Manufacturing method for thermally compounded stacked battery cell, and thermally compounded stacked battery cell

Abstract

The present application discloses a manufacturing method for a thermally compounded stacked battery cell, and a thermally compounded stacked battery cell. The method comprises the following steps: providing a negative electrode sheet, a positive electrode sheet, and a separator; thermally compounding the negative electrode sheet, the positive electrode sheet, and the separator to form a thermally compounded structure; performing machining on the thermally compounded structure to form a plurality of incomplete cutoff structures, wherein adjacent incomplete cutoff structures are spaced apart from each other by i positive electrode sheets, and i is a positive integer; and folding the thermally compounded structure along a straight line where the incomplete cutoff structures are located, so as to manufacture the thermally compounded stacked battery cell.

Description

Preparation method of thermal composite laminated battery core and thermal composite laminated battery core

[0001] This application claims priority to Chinese patent applications filed with the China Patent Office on April 3, 2024, with application numbers 202410404575.3, 202420686693.3, 202410404589.5, 202420685535.6, 202410405978.X, and 202420693462.5. The entire contents of the above applications are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the field of battery technology, and in particular relates to a preparation method of a thermal composite laminated battery cell and a thermal composite laminated battery cell. Background Art

[0003] At present, battery cells are mainly made through folding or winding processes. Thermal composite laminated cells have been widely used due to their many advantages. The electrodes of thermal composite laminated cells are in a free-fall state during the folding process. The negative and positive electrodes in the thermal composite laminated cells are misaligned, and the alignment of the thermal composite laminated cells is poor. During the battery charging process, lithium ions are deintercalated from the positive electrode and embedded in the negative electrode. Due to the misalignment of the positive and negative electrodes, the lithium ions cannot be completely embedded in the negative electrode. The lithium ions that cannot be embedded in the negative electrode can only obtain electrons on the surface of the negative electrode, thereby forming white metallic lithium and causing lithium plating. Lithium plating significantly shortens the cycle life of the battery, limits the fast charging capacity of the battery, and may also cause combustion and explosion, posing a safety hazard and reducing the performance of the battery.

[0004] In related technologies, to improve the alignment of thermally composite laminated cells, a shaping process is added to the production process. After the thermally composite unit is folded through free fall to form a cell, shaping cylinders are used to clamp the cell from both sides to align the individual electrode sheets within the cell. Relying on shaping cylinders for cell shaping still results in poor alignment, and during the shaping process, the electrode sheets can be knocked loose, increasing the risk of short circuits in the cell pack. SUMMARY OF THE INVENTION

[0005] The present application provides a preparation method of a thermal composite laminated battery cell and a thermal composite laminated battery cell. By setting an incomplete cutting structure on the thermal composite structure, the thermal composite structure is folded along the incomplete cutting structure, thereby achieving technical effects of good folding quality, high folding efficiency and good alignment.

[0006] In a first aspect, the present application provides a method for preparing a thermal composite laminated battery cell, comprising the following steps:

[0007] Provide negative electrode sheets, positive electrode sheets, and separators;

[0008] The negative electrode sheet, the positive electrode sheet and the separator are thermally composited to form a thermal composite structure;

[0009] Processing a plurality of incompletely cut structures on the thermal composite structure, wherein adjacent incompletely cut structures are spaced by i positive electrode sheets, where i is a positive integer;

[0010] The thermal composite structure is folded along the straight line where the incompletely cut structure is located to prepare a thermal composite laminated battery core.

[0011] In a second aspect, the present application further provides a thermal composite laminated battery cell, comprising:

[0012] a plurality of first pole pieces;

[0013] a plurality of second pole pieces, wherein the polarity of the first pole piece is opposite to that of the second pole piece; and

[0014] a diaphragm comprising a plurality of main bodies and a plurality of bent portions arranged alternately and continuously;

[0015] Among them, along the thickness direction of the first pole piece, the first pole piece and the second pole piece are alternately stacked, the adjacent first pole piece and the second pole piece are separated by the main body, the bending portion is provided with an incompletely cut structure, and the diaphragm is folded at the incompletely cut structure.

[0016] In a third aspect, the present application further provides a thermal composite laminated battery cell, comprising:

[0017] negative electrode;

[0018] Multiple positive plates;

[0019] The diaphragm includes a first diaphragm and a second diaphragm, the negative electrode sheet is attached between the first diaphragm and the second diaphragm to form a thermal composite structure, the thermal composite structure includes a plurality of main parts and a plurality of bent parts arranged alternately and continuously, the bent parts are provided with an incompletely cut structure, and the positive electrode sheet is arranged between adjacent main parts along the thickness direction of the negative electrode sheet, and the projection of the positive electrode sheet in the thickness direction completely falls within the planar area of ​​the main part. Beneficial effects

[0020] The preparation method of the thermal composite laminated battery cell and the thermal composite laminated battery cell provided by the present application thermally composite the negative electrode sheet, the positive electrode sheet and the diaphragm to form a thermal composite structure, and process a plurality of incompletely cut structures on the thermal composite structure, with i positive electrode sheets between adjacent incompletely cut structures, and fold the thermal composite structure along the straight line where the incompletely cut structure is located, and the folding position is fixed to ensure the alignment of each electrode sheet during folding, which can save the subsequent shaping equipment investment and process. The structural strength at the position of the incompletely cut structure prevents the diaphragm from being pulled apart, and the position of the thermal composite structure is fixed each folding, the alignment of the thermal composite laminated battery cell is good, the occurrence of lithium plating is reduced, and the electrical performance of the thermal composite laminated battery cell in terms of cycle life, fast charging capacity and safety is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a three-dimensional diagram of a thermal composite laminated battery cell prepared by the method for preparing a thermal composite laminated battery cell provided in the present application.

[0022] FIG2 is a schematic diagram of a form of a thermal composite structure in the method for preparing a thermal composite laminated battery core provided in the present application.

[0023] FIG3 is a schematic diagram of the composite battery cell group after the thermal composite structure of FIG2 is folded.

[0024] FIG4 is a schematic diagram of a thermal composite structure of form 1 in the method for preparing a thermal composite laminated battery cell provided in the present application.

[0025] FIG5 is a schematic diagram of a thermal composite laminated battery cell after folding the thermal composite structure of form 1. FIG.

[0026] FIG6 is a partial enlarged view of point A in FIG5 .

[0027] FIG7 is a schematic diagram of a thermal composite structure of form 2 in the method for preparing a thermal composite laminated battery cell provided in this application.

[0028] FIG8 is a schematic diagram of a thermal composite laminated battery cell after folding the thermal composite structure of form II.

[0029] FIG9 is a partial enlarged view of point B in FIG8 .

[0030] FIG10 is a schematic diagram of a third form of the thermal composite structure in the method for preparing the thermal composite laminated battery cell provided in the present application.

[0031] FIG11 is a schematic diagram of a thermal composite laminated battery cell prepared by folding the thermal composite structure of form three.

[0032] FIG12 is a partial enlarged view of point C in FIG11 .

[0033] FIG13 is a schematic diagram of a fourth form of the thermal composite structure in the method for preparing the thermal composite laminated battery cell provided in the present application.

[0034] FIG14 is a schematic diagram of a thermal composite laminated battery cell prepared by folding the thermal composite structure of form four.

[0035] FIG15 is a schematic diagram of a fifth form of the thermal composite structure in the method for preparing the thermal composite laminated battery cell provided in the present application.

[0036] FIG16 is a schematic diagram of a thermal composite laminated battery cell prepared by folding the thermal composite structure of form five.

[0037] FIG17 is a partial enlarged view of point D in FIG16 .

[0038] FIG18 is a schematic diagram of a thermal composite laminated battery cell prepared by folding the thermal composite structure of form six.

[0039] FIG19 is a partial enlarged view of point E in FIG18 .

[0040] FIG20 is a labeled diagram of the thermal composite laminated battery cell provided in this application.

[0041] Description of reference numerals:

[0042] 10. Thermal composite laminated battery cell; 100. Negative electrode sheet; 100A. Single-sided negative electrode sheet; 100B. Double-sided negative electrode sheet; 110. Negative electrode current collector; 120. Negative electrode active layer; 20. Thermal composite structure; 200. Positive electrode sheet; 30. Composite battery cell group; 300. Separator; 310. First separator; 320. Second separator; 331. Horizontal portion; 332. Connecting portion; 340. Main body; 341. First main body; 342. Second main body; 350. Bend portion; 351. First bend portion; 352. Second bend portion; 400. Incompletely cut structure; 410. Through hole. Modes for Carrying Out the Invention

[0043] This application provides a method for preparing a thermal composite laminated battery cell to solve the problems of existing thermal composite laminated battery cells that require shaping and alignment equipment, such as high equipment investment, multiple processing steps, and poor alignment. The method will be described below with reference to the accompanying drawings.

[0044] 1 , 2 and 3 , the present application provides a method for preparing a thermal composite laminated battery cell, comprising the following steps:

[0045] Providing a negative electrode sheet 100, a positive electrode sheet 200, and a separator 300;

[0046] The negative electrode sheet 100, the positive electrode sheet 200 and the separator 300 are thermally composited to form a thermal composite structure 20;

[0047] A plurality of incompletely cut structures 400 are processed on the thermal composite structure 20, and the number of positive electrode sheets 200 is i between adjacent incompletely cut structures 400, where i is a positive integer.

[0048] The thermal composite structure 20 is folded along the line where the incompletely cut structure 400 is located to produce a thermal composite laminated battery cell 10. The thermal composite laminated battery cell 10 can be used as an energy storage unit of a battery, which can convert the energy stored in the cell into current and supply it to electronic devices.

[0049] Exemplarily, the thermal composite process is as follows: the positive electrode material roll, the negative electrode material roll, and the separator 300 are fed at the same time. Before entering the heating device, the electrode sheet is cut into the required size by a cutter. The combination of the negative electrode sheet 100, the positive electrode sheet 200, and the separator 300 enters the heating system under the action of rollers. The separator is a glue-coated separator, which becomes sticky after heating. After baking, the positive electrode sheet 200, the negative electrode sheet 100 and the separator 300 are thermally composited, and then rolled and cut to form a thermal composite structure 20.

[0050] It can be understood that in this embodiment, the negative electrode sheet 100, the positive electrode sheet 200 and the separator 300 are thermally composited to form a thermal composite structure 20, and an incompletely cut structure 400 is processed on the thermal composite structure 20. The incompletely cut structure 400 is located on one side of the positive electrode sheet 200. The thermal composite structure 20 is folded in a free-fall manner along the straight line where the incompletely cut structure 400 is located. The incompletely cut structure 400 is equivalent to a preset crease. The thermal composite structure 20 is folded along the preset crease to ensure that the position of each fold is fixed. Since the distance between adjacent incompletely cut structures 400 is the same, the alignment of the folded battery cells is ensured, and the subsequent shaping equipment investment and process are saved, thereby reducing the processing cost of the folded battery cells.

[0051] In some embodiments, as shown in Figures 1, 2, and 3, the thermal composite structure 20 is folded in a "Z" shape between the incompletely cut structures 400. The "Z"-shaped folding of the thermal composite structure 20 reduces material input and production costs compared to "U"-shaped winding.

[0052] In some embodiments, referring to FIG2 and FIG3 , the method for preparing a thermal composite laminated battery cell further includes the following steps: if i is greater than 1, the thermal composite structure 20 is folded along the straight line where the incompletely cut structure 400 is located to form a composite battery cell group 30 ; the composite battery cell group 30 is cut along the area between adjacent positive electrode sheets 200 to prepare i thermal composite laminated battery cells 10 .

[0053] It can be understood that in this embodiment, a plurality of positive electrode sheets 200 are spaced between adjacent incompletely cut structures 400, for example, four positive electrode sheets 200 are spaced between adjacent incompletely cut structures 400. As shown in FIG2 , several electrode layers are formed along the thickness direction of the composite battery cell group 30, and the number of positive electrode sheets 200 in each electrode layer is the same. As shown in FIG3 , the thermal composite structure 20 is folded along the incompletely cut structure 400 to form the composite battery cell group 30, which is equivalent to completing the folding of i thermal composite laminated cells at the same time. The alignment of the electrode sheets in the composite battery cell group 30 is high. When the composite battery cell group 30 is then cut into individual thermal composite laminated cells, the alignment of the cut sides is also high, and the prepared thermal composite laminated cells have a high alignment. Therefore, while improving the alignment of the thermal composite laminated cells, the processing efficiency of the thermal composite laminated cells is also improved.

[0054] In some embodiments, as shown in FIG1 , when i is 1, an incompletely cut structure 400 is provided between adjacent positive electrode sheets 200, and the thermal composite structure 20 is folded along the incompletely cut structure 400 to produce a single thermally composite laminated battery cell. The incompletely cut structure 400 acts as a pre-set crease, and the thermal composite structure 20 is folded along the pre-set crease, ensuring that the position of each fold is fixed. Since the distance between adjacent incompletely cut structures 400 is consistent, the alignment of the folded battery cell is guaranteed, and subsequent shaping equipment and process steps are saved, thereby reducing the processing cost of the folded battery cell.

[0055] Due to the different structures and stacking methods of the negative electrode sheet 100, the positive electrode sheet 200, and the separator 300, the corresponding thermal composite structures 20 are different, the specific processing steps are also different, and the structures of the corresponding processed thermal composite laminated battery cells 10 are different. The following is a detailed introduction to different forms of thermal composite structures 20.

[0056] Form 1: As shown in Figure 4, the thermal composite structure 20 includes multiple negative electrode sheets 100 with single structures, multiple positive electrode sheets 200 with single structures and a separator 300. The separator 300 is a continuous single-layer strip separator. The negative electrode sheet 100 and the positive electrode sheet 200 are rectangular in shape. The negative electrode sheet 100 is provided with a negative electrode tab, and the positive electrode sheet 200 is provided with a positive electrode tab. The negative electrode sheet 100 is located on one side of the separator 300, and the multiple negative electrode sheets 100 are arranged at intervals along the length direction Y of the separator 300. The positive electrode sheet 200 is located on the other side of the separator 300. The multiple positive electrode sheets 200 are arranged at intervals along the length direction Y of the separator 300. Along the length direction Y of the separator 300, i negative electrode sheets 100 and i positive electrode sheets 200 are arranged alternately, and the incompletely cut structure 400 is provided on the separator 300. Among them, when i is 1, the negative electrode sheets 100 and the positive electrode sheets 200 are alternately arranged along the length direction Y of the diaphragm 300, and when i is a positive integer greater than 1, along the length direction Y of the diaphragm 300, every i negative electrode sheets 100 and every i positive electrode sheets 200 are alternately arranged.

[0057] The method for preparing the thermal composite structure 20 of form 1 includes the following steps:

[0058] S10, providing negative electrode material rolls, positive electrode material rolls and separator material rolls;

[0059] S11, cutting the negative electrode material roll to prepare multiple single negative electrode sheets 100, cutting the positive electrode material roll to prepare multiple single positive electrode sheets 200, cutting the separator material roll to prepare the separator 300, and thermally compounding the multiple negative electrode sheets 100 and the multiple positive electrode sheets 200 with the separator 300 to form the above-mentioned thermal composite structure 20, as shown in Figure 4.

[0060] In S11 , after all the negative electrode sheets 100 and the separator 300 are thermally composited, all the positive electrode sheets 200 and the separator 300 are thermally composited to form a thermal composite structure 20 .

[0061] In S11, i negative electrode sheets 100 are first thermally composited with the separator 300, and then i positive electrode sheets 200 are thermally composited with the separator 300. i negative electrode sheets 100 and i positive electrode sheets 200 are thermally composited with the separator 300 alternately until the above-mentioned form 1 thermal composite structure 20 is processed.

[0062] It can be understood that in S11 of the embodiment, the required negative electrode sheet 100 and positive electrode sheet 200 can be completely cut and then thermally composited with the diaphragm 300, or the next electrode sheet can be cut during the process of thermally composite the previous electrode sheet with the diaphragm 300. The specific selection can be made according to actual conditions and is not specifically limited in this embodiment.

[0063] The thermal composite structure 20 of the first form is folded in a Z-shape to prepare a thermal composite laminated battery cell 10 , as shown in FIG. 5 and FIG. 6 .

[0064] The structure of the thermal composite laminated battery cell 10 corresponding to form one is as follows: As shown in Figures 5 and 6, the thermal composite laminated battery cell 10 includes a diaphragm 300, a negative electrode sheet 100 and a positive electrode sheet 200. The diaphragm 300 forms a plurality of main portions 340 and a plurality of bending portions 350 that are continuously and alternately arranged. One side of the negative electrode sheet 100 is compounded with one side of the diaphragm 300, and one side of the positive electrode sheet 200 is compounded with the other side of the diaphragm 300. Along the thickness direction of the negative electrode sheet 100, the positive electrode sheet 200 and the negative electrode sheet 100 are alternately arranged. Adjacent negative electrode sheets 100 and positive electrode sheets 200 are separated by the main portion 340, and an incompletely cut structure 400 is provided on the bending portion 350.

[0065] Form 2: As shown in Figures 2 and 7 , the separator 300 includes a first separator 310 and a second separator 320 in the form of a continuous strip. The thermal composite structure 20 includes N negative electrode sheet groups, M positive electrode sheet groups, a first separator 310, and a second separator 320. The negative electrode sheet group includes i negative electrode sheets 100, and the positive electrode sheet group includes i positive electrode sheets 200. N, M, and i are positive integers, and NM = 1. The number of negative electrode sheets 100 is set to be i more than the number of positive electrode sheets 200. Correspondingly, the number of negative electrode sheets 100 in each thermal composite laminated cell exceeds the number of positive electrode sheets 200 by one, ensuring that the outermost electrodes of the thermal composite laminated cell are both negative electrode sheets 100, thus meeting the electrical performance requirements of the thermal composite laminated cell.

[0066] The negative electrode sheet group is attached between the first separator 310 and the second separator 320. Along the length direction Y of the thermal composite structure 20, the positive electrode sheet groups are alternately attached to the side of the first separator 310 facing away from the negative electrode sheet group and the side of the second separator 320 facing away from the negative electrode sheet group. The projection of the positive electrode sheet 200 along the thickness direction falls completely within the plane area where the negative electrode sheet 100 is located. The incompletely cut structure 400 is arranged on the first separator 310 and / or the second separator 320 between adjacent negative electrode sheet groups.

[0067] The preparation method of the second type thermal composite structure 20 includes the following steps:

[0068] S20, providing a negative electrode material roll, a positive electrode material roll, and a separator material roll;

[0069] S21, cutting the negative electrode material roll to prepare the negative electrode sheet 100, cutting the positive electrode material roll to prepare the positive electrode sheet 200, cutting the separator material roll to prepare the separator 300, and thermally compounding the negative electrode sheet 100 and the positive electrode sheet 200 with the separator 300 to form the above-mentioned thermal composite structure 20, as shown in Figure 7.

[0070] S21 includes the following specific steps:

[0071] S211, cutting i negative electrode sheets 100 in sequence, and thermally compounding the i negative electrode sheets 100 between the first separator 310 and the second separator 320 in sequence;

[0072] S212, cutting i positive electrode sheets 200 in sequence, and thermally compounding the i positive electrode sheets 200 in sequence on the side of the first separator 310 facing away from the negative electrode sheet 100 or the side of the second separator 320 facing away from the negative electrode sheet 100;

[0073] S113 , alternately executing S211 and S212 until the above-mentioned thermal composite structure 20 is processed, as shown in FIG. 2 and FIG. 7 .

[0074] As a variation, in S21 , after all the negative electrode sheets 100 are thermally composited with the first separator 310 and the second separator 320 , all the positive electrode sheets 200 are thermally composited with the first separator 310 and the second separator 320 .

[0075] The thermal composite structure 20 of the second form is folded in a Z-shape to prepare a thermal composite laminated battery cell 10, as shown in FIG8 and FIG9.

[0076] The structure of the thermal composite laminated battery cell 10 corresponding to form 2 is as follows: As shown in Figures 8 and 9 , the thermal composite laminated battery cell 10 includes multiple negative electrode sheets 100, multiple positive electrode sheets 200, and a separator 300. The separator 300 includes a first separator 310 and a second separator 320. The first separator 310 includes a first main body 341 and a first bent portion 351, and the second separator 320 includes a second main body 342 and a second bent portion 352. A negative electrode sheet 100 is disposed between any two adjacent first main bodies 341 and second main bodies 342, and a positive electrode sheet 200 is disposed between any two adjacent first main bodies 341 and any two adjacent second main bodies 342. An incompletely cut structure 400 is disposed on the first bent portion 351 and / or the second bent portion 352. Specifically, it includes the following situations: all the incompletely cut structures 400 are arranged on the first diaphragm 310; or, all the incompletely cut structures 400 are arranged on the second diaphragm 320; or, a part of the incompletely cut structures 400 are arranged on the first diaphragm 310, and the other part of the incompletely cut structures 400 are arranged on the second diaphragm 320; or, both the first diaphragm 310 and the second diaphragm 320 are provided with incompletely cut structures 400, and the number and position of the incompletely cut structures 400 on the first diaphragm 310 and the second diaphragm 320 are the same.

[0077] As shown in Figure 9, when both the first bend 351 and the second bend 352 are provided with an incompletely cut structure 400, the projection of the incompletely cut structure 400 on the first separator 310 onto the second separator 320 overlaps with the continuous planar region enclosed by the outer contour of the incompletely cut structure 400 on the second separator 320. When the separator 300 is folded, both the first and second separators 310 and 320 fold along the same straight line, ensuring alignment of the main bodies 340 of the folded cell and improving the alignment of the thermally composite laminated cell.

[0078] For example, as shown in FIG9 , the first bend portion 351 and the second bend portion 352 can be connected in a form-fitting manner. As long as a portion of one bend portion contacts the other bend portion, the two bend portions can be considered to be in a form-fitting manner. In other embodiments, the first bend portion 351 and the second bend portion 352 may not contact each other, and this application is not limited thereto.

[0079] The embodiment of the present application limits the folding position of the diaphragm 300 by setting an incomplete cutting area, so that the diaphragm 300 can be folded at basically the same position to ensure the alignment of the negative electrode sheet 100 and the positive electrode sheet 200 in the folded battery cell, and avoid the occurrence of lithium plating piercing the diaphragm 300 due to misalignment of the negative electrode sheet 100 and the positive electrode sheet 200, thereby improving the electrical performance of the folded battery cell in terms of service life, fast charging capacity, safety, etc.

[0080] Form 3: As shown in FIG10 , the difference between Form 3 and Form 2 is that in Form 2, the negative electrode sheet 100 is disposed between the first separator 310 and the second separator 320 , while in Form 3, the positive electrode sheet 200 is disposed between the first separator 310 and the second separator 320 .

[0081] The thermal composite structure 20 includes a positive electrode sheet group, a negative electrode sheet group, a first separator 310, and a second separator 320. The positive electrode sheet group is attached between the first separator 310 and the second separator 320. Along the length direction Y of the thermal composite structure 20, the negative electrode sheet groups are alternately attached to the side of the first separator 310 facing away from the positive electrode sheet 200 and the side of the second separator 320 facing away from the positive electrode sheet 200. The projection of the positive electrode sheet 200 along the thickness direction falls completely within the plane area where the negative electrode sheet 100 is located. The incompletely cut structure 400 is provided on the first separator 310 and / or the second separator 320 between adjacent negative electrode sheet groups.

[0082] The method for preparing the thermal composite structure 20 in form 3 includes the following steps:

[0083] S30, providing negative electrode material rolls, positive electrode material rolls, and separator material rolls;

[0084] S31 , cutting the negative electrode material roll to prepare the negative electrode sheet 100 , cutting the positive electrode material roll to prepare the positive electrode sheet 200 , cutting the separator material roll to prepare the separator 300 , and thermally compounding the negative electrode sheet 100 , the positive electrode sheet 200 and the separator 300 to form the thermally compounded structure 20 .

[0085] S31 specifically includes the following steps:

[0086] S341 , sequentially cutting out i negative electrode sheets 100 , and sequentially thermally bonding the i negative electrode sheets 100 to the side of the first separator 310 facing away from the second separator 320 or the side of the second separator 320 facing away from the first separator 310 ;

[0087] S342, cutting i positive electrode sheets 200 in sequence, and thermally compounding the i positive electrode sheets 200 between the first separator 310 and the second separator 320 in sequence;

[0088] S313 , alternately executing S341 and S342 until the above-mentioned thermal composite structure 20 is processed, as shown in FIG10 .

[0089] The structure of the thermal composite laminated battery cell 10 corresponding to the third thermal composite structure 20 is as follows: The thermal composite laminated battery cell 10 includes multiple negative electrode sheets 100, multiple positive electrode sheets 200, and a separator 300. The battery cell can be used as an energy storage unit of a battery, which can convert the energy stored in the battery cell into current and supply it to electronic devices.

[0090] The negative electrode sheet 100 and the positive electrode sheet 200 can both be rectangular in shape. A negative electrode tab can be provided on the negative electrode sheet 100, and a positive electrode tab can be provided on the positive electrode sheet 200. Both the negative electrode tab and the positive electrode tab can have at least a portion of their structure located outside the separator 300. The polarity of the negative electrode sheet 100 is opposite to that of the positive electrode sheet 200, while the polarity of the negative electrode tab is the same as that of the negative electrode sheet 100, and the polarity of the positive electrode tab is the same as that of the positive electrode sheet 200.

[0091] There may be multiple separators 300, and the multiple separators may be stacked along the thickness direction of the negative electrode sheet 100. For example, the battery cell may include a double-layer separator, or may include more layers of separators.

[0092] The double-layer diaphragm 300 includes a first diaphragm 310 and a second diaphragm 320. The first diaphragm 310 and the second diaphragm 320 both include a main body 340 and a bent portion 350. Along the thickness direction X of the negative electrode sheet 100, the negative electrode sheet 100 and the positive electrode sheet 200 are alternately stacked. Adjacent negative electrode sheets 100 and positive electrode sheets 200 are separated by the main body 340. The bent portion 350 of the first diaphragm 310 is provided with an incompletely cut structure 400 and / or the bent portion 350 of the second diaphragm 320 is provided with an incompletely cut structure 400.

[0093] The side of the outermost negative electrode sheet 100 facing away from the positive electrode sheet 200 is compounded by the first separator 310 and the second separator 320 to prevent the outermost negative electrode sheet 100 from contacting and conducting electricity with the battery case, thereby improving the safety of the battery cell.

[0094] Form 4: As shown in Figure 13, the diaphragm 300 includes a first diaphragm 310 and a second diaphragm 320, and the thermal composite structure 20 includes a continuous negative electrode sheet 100, multiple positive electrode sheets 200, a first diaphragm 310 and a second diaphragm 320. The first diaphragm 310 and the second diaphragm 320 are arranged relatively parallel to each other, and the negative electrode sheet 100 is thermally composited between the first diaphragm 310 and the second diaphragm 320. i positive electrode sheets 200 are alternately thermally composited on the side of the first diaphragm 310 facing away from the negative electrode sheet 100 and the side of the second diaphragm 320 facing away from the negative electrode sheet 100.

[0095] The method for preparing the thermal composite structure 20 in Form 4 includes the following steps:

[0096] S30, providing negative electrode material rolls, positive electrode material rolls, and separator material rolls;

[0097] S31, the negative electrode sheet 100 is removed from the negative electrode material roll. During the process of moving, the negative electrode sheet 100 is thermally laminated between the first separator 310 and the second separator 320 until the length of the negative electrode sheet 100 reaches the set length and then cut. When the length of the first separator 310 and the second separator 320 reaches the set length, they are cut.

[0098] S32, cut multiple single-structure positive electrode sheets 200 from the positive electrode material roll in turn, and alternately thermally composite i positive electrode sheets 200 on the side of the first separator 310 facing away from the negative electrode sheet 100 and the side of the second separator 320 facing away from the negative electrode sheet 100 to prepare the above-mentioned thermal composite structure 20, as shown in Figure 13.

[0099] S33 , processing an incompletely cut structure 400 on the thermal composite structure 20 , wherein the incompletely cut structure 400 is disposed on the first separator 310 and / or the second separator 320 and / or the negative electrode sheet 100 .

[0100] As a variation, the positive electrode sheet 200 can also be thermally composited simultaneously with the negative electrode sheet 100. The positive electrode sheet 200 and the incompletely cut structure 400 can be processed alternately, or the incompletely cut structure 400 can be processed simultaneously after the thermally composite structure 20 is fully formed.

[0101] It can be understood that, compared with other implementations, the negative electrode sheet 100 in this embodiment is a continuous strip structure, which saves the step of cutting the negative electrode sheet 100, reduces the processing steps of the thermal composite laminated battery cell, and improves processing efficiency.

[0102] The thermal composite structure 20 of the fourth form is folded in a Z-shape to prepare a thermal composite laminated battery cell 10, as shown in FIG14 .

[0103] The structure of the thermal composite laminated battery cell 10 corresponding to form four is as follows: As shown in FIG. 14 , the thermal composite laminated battery cell 10 includes a continuous negative electrode sheet 100 , a plurality of positive electrode sheets 200 and a separator 300 .

[0104] The separator 300 includes a first separator 310 and a second separator 320. Before folding, the first separator 310 and the second separator 320 are continuous strip structures. The first separator 310 and the second separator 320 have the same size and shape. The shape of the negative electrode sheet 100 is the same as that of the first separator 310 and the second separator 320. The size of the first separator 310 and the second separator 320 is larger than that of the negative electrode sheet 100. The negative electrode sheet 100 is arranged between the first separator 310 and the second separator 320. The first separator 310 and the negative electrode sheet 100 are arranged between the first separator 310 and the second separator 320. The electrode sheets 100 and the second separator 320 are stacked to form a thermal composite structure 20. The thermal composite structure 20 is folded to form multiple horizontal portions 331 and multiple connecting portions 332. The connecting portions 332 connect adjacent horizontal portions 331 and are provided with an incompletely cut structure 400. Along the thickness direction X, the positive electrode sheets 200 and the horizontal portions 331 are alternately arranged. The positive electrode sheets 200 are arranged between adjacent horizontal portions 331, and the projection of the positive electrode sheets 200 in the thickness direction completely falls within the planar area of ​​the horizontal portion 331. The planar area of ​​the horizontal portion 331 is the continuous planar area enclosed by the outer contour of the horizontal portion 331 projected along the thickness direction of the positive electrode sheet 200. The material of the separator 300 can be polypropylene, polyethylene, polyethylene terephthalate, polybutylene terephthalate, ethylene-propylene copolymer, cellulose, etc.

[0105] Form 5: Based on the above Form 4, as shown in Figures 15 and 17, the negative electrode sheet 100 includes a continuous negative electrode current collector 110 and multiple negative electrode active layers 120. Negative electrode active layers 120 are provided on both sides of the negative electrode current collector 110. The negative electrode active layers 120 are arranged opposite to the positive electrode sheet 200, and the projection of the positive electrode sheet 200 in the thickness direction falls within the planar area of ​​the negative electrode active layer 120.

[0106] All negative electrode active layers 120 may be etched out on the continuous negative electrode sheet 100 first, and then the negative electrode sheet 100 is thermally composited with the first separator 310 and the second separator 320. Alternatively, the negative electrode active material on the negative electrode sheet 100 may be etched away during the thermal composite process of the negative electrode sheet 100 and the first separator 310 and the second separator 320.

[0107] In some embodiments, the negative electrode current collector 110 located between adjacent negative electrode active layers 120 is laminated with the first separator 310 and the second separator 320 .

[0108] In this embodiment, the area between adjacent negative active layers 120 corresponds to the folded area of ​​the negative electrode sheet 100, which reduces the occurrence of short circuits in the thermal composite laminated battery cell caused by folding and powder shedding, thereby improving the reliability of the thermal composite laminated battery cell.

[0109] The thermal composite structure 20 of the fifth form is folded in a Z-shape to prepare a thermal composite laminated battery cell 10, as shown in FIG. 16 and FIG. 17 .

[0110] The structure of the thermally composite laminated battery cell 10 prepared from the thermally composite structure 20 of form five is as follows: Referring to Figures 16 and 17 , the thermally composite laminated battery cell 10 includes a negative electrode sheet 100, multiple positive electrode sheets 200, and a separator 300. The negative electrode sheet 100 includes a negative electrode current collector 110 and multiple negative electrode active layers 120, with the negative electrode active layers 120 spaced apart on either side of the negative electrode current collector 110. The separator 300 includes a first separator 310 and a second separator 320, with the negative electrode sheet 100 thermally composited between the first separator 310 and the second separator 320. The negative electrode sheet 100 and the separator 300 form a composite laminate. The thermally composite structure 20 is folded to form multiple horizontal portions 331 and multiple connecting portions 332. The connecting portions 332 connect adjacent horizontal portions 331, and the connecting portions 332 are provided with an incompletely cut structure 400. Along the thickness direction X, the positive electrode sheets 200 and the horizontal portions 331 are arranged alternately. Positive electrode sheets 200 are arranged between adjacent horizontal portions 331, and the projections of the positive electrode sheets 200 in the thickness direction X completely fall within the planar area of ​​the horizontal portions 331. The negative electrode sheets 100 in the horizontal portions 331 include a negative electrode current collector 110 and a negative electrode active layer 120. The negative electrode active layer 120 is provided on both sides of the negative electrode current collector 110, and the projections of the positive electrode sheets 200 in the thickness direction X completely fall within the planar area of ​​the negative electrode active layer 120. The connecting portions 332 correspond to the negative electrode current collectors 110 between adjacent negative electrode active layers 120.

[0111] In this embodiment, the negative electrode sheet 100 is formed by a continuous negative electrode current collector 110 and multiple individual negative electrode active layers 120. The size of the negative electrode current collector 110 is smaller than that of the separator 300, but larger than that of at least two positive electrode sheets 200. The size of the negative electrode active layer 120 is larger than that of the positive electrode sheet 200. The negative electrode active layer 120 corresponds to the positive electrode sheet 200. The area between adjacent negative electrode active layers 120 corresponds to the folding structure, where the negative electrode active layer 120 is not provided. This prevents powder loss during folding, which can cause short circuits in the thermal composite laminated cell, and improves the reliability of the thermal composite laminated cell.

[0112] In some embodiments, laser etching is used to remove the negative electrode active material on the negative electrode sheet 100 to form multiple negative electrode active layers 120. Laser etching of the negative electrode sheet 100 provides good etching effects and is simple to operate. Furthermore, the etching operation can be performed while the negative electrode sheet 100 is being transported, which does not increase processing time and improves processing efficiency.

[0113] In some embodiments, the distances between adjacent negative active layers 120 are the same.

[0114] It can be understood that a plurality of negative electrode active layers 120 are formed by etching the negative electrode active material, and the distances between the negative electrode active layers 120 are set to be the same to facilitate processing.

[0115] In some embodiments, as shown in FIG15 , the distance between adjacent negative electrode active layers 120 is L, where 1 mm ≤ L ≤ 3 mm. The value of L can be 1 mm, 1.3 mm, 1.8 mm, 2.5 mm, 2.7 mm, 3 mm, or other values ​​not listed.

[0116] In this embodiment, the distance between adjacent negative electrode active layers 120 is reasonably designed to avoid excessive negative electrode active material in the bending area or the cutting area, which may cause powder loss during folding or cutting, while ensuring that the negative electrode active layer 120 can cover the positive electrode sheet 200 and ensure the performance of the thermal composite laminated battery cell.

[0117] In some embodiments, as shown in FIG16 , the thickness of the negative electrode current collector 110 is D1, where 4 μm ≤ D1 ≤ 6 μm. The value of D1 can be 4 μm, 4.3 μm, 5 μm, 5.2 μm, 6 μm, or other unspecified values. The thickness of the negative electrode current collector 110 is designed to meet the electrical requirements of the negative electrode sheet 100.

[0118] In some embodiments, as shown in FIG16 , the thickness of the negative electrode active layer 120 is D2, where 50 μm ≤ D2 ≤ 200 μm. The thickness of the negative electrode active layer 120 is D2, where 50 μm ≤ D2 ≤ 200 μm. The value of D2 can be 50 μm, 65 μm, 74 μm, 81 μm, 98 μm, 105 μm, 111 μm, 127 μm, 133 μm, 147 μm, 155 μm, 164 μm, 178 μm, 183 μm, 196 μm, 200 μm, or other values ​​not specified. The thickness of the negative electrode active layer 120 is designed to meet the electrical requirements of the negative electrode sheet 100.

[0119] Form six: The thermal composite structure 20 includes n double-sided negative electrode sheet groups, M positive electrode sheet groups, a first separator 310 and a second separator 320, the double-sided negative electrode sheet group includes i double-sided negative electrode sheets 100B, and the positive electrode sheet group includes i positive electrode sheets, n and m are positive integers, Mn=1, wherein the positive electrode sheet group is located between the first separator 310 and the second separator 320, and along the length direction Y of the thermal composite structure 20, the double-sided negative electrode sheet group and the positive electrode sheet group are alternately arranged, and the double-sided negative electrode sheet group is thermally composited on the side of the first separator 310 away from the positive electrode sheet group and the side of the second separator 320 away from the positive electrode sheet group. The projection of the positive electrode sheet 200 along the thickness direction falls on the plane area where the double-sided negative electrode sheet 100B is located, and the incomplete cutting structure 400 is arranged on the first separator 310 and / or the second separator 320 between adjacent double-sided negative electrode sheet groups.

[0120] For example, as shown in FIG. 19 , a double-sided negative electrode sheet 100B includes a negative electrode current collector 110 and a negative electrode active layer 120 . The negative electrode active layer 120 is disposed on both sides of the negative electrode current collector 110 .

[0121] Correspondingly, the method for preparing the thermal composite laminated battery cell further includes the following steps:

[0122] Two single-sided electrode groups are provided, each of which includes i single-sided negative electrode sheets 100A;

[0123] After the thermal composite structure 20 is folded along the straight line where the incompletely cut structure 400 is located, the single-piece electrode groups are thermally composited on the outermost sides of the folded thermal composite structure 20 to prepare a thermal composite laminated battery cell 10, as shown in Figures 18 and 19.

[0124] For example, as shown in FIG. 19 , a single-sided negative electrode sheet 100A includes a negative electrode current collector 110 and a negative electrode active layer 120 . The negative electrode active layer 120 is disposed on one side of the negative electrode current collector 110 .

[0125] The structure of the thermal composite laminated battery cell 10 prepared by the thermal composite structure 20 of form six is ​​as follows:

[0126] The thermal composite laminated battery cell 10 includes a negative electrode sheet 100, a positive electrode sheet 200, and a separator 300. The separator 300 includes a plurality of main portions 340 and a plurality of folds 350 arranged alternately and continuously. The main portions 340 are stacked along the thickness direction X of the negative electrode sheet 100. Adjacent main portions 340 are connected by folds 350. The folds 350 are provided with incomplete cutout structures 400, and the separator 300 is bent at the incomplete cutout structures 400. Along the thickness direction X of the negative electrode sheet 100, the negative electrode sheets 100 and the positive electrode sheets 200 are stacked alternately, with each positive electrode sheet 200 positioned between two negative electrode sheets 100. Adjacent negative electrode sheets 100 and positive electrode sheets 200 are separated by the main portions 340. The two outermost negative electrode sheets 100 are single-sided negative electrode sheets 100A, while the remaining negative electrode sheets 100 are double-sided negative electrode sheets 100B. The projections of the positive electrode sheet 200 and the negative electrode sheet 100 along the thickness direction of the negative electrode sheet 100 completely fall within the planar area of ​​the main body 340 between them, so that the main body 340 can completely separate the negative electrode sheet 100 and the positive electrode sheet 200, preventing the positive electrode sheet 200 from contacting the negative electrode sheet 100 and causing a short circuit. The planar area of ​​the main body 340 is the continuous planar area enclosed by the outer contour of the main body 340 projected along the thickness direction of the negative electrode sheet 100.

[0127] It can be understood that before folding, the diaphragm 300 is in a continuous strip structure, and the negative electrode sheet 100 and the positive electrode sheet 200 are compounded on the main body 340 of the diaphragm 300 to form a thermal composite structure 20, and an incompletely cut structure 400 is provided on the diaphragm 300. The distance between the two sides of the incompletely cut structure 400 and the negative electrode sheet 100 on its side is the same or approximately the same, and the thermal composite structure 20 is folded along the straight line where the incompletely cut structure 400 is located. The folding position is fixed, which improves the alignment during the folding process, avoids the situation where lithium plating pierces the diaphragm 300 due to the misalignment of the negative electrode sheet 100 and the positive electrode sheet 200, and improves the electrical performance of the folded battery cell. The outermost negative electrode sheet 100 is set as a single-sided negative electrode sheet 100A, and the outermost side of the single-sided negative electrode sheet 100A does not need to be provided with an active material layer, thereby reducing material input and reducing costs.

[0128] In this embodiment, two types of negative electrode sheets 100 are provided. A double-sided negative electrode sheet 100B, a first separator 310, a second separator 320, and a positive electrode sheet 200 are thermally composited to form a thermal composite structure 20. After the thermal composite structure 20 is folded, the single-sided negative electrode sheet 100A is bonded to the outermost side of the folded thermal composite structure 20. The negative electrode active layer 120 of the single-sided negative electrode sheet 100A is bonded to the separator 300. The outermost negative electrode sheet 100 does not require a coating, reducing separator material usage and lowering costs.

[0129] In some embodiments, as shown in FIG. 1 and FIG. 20 , the incompletely cut structure 400 includes a plurality of through holes 410 , and the plurality of through holes 410 are spaced apart along the width direction Z of the thermal composite structure 20 .

[0130] A plurality of through holes 410 are arranged in an array, and a plurality of columns of through holes 410 are arranged along the length direction Y of the diaphragm 300. Each column of through holes 410 can be arranged along the width direction Z of the diaphragm 300. Exemplarily, the arrangement directions of the plurality of columns of through holes 410 can be parallel to each other. In some other embodiments, there may be an angle between the arrangement direction of at least one column of through holes 410 and the arrangement direction of the through holes in other columns. Exemplarily, the angle may be less than or equal to 10°, for example, 1°, 2°, 5°, etc. In some other embodiments, the angle may also be greater than 10°, and the embodiments of the present application are not limited to this. Exemplarily, the plurality of through holes 410 in one of any two columns of through holes 410 may be arranged one-to-one relative to the plurality of through holes 410 in the other column. In some other embodiments, the plurality of through holes 410 in at least one column may be staggered with the plurality of through holes 410 in other columns. If the projections of two through holes 410 in the length direction Y of the diaphragm 300 do not overlap, the two through holes 410 can be considered to be staggered. For example, the through holes 410 in one of two adjacent rows of through holes 410 can be staggered with the through holes 410 in the other row.

[0131] In some other embodiments, the incompletely cut structure 400 may also include a plurality of slits spaced apart from each other. The slits may be formed by cutting the diaphragm with a knife or the like. The incompletely cut structure 400 may also be a textured structure.

[0132] It is understood that when the separator 300 is a single-layer separator and the negative electrode sheet 100 and the positive electrode sheet 200 are discontinuous electrodes, the incompletely cut structure 400 is a through hole 410 that penetrates the single-layer separator, and the separators between adjacent through holes 410 remain connected. When the separator 300 is a double-layer separator and the negative electrode sheet 100 and the positive electrode sheet 200 are discontinuous electrodes, the incompletely cut structure 400 is a through hole that penetrates the first separator 310 and / or the second separator 320.

[0133] Part of the material on the diaphragm 300 is cut off to form a through hole 410. Along the width direction Z of the diaphragm 300, the diaphragm 300 is not completely cut. Compared with completely cutting the diaphragm 300, shrinkage and wrinkling will not occur due to disconnection changes. Moreover, the diaphragm 300 around the through hole 410 is weak. During free fall folding, the diaphragm 300 will fold along the position of the through hole 410 to achieve precise position folding, which is beneficial to the alignment of the negative electrode sheet 100 and the positive electrode sheet 200 in the folded battery cell.

[0134] In some embodiments, as shown in FIG. 14 and FIG. 17 , the incompletely cut structure 400 includes a plurality of through holes 410 penetrating the separator 300 and the negative electrode sheet 100 . The plurality of through holes 410 are spaced apart along the width direction Z of the thermal composite structure 20 .

[0135] It can be understood that when the diaphragm 300 includes the first diaphragm 310 and the second diaphragm 320, and the negative electrode sheet 100 is a continuous electrode sheet, the through hole 410 of the incompletely cut structure 400 passes through the first diaphragm 310, the second diaphragm 320 and the negative electrode sheet 100, and the first diaphragm 310 and the second diaphragm 320 around the through hole 410 are fitted with the negative electrode sheet 100 around the through hole 410, completely covering the negative electrode sheet 100 around the through hole 410, preventing leakage or short circuit, and improving the reliability of the battery cell. In addition, the through hole 410 passes through the first diaphragm 310, the second diaphragm 320 and the negative electrode sheet 100, reducing the folding resistance of the first diaphragm 310, the second diaphragm 320 and the negative electrode sheet 100 at this position, which is beneficial to the folding of the first diaphragm 310, the second diaphragm 320 and the negative electrode sheet 100, realizing fixed-point folding, and improving the alignment of the thermal composite laminated battery cell.

[0136] 1 and 20 , the spacing between adjacent through holes 410 is the same, where the spacing between adjacent through holes 410 refers to the distance between one side of a through hole 410 and one side of an adjacent through hole 410 along the width direction Z of the diaphragm 300 .

[0137] In this embodiment, the intervals between adjacent through holes 410 are the same, which is conducive to processing the through holes 410 on the diaphragm 300 and the negative electrode sheet 100, so that the strength of the diaphragm 300 and the negative electrode sheet 100 on the straight line where the multiple through holes 410 are located is the same, avoiding the diaphragm 300 and the negative electrode sheet 100 from being pulled apart during the folding process due to local weak strength.

[0138] In some embodiments, as shown in FIG20 , the spacing between adjacent through-holes 410 along the width direction Z of the thermal composite structure 20 is S1, where 5 mm ≤ S1 ≤ 20 mm. The value of S1 can be 5.0 mm, 5.2 mm, 5.7 mm, 7.8 mm, 9.0 mm, 10.5 mm, 11.5 mm, 12.3 mm, 13.9 mm, 14.0 mm, 15.7 mm, 16.1 mm, 17.4 mm, 18.0 mm, 19.6 mm, 20.0 mm, or other values ​​not specified.

[0139] It can be understood that the spacing distance between the through holes 410 in this embodiment is reasonably designed to avoid the situation where the distance between the through holes 410 is too small and the number of through holes 410 is too large, which affects the structural strength of the diaphragm 300 and the negative electrode sheet 100. It also avoids the situation where the distance between the through holes 410 is too large and the number of through holes 410 is too small, which fails to play a role in positioning and folding during the folding process.

[0140] In some embodiments, the through hole 410 is in a circular, rectangular, or irregular shape. In addition to circular and rectangular shapes, the through hole 410 can also be in a regular shape such as an ellipse, a hexagon, or an octagon.

[0141] In some embodiments, as shown in FIG. 20 , through-hole 410 has a first dimension L1 and a second dimension W1. The first dimension is the distance between two parallel planes that virtually abut the two side walls of through-hole 410, and the second dimension is the distance between two parallel planes that virtually abut the two end walls of through-hole 410. Here, 1 mm ≤ L1 ≤ 20 mm, and / or 1 mm ≤ W1 ≤ 2 mm. The two side walls refer to the side walls extending along the width direction ZZ of diaphragm 300, and the two end walls refer to the side walls extending along the length direction Y of diaphragm 300. In this embodiment, the value of L1 can be 1.1 mm, 1.2 mm, 1.5 mm, 2.3 mm, 3.4 mm, 4.2 mm, 5.0 mm, 6.8 mm, 7.8 mm, 8.8 mm, 9.0 mm, 10.3 mm, 11.1 mm, 12.5 mm, 13.8 mm, 14.1 mm, 15.0 mm, 16.6 mm, 17.7 mm, 18.2 mm, 19.1 mm, 20.0 mm, or other unspecified values. In this embodiment, the value of W1 can be 1.1 mm, 1.2 mm, 1.4 mm, 1.5 mm, 1.8 mm, 2.0 mm, or other unspecified values.

[0142] It should be noted that the two parallel planes virtually abutting the through-hole 410 are introduced only to facilitate understanding of the first and second dimensions and do not actually exist in the present application. For example, if the through-hole 410 has a rectangular outer contour, to determine the first and second dimensions, two sets of planes can be hypothesized to exist, each set of planes comprising two parallel planes spaced apart, with the two parallel planes in each set being able to virtually abut the two opposing walls of the through-hole 410. In this case, there is a distance between the two parallel planes in each set, with the first dimension being the distance between the two planes abutting the two side walls of the through-hole 410, and the second dimension being the distance between the two planes abutting the two end walls of the through-hole 410.

[0143] It can be understood that the size of the through hole 410 in this embodiment is reasonably designed to avoid the length and width of the through hole 410 being too long or too short, to avoid the structural strength of the diaphragm 300 and the negative electrode sheet 100 being affected by the through hole 410 being too large, or to avoid the through hole 410 being too small and failing to play a role in positioning and folding during the folding process.

[0144] In some embodiments, as shown in Figures 1, 6, 9, 12, 14 and 17, the length of the separator 300 is greater than the length of the negative electrode sheet 100, and the width of the separator 300 is greater than the width of the negative electrode sheet 100.

[0145] It can be understood that, regardless of whether the negative electrode sheet 100 is a single electrode sheet or a continuous electrode sheet, the projection of the negative electrode sheet 100 on the separator 300 completely falls within the range of the separator 300. The negative electrode sheet 100 and the positive electrode sheet 200 are separated by the separator 300, meeting the electrical safety requirements of the thermal composite laminated battery cell and improving the reliability of the thermal composite laminated battery cell.

[0146] In some embodiments, as shown in FIG20 , the distance between the long side of the negative electrode sheet 100 and the side of the separator 300 is S4. The separator 300 includes a starting end and a terminating end. The distance between the starting end of the separator 300 and the wide side of the negative electrode sheet 100 near the starting end is S5, where 2 mm ≤ S4 ≤ 4 mm, and 1 mm ≤ S5 ≤ 3 mm. On the outside, the distance between the terminating end of the separator 300 and the wide side of the negative electrode sheet 100 near the terminating end is the same as S5.

[0147] In this embodiment, the value of S4 can be 2.1mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.9mm, 3mm, 3.2mm, 3.3mm, 3.5mm, 3.7mm, 3.8mm, 3.9mm, 4mm or other unlisted values.

[0148] In this embodiment, the value of S5 can be 1.1mm, 1.2mm, 1.4mm, 1.5mm, 1.7mm, 1.8mm, 2mm, 2.1mm, 2.2mm, 2.3mm, 2.5mm, 2.6mm, 2.8mm, 2.9mm, 3mm or other unlisted values.

[0149] In this embodiment, the values ​​of S4 and S5 may be the same or different, and this embodiment does not impose any specific limitation.

[0150] It is understandable that the sizes of the negative electrode sheet 100 and the separator 300 are designed to be reasonable. While ensuring electrical safety, the separator 300 is prevented from being too large and causing material waste, thereby reducing processing costs.

[0151] In some embodiments, as shown in Figures 1, 6, 9, 12, 14, and 17, the length of the negative electrode sheet 100 is greater than the length of the positive electrode sheet 200, and the width of the negative electrode sheet 100 is greater than the width of the positive electrode sheet 200. Along the thickness direction of the negative electrode sheet 100, the projection of the positive electrode sheet 200 completely falls within the range of the negative electrode sheet 100.

[0152] It can be understood that the size of the negative electrode sheet 100 is designed to be larger than the size of the positive electrode sheet 200. During the charging process of the lithium battery, the negative electrode sheet 100 can completely receive the lithium ions of the positive electrode sheet 200 and will not form lithium dendrites, thereby avoiding the formation of lithium dendrites that pierce the diaphragm 300, causing a short circuit and thermal runaway, thereby improving the reliability of the battery.

[0153] In some embodiments, as shown in Figures 1, 6, 9, 17, and 20, the positive electrode sheet 200 and the negative electrode sheet 100 are both single-piece electrodes. The distance between the long side of the positive electrode sheet 200 and the long side of the negative electrode sheet 100 is S2, and the distance between the wide side of the positive electrode sheet 200 and the wide side of the negative electrode sheet 100 is S3, where 1 mm ≤ S2 ≤ 3 mm, and 1 mm ≤ S3 ≤ 3 mm. The values ​​of S2 and S3 can be 1 mm, 1.3 mm, 2 mm, 2.6 mm, 3 mm, or other values ​​not specified.

[0154] The distance S2 between the long side of the positive electrode sheet 200 and the long side of the negative electrode sheet 100 and the distance S3 between the wide side of the positive electrode sheet 200 and the wide side of the negative electrode sheet 100 may be the same or different, which is not specifically limited in this embodiment.

[0155] It can be understood that in this embodiment, the distance S2 between the long side of the positive electrode sheet 200 and the long side of the negative electrode sheet 100 and the distance S3 between the wide side of the positive electrode sheet 200 and the wide side of the negative electrode sheet 100 are reasonably designed to avoid material waste and increased cost due to excessive size while meeting the battery safety performance.

[0156] Referring to Figures 1, 5, 6, 8, and 9, the present application provides a thermal composite laminated battery cell 10 comprising a plurality of first electrode sheets, a plurality of second electrode sheets, and a separator 300. The battery cell can be used as an energy storage unit of a battery, which can convert the energy stored in the battery cell into current and supply it to an electronic device. For example, the first electrode sheet can be a positive electrode sheet 200, and accordingly, the second electrode sheet can be a negative electrode sheet 100; in some other embodiments, the first electrode sheet can also be a negative electrode sheet 100, and accordingly, the second electrode sheet can also be a positive electrode sheet 200. The embodiments of the present application are described using the example of the first electrode sheet being the positive electrode sheet 200 and the second electrode sheet being the negative electrode sheet 100. The scheme in which the first electrode sheet is the negative electrode sheet 100 and the second electrode sheet is the positive electrode sheet 200 can be adaptively adjusted with reference to the scheme in which the first electrode sheet is the positive electrode sheet 200 and the second electrode sheet is the negative electrode sheet 100, and will not be further described here.

[0157] In this embodiment, the first pole piece and the second pole piece are cut from a first pole piece roll and a second pole piece roll. The shapes of the first pole piece and the second pole piece can both be rectangular. A first pole ear can be provided on the first pole piece, and a second pole ear can be provided on the second pole piece. The first pole ear and the second pole ear can both have at least a partial structure located on the outside of the diaphragm 300. The polarity of the first pole piece is opposite to that of the second pole piece, the polarity of the first pole ear is the same as that of the first pole piece, and the polarity of the second pole ear is the same as that of the second pole piece. For example: the first pole ear and the first pole piece are both positive, and the second pole ear and the second pole piece are both negative; or the first pole ear and the first pole piece are both negative, and the second pole ear and the second pole piece are both positive.

[0158] In some embodiments, referring to FIG1 and FIG11 , along the thickness direction X of the first electrode sheet, the projections of all first electrode tabs overlap, and the projections of all second electrode tabs overlap. The first electrode tabs are stacked with the first electrode sheet, and the second electrode tabs are stacked with the second electrode sheet. Adjacent first electrode tabs are spaced apart by the thickness of the main body 340, and the projections of all first electrode tabs are at the same position. Adjacent second electrode tabs are spaced apart by the thickness of the main body 340, and the projections of all second electrode tabs are at the same position. This facilitates welding of all first electrode tabs and all second electrode tabs together, and the first electrode tabs and the second electrode tabs occupy little space.

[0159] In some embodiments, referring to Figures 1 and 11 , the first tab on the first electrode piece and the second tab on the second electrode piece are arranged side by side as projected onto the plane where the main body 340 is located. The main body 340 is flanked by the first electrode piece and the second electrode piece, respectively. The first tab on the first electrode piece and the second tab on the second electrode piece are spaced apart as projected onto the plane where the main body 340 is located, to prevent interference between the first tab and the second tab, thereby ensuring electrical safety.

[0160] In some embodiments, referring to Figures 1, 6, 8 and 9, the diaphragm 300 is a continuous diaphragm 300, and the diaphragm 300 includes a plurality of main bodies 340 and a plurality of bending portions 350 that are alternately and continuously arranged. The plurality of main bodies 340 are stacked along the thickness direction X of the first pole piece, and two adjacent main bodies 340 are connected by a bending portion 350. The bending portion 350 is provided with an incompletely cut structure 400, and the diaphragm 300 is bent at the incompletely cut structure 400.

[0161] In some embodiments, referring to Figures 6, 8, and 9, the first and second pole pieces are alternately stacked along the thickness direction of the first pole piece, and adjacent first and second pole pieces are separated by a main body portion 340. The projections of the first and second pole pieces along the thickness direction of the first pole piece completely fall within the planar area of ​​the main body portion 340 between them, so that the main body portion 340 can completely separate the first and second pole pieces, preventing the first and second pole pieces from contacting and causing a short circuit. The planar area of ​​the main body portion 340 is a continuous planar area enclosed by the outer contour of the main body portion 340 projected along the thickness direction of the first pole piece.

[0162] As can be understood, referring to FIG7 , before folding, the diaphragm 300 is a continuous strip-like structure. The first and second pole pieces are composited on the main body 340 of the diaphragm 300 to form a thermal composite structure 20. An incompletely cut structure 400 is provided on the diaphragm 300. The distance between the two sides of the incompletely cut structure 400 and the first pole piece on the side on which it is located is the same. The thermal composite structure 20 is folded along the straight line where the incompletely cut structure 400 is located. The folding position is fixed, and the dimensions between the folding positions are the same, which improves the alignment during the folding process, avoids the occurrence of lithium plating piercing the diaphragm 300 due to misalignment of the first and second pole pieces, and improves the electrical performance of the folded battery cell.

[0163] In some embodiments, referring to Figures 1, 7, 8, 9, 10, 11, and 12, there may be multiple separators 300, and multiple separators 300 may be stacked along the thickness direction of the first electrode sheet. For example, the battery cell may include a double-layer separator 300, or may include more layers of separators 300. The embodiments of this application are described using a double-layer separator 300 as an example. Embodiments with other numbers of separators 300 can be adaptively designed based on the embodiment of the double-layer separator 300.

[0164] In some embodiments, referring to Figures 1, 9 and 12, the double-layer diaphragm 300 includes a first diaphragm 310 and a second diaphragm 320, and the first diaphragm 310 and the second diaphragm 320 both include a main body 340 and a bent portion 350. Along the thickness direction X of the first pole piece, the first pole piece and the second pole piece are alternately stacked, and the adjacent first pole pieces and the second pole pieces are separated by the main body 340. The bent portion 350 of the first diaphragm 310 is provided with an incompletely cut structure 400 and / or the bent portion 350 of the second diaphragm 320 is provided with an incompletely cut structure 400. Specifically, it includes the following situations: all the incompletely cut structures 400 are arranged on the first diaphragm 310; or, all the incompletely cut structures 400 are arranged on the second diaphragm 320; or, a part of the incompletely cut structures 400 are arranged on the first diaphragm 310, and the other part of the incompletely cut structures 400 are arranged on the second diaphragm 320; or, both the first diaphragm 310 and the second diaphragm 320 are provided with incompletely cut structures 400, and the number and position of the incompletely cut structures 400 on the first diaphragm 310 and the second diaphragm 320 are the same.

[0165] For example, as shown in Figure 9, the battery cell may include a dual diaphragm 300, namely a first diaphragm 310 and a second diaphragm 320. The first diaphragm 310 includes a first main body 341 and a first bend 351, and the second diaphragm 320 includes a second main body 342 and a second bend 352. A first pole piece is provided between any two adjacent first main bodies 341 and second main bodies 342, and a second pole piece is provided between any two adjacent first main bodies 341 and any two adjacent second main bodies 342. An incompletely cut structure 400 is provided on both the first diaphragm 310 and the second diaphragm 320. The projection of the incompletely cut structure 400 on the first diaphragm 310 on the second diaphragm 320 overlaps with the continuous planar area enclosed by the outer contour of the incompletely cut structure 400 on the second diaphragm 320. When the separator 300 is folded, the first separator 310 and the second separator 320 are folded along the same straight line, ensuring that the main bodies 340 of the layers in the folded battery cell are aligned, thereby improving the alignment of the thermal composite laminated battery cell 10 .

[0166] For example, the first bend portion 351 and the second bend portion 352 can be connected in a form-fitting manner. As long as a portion of the structure of one bend portion 350 contacts the other bend portion 350, the two bend portions 350 can be considered to be connected in a form-fitting manner. In other embodiments, the first bend portion 351 and the second bend portion 352 may not contact each other, and this application is not limited to this.

[0167] In this embodiment, referring to Figures 7 and 10 , before folding, the first diaphragm 310 and the second diaphragm 320 are both continuous strip structures. The first electrode plate is composited between the first diaphragm 310 and the second diaphragm 320. The second electrode plate is composited on the side of the first diaphragm 310 facing away from the first electrode plate and on the side of the second diaphragm 320 facing away from the first electrode plate. An incompletely cut structure 400 is located between adjacent first electrode plates. The distance between the two sides of the incompletely cut structure 400 is the same as the distance between the first electrode plates on its side. The diaphragm 300 (i.e., the first diaphragm 310 and the second diaphragm 320) folds at the incompletely cut structure 400. The incompletely cut structure 400 can relieve the stress generated by folding, making it easier for the diaphragm 300 to fold at the incompletely cut structure 400, thereby limiting the folding position and improving folding quality and efficiency.

[0168] The embodiment of the present application limits the folding position of the diaphragm 300 by setting an incomplete cut portion, so that the diaphragm 300 can be folded basically at the same position to ensure the alignment of the first electrode and the second electrode in the folded battery cell, and reduce the occurrence of lithium plating piercing the diaphragm 300 due to misalignment of the first electrode and the second electrode, thereby improving the electrical performance of the folded battery cell in terms of service life, fast charging capacity, safety, etc.

[0169] In some embodiments, referring to Figures 1, 6, 9 and 12, the incompletely cut structure 400 includes a plurality of through holes 410 penetrating the diaphragm 300, and the plurality of through holes 410 are spaced apart along the width direction Z of the diaphragm 300. Alternatively, the plurality of through holes 410 are arranged in an array, and are arranged in a plurality of rows of through holes 410 along the length direction Y of the diaphragm 300. Each row of through holes 410 can be arranged along the width direction Z of the diaphragm 300. For example, the arrangement directions of the plurality of rows of through holes 410 can be parallel to each other. In some other embodiments, there may also be an angle between the arrangement direction of at least one row of through holes 410 and the arrangement direction of other rows of through holes 410. For example, the angle may be less than or equal to 10°, for example, 1°, 2°, 5°, etc. In some other embodiments, the angle may also be greater than 10°, and the embodiments of the present application are not limited to this. For example, the multiple through-holes 410 in one of any two rows of through-holes 410 can be arranged one-to-one with the multiple through-holes 410 in the other row. In other embodiments, the multiple through-holes 410 in at least one row can be staggered with the multiple through-holes 410 in the other row. If the projections of the two through-holes 410 in the length direction Y of the diaphragm 300 do not overlap, the two through-holes 410 can be considered to be staggered. For example, the multiple through-holes 410 in one of two adjacent rows of through-holes 410 can be staggered with the multiple through-holes 410 in the other row.

[0170] In some other embodiments, the incompletely cut structure 400 may also include a plurality of slits spaced apart from each other. The slits may be formed by cutting the diaphragm 300 with a knife or the like. In addition, the incompletely cut structure 400 may also be a textured structure.

[0171] When the diaphragm 300 includes a first diaphragm 310 and a second diaphragm 320, the incompletely cut structure 400 on the first diaphragm 310 is a through hole 410 that passes through the first diaphragm 310, and the incompletely cut structure 400 on the second diaphragm 320 is a through hole 410 that passes through the second diaphragm 320. When both the first diaphragm 310 and the second diaphragm 320 are provided with the incompletely cut structure 400, the through hole 410 on the first diaphragm 310 and the through hole 410 on the second diaphragm 320 are arranged opposite each other, and the through hole 410 on the first diaphragm 310 and the through hole 410 on the second diaphragm 320 pass through each other.

[0172] It can be understood that by providing multiple through holes 410 in the diaphragm 300 to form an incompletely cut structure 400, local material on the diaphragm 300 is cut off, and along the width direction Z of the diaphragm 300, the diaphragm 300 is not completely cut, so that the diaphragm 300 around the through holes 410 is weak. During free fall folding, the diaphragm 300 will fold along the position of the through holes 410 to achieve precise position folding, which is conducive to the alignment of the first electrode and the second electrode in the folded battery cell.

[0173] In some embodiments, the intervals between adjacent through holes 410 are the same, wherein the interval between adjacent through holes 410 refers to the distance between one side of a through hole 410 and one side of an adjacent through hole 410 along the width direction Z of the diaphragm 300 .

[0174] In this embodiment, the intervals between adjacent through holes 410 are the same, which is conducive to processing the through holes 410 on the diaphragm 300, so that the strength of the diaphragm 300 on the straight line where the multiple through holes 410 are located is the same, avoiding the situation where the local strength is weak and it is broken during the folding process.

[0175] In some embodiments, the through hole 410 is in a regular shape such as a circle, rectangle, ellipse, hexagon, or octagon. In addition to being in a regular shape, the through hole 410 can also be in an irregular shape.

[0176] In some embodiments, the first electrode sheet is a negative electrode sheet 100 or a positive electrode sheet 200 , and the second electrode sheet is a positive electrode sheet 200 or a negative electrode sheet 100 .

[0177] For example, referring to FIG1 , if the first electrode is a negative electrode 100 , the corresponding second electrode is a positive electrode 200 ; referring to FIG12 , if the first electrode is a positive electrode 200 , the corresponding second electrode is a negative electrode 100 .

[0178] In some embodiments, referring to Figures 1 and 12 , the length of the negative electrode sheet 100 is greater than the length of the positive electrode sheet 200, and the width of the negative electrode sheet 100 is greater than the width of the positive electrode sheet 200. In the thermal composite laminated battery cell 10, along the thickness direction of the negative electrode sheet 100, the projection of the positive electrode sheet 200 on the negative electrode sheet 100 completely falls within the negative electrode sheet 100.

[0179] It can be understood that, referring to Figures 1 and 9, if the first electrode is a negative electrode 100 and the second electrode is a positive electrode 200, the length dimension of the first electrode is greater than the length dimension of the second electrode, and the width dimension of the first electrode is greater than the width dimension of the second electrode; referring to Figures 11 and 12, if the first electrode is a positive electrode 200 and the second electrode is a negative electrode 100, the length dimension of the first electrode is less than the length dimension of the second electrode, and the width dimension of the first electrode is less than the width dimension of the second electrode. The size of the negative electrode 100 is designed to be larger than the size of the positive electrode 200. During the charging process of the lithium battery, the negative electrode 100 can fully receive the lithium ions of the positive electrode 200, reducing the probability of lithium dendrite formation, thereby reducing the occurrence of lithium dendrites piercing the diaphragm 300, resulting in a short circuit and thermal runaway, thereby improving the reliability of the battery.

[0180] In some embodiments, as shown in Figure 20, the long side dimension of the main body 340 is larger than the long side dimension of the negative electrode sheet 100, and the wide side dimension of the main body 340 is larger than the wide side dimension of the negative electrode sheet 100, that is, the projection of the negative electrode sheet 100 on the main body 340 completely falls within the continuous planar area enclosed by the outer contour of the main body 340.

[0181] The negative electrode sheet 100 and the positive electrode sheet 200 are separated by the main body 340. If the size of the main body 340 is smaller than the size of the negative electrode sheet 100, the negative electrode sheet 100 and the positive electrode sheet 200 may directly contact each other, causing a short circuit and thermal runaway. The size of the main body 340 is designed to be larger than the size of the positive electrode sheet 200 to meet the electrical safety requirements of the thermal composite laminated battery cell 10 and improve the reliability of the thermal composite laminated battery cell 10.

[0182] In some embodiments, referring to FIG7 , the thermal composite laminated battery cell 10 includes N first pole pieces and M second pole pieces, where N and M are both positive integers greater than 1. When the first pole piece is a negative pole piece 100 and the second pole piece is a positive pole piece 200 , NM=1.

[0183] It can be understood that the first electrode sheets and the second electrode sheets are arranged alternately, and the number of negative electrode sheets 100 is one more than the number of positive electrode sheets 200. The two outermost electrode sheets of the thermal composite laminated battery cell 10 are both negative electrode sheets 100, ensuring that the negative electrode sheets 100 can provide sufficient vacancies for the lithium ions released from the positive electrode sheets 200 to be embedded. Providing an excess of negative electrode sheets 100 reduces the probability of surface lithium dendrites in the battery and meets the electrical requirements of the battery.

[0184] Based on the above embodiment, as shown in Figure 4, the diaphragm 300 includes a starting end and an ending end, the first first pole piece is closer to the starting end of the diaphragm 300 than the first second pole piece, and the Nth first pole piece is closer to the ending end of the diaphragm 300 than the Mth second pole piece.

[0185] It can be understood that along the thickness direction of the first electrode sheet, N first electrode sheets and M second electrode sheets are alternately arranged, from the bottom of the thermal composite laminated battery cell 10 to the top of the thermal composite laminated battery cell 10, the N first electrode sheets are sequentially the 1st first electrode sheet to the Nth first electrode sheet, and the M second electrode sheets are sequentially the 1st second electrode sheet to the Mth second electrode sheet. The bottom and top of the thermal composite laminated battery cell 10 are the 1st first electrode sheet and the Nth first electrode sheet respectively. The diaphragm 300 wraps the side of the 1st first electrode sheet away from the 1st second electrode sheet, and the diaphragm 300 wraps the side of the Nth first electrode sheet away from the Mth second electrode sheet.

[0186] In some embodiments, as shown in Figures 18 and 19 , along the thickness direction X of the negative electrode sheets 100, the negative electrode sheets 100 and the positive electrode sheets 200 are alternately stacked, with each positive electrode sheet 200 positioned between two negative electrode sheets 100. Adjacent negative electrode sheets 100 and positive electrode sheets 200 are separated by a main body portion 340. The two outermost negative electrode sheets 100 are single-sided negative electrode sheets 100A, while the remaining negative electrode sheets 100 are single-sided negative electrode sheets 100B. The projections of the positive electrode sheets 200 and the negative electrode sheets 100 along the thickness direction of the negative electrode sheets 100 completely fall within the planar area of ​​the main body portion 340 between them. This allows the main body portion 340 to completely separate the negative electrode sheets 100 and the positive electrode sheets 200, preventing contact between the positive electrode sheets 200 and the negative electrode sheets 100 and causing a short circuit. The planar area of ​​the main body portion 340 is the continuous planar area enclosed by the outer contour of the main body portion 340 projected along the thickness direction of the negative electrode sheet 100.

[0187] It can be understood that before folding, the diaphragm 300 is in a continuous strip structure, and the negative electrode sheet 100 and the positive electrode sheet 200 are compounded on the main body 340 of the diaphragm 300 to form a thermal composite structure 20, and an incompletely cut structure 400 is provided on the diaphragm 300. The distance between the two sides of the incompletely cut structure 400 and the negative electrode sheet 100 on its side is the same or approximately the same, and the thermal composite structure 20 is folded along the straight line where the incompletely cut structure 400 is located. The folding position is fixed, which improves the alignment during the folding process, avoids the situation where lithium plating pierces the diaphragm 300 due to the misalignment of the negative electrode sheet 100 and the positive electrode sheet 200, and improves the electrical performance of the folded battery cell. The outermost negative electrode sheet 100 is set as a single-sided negative electrode sheet 100A, and the outermost side of the single-sided negative electrode sheet 100A does not need to be provided with an active material layer, thereby reducing material input and reducing costs.

[0188] In some embodiments, as shown in FIG. 4 , a single-sided negative electrode sheet 100B includes a negative electrode current collector 110 and a negative electrode active layer 120 . The negative electrode active layer 120 is disposed on both sides of the negative electrode current collector 110 .

[0189] In some embodiments, the single-sided negative electrode sheet 100A includes a negative current collector 110 and a negative active layer 120. The negative active layer 120 is disposed on one side of the negative current collector 110. For example, the negative current collector 110 may be made of copper, and the negative active layer 120 may be made of graphite.

[0190] In this embodiment, referring to FIG19 , along the thickness direction X of the negative electrode sheet 100 , from bottom to top, the N negative electrode sheets 100 are the first negative electrode sheet 100 , the second negative electrode sheet 100 …… the Nth negative electrode sheet 100 , the first negative electrode sheet 100 and the Nth negative electrode sheet 100 are located at the outermost sides of the thermal composite battery cell, the first negative electrode sheet 100 and the Nth negative electrode sheet 100 use a single-sided negative electrode sheet 100A, and the other negative electrode sheets 100 use a single-sided negative electrode sheet 100B, and the negative electrode active layer 120 is provided on one side of the negative electrode current collector 110 of the first negative electrode sheet 100 and the Nth negative electrode sheet 100 close to the main body 340 .

[0191] The outermost negative electrode sheet 100 of the thermal composite battery cell is set as a single-sided negative electrode sheet 100A, which reduces the use of negative electrode active materials and reduces processing costs. In addition, the outermost side of the single-sided negative electrode sheet 100A does not need to be covered with a separator 300, which reduces the separator 300 material and further reduces processing costs. Compared with related technologies, two layers of negative electrode active layers 120 and two layers of separators 300 are reduced, reducing the thickness of the thermal composite battery cell.

[0192] In some embodiments, as shown in FIG19 , the thickness of the negative electrode current collector 110 is D1, where 4.0 μm ≤ D1 ≤ 6.0 μm. The value of D1 can be 4.0 μm, 4.1 μm, 4.7 μm, 5.0 μm, 5.4 μm, 5.6 μm, 6.0 μm, or other unspecified values. The thickness of the negative electrode current collector 110 is designed to meet the electrical requirements of the negative electrode sheet 100.

[0193] In some embodiments, referring to FIG. 19 , the thickness of the negative electrode active layer 120 is D2, where 50 μm ≤ D2 ≤ μm. The value of D2 can be 50 μm, 65 μm, 72 μm, 89 μm, 95 μm, 108 μm, 117 μm, 122 μm, 136 μm, 144 μm, 159 μm, 162 μm, 175 μm, 187 μm, 198 μm, or other unspecified values. The thickness of the negative electrode active layer 120 is designed to meet the electrical requirements of the negative electrode sheet 100.

[0194] In some embodiments, the positive electrode sheet 200 includes a positive electrode current collector and a positive electrode active layer, with the positive electrode active layer disposed on both sides of the positive electrode current collector. For example, the positive electrode current collector may be made of aluminum foil, and the positive electrode active layer may be made of one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, or lithium iron phosphate.

[0195] In some embodiments, as shown in FIG10 , the thermal composite laminated battery cell 10 includes N first pole pieces and M second pole pieces, where N and M are both positive integers greater than 1. When the first pole piece is the positive pole piece 200 and the second pole piece is the negative pole piece 100 , MN=1.

[0196] It can be understood that the first electrode sheets and the second electrode sheets are arranged alternately, and the number of negative electrode sheets 100 is one more than the number of positive electrode sheets 200. The two outermost electrode sheets of the thermal composite laminated battery cell 10 are both negative electrode sheets 100, which meets the electrical requirements of the battery.

[0197] Referring to Figures 13, 14, 15, 16, and 17, this application also provides a thermal composite laminated battery cell 1010, which can be used as an energy storage unit in a battery. The battery can convert the energy stored in the battery cell into current and supply it to electronic devices. The thermal composite laminated battery cell 10 includes a continuous negative electrode sheet 100, multiple positive electrode sheets 200, and a separator 300.

[0198] In this embodiment, referring to Figures 13 and 15 , before folding, the negative electrode sheet 100 is in a continuous strip shape, and a plurality of negative electrode tabs are processed on the negative electrode sheet 100 . The positive electrode sheet 200 is cut from a positive electrode material roll, and the shape of the positive electrode sheet 200 is rectangular, and positive electrode tabs are processed on the positive electrode sheet 200 .

[0199] In this embodiment, referring to FIG13 and FIG15, the separator 300 includes a first separator 310 and a second separator 320. Before folding, the first separator 310 and the second separator 320 are continuous strip structures. The first separator 310 and the second separator 320 have the same size and shape. The shape of the negative electrode sheet 100 is the same as that of the first separator 310 and the second separator 320. The size of the first separator 310 and the second separator 320 is larger than that of the negative electrode sheet 100. The negative electrode sheet 100 is disposed between the first separator 310 and the second separator 320. The first separator 310 and the negative electrode sheet 100 are disposed between the first separator 310 and the second separator 320. The negative electrode sheet 100 is stacked with the first separator 310 and the second separator 320 to form a thermal composite structure 20. The thermal composite structure 20 is folded in a Z-shape to form multiple main bodies 340 and multiple bends 350. The bends 350 connect adjacent main bodies 340 and are provided with incompletely cut structures 400. Along the thickness direction X, the positive electrode sheets 200 and the main bodies 340 are alternately arranged. The positive electrode sheets 200 are arranged between adjacent main bodies 340, and the projection of the positive electrode sheets 200 in the thickness direction completely falls within the planar area of ​​the main body 340. The planar area of ​​the main body 340 is the continuous planar area enclosed by the outer contour of the main body 340 projected along the thickness direction of the positive electrode sheet 200. The separator 300 can be made of polypropylene, polyethylene, polyethylene terephthalate, polybutylene terephthalate, ethylene-propylene copolymer, cellulose, etc.

[0200] It can be understood that, referring to Figures 13 and 15, before the thermal composite structure 20 is folded, the first separator 310, the negative electrode sheet 100 and the second separator 320 are thermally composited to form a layered structure. The first separator 310 and the second separator 320 completely cover the negative electrode sheet 100 to ensure the electrical performance of the negative electrode sheet 100. Then, the positive electrode sheet 200 is alternately thermally composited on the first separator 310 and the second separator 320, and an incompletely cut structure 400 is processed on the thermal composite structure 20. The incompletely cut structure 400 is located at On one side of the positive electrode sheet 200, in this embodiment, there is no need to cut the negative electrode sheet 100, which reduces the processing steps of the thermal composite laminated battery cell 10 and improves the production efficiency of the thermal composite laminated battery cell 10. In addition, the thermal composite structure 20 is fixed at the position of each fold along the incompletely cut structure 400, which is conducive to the alignment of the thermal composite laminated battery cell 10, ensuring the electrical performance of the thermal composite laminated battery cell 10, and omitting subsequent alignment equipment, reducing equipment investment, reducing processing steps, and reducing the production cost of the thermal composite laminated battery cell 10.

[0201] The negative electrode sheet 100 and the positive electrode sheet 200 are composited on the separator 300, which means that the negative electrode sheet 100 and the positive electrode sheet 200 are fixed to the surface of the separator 300 through a thermal composite process. Exemplarily, the thermal composite process is as follows: the positive electrode material roll, the negative electrode material roll, and the separator 300 are fed simultaneously. Before entering the heating device, the positive electrode sheet 200 is cut into individual electrode sheets of the required size by a cutter. The combination of the negative electrode sheet 100, the positive electrode sheet 200, and the separator 300 enters the heating system under the action of rollers. The separator 300 is a glue-coated separator 300, which becomes sticky after being heated. After baking, the positive electrode sheet 200, the negative electrode sheet 100, and the separator 300 are thermally composited, and then rolled and cut to form a thermal composite structure 20.

[0202] In some embodiments, the negative electrode sheet 100 includes a continuous negative electrode current collector 110 and a continuous negative electrode active layer 120. The negative electrode active layer 120 is disposed on both sides of the negative electrode current collector 110. The side of the negative electrode active layer 120 facing away from the negative electrode current collector 110 is laminated to the separator 300 on that side. That is, the first separator 310 is laminated to the negative electrode active layer 120 on that side, and the second separator 320 is laminated to the negative electrode active layer 120 on that side. The negative electrode current collector 110 can be made of copper, and the negative electrode active layer 120 can be made of graphite.

[0203] In some embodiments, referring to Figures 15 and 16, the negative electrode sheet 100 includes a continuous negative electrode current collector 110 and multiple negative electrode active layers 120. The negative electrode current collector 110 is in a continuous strip shape. Multiple negative electrode active layers 120 are provided on both sides of the negative electrode current collector 110. The multiple negative electrode active layers 120 on one side of the negative electrode current collector 110 are arranged at intervals. The negative electrode active layer 120 is attached to the first separator 310 and the second separator 320 on its side. The projections of the negative electrode active layers 120 on both sides of the negative electrode current collector 110 on the negative electrode current collector 110 overlap, and the projections of the negative electrode active layers 120 along the thickness direction completely fall within the planar area of ​​the main body 340.

[0204] In this embodiment, the negative electrode sheet 100 can be laser etched to etch away the negative electrode active material in a local area to form a spaced negative electrode active layer 120, thereby preventing powder from falling off in the etched area during the folding of the composite laminate, reducing core package short circuits, and improving the performance of the thermal composite laminate battery cell 10.

[0205] Based on the above embodiment, referring to FIG17 , the two side surfaces of the negative electrode current collector 110 between adjacent negative electrode active layers 120 are respectively laminated to the first separator 310 and the second separator 320 on the side thereof. It will be appreciated that in this embodiment, the exposed negative electrode current collector 110 is laminated to the separator 300, and the separator 300 is firmly connected to the negative electrode sheet 100, reducing the probability of the separator 300 separating from the exposed negative electrode current collector 110 and improving the reliability of the battery cell.

[0206] In some embodiments, referring to FIG. 15 , in the thermal composite structure 20 , the distances between adjacent negative electrode active layers 120 are the same.

[0207] It can be understood that multiple negative electrode active layers 120 are formed by etching the negative electrode active material, and the distances between the negative electrode active layers 120 are set to be the same to facilitate processing. In addition, the area between adjacent negative electrode active layers 120 corresponds to the folded bending portion 350 to ensure the alignment of the thermal composite laminated battery cell 10.

[0208] In some embodiments, as shown in FIG15 , in the thermal composite structure 20 , the distance between adjacent negative electrode active layers 120 is L, where 1 mm ≤ L ≤ 3 mm. The value of L can be 1 mm, 1.3 mm, 1.8 mm, 2.5 mm, 2.7 mm, 3 mm, or other values ​​not listed.

[0209] In this embodiment, the distance between adjacent negative electrode active layers 120 is reasonably designed to avoid excessive negative electrode active material in the bending portion 350 area, which may cause powder loss during folding, and to avoid too little negative electrode active material in the main body 340 area, which may be unable to cover the positive electrode sheet 200, thereby ensuring the performance of the thermal composite laminated battery cell 10.

[0210] In some embodiments, as shown in FIG17 , the thickness of the negative electrode current collector 110 is D1, where 4 μm ≤ D1 ≤ 6 μm. The value of D1 can be 4 μm, 4.3 μm, 5 μm, 5.2 μm, 6 μm, or other unspecified values. The thickness of the negative electrode current collector 110 is designed to meet the electrical requirements of the negative electrode sheet 100.

[0211] In some embodiments, as shown in FIG. 17 , the thickness of the negative electrode active layer 120 is D2, where 50 μm ≤ D2 ≤ μm. The value of D2 can be 50 μm, 65 μm, 74 μm, 81 μm, 98 μm, 105 μm, 111 μm, 127 μm, 133 μm, 147 μm, 155 μm, 164 μm, 178 μm, 183 μm, 196 μm, μm, or other unspecified values. The thickness of the negative electrode active layer 120 is designed to meet the electrical requirements of the negative electrode sheet 100.

[0212] In some embodiments, as shown in FIG. 17 , the incompletely cut structure 400 includes a plurality of through holes 410 penetrating the separator 300 and the negative electrode sheet 100 . The plurality of through holes 410 are spaced apart along the width direction Z of the separator 300 .

[0213] It can be understood that in this embodiment, an incompletely cut structure 400 is formed by forming a through hole 410 on the composite laminate that passes through the first separator 310, the second separator 320 and the negative electrode sheet 100. The material at local positions on the first separator 310, the second separator 320 and the negative electrode sheet 100 is cut off. Along the width direction Z of the composite laminate, the first separator 310, the second separator 320 and the negative electrode sheet 100 are not completely cut. Compared with complete cutting, the separator 300 and the negative electrode sheet 100 will not be misaligned, and the separator 300 around the through hole 410 is weak. When the composite laminate is folded by free fall, the separator 300 and the negative electrode sheet 100 will fold along the position of the through hole 410, achieving precise position folding, which is beneficial to the alignment of the negative electrode sheet 100 and the positive electrode sheet 200 in the thermal composite laminate battery cell 10.

[0214] Alternatively, a plurality of through holes 410 are arranged in an array, and a plurality of columns of through holes 410 are arranged along the length direction Y of the diaphragm 300. Each column of through holes 410 can be arranged along the width direction Z of the diaphragm 300. Exemplarily, the arrangement directions of the plurality of columns of through holes 410 can be parallel to each other. In some other embodiments, there may be an angle between the arrangement direction of at least one column of through holes 410 and the arrangement direction of the through holes 410 in other columns. Exemplarily, the angle may be less than or equal to 10°, for example, 1°, 2°, 5°, etc. In some other embodiments, the angle may also be greater than 10°, and the embodiments of the present application are not limited to this. Exemplarily, the plurality of through holes 410 in one of any two columns of through holes 410 may be arranged one-to-one opposite to the plurality of through holes 410 in the other column. In some other embodiments, the plurality of through holes 410 in at least one column may be staggered with the plurality of through holes 410 in other columns. If the projections of two through holes 410 in the length direction Y of the diaphragm 300 do not overlap, the two through holes 410 can be considered to be staggered. For example, the through holes 410 in one of two adjacent rows of through holes 410 can be staggered with the through holes 410 in the other row.

[0215] In some other embodiments, the incompletely cut structure 400 may also include a plurality of slits spaced apart from each other. The slits may be formed by cutting the diaphragm 300 with a knife or the like. The incompletely cut structure 400 may also be a textured structure.

[0216] In other embodiments, the incompletely cut structure 400 includes a plurality of through holes 410 that only penetrate the diaphragm 300, and the plurality of through holes 410 are spaced apart along the width direction Z of the diaphragm 300. This can also release the folding stress at the bend 350, making it easier for the composite laminate to fold at the incompletely cut structure 400, thereby limiting the folding position and improving the folding quality and efficiency.

[0217] In some embodiments, referring to FIG. 15 , the length dimension of the negative electrode sheet 100 on the main body 340 is greater than the length dimension of the corresponding positive electrode sheet 200 , and the width dimension of the negative electrode sheet 100 on the main body 340 is greater than the width dimension of the corresponding positive electrode sheet 200 .

[0218] It is understood that along the thickness direction X of the thermal composite laminated battery cell 10, the projection of the positive electrode sheet 200 on the main body 340 completely falls within the negative electrode sheet 100. When the negative electrode sheet 100 includes multiple spaced negative electrode active layers 120, the projection of the positive electrode sheet 200 on the main body 340 completely falls within the negative electrode active layer 120. The size of the negative electrode sheet 100 is designed to be larger than that of the positive electrode sheet 200. During the charging process of the lithium battery, the negative electrode sheet 100 can fully receive the lithium ions of the positive electrode sheet 200, and lithium dendrites will not form. This prevents the formation of lithium dendrites that pierce the diaphragm 300, resulting in a short circuit and thermal runaway, thereby improving the reliability of the battery.

[0219] In some embodiments, as shown in FIG20 , the distance between the long side of the positive electrode sheet 200 and the long side of the corresponding negative electrode sheet 100 on the main body 340 is S2, where 1 mm ≤ S2 ≤ 3 mm, and / or the distance between the wide side of the positive electrode sheet 200 and the wide side of the negative active layer 120 of the corresponding negative electrode sheet 100 on the main body 340 is S3, where 1 mm ≤ S3 ≤ 3 mm. The values ​​of S2 and S3 can be 1 mm, 1.3 mm, 2 mm, 2.7 mm, 3 mm, or other values ​​not specified.

[0220] It can be understood that when the negative electrode sheet 100 includes a continuous negative electrode current collector 110 and multiple negative electrode active layers 120, the distance between the long side of the positive electrode sheet 200 and the long side of the corresponding negative electrode active layer 120 is S2, and the distance between the wide side of the positive electrode sheet 200 and the wide side of the corresponding negative electrode active layer 120 on the main body 340 is S3.

[0221] In this embodiment, the distance S2 between the long side of the positive electrode sheet 200 and the long side of the negative electrode sheet 100 and the distance S3 between the wide side of the positive electrode sheet 200 and the wide side of the negative electrode sheet 100 are reasonably designed to avoid material waste and increased cost due to excessive size while meeting the battery safety performance.

[0222] In some embodiments, referring to FIG. 13 and FIG. 15 , the length of the separator 300 is greater than the length of the negative electrode sheet 100 , and the width of the separator 300 is greater than the width of the negative electrode sheet 100 .

[0223] It is understood that the length of the separator 300 is greater than the length of the continuous negative electrode sheet 100, and the width of the separator 300 is greater than the width of the continuous negative electrode sheet 100. The negative electrode sheet 100 and the positive electrode sheet 200 are separated by the separator 300. If the separator 300 is smaller than the negative electrode sheet 100, the negative electrode sheet 100 and the positive electrode sheet 200 may directly contact each other, causing a short circuit and thermal runaway. The separator 300 is designed to be larger than the positive electrode sheet 200 to meet the electrical safety requirements of the thermal composite laminated battery cell 10 and improve the reliability of the thermal composite laminated battery cell 10.

Claims

1. A method for preparing a thermal composite laminated battery cell, comprising the following steps: Providing a negative electrode sheet (100), a positive electrode sheet (200), and a separator (300); The negative electrode sheet (100), the positive electrode sheet (200) and the separator (300) are thermally composited to form a thermal composite structure (20); Processing a plurality of incompletely cut structures (400) on the thermal composite structure (20), wherein adjacent incompletely cut structures (400) are spaced by i positive electrode sheets (200), where i is a positive integer; The thermal composite structure (20) is folded along a straight line where the incompletely cut structure (400) is located to prepare a thermal composite laminated battery core (10).

2. The method for preparing a thermal composite laminated battery cell according to claim 1, wherein: The thermal composite structure (20) is folded in a "Z" shape along the incompletely cut structure (400).

3. The method for preparing a thermal composite laminated battery cell according to claim 1, further comprising the following steps: if i is greater than 1, folding the thermal composite structure (20) along the straight line where the incompletely cut structure (400) is located to form a composite battery cell group (30); The composite battery cell group (30) is cut along the area between adjacent positive electrode sheets (200) to prepare i thermal composite laminated battery cells (10).

4. The method for preparing the thermal composite laminated battery core (10) according to claim 1, wherein: The thermal composite structure (20) comprises a plurality of negative electrode sheets (100), a plurality of positive electrode sheets (200) and a separator (300), wherein the negative electrode sheets (100) are arranged at intervals on one side of the separator (300), and the positive electrode sheets (200) are arranged at intervals on the other side of the separator (300), and along the length direction of the separator (300), i negative electrode sheets (100) and i positive electrode sheets (200) are arranged alternately, and the incompletely cut structure (400) is arranged on the separator (300) between adjacent negative electrode sheets (100) and positive electrode sheets (200).

5. The method for preparing a thermal composite laminated battery cell according to claim 1, wherein: The thermal composite structure (20) comprises N negative electrode sheet groups, M positive electrode sheet groups, a first separator (310) and a second separator (320), wherein the negative electrode sheet group comprises i negative electrode sheets (100), and the positive electrode sheet group comprises i positive electrode sheets (200), wherein N, M and i are positive integers, and NM=1.

6. The method for preparing the thermal composite laminated battery core (10) according to claim 5, wherein: The first separator (310) and the second separator (320) are bonded between adjacent negative electrode sheets (100).

7. The method for preparing a thermal composite laminated battery cell according to claim 5, wherein: The negative electrode sheet group is attached between the first separator (310) and the second separator (320); along the length direction of the thermal composite structure (20), the positive electrode sheet group is alternately attached to the side of the first separator (310) facing away from the negative electrode sheet group and the side of the second separator (320) facing away from the negative electrode sheet group; the projection of the positive electrode sheet (200) along the thickness direction completely falls within the plane area where the negative electrode sheet (100) is located; and the incompletely cut structure (400) is arranged on the first separator (310) and / or the second separator (320) between adjacent negative electrode sheet groups.

8. The method for preparing a thermal composite laminated battery cell according to claim 5, wherein: The positive electrode sheet group is attached between the first separator (310) and the second separator (320); along the length direction of the thermal composite structure (20), the negative electrode sheet group is alternately attached to the side of the first separator (310) facing away from the positive electrode sheet (200) and the side of the second separator (320) facing away from the positive electrode sheet (200); the projection of the positive electrode sheet (200) along the thickness direction completely falls within the plane area where the negative electrode sheet (100) is located; and the incompletely cut structure (400) is arranged on the first separator (310) and / or the second separator (320) between adjacent negative electrode sheet groups.

9. The method for preparing a thermal composite laminated battery cell according to claim 1, wherein: The thermal composite structure (20) comprises a continuous negative electrode sheet (100), a plurality of positive electrode sheet groups, a first separator (310) and a second separator (320); the positive electrode sheet group comprises i positive electrode sheets (200); the negative electrode sheet (100) is thermally composited between the first separator (310) and the second separator (320); along the length direction of the thermal composite structure (20), the positive electrode sheet group is alternately thermally composited on the side of the first separator (310) facing away from the negative electrode sheet (100) and the side of the second separator (320) facing away from the negative electrode sheet (100); the projection of the positive electrode sheet (200) in the thickness direction completely falls within the plane area where the negative electrode sheet (100) is located; and the incompletely cut structure (400) is arranged on the first separator (310) and / or the second separator (320) and / or the negative electrode sheet (100) between adjacent positive electrode sheet groups.

10. The method for preparing a thermal composite laminated battery cell according to claim 9, wherein: The negative electrode sheet (100) comprises a continuous negative electrode current collector (110) and a continuous negative electrode active layer (120), wherein the negative electrode active layer (120) is arranged on both sides of the negative electrode current collector (110), and the side of the negative electrode active layer (120) facing away from the negative electrode current collector (110) is in contact with the separator (300) on the side thereof.

11. The method for preparing a thermal composite laminated battery cell according to claim 9, wherein: The negative electrode sheet (100) comprises a continuous negative electrode current collector (110) and a plurality of negative electrode active layers (120), wherein the negative electrode active layers (120) are provided on both sides of the negative electrode current collector (110), and the negative electrode active layers (120) are arranged at intervals along the length direction of the negative electrode current collector (110), and the projection of the positive electrode sheet (200) along the thickness direction falls within the plane region where the negative electrode active layers (120) are located.

12. The method for preparing a thermal composite laminated battery cell according to claim 11, wherein: The two side surfaces of the negative electrode current collector (110) between adjacent negative electrode active layers (120) are bonded to the corresponding first separator (310) and the second separator (320).

13. The method for preparing a thermal composite laminated battery cell according to claim 11, wherein: The negative electrode active material on the negative electrode sheet (100) is etched away by laser to form a plurality of negative electrode active layers (120).

14. The method for preparing a thermal composite laminated battery cell according to claim 11, wherein: The distances between any adjacent negative electrode active layers (120) are the same.

15. The method for preparing a thermal composite laminated battery core according to any one of claims 10 to 14, wherein: The thickness of the negative electrode current collector (110) is D1, 4 μm≤D1≤6 μm.

16. The method for preparing a thermal composite laminated battery core according to any one of claims 10 to 14, wherein: The thickness of the negative electrode active layer (120) is D2, 50 μm≤D2≤200 μm.

17. The method for preparing a thermal composite laminated battery core according to any one of claims 10 to 14, wherein: The distance between adjacent negative electrode active layers (120) is 1 mm ≤ L ≤ 3 mm.

18. The method for preparing a thermal composite laminated battery cell according to claim 1, wherein: The thermal composite structure (20) includes n double-sided negative electrode sheet groups, M positive electrode sheet groups, a first separator (310) and a second separator (320), wherein the double-sided negative electrode sheet group includes i double-sided negative electrode sheets (100B), and the positive electrode sheet group includes i positive electrode sheets (200), n and m are positive integers, Mn=1, wherein the positive electrode sheet group is located between the first separator (310) and the second separator (320), and along the length direction of the thermal composite structure (20), the double-sided negative electrode sheet group and the positive electrode sheet group are spaced apart. The double-sided negative electrode sheet group is alternately arranged, and is thermally composited on the side of the first separator (310) facing away from the positive electrode sheet group and the side of the second separator (320) facing away from the positive electrode sheet group. The projection of the positive electrode sheet (200) in the thickness direction falls within the plane area where the double-sided negative electrode sheet (100B) is located. The incompletely cut structure (400) is arranged on the first separator (310) and / or the second separator (320) between adjacent double-sided negative electrode sheet groups.

19. The method for preparing a thermal composite laminated battery cell according to claim 18, wherein: The following steps are also included: Providing two single-sided electrode groups, each of which includes i single-sided negative electrode sheets (100A); After the thermal composite structure (20) is folded along the straight line where the incompletely cut structure (400) is located, the single-piece electrode groups are thermally composited on the outermost sides of the folded thermal composite structure (20) to prepare a thermal composite laminated battery core (10).

20. The method for preparing a thermal composite laminated battery core according to any one of claims 1 to 14, wherein: The incompletely cut structure (400) comprises a plurality of through holes (410), and the plurality of through holes (410) are arranged at intervals along the width direction of the thermal composite structure (20).

21. The method for preparing a thermal composite laminated battery cell according to claim 20, wherein: The intervals between adjacent through holes (410) are the same.

22. The method for preparing a thermal composite laminated battery core according to claim 20, wherein: Along the width direction of the thermal composite structure (20), the interval between adjacent through holes (410) is S1, wherein 5 mm ≤ S1 ≤ 20 mm.

23. The method for preparing the thermal composite laminated battery core (10) according to claim 20, wherein: The through hole (410) is in the shape of a circle, a rectangle, an ellipse, a hexagon or an octagon.

24. The method for preparing the thermal composite laminated battery core (10) according to claim 20, wherein: The through hole (410) has a first size L1 and a second size W1, wherein the first size is the distance between two parallel planes that virtually abut the hole walls on both sides of the through hole (410), and the second size is the distance between two parallel planes that virtually abut the hole walls at both ends of the through hole (410), wherein 1mm≤L1≤20mm, and / or 1mm≤W1≤2mm.

25. A thermal composite laminated battery core (10), comprising: a plurality of first pole pieces; a plurality of second pole pieces, wherein the polarities of the first pole piece and the second pole piece are opposite; as well as A diaphragm (300), the diaphragm (300) comprising a plurality of main body portions (340) and a plurality of bending portions (350) arranged alternately and continuously; In which, along the thickness direction of the first pole piece, the first pole piece and the second pole piece are alternately stacked, the adjacent first pole piece and the second pole piece are separated by the main body (340), the bending portion (350) is provided with an incompletely cut structure (400), and the diaphragm (300) is folded at the incompletely cut structure (400).

26. The thermal composite laminated battery core (10) according to claim 25, wherein: The first pole piece is provided with a first pole tab, the second pole piece is provided with a second pole tab, and at least a portion of the first pole tab and the second pole tab is located outside the diaphragm (300).

27. The thermal composite laminated battery core (10) according to claim 25 or 26, wherein: The first electrode sheet is a negative electrode sheet (100), the second electrode sheet is a positive electrode sheet (200), N first electrode sheets and M second electrode sheets are provided, N and M are both positive integers greater than 1, NM=1, the two outermost negative electrode sheets (100) are single-sided negative electrode sheets (100A), and the other negative electrode sheets (100) are double-sided negative electrode sheets (100B).

28. The thermal composite laminated battery core (10) according to claim 27, characterized in that: The single-sided negative electrode sheet (100A) comprises a negative electrode current collector (110) and a negative electrode active layer (120), wherein the negative electrode active layer (120) is provided on a side of the negative electrode current collector (110) close to the main body (340); The thickness of the negative electrode current collector (110) is D1, 4 μm≤D1≤6 μm; And / or, the thickness of the negative electrode active layer (120) is D2, 50 μm≤D2≤200 μm.

29. The thermal composite laminated battery core (10) according to any one of claims 25 to 28, wherein: The diaphragm (300) includes a first diaphragm (310) and a second diaphragm (320), wherein the first diaphragm (310) includes a first main body portion (341) and a first bent portion (351), and the second diaphragm (320) includes a second main body portion (342) and a second bent portion (352), and the first bent portion (351) and / or the second bent portion (352) are provided with the incompletely cut structure (400).

30. The thermal composite laminated battery core (10) according to claim 29, wherein: The first bending portion (351) and the second bending portion (352) are both provided with the incompletely cut structure (400), and the projection of the incompletely cut structure (400) on the first bending portion (351) on the second diaphragm (320) overlaps with the incompletely cut structure (400) on the second bending portion (352).

31. The thermal composite laminated battery core (10) according to claim 30, wherein: The first bending portion (351) and the second bending portion (352) are connected in a close-fitting manner.

32. The thermal composite laminated battery core (10) according to any one of claims 25 to 31, wherein: The incompletely cut structure (400) includes a plurality of through holes (410) penetrating the diaphragm (300), and the plurality of through holes (410) are arranged at intervals along the width direction of the diaphragm (300).

33. The thermal composite laminated battery core (10) according to claim 32, wherein: The intervals between any two adjacent through holes (410) are the same.

34. The thermal composite laminated battery core (10) according to claim 32 or 33, wherein: Along the width direction of the diaphragm (300), the interval between adjacent through holes (410) is S1, wherein 5 mm ≤ S1 ≤ 20 mm.

35. The thermal composite laminated battery core (10) according to any one of claims 32 to 34, wherein: The through hole (410) has a first size L1 and a second size W1, wherein the first size is the distance between two parallel planes that virtually abut the hole walls on both sides of the through hole (410), and the second size is the distance between two parallel planes that virtually abut the hole walls at both ends of the through hole (410), wherein 1mm≤L1≤20mm, and / or 1mm≤W1≤2mm.

36. The thermal composite laminated battery core (10) according to any one of claims 32 to 35, wherein: The through hole (410) is in the shape of a circle, a rectangle, an ellipse, a hexagon or an octagon.

37. The thermal composite laminated battery core (10) according to any one of claims 25 to 36, wherein: The first electrode sheet is a negative electrode sheet (100), the second electrode sheet is a positive electrode sheet (200), the long side dimension of the negative electrode sheet (100) is larger than the long side dimension of the positive electrode sheet (200), and the wide side dimension of the negative electrode sheet (100) is larger than the wide side dimension of the positive electrode sheet (200).

38. The thermal composite laminated battery core (10) according to claim 37, wherein: The distance between the long side of the positive electrode sheet (200) and the long side of the negative electrode sheet (100) is S2, wherein 1 mm ≤ S2 ≤ 3 mm; And / or, the distance between the wide side of the positive electrode sheet (200) and the wide side of the negative electrode sheet (100) is S3, wherein 1mm≤S3≤3mm.

39. The thermal composite laminated battery core (10) according to claim 37 or 38, wherein: The long side dimension of the main body (340) is greater than the long side dimension of the negative electrode sheet (100), and the wide side dimension of the main body (340) is greater than the wide side dimension of the negative electrode sheet (100).

40. The thermal composite laminated battery core (10) according to any one of claims 37 to 40, wherein: The distance between the long side of the negative electrode sheet (100) and the long side of the separator (300) is S4, wherein 2 mm ≤ S4 ≤ 4 mm; And / or, the separator (300) includes a starting end, and the distance between the starting end and the wide side of the negative electrode sheet (100) close to the starting end is S5, wherein 1mm≤S5≤3mm.

41. The thermal composite laminated battery core (10) according to claim 26, wherein: The diaphragm (300) includes a starting end and an ending end, the first first pole piece is closer to the starting end of the diaphragm (300) than the first second pole piece, and the Nth first pole piece is closer to the ending end of the diaphragm (300) than the Mth second pole piece.

42. The thermal composite laminated battery cell (10) according to claim 25 comprises N first pole pieces and M second pole pieces, N and M are both positive integers greater than 1, and when the first pole piece is a positive pole piece (200) and the second pole piece is a negative pole piece (100), MN=1.

43. The thermal composite laminated battery core (10) according to claim 42, characterized in that: The diaphragm (300) includes a starting end and an ending end, the first second pole piece is closer to the starting end of the diaphragm (300) than the first first pole piece, and the Mth second pole piece is closer to the ending end of the diaphragm (300) than the Nth first pole piece.

44. A thermal composite laminated battery core (10), comprising: A negative electrode sheet (100); a plurality of positive electrode sheets (200); The diaphragm (300) comprises a first diaphragm (310) and a second diaphragm (320); the negative electrode sheet (100) is attached between the first diaphragm (310) and the second diaphragm (320) to form a thermal composite structure; the thermal composite structure comprises a plurality of main bodies (340) and a plurality of bent parts (350) arranged alternately and continuously; the bent parts (350) are provided with an incompletely cut structure (400); along the thickness direction of the negative electrode sheet (100), the positive electrode sheet (200) is arranged between adjacent main bodies (340); and the projection of the positive electrode sheet (200) in the thickness direction completely falls within the plane area of ​​the main body (340).

45. The thermal composite laminated battery core (10) according to claim 44, wherein: The length of the negative electrode sheet (100) is at least greater than the length of the two positive electrode sheets (200).

46. ​​The thermal composite laminated battery core (10) according to claim 44 or 45, wherein: The negative electrode sheet (100) comprises a continuous negative electrode current collector (110) and a continuous negative electrode active layer (120), wherein the negative electrode active layer (120) is arranged on both sides of the negative electrode current collector (110), and the side of the negative electrode active layer (120) facing away from the negative electrode current collector (110) is in contact with the separator (300) on the side thereof.

47. The thermal composite laminated battery core (10) according to claim 45 or 46, wherein: The negative electrode sheet (100) comprises a continuous negative electrode current collector (110) and two layers of negative electrode active layers (120), the negative electrode active layers (120) are provided on both sides of the negative electrode current collector (110), and the projection of the negative electrode active layers (120) in the thickness direction completely falls within the plane area of ​​the main body (340).

48. The thermal composite laminated battery core (10) according to claim 47, wherein: The negative electrode current collector (110) between adjacent negative electrode active layers (120) is bonded to the first separator (310) and the second separator (320).

49. The thermal composite laminated battery core (10) according to claim 47 or 48, wherein: In the thermal composite structure, the distances between adjacent negative electrode active layers (120) are the same.

50. The thermal composite laminated battery core (10) according to any one of claims 47 to 59, wherein: In the thermal composite structure, the distance between adjacent negative electrode active layers (120) is L, wherein 1 mm ≤ L ≤ 3 mm.

51. The thermal composite laminated battery core (10) according to any one of claims 46 to 50, wherein: The thickness of the negative electrode current collector (110) is D1, 4 μm≤D1≤6 μm.

52. The thermal composite laminated battery core (10) according to any one of claims 46 to 51, wherein: The thickness of the negative electrode active layer (120) is D2, 50 μm≤D2≤200 μm.

53. The thermal composite laminated battery core (10) according to any one of claims 44 to 52, characterized in that: The incompletely cut structure (400) comprises a plurality of through holes (410) penetrating the diaphragm (300) and the negative electrode sheet (100), and the plurality of through holes (410) are arranged at intervals along the width direction of the diaphragm (300).

54. The thermal composite laminated battery core (10) according to claim 53, wherein: The intervals between any two adjacent through holes (410) are the same.

55. The thermal composite laminated battery core (10) according to claim 53 or 54, wherein: The through hole (410) is in the shape of a circle, a rectangle, an ellipse, a hexagon or an octagon.

56. The thermal composite laminated battery core (10) according to any one of claims 53 to 55, wherein: Along the width direction of the diaphragm (300), the interval between adjacent through holes (410) is S1, wherein 5 mm ≤ S1 ≤ 20 mm.

57. The thermal composite laminated battery core (10) according to any one of claims 53 to 56, wherein: The through hole (410) has a first size L1 and a second size W1, wherein the first size is the distance between two parallel planes that virtually abut the hole walls on both sides of the through hole (410), and the second size is the distance between two parallel planes that virtually abut the hole walls at both ends of the through hole (410), wherein 1mm≤L1≤20mm, and / or 1mm≤W1≤2mm.

58. The thermal composite laminated battery core (10) according to any one of claims 47 to 57, characterized in that: The length dimension of the negative electrode sheet (100) on the main body (340) is greater than the length dimension of the corresponding positive electrode sheet (200), and the width dimension of the negative electrode sheet (100) on the main body (340) is greater than the width dimension of the corresponding positive electrode sheet (200).

59. The thermal composite laminated battery core (10) according to claim 58, characterized in that: The distance between the long side of the positive electrode sheet (200) and the long side of the corresponding negative electrode sheet (100) on the main body (340) is S2, 1mm≤S2≤3mm; And / or, the distance between the wide side of the positive electrode sheet (200) and the wide side of the corresponding negative electrode active layer (120) on the main body (340) is S3, wherein 1mm≤S3≤3mm.

60. The thermal composite laminated battery core (10) according to any one of claims 1 to 59, characterized in that: The length dimension of the separator (300) is greater than the length dimension of the negative electrode sheet (100), and the width dimension of the separator (300) is greater than the width dimension of the negative electrode sheet (100).

61. The thermal composite laminated battery core (10) according to claim 60, characterized in that: The distance between the long side of the negative electrode sheet (100) and the long side of the separator (300) is S4, 2mm≤S4≤4mm; And / or, the distance between the starting and ending ends of the negative electrode sheet (100) and the starting and ending ends of the separator (300) is S5, wherein 1mm≤S5≤3mm.

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