Cylindrical battery and battery module

Abstract

The cylindrical battery comprises a shell, a battery cell located in the shell, and a positive pole lug and a negative pole lug which are located at the two ends of the battery cell, the battery cell comprises a wound positive pole piece, a diaphragm and a negative pole piece, the negative pole piece comprises a load section and an empty foil section, the load section comprises a negative current collector and an active material layer attached to the negative current collector, and the empty foil section comprises a positive electrode and a negative electrode. The empty foil section comprises a negative current collector which is positioned on the outermost layer of the battery cell to form an outer side layer of the battery cell, and the conductivity of the negative current collector of the empty foil section is superior to that of the shell. The cylindrical battery can effectively reduce the battery impedance. The utility model further discloses a battery module comprising the cylindrical battery.

Description

Technical Field

[0001] The utility model relates to the field of cylindrical batteries, in particular to the field of battery cells. Background Art

[0002] At present, cylindrical batteries generally include a battery cell, a shell, a positive electrode and a negative electrode. The positive and negative electrodes are respectively arranged at the two ends of the shell, and multiple battery cells are connected through positive and negative electrode tabs. The welding points and explosion-proof valves are respectively arranged at the two ends to achieve thermal and electrical separation.

[0003] The negative electrode of the battery is generally set at the bottom of the battery and needs to be welded to the collector plate. The positive electrode is set at the top of the battery and is electrically connected to the outside world through the pole. The outer shell of the cylindrical battery wraps the battery cell. When the battery is working and discharging, the current will pass through the entire stainless steel battery tube shell, thereby increasing the impedance and heat generation of the battery, reducing the operating voltage of the battery, and affecting the fast charging performance of the battery. Utility Model Content

[0004] One purpose of the utility model is to provide a cylindrical battery which can effectively reduce the battery impedance.

[0005] A cylindrical battery for achieving the above-mentioned purpose comprises a shell, a battery cell located in the shell, and a positive electrode tab and a negative electrode tab located at both ends of the battery cell, the battery cell comprises a wound positive electrode sheet, a separator and a negative electrode sheet, the negative electrode sheet comprises a load section and an empty foil section, the load section comprises a negative electrode collector and an active material layer attached to the negative electrode collector, the empty foil section comprises a negative electrode collector, the empty foil section is located on the outer layer of the battery cell to form the outer layer of the battery cell, and the negative electrode collector of the empty foil section has better conductivity than the shell.

[0006] In one or more embodiments, the negative electrode plate further includes a blank area, and the blank area is used to form the negative electrode tab.

[0007] In one or more embodiments, the ends of the load segment and the empty foil segment both include the blank area to form a load segment pole ear and an empty foil segment pole ear respectively, and the load segment pole ear and the empty foil segment pole ear together form a negative electrode welding surface.

[0008] In one or more embodiments, the blank area includes a plurality of cut-out areas, and the plurality of cut-out areas form the negative electrode tab.

[0009] In one or more embodiments, the cylindrical battery further includes a negative electrode current collector disk, the negative electrode welding surface is electrically connected to the negative electrode current collector disk, and the negative electrode current collector disk is also electrically connected to the outer shell.

[0010] In one or more embodiments, the end boundary of the load segment after winding exceeds the end boundary of the positive electrode sheet, and the exceeding portion forms a first excess coating area.

[0011] In one or more embodiments, the end boundary of the diaphragm exceeds the end boundary of the load section, and the exceeding portion forms a second excess coating region.

[0012] In one or more embodiments, the empty foil segment wraps around the load segment at least once, and an end of the empty foil segment exceeds the load segment, and the exceeding portion forms a third excess wrapping area.

[0013] In one or more embodiments, the negative electrode current collector is copper foil, and the outer shell is a stainless steel shell.

[0014] Another object of the present invention is to provide a battery module comprising a plurality of the above cylindrical batteries.

[0015] The above-mentioned cylindrical battery uses the empty foil segment of the negative electrode plate to form the outer layer of the battery cell, and the conductivity of the negative electrode collector is better than that of the outer shell. Therefore, although the negative electrode welding surface is welded to the outer shell, the current preferentially flows to the side of the material with better conductivity, so that the current preferentially flows to the positive electrode through the negative electrode collector of the empty foil segment. Compared with the traditional current flow, the battery impedance is effectively reduced under the premise of thermal and electrical separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other features, properties and advantages of the present invention will become more apparent through the following description in conjunction with the accompanying drawings and embodiments, in which:

[0017] Figure 1 is an expanded view of an embodiment of a negative electrode plate;

[0018] Figure 2 is an expanded view of an embodiment of a negative electrode sheet with a negative electrode tab;

[0019] Figure 3 is a schematic diagram of an embodiment of a negative electrode tab;

[0020] Figure 4 This is a top view of the negative electrode ear after flattening;

[0021] Figure 5 It is a schematic diagram of the cross section of the battery cell after winding;

[0022] Figure 6 It is a schematic diagram of the ends of the negative electrode sheet, the separator and the positive electrode sheet;

[0023] Figure 7 It is a longitudinal cross-sectional view of the battery;

[0024] Figure 8 yes Figure 7 Enlarged view of point E in the middle. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with specific embodiments and drawings. More details are elaborated in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in a variety of other ways different from the description. Those skilled in the art can make similar generalizations and deductions based on actual application situations without violating the connotation of the present invention. Therefore, the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0026] It should be noted that these and other subsequent drawings are only examples and are not drawn in proportion, and should not be used as a limitation on the actual scope of protection required by the present utility model.

[0027] The cylindrical battery disclosed in the present invention is Figure 7 As shown, the battery cell 20 includes a housing 10, a positive electrode tab 234 and a negative electrode tab 235 at both ends of the battery cell, and a pole 40 electrically connected to the positive electrode tab 234. Figure 5 As shown, it includes a wound positive electrode sheet 21, a separator 22 and a negative electrode sheet 23, and an electrolyte is provided between the positive electrode sheet 21 and the negative electrode sheet 23. The positive electrode sheet 21 and the negative electrode sheet 23 are separated by the separator 22 and wound around the center to form a battery cell 20.

[0028] Among them, the negative electrode plate 23 is as follows Figures 1 to 3 As shown, it includes a load segment 231 and an empty foil segment 232, and the boundary line between the two is shown as line G.

[0029] The load segment 231 includes a negative electrode current collector and an active material layer attached to the negative electrode current collector, wherein the active material layer includes active materials, a binder, etc., and the negative electrode active material includes graphite. The empty foil segment 232 includes only the negative electrode current collector without other materials attached thereto, that is, the empty foil segment 232 is a whole empty foil wrapped around the outer ring of the battery cell without coating. Thus, the empty foil segment 232 is used as a wrapping redundant area to form the outer layer of the battery cell 23, such as Figure 5 and Figure 8 As shown, the conductivity of the negative electrode current collector of the empty foil segment 232 is set to be better than the conductivity of the outer shell 10, and the conductivity is generally measured by the conductivity σ. In this way, when the battery is working, the current can pass through the empty foil segment 232 of the outer ring of the battery cell, that is, directly through the negative electrode current collector to reach the positive electrode side of the battery without being conducted through the outer shell 10, thereby effectively reducing the battery impedance.

[0030] In some embodiments, the negative electrode current collector is copper foil, and the outer shell 10 is a stainless steel shell. Compared with the stainless steel material, the current flowing through the copper foil can also achieve rapid heat dissipation.

[0031] like Figure 6As shown, in some embodiments, the end boundary of the load segment 231 after winding exceeds the end boundary of the positive electrode sheet 21, and the portion exceeding the end boundary forms a first excess coating area A, and the length range of the first excess area A is preferably 5 to 100 mm. The end boundary of the diaphragm 22 after winding exceeds the end boundary of the load segment 231, and the portion exceeding the end boundary forms a second excess coating area B, and the length range of the second excess coating area B is preferably 5 to 100 mm. However, the boundary of the diaphragm 22 after winding does not exceed the boundary of the empty foil segment 232, and the empty foil segment 232 after winding forms the outermost circle of the battery cell 23, or multiple circles located in the outermost layer.

[0032] The empty foil segment 232 wraps around the load segment 231 of the negative electrode plate 23 by at least one circle, and the end of the empty foil segment 232 exceeds the load segment 231 , and the excess portion forms a third excess wrapping area C. Figure 6 In the illustrated embodiment, the empty foil segment 232 extends beyond the load segment 231 by one full circle, and may also wrap more circles, such as two circles. The empty foil segment 232 preferably wraps the load segment 231 as long as possible.

[0033] Continue to refer to Figure 3 and Figure 4 As shown, the negative electrode sheet 23 also includes blank areas 233 at both ends in the width direction, and the blank areas 233 are used to form negative electrode tabs 235. The blank area 233 refers to the uncoated foil at the edge of the electrode sheet. In some embodiments, a plurality of cutting areas are formed in the blank area 233 by laser cutting or mechanical die cutting, such as Figure 4 The trapezoidal shape shown in the figure may also be a chamfered parallelogram, a quadrilateral perpendicular to the electrode piece, etc., and the negative electrode tab 235 may be formed by a flattening process. In other embodiments, the entire blank area 233 may be used as the negative electrode tab 235 without cutting, such as Figure 1 shown.

[0034] In some embodiments, the negative electrode tab 235 may be formed only in the load segment 231, or the ends of the load segment 231 and the empty foil segment 232 may include a blank area 233 to form a load segment tab 2351 and an empty foil segment tab 2352, respectively, and the load segment tab 2351 and the empty foil segment tab 2352 together form a Figure 4 The negative electrode tab shown is used as the negative electrode welding surface.

[0035] The negative electrode tab 235 is formed by a flattening process when the negative electrode welding plane is formed by the blank area, and is formed by a flattening process when the negative electrode welding plane is formed by the cut part.

[0036] The cylindrical battery also includes a negative electrode collector plate located on one side of the negative electrode welding plane. The negative electrode welding surface and the negative electrode collector plate are welded by methods such as laser spot welding. The negative electrode collector plate is also welded to the battery shell by methods such as ultrasonic torque welding or laser welding.

[0037] The battery assembly process using the above structure includes the following steps.

[0038] First, the negative electrode tab 235 is formed in the blank area 233 of the negative electrode sheet 23 by laser cutting or mechanical die cutting. Subsequently, the positive electrode sheet 21 and the negative electrode sheet 23 are separated by the diaphragm 22 and wound around the center to form a battery cell 23. The empty foil segment 232 serves as a redundant coating area to become the outermost structure of the battery cell 8, or the traditional "battery cell" part. Subsequently, the blank area 233 of the load segment 231 and the empty foil segment 232 is flattened and pressed to form a negative electrode welding surface. Finally, the negative electrode collector plate is connected to the negative electrode welding plane by laser spot welding, and the negative electrode collector plate is connected to the battery casing by ultrasonic torque welding or laser welding to complete the processing of the battery negative electrode.

[0039] In this way, by setting an empty foil segment at the tail of the negative electrode sheet and using a suitable laser die-cutting process, the copper foil of the wound battery cell is used as the outer layer. After the negative electrode side is flattened, the outer empty foil segment is used as the outermost side of the entire negative terminal surface. Since the entire negative terminal surface is a conductive surface, the outermost side of the negative terminal surface is set as the area of ​​the empty foil segment. The electrons in the negative electrode inside the battery tend to flow to the end face of the negative electrode ear at the top along the up and down direction of the battery first, and flow to the empty foil segment with the help of the overall conductive characteristics of the negative terminal surface. Compared with the traditional electrons being transferred laterally to the outer shell in the radial direction, the above method makes the current tend to flow through the empty foil segment with better conductivity to reach the positive electrode of the battery, which will significantly shorten the time for electrons to be transferred to the outer shell, and the distance for the electrons in the negative electrode inside the battery to flow to the outer shell is shortened and becomes closer, achieving thermal and electrical separation while reducing the impedance of the battery.

[0040] The following is a comparison through two embodiments.

[0041] The shell of the traditional cylindrical battery is made of stainless steel, with a diameter of 46 mm and a height of 95 mm. The positive electrode is made of nickel-cobalt-manganese ternary material, and the negative electrode is artificial graphite doped with silicon dioxide. The nominal capacity is 32 Ah and the nominal voltage is 3.65 V. Its assembly process is as follows: (1) The negative electrode plate is continuously coated without setting a blank foil section, and the terminal tab is formed in the blank area at the end by laser cutting; (2) The negative electrode plate and the positive electrode plate are separated by a diaphragm and wound around the center to form a battery cell, so that the negative electrode covers the positive electrode and the diaphragm covers the negative electrode plate, and the outer side of the diaphragm is fixed with a termination tape; (3) The blank area of ​​the negative electrode plate is flattened to form a negative electrode welding plane; (4) The negative electrode collector plate and the negative electrode welding plane are connected by laser spot welding; (5) The negative electrode collector plate and the battery shell are connected by ultrasonic torque welding or laser welding.

[0042] The cylindrical battery disclosed in the present invention has a stainless steel shell, a diameter of 46 mm, a height of 95 mm, a positive electrode of nickel-cobalt-manganese ternary material, a negative electrode of artificial graphite doped with silicon dioxide, a nominal capacity of 32 Ah, and a nominal voltage of 3.65 V. The assembly process is as follows: (1) The negative electrode sheet is coated at a gap, and an empty foil segment is set at the tail. The lengths of the empty foil segments are 140 mm, 280 mm, 420 mm, and 560 mm, respectively. Laser cutting is used to form the pole ear in the blank area; (2) The negative electrode sheet and the positive electrode sheet are separated by a diaphragm and wound around the center to form a battery cell, so that the negative electrode empty foil segment wraps the battery cell. According to the different lengths of the empty foil segments, the wrapping redundancy is 5 mm, 145 mm, 285 mm, and 425 mm, respectively, and the outside is fixed with a termination tape; (3) The blank area of ​​the negative electrode sheet is provided with multiple trapezoidal cutting areas, and the cutting areas are flattened to form a negative electrode welding plane as the negative electrode ear; (4) The negative electrode collector and the negative electrode welding plane are connected by laser spot welding; (5) The negative electrode collector and the battery casing are connected by ultrasonic torque welding or laser welding.

[0043] The test results of traditional cylindrical batteries and the cylindrical batteries described in the present disclosure are shown in the following table, where Group A is traditional cylindrical batteries, Group B is the cylindrical batteries described in the present disclosure, and different Groups B represent embodiments with different empty foil segment lengths.

[0044]

[0045] The above data show that the cylindrical battery disclosed in the present invention has a significant decrease in DCIR (Direct Current Internal Resistance), with an average decrease of 12.7%, and the median voltage during discharge increased by about 0.01V, significantly reducing the battery impedance.

[0046] Combined with the introduction of the above cylindrical batteries, it can also be understood that a battery module including a plurality of the above cylindrical batteries has better discharge performance.

[0047] The present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or multiple times in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0048] Although the utility model is disclosed as above with preferred embodiments, it is not intended to limit the utility model. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the utility model. Therefore, any modification, equivalent change and modification made to the above embodiments based on the technical essence of the utility model without departing from the content of the technical solution of the utility model shall fall within the protection scope defined by the claims of the utility model.

Claims

1. A cylindrical battery, comprising a housing, a battery cell in the housing, and a positive electrode tab and a negative electrode tab at both ends of the battery cell, wherein the battery cell comprises a wound positive electrode sheet, a separator and a negative electrode sheet, characterized in that: The negative electrode sheet includes a load segment and an empty foil segment, the load segment includes a negative electrode current collector and an active material layer attached to the negative electrode current collector, the empty foil segment includes a negative electrode current collector, the empty foil segment is located on the outer layer of the battery cell, and the negative electrode current collector of the empty foil segment has better conductivity than the shell.

2. The cylindrical battery according to claim 1, characterized in that: The negative electrode plate also includes a blank area, and the blank area is used to form the negative electrode tab.

3. The cylindrical battery according to claim 2, characterized in that: The ends of the load segment and the empty foil segment both include the blank area to form a load segment pole ear and an empty foil segment pole ear respectively, and the load segment pole ear and the empty foil segment pole ear jointly form a negative electrode welding surface.

4. The cylindrical battery according to claim 2, characterized in that: The blank area includes a plurality of cutting areas, and the plurality of cutting areas form the negative electrode tab.

5. The cylindrical battery according to claim 3, characterized in that: The cylindrical battery also includes a negative electrode current collecting disk, the negative electrode welding surface is electrically connected to the negative electrode current collecting disk, and the negative electrode current collecting disk is also electrically connected to the shell.

6. The cylindrical battery according to claim 1, characterized in that: The end boundary of the load segment after winding exceeds the end boundary of the positive electrode plate, and the exceeding portion forms a first excess coating area.

7. The cylindrical battery according to claim 1, characterized in that: The end edge of the diaphragm exceeds the end edge of the load section, and the exceeding portion forms a second excess coating area.

8. The cylindrical battery according to claim 1, characterized in that: The empty foil segment wraps around the load segment at least once, and an end of the empty foil segment exceeds the load segment, and the exceeding portion forms a third excess wrapping area.

9. The cylindrical battery according to claim 1, characterized in that: The negative electrode current collector is copper foil, and the shell is a stainless steel shell.

10. A battery module, characterized in that: The invention comprises a plurality of cylindrical batteries according to any one of claims 1 to 9.

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