Bare battery cell, method for manufacturing bare battery cell, and battery

Abstract

The application provides a bare battery cell, which comprises a plurality of pole pieces and a diaphragm, the plurality of pole pieces comprises a plurality of positive pole pieces and a plurality of negative pole pieces, the plurality of positive pole pieces is divided into a plurality of groups according to the length of the blank foil area of the positive pole pieces, the plurality of groups of positive pole pieces are sequentially stacked according to the length of the blank foil area of the positive pole pieces from short to long, and the blank foil areas of the plurality of groups of positive pole pieces are welded by stages after stacking to form positive tabs; and / or the plurality of negative pole pieces is divided into a plurality of groups according to the length of the blank foil area of the negative pole pieces, the plurality of groups of negative pole pieces are sequentially stacked according to the length of the blank foil area of the negative pole pieces from short to long, and the blank foil areas of the plurality of groups of negative pole pieces are welded by stages after stacking to form negative tabs. The blank foil area of the pole piece is set to different lengths, so that the pole piece can be welded by stages, the welding effect is improved, false welding is avoided, the number of stacked pole pieces is increased, and the capacity of the battery cell is improved. The application further provides a preparation method of the bare battery cell and a battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a bare cell, a method for preparing a bare cell, and a battery. Background Technology

[0002] High-energy-density batteries are one of the current development directions for lithium batteries. For laminated cells, the more layers, the higher the cell capacity. However, as the number of layers increases, the empty foil areas of the copper and / or aluminum foil also become thicker, making them prone to poor soldering during welding. Due to current welding technology limitations, the number of laminated cells is generally below 50 layers. How to improve the structure of the empty foil areas and welding methods, and increase the number of laminated layers, are important issues that need to be addressed to improve battery capacity. Summary of the Invention

[0003] The purpose of this invention is to provide a bare battery cell that, by setting the empty foil area of ​​the electrode sheet to different lengths, enables graded welding, improves the welding effect, avoids incomplete welding, increases the number of electrode sheet stacks, and improves the battery cell capacity.

[0004] This invention provides a bare battery cell, comprising multiple electrode plates and a separator. The multiple electrode plates include multiple positive electrode plates and multiple negative electrode plates, which are arranged alternately in sequence. Adjacent positive electrode plates and negative electrode plates are separated by the separator. Both the positive electrode plates and the negative electrode plates have empty foil areas. The empty foil areas of the multiple positive electrode plates are stacked and then welded to form a positive electrode tab. The empty foil areas of the multiple negative electrode plates are stacked and then welded to form a negative electrode tab.

[0005] The positive electrode sheets are divided into multiple groups according to the length of their empty foil areas. Each group contains at least one positive electrode sheet. The length of the empty foil areas on the positive electrode sheets in the same group is the same. The length of the empty foil areas of the positive electrode sheets in each group is different. The multiple groups of positive electrode sheets are stacked sequentially along the thickness direction of the positive electrode sheets in order of increasing length of their empty foil areas. The positive electrode tab is formed by stacking the empty foil areas of the multiple groups of positive electrode sheets and then welding them in stages.

[0006] And / or, the plurality of negative electrode sheets are divided into multiple groups according to the length of their empty foil areas, and the number of negative electrode sheets in each group is at least one. The length of the empty foil areas on the negative electrode sheets in the same group is the same, and the length of the empty foil areas of the negative electrode sheets in each group is different. The multiple groups of negative electrode sheets are stacked sequentially along the thickness direction of the negative electrode sheets in order of increasing length of their empty foil areas. The negative electrode tab is formed by stacking the empty foil areas of the multiple groups of negative electrode sheets through graded welding.

[0007] In one feasible embodiment, the number of positive electrode sheets in each group is multiple. In another feasible embodiment, the number of positive electrode sheets in each group does not exceed 50, or 10-50, or 15-40. This limitation further ensures that incomplete soldering occurs during the graded welding process. The length of the empty foil area on the multiple positive electrode sheets in the same group is the same. And / or, the number of negative electrode sheets in each group is multiple. In one feasible embodiment, the number of negative electrode sheets in each group does not exceed 50, or 10-50, or 15-40. This limitation further ensures that incomplete soldering occurs during the graded welding process. The length of the empty foil area on the multiple negative electrode sheets in the same group is the same.

[0008] In one feasible manner, when forming the positive electrode tab by graded welding, along the thickness direction of the positive electrode sheet, all empty foil areas on the positive electrode sheets in the previous group are fixed to the empty foil areas on the positive electrode sheets in the adjacent next group by welding; and / or, when forming the negative electrode tab by graded welding, along the thickness direction of the negative electrode sheet, all empty foil areas on the negative electrode sheets in the previous group are fixed to the empty foil areas on the negative electrode sheets in the adjacent next group by welding.

[0009] In one feasible manner, when forming the positive electrode tab by staged welding, the ratio of the number of positive electrode pieces participating in welding in the previous group to the number of positive electrode pieces participating in welding in the next adjacent group is (2:1) to (30:1); and / or, when forming the negative electrode tab by staged welding, the ratio of the number of negative electrode pieces participating in welding in the previous group to the number of negative electrode pieces participating in welding in the next adjacent group is (2:1) to (30:1).

[0010] In one possible implementation, the ratio of the length of the empty foil region of the previous set of positive electrode sheets to the length of the empty foil region of the adjacent next set of positive electrode sheets is 1:(1.2-4); and / or, the ratio of the length of the empty foil region of the previous set of negative electrode sheets to the length of the empty foil region of the adjacent next set of negative electrode sheets is 1:(1.2-4).

[0011] In one possible implementation, the length difference between the empty foil area of ​​the previous set of positive electrode sheets and the empty foil area of ​​the adjacent next set of positive electrode sheets is 1.5 mm to 5 mm; and / or, the length difference between the empty foil area of ​​the previous set of negative electrode sheets and the empty foil area of ​​the adjacent next set of negative electrode sheets is 1.5 mm to 5 mm.

[0012] In one feasible embodiment, the bare cell further includes a positive conductive handle and a negative conductive handle, wherein the positive conductive handle is fixed to the positive electrode tab by welding, and the negative conductive handle is fixed to the negative electrode tab by welding. The welding position of the conductive handles is not particularly limited; the positive / negative conductive handles can be welded to the last set of positive / negative electrode sheets, located on the side of the last set of positive / negative electrode sheets closer to the first set, or located on the side of the last set of positive / negative electrode sheets farther from the first set. The positive / negative conductive handles can also be inserted between any empty foil areas of the positive / negative electrode sheets during the graded welding process, and welded to the empty foil areas of adjacent positive / negative electrode sheets.

[0013] In one possible implementation, the positive tab and the negative tab are located on the same side or different sides of the bare battery cell.

[0014] This invention also provides a method for preparing a bare battery cell, applicable to the bare battery cell described above, wherein the method for preparing the bare battery cell includes:

[0015] S10: Provides an electrode and a separator, wherein the electrode includes a plurality of positive electrode plates and a plurality of negative electrode plates;

[0016] S20: The plurality of positive electrode sheets, the plurality of negative electrode sheets, and the separator are stacked in the order of "positive electrode sheet-separator-negative electrode sheet" or "negative electrode sheet-separator-positive electrode sheet". The empty foil areas of the plurality of positive electrode sheets are stacked and then welded to form a positive electrode tab. The empty foil areas of the plurality of negative electrode sheets are stacked and then welded to form a negative electrode tab. At least one of the positive electrode tab and the negative electrode tab is formed by graded welding.

[0017] In one feasible manner, the positive electrode tab is formed by hierarchical welding of the empty foil regions of the plurality of positive electrode sheets, and the step of forming the positive electrode tab by hierarchical welding of the empty foil regions of the plurality of positive electrode sheets includes:

[0018] The positive electrode plates are divided into multiple groups according to the length of their empty foil regions. The length of the empty foil regions of the positive electrode plates in the multiple groups increases sequentially, and the number of positive electrode plates in each group is multiple.

[0019] The positive electrode tab is formed by stacking the empty foil areas of multiple sets of positive electrode sheets and then welding them in stages; wherein, when forming the positive electrode tab by stage welding, along the thickness direction of the positive electrode sheet, all the empty foil areas on the positive electrode sheets in the previous set are fixed to the empty foil areas on some of the positive electrode sheets in the next adjacent set by welding.

[0020] In one possible implementation, the bare cell further includes a positive conductive stem, and the method for fabricating the bare cell further includes:

[0021] When welding the empty foil area of ​​the last group of positive electrode sheets, the positive electrode conductive handle is fixed to the empty foil area on the last group of positive electrode sheets by welding; or, during the graded welding process, the positive electrode conductive handle is inserted between the empty foil areas of any of the positive electrode sheets and fixed to the empty foil areas of the adjacent positive electrode sheets by welding.

[0022] In one feasible manner, the negative electrode tab is formed by graded welding of the empty foil regions of a plurality of negative electrode sheets, and the step of forming the negative electrode tab by graded welding of the empty foil regions of the plurality of negative electrode sheets includes:

[0023] The multiple negative electrode sheets are divided into multiple groups according to the length of their empty foil areas. The length of the empty foil areas of the multiple groups of negative electrode sheets increases sequentially, and the number of negative electrode sheets in each group is multiple.

[0024] The negative electrode tab is formed by stacking the empty foil areas of multiple sets of negative electrode sheets and then welding them in stages; wherein, when forming the negative electrode tab by stage welding, along the thickness direction of the negative electrode sheet, all the empty foil areas on the negative electrode sheets in the previous set are fixed to the empty foil areas on some of the negative electrode sheets in the next adjacent set by welding.

[0025] In one possible implementation, the bare cell further includes a negative conductive stem, and the method for fabricating the bare cell further includes:

[0026] When welding the empty foil area of ​​the last set of negative electrode sheets, the negative electrode conductive handle is fixed to the empty foil area on the last set of negative electrode sheets by welding; or, during the graded welding process, the negative electrode conductive handle is inserted between the empty foil areas of any negative electrode sheet and fixed to the empty foil area of ​​the adjacent negative electrode sheet by welding.

[0027] The present invention also provides a battery comprising the bare cells described above.

[0028] The bare battery cell provided by this invention divides the positive and / or negative electrode sheets into multiple groups according to the different lengths of their empty foil areas. Multiple groups of positive electrode sheets are sequentially stacked in order of increasing empty foil area length and then welded in stages to form positive electrode tabs. Similarly, multiple groups of negative electrode sheets are sequentially stacked in order of increasing empty foil area length and then welded in stages to form negative electrode tabs. During staged welding, the longer empty foil areas are used for transfer, thereby achieving multiple welding operations. This invention, by setting the empty foil areas of the electrode sheets to different lengths, enables multiple staged welding operations, improves welding efficiency, avoids incomplete soldering, increases the number of electrode layers, and improves the cell's capacity. Attached Figure Description

[0029] Figure 1 This is a top view of a bare battery cell in an embodiment of the present invention.

[0030] Figure 2 for Figure 1 Side view.

[0031] Figure 3 This is a schematic diagram of the structure of the positive electrode, negative electrode and separator in an embodiment of the present invention.

[0032] Figure 4 This is a top view of a bare battery cell in another embodiment of the present invention.

[0033] Figure 5 This is a top view of a bare battery cell in another embodiment of the present invention. Detailed Implementation

[0034] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0035] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification and claims of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0036] The directional terms such as "up," "down," "left," "right," "front," "back," "top," and "bottom" (if present) used in the specification and claims of this invention are defined by the position of the structures in the drawings and their relative positions to each other, and are only for the clarity and convenience of expressing the technical solution. It should be understood that the use of these directional terms should not limit the scope of protection claimed in this application.

[0037] like Figures 1 to 3As shown, the bare battery cell 1 provided in this embodiment of the invention includes multiple electrode sheets and multiple separators 13. The multiple electrode sheets include multiple positive electrode sheets 11 and multiple negative electrode sheets 12, which are arranged alternately in sequence. Adjacent positive electrode sheets 11 and negative electrode sheets 12 are separated by separators 13. Both the positive electrode sheet 11 and the negative electrode sheet 12 have empty foil areas 111 / 121 and coated areas 112 / 122, with the empty foil areas 111 / 121 located on one side of the coated areas 112 / 122. The coated areas 112 / 122 are coated with active material, while the empty foil areas 111 / 121 are not coated with active material. The empty foil areas 111 on the positive electrode sheet 11 and 121 on the negative electrode sheet 12 are both cut to form tabs. The bare cell 1 is formed by stacking and welding multiple positive electrode plates 11, multiple negative electrode plates 12, and a separator 13. The coating areas 112 of the multiple positive electrode plates 11, the coating areas 122 of the multiple negative electrode plates 12, and the separator 13 are stacked to form the main body 101 of the bare cell 1. The empty foil areas 111 of the multiple positive electrode plates 11 are stacked and welded to form the positive electrode tab 102 of the bare cell 1, and the empty foil areas 121 of the multiple negative electrode plates 12 are stacked and welded to form the negative electrode tab 103 of the bare cell 1.

[0038] like Figures 1 to 3 As shown, in one embodiment, multiple positive electrode plates 11 are divided into multiple groups according to the length of their empty foil areas 111. The number of positive electrode plates 11 in each group is at least one. The length of the empty foil areas 111 on the positive electrode plates 11 in the same group is the same. The length of the empty foil areas 111 in each group of positive electrode plates 11 is different. Multiple groups of positive electrode plates 11 are stacked sequentially along the thickness direction of the positive electrode plates 11 in order of increasing length of their empty foil areas 111 (i.e., stacked along the thickness direction of the bare cell 1). After stacking, the empty foil areas 111 of multiple groups of positive electrode plates 11 are formed into the positive electrode tab 102 of the bare cell 1 by graded welding (in the graded welding, only the empty foil areas 111 of two adjacent groups of positive electrode plates 11 are welded in each stage, and then the longer empty foil area 111 is used for the transition to the next stage of welding).

[0039] Multiple negative electrode sheets 12 are divided into multiple groups according to the length of their empty foil areas 121. Each group contains at least one negative electrode sheet 12. The length of the empty foil areas 121 on the negative electrode sheets 12 in the same group is the same. The length of the empty foil areas 121 of each group of negative electrode sheets 12 is different. Multiple groups of negative electrode sheets 12 are stacked sequentially along the thickness direction of the negative electrode sheets 12 in order of increasing length of their empty foil areas 121 (i.e., stacked along the thickness direction of the bare cell 1). After stacking, the empty foil areas 121 of multiple groups of negative electrode sheets 12 are formed into the negative electrode tabs 103 of the bare cell 1 through graded welding (in the graded welding, only the empty foil areas 121 of two adjacent groups of negative electrode sheets 12 are welded at each stage, and then the longer empty foil areas 121 are used for the transition to the next stage of welding).

[0040] For example, multiple positive electrode plates 11 are divided into N groups according to the length of their empty foil regions 111, that is, the multiple groups of positive electrode plates 11 are the first group of positive electrode plates 11 to the Nth group of positive electrode plates 11; multiple negative electrode plates 12 are divided into N groups according to the length of their empty foil regions 121, that is, the multiple groups of negative electrode plates 12 are the first group of negative electrode plates 12 to the Nth group of negative electrode plates 12; where N is a positive integer greater than or equal to 2.

[0041] The aforementioned graded welding specifically includes: when forming the positive electrode tab 102 through graded welding, firstly, the empty foil area 111 on the Mth group of positive electrode plates 11 is fixed to a portion of the empty foil area 111 on the (M+1)th group of positive electrode plates 11 by welding, then the empty foil area 111 on the (M+1)th group of positive electrode plates 11 is transferred through welding, and the empty foil area 111 on the (M+1)th group of positive electrode plates 11 is fixed to a portion of the empty foil area 111 on the (M+2)th group of positive electrode plates 11 by welding, and so on, until the empty foil area 111 on the (N-1)th group of positive electrode plates 11 is fixed to all the empty foil areas 111 on the Nth group of positive electrode plates 11 by welding. When forming the negative electrode tab 103 through graded welding, the empty foil area 121 on the Mth group of negative electrode sheets 12 is first fixed to a portion of the empty foil area 121 on the (M+1)th group of negative electrode sheets 12 by welding. Then, the empty foil area 121 on the already welded (M+1)th group of negative electrode sheets 12 is transferred to a portion of the empty foil area 121 on the (M+2)th group of negative electrode sheets 12 by welding, and so on, until the empty foil area 121 on the (N-1)th group of negative electrode sheets 12 is fixed to all the empty foil areas 121 on the Nth group of negative electrode sheets 12 by welding. Here, M is a positive integer greater than or equal to 1 and less than N.

[0042] It should be noted that in practical applications, one of the positive electrode tab 102 and the negative electrode tab 103 can be formed by graded welding, while the other can be formed by conventional welding (e.g., by a single welding process). For example, if the positive electrode tab 102 is formed by graded welding and the negative electrode tab 103 is formed by conventional welding, then multiple positive electrode sheets 11 are grouped as described above and then formed by graded welding to form the positive electrode tab 102; while the empty foil areas 121 of multiple negative electrode sheets 12 are of the same length, and the empty foil areas 121 of multiple negative electrode sheets 12 are stacked and then welded by conventional welding (e.g., a single welding process) to form the negative electrode tab 103. Conversely, the negative electrode tab 103 can also be formed by graded welding, while the positive electrode tab 102 can be formed by conventional welding. Preferably, both the positive electrode tab 102 and the negative electrode tab 103 are formed by graded welding.

[0043] The bare cell 1 provided in this embodiment divides the positive electrode 11 and negative electrode 12 into multiple groups according to the different lengths of the empty foil areas 111 / 121. Multiple groups of positive electrode 11 are stacked sequentially in ascending order of the length of their empty foil areas 111 and formed into a positive electrode tab 102 through graded welding. Similarly, multiple groups of negative electrode 12 are stacked sequentially in ascending order of the length of their empty foil areas 121 and formed into a negative electrode tab 103 through graded welding. During graded welding, the longer empty foil areas are used for transfer, thus achieving multiple welding operations. This embodiment sets the empty foil areas of the electrode 11 to different lengths, enabling multiple graded welding operations. Each welding operation involves a relatively small number of electrode 11s, and the thickness of the stacked empty foil areas is also relatively thin (i.e., dividing a single welding operation into multiple welding operations with fewer electrode 11s per operation), thereby avoiding incomplete welds, improving welding efficiency, increasing the number of electrode stack layers, and increasing the cell capacity. Meanwhile, graded welding can solve the problem of difficulty in gathering the empty foil area of ​​traditional laminated cells, reducing the probability of the outermost empty foil area being torn off.

[0044] like Figure 1 and Figure 2 As shown, in one embodiment, the bare battery cell 1 also includes a positive conductive handle 14 and a negative conductive handle 15. The positive conductive handle 14 is fixed to the positive electrode tab 102 by welding, and the negative conductive handle 15 is fixed to the negative electrode tab 103 by welding.

[0045] like Figure 2 As shown, in one embodiment, the positive electrode conductive handle 14 is fixed to the empty foil area 111 on the last group of positive electrode plates 11 (i.e., the Nth group of positive electrode plates 11) by welding, and the negative electrode conductive handle 15 is fixed to the empty foil area 121 on the last group of negative electrode plates 12 (i.e., the Nth group of negative electrode plates 12) by welding.

[0046] like Figure 2 As shown, in one embodiment, the positive electrode conductive handle 14 is located on the side of the last group of positive electrode plates 11 that is close to the first group of positive electrode plates 11, and the negative electrode conductive handle 15 is located on the side of the last group of negative electrode plates 12 that is close to the first group of negative electrode plates 12.

[0047] like Figure 1 and Figure 2 As shown, in one embodiment, both the positive electrode conductive handle 14 and the negative electrode conductive handle 15 are provided with tab adhesive 16.

[0048] like Figure 2 As shown, in one embodiment, there are multiple positive electrode plates 11 in each group, and the length of the open foil region 111 on the multiple positive electrode plates 11 in the same group is the same. There are multiple negative electrode plates 12 in each group, and the length of the open foil region 121 on the multiple negative electrode plates 12 in the same group is the same.

[0049] like Figure 1 andFigure 2 As shown, in one embodiment, when forming the positive electrode tab 102 by graded welding, along the thickness direction of the positive electrode sheet 11, all the empty foil areas 111 on the positive electrode sheets 11 in the previous group are fixed to the empty foil areas 111 on the positive electrode sheets 11 in the adjacent next group by welding; when forming the negative electrode tab 103 by graded welding, along the thickness direction of the negative electrode sheet 12, all the empty foil areas 121 on the negative electrode sheets 12 in the previous group are fixed to the empty foil areas 121 on the negative electrode sheets 12 in the adjacent next group by welding.

[0050] like Figure 1 and Figure 2 As shown, in one embodiment, multiple positive electrode plates 11 are divided into three groups according to the length of their empty foil regions 111. The length of the empty foil regions 111 in the three groups of positive electrode plates 11 increases sequentially. The first group of positive electrode plates 11 includes multiple first positive electrode plates 11A, the second group of positive electrode plates 11 includes multiple second positive electrode plates 11B, and the third group of positive electrode plates 11 includes multiple third positive electrode plates 11C. Multiple negative electrode plates 12 are divided into three groups according to the length of their empty foil regions 121. The length of the empty foil regions 121 in the three groups of negative electrode plates 12 increases sequentially. The first group of negative electrode plates 12 includes multiple first negative electrode plates 12A, the second group of negative electrode plates 12 includes multiple second negative electrode plates 12B, and the third group of negative electrode plates 12 includes multiple third negative electrode plates 12C.

[0051] When forming the positive electrode tab 102 through graded welding, all the empty foil areas 111 on the first positive electrode 11A in the first group and some of the empty foil areas 111 on the second positive electrode 11B in the second group are welded to form a first-level weld (H1 in the figure represents the location of the first-level weld). All the empty foil areas 111 on the second positive electrode 11B (including some of the second positive electrode 11B that participate in the first-level weld) in the second group and some of the empty foil areas 111 on the third positive electrode 11C in the third group are welded to form a second-level weld (H2 in the figure represents the location of the second-level weld). All the empty foil areas 111 on the third positive electrode 11C (including some of the third positive electrode 11C that participate in the second-level weld) in the third group and the positive electrode conductive handle 14 are welded to form a third-level weld (H3 in the figure represents the location of the third-level weld).

[0052] When forming the negative electrode tab 103 through graded welding, all the empty foil areas 121 on the first negative electrode sheet 12A in the first group and some of the empty foil areas 121 on the second negative electrode sheet 12B in the second group are welded to form a first-level weld (H1 in the figure represents the location of the first-level weld). All the empty foil areas 121 on the second negative electrode sheet 12B (including some of the second negative electrode sheet 12B involved in the first-level weld) in the second group and some of the empty foil areas 121 on the third negative electrode sheet 12C in the third group are welded to form a second-level weld (H2 in the figure represents the location of the second-level weld). All the empty foil areas 121 on the third negative electrode sheet 12C (including some of the third negative electrode sheet 12C involved in the second-level weld) in the third group and the negative electrode conductive handle 15 are welded to form a third-level weld (H3 in the figure represents the location of the third-level weld).

[0053] In one implementation, when forming the positive electrode tab 102 by graded welding, the ratio of the number of positive electrode pieces 11 participating in welding in the previous group to the number of positive electrode pieces 11 participating in welding in the next adjacent group is (2:1) to (30:1), or (3:1) to (20:1), or (5:1) to (10:1); for example, the ratio of the number of the first positive electrode piece 11A and the second positive electrode piece 11B participating in welding is (2:1) to (30:1).

[0054] When forming the negative electrode tab 103 by graded welding, the ratio of the number of negative electrode pieces 12 participating in welding in the previous group to the number of negative electrode pieces 12 participating in welding in the adjacent next group is (2:1) to (30:1), or (3:1) to (20:1), or (5:1) to (10:1); for example, the ratio of the number of the first negative electrode piece 12A and the second negative electrode piece 12B participating in welding is (2:1) to (30:1).

[0055] In one implementation, the number of the last group of positive electrode plates 11 (i.e., the Nth group of positive electrode plates 11) is 10 to 50, or 15 to 40. The number of the last group of negative electrode plates 12 (i.e., the Nth group of negative electrode plates 12) is 10 to 50, or 15 to 40.

[0056] In one embodiment, the number of positive electrode plates 11 in each group does not exceed 50, or 10 to 50, or 15 to 40. In another embodiment, the number of negative electrode plates 12 in each group does not exceed 50, or 10 to 50, or 15 to 40.

[0057] In one implementation, the ratio of the length of the empty foil region 111 of the previous set of positive electrode plates 11 to the length of the empty foil region 111 of the adjacent next set of positive electrode plates 11 is 1:(1.2-4) or 1:(1.5-4). For example, the length of the empty foil region 111 of the first positive electrode plate 11A : the length of the empty foil region 111 of the second positive electrode plate 11B = 1:(1.2-4) or 1:(1.5-4).

[0058] In one implementation, the length difference between the empty foil region 111 of the previous positive electrode 11 and the empty foil region 111 of the adjacent next positive electrode 11 is 1.5mm to 5mm, or 2.5mm to 4mm, or 3mm to 4mm; for example, the length difference between the empty foil region 111 of the first positive electrode 11A and the empty foil region 111 of the second positive electrode 11B is 1.5mm to 5mm.

[0059] In one implementation, the length of the empty foil region 121 of the previous negative electrode 12 is 1:(1.2-4) to the length of the empty foil region 121 of the adjacent next negative electrode 12. For example, the length of the empty foil region 121 of the first negative electrode 12A is 1:(1.2-4) to the length of the empty foil region 121 of the second negative electrode 12B.

[0060] In one implementation, the length difference between the empty foil area 121 of the previous negative electrode 12 and the empty foil area 121 of the adjacent next negative electrode 12 is 1.5mm to 5mm, or 2.5mm to 4mm, or 3mm to 4mm; for example, the length difference between the empty foil area 121 of the first negative electrode 12A and the empty foil area 121 of the second negative electrode 12B is 1.5mm to 5mm.

[0061] like Figure 1 As shown, in one embodiment, the positive tab 102 and the negative tab 103 are located on the same side of the bare cell 1.

[0062] like Figure 1 As shown, in one embodiment, the positive tab 102 and the negative tab 103 are both located on the same side of the bare cell 1 along its length L. Figure 4 As shown, in another embodiment, the positive tab 102 and the negative tab 103 are both located on the same side of the bare cell 1 along the width direction W of the bare cell 1.

[0063] like Figure 5 As shown, in one embodiment, the positive tab 102 and the negative tab 103 are located on different sides of the bare cell 1, and the positive tab 102 and the negative tab 103 are respectively located on opposite sides of the bare cell 1 along the length direction L of the bare cell 1.

[0064] In one implementation, the bare cell 1 can be stacked in the order of "positive electrode 11-separator 13-negative electrode 12" or "negative electrode 12-separator 13-positive electrode 11" during the stacking process, and the positive electrode 11 and the negative electrode 12 are stacked in the order of shortest to longest length of the empty foil area 111 / 121 during the stacking process.

[0065] In one implementation, the bare battery cell 1 can be encapsulated using an aluminum-plastic film or a metal casing.

[0066] This invention also provides a method for preparing a bare battery cell, applied to the bare battery cell 1 described above, the method comprising:

[0067] S10: Provides an electrode and a separator 13, the electrode including a plurality of positive electrode 11 and a plurality of negative electrode 12;

[0068] S20: Multiple positive electrode plates 11, multiple negative electrode plates 12, and separator 13 are stacked in the order of "positive electrode plate 11-separator 13-negative electrode plate 12" or "negative electrode plate 12-separator 13-positive electrode plate 11". The empty foil areas 111 of the multiple positive electrode plates 11 are stacked and then welded to form a positive electrode tab 102. The empty foil areas 121 of the multiple negative electrode plates 12 are stacked and then welded to form a negative electrode tab 103. At least one of the positive electrode tab 102 and the negative electrode tab 103 is formed by graded welding.

[0069] In one embodiment, the positive electrode tab 102 is formed by hierarchical welding of the empty foil regions 111 of multiple positive electrode plates 11. The step of forming the positive electrode tab 102 by hierarchical welding of the empty foil regions 111 of multiple positive electrode plates 11 includes:

[0070] Multiple positive electrode plates 11 are divided into multiple groups according to the length of their empty foil regions 111. The length of the empty foil regions 111 of the multiple groups of positive electrode plates 11 increases sequentially, and the number of positive electrode plates 11 in each group is multiple.

[0071] The empty foil areas 111 of multiple sets of positive electrode sheets 11 are stacked and then formed into positive electrode tabs 102 by graded welding; wherein, when forming positive electrode tabs 102 by graded welding, along the thickness direction of the positive electrode sheet 11, all the empty foil areas 111 on the positive electrode sheets 11 in the previous set are fixed to the empty foil areas 111 on some of the positive electrode sheets 11 in the next adjacent set by welding.

[0072] In one embodiment, the bare cell 1 further includes a positive electrode conductive stem 14, and the method for preparing the bare cell further includes:

[0073] When welding the empty foil area 111 of the last set of positive electrode plates 11, the positive electrode conductive handle 14 is fixed to the empty foil area 111 on the last set of positive electrode plates 11 by welding.

[0074] In one embodiment, the negative electrode tab 103 is formed by graded welding of the empty foil areas 121 of a plurality of negative electrode sheets 12. The step of forming the negative electrode tab 103 by graded welding of the empty foil areas 121 of the plurality of negative electrode sheets 12 includes:

[0075] Multiple negative electrode plates 12 are divided into multiple groups according to the length of their empty foil regions 121. The length of the empty foil regions 121 of the multiple groups of negative electrode plates 12 increases sequentially, and the number of negative electrode plates 12 in each group is multiple.

[0076] The empty foil areas 121 of multiple sets of negative electrode sheets 12 are stacked and then formed into negative electrode tabs 103 by graded welding; wherein, when forming negative electrode tabs 103 by graded welding, along the thickness direction of the negative electrode sheet 12, all the empty foil areas 121 on the negative electrode sheets 12 in the previous set are fixed to the empty foil areas 121 on the negative electrode sheets 12 in the adjacent next set by welding.

[0077] In one embodiment, the bare cell 1 further includes a negative electrode conductive stem 15, and the method for preparing the bare cell further includes:

[0078] When welding the empty foil area 121 of the last set of negative electrode sheets 12, the negative electrode conductive handle 15 is fixed to the empty foil area 121 on the last set of negative electrode sheets 12 by welding.

[0079] In one implementation, both the positive electrode tab 102 and the negative electrode tab 103 are formed by staged welding, and the above-mentioned step S20 specifically includes:

[0080] Multiple positive electrode plates 11 are divided into multiple groups according to the length of their empty foil regions 111, and the length of the empty foil regions 111 of the multiple groups of positive electrode plates 11 increases sequentially; multiple negative electrode plates 12 are divided into multiple groups according to the length of their empty foil regions 121, and the length of the empty foil regions 121 of the multiple groups of negative electrode plates 12 increases sequentially.

[0081] Multiple sets of positive electrode plates 11, multiple sets of negative electrode plates 12, and separators 13 are stacked in the order of "positive electrode plate 11-separator 13-negative electrode plate 12" or "negative electrode plate 12-separator 13-positive electrode plate 11" to obtain multiple stacked groups (that is, positive electrode plates 11 and negative electrode plates 12 of the same group are stacked together, for example, the first set of positive electrode plates 11 and the first set of negative electrode plates 12 are stacked together to obtain the first stacked group... and the Nth set of positive electrode plates 11 and the Nth set of negative electrode plates 12 are stacked together to obtain the Nth stacked group); the multiple stacked groups are the first stacked group to the Nth stacked group, where N is a positive integer greater than or equal to 2; the number of positive electrode plates 11 in each stacked group is multiple, and the number of negative electrode plates 12 in each stacked group is multiple;

[0082] Perform first-stage welding: fix all the empty foil areas 111 on the positive electrode 11 in the first lamination group to the empty foil areas 111 on the positive electrode 11 in the second lamination group by welding; fix all the empty foil areas 121 on the negative electrode 12 in the first lamination group to the empty foil areas 121 on the negative electrode 12 in the second lamination group by welding.

[0083] Perform secondary welding: fix all the empty foil areas 111 on the positive electrode 11 in the second lamination group to the empty foil areas 111 on the positive electrode 11 in the third lamination group by welding; fix all the empty foil areas 121 on the negative electrode 12 in the second lamination group to the empty foil areas 121 on the negative electrode 12 in the third lamination group by welding.

[0084] ...

[0085] Perform (N-1) level welding: fix the empty foil areas 111 on all the positive electrode sheets 11 in the (N-1) stack to the empty foil areas 111 on some of the positive electrode sheets 11 in the Nth stack by welding; fix the empty foil areas 121 on all the negative electrode sheets 12 in the (N-1) stack to the empty foil areas 121 on some of the negative electrode sheets 12 in the Nth stack by welding.

[0086] Perform N-level welding: Fix all the empty foil areas 111 on the positive electrode 11 in the Nth lamination group by welding, so that all the empty foil areas 111 on the positive electrode 11 are welded together to form a positive electrode tab 102; fix all the empty foil areas 121 on the negative electrode 12 in the Nth lamination group by welding, so that all the empty foil areas 121 on the negative electrode 12 are welded together to form a negative electrode tab 103.

[0087] In one embodiment, the bare cell 1 further includes a positive conductive handle 14 and a negative conductive handle 15, and the method for preparing the bare cell further includes:

[0088] During N-level welding, the positive electrode conductive handle 14 is fixed to the empty foil area 111 on the positive electrode sheet 11 in the Nth lamination group by welding, and the negative electrode conductive handle 15 is fixed to the empty foil area 121 on the negative electrode sheet 12 in the Nth lamination group by welding.

[0089] This embodiment uses a three-stage welding process as an example to illustrate the preparation method of the bare battery cell:

[0090] 1. Multiple positive electrode plates 11 are divided into three groups according to the length of their empty foil regions 111. The length of the empty foil regions 111 in the three groups of positive electrode plates 11 increases sequentially. The first group of positive electrode plates 11 includes multiple first positive electrode plates 11A, the second group of positive electrode plates 11 includes multiple second positive electrode plates 11B, and the third group of positive electrode plates 11 includes multiple third positive electrode plates 11C. Multiple negative electrode plates 12 are divided into three groups according to the length of their empty foil regions 121. The length of the empty foil regions 121 in the three groups of negative electrode plates 12 increases sequentially. The first group of negative electrode plates 12 includes multiple first negative electrode plates 12A, the second group of negative electrode plates 12 includes multiple second negative electrode plates 12B, and the third group of negative electrode plates 12 includes multiple third negative electrode plates 12C.

[0091] 2. Stack all (20-30 sheets) of the first positive electrode 11A and all (20-30 sheets) of the first negative electrode 12A (separated by a separator 13 between adjacent first positive electrode 11A and first negative electrode 12A), and then stack 3-10 sheets of the second positive electrode 11B and 3-10 sheets of the second negative electrode 12B (separated by a separator 13 between adjacent second positive electrode 11B and second negative electrode 12B), and perform primary welding on the empty foil areas of the above positive and negative electrode sheets respectively;

[0092] 3. Based on the semi-finished product of the first-stage welding, continue to stack 20-30 second positive electrode sheets 11B and 20-30 second negative electrode sheets 12B, and then stack 3-10 third positive electrode sheets 11C and 3-10 third negative electrode sheets 12C, and perform secondary welding on the empty foil areas of the above positive and negative electrode sheets respectively.

[0093] 4. Based on the semi-finished product after secondary welding, continue to stack the remaining third positive electrode 11C and third negative electrode 12C, and perform tertiary welding on the positive electrode conductive handle 14 and the negative electrode conductive handle 15 to the third positive electrode 11C and the third negative electrode 12C respectively.

[0094] This invention also provides a battery, particularly a stacked battery, comprising the bare cell 1 described above.

[0095] The bare cell 1 provided in this embodiment enables multiple-stage welding by setting the empty foil area of ​​the electrode sheets to different lengths. Each welding operation involves a relatively small number of electrode sheets and a relatively thin layer of stacked empty foil areas (i.e., dividing a single welding operation into multiple welding operations with fewer electrode sheets per operation). This avoids incomplete soldering, improves welding quality, increases the number of electrode layers, and enhances the cell's capacity. Simultaneously, staged welding solves the problem of difficulty in gathering the empty foil areas of stacked cells, reducing the probability of the outermost empty foil area being torn off.

[0096] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A bare battery cell, comprising a plurality of electrode plates and a separator, wherein the plurality of electrode plates include a plurality of positive electrode plates and a plurality of negative electrode plates, the plurality of positive electrode plates and the plurality of negative electrode plates are arranged alternately in sequence, adjacent positive electrode plates and negative electrode plates are separated by the separator, both the positive electrode plates and the negative electrode plates are provided with empty foil areas, the empty foil areas of the plurality of positive electrode plates are stacked and then welded to form a positive electrode tab, and the empty foil areas of the plurality of negative electrode plates are stacked and then welded to form a negative electrode tab; Its features are, The positive electrode sheets are divided into multiple groups according to the length of their empty foil areas. Each group contains multiple positive electrode sheets. The length of the empty foil areas on the multiple positive electrode sheets in the same group is the same. The length of the empty foil areas on the positive electrode sheets in each group is different. The multiple groups of positive electrode sheets are stacked sequentially along the thickness direction of the positive electrode sheets in order of increasing length of their empty foil areas. The positive electrode tab is formed by stacking the empty foil areas of the multiple groups of positive electrode sheets and then welding them in stages. When forming the positive electrode tab by stage welding, along the thickness direction of the positive electrode sheets, the empty foil areas on all the positive electrode sheets in the previous group are fixed to the empty foil areas on some of the positive electrode sheets in the next adjacent group by welding. And / or, multiple negative electrode sheets are divided into multiple groups according to the length of their empty foil areas. Each group contains multiple negative electrode sheets. The length of the empty foil areas on multiple negative electrode sheets in the same group is the same. The length of the empty foil areas on the negative electrode sheets in each group is different. Multiple groups of negative electrode sheets are stacked sequentially along the thickness direction of the negative electrode sheets in order of increasing length of their empty foil areas. The negative electrode tab is formed by stacking the empty foil areas of multiple groups of negative electrode sheets through graded welding. When forming the negative electrode tab through graded welding, along the thickness direction of the negative electrode sheets, the empty foil areas on all the negative electrode sheets in the previous group are fixed to the empty foil areas on some of the negative electrode sheets in the next adjacent group by welding.

2. The bare battery cell as described in claim 1, characterized in that, When the positive electrode tab is formed by graded welding, the ratio of the number of positive electrode pieces participating in welding in the previous group to the number of positive electrode pieces participating in welding in the next adjacent group is (2:1) to (30:1). And / or, when the negative electrode tab is formed by graded welding, the ratio of the number of negative electrode pieces participating in welding in the previous group to the number of negative electrode pieces participating in welding in the next adjacent group is (2:1) to (30:1).

3. The bare battery cell as described in claim 1, characterized in that, The number of positive electrode plates in each group shall not exceed 50; and / or the number of negative electrode plates in each group shall not exceed 50.

4. The bare battery cell as described in claim 1, characterized in that, The ratio of the length of the empty foil region of the previous group of positive electrode plates to the length of the empty foil region of the next adjacent group of positive electrode plates is 1:(1.2-4). And / or, the ratio of the length of the empty foil region of the previous set of negative electrode sheets to the length of the empty foil region of the adjacent next set of negative electrode sheets is 1:(1.2-4).

5. The bare battery cell as described in claim 1, characterized in that, The length difference between the empty foil area of ​​the previous group of positive electrode plates and the empty foil area of ​​the adjacent next group of positive electrode plates is 1.5mm to 5mm; And / or, the length difference between the empty foil area of ​​the previous set of negative electrode sheets and the empty foil area of ​​the adjacent next set of negative electrode sheets is 1.5mm to 5mm.

6. The bare battery cell as described in claim 1, characterized in that, The bare battery cell also includes a positive conductive handle and a negative conductive handle. The positive conductive handle is fixed to the positive electrode tab by welding, and the negative conductive handle is fixed to the negative electrode tab by welding.

7. A method for preparing a bare battery cell, characterized in that, The bare battery cell used in any one of claims 1-6, wherein the method for preparing the bare battery cell comprises: S10: Provides an electrode and a separator, wherein the electrode includes a plurality of positive electrode plates and a plurality of negative electrode plates; S20: The plurality of positive electrode sheets, the plurality of negative electrode sheets, and the separator are stacked in the order of "positive electrode sheet-separator-negative electrode sheet" or "negative electrode sheet-separator-positive electrode sheet". The empty foil areas of the plurality of positive electrode sheets are stacked and then welded to form a positive electrode tab. The empty foil areas of the plurality of negative electrode sheets are stacked and then welded to form a negative electrode tab. At least one of the positive electrode tab and the negative electrode tab is formed by graded welding.

8. The method for preparing a bare battery cell as described in claim 7, characterized in that, The positive electrode tab is formed by hierarchical welding of the empty foil regions of the multiple positive electrode sheets. The step of forming the positive electrode tab by hierarchical welding of the empty foil regions of the multiple positive electrode sheets includes: The positive electrode plates are divided into multiple groups according to the length of their empty foil regions. The length of the empty foil regions of the positive electrode plates in the multiple groups increases sequentially, and the number of positive electrode plates in each group is multiple. The positive electrode tab is formed by stacking the empty foil areas of multiple sets of positive electrode sheets and then welding them in stages; wherein, when forming the positive electrode tab by stage welding, along the thickness direction of the positive electrode sheet, all the empty foil areas on the positive electrode sheets in the previous set are fixed to the empty foil areas on some of the positive electrode sheets in the next adjacent set by welding.

9. The method for preparing a bare battery cell as described in claim 7, characterized in that, The negative electrode tab is formed by graded welding of the empty foil areas of multiple negative electrode sheets. The step of forming the negative electrode tab by graded welding of the empty foil areas of multiple negative electrode sheets includes: The multiple negative electrode sheets are divided into multiple groups according to the length of their empty foil areas. The length of the empty foil areas of the multiple groups of negative electrode sheets increases sequentially, and the number of negative electrode sheets in each group is multiple. The negative electrode tab is formed by stacking the empty foil areas of multiple sets of negative electrode sheets and then welding them in stages; wherein, when forming the negative electrode tab by stage welding, along the thickness direction of the negative electrode sheet, all the empty foil areas on the negative electrode sheets in the previous set are fixed to the empty foil areas on some of the negative electrode sheets in the next adjacent set by welding.

10. A battery, characterized in that, Includes bare cells as described in any one of claims 1-6.

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