CN115149112A - Naked battery core, preparation method of naked battery core and battery - Google Patents

Abstract

The invention provides a bare cell, which comprises a plurality of pole pieces and diaphragms, wherein the pole pieces comprise a plurality of positive pole pieces and a plurality of negative pole pieces, the positive pole pieces are divided into a plurality of groups according to the lengths of empty foil areas of the positive pole pieces, the positive pole pieces are sequentially overlapped according to the length sequence from short to long of the empty foil areas of the positive pole pieces, and the empty foil areas of the positive pole pieces are overlapped and then welded in a grading manner to form positive pole lugs; and/or the plurality of negative plates are divided into a plurality of groups according to the lengths of the empty foil areas, the plurality of groups of negative plates are sequentially overlapped according to the order of the lengths of the empty foil areas from short to long, and the empty foil areas of the plurality of groups of negative plates are overlapped and then welded in a grading way to form negative electrode lugs. According to the invention, the empty foil areas of the pole pieces are set to be different in length, so that the graded welding can be carried out, the welding effect is improved, the cold joint is avoided, the lamination layer number of the pole pieces is increased, and the capacity of the battery cell is improved. The invention also provides a preparation method of the bare cell and a battery.

Description

Naked battery core, preparation method of naked battery core and battery

Technical Field

The invention relates to the technical field of batteries, in particular to a bare cell, a preparation method of the bare cell and a battery.

Background

High energy density batteries are one of the current development directions for lithium batteries. For laminated cells, the greater the number of laminated layers, the higher the capacity of the cell. However, as the number of layers of the laminated sheet increases, the thickness of the empty foil area of the copper foil and/or the aluminum foil increases, which tends to cause cold joint during soldering. Due to the current welding process, the number of lamination layers of the cell is generally below 50. How to improve the structure and the welding method of the empty foil area and increase the lamination number of the battery core is an important problem to be solved for improving the battery capacity.

Disclosure of Invention

The invention aims to provide a naked battery cell, which can perform graded welding by setting the empty foil areas of the pole pieces to different lengths, thereby improving the welding effect, avoiding rosin joint, increasing the lamination number of the pole pieces and improving the capacity of the battery cell.

The invention provides a bare cell, which comprises a plurality of pole pieces and diaphragms, wherein the pole pieces comprise a plurality of positive pole pieces and a plurality of negative pole pieces, the positive pole pieces and the negative pole pieces are sequentially and alternately arranged, the adjacent positive pole pieces and the negative pole pieces are separated by the diaphragms, the positive pole pieces and the negative pole pieces are respectively provided with a blank foil area, the blank foil areas of the positive pole pieces are overlapped and then welded to form positive pole lugs, and the blank foil areas of the negative pole pieces are overlapped and then welded to form negative pole lugs;

the positive plates are divided into a plurality of groups according to the lengths of the empty foil areas of the positive plates, the number of the positive plates in each group is at least one, the lengths of the empty foil areas on the positive plates in the same group are the same, the lengths of the empty foil areas of the positive plates in each group are different, the plurality of groups of positive plates are sequentially overlapped along the thickness direction of the positive plates according to the sequence of the lengths of the empty foil areas from short to long, and the positive lugs are formed by overlapping and then welding the empty foil areas of the plurality of groups of positive plates in a grading manner;

and/or, a plurality of the negative pole pieces are divided into a plurality of groups according to the lengths of the empty foil areas of the negative pole pieces, the number of the negative pole pieces in each group is at least one, the lengths of the empty foil areas on the negative pole pieces in the same group are the same, the lengths of the empty foil areas of the negative pole pieces in each group are different, the negative pole pieces in the plurality of groups are sequentially stacked and arranged along the thickness direction of the negative pole pieces according to the sequence from short to long of the lengths of the empty foil areas of the negative pole pieces, and the negative pole ears are formed by the plurality of groups of the empty foil areas of the negative pole pieces through graded welding after stacking.

In an implementable manner, the number of positive electrode plates in each group is plural. In a practical mode, the number of the positive plates in each group does not exceed 50, or is 10-50, or is 15-40, and the limitation of the number can further ensure that the step welding does not generate cold welding. The lengths of the empty foil areas on the plurality of positive plates in the same group are the same. And/or the number of the negative plates in each group is multiple. In a practical mode, the number of the negative electrode sheets in each group is not more than 50, or 10 to 50, or 15 to 40, and the limitation of the number can further ensure that the step welding does not generate cold welding. The lengths of the empty foil areas on the negative electrode plates in the same group are the same.

In a realizable mode, when the positive electrode tab is formed through stepped welding, the empty foil areas on all the positive electrode sheets in the upper group and the empty foil areas on the positive electrode sheets in the adjacent lower group are fixed through welding along the thickness direction of the positive electrode sheets; and/or when the negative electrode tab is formed by graded welding, the empty foil areas on all the negative electrode sheets in the upper group and the empty foil areas on part of the negative electrode sheets in the adjacent lower group are fixed by welding along the thickness direction of the negative electrode sheets.

In a realizable manner, when the positive electrode tab is formed by staged welding, the ratio of the number of the positive electrode tabs that participate in welding in the previous group to the number of the positive electrode tabs that participate in welding in the next adjacent group is (2; and/or when the negative electrode tab is formed by step welding, the ratio of the number of the negative electrode tabs participating in welding in the previous group to the number of the negative electrode tabs participating in welding in the next adjacent group is (2.

In an achievable mode, the ratio of the length of the empty foil area of the positive electrode plate in the previous group to the length of the empty foil area of the positive electrode plate in the next adjacent group is 1 (1.2-4); and/or the ratio of the length of the empty foil area of the last group of negative electrode plates to the length of the empty foil area of the next adjacent group of negative electrode plates is 1 (1.2-4).

In a realizable mode, the lengths of the empty foil areas of the positive plates in the previous group and the empty foil areas of the positive plates in the next adjacent group are different by 1.5-5 mm; and/or the length difference between the empty foil area of the previous group of negative plates and the empty foil area of the next adjacent group of negative plates is 1.5-5 mm.

In an implementation manner, the bare cell further comprises a positive conductive handle and a negative conductive handle, the positive conductive handle is fixed to the positive tab by welding, and the negative conductive handle is fixed to the negative tab by welding. The welding position of the conductive handle is not particularly limited, and the positive/negative conductive handle can be welded with the last group of positive/negative plates on the side of the last group of positive/negative plates close to the first group of positive/negative plates or on the side of the last group of positive/negative plates far away from the first group of positive/negative plates; the positive/negative electrode conductive handle can also be inserted between the empty foil areas of any positive/negative electrode plate in the step welding process and is welded with the empty foil areas of the adjacent positive/negative electrode plates.

In an implementable manner, the positive and negative tabs are located on the same or different sides of the bare cell.

The invention also provides a preparation method of the naked electric core, which is applied to the naked electric core, and the preparation method of the naked electric core comprises the following steps:

s10: providing a pole piece and a diaphragm, wherein the pole piece comprises a plurality of positive pole pieces and a plurality of negative pole pieces;

s20: stacking the plurality of positive plates, the plurality of negative plates and the diaphragms according to the sequence of positive plate-diaphragm-negative plate or negative plate-diaphragm-positive plate, forming positive tabs by welding empty foil areas of the plurality of positive plates after stacking, and forming negative tabs by welding empty foil areas of the plurality of negative plates after stacking; wherein at least one of the positive electrode tab and the negative electrode tab is formed by step welding.

In one implementation, the step of forming the positive electrode tab by stepped welding from the empty foil regions of the plurality of positive electrode sheets comprises:

dividing the plurality of positive plates into a plurality of groups according to the lengths of the empty foil areas of the positive plates, wherein the lengths of the empty foil areas of the plurality of groups of positive plates are sequentially increased, and the number of the positive plates in each group is multiple;

overlapping the empty foil areas of the plurality of groups of positive plates and then forming the positive lugs through graded welding; when the positive tab is formed by graded welding, the empty foil areas on all the positive tabs in the upper group and the empty foil areas on the parts in the adjacent lower group are fixed by welding along the thickness direction of the positive tabs.

In an implementable manner, the bare cell further comprises a positive conductive handle, and the method of making the bare cell further comprises:

when the empty foil areas of the last group of positive plates are welded, the positive conductive handle and the empty foil areas on the last group of positive plates are fixed through welding; or in the process of graded welding, the positive conductive handle is inserted between the empty foil areas of any one positive plate and is fixed with the empty foil areas of the adjacent positive plates through welding.

In an implementable manner, the step of forming the negative electrode tab by the step of welding the empty foil regions of the plurality of negative electrode sheets comprises:

dividing the plurality of negative plates into a plurality of groups according to the lengths of the empty foil areas of the negative plates, wherein the lengths of the empty foil areas of the plurality of groups of negative plates are sequentially increased, and the number of the negative plates in each group is multiple;

overlapping the empty foil areas of the plurality of groups of negative pole pieces and then forming the negative pole ears by stepped welding; when the negative electrode tabs are formed through graded welding, the empty foil areas on all the negative electrode tabs in the upper group and the empty foil areas on the partial negative electrode tabs in the next adjacent group are fixed through welding in the thickness direction of the negative electrode tabs.

In an implementable manner, the bare cell further includes a negative conductive handle, and the method of making the bare cell further includes:

when the empty foil areas of the last group of negative plates are welded, the negative conductive handle and the empty foil areas on the last group of negative plates are fixed through welding; or in the process of step welding, the negative electrode conductive handle is inserted between the empty foil regions of any one of the negative electrode sheets and is fixed with the empty foil regions of the adjacent negative electrode sheets through welding.

The invention also provides a battery, which comprises the naked battery core.

According to the bare cell provided by the invention, the positive plates and/or the negative plates are respectively divided into a plurality of groups according to different lengths of the empty foil areas, the plurality of groups of positive plates are sequentially stacked according to the sequence of the lengths of the empty foil areas from short to long and are welded in a grading manner to form the positive electrode lugs, and the plurality of groups of negative plates are sequentially stacked according to the sequence of the lengths of the empty foil areas from short to long and are welded in a grading manner to form the negative electrode lugs; during the step welding, the connection is carried out through the empty foil area with longer length, so that the multiple welding is realized. According to the invention, the empty foil areas of the pole pieces are set to be different in length, so that multiple times of graded welding can be carried out, the welding effect is improved, the cold joint is avoided, the lamination layer number of the pole pieces is increased, and the capacity of the battery cell is improved.

Drawings

Fig. 1 is a top view of a bare cell in an embodiment of the invention.

Fig. 2 is a side view of fig. 1.

Fig. 3 is a schematic structural diagram of a positive plate, a negative plate and a separator in an embodiment of the invention.

Fig. 4 is a top view of a bare cell in another embodiment of the invention.

Fig. 5 is a top view of a bare cell in another embodiment of the invention.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

The terms "first," "second," "third," "fourth," and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.

The terms of orientation, up, down, left, right, front, back, top, bottom, and the like (if any) referred to in the specification and claims of the present invention are defined by the positions of structures in the drawings and the positions of the structures relative to each other, only for the sake of clarity and convenience in describing the technical solutions. It is to be understood that the use of the directional terms should not be taken to limit the scope of the claims.

As shown in fig. 1 to 3, a bare cell 1 provided in an embodiment of the present invention includes a plurality of pole pieces and a plurality of separators 13, where the plurality of pole pieces include a plurality of positive pole pieces 11 and a plurality of negative pole pieces 12, the plurality of positive pole pieces 11 and the plurality of negative pole pieces 12 are sequentially and alternately disposed, and the separators 13 are disposed between adjacent positive pole pieces 11 and adjacent negative pole pieces 12 and separated by the separators 13. The positive electrode tab 11 and the negative electrode tab 12 are each provided with a blank foil region 111/121 and a coating region 112/122, and the blank foil region 111/121 is located on one side of the coating region 112/122. Wherein the coated regions 112/122 are coated with an active material, the empty foil regions 111/121 are not coated with an active material, and the empty foil regions 111 and 121 on the positive and negative electrode sheets 11 and 12 are both formed in the shape of tabs by cutting. Naked electric core 1 is being formed through lamination, welding back by a plurality of positive pole pieces 11, a plurality of negative pole piece 12 and diaphragm 13, and the main part 101 of naked electric core 1 is formed after the coating district 112 of a plurality of positive pole pieces 11, the coating district 122 of a plurality of negative pole pieces 12 and diaphragm 13 superpose. Empty foil district 111 of a plurality of positive plates 11 forms bare electric core 1's positive ear 102 through the welding after the stack, and the empty foil district 121 of a plurality of negative pole pieces 12 forms bare electric core 1's negative ear 103 through the welding after the stack.

As shown in fig. 1 to 3, as an embodiment, the plurality of positive electrode sheets 11 are divided into a plurality of groups according to the length of the empty foil area 111 thereof, the number of the positive electrode sheets 11 in each group is at least one, the length of the empty foil area 111 on the positive electrode sheet 11 in the same group is the same, the length of the empty foil area 111 of each group of positive electrode sheets 11 is different, the plurality of groups of positive electrode sheets 11 are sequentially stacked along the thickness direction of the positive electrode sheets 11 according to the length sequence of the empty foil area 111 thereof from short to long (i.e., stacked along the thickness direction of the bare cell 1), and the empty foil areas 111 of the plurality of groups of positive electrode sheets 11 are stacked and then welded in a graded manner to form the positive electrode tab 102 of the bare cell 1 (in the graded welding, only the empty foil areas 111 of two adjacent groups of positive electrode sheets 11 are welded at each grade, and then the empty foil area 111 with a longer length is switched to perform the next-stage welding).

The negative plates 12 are divided into multiple groups according to the lengths of the empty foil areas 121, the number of the negative plates 12 in each group is at least one, the lengths of the empty foil areas 121 on the negative plates 12 in the same group are the same, the lengths of the empty foil areas 121 of the negative plates 12 in each group are different, the negative plates 12 in the multiple groups are sequentially stacked along the thickness direction of the negative plates 12 in the sequence from short to long according to the lengths of the empty foil areas 121 (namely, the negative plates are stacked along the thickness direction of the bare cell 1), and the empty foil areas 121 of the negative plates 12 in the multiple groups are stacked and then welded in a grading manner to form the negative electrode tab 103 of the bare cell 1 (when welding in a grading manner, only the empty foil areas 121 of two adjacent groups of negative plates 12 in each grade are welded, and then the empty foil areas 121 with longer lengths are connected in a transferring manner to perform the next-stage welding).

For example, the plurality of positive electrode sheets 11 are divided into N groups according to the length of the empty foil area 111, that is, the plurality of groups of positive electrode sheets 11 are the first group of positive electrode sheets 11 to the nth group of positive electrode sheets 11; dividing the negative plates 12 into N groups according to the lengths of the empty foil regions 121, namely, the negative plates 12 in the multiple groups are respectively the first group of negative plates 12 to the nth group of negative plates 12; wherein N is a positive integer greater than or equal to 2.

The step welding specifically comprises: when the positive tab 102 is formed by step welding, the empty foil area 111 on the M-th group positive plate 11 and the empty foil area 111 on part of the (M + 1) -th group positive plate 11 are fixed by welding, and then the welded empty foil area 111 on the (M + 1) -th group positive plate 11 is switched, and the empty foil area 111 on the (M + 1) -th group positive plate 11 and the empty foil area 111 on part of the (M + 2) -th group positive plate 11 are fixed by welding, and so on, until the empty foil area 111 on the (N-1) -th group positive plate 11 and the empty foil areas 111 on all the N-th group positive plates 11 are fixed by welding. When the negative electrode tab 103 is formed by the step welding, the empty foil region 121 on the M-th group of negative electrode sheets 12 and the empty foil region 121 on a part of the (M + 1) -th group of negative electrode sheets 12 are fixed by welding, and then the empty foil region 121 on the (M + 1) -th group of negative electrode sheets 12 is switched by the empty foil region 121 on the welded (M + 1) -th group of negative electrode sheets 12, and the empty foil region 121 on the (M + 1) -th group of negative electrode sheets 12 and the empty foil region 121 on a part of the (M + 2) -th group of negative electrode sheets 12 are fixed by welding, and so on, until the empty foil region 121 on the (N-1) -th group of negative electrode sheets 12 and the empty foil regions 121 on all the N-th group of negative electrode sheets 12 are fixed by welding. Wherein M is a positive integer greater than or equal to 1 and less than N.

In actual use, one of the positive electrode tab 102 and the negative electrode tab 103 may be formed by step welding, and the other may be formed by welding in a conventional manner (for example, by one-time welding). For example, the positive tab 102 is formed by step welding, the negative tab 103 is formed by conventional welding, and then the plurality of positive tabs 11 are grouped in the above manner, and then the positive tab 102 is formed by step welding; while the empty foil regions 121 of the negative electrode tabs 12 are the same length, the empty foil regions 121 of the negative electrode tabs 12 are stacked and then welded (e.g., welded at one time) in a conventional manner to form the negative electrode tabs 103. Conversely, the negative tab 103 may be formed by step welding and the positive tab 102 may be formed by welding in a conventional manner. Preferably, both the positive electrode tab 102 and the negative electrode tab 103 are formed by step welding.

In the bare cell 1 provided by this embodiment, the positive plates 11 and the negative plates 12 are respectively divided into a plurality of groups according to different lengths of the empty foil regions 111/121, the plurality of groups of positive plates 11 are sequentially stacked and arranged according to the order of the lengths of the empty foil regions 111 from short to long and are welded in a graded manner to form the positive tab 102, and the plurality of groups of negative plates 12 are sequentially stacked and arranged according to the order of the lengths of the empty foil regions 121 from short to long and are welded in a graded manner to form the negative tab 103; during the step welding, the connection is carried out through the empty foil area with longer length, so that the multiple welding is realized. This embodiment sets up to different length through the empty paper tinsel district with the pole piece to can carry out a lot of hierarchical welding, the quantity of pole piece is less relatively when welding at every turn, and the superimposed thickness in the time of welding space-time paper tinsel district is also relatively thin (being about to present welding divide into welding many times, and pole piece quantity when welding at every turn is still less), thereby avoids the rosin joint, improves the welding effect, and increases the lamination number of piles of pole piece, promotes the capacity of electric core. Meanwhile, the problem that the empty foil area of the traditional laminated battery core is difficult to fold can be solved through graded welding, and the probability that the empty foil area at the outermost layer is torn off is reduced.

As shown in fig. 1 and fig. 2, as an embodiment, the bare cell 1 further includes a positive conductive handle 14 and a negative conductive handle 15, the positive conductive handle 14 and the positive tab 102 are fixed by welding, and the negative conductive handle 15 and the negative tab 103 are fixed by welding.

As shown in fig. 2, as an embodiment, the positive conductive handle 14 is fixed to the empty foil area 111 on the last group of positive plates 11 (i.e., the nth group of positive plates 11) by welding, and the negative conductive handle 15 is fixed to the empty foil area 121 on the last group of negative plates 12 (i.e., the nth group of negative plates 12) by welding.

As shown in fig. 2, as an embodiment, the positive conductive handle 14 is located on one side of the last group of positive electrode tabs 11 close to the first group of positive electrode tabs 11, and the negative conductive handle 15 is located on one side of the last group of negative electrode tabs 12 close to the first group of negative electrode tabs 12.

As shown in fig. 1 and 2, in one embodiment, tab paste 16 is provided on each of the positive electrode conductive tab 14 and the negative electrode conductive tab 15.

As shown in fig. 2, as an embodiment, the number of positive electrode sheets 11 in each group is plural, and the lengths of the empty foil regions 111 on the plural positive electrode sheets 11 in the same group are the same. The number of the negative electrode sheets 12 in each group is multiple, and the lengths of the empty foil regions 121 on the negative electrode sheets 12 in the same group are the same.

As shown in fig. 1 and 2, in one embodiment, when the positive electrode tab 102 is formed by step welding, the empty foil regions 111 on all the positive electrode tabs 11 in the upper group and the empty foil regions 111 on the internal partial positive electrode tabs 11 in the adjacent lower group are fixed by welding in the thickness direction of the positive electrode tabs 11; when the negative electrode tabs 103 are formed by step welding, the empty foil regions 121 on all the negative electrode sheets 12 in the upper group and the empty foil regions 121 on the internal partial negative electrode sheets 12 in the adjacent lower group are fixed by welding in the thickness direction of the negative electrode sheets 12.

As shown in fig. 1 and 2, in one embodiment, the plurality of positive electrode sheets 11 are divided into three groups according to the lengths of the empty foil areas 111 of the positive electrode sheets 11, the lengths of the empty foil areas 111 of the three groups of positive electrode sheets 11 are sequentially increased, the first group of positive electrode sheets 11 includes a plurality of first positive electrode sheets 11A, the second group of positive electrode sheets 11 includes a plurality of second positive electrode sheets 11B, and the third group of positive electrode sheets 11 includes a plurality of third positive electrode sheets 11C. The negative plates 12 are divided into three groups according to the lengths of the empty foil areas 121, the lengths of the empty foil areas 121 of the negative plates 12 of the three groups increase progressively in sequence, the first group of negative plates 12 comprises a plurality of first negative plates 12A, the second group of negative plates 12 comprises a plurality of second negative plates 12B, and the third group of negative plates 12 comprises a plurality of third negative plates 12C.

When the positive electrode tab 102 is formed by step welding, the empty foil regions 111 on all the first positive electrode sheets 11A in the first group and the empty foil regions 111 on the second positive electrode sheets 11B in the second group form one-step welding (H1 in the drawing indicates the location of the one-step welding), the empty foil regions 111 on all the second positive electrode sheets 11B in the second group (including the portion of the second positive electrode sheets 11B participating in the one-step welding) and the empty foil regions 111 on the third positive electrode sheets 11C in the third group form two-step welding (H2 in the drawing indicates the location of the two-step welding), and the empty foil regions 111 on all the third positive electrode sheets 11C in the third group (including the portion of the third positive electrode sheets 11C participating in the two-step welding) and the positive electrode conductive handle 14 form three-step welding (H3 in the drawing indicates the location of the three-step welding).

When the negative electrode tabs 103 are formed by step welding, the empty foil regions 121 on all the first negative electrode sheets 12A in the first group and the empty foil regions 121 on the second negative electrode sheets 12B in the second group form one-step welding (H1 in the figure indicates the location of the one-step welding), the empty foil regions 121 on all the second negative electrode sheets 12B in the second group (including the portion of the second negative electrode sheets 12B participating in the one-step welding) and the empty foil regions 121 on the third negative electrode sheets 12C in the third group form two-step welding (H2 in the figure indicates the location of the two-step welding), and the empty foil regions 121 on all the third negative electrode sheets 12C in the third group (including the portion of the third negative electrode sheets 12C participating in the two-step welding) and the negative electrode conductive handle 15 form three-step welding (H3 in the figure indicates the location of the three-step welding).

In one embodiment, when the positive electrode tab 102 is formed by the step welding, the ratio of the number of positive electrode sheets 11 subjected to the welding in the previous group to the number of positive electrode sheets 11 subjected to the welding in the next adjacent group is (2; for example, the ratio of the number of first positive electrode tab 11A and second positive electrode tab 11B participating in welding is (2.

When the negative electrode tabs 103 are formed by the step welding, the ratio of the number of negative electrode sheets 12 that participate in the welding in the previous group to the number of negative electrode sheets 12 that participate in the welding in the next adjacent group is (2; for example, the ratio of the number of welding-participating first negative electrode tabs 12A to the number of welding-participating second negative electrode tabs 12B is (2.

In one embodiment, the number of the last group of positive electrode tabs 11 (i.e., the nth group of positive electrode tabs 11) is 10 to 50, or 15 to 40. The number of the last group of negative electrode tabs 12 (i.e., the nth group of negative electrode tabs 12) is 10 to 50, or 15 to 40.

In one embodiment, the number of the positive electrode sheets 11 in each group is not more than 50, or 10 to 50, or 15 to 40. In one embodiment, the number of the negative electrode sheets 12 in each group is not more than 50, or 10 to 50, or 15 to 40.

In one embodiment, the ratio of the length of the empty foil area 111 of the previous group of positive electrode sheets 11 to the length of the empty foil area 111 of the next adjacent group of positive electrode sheets 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 tab 11A: the length of the empty foil region 111 of the second positive electrode tab 11B =1 (1.2-4) or 1 (1.5-4).

In one embodiment, the lengths of the empty foil area 111 of the previous group of positive plates 11 and the empty foil area 111 of the next adjacent group of positive plates 11 are different by 1.5mm to 5mm, or 2.5mm to 4mm, or 3mm to 4mm; for example, the lengths of the empty foil section 111 of the first positive electrode sheet 11A and the empty foil section 111 of the second positive electrode sheet 11B differ by 1.5mm to 5mm.

In one embodiment, the ratio of the length of the empty foil region 121 of the negative electrode sheet 12 in the previous group to the length of the empty foil region 121 of the negative electrode sheet 12 in the next adjacent group is 1 (1.2-4). For example, the length of the empty foil region 121 of the first negative electrode tab 12A: the length of the empty foil region 121 of the second negative electrode tab 12B =1 (1.2-4).

In one embodiment, the lengths of the empty foil region 121 of the upper group of negative electrode sheets 12 and the empty foil region 121 of the adjacent lower group of negative electrode sheets 12 are different by 1.5mm to 5mm, or 2.5mm to 4mm, or 3mm to 4mm; for example, the lengths of the empty foil region 121 of the first negative electrode tab 12A and the empty foil region 121 of the second negative electrode tab 12B are different by 1.5mm to 5mm.

As shown in fig. 1, as an embodiment, positive tab 102 and negative tab 103 are located on the same side of bare cell 1.

As shown in fig. 1, as an embodiment, positive electrode tab 102 and negative electrode tab 103 are both located on the same side of bare cell 1 along length direction L of bare cell 1. As shown in fig. 4, as another embodiment, positive electrode tab 102 and negative electrode tab 103 are both located on the same side of bare cell 1 in the width direction W of bare cell 1.

As shown in fig. 5, as an embodiment, positive electrode tab 102 and negative electrode tab 103 are located naked electric core 1 different sides, and positive electrode tab 102 and negative electrode tab 103 are located naked electric core 1 respectively along the opposite sides on naked electric core 1's length direction L.

As an embodiment, the bare cell 1 may be laminated in the order of "positive electrode tab 11-diaphragm 13-negative electrode tab 12" or "negative electrode tab 12-diaphragm 13-positive electrode tab 11" during lamination, and the positive electrode tab 11 and the negative electrode tab 12 are laminated in the order of the length of the empty foil region 111/121 from short to long during lamination.

As an embodiment, naked electric core 1 can encapsulate through the plastic-aluminum membrane, also can encapsulate through the metal casing.

The embodiment of the invention also provides a preparation method of the naked electric core, which is applied to the naked electric core 1, and the preparation method of the naked electric core comprises the following steps:

s10: providing a pole piece and a diaphragm 13, wherein the pole piece comprises a plurality of positive pole pieces 11 and a plurality of negative pole pieces 12;

s20: stacking the positive plates 11, the negative plates 12 and the diaphragms 13 in the order of "positive plate 11-diaphragm 13-negative plate 12" or "negative plate 12-diaphragm 13-positive plate 11", stacking the empty foil regions 111 of the positive plates 11, welding to form positive tabs 102, and stacking the empty foil regions 121 of the negative plates 12, welding to form negative tabs 103; wherein at least one of the positive electrode tab 102 and the negative electrode tab 103 is formed by step welding.

In one embodiment, the step of forming positive tab 102 by step welding empty foil areas 111 of plurality of positive electrode sheets 11 and step welding empty foil areas 111 of plurality of positive electrode sheets 11 to form positive tab 102 includes:

dividing the plurality of positive plates 11 into a plurality of groups according to the lengths of the empty foil areas 111 of the positive plates, wherein the lengths of the empty foil areas 111 of the plurality of groups of positive plates 11 are sequentially increased, and the number of the positive plates 11 in each group is multiple;

overlapping the empty foil areas 111 of the plurality of groups of positive plates 11 and then forming the positive tab 102 through graded welding; when the positive electrode tab 102 is formed by step welding, the empty foil regions 111 on all the positive electrode tabs 11 in the previous group and the empty foil regions 111 on the internal partial positive electrode tabs 11 in the next adjacent group are fixed by welding in the thickness direction of the positive electrode tabs 11.

As an embodiment, naked electric core 1 still includes anodal electrically conductive handle 14, and the preparation method of naked electric core still includes:

when the empty foil area 111 of the last group of positive electrode sheets 11 is welded, the positive electrode conductive handle 14 is fixed to the empty foil area 111 of the last group of positive electrode sheets 11 by welding.

As an embodiment, the step of forming the negative electrode tab 103 by the step welding of the empty foil regions 121 of the negative electrode tabs 12 by the step welding includes:

dividing the negative electrode plates 12 into a plurality of groups according to the lengths of the empty foil areas 121 of the negative electrode plates 12, wherein the lengths of the empty foil areas 121 of the negative electrode plates 12 of the plurality of groups are sequentially increased in an increasing manner, and the number of the negative electrode plates 12 in each group is multiple;

overlapping the empty foil areas 121 of the multiple groups of negative plates 12 and then forming the negative electrode tabs 103 through step welding; when the negative electrode tabs 103 are formed by step welding, the empty foil regions 121 on all the negative electrode tabs 12 in the upper group and the empty foil regions 121 on the internal part negative electrode tabs 12 in the next adjacent group are fixed by welding along the thickness direction of the negative electrode tabs 12.

As an embodiment, naked electric core 1 still includes electrically conductive handle 15 of negative pole, and the preparation method of naked electric core still includes:

when the empty foil area 121 of the last group of negative electrode sheets 12 is welded, the negative conductive handle 15 is fixed to the empty foil area 121 of the last group of negative electrode sheets 12 by welding.

In one embodiment, the positive tab 102 and the negative tab 103 are formed by step welding, and the step S20 specifically includes:

dividing the plurality of positive plates 11 into a plurality of groups according to the lengths of the empty foil areas 111 of the positive plates, wherein the lengths of the empty foil areas 111 of the plurality of groups of positive plates 11 are sequentially increased; dividing the plurality of negative plates 12 into a plurality of groups according to the lengths of the empty foil areas 121 of the negative plates, wherein the lengths of the empty foil areas 121 of the plurality of groups of negative plates 12 are sequentially increased;

respectively laminating multiple groups of positive plates 11, multiple groups of negative plates 12 and diaphragms 13 according to the sequence of 'positive plates 11-diaphragms 13-negative plates 12' or 'negative plates 12-diaphragms 13-positive plates 11' to obtain multiple laminated groups (i.e. overlapping the positive plates 11 and the negative plates 12 of the same group level, for example, overlapping the first group of positive plates 11 and the first group of negative plates 12 to obtain a first laminated group \8230; \823030; overlapping the N group of positive plates 11 and the N group of negative plates 12 to obtain an N-th laminated group); the multiple lamination groups are respectively a first lamination group to an Nth lamination group, wherein N is a positive integer greater than or equal to 2; the number of the positive plates 11 in each lamination group is multiple, and the number of the negative plates 12 in each lamination group is multiple;

performing primary welding: fixing the empty foil regions 111 on all the positive plates 11 in the first lamination group and the empty foil regions 111 on the positive plates 11 in the second lamination group by welding, and fixing the empty foil regions 121 on all the negative plates 12 in the first lamination group and the empty foil regions 121 on the negative plates 12 in the second lamination group by welding;

carrying out secondary welding: welding and fixing the empty foil regions 111 on all the positive plates 11 in the second lamination group and the empty foil regions 111 on the positive plates 11 in the third lamination group, and welding and fixing the empty foil regions 121 on all the negative plates 12 in the second lamination group and the empty foil regions 121 on the negative plates 12 in the third lamination group;

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carrying out (N-1) stage welding: fixing the empty foil regions 111 on all the positive plates 11 in the (N-1) th lamination group and the empty foil regions 111 on the positive plates 11 in the Nth lamination group by welding, and fixing the empty foil regions 121 on all the negative plates 12 in the (N-1) th lamination group and the empty foil regions 121 on the negative plates 12 in the Nth lamination group by welding;

and (3) carrying out N-level welding: fixing the empty foil regions 111 on all positive plates 11 in the nth lamination group by welding, so that the empty foil regions 111 on all positive plates 11 are welded together and form positive lugs 102; the empty foil regions 121 on all the negative electrode sheets 12 in the nth stack are fixed by welding, so that the empty foil regions 121 on all the negative electrode sheets 12 are welded together and form the negative electrode tabs 103.

As an embodiment, bare cell 1 further includes positive conductive handle 14 and negative conductive handle 15, and the preparation method of bare cell further includes:

when the N-level welding is performed, the positive conductive handle 14 is fixed to the empty foil area 111 on the positive plate 11 in the nth stack by welding, and the negative conductive handle 15 is fixed to the empty foil area 121 on the negative plate 12 in the nth stack by welding.

In this embodiment, a three-stage welding process is used to illustrate a method for preparing the bare cell:

1. the positive plates 11 are divided into three groups according to the lengths of the empty foil areas 111 of the positive plates 11, the lengths of the empty foil areas 111 of the three groups of positive plates 11 are sequentially increased, the first group of positive plates 11 comprises a plurality of first positive plates 11A, the second group of positive plates 11 comprises a plurality of second positive plates 11B, and the third group of positive plates 11 comprises a plurality of third positive plates 11C. The negative plates 12 are divided into three groups according to the lengths of the empty foil areas 121, the lengths of the empty foil areas 121 of the three groups of negative plates 12 are sequentially increased, the first group of negative plates 12 comprises a plurality of first negative plates 12A, the second group of negative plates 12 comprises a plurality of second negative plates 12B, and the third group of negative plates 12 comprises a plurality of third negative plates 12C;

2. laminating all (20-30) first positive plates 11A and all (20-30) first negative plates 12A (the adjacent first positive plates 11A and the first negative plates 12A are separated by a diaphragm 13), then laminating 3-10 second positive plates 11B and 3-10 second negative plates 12B (the adjacent second positive plates 11B and the second negative plates 12B are separated by the diaphragm 13), and respectively carrying out primary welding on the empty foil areas of the positive and negative plates;

3. continuously stacking 20-30 second positive plates 11B and 20-30 second negative plates 12B on the basis of the primary welded semi-finished product, then stacking 3-10 third positive plates 11C and 3-10 third negative plates 12C, and respectively carrying out secondary welding on the empty foil areas of the positive and negative plates;

4. and on the basis of the semi-finished product of the secondary welding, continuously stacking the rest third positive plate 11C and the rest third negative plate 12C, and respectively carrying out tertiary welding on the positive conductive handle 14 and the negative conductive handle 15 with the third positive plate 11C and the third negative plate 12C.

The embodiment of the invention also provides a battery, in particular to a laminated battery, which comprises the bare cell 1.

Naked electric core 1 that this embodiment provided sets up to different length through the empty paper tinsel district with the pole piece to can carry out a lot of hierarchical welding, the quantity of pole piece is less relatively when welding at every turn, and the time and space paper tinsel district superimposed thickness is also relatively thin (be about to present welding and fall into welding many times, pole piece quantity when welding at every turn is still less) when welding at every turn, thereby avoids the rosin joint, improves the welding effect, and increases the lamination number of piles of pole piece, promotes the capacity of electric core. Meanwhile, the problem that the empty foil area of the laminated battery core is difficult to fold can be solved through graded welding, and the probability that the empty foil area on the outermost layer is torn off is reduced.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (12)

1. A bare cell comprises a plurality of pole pieces and diaphragms, wherein the pole pieces comprise a plurality of positive pole pieces and a plurality of negative pole pieces, the positive pole pieces and the negative pole pieces are sequentially and alternately arranged, the adjacent positive pole pieces and the negative pole pieces are separated by the diaphragms, the positive pole pieces and the negative pole pieces are respectively provided with a blank foil area, the blank foil areas of the positive pole pieces are overlapped and then welded to form positive pole lugs, and the blank foil areas of the negative pole pieces are overlapped and then welded to form negative pole lugs;

the anode tab is characterized in that a plurality of anode tabs are divided into a plurality of groups according to the lengths of empty foil areas of the anode tabs, the number of the anode tabs in each group is at least one, the lengths of the empty foil areas on the anode tabs in the same group are the same, the lengths of the empty foil areas of the anode tabs in each group are different, the plurality of groups of anode tabs are sequentially overlapped along the thickness direction of the anode tabs according to the sequence of the lengths of the empty foil areas from short to long, and the anode tab is formed by overlapping and then welding the empty foil areas of the plurality of groups of anode tabs in a grading manner;

and/or the plurality of negative plates are divided into a plurality of groups according to the lengths of the empty foil areas of the negative plates, the number of the negative plates in each group is at least one, the lengths of the empty foil areas on the negative plates in the same group are the same, the lengths of the empty foil areas of the negative plates in each group are different, the plurality of groups of negative plates are sequentially overlapped along the thickness direction of the negative plates according to the sequence of the lengths of the empty foil areas from short to long, and the negative electrode tabs are formed by the overlapping and then welding the empty foil areas of the plurality of groups of negative plates in a grading manner.

2. The bare cell of claim 1, wherein the number of positive plates in each group is multiple, and the lengths of the empty foil regions on multiple positive plates in the same group are the same;

and/or the number of the negative pole pieces in each group is multiple, and the lengths of the empty foil areas on the multiple negative pole pieces in the same group are the same.

3. The bare cell according to claim 2, wherein, when the positive tab is formed by step welding, the empty foil areas on all the positive tabs in the upper group are fixed by welding with the empty foil areas on some of the positive tabs in the next adjacent group along the thickness direction of the positive tabs;

and/or when the negative electrode tab is formed by graded welding, the empty foil regions on all the negative electrode sheets in the previous group and the empty foil regions on the partial negative electrode sheets in the next adjacent group are fixed by welding along the thickness direction of the negative electrode sheets.

4. The bare cell according to claim 3, wherein, when the positive tab is formed by staged welding, the ratio of the number of positive tabs involved in welding in the previous group to the number of positive tabs involved in welding in the next adjacent group is (2;

and/or, when the negative electrode tab is formed by step welding, the ratio of the number of the negative electrode tabs subjected to welding in the previous group to the number of the negative electrode tabs subjected to welding in the next adjacent group is (2.

5. The bare cell according to claim 2, wherein the number of positive plates in each group is no more than 50; and/or the number of the negative plates in each group is not more than 50.

6. The bare cell according to claim 1, wherein the ratio of the length of the empty foil area of the positive electrode plate in the previous group to the length of the empty foil area of the positive electrode plate in the next adjacent group is 1 (1.2-4);

and/or the ratio of the length of the empty foil area of the last group of negative electrode plates to the length of the empty foil area of the next adjacent group of negative electrode plates is 1 (1.2-4).

7. The bare cell according to claim 1, wherein the difference between the lengths of the empty foil area of the upper group of positive plates and the empty foil area of the next adjacent group of positive plates is 1.5mm to 5mm;

and/or the length difference between the empty foil area of the previous group of negative plates and the empty foil area of the next adjacent group of negative plates is 1.5-5 mm.

8. The bare cell of claim 1, further comprising a positive conductive handle and a negative conductive handle, wherein the positive conductive handle is fixed to the positive tab by welding, and the negative conductive handle is fixed to the negative tab by welding.

9. A preparation method of a naked battery cell, which is applied to the naked battery cell of any one of claims 1 to 8, the preparation method of the naked battery cell comprises the following steps:

s10: providing a pole piece and a diaphragm, wherein the pole piece comprises a plurality of positive pole pieces and a plurality of negative pole pieces;

s20: stacking the positive plates, the negative plates and the diaphragms according to the sequence of 'positive plate-diaphragm-negative plate' or 'negative plate-diaphragm-positive plate', forming positive lugs by welding the empty foil areas of the positive plates after stacking, and forming negative lugs by welding the empty foil areas of the negative plates after stacking; wherein at least one of the positive tab and the negative tab is formed by step welding.

10. The method for preparing a bare cell according to claim 9, wherein the positive tab is formed by staged welding of the empty foil regions of the plurality of positive tabs, and the step of forming the positive tab by staged welding of the empty foil regions of the plurality of positive tabs comprises:

dividing the plurality of positive plates into a plurality of groups according to the lengths of the empty foil areas of the positive plates, wherein the lengths of the empty foil areas of the plurality of groups of positive plates are sequentially increased, and the number of the positive plates in each group is multiple;

overlapping the empty foil areas of the plurality of groups of positive plates and then forming the positive lugs through graded welding; when the positive tab is formed by stepped welding, the empty foil areas on all the positive tabs in the previous group and the empty foil areas on the internal parts in the next adjacent group are fixed by welding along the thickness direction of the positive tabs.

11. The method of preparing a bare cell according to claim 9, wherein the negative electrode tab is formed by step welding of empty foil regions of the negative electrode sheets, and the step of forming the negative electrode tab by step welding of the empty foil regions of the negative electrode sheets comprises:

dividing the plurality of negative plates into a plurality of groups according to the lengths of the empty foil areas of the negative plates, wherein the lengths of the empty foil areas of the plurality of groups of negative plates are sequentially increased, and the number of the negative plates in each group is multiple;

overlapping the empty foil areas of the plurality of groups of negative pole pieces and then forming the negative pole ears by stepped welding; when the negative electrode tab is formed by graded welding, the empty foil areas on all the negative electrode plates in the upper group and the empty foil areas on part of the negative electrode plates in the next adjacent group are fixed by welding along the thickness direction of the negative electrode plates.

12. A battery comprising the bare cell of any of claims 1-8.

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