, the distance between the first end portion 2203 or the second end portion 2204 and the buffer member 23 is left appropriate, on the one hand, facilitating bonding of the adhesive piece 24, improving manufacturability, and being conducive to ensuring the forming quality of the electrode assembly 22, and on the other hand, providing a certain space for compression and expansion of the buffer member 23, so as to ensure the functionality of the buffer member 23, thereby enabling the buffer member 23 to reduce the probability of swelling and rupture of the outer electrode sheet, and improving the reliability of the battery monomer 20.

[0224] In some embodiments of the present application, referring to FIGS. 18 and 19, the thickness of the buffer member 23 is greater than the thickness of the second electrode sheet 222.

[0225] For example, the thickness direction of the buffer member 23 and the thickness direction of the second electrode sheet 222 can be the first direction X of FIGS. 18 and 19.

[0226] In the technical solution, by virtue of the thickness of the buffer member 23 being greater than the thickness of the second electrode sheet 222, the buffer member 23 can provide a larger buffer space for swelling and deformation of the first electrode sheet 221, thereby reducing the swelling and stretching force of the first electrode sheet 221 on the outer electrode sheet, which is conducive to reducing the risk of swelling and rupture of the outer electrode sheet, further improving the reliability of the electrode assembly 22, and improving the reliability of the battery monomer 20.

[0227] The embodiments of the present application also provide a battery device 100 comprising the battery monomer 20 of any of the foregoing embodiments.

[0228] In the technical solution, since the buffer member 23 in the battery monomer 20 can be arranged in the accommodation groove 224 of at least one winding layer, the probability of rupture of the outer electrode sheet can be reduced, the risk of metal ion precipitation of the positive electrode sheet can be reduced, and the overall reliability of the battery monomer 20 can be improved, thereby improving the reliability of the battery device 100 comprising the battery monomer 20, being conducive to improving the use performance of the battery device 100, and prolonging the service life of the battery device 100.

[0229] The embodiments of the present application also provide a power consumption device 1000 comprising the battery monomer 20 of any of the foregoing embodiments, or the battery device 100 of any of the foregoing embodiments, the battery monomer 20 or the battery device 100 being used for storing or providing electric energy.

[0230] In the technical solution, since the battery monomer 20 and the battery device 100 have high reliability, the power consumption device 1000 comprising the battery monomer 20 or the battery device 100 also has high reliability, and is conducive to reliable operation of the power consumption device 1000.

[0231] Embodiment one

[0232] Referring to FIG. 4, the battery cell 20 according to the embodiment of the present application includes a shell assembly 21, an electrode assembly 22, and a buffer 23.

[0233] The electrode assembly 22 is a race track-shaped winding core and is disposed in the shell assembly 21. The electrode assembly 22 includes a flat portion 2011 and arc-shaped portions 2012 at both ends of the flat portion 2011. In the winding layer at the position of each arc-shaped portion 2012, a cathode tab is partially cut to form a receiving groove 224. The buffer 23 is a foam and is arc-shaped, and is disposed on an anode tab in the arc-shaped portion 2012 corresponding to the cut region of the cathode tab. The buffer 23 is bonded to the anode tab.

[0234] In this way, the buffer 23 can realize a large gap between the tabs of a certain winding layer, provide a stress expansion space for the expansion force of the tabs on other winding layers in the cycle process, reduce the pulling force of the expansion force on the tabs, and prevent the tabs from being broken.

[0235] Embodiment Two

[0236] Referring to FIG. 8, the structure of the battery cell 20 of the embodiment two is substantially the same as that of the battery cell 20 of the embodiment one, except that the buffer 23 is disposed in the first winding layer 203 and the second winding layer 204 of the electrode assembly 22.

[0237] The first winding layer 203 includes a first arc-shaped portion 2031 at one end of the first direction X, and the second winding layer 204 includes a first flat portion 2041 and a second arc-shaped portion 2042 at the other end of the first direction X. The first flat portion 2041 connects the second arc-shaped portion 2042 and the first arc-shaped portion 2031. The first arc-shaped portion 2031 and the second arc-shaped portion 2042 are both provided with the buffer 23. The cut region of the cathode tab extends along the first arc-shaped portion 2031, the first flat portion 2041, and the second arc-shaped portion 2042. The first end portion 2203 is disposed in the first arc-shaped portion 2031 and is located on the side of the buffer 23 away from the first flat portion 2041. The second end portion 2204 is disposed in the second arc-shaped portion 2042 and is located on the side of the buffer 23 away from the first flat portion 2041.

[0238] Embodiment Three

[0239] Referring to FIG. 9, the structure of the battery cell 20 of the embodiment three is substantially the same as that of the battery cell 20 of the embodiment two, except that:

[0240] The first winding layer 203 comprises a first arc-shaped portion 2031 located at one end of the first direction X, and the second winding layer 204 comprises a first flat portion 2041, a second arc-shaped portion 2042, a second flat portion 2043, and a third arc-shaped portion 2044, the first flat portion 2041 connecting the first arc-shaped portion 2031 and the second arc-shaped portion 2042, the second flat portion 2043 connecting the second arc-shaped portion 2042 and the third arc-shaped portion 2044, the first arc-shaped portion 2031 and the second arc-shaped portion 2042 both being provided with the buffer 23, the disconnection area of the cathode sheet extending along the first arc-shaped portion 2031, the first flat portion 2041, the second arc-shaped portion 2042, the second flat portion 2043, and the third arc-shaped portion 2044, the first end portion 2203 being arranged in the first arc-shaped portion 2031 and located at a center of the first arc-shaped portion 2031 away from the first flat portion 2041, and the second end portion 2204 being arranged in the third arc-shaped portion 2044 and located at a center of the third arc-shaped portion close to the second flat portion 2043.

[0241] Embodiment four

[0242] Referring to FIG. 16, the structure of the battery cell 20 of embodiment four is substantially the same as that of the battery cell 20 of embodiment one, except that one end of the disconnection area of the cathode sheet is the first end portion 2203, the other end is the second end portion 2204, the buffer 23 is arranged between the separator films 223 at both ends of the cathode sheet in the thickness direction of the winding layer, and both ends of the buffer 23 in the thickness direction are provided with the adhesive piece 24, both ends of the adhesive piece 24 extend beyond the buffer 23, and one end of the adhesive piece 24 is bonded to the first end portion 2203 and the other end is bonded to the second end portion 2204.

[0243] Embodiment five

[0244] Referring to FIG. 17, the structure of the battery cell 20 of embodiment five is substantially the same as that of the battery cell 20 of embodiment four, except that there are two buffers 23 in each arc-shaped portion 2012, and the two buffers 23 coincide with the quarter division line 2012a of the arc length of the arc-shaped portion 2012.

[0245] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0246] The above is only the preferred embodiments of the present application and is not intended to limit the present application. All the embodiments and optional embodiments of the present application can be combined to form new technical solutions without special description. All the technical features and optional technical features of the present application can be combined to form new technical solutions without special description. Any modification, equivalent replacement, improvement, etc. 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, wherein, The application relates to a battery electrode assembly. The battery electrode assembly comprises a housing assembly, an electrode assembly arranged in the housing assembly, and a buffer arranged in at least one winding layer of the electrode assembly. The electrode assembly comprises a first electrode sheet, a second electrode sheet, and a separator film arranged between the first electrode sheet and the second electrode sheet. The electrode assembly comprises a winding axis, and the electrode assembly has a winding core structure wound around the winding axis and comprises a plurality of winding layers perpendicular to the winding axis.

2. The battery cell of claim 1, wherein, The first electrode sheet and / or the second electrode sheet are provided with a receiving groove, and a part of the buffer is arranged in the receiving groove.

3. The battery cell of claim 1 or 2, wherein, The receiving groove comprises a bottom groove wall and side groove walls arranged at both ends of the bottom groove wall.

4. The battery cell of claim 1 or 2, wherein, The buffer is arranged on the bottom groove wall.

5. The battery cell of any one of claims 1 to 4, wherein, The first electrode sheet and the second electrode sheet each comprise a current collector and an active material layer coated on the surface of the current collector.

6. The battery cell of any one of claims 1 to 5, wherein, The receiving groove is arranged on the current collector and penetrates the active material layer.

7. The battery cell of claim 6, wherein, The receiving groove is arranged on the first electrode sheet and penetrates the first electrode sheet along the thickness direction of the first electrode sheet.

8. The battery cell of claim 7, wherein, The electrode assembly comprises a main body and a tab connected to each other.

9. The battery cell of any one of claims 6-8, wherein, The main body comprises a flat portion and an arc-shaped portion connected to each other.

10. The battery cell of claim 9, wherein, The receiving groove is arranged on the arc-shaped portion.

11. The battery cell of claim 9 or 10, wherein, The arc-shaped portion comprises two ends, and the receiving groove is arranged on each end of the arc-shaped portion.

12. The battery cell of any one of claims 1-11, wherein, The receiving groove and the buffer are arranged in the same winding layer or different winding layers.

13. The battery cell of claim 12, wherein, In the winding direction of the arc-shaped portion, the receiving groove and the buffer are arranged in the center of the arc-shaped portion.

14. The battery cell of claim 13, wherein, The buffer is arranged in the receiving groove in a plurality of ways. In the winding direction of the arc-shaped portion, the buffer has a center surface, and the buffer is arranged in the receiving groove in two ways. In the winding layer where the buffer is arranged, the receiving groove penetrates the first electrode sheet and / or the second electrode sheet along the thickness direction of the winding layer and the winding axis of the electrode assembly and forms a first end and a second end on the first electrode sheet or the second electrode sheet. The electrode assembly comprises a main body and a tab connected to each other. The main body comprises a flat portion and an arc-shaped portion connected to each end of the flat portion in a first direction. The arc-shaped portion has a joint line connected to the flat portion. In the winding direction of the arc-shaped portion, the distance between the first end and the second end and the adjacent joint line is less than or equal to one-fourth of the arc length of the arc-shaped portion.

15. The battery cell of any one of claims 12-14, wherein, The distance between the first end portion or the second end portion and the buffer piece is greater than or equal to 3 mm.

16. The battery cell of claim 13 or 14, wherein, The first pole piece or the second pole piece of the two arc-shaped portions is provided with the accommodating groove, and is provided with the first end portion and the second end portion.

17. The battery cell of any one of claims 12-16, wherein, The plurality of winding layers comprises a first winding layer and a second winding layer connected in sequence, the first winding layer comprises a first arc-shaped portion located at one end of the first direction, the second winding layer comprises a first flat portion, a second arc-shaped portion located at the other end of the first direction, and a second flat portion connecting the second arc-shaped portion and the first arc-shaped portion, the first arc-shaped portion and the second arc-shaped portion are provided with the buffer piece, the accommodating groove extends along the first arc-shaped portion, the first flat portion, and the second arc-shaped portion, the first end portion is arranged in the first arc-shaped portion and located on the side of the buffer piece away from the first flat portion, and the second end portion is arranged in the second arc-shaped portion and located on the side of the buffer piece away from the first flat portion.

18. The battery cell of any one of claims 12-16, wherein, The plurality of winding layers comprises a first winding layer and a second winding layer connected in sequence, the first winding layer comprises a first arc-shaped portion located at one end of the first direction, the second winding layer comprises a first flat portion, a second arc-shaped portion located at the other end of the first direction, a second flat portion, and a third arc-shaped portion, the first flat portion connects the first arc-shaped portion and the second arc-shaped portion, and the second flat portion connects the second arc-shaped portion and the third arc-shaped portion, the first arc-shaped portion and the second arc-shaped portion are provided with the buffer piece, the accommodating groove extends along the first arc-shaped portion, the first flat portion, the second arc-shaped portion, the second flat portion, and the third arc-shaped portion, the first end portion is arranged in the first arc-shaped portion and located on the side of the center of the first arc-shaped portion away from the first flat portion, and the second end portion is arranged in the third arc-shaped portion and located on the side of the center of the third arc-shaped portion close to the second flat portion.

19. The battery cell of claim 18, wherein, The first end portion and the second end portion are staggered in the winding direction of the third arc-shaped portion.

20. The battery cell of any one of claims 12-19, wherein, The first pole piece is an anode piece, the second pole piece is a cathode piece, and the accommodating groove is arranged.

21. The battery cell of claim 20, wherein, The side of the buffer piece away from the first pole piece is provided with an adhesive piece, both ends of the adhesive piece are arranged outside the buffer piece in the winding direction of the electrode assembly, and the adhesive piece is adhered to the first pole piece.

22. The battery cell of claim 20 or 21, wherein, The side of the buffer piece close to the first pole piece is adhered to the first pole piece.

23. The battery cell of claim 21, wherein, The buffer piece comprises any one of a rectangular shape, a T shape, and an arc shape.

24. The battery cell of any one of claims 20-23, wherein, The buffer piece is arranged between the isolation films at both ends of the second pole piece in the thickness direction of the winding layer, and the buffer piece is provided with an adhesive piece, both ends of the adhesive piece are arranged outside the buffer piece, and one end of the adhesive piece is adhered to the first end portion and the other end of the adhesive piece is adhered to the second end portion.

25. The battery cell of claim 24, wherein, The adhesive piece is arranged at both ends in the thickness direction of the buffer piece, and is connected to the first end portion and the second end portion.

26. The battery cell of claim 24 or 25, wherein, The electrode assembly includes the connected body portion and the tab, the body portion includes the connected flat portion and the arc-shaped portion, the accommodation groove is provided on the arc-shaped portion, and the length of the portion of the second tab between the buffer and the arc-shaped portion is greater than or equal to 5 mm.

27. The battery cell of claim 26, wherein, The distance between the first end portion or the second end portion and the buffer is greater than or equal to 3 mm.

28. The battery cell of any one of claims 24-27, wherein, The thickness of the buffer is greater than the thickness of the second tab.

29. A battery device, wherein, A battery cell as claimed in any one of claims 1 to 28.

30. An electrical device, comprising: A battery cell as claimed in any one of claims 1 to 28, or a battery device as claimed in claim 29, for storing or providing electrical energy.

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