Secondary battery, battery pack and energy storage cabinet

Abstract

The utility model discloses a secondary battery, a battery pack and an energy storage cabinet, the secondary battery comprises a shell, a top cover and a naked battery cell, the naked battery cell is located in a containing cavity of the shell, the top cover covers an opening of the containing cavity, the naked battery cell comprises a plurality of stacked pole pieces, and the naked battery cell further comprises a bending area and a straight area. Each pole piece is provided with a first surface and a second surface along a first direction x, the first surface is provided with a first coating and a third coating, the second surface is provided with a second coating and a fourth coating, the first coating and the third coating as well as the second coating and the fourth coating are alternately distributed along a second direction y, and projections of the first coating and the second coating along the first direction x are at least partially overlapped. In the first direction x, the thickness of the first coating is larger than that of the third coating, and the thickness of the second coating is larger than that of the fourth coating; in the second direction y, the width of the first coating is smaller than that of the second coating and / or the width of the first coating and the width of the second coating are gradually increased; the first coating and the second coating are located in the bending area.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a secondary battery, a battery pack and an energy storage cabinet. Background Art

[0002] As an important part of the energy storage system, the battery cell is used to store and release electrical energy. In the process of manufacturing the battery cell, the positive and negative pole pieces are coated with paint along the thickness direction of the pole piece. After the paint is dried, the positive and negative pole pieces are rolled into a preset thickness by rolling, and the pole ears are cut on the positive and negative pole pieces. Finally, the positive pole pieces, negative pole pieces and diaphragms are stacked and wound to form a battery cell. The wound battery cell includes a straight area and a bending area. The positive and negative pole pieces located in the bending area will be bent into an arc structure. In the prior art, along the thickness direction of the pole piece, since the size of the paint on both sides of the pole piece is equal, after the pole piece is bent to form an arc structure, the deformation of the paint inside and outside the pole piece is different, so that the size of the paint inside the pole piece and the size of the paint outside the pole piece do not correspond to the size of the pole piece, thereby reducing the electrical performance of the bending area of ​​the battery cell. Utility Model Content

[0003] In view of this, the present application provides a secondary battery, a battery pack and an energy storage cabinet to solve the technical problem in the prior art that after the pole piece is bent to form an arc structure, the deformation of the coating on the inner and outer sides of the pole piece is different, resulting in reduced electrical performance in the bent area of ​​the battery cell.

[0004] The present application provides a secondary battery, which includes a shell, a top cover and a bare cell, the shell having a accommodating cavity, the top cover covering the opening of the accommodating cavity, the bare cell being located in the accommodating cavity, the bare cell including a positive electrode sheet, a diaphragm and a negative electrode sheet which are stacked, the positive electrode sheet, the diaphragm and the negative electrode sheet being wound to form the bare cell so that the bare cell includes a bent area and a straight area.

[0005] Wherein, each of the pole pieces has a first surface and a second surface along the first direction x, the first surface is provided with a first coating and a third coating, the second surface is provided with a second coating and a fourth coating, the first coating and the third coating are alternately distributed along the second direction y, and the second coating and the fourth coating are alternately distributed along the second direction y, so that the projections of the first coating and the second coating along the first direction x at least partially overlap.

[0006] Along the first direction x, the thickness of the first coating is greater than the thickness of the third coating, and the thickness of the second coating is greater than the thickness of the fourth coating; along the second direction y, the width of the first coating is smaller than the width of the second coating, and / or the width of the first coating and the width of the second coating gradually increase; the first coating and the second coating are both located in the bending area, and the third coating and the fourth coating are both located in the straight area.

[0007] In the embodiment of the present application, when each pole piece is in the unfolded state, by setting the thickness of the first coating along the first direction x to be greater than the thickness of the third coating, the coating amount of the first coating can be increased, so that in the process of winding the positive pole piece, the diaphragm and the negative pole piece to form a bare cell, the possibility of the first coating of each pole piece being easily damaged after being compressed and deformed, resulting in the possibility of falling off from the pole piece body, and the structural stability of the first coating is improved. At the same time, by setting the thickness of the second coating along the first direction x to be greater than the thickness of the fourth coating along the first direction x, the coating amount of the second coating can be increased, so that in the process of winding the positive pole piece, the diaphragm and the negative pole piece to form a bare cell, the possibility of the second coating of each pole piece being easily damaged after being compressed and deformed, resulting in the possibility of falling off from the pole piece body, and the structural stability of the second coating is improved. Based on this, by thickening the first coating and the second coating located in the bending area of ​​the bare cell, each pole piece has a strong mechanical strength after being wound to form a bare cell, which is beneficial to improving the electrical performance of the bending area in the bare cell and improving the stability and reliability of the secondary battery during operation.

[0008] Among them, in the process of winding the positive electrode sheet, the diaphragm and the negative electrode sheet to form a bare cell, the first coating on the first surface is compressed, and the second coating on the second surface is pulled, which easily leads to the coverage of the first coating after bending being larger than the coverage of the electrode body it needs to cover, and the coverage of the second coating after bending being smaller than the coverage of the electrode body it needs to cover. Therefore, in this embodiment, by setting the width of the first coating along the second direction y to be smaller than the width of the second coating along the second direction y, the first coating after bending and the second coating after bending in each electrode sheet can completely cover the electrode body along the third direction z, thereby reducing the possibility of excessive coating of the first coating and the possibility of insufficient coating of the second coating, thereby reducing the coating amount of the first coating, while saving production costs and improving the electrical performance of the bending area in the bare cell.

[0009] In addition, in the process of winding the positive electrode sheet, the separator and the negative electrode sheet to form a bare battery cell, the thickness of the bare battery cell along the third direction z gradually increases, and the radius of its bending area also gradually increases. Therefore, the width of the first coating along the second direction y and the width of the second coating along the second direction y can also be set to gradually increase, so as to wind the stacked positive electrode sheet, the separator and the negative electrode sheet, so that the first coating and the second coating after winding can completely cover the electrode body in the middle area and the edge area of ​​the bare battery cell, thereby reducing the occurrence of empty foil on the electrode body and improving the safety of the secondary battery.

[0010] Therefore, in this embodiment, by changing the thickness and / or width of the first coating and the second coating in the positive electrode sheet, and changing the thickness and / or width of the first coating and the second coating in the negative electrode sheet, the performance of the bending area in the bare battery cell can be optimized to improve the electrical performance of the bending area of ​​the bare battery cell, thereby improving the working stability of the secondary battery and extending the service life of the secondary battery.

[0011] In a possible embodiment, in the bending area, along the third direction z, the arc lengths of the first coatings of N adjacent layers of the pole pieces are equal, the arc lengths of the second coatings of N adjacent layers of the pole pieces are equal, and on the same pole piece, the arc length of the first coating is equal to the arc length of the second coating, wherein the number of layers N satisfies 2≤N≤10.

[0012] In a possible implementation manner, in the bending region, along the third direction z, the arc length relationship of two adjacent layers of the pole pieces satisfies:

[0013] ;

[0014] Wherein, L is the arc length of the pole piece, n is the number of layers of the pole piece, d1 is the tolerance of the arc lengths of two adjacent pole pieces, and d1 satisfies 0.08mm≤d1≤0.2mm.

[0015] In a possible implementation, along the first direction x, the thickness of the first coating is smaller than the thickness of the second coating.

[0016] In a possible implementation, along the second direction y, the thickness of the first coating layer and / or the thickness of the second coating layer gradually decreases.

[0017] In a possible implementation, the thickness of the first coating of N adjacent layers of the pole pieces is equal, the thickness of the second coating of N adjacent layers of the pole pieces is equal, and the thickness of the first coating is equal to the thickness of the second coating.

[0018] In a possible embodiment, the first surface is provided with first grooves along the first direction x, the first grooves are arranged at intervals along the second direction y, and the first coating is applied to the first grooves, and / or the second surface is provided with second grooves, the second grooves are arranged at intervals along the second direction y, and the second coating is applied to the second grooves.

[0019] In a possible implementation manner, along the second direction y, the depth of the first groove and / or the depth of the second groove gradually decreases.

[0020] An embodiment of the present application further provides a battery pack, the battery pack comprising at least one battery module, the battery module comprising at least one secondary battery, wherein the secondary battery is the secondary battery described above.

[0021] In the embodiment of the present application, when the battery pack includes the secondary battery described above, it is beneficial to improve the energy density of the battery pack per unit volume, thereby helping to improve the energy storage and discharge capacity of the battery pack and improve the performance of the battery pack.

[0022] An embodiment of the present application further provides an energy storage cabinet, which includes an inverter, a battery management system and at least one battery pack, wherein the battery pack is the battery pack described above.

[0023] In the embodiment of the present application, the battery pack is connected to an external load through an inverter so as to convert the electric energy in the energy storage cabinet into specific electric energy required by the external load. At the same time, the battery pack and the inverter are both connected to a battery management system. When any battery pack has an abnormality, it is convenient for the staff to check the abnormal battery pack through the battery management system, thereby improving the working stability of the energy storage cabinet.

[0024] It should be understood that the foregoing general description and the following detailed description are exemplary only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0026] Figure 1 A schematic diagram of the structure of a battery cell provided in this application in a specific embodiment;

[0027] Figure 2 for Figure 1 A top view of the middle electrode sheet;

[0028] Figure 3 for Figure 2 Front view of .

[0029] Description of reference numerals:

[0030] 1-Bare battery cell;

[0031] 11- diaphragm;

[0032] 12-pole piece;

[0033] 121- first page;

[0034] 121a-first coating;

[0035] 121b - third coating;

[0036] 121c-first groove;

[0037] 122-side 2;

[0038] 122a - second coating;

[0039] 122b- fourth coating;

[0040] 122c-second groove;

[0041] 13-bending area;

[0042] 14-Straight area.

[0043] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application. DETAILED DESCRIPTION

[0044] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0045] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0046] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0047] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0048] The embodiment of the present application provides a secondary battery, such as Figure 1 As shown, the secondary battery includes a shell, a top cover and a bare cell 1. The shell has a accommodating cavity, which is used to accommodate electrolyte and the bare cell 1. The top cover is covered at the opening of the accommodating cavity to encapsulate the accommodating cavity, reduce the possibility of electrolyte leakage, and improve the sealing of the secondary electrolyte.

[0049] The bare cell 1 includes a stacked positive electrode sheet, a separator 11 and a negative electrode sheet, which can be used to form the above-mentioned bare cell 1 by winding, and the bare cell 1 includes a bending area 13 and a straight area 14. During the winding process, the positive electrode sheet, the separator 11 and the negative electrode sheet are stacked along the first direction x, so that the adjacent positive electrode sheets and negative electrode sheets can be isolated by the separator 11, which is conducive to reducing the risk of short circuit.

[0050] In this embodiment, Figure 1 and Figure 2 As shown, when each pole piece 12 is in the unfolded state, the thickness direction of each pole piece 12 is defined as the first direction x, and the extension direction of each pole piece 12 is defined as the second direction y. After each pole piece 12 is wound to form a bare battery cell 1, the direction along the middle area toward the edge area is defined as the third direction z.

[0051] Specifically, Figure 2 and Figure 3 As shown, when each pole piece 12 is in an unfolded state, each pole piece 12 has a first surface 121 and a second surface 122 along a first direction x, the first surface 121 is provided with a first coating 121a and a third coating 121b, the second surface 122 is provided with a second coating 122a and a fourth coating 122b, the first coating 121a and the third coating 121b are alternately distributed along the second direction y, and the second coating 122a and the fourth coating 122b are alternately distributed along the second direction y, so that the projections of the first coating 121a and the second coating 122a along the first direction x at least partially overlap, and the projections of the third coating 121b and the fourth coating 122b along the first direction x at least partially overlap.

[0052] More specifically, if Figure 1 , Figure 2 and Figure 3As shown, when the positive electrode sheet, the separator 11 and the negative electrode sheet are wound to form a bare battery cell 1, the first side 121 is the side of each electrode sheet 12 facing the inner side of the bare battery cell 1 along the third direction z after the electrode sheet 12 is wound, and the second side 122 is the side of each electrode sheet 12 facing the outer side of the bare battery cell 1 along the third direction z after the electrode sheet 12 is wound, and the first coating 121a and the second coating 122a of each electrode sheet 12 are both located in the bending area 13 of the bare battery cell 1, and the third coating 121b and the fourth coating 122b of each electrode sheet 12 are both located in the straight area 14 of the bare battery cell 1.

[0053] In which, along the first direction x, the thickness of the first coating 121a is greater than the thickness of the third coating 121b, and the thickness of the second coating 122a is greater than the thickness of the fourth coating 122b; along the second direction y, the width of the first coating 121a is smaller than the width of the second coating 122a, and / or the width of the first coating 121a and the width of the second coating 122a gradually increase.

[0054] In the embodiment of the present application, during the winding process of the positive electrode sheet, the diaphragm 11 and the negative electrode sheet, the first surface 121 of each electrode sheet 12 is compressed and contracted, and its bent area (i.e., the first coating 121a) is thickened, and the second surface 122 of each electrode sheet 12 is stretched and elongated, and its bent area (i.e., the second coating 122a) is thinned, and since the strain neutral layer is maintained and moved toward the first surface 121, the thinning amount of the second surface 122 is greater than the thickening amount of the first surface 121, so that the deformation amount of the first surface 121 of each electrode sheet 12 is greater than the deformation amount of the second surface 122 of each electrode sheet 12, that is, in each electrode sheet 12, the deformation amount of the first coating 121a is greater than the deformation amount of the second coating 122a. When the positive electrode sheet, the separator 11 and the negative electrode sheet are wound to form a bare battery cell 1, along the third direction z, the deformation of the middle area of ​​the bare battery cell 1 is greater than the deformation of the edge area of ​​the bare battery cell 1, that is, in each electrode sheet 12, along the second direction y, the deformation of the first coating 121a of each electrode sheet 12 gradually increases, and the deformation of the second coating 122a of each electrode sheet 12 gradually increases.

[0055] When each electrode sheet 12 is in the unfolded state, by setting the thickness of the first coating 121a along the first direction x to be greater than the thickness of the third coating 121b, the coating amount of the first coating 121a can be increased, thereby reducing the possibility that the first coating 121a of each electrode sheet 12 is easily damaged after being compressed and deformed, resulting in it falling off from the electrode sheet body, thereby improving the structural stability of the first coating 121a. At the same time, by setting the thickness of the second coating 122a along the first direction x to be greater than the thickness of the fourth coating 122b along the first direction x, the coating amount of the second coating 122a can be increased, thereby reducing the possibility that the second coating 122a of each electrode sheet 12 is easily damaged after being compressed and deformed, resulting in it falling off from the electrode sheet body, thereby improving the structural stability of the second coating 122a. Based on this, by thickening the first coating 121a and the second coating 122a located in the bending area 13 of the bare battery cell 1, each electrode 12 has a strong mechanical strength after being wound to form the bare battery cell 1, which is beneficial to improving the electrical performance of the bending area 13 in the bare battery cell 1 and improving the stability and reliability of the secondary battery during operation.

[0056] Among them, in the process of winding the positive electrode sheet, the separator 11 and the negative electrode sheet to form the bare battery cell 1, the first coating 121a located on the first surface 121 is compressed, and the second coating 122a located on the second surface 122 is pulled, which easily leads to the coverage of the first coating 121a after bending being larger than the coverage of the electrode body it needs to cover, and the coverage of the second coating 122a after bending being smaller than the coverage of the electrode body it needs to cover. Therefore, in this embodiment, by setting the width of the first coating 121a along the second direction y to be smaller than the width of the second coating 122a along the second direction y, the bent first coating 121a and the bent second coating 122a in each electrode 12 can completely cover the electrode body along the third direction z, thereby reducing the possibility of excessive coating of the first coating 121a and the possibility of insufficient coating of the second coating 122a, thereby reducing the coating amount of the first coating 121a, while saving production costs, improving the electrical performance of the bending area 13 in the bare battery cell 1.

[0057] In addition, in the process of winding the positive electrode sheet, the separator 11 and the negative electrode sheet to form the bare battery cell 1, the thickness of the bare battery cell 1 along the third direction z gradually increases, and the radius of the bending area 13 thereof also gradually increases. Therefore, the width of the first coating 121a along the second direction y and the width of the second coating 122a along the second direction y can also be set to gradually increase, so as to wind the stacked positive electrode sheet, the separator 11 and the negative electrode sheet, so that the first coating 121a and the second coating 122a after winding can completely cover the electrode body in the middle area and the edge area of ​​the bare battery cell 1, thereby reducing the occurrence of empty foil on the electrode body and improving the safety of the secondary battery.

[0058] Therefore, in this embodiment, by changing the thickness and / or width of the first coating 121a and the second coating 122a in the positive electrode sheet, and changing the thickness and / or width of the first coating 121a and the second coating 122a in the negative electrode sheet, the performance of the bending area 13 in the bare battery cell 1 can be optimized to improve the electrical performance of the bending area 13 of the bare battery cell 1, thereby improving the working stability of the secondary battery and extending the service life of the secondary battery.

[0059] In a possible implementation, the coating of the positive electrode plate may be one or more of lithium iron phosphate, lithium cobaltate or lithium titanate, and the coating of the negative electrode plate may be one or more of artificial graphite, natural graphite or amorphous carbon.

[0060] When each electrode sheet 12 is in an unfolded state, the first surface 121 of the positive electrode sheet and the negative electrode sheet is further provided with a third coating 121b, and the second surface 122 of the positive electrode sheet and the negative electrode sheet is further provided with a fourth coating 122b, and along the second direction y, the first coating 121a and the third coating 121b are alternately distributed, and the second coating 122a and the fourth coating 122b are alternately distributed, so that the projections of the first coating 121a and the second coating 122a along the first direction x at least partially overlap, and the projections of the third coating 121b and the fourth coating 122b along the first direction x at least partially overlap.

[0061] When the positive electrode sheet, the separator 11 and the negative electrode sheet are wound into a bare battery cell 1, the first coating 121a and the second coating 122a of the positive electrode sheet and the negative electrode sheet are both located in the bending area 13 of the bare battery cell 1, and the third coating 121b and the fourth coating 122b of the positive electrode sheet and the negative electrode sheet are both located in the straight area 14 of the bare battery cell 1.

[0062] Among them, the first coating 121a and the third coating 121b can be coated with different materials respectively, and the second coating 122a and the fourth coating 122b can be coated with different materials, so that the active material load per unit area of ​​the first coating 121a is smaller than the active material load per unit area of ​​the third coating 121b, and the active material load per unit area of ​​the second coating 122a is smaller than the active material load per unit area of ​​the fourth coating 122b, so as to reduce the internal stress of the positive electrode plate in the bending area 13 of the bare battery cell 1, reduce the possibility of lithium plating, improve the working stability of the secondary battery, and increase the service life of the secondary battery.

[0063] In a possible embodiment, the third coating 121b and the fourth coating 122b can be coated on the first surface 121 and the second surface 122 of each pole piece 12 respectively along the second direction y, and then the first coating 121a is coated on the first surface 121 of each pole piece 12 at intervals along the second direction y, and the second coating 122a is coated on the second surface 122 of each pole piece 12 at intervals, thereby avoiding the possibility of electrical performance failure of each pole piece 12 due to accidental shedding of the first coating 121a and / or the second coating 122a, and further ensuring the stability of the secondary battery during operation.

[0064] In a specific embodiment, Figure 1 As shown, in the bending area 13 of the bare battery cell 1, along the third direction z, the arc lengths of the first coatings 121a of adjacent N layers of pole pieces 12 are equal, the arc lengths of the second coatings 122a of adjacent N layers of pole pieces 12 are equal, and on the same pole piece 12, the arc length of the first coating 121a is equal to the arc length of the second coating 122a, wherein the number of adjacent layers N satisfies 2≤N≤10.

[0065] In the embodiment of the present application, since the thicknesses of the positive electrode sheet, the separator 11 and the negative electrode sheet are all relatively small, after the positive electrode sheet, the separator 11 and the negative electrode sheet are wound to form the bare battery cell 1, along the third direction z, the sizes of some adjacent positive electrode sheets and negative electrode sheets in the bending area 13 thereof are relatively small. Therefore, the arc lengths of the first coatings 121a of adjacent N-layer pole pieces 12 can be set to be equal, the arc lengths of the second coatings 122a of adjacent N-layer pole pieces 12 can be set to be equal, and on the same pole piece 12, the arc length of the first coating 121a is equal to the arc length of the second coating 122a, that is, when the positive pole pieces and negative pole pieces of adjacent N layers are in the unfolded state, along the direction in which the two are stacked, the widths of the first coatings 121a of adjacent N-layer pole pieces 12 along the second direction y are equal, the widths of the second coatings 122a of adjacent N-layer pole pieces 12 along the second direction y are equal, and in adjacent N-layer pole pieces 12, the width of the first coating 121a of the same pole piece 12 along the second direction y is equal to the width of the second coating 122a along the second direction y. The above-mentioned arrangement is helpful to reduce the difficulty of processing the first coating 121a and the second coating 122a on the positive electrode sheets and the negative electrode sheets, thereby reducing the processing accuracy during the processing and improving the control effect of the processing equipment, which is beneficial to improve the production yield of the positive electrode sheets and the negative electrode sheets while reducing the production cost.

[0066] Among them, the number of adjacent layers N can specifically be 2, 3, 4, 5, 6, 7, 8, 9, and 10. When the number of adjacent layers N satisfies 2≤N≤10, in the bending area 13 of the bare battery cell 1, along the third direction z, the sizes of the adjacent positive electrode sheets and negative electrode sheets are slightly different, so that after winding, the first coating 121a and the second coating 122a of the positive electrode sheet can both cover the corresponding electrode sheet body, and after winding, the first coating 121a and the second coating 122a of the negative electrode sheet can both cover the corresponding electrode sheet body, ensuring that the bending area 13 of the bare battery cell 1 still has good electrical performance, thereby reducing the processing difficulty while ensuring the stability and reliability of the secondary battery during operation.

[0067] In another specific embodiment, Figure 1 As shown, in the bending area 13 of the bare battery cell 1, along the third direction z, the arc length relationship between two adjacent layers of pole pieces 12 satisfies:

[0068] ;

[0069] Wherein, L is the arc length of the pole piece 12, n is the number of layers of the pole piece 12, d1 is the tolerance of the arc lengths of two adjacent pole pieces 12, and d1 satisfies 0.08 mm≤d1≤0.2 mm.

[0070] In the embodiment of the present application, in the process of winding the positive electrode sheet, the separator 11 and the negative electrode sheet to form the bare cell 1, the thickness of the bare cell 1 along the third direction z gradually increases, and the radius of the bending area 13 thereof also gradually increases. Therefore, the size relationship between adjacent electrode sheets 12 in the bending area 13 of the bare cell 1 can be set by the above formula.

[0071] Specifically, along the third direction z, there is a tolerance d1 between the arc lengths of two adjacent layers of electrode sheets 12, that is, when the adjacent positive electrode sheets and negative electrode sheets are in the unfolded state, along the direction in which the two are stacked, there is a tolerance d1 between the width of the first coating 121a of the positive electrode sheet along the second direction y and the width of the first coating 121a of the adjacent negative electrode sheet along the second direction y, and there is a tolerance d1 between the width of the second coating 122a of the positive electrode sheet along the second direction y and the width of the second coating 122a of the adjacent negative electrode sheet along the second direction y. Therefore, by setting a tolerance d1 between the sizes of two adjacent layers of electrode sheets 12, the first coating 121a and the second coating 122a of the electrode sheet 12 are gradually increased in the direction from the middle area to the edge area in the bending area 13 of the bare battery cell 1, so as to wind the stacked positive electrode sheet, the diaphragm 11 and the negative electrode sheet, so that the first coating 121a and the second coating 122a after winding can completely cover the electrode sheet body in the middle area and the edge area of ​​the bare battery cell 1, thereby reducing the occurrence of empty foil on the electrode sheet body and improving the safety of the secondary battery.

[0072] Specifically, the tolerance d1 of the arc length of two adjacent pole pieces 12 can be 0.08mm, 0.09mm, 0.1mm, 0.11mm, 0.12mm, 0.13mm, 0.14mm, 0.15mm, 0.16mm, 0.17mm, 0.18mm, 0.19mm, 0.2mm, etc. When the tolerance d1 of the arc length of two adjacent pole pieces 12 satisfies 0.08mm≤d1≤0.2mm, the difference between the positive pole piece and the adjacent negative pole piece in the bending area 13 of the bare battery cell 1 along the third direction z is moderate, which can reduce the difficulty of processing the first coating 121a and the second coating 122a on the positive pole piece and the negative pole piece, thereby reducing the processing accuracy during the processing, improving the control effect of the processing equipment, and thus helping to reduce the production cost while improving the production yield of the positive pole piece and the negative pole piece.

[0073] In a possible embodiment, when the first coating 121a and the second coating 122a of the pole piece 12 gradually increase from the middle area to the edge area, the arc lengths of the first coating 121a and the second coating 122a located on the same pole piece 12 can be equal, that is, when the adjacent positive pole piece and the negative pole piece are in the unfolded state, along the direction in which the two are stacked, the widths of the first coating 121a and the second coating 122a located on the same pole piece 12 along the second direction y are equal, thereby further reducing the difficulty of processing the first coating 121a and the second coating 122a on the pole piece 12.

[0074] Alternatively, when the first coating 121a and the second coating 122a of the pole piece 12 gradually increase from the middle area toward the edge area, there is a tolerance d2 between the first coating 121a and the second coating 122a located on the same pole piece 12, and the tolerance d2 satisfies 0mm<d2<0.08mm.

[0075] In a specific embodiment, Figure 2 and Figure 3 As shown, along the first direction x, the thickness of the first coating layer 121 a is less than the thickness of the second coating layer 122 a .

[0076] In the embodiment of the present application, after the positive electrode sheet, the separator 11 and the negative electrode sheet are wound to form the bare battery cell 1, the first coating 121a of the positive electrode sheet and the negative electrode sheet are both oriented toward the inside of the bare battery cell 1 along the third direction z, and the second coating 122a of the positive electrode sheet and the negative electrode sheet are both oriented toward the outside of the bare battery cell along the third direction z. By setting the thickness of the first coating 121a on each electrode sheet 12 to be smaller than the thickness of the second coating 122a, the coating amount of the first coating 121a on the inner side of the same electrode sheet 12 is less than the coating amount of the second coating 122a on the outer side. In this way, during the winding process of the positive electrode sheet and the negative electrode sheet, it is easier to bend the first coating 121a and the second coating 122a of the two, which is beneficial to improving the processing efficiency of the bare battery cell 1. At the same time, during the operation of the second battery, the number of lithium ions on the inner side of the positive electrode sheet in the bending area 13 can be limited, thereby avoiding the situation of uneven local distribution of lithium ions in the bending area 13 and reducing the possibility of lithium deposition in the bending area 13, so as to ensure the working stability of the secondary battery and further improve the service life of the secondary battery.

[0077] In a specific embodiment, Figure 2 and Figure 3 As shown, along the second direction y, the thickness of the first coating layer 121a and / or the thickness of the second coating layer 122a gradually decreases.

[0078] In the embodiment of the present application, in the process of winding the positive electrode sheet, the separator 11 and the negative electrode sheet to form the bare battery cell 1, the thickness of the bare battery cell 1 along the third direction z gradually increases, and the radius of the bending area 13 thereof also gradually increases. Therefore, by setting the thickness of the first coating 121a along the second direction y and / or the thickness of the second coating 122a along the second direction y to gradually decrease, the end of the positive electrode sheet along the second direction y and the end of the negative electrode sheet along the second direction y are easier to be bent, so that during the winding process, the positive electrode sheet located in the bending area 13 can be more closely attached to the adjacent negative electrode sheet, so as to improve the electrical performance of the bending area 13 in the bare battery cell 1, thereby improving the stability and reliability of the secondary battery during operation.

[0079] In a specific embodiment, Figure 1 As shown, in the bending area 13 of the bare battery cell 1, along the third direction z, the thickness of the first coating 121a of adjacent N layers of pole pieces 12 is equal, the thickness of the second coating 122a of adjacent N layers of pole pieces 12 is equal, and on the same pole piece 12, the thickness of the first coating 121a is equal to the thickness of the second coating 122a, wherein the number of layers N satisfies 2≤N≤10.

[0080] In the embodiment of the present application, since the thicknesses of the positive electrode sheet, the separator 11 and the negative electrode sheet are all relatively small, after the positive electrode sheet, the separator 11 and the negative electrode sheet are wound to form the bare battery cell 1, along the third direction z, the bending radii of some adjacent positive electrode sheets and negative electrode sheets in the bending area 13 thereof are relatively small. Therefore, the thickness of the first coating 121a of adjacent N-layer pole pieces 12 can be set to be equal, the thickness of the second coating 122a of adjacent N-layer pole pieces 12 can be set to be equal, and on the same pole piece 12, the thickness of the first coating 121a is equal to the thickness of the second coating 122a, that is, when the positive pole piece and the negative pole piece of adjacent N layers are in the unfolded state, along the stacking direction of the two, the thickness of the first coating 121a of adjacent N-layer pole pieces 12 in the first direction x is equal, the thickness of the second coating 122a of adjacent N-layer pole pieces 12 in the first direction x is equal, and in adjacent N-layer pole pieces 12, the thickness of the first coating 121a in the first direction x of the same pole piece 12 is equal to the thickness of the second coating 122a in the first direction x. The above-mentioned arrangement is helpful to reduce the difficulty of bending the positive electrode sheet and the negative electrode sheet, improve the processing efficiency of the bare battery cell 1, and enable the bent positive electrode sheet to fit more closely with the adjacent negative electrode sheet, thereby improving the electrical performance of the bending area 13 in the bare battery cell 1, thereby improving the stability and reliability of the secondary battery during operation.

[0081] Among them, the number of adjacent layers N can specifically be 2, 3, 4, 5, 6, 7, 8, 9, and 10. When the number of adjacent layers N satisfies 2≤N≤10, in the bending area 13 of the bare battery cell 1, along the third direction z, the bending radius of the adjacent positive electrode sheet and the negative electrode sheet is slightly different, so that after winding, the first coating 121a and the second coating 122a of the positive electrode sheet can both cover the corresponding electrode sheet body, and after winding, the first coating 121a and the second coating 122a of the negative electrode sheet can both cover the corresponding electrode sheet body, ensuring that the bending area 13 of the bare battery cell 1 still has good electrical performance, thereby reducing the difficulty of bending while ensuring the stability and reliability of the secondary battery during operation.

[0082] In a specific embodiment, Figure 2 As shown, along the first direction x, the first surface 121 is provided with first grooves 121c, the first grooves 121c are arranged at intervals along the second direction y, and the first coating 121a is coated in the first grooves 121c, and / or, the second surface 122 is provided with second grooves 122c, the second grooves 122c are arranged at intervals along the second direction y, and the second coating 122a is coated in the second grooves 122c.

[0083] In the embodiment of the present application, after the positive electrode sheet, the separator 11 and the negative electrode sheet are wound to form a bare battery cell 1, the first groove 121c and the second groove 122c of the positive electrode sheet are both located in the bending area 13 of the bare battery cell 1, and the first groove 121c and the second groove 122c of the negative electrode sheet are both located in the bending area 13 of the bare battery cell 1.

[0084] When the first coating 121a and the second coating 122a of the positive electrode sheet and the negative electrode sheet are respectively coated in the corresponding first groove 121c and the second groove 122c, during the winding process, the first groove 121c is compressed, resulting in a smaller space in the first groove 121c, and the second groove 122c is pulled, resulting in an increase in the space in the second groove 122c, and when the winding is completed, the first coating 121a of the positive electrode sheet and the negative electrode sheet can fill the first groove 121c, and the second coating 122a of the positive electrode sheet and the negative electrode sheet can fill the second groove 122c, so that the first coating 121a along the third direction z toward the surface of the middle area of ​​the bare battery cell 1 is aligned with the positive electrode 1. The first surfaces 121 of the positive electrode sheet and the negative electrode sheet are flush, and the surface of the second coating 122a along the third direction z toward the edge area of ​​the bare battery cell 1 is flush with the second surfaces 122 of the positive electrode sheet and the negative electrode sheet, so as to ensure the flatness of the first surface 121 and the second surface 122 of each electrode sheet 12 after winding, avoid overflow of the first coating 121a in each electrode sheet 12, and avoid breakage of the second coating 122a in each electrode sheet 12. At the same time, it is also convenient to bend the first coating 121a and the second coating 122a during the winding process, thereby improving the structural stability of the bending area 13 of the bare battery cell 1, so that the secondary electrode is safer and more reliable during operation.

[0085] Specifically, each pole piece 12 is provided with a plurality of first grooves 121c and a plurality of second grooves 122c. When each pole piece 12 is in the unfolded state, along the second direction y, the first grooves 121c and the second grooves 122c are symmetrically distributed relative to the midline position of the pole piece body, so that the two are aligned along the first direction x, so that the first grooves 121c and the second grooves 122c are deformed simultaneously during the winding process of the positive pole piece, the diaphragm 11 and the negative pole piece, so that after being wound into a bare battery cell 1, the first grooves 121c and the second grooves 122c are both located in the bending area 13 and fit each other along the third direction z, thereby reducing the possibility of lithium plating and improving the electrical performance of the bending area 13.

[0086] In a specific embodiment, Figure 2 As shown, along the second direction y, the depth of the first groove 121c and / or the depth of the second groove 122c gradually decreases.

[0087] In the embodiment of the present application, the depth of the first groove 121c and / or the depth of the second groove 122c gradually decreases along the second direction y, so that the thickness of the first coating 121a and / or the second coating 122a along the second direction y gradually decreases, so that in the process of winding the positive electrode sheet and the negative electrode sheet, the end of the positive electrode sheet along the second direction y and the end of the negative electrode sheet along the second direction y are more easily bent. At the same time, the structural strength of the positive electrode sheet along the second direction y and the structural strength of the negative electrode sheet along the second direction y are gradually enhanced, reducing the possibility of fracture of each electrode sheet 12, and improving the structural stability of the positive electrode sheet and the negative electrode sheet, so that when the positive electrode sheet, the diaphragm 11 and the negative electrode sheet are wound into a bare battery cell 1, the positive electrode sheet located in the bending area 13 can be more closely attached to the adjacent negative electrode sheet, thereby reducing the possibility of low energy density in the bending area 13, improving the electrical performance of the bending area 13 in the bare battery cell 1, and improving the stability and reliability of the secondary battery during operation.

[0088] In one possible embodiment, when each electrode sheet 12 is in an unfolded state, along the first direction x, the depth of the first groove 121c is less than the depth of the second groove 122c, so that the coating amount of the first coating 121a on the same electrode sheet 12 is less than the coating amount of the second coating 122a, so that after the positive electrode sheet, the diaphragm 11 and the negative electrode sheet are wound into a bare battery cell 1, the possibility of lithium deposition in the bending area 13 can be further reduced, and the positive electrode sheet and the negative electrode sheet are easier to be bent during the winding process, thereby further improving the processing efficiency of the bare battery cell 1 and further improving the safety performance and service life of the secondary battery.

[0089] An embodiment of the present application also provides a battery pack, which includes at least one battery module, and the battery module includes at least one secondary battery, wherein the secondary battery is the secondary battery described above, which is beneficial to improving the energy density of the battery pack per unit volume, thereby facilitating improving the energy storage and discharge capacity of the battery pack and improving the performance of the battery pack.

[0090] An embodiment of the present application also provides an energy storage cabinet, which includes an inverter, a battery management system and at least one battery pack, wherein the battery pack is the above-mentioned battery pack.

[0091] In the embodiment of the present application, the battery pack is connected to an external load through an inverter so as to convert the electric energy in the energy storage cabinet into specific electric energy required by the external load. At the same time, the battery pack and the inverter are both connected to a battery management system. When any battery pack has an abnormality, it is convenient for the staff to check the abnormal battery pack through the battery management system, thereby improving the working stability of the energy storage cabinet.

[0092] The above describes in detail the structure, features and effects of the present application based on the embodiments shown in the drawings. The above is only a preferred embodiment of the present application, but the present application does not limit the scope of implementation to what is shown in the drawings. Any changes made in accordance with the concept of the present application, or modifications to equivalent embodiments with equivalent changes, which still do not exceed the spirit covered by the description and drawings, should be within the protection scope of the present application.

Claims

1. A secondary battery, characterized in that: The secondary battery comprises: A housing having a receiving cavity; A top cover, the top cover covers the opening of the accommodating cavity; A bare battery cell (1), the bare battery cell (1) being located in the accommodating cavity, the bare battery cell (1) comprising a positive electrode sheet, a separator (11) and a negative electrode sheet which are stacked, the positive electrode sheet, the separator (11) and the negative electrode sheet being wound to form the bare battery cell (1), so that the bare battery cell (1) comprises a bent region (13) and a straight region (14); Each of the pole pieces (12) has a first surface (121) and a second surface (122) along a first direction x, the first surface (121) is provided with a first coating (121a) and a third coating (121b), the second surface (122) is provided with a second coating (122a) and a fourth coating (122b), the first coating (121a) and the third coating (121b) are alternately distributed along a second direction y, and the second coating (122a) and the fourth coating (122b) are alternately distributed along the second direction y, so that the projections of the first coating (121a) and the second coating (122a) along the first direction x at least partially overlap; Along the first direction x, the thickness of the first coating (121a) is greater than the thickness of the third coating (121b), and the thickness of the second coating (122a) is greater than the thickness of the fourth coating (122b); Along the second direction y, the width of the first coating (121a) is smaller than the width of the second coating (122a), and / or the width of the first coating (121a) and the width of the second coating (122a) gradually increase; The first coating (121a) and the second coating (122a) are both located in the bending area (13), and the third coating (121b) and the fourth coating (122b) are both located in the straight area (14).

2. The secondary battery according to claim 1, characterized in that: In the bending area (13), along the third direction z, the arc lengths of the first coating (121a) of N adjacent layers of the pole pieces (12) are equal, the arc lengths of the second coating (122a) of N adjacent layers of the pole pieces (12) are equal, and on the same pole piece (12), the arc length of the first coating (121a) is equal to the arc length of the second coating (122a), wherein the number of layers N satisfies 2≤N≤10.

3. The secondary battery according to claim 1, characterized in that: In the bending area (13), along the third direction z, the arc length relationship between two adjacent layers of the pole pieces (12) satisfies: ； Wherein, L is the arc length of the pole piece (12), n is the number of layers of the pole piece (12), d1 is the tolerance of the arc lengths of two adjacent pole pieces (12), and d1 satisfies 0.08 mm ≤ d1 ≤ 0.2 mm.

4. The secondary battery according to any one of claims 1 to 3, characterized in that: Along the first direction x, the thickness of the first coating layer (121a) is smaller than the thickness of the second coating layer (122a).

5. The secondary battery according to any one of claims 1 to 3, characterized in that: Along the second direction y, the thickness of the first coating layer (121a) and / or the thickness of the second coating layer (122a) gradually decreases.

6. The secondary battery according to claim 2, characterized in that: The thickness of the first coating (121a) of the adjacent N layers of pole pieces (12) is equal, the thickness of the second coating (122a) of the adjacent N layers of pole pieces (12) is equal, and the thickness of the first coating (121a) is equal to the thickness of the second coating (122a).

7. The secondary battery according to any one of claims 1 to 3, characterized in that: The first surface (121) is provided with first grooves (121c) along a first direction x, the first grooves (121c) are arranged at intervals along a second direction y, and the first coating (121a) is applied in the first grooves (121c), and / or the second surface (122) is provided with second grooves (122c), the second grooves (122c) are arranged at intervals along a second direction y, and the second coating (122a) is applied in the second grooves (122c).

8. The secondary battery according to claim 7, characterized in that: Along the second direction y, the depth of the first groove (121c) and / or the depth of the second groove (122c) gradually decreases.

9. A battery pack, characterized in that: The battery pack includes at least one battery module, and the battery module includes at least one secondary battery; The secondary battery is the secondary battery according to any one of claims 1 to 8.

10. An energy storage cabinet, characterized in that: The energy storage cabinet includes an inverter, a battery management system and at least one battery pack, wherein the battery pack is the battery pack according to claim 9.

Images