A lithium battery and a method for manufacturing a lithium battery

Abstract

The present invention provides a lithium battery, including a parallel stacked core; the parallel stacked core includes a first stacked core, a second stacked core, a first positive electrode connecting piece, and a second positive electrode connecting piece; the first positive electrode tab of the first stacked core is fixedly connected to the first positive electrode connecting piece, the second positive electrode tab of the second stacked core is fixedly connected to the second positive electrode connecting piece, and the first positive electrode tab, the first positive electrode tab, the second positive electrode tab, and the second positive electrode tab are arranged in sequence; a corner of the first positive electrode tab extends away from the first stacked core and is fixed with a first auxiliary connecting piece, a corner of the second positive electrode tab extends away from the second stacked core and is fixed with a second auxiliary connecting piece, and the first auxiliary connecting piece and the second auxiliary connecting piece are fixed to each other. The present invention connects the positive electrode tabs of the two stacked cores together by fixing the auxiliary connecting pieces, thereby solving the risk of cold welding and tearing caused by directly bending and welding the first positive electrode tab and the second positive electrode tab in the traditional process.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, in particular to a lithium battery and a method for manufacturing the lithium battery. Background Art

[0002] As a new energy battery, lithium battery has the advantages of high operating voltage, high specific capacity, long charge and discharge life, and no memory effect. Lithium battery has gradually become the mainstream energy source of people's choice, so the demand for lithium battery is getting higher and higher; at the same time, the safety of lithium battery use has become more and more the focus of people's attention. The manufacturing direction of lithium battery is gradually tending towards high energy and high capacity, which makes the size and thickness of battery cells larger and larger.

[0003] At present, the battery cells that are put into square shells by the stacking process are widely used; most of the battery cells that are put into square shells by the existing stacking process adopt the method of outputting the pole ears at both ends, which makes the cover plate welded at both ends of the battery cell, and the stacking can only adopt the butterfly welding process at one end, and the other end adopts the traditional parallel stacking bending welding. If the number of stacking layers exceeds a certain order of magnitude, it will bring welding risks to the ultrasonic welding of the pole ears and the connecting pieces after parallel connection. The main manifestation is that there are too many pole ear layers. The super-thick pole ears make the direct ultrasonic welding bring the risk of cold welding, and the excessive number of pole ear layers after welding will also bring the risk of tearing. Summary of the invention

[0004] The technical problem to be solved by the present invention is how to avoid problems such as cold welding and tearing caused by bending and welding of an ultra-thick tab layer.

[0005] The present invention solves the above technical problems through the following technical means:

[0006] A lithium battery, comprising a parallel stacked core; the parallel stacked core comprises a first stacked core (7), a second stacked core (8), a first positive electrode connecting sheet (10), and a second positive electrode connecting sheet (11); a first negative electrode tab (42) of the first stacked core (7) and a second negative electrode tab (42') of the second stacked core (8) are arranged adjacent to each other; the first positive electrode tab (41) of the first stacked core (7) is fixedly connected to the first positive electrode connecting sheet (10), and the second positive electrode tab (41') of the second stacked core (8) is fixedly connected to the second positive electrode connecting sheet (11), the first positive electrode tab (41), the first positive electrode connecting sheet (10), the second positive electrode tab (41'), and the second positive electrode connecting sheet (11) are arranged in sequence; a corner of the first positive electrode connecting sheet (10) is extended away from the first stacked core (7) and fixed with a first auxiliary connecting sheet (12), and a corner of the second positive electrode connecting sheet (11) is extended away from the second stacked core (8) and fixed with a second auxiliary connecting sheet (12'), and the first auxiliary connecting sheet (12) and the second auxiliary connecting sheet (12') are fixed to each other.

[0007] Beneficial effect: Through the mutual cooperation of the first positive electrode connecting sheet, the first auxiliary connecting sheet, the second positive electrode connecting sheet and the second auxiliary connecting sheet, the first positive electrode ear and the second positive electrode ear can be connected together by fixing the first auxiliary connecting sheet and the second auxiliary connecting sheet, thereby solving the risk of cold welding and tearing caused by directly bending and welding the first positive electrode ear and the second positive electrode ear in the traditional process.

[0008] Furthermore, the first positive electrode connecting sheet (10) and the second positive electrode tab (41') are arranged in contact with each other.

[0009] Furthermore, it also includes a positive electrode cover plate (17), and the first auxiliary connecting piece (12) and the second auxiliary connecting piece (12') are fixed to each other after passing through two holes of the positive electrode cover plate (17).

[0010] Furthermore, it also includes a battery shell (16) and a negative electrode cover plate (15), wherein a closed space is formed between the battery shell (16), the negative electrode cover plate (15) and the positive electrode cover plate (17), and the parallel stacked cores are fixed in the closed space.

[0011] Furthermore, the parallel stacked core also includes a negative electrode connecting sheet (13), and the first negative electrode tab (42) of the first stacked core (7) is fixed to the second negative electrode tab (42') of the second stacked core (8) via the negative electrode connecting sheet (13); and the side of the negative electrode connecting sheet (13) away from the negative electrode tab is fixed to the negative electrode cover plate (15).

[0012] The present invention also discloses a method for manufacturing a lithium battery according to any of the above technical solutions, comprising the following steps:

[0013] S1: fixing the first negative electrode tab (42) of the first stacked core (7) to the second negative electrode tab (42') of the second stacked core (8) via the negative electrode connecting sheet (13); fixing the first positive electrode tab (41) of the first stacked core (7) to the first positive electrode connecting sheet (10), and fixing the second positive electrode tab (41') of the second stacked core (8) to the second positive electrode connecting sheet (11); a first auxiliary connecting sheet (12) is extended and fixed to one corner of the first positive electrode connecting sheet (10), and a second auxiliary connecting sheet (12') is extended and fixed to one corner of the second positive electrode connecting sheet (11), and the first auxiliary connecting sheet (12) and the second auxiliary connecting sheet (12') are arranged in a mirror-image folded arrangement;

[0014] S2 folds the negative electrode connecting sheet (13) so that the first core stack (7) and the second core stack (8) are arranged in parallel;

[0015] S3: folding the first positive electrode connecting sheet (10), the first positive electrode ear (41) and the second positive electrode connecting sheet (11), the second positive electrode ear (41') at the positive end of the parallel stacked core toward each other; at this time, the auxiliary connecting sheets on the first positive electrode connecting sheet (10) and the second positive electrode connecting sheet (11) are arranged parallel to the top plane of the parallel stacked core;

[0016] S4: fold the first auxiliary connecting piece (12) and the second auxiliary connecting piece (12') towards each other and fix them.

[0017] Beneficial effect: Through the mutual cooperation of the first positive electrode connecting sheet, the first auxiliary connecting sheet, the second positive electrode connecting sheet and the second auxiliary connecting sheet, the first positive electrode ear and the second positive electrode ear can be connected together by fixing the first auxiliary connecting sheet and the second auxiliary connecting sheet, thereby solving the risk of cold welding and tearing caused by directly bending and welding the first positive electrode ear and the second positive electrode ear in the traditional process; the lithium battery manufacturing method provided by the present application can prepare a lithium battery with a thickness greater than 30 mm.

[0018] Furthermore, the method for manufacturing the stacked core comprises the following steps:

[0019] S1 After rolling, the positive electrode sheet is cut from the middle foil area (1) and the effective dressing area (3) to form a plurality of positive electrode sheets; the operation process of the negative electrode sheet is the same as that of the positive electrode sheet;

[0020] S2 takes a positive electrode sheet in S1, cuts the foil area (2) at the edge of the electrode sheet, and forms a plurality of discontinuous foil areas, which are the positive electrode tabs (4); similarly, a plurality of negative electrode tabs (4') are formed on the negative electrode sheet;

[0021] S3 cuts the effective dressing area (3) of the positive and negative electrode sheets respectively, wherein the slicing direction is consistent with the length direction of the electrode ear, and the electrode sheet is cut into a certain width according to a certain width size to form a plurality of unit sheets;

[0022] S4: alternately stacking the negative unit sheets (6) and the positive unit sheets (5) to form a stacked core, wherein the stacking method is that the positive electrode tabs (4) are all distributed on one side of the stacked core, and the negative electrode tabs (4') are all distributed on the other side of the stacked core;

[0023] S5 fixes the positive electrode tabs (4) on one side of the stacked core together, and fixes the negative electrode tabs (4') on the other side of the stacked core together.

[0024] Furthermore, the first negative electrode tab (42) of the first stacked core (7) is firstly connected to the second negative electrode tab (42') of the second stacked core (8) via a rubber strip (9), and then the first negative electrode tab (42) and the second negative electrode tab (42') are ultrasonically welded to the two sides of the same negative electrode connecting sheet (13), and the weld marks do not overlap.

[0025] Furthermore, when the pole ear is welded to the connecting piece, the pole ear is located above the connecting piece.

[0026] Furthermore, the first auxiliary connecting piece (12) and the second auxiliary connecting piece (12') are passed through the two holes of the positive electrode cover plate (17) and then folded towards each other for fixation.

[0027] The advantages of the present invention are:

[0028] The present invention, through the mutual cooperation of the first positive electrode connecting sheet, the first auxiliary connecting sheet, the second positive electrode connecting sheet, and the second auxiliary connecting sheet, can connect the first positive electrode ear and the second positive electrode ear together by fixing the first auxiliary connecting sheet and the second auxiliary connecting sheet, thereby solving the risk of cold welding and tearing caused by directly bending and welding the first positive electrode ear and the second positive electrode ear in the traditional process; the lithium battery manufacturing method provided by the present application can prepare a lithium battery with a thickness greater than 30 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A top view of the positive electrode sheet in step 1 of the lithium battery manufacturing method according to embodiment 2 of the present invention;

[0030] Figure 2 A top view of the electrode sheet in step 2 of the lithium battery manufacturing method according to the second embodiment of the present invention;

[0031] Figure 3 It is a top view of the electrode sheet after being cut in step 3 of the lithium battery manufacturing method of the second embodiment of the present invention;

[0032] Figure 4 It is a front view of the stacked core in step 4 of the lithium battery manufacturing method of embodiment 2 of the present invention;

[0033] Figure 5 A top view of the stacked core in step 4 of the lithium battery manufacturing method according to embodiment 2 of the present invention;

[0034] Figure 6 It is a front view of the stacked core in step 5 of the lithium battery manufacturing method of embodiment 2 of the present invention;

[0035] Figure 7 A top view of the stacked core in step 5 of the lithium battery manufacturing method according to the second embodiment of the present invention;

[0036] Figure 8 It is a front view of the double-stacked core in step 6 of the lithium battery manufacturing method of embodiment 2 of the present invention;

[0037] Fig. 9 A top view of the double-stacked core in step 6 of the lithium battery manufacturing method of Example 2 of the present invention;

[0038] Fig.10A three-dimensional diagram of the first positive electrode connecting piece in step 6 of the lithium battery manufacturing method according to the second embodiment of the present invention;

[0039] Fig.11 A three-dimensional diagram of the second positive electrode connecting piece in step 6 of the lithium battery manufacturing method according to the second embodiment of the present invention;

[0040] Fig.12 A top view of the double-stacked core in step 7 of the lithium battery manufacturing method of Example 2 of the present invention;

[0041] Fig.13 It is a front view of the parallel stacked cores in step 7 of the lithium battery manufacturing method of embodiment 2 of the present invention;

[0042] Fig.14 A top view of the parallel stacked cores in step 7 of the lithium battery manufacturing method according to the second embodiment of the present invention;

[0043] Fig.15 A top view of the parallel stacked cores in step 8 of the lithium battery manufacturing method according to the second embodiment of the present invention;

[0044] Fig.16 It is a front view of the parallel stacked cores in step 8 of the lithium battery manufacturing method of embodiment 2 of the present invention;

[0045] Fig.17 for Fig.16 A magnified view of middle;

[0046] Fig.18 This is a front view of the battery shell after the parallel stacking of the cores in step 8 of the lithium battery manufacturing method of the second embodiment of the present invention;

[0047] Fig.19 It is a top view of the battery shell assembled by parallel stacking the cores in step 8 of the lithium battery manufacturing method of the second embodiment of the present invention;

[0048] Fig. 20 This is a front view of the positive electrode cover plate after the parallel stacking of the cores is assembled in step 9 of the lithium battery manufacturing method according to the second embodiment of the present invention;

[0049] Fig.21 for Fig. 20 Enlarged view of middle B;

[0050] Fig. 22 It is a top view of the positive electrode cover plate after the parallel stacking of the cores is assembled in step 9 of the lithium battery manufacturing method of the second embodiment of the present invention;

[0051] Fig.23 It is a right side view of the positive electrode cover plate after the parallel stacking of the cores is assembled in step 9 of the lithium battery manufacturing method of the second embodiment of the present invention;

[0052] Fig.24 It is a front view of the auxiliary connecting sheet after being bent in step 10 of the lithium battery manufacturing method of the second embodiment of the present invention;

[0053] Fig.25 for Fig.24 Enlarged view of middle C;

[0054] Fig.26 It is a top view of the auxiliary connecting sheet after being bent in step 10 of the lithium battery manufacturing method of the second embodiment of the present invention;

[0055] Fig. 27 This is a three-dimensional diagram of the auxiliary connecting sheet after being bent in step 10 of the lithium battery manufacturing method of the second embodiment of the present invention;

[0056] Fig.28 It is a front view of the positive electrode column pressing plate after welding in step 10 of the lithium battery manufacturing method of the second embodiment of the present invention;

[0057] Fig.29 for Fig.28 Enlarged view of middle D;

[0058] Fig.30 This is a right view of the positive electrode column pressing plate after welding in step 10 of the lithium battery manufacturing method of embodiment 2 of the present invention. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0060] Embodiment 1

[0061] like Fig. 27 , 28 As shown, this embodiment provides a lithium battery, including a battery shell 16, a negative electrode cover plate 15, a positive electrode cover plate 17, and a parallel stacked core; a closed space is formed between the battery shell 16, the negative electrode cover plate 15, and the positive electrode cover plate 17, and the parallel stacked core is fixed in the closed space;

[0062] like Fig.12 , 13 As shown, the parallel stack core includes a first stack core 7, a second stack core 8, a negative electrode connecting sheet 13, a first positive electrode connecting sheet 10, and a second positive electrode connecting sheet 11; the first negative electrode tab 42 of the first stack core 7 is fixed to the second negative electrode tab 42' of the second stack core 8 through the negative electrode connecting sheet 13; the side of the negative electrode connecting sheet 13 away from the negative electrode tab is fixed to the negative electrode cover plate 15;

[0063] like Fig.29As shown, the first positive electrode tab 41 of the first stacked core 7 is fixedly connected to the first positive electrode connecting sheet 10, and the second positive electrode tab 41' of the second stacked core 8 is fixedly connected to the second positive electrode connecting sheet 11. The first positive electrode tab 41, the first positive electrode connecting sheet 10, the second positive electrode tab 41' and the second positive electrode connecting sheet 11 are arranged in sequence, and the first positive electrode connecting sheet 10 and the second positive electrode tab 41' are arranged in contact with each other; a corner of the first positive electrode connecting sheet 10 extends to the right to fix a first auxiliary connecting sheet 12, and a corner of the second positive electrode connecting sheet 11 extends to the right to fix a second auxiliary connecting sheet 12', and the first auxiliary connecting sheet 12 and the second auxiliary connecting sheet 12' pass through two square holes of the positive cover plate 17 and are fixed to each other.

[0064] Through the mutual cooperation of the first positive electrode connecting sheet 10, the first auxiliary connecting sheet 12, the second positive electrode connecting sheet 11, and the second auxiliary connecting sheet 12', the first positive electrode tab 41 and the second positive electrode tab 41' can be connected together by fixing the first auxiliary connecting sheet 12 and the second auxiliary connecting sheet 12', thereby solving the risks of cold welding and tearing caused by directly bending and welding the first positive electrode tab 41 and the second positive electrode tab 41' in the traditional process. The lithium battery manufacturing method provided in the present application can prepare a lithium battery with a thickness greater than 30 mm.

[0065] Embodiment 2

[0066] The method for manufacturing the lithium battery of Example 1 comprises the following steps:

[0067] S1, rolling and slitting: Figure 1 As shown, taking the positive electrode sheet as an example, the positive electrode sheet includes a middle foil area 1, two side edge foil areas 2 and a dressing effective area 3, and the two sides of the middle foil area 1 are the dressing effective area 3; the length of the middle foil area 1 is twice the length of the two side edge foil areas 2; the negative electrode sheet has the same structure as the positive electrode sheet; as shown Figure 1 As shown, after rolling, the positive electrode sheet is cut into two from the center of the middle foil area 1, and then cut from the center of the dressing effective area 3 to form four positive divided electrode sheets; the operation process of the negative electrode sheet is the same as that of the positive electrode sheet.

[0068] S2, Tab Forming: Figure 1 , Figure 2 As shown, one of the positive pole sheets is taken, and the foil area 2 at the edge of the pole sheet is laser cut to form a number of discontinuous foil areas, which are the positive pole ears 4 of the positive pole sheet; similarly, a number of negative pole ears (not shown) are formed on the negative pole sheet; the spacing between two adjacent pole ears on the positive and negative pole sheets is equal, all positive pole ears 4 have equal upper and lower widths, and all negative pole ears (not shown) have equal upper and lower widths.

[0069] S3, Production: Figure 3As shown, the effective dressing area 3 of the positive and negative polarizer sheets is laser cut or die cut respectively, and the slicing direction is consistent with the length direction of the pole ear. The pole sheet is cut into a certain width according to a certain width size to form a number of unit sheets; this embodiment takes the positive polarizer sheet as an example, and cuts it into four positive unit sheets 5.

[0070] S4, lamination: Figure 3 , Figure 4 , Figure 5 As shown, the negative unit sheet 6 is placed on the bottom layer, the positive unit sheet 5 is placed on the negative unit sheet 6, a layer of diaphragm is arranged between the positive and negative unit sheets, the positive and negative electrode ears are facing opposite directions, and are stacked in sequence to the top layer of the negative unit sheet 6 to form a stacked core; the stacking method is that the positive electrode ears 4 are all distributed on one side of the stacked core, and the negative electrode ears 4' are all distributed on the other side of the stacked core; after the unit sheets are stacked, the positive and negative electrode ears meet the requirement of completely overlapping each other, and the number of unit sheet stacking layers: positive electrode>40 layers, negative electrode>41 layers.

[0071] S5, welding tabs: Figure 6 , Figure 7 As shown, the positive electrode tabs 4 are ultrasonically welded together, and the negative electrode tabs 4' are ultrasonically welded together.

[0072] S6, welding connecting piece: Figure 8 , Fig. 9 As shown, the first negative electrode tab 42 of the first stacked core 7 is butted with the second negative electrode tab 42' of the second stacked core 8 through the rubber strip 9 to form a double stacked core; the first positive electrode tab 41 of the first stacked core 7 is ultrasonically welded to the first positive electrode connecting sheet 10, and the second positive electrode tab 41' of the second stacked core 8 is ultrasonically welded to the second positive electrode connecting sheet 11; Figure 8 As shown, the orthographic projection of the first positive electrode connecting sheet 10 is an inverted L shape, and the second positive electrode connecting sheet 11 and the first positive electrode connecting sheet 10 are arranged in a mirror image, as shown in FIG. Fig.10 , 11 As shown, the specific operation is: a first auxiliary connecting piece 12 is extended and fixed to one corner of the first positive connecting piece 10, and a second auxiliary connecting piece 12' is extended and fixed to one corner of the second positive connecting piece 11. The first auxiliary connecting piece 12 and the second auxiliary connecting piece 12' are first bent in a mirror-image direction, and the bending position is the root of the auxiliary connecting piece, and the bending angle is 90°; Fig.12 As shown, the first negative electrode tab 42 and the second negative electrode tab 42' are ultrasonically welded to the two sides of the same negative electrode connecting sheet 13, and the weld marks do not overlap; when the positive and negative tabs are welded, the tabs and the connecting sheet are placed in the following positions: the tabs are located above the connecting sheet.

[0073] S7, parallel assembly of stacked cores and laser welding of negative electrode cover: Fig.12 , 13As shown in FIG. 14 , after welding, the negative electrode connecting sheet 13 is folded from the center so that the first core stack 7 and the second core stack 8 are arranged in parallel and fixed by an adhesive tape 14 ; then the negative electrode connecting sheet 13 and the negative electrode cover plate 15 are laser welded.

[0074] S8, bending and shelling of positive electrode connecting piece: Fig.15 , 16 As shown in FIG. 17 , the first positive electrode connecting sheet 10 and the first positive electrode ear 41 of the positive terminal of the parallel stacked core are folded downward, and then the second positive electrode connecting sheet 11 and the second positive electrode ear 41 'are folded upward; at this time, the auxiliary connecting sheet on the first positive electrode connecting sheet 10 and the second positive electrode connecting sheet 11 is arranged parallel to the top plane of the parallel stacked core; as shown in FIG. Fig.18 , 19 As shown, the parallel stacked cores are placed as a whole into the battery shell 16 to complete the matching between the negative electrode cover plate 15 and one end of the battery shell 16 .

[0075] S9, positive electrode cover assembly and welding: Fig. 20 , 21 As shown in , 22 and 23, the vertically bent auxiliary connecting piece is passed through the two square holes of the positive electrode cover plate 17 to complete the matching of the positive electrode cover plate 17 and the other end of the battery shell 16.

[0076] S10, battery forming: welding the positive and negative electrode covers to the periphery of the shell, such as Fig.24 , 25 As shown in , 26, and 27, the auxiliary connecting piece is bent for the second time, and the bent auxiliary connecting piece is fixed by ultrasonic welding; the second bending direction of the first auxiliary connecting piece 12 and the second auxiliary connecting piece 12' is folded toward each other, the bending position is the middle position of the auxiliary connecting piece, and the bending angle is 90°; Fig.28 , 29 As shown in 30, the positive electrode column pressing plate 18 is finally laser welded to form a lithium battery.

[0077] The thickness of the lithium battery is greater than 30 mm.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lithium battery, characterized in that: Including parallel stacked cores; The parallel stacked core comprises a first stacked core (7), a second stacked core (8), a first positive electrode connecting sheet (10), a second positive electrode connecting sheet (11), a negative electrode connecting sheet (13), and a positive electrode cover plate (17); The first negative electrode tab (42) of the first stacked core (7) and the second negative electrode tab (42') of the second stacked core (8) are arranged adjacent to each other, and the first negative electrode tab (42) of the first stacked core (7) is fixed to the second negative electrode tab (42') of the second stacked core (8) via a negative electrode connecting sheet (13); the first positive electrode tab (41) of the first stacked core (7) is fixedly connected to the first positive electrode connecting sheet (10), and the second positive electrode tab (41') of the second stacked core (8) is fixedly connected to the second positive electrode connecting sheet (11); the first positive electrode tab (41), the first positive electrode connecting sheet (10), the second positive electrode tab (41'), and the second positive electrode connecting sheet (11) are arranged in sequence; A first auxiliary connecting piece (12) is fixedly provided at one corner of the first positive connecting piece (10) and extending away from the first stacked core (7); a second auxiliary connecting piece (12') is fixedly provided at one corner of the second positive connecting piece (11) and extending away from the second stacked core (8); the first auxiliary connecting piece (12) and the second auxiliary connecting piece (12') are fixed to each other; the first positive connecting piece (10) and the second positive electrode tab (41') are arranged in contact with each other; the first auxiliary connecting piece (12) and the second auxiliary connecting piece (12') are fixed to each other after passing through two holes of the positive electrode cover plate (17); and the negative electrode connecting piece (13) is located on opposite sides to the first positive connecting piece (10) and the second positive connecting piece (11).

2. A lithium battery according to claim 1, characterized in that: It also includes a battery shell (16) and a negative electrode cover plate (15). A closed space is formed between the battery shell (16), the negative electrode cover plate (15) and the positive electrode cover plate (17), and the parallel stacked cores are fixed in the closed space.

3. A lithium battery according to claim 2, characterized in that: The side of the negative electrode connecting sheet (13) away from the negative electrode ear is fixed to the negative electrode cover plate (15).

4. A method for manufacturing a lithium battery according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1: fixing the first negative electrode tab (42) of the first stacked core (7) to the second negative electrode tab (42') of the second stacked core (8) via the negative electrode connecting sheet (13); fixing the first positive electrode tab (41) of the first stacked core (7) to the first positive electrode connecting sheet (10), and fixing the second positive electrode tab (41') of the second stacked core (8) to the second positive electrode connecting sheet (11); a first auxiliary connecting sheet (12) is extended and fixed to one corner of the first positive electrode connecting sheet (10), and a second auxiliary connecting sheet (12') is extended and fixed to one corner of the second positive electrode connecting sheet (11), and the first auxiliary connecting sheet (12) and the second auxiliary connecting sheet (12') are arranged in a mirror-image folded arrangement; S2 folds the negative electrode connecting sheet (13) so that the first core stack (7) and the second core stack (8) are arranged in parallel; S3: folding the first positive electrode connecting sheet (10), the first positive electrode ear (41) and the second positive electrode connecting sheet (11), the second positive electrode ear (41') at the positive end of the parallel stacked core toward each other; at this time, the auxiliary connecting sheets on the first positive electrode connecting sheet (10) and the second positive electrode connecting sheet (11) are arranged parallel to the top plane of the parallel stacked core; S4: fold the first auxiliary connecting piece (12) and the second auxiliary connecting piece (12') towards each other and fix them.

5. The method for manufacturing a lithium battery according to claim 4, characterized in that: The method for manufacturing the stacked core comprises the following steps: S1 After rolling, the positive electrode sheet is cut from the middle foil area (1) and the effective dressing area (3) to form a plurality of positive electrode sheets; the operation process of the negative electrode sheet is the same as that of the positive electrode sheet; S2 takes a positive electrode sheet in S1, cuts the foil area (2) at the edge of the electrode sheet, and forms a plurality of discontinuous foil areas, which are the positive electrode tabs (4); similarly, a plurality of negative electrode tabs (4') are formed on the negative electrode sheet; S3 cuts the effective dressing area (3) of the positive and negative electrode sheets respectively, the slicing direction is consistent with the length direction of the electrode ear, and the electrode sheet is cut into a certain width according to a certain width size to form a plurality of unit sheets; S4: alternately stacking the negative unit sheets (6) and the positive unit sheets (5) to form a stacked core, wherein the stacking method is that the positive electrode tabs (4) are all distributed on one side of the stacked core, and the negative electrode tabs (4') are all distributed on the other side of the stacked core; S5 fixes the positive electrode tabs (4) on one side of the stacked core together, and fixes the negative electrode tabs (4') on the other side of the stacked core together.

6. The method for manufacturing a lithium battery according to claim 4, characterized in that: The first negative electrode tab (42) of the first stacked core (7) is firstly connected to the second negative electrode tab (42') of the second stacked core (8) via a rubber strip (9), and then the first negative electrode tab (42) and the second negative electrode tab (42') are ultrasonically welded to the two sides of the same negative electrode connecting sheet (13), and the weld marks do not overlap.

7. The method for manufacturing a lithium battery according to claim 4, characterized in that: When the pole ear is welded to the connecting piece, the pole ear is located above the connecting piece.

8. The method for manufacturing a lithium battery according to claim 4, characterized in that: The first auxiliary connecting piece (12) and the second auxiliary connecting piece (12') are passed through two holes of the positive electrode cover plate (17) and then folded towards each other for fixation.

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