Secondary battery

Abstract

To suppress an unevenness in the salt concentration of an electrolyte impregnated in a wound body, while maintaining the battery capacity.SOLUTION: A battery module 1 comprises: a wound body 30 which is formed in a flat shape, and around which a cathode sheet 50, an anode sheet 40, and a separator 45 located between the cathode sheet 50 and the anode sheet 40 are wound; a case 60 in which the wound body 30 is accommodated together with an electrolyte W; and a spacer 72 having a first rib 74A extending in a direction crossing the wound axis direction G of the wound body 30 and pressed against the case 60, and a second rib 74B extending in the wound axis direction G of the wound body 30 and pressed against the case 60, and forming a ventilation path between the case 60 and itself. Plasma treatment is applied to a section of the cathode sheet 50 and / or the anode sheet 40 against which the first rib 74A is pressed.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a secondary battery. [Background technology]

[0002] It is known that in a secondary battery, a spacer having comb-tooth ribs is pressed against a case that houses an electrode assembly to form an air passage (see, for example, Patent Document 1).

[0003] Patent Document 1 discloses a secondary battery in which a restraining member having a plurality of ribs arranged in a comb-like shape is pressed against the side of the secondary battery case. This secondary battery has a thin-walled portion in which the electrode active material layer provided on the electrode body is thin, at a position where a cross-direction rib pressing region is formed that is pressed against a cross-direction rib extension extending in a direction intersecting the winding axis direction of the electrode body. This suppresses the progress of high-rate degradation.

[0004] In a secondary battery, it is preferable to suppress unevenness in the salt concentration of the electrolyte impregnated in the wound body while maintaining the battery capacity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2022-074696 Summary of the Invention [Problem to be solved by the invention]

[0006] In consideration of the above, an object of the present invention is to suppress unevenness in the salt concentration of the electrolyte impregnated in the wound body while maintaining the battery capacity. [Means for solving the problem]

[0007] A secondary battery of a first aspect of the present invention comprises: a wound body formed into a flat shape by winding a positive electrode sheet, a negative electrode sheet, and a separator arranged between the positive electrode sheet and the negative electrode sheet; a case in which the wound body is accommodated together with an electrolyte; and a restraint member having a first rib extending in a direction intersecting a winding axis direction of the wound body and pressed against the case, and a second rib extending in the winding axis direction of the wound body and pressed against the case, and forming an air passage between the case and the restraint member, and a portion of at least one of the positive electrode sheet and the negative electrode sheet against which the first rib is pressed is subjected to plasma treatment.

[0008] In a second aspect of the secondary battery of the present invention, in the secondary battery of the first aspect of the present invention, a plasma treatment is applied to a portion of the wound body corresponding to a portion of the case where cooling air first hits.

[0009] In a secondary battery of a third aspect of the present invention, in the secondary battery of the first or second aspect of the present invention, the part of the wound body corresponding to the part of the case where the cooling air first hits is the R portion of the wound body.

[0010] In a secondary battery of a fourth aspect of the present invention, in the secondary battery of any one of the first to third aspects of the present invention, the plasma treatment is performed on at least one of the positive electrode sheet and the negative electrode sheet near the center in the winding axis direction.

[0011] A secondary battery according to a fifth aspect of the present invention is the secondary battery according to any one of the first to fourth aspects of the present invention, wherein the plasma treatment is performed on the negative electrode active material layer of the negative electrode sheet. Effect of the Invention

[0012] In the secondary battery of the first aspect of the present invention, the portion of at least one of the positive electrode sheet and the negative electrode sheet against which the first rib is pressed is subjected to plasma treatment, thereby improving the wettability of the portion of the electrode sheet subjected to the plasma treatment. Therefore, in the portion of the wound body against which the first rib is pressed, the movement of the electrolyte in the winding axis direction is promoted, and the return of the electrolyte to the wound body is improved. Moreover, the battery capacity can be maintained compared to the case where the return of the electrolyte to the wound body is improved by providing a groove in the wound body. As a result, the unevenness of the salt concentration of the electrolyte impregnated in the wound body can be suppressed while maintaining the battery capacity. This makes it possible to suppress high-rate deterioration in which the internal resistance increases due to the bias in the salt concentration.

[0013] In the secondary battery according to the second aspect of the present invention, the portion of the winding corresponding to the portion of the case where the cooling air first hits is subjected to plasma treatment, thereby improving the wettability of the portion of the electrode sheet where the plasma treatment is performed. Therefore, in the portion of the winding corresponding to the portion of the case where the cooling air first hits, the movement of the electrolyte in the winding axis direction is promoted, and the return of the electrolyte to the winding is improved. As a result, it is possible to suppress unevenness in the salt concentration of the electrolyte impregnated in the winding.

[0014] In the secondary battery according to the third aspect of the present invention, the portion of the winding that corresponds to the portion of the case where the cooling air first hits is the R portion of the winding, and the wettability of the R portion of the winding that has been subjected to the plasma treatment is improved. Therefore, in the R portion of the winding where the cooling air first hits the case, the movement of the electrolyte in the winding axis direction is promoted, and the return of the electrolyte to the winding is improved. As a result, it is possible to suppress unevenness in the salt concentration of the electrolyte impregnated in the winding.

[0015] In the secondary battery according to the fourth aspect of the present invention, at least one of the positive electrode sheet and the negative electrode sheet is subjected to a plasma treatment near the center in the winding axis direction, so that the plasma treatment is performed in the portion where the salt concentration is likely to be uneven. Therefore, in the portion where the salt concentration of the wound body is likely to be uneven, the movement of the electrolyte in the winding axis direction is promoted, and the return of the electrolyte to the wound body is improved. As a result, the unevenness of the salt concentration of the electrolyte impregnated in the wound body can be suppressed.

[0016] In the secondary battery of the fifth aspect of the present invention, the plasma treatment is performed on the negative electrode active material layer of the negative electrode sheet, so that the negative electrode active material layer of the negative electrode sheet that expands and contracts during high-rate charging and discharging is plasma treated. Therefore, in the portion that expands and contracts during high-rate charging and discharging, the movement of the electrolyte in the winding axis direction is promoted, and the return of the electrolyte to the wound body is improved. As a result, it is possible to suppress unevenness in the salt concentration of the electrolyte impregnated in the wound body. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a plan view showing a battery module according to the embodiment. [Diagram 2] FIG. 2 is an exploded perspective view showing a battery module according to the embodiment. [Diagram 3] FIG. 2 is an exploded perspective view showing a battery cell according to the embodiment. [Figure 4] 4 is a cross-sectional view showing a wound body according to the embodiment, showing a cross section taken along the line AA in FIG. [Diagram 5] FIG. 2 is a front view showing a spacer according to the embodiment. [Figure 6] FIG. 2 is a front view showing a wound body according to the embodiment. [Figure 7] FIG. 2 is a front view showing a battery cell according to the embodiment. [Figure 8] 8 is a cross-sectional view showing the battery cell according to the embodiment, showing the cross section taken along line BB in FIG. 7. [Figure 9] 13 shows test results confirming the effect of suppressing unevenness in salt concentration in a battery cell according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, a secondary battery according to an embodiment will be described with reference to the drawings. The secondary battery according to the embodiment is used as an on-board power source for, for example, an electric vehicle or a hybrid vehicle, and an example will be described in which lithium ion secondary batteries are stacked as battery cells (single cells) to form a battery module (assembled battery). In each drawing, an arrow D indicates the longitudinal direction D of the battery cell 10, an arrow E indicates the depth direction E of the battery cell 10, an arrow F indicates the up-down direction F of the battery cell 10, and an arrow T indicates the thickness direction T of the wound body 30. The longitudinal direction D of the battery cell 10 coincides with the winding axis direction G of the wound body 30, and one side of the winding axis direction G of the wound body 30 is a positive electrode, and the other side of the winding axis direction G of the wound body is a negative electrode.

[0019] [Battery module 1 configuration] 1 and 2, the battery module 1 includes a plurality of battery cells 10 and a plurality of restraining members 70 interposed between wide surfaces of the battery cells 10. In the battery module 1, the battery cells 10 and the restraining members 70 are arranged alternately in the depth direction E of the battery cells 10.

[0020] The restraining member 70 includes spacers 72 that are disposed between the battery cells 10, and end plates 76 that are disposed at both ends of the battery module.

[0021] The end plates 76 are arranged to sandwich the battery cells 10 and the spacers 72. For example, a restraining band (not shown) that restrains the end plates 76 applies a restraining pressure to the battery module 1 that compresses the battery cells 10 in the depth direction E.

[0022] [Configuration of battery cell 10] As shown in FIG. 3, the battery cell 10 includes a lid assembly 20, a wound body 30, a case 60, and an electrolyte W (see FIG. 7).

[0023] (Case 60) The case 60 is made of, for example, aluminum, and is formed in the shape of a rectangular box that is long in the longitudinal direction D and has an open top.

[0024] (Lid Assembly 20) The lid assembly 20 includes a lid member 21, a negative electrode current collector terminal 22 as a current collector terminal, a positive electrode current collector terminal 23 as a current collector terminal, a negative electrode external terminal 24 as an external terminal, and a positive electrode external terminal 25 as an external terminal.

[0025] <Cover member 21> The lid member 21 is made of, for example, aluminum, and is formed in a rectangular plate shape extending in the longitudinal direction D. The lid member 21 is provided with a safety valve 21A and a cap 26 that closes the injection port 21B.

[0026] The safety valve 21A opens when the internal pressure of the case 60 reaches a predetermined pressure, and discharges gas generated inside the case 60.

[0027] Inlet 21B is formed as a through hole penetrating in the plate thickness direction of cover member 21. Inlet 21B is used when injecting the electrolyte into case 60. Cap 26 is attached to inlet 21B, for example, by laser welding, and is hermetically sealed.

[0028] With the wound body 30, the negative electrode collector terminal 22, and the positive electrode collector terminal 23 housed inside the case 60, the cover member 21 is attached, for example by laser welding, to cover the opening of the case 60.

[0029] <Negative electrode current collector terminal 22 and negative electrode external terminal 24> The negative electrode current collector terminal 22 and the negative electrode external terminal 24 are made of copper, and are disposed on the other end side in the longitudinal direction D of the case 60. The negative electrode current collector terminal 22 is formed in a rectangular plate shape with the plate thickness direction being the depth direction E. The negative electrode current collector terminal 22 is joined to the negative electrode current collector part 32 of the wound body 30 by, for example, ultrasonic welding. The negative electrode external terminal 24 is electrically connected to the negative electrode current collector terminal 22, and is exposed to the outside of the cover member 21.

[0030] <Positive electrode current collector terminal 23 and positive electrode external terminal 25> The positive electrode current collector terminal 23 is made of aluminum, for example, and is disposed at one end side in the longitudinal direction D of the case 60. The positive electrode current collector terminal 23 is formed in a rectangular plate shape with the depth direction E as the plate thickness direction. The positive electrode current collector terminal 23 is joined to the positive electrode current collector part 33 of the wound body 30 by, for example, resistance welding. The positive electrode external terminal 25 is electrically connected to the positive electrode current collector terminal 23, and is exposed to the outside of the cover member 21.

[0031] (Wound body 30) 3 and 4, the wound body 30 has a power generating body 31, a negative electrode current collecting part 32, and a positive electrode current collecting part 33. The wound body 30 is formed in a flat shape having an R part 30A by winding a negative electrode sheet 40 as an electrode sheet, a positive electrode sheet 50 as an electrode sheet, and two separators 45 in a stacked state. The R part 30A is a part that has a vertical cross section that is formed in the wound wound body 30 and is a curved part with the largest curvature.

[0032] The power generating body 31 is formed by stacking a region of the positive electrode sheet 50 coated with a positive electrode active material, a region of the negative electrode sheet 40 coated with a negative electrode active material, and a separator 45. The power generating body 31 has a function of storing electric energy of the battery cell 10.

[0033] The negative electrode current collecting part 32 is not coated with an active material, and is formed by winding a negative electrode sheet 40. The positive electrode current collecting part 33 is not coated with an active material, and is formed by winding a positive electrode sheet 50.

[0034] <Negative electrode sheet 40> As shown in FIG. 4, the negative electrode sheet 40 is formed by coating a negative electrode mixture on both sides of a long strip-shaped negative electrode current collector 41, and forming a negative electrode active material layer .

[0035] The negative electrode active material layer 42 has an outer periphery side negative electrode active material layer 42A arranged on the outer periphery side, and an inner periphery side negative electrode active material layer 42B arranged on the inner periphery side.

[0036] <Positive electrode sheet 50> The positive electrode sheet 50 is formed by coating a positive electrode mixture on both sides of a long strip-shaped positive electrode current collector 51 to form a positive electrode active material layer 52 .

[0037] The positive electrode active material layer 52 has an outer periphery side positive electrode active material layer 52A arranged on the outer periphery side, and an inner periphery side positive electrode active material layer 52B arranged on the inner periphery side.

[0038] <Separator 45> The separator 45 is formed of an insulating material such as polypropylene, polyethylene, etc. The separator 45 is disposed between the positive electrode sheet 50 and the negative electrode sheet 40, and insulates the positive electrode sheet 50 from the negative electrode sheet 40.

[0039] (Electrolyte W) 7, the case 60 contains the wound body 30 and an electrolyte solution W. The electrolyte solution W is a composition in which a supporting salt is contained in a solvent.

[0040] [Configuration of Restraint Member 70] As shown in FIG. 1, the restraining member 70 includes a spacer 72 and an end plate 76 .

[0041] (Spacer 72) As shown in FIG. 5, the spacer 72 includes a base portion 73 and a comb-tooth-shaped rib 74 formed in a comb-tooth shape.

[0042] <Base part 73> The base portion 73 is formed in a rectangular plate shape with its plate thickness direction aligned in the depth direction E. The size of the wide surface of the base portion 73 can be approximately the same as the size of the wide surface of the case 60.

[0043] <Comb-tooth rib 74> The comb-tooth-shaped rib 74 is formed so as to protrude in the depth direction E from a wide surface on one side of the base portion 73. A plurality of comb-tooth-shaped ribs 74 are arranged at intervals from each other, and are formed into a comb-tooth-shaped cross section.

[0044] As shown in FIGS. 5 and 6, the comb-tooth-shaped rib 74 includes a first rib 74A and a second rib 74B.

[0045] The first rib 74A is provided near the center of the winding axis direction G of the wound body 30. The first rib 74A is formed to extend in a direction intersecting the winding axis direction G. The intersecting direction is a direction including a direction perpendicular to the winding axis direction G and a direction intersecting the winding axis direction G. The first rib 74A has a portion that extends upward from the lower end side of the base portion 73 and then curves toward the end side of the winding axis direction G of the wound body 30, and a portion that curves and extends from the middle part of the base portion 73 in the up-down direction F toward the end side of the winding axis direction G of the wound body 30.

[0046] The second rib 74B is formed to extend in the winding axis direction G. The second rib 74B is connected to the first rib 74A and extends to an end side of the wound body 30 in the winding axis direction G.

[0047] The first rib 74A and the second rib 74B are pressed against one wide surface of the case 60. This forms an air passage between the spacer 72 and the case for cooling air to pass through. The cooling air that is introduced between the battery cells 10 and the spacers 72 from the lower side of the battery module 1 is discharged from the side of the battery module 1.

[0048] [Flow of electrolyte W] 7, during high-rate charge / discharge in which a large current flows, the negative electrode active material layer 42 expands and contracts. When the negative electrode active material layer 42 expands, the electrolyte W impregnated in the wound body 30 flows out of the wound body 30 from both ends in the winding axis direction G. Then, when the negative electrode active material layer 42 contracts, the electrolyte W that has flowed out of the wound body 30 is absorbed into the wound body 30 from both ends in the winding axis direction G.

[0049] 8, the first rib 74A extending in a direction intersecting the winding axis direction G presses the wound body 30. When the first rib 74A presses the wound body 30, the wound body 30 is crushed, the movement of the electrolyte W in the winding axis direction G is hindered, and the return of the electrolyte W to the wound body 30 is deteriorated. As a result, the salt concentration of the electrolyte W impregnated in the wound body 30 becomes uneven, and there is a problem of high-rate deterioration in which the internal resistance increases due to the bias in the salt concentration.

[0050] Therefore, in this embodiment, in order to facilitate the movement of the electrolyte W in the winding axis direction G, the negative electrode active material layer 42 is subjected to a plasma treatment.

[0051] [Plasma treatment] As shown in FIGS. 6 and 7, the wound body 30 is formed with a first plasma-treated region S1 that has been subjected to plasma treatment, and a second plasma-treated region S2 that has been subjected to plasma treatment.

[0052] The first plasma treatment region S1 is a portion of the negative electrode sheet 40 corresponding to a portion where the first rib 74A is pressed against the case 60. The second plasma treatment region S2 is a portion of the negative electrode sheet 40 corresponding to a portion where the cooling air first hits the case 60. In this embodiment, the portion of the negative electrode sheet 40 corresponding to the portion where the cooling air first hits the case 60 is the R portion 30A on the lower side in the vertical direction of the wound body 30.

[0053] The first plasma treatment region S1 and the second plasma treatment region S2 are formed from the inner periphery side to the outer periphery side of the negative electrode sheet 40. The first plasma treatment region S1 and the second plasma treatment region S2 are applied to the outer periphery side negative electrode active material layer 42A and the inner periphery side negative electrode active material layer 42B of the negative electrode sheet 40.

[0054] The first plasma treatment region S1 is formed to be slightly larger than the area of ​​the upper surface of the first rib 74 A. The first plasma treatment region S1 and the second plasma treatment region S2 are formed near the center of the negative electrode sheet 40 in the winding axis direction G.

[0055] [Effectiveness verification test] A test was carried out to confirm the effect of suppressing unevenness in the salt concentration of the electrolyte W impregnated in the wound body 30 of the battery module 1 according to the embodiment.

[0056] In the tests, Example 1 in which a first plasma processing region S1 was formed, Example 2 in which a second plasma processing region S2 was formed, and Example 3 in which the first plasma processing region S1 and the second plasma processing region S2 were formed were prepared.

[0057] Also prepared were Comparative Example 1, which was not subjected to plasma treatment, and Comparative Example 2, which was provided with a thin portion in the negative electrode active material layer 42. The thin portion in the negative electrode active material layer 42 was formed in a portion corresponding to the portion against which the first rib 74A was pressed.

[0058] Then, the battery module 1 was charged and discharged for a predetermined period of time, and the resistance increase rate, which is the ratio of the battery resistance after use to the battery resistance before use, was measured.

[0059] As shown in FIG. 9, in Example 1, the initial capacity of the battery module 1 was 3.6 [Ah] and the resistance increase rate was 118 [%]. In Example 2, the initial capacity of the battery module 1 was 3.6 [Ah] and the resistance increase rate was 119 [%]. In Example 3, the initial capacity of the battery module 1 was 3.6 [Ah] and the resistance increase rate was 117 [%]. In Comparative Example 1, the initial capacity of the battery module 1 was 3.6 [Ah] and the resistance increase rate was 120 [%]. In Comparative Example 2, the initial capacity of the battery module 1 was 3.5 [Ah] and the resistance increase rate was 118 [%].

[0060] As a result of the test, it was found that Examples 1 to 3 had a lower resistance increase rate than Comparative Example 1, and suppressed unevenness in the salt concentration of the electrolyte W impregnated in the wound body 30. It was also found that Examples 1 to 3 had the same initial capacity (initial battery capacity) as Comparative Example 1, and had a larger initial capacity than Comparative Example 2.

[0061] [Effect] The battery module 1 of the embodiment includes a wound body 30 formed into a flat shape by winding a positive electrode sheet 50, a negative electrode sheet 40, and a separator 45 arranged between the positive electrode sheet 50 and the negative electrode sheet 40, a case 60 in which the wound body 30 is accommodated together with an electrolyte W, and a spacer 72 having a first rib 74A extending in a direction intersecting the winding axis direction G of the wound body 30 and pressed against the case 60, and a second rib 74B extending in the winding axis direction G of the wound body 30 and pressed against the case 60, and forming an air passage between the spacer 72 and the case 60, and a portion of the negative electrode sheet 40 against which the first rib 74A is pressed is subjected to plasma treatment (see FIG. 7).

[0062] By subjecting the portion of the negative electrode sheet 40 against which the first rib 74A is pressed, the wettability of the portion of the negative electrode sheet 40 against which the plasma treatment is applied is improved. Therefore, in the portion of the wound body 30 against which the first rib 74A is pressed, the movement of the electrolyte W in the winding axis direction G is promoted, and the return of the electrolyte W to the wound body 30 is improved. Moreover, compared to the case where a groove is provided in the wound body 30 to improve the return of the electrolyte W to the wound body 30, the battery capacity can be maintained. As a result, it is possible to suppress unevenness in the salt concentration of the electrolyte W impregnated in the wound body 30 while maintaining the battery capacity. This makes it possible to suppress high-rate deterioration in which the internal resistance increases due to the bias in the salt concentration.

[0063] Incidentally, the portion of the case 60 that the cooling wind hits first has high cooling efficiency within the secondary battery. Therefore, the viscosity of the electrolyte W in the vicinity of the portion of the case 60 that the cooling wind hits first becomes high. As a result, the electrolyte W does not return to the wound body 30 as easily.

[0064] In the battery module 1 of the embodiment, a plasma treatment is applied to a portion of the wound body 30 that corresponds to a portion of the case 60 where the cooling air first hits (see FIG. 7).

[0065] By subjecting the portion of the wound body 30 corresponding to the portion of the case 60 where the cooling air first hits, the wettability of the portion of the negative electrode sheet 40 where the plasma treatment has been applied is improved. Therefore, in the portion of the wound body 30 corresponding to the portion of the case 60 where the cooling air first hits, the movement of the electrolyte W in the winding axis direction G is promoted, and the return of the electrolyte W to the wound body 30 is improved. As a result, unevenness in the salt concentration of the electrolyte W impregnated in the wound body 30 can be suppressed.

[0066] In the battery module 1 of the embodiment, the portion of the wound body 30 corresponding to the portion of the case 60 that is first hit by the cooling air is the R portion 30A of the wound body 30 (see FIG. 7).

[0067] The portion of the wound body 30 corresponding to the portion where the cooling air first hits the case 60 is the R portion 30A of the wound body 30, and thus the wettability of the R portion 30A of the wound body 30 that has been subjected to the plasma treatment is improved. Therefore, in the R portion 30A of the wound body 30 where the cooling air first hits the case 60, the movement of the electrolyte W in the winding axis direction G is promoted, and the return of the electrolyte W to the wound body 30 is improved. As a result, unevenness in the salt concentration of the electrolyte W impregnated in the wound body 30 can be suppressed.

[0068] In the battery module 1 of the embodiment, a plasma treatment is performed on the negative electrode sheet 40 near the center in the winding axis direction G (see FIG. 7).

[0069] By subjecting the negative electrode sheet 40 to plasma treatment near the center in the winding axis direction G, the plasma treatment is applied to the portion where unevenness in the salt concentration is likely to occur. Therefore, in the portion of the wound body 30 where unevenness in the salt concentration is likely to occur, the movement of the electrolyte W in the winding axis direction G is promoted, and the return of the electrolyte W to the wound body 30 is improved. As a result, unevenness in the salt concentration of the electrolyte W impregnated in the wound body 30 can be suppressed.

[0070] In the battery module 1 of the embodiment, the plasma treatment is performed on the negative electrode active material layer 42 of the negative electrode sheet 40 (see FIG. 7).

[0071] The plasma treatment is performed on the negative electrode active material layer 42 of the negative electrode sheet 40, which expands and contracts during high-rate charge and discharge. This promotes movement of the electrolyte W in the winding axis direction G in the portion that expands and contracts during high-rate charge and discharge, improving the return of the electrolyte W to the wound body 30. As a result, unevenness in the salt concentration of the electrolyte W impregnated in the wound body 30 can be suppressed.

[0072] The secondary battery of the present invention has been described above based on the above embodiment. However, the specific configuration is not limited to this embodiment, and design changes and the like are permitted as long as they do not deviate from the gist of the invention according to each claim in the scope of the claims.

[0073] In the embodiment, an example has been shown in which the first plasma processing region S1 and the second plasma processing region S2 are formed in the wound body 30. However, the wound body 30 may be formed with only the first plasma processing region S1.

[0074] In the embodiment, an example has been shown in which the first plasma treatment region S1 and the second plasma treatment region S2 are applied to the outer periphery side negative electrode active material layer 42A and the inner periphery side negative electrode active material layer 42B of the negative electrode sheet 40. However, the first plasma treatment region S1 and the second plasma treatment region S2 may be applied to one of the outer periphery side negative electrode active material layer 42A and the inner periphery side negative electrode active material layer 42B of the negative electrode sheet 40.

[0075] In the embodiment, an example has been shown in which the first plasma treatment region S1 and the second plasma treatment region S2 are applied to the negative electrode sheet 40. However, the first plasma treatment region S1 and the second plasma treatment region S2 may be applied to the positive electrode sheet 50 or the separator 45.

[0076] In the embodiment, an example has been shown in which the comb-tooth-shaped rib 74 is formed on one wide surface of the base portion 73. However, the comb-tooth-shaped rib 74 may be formed on both wide surfaces of the base portion 73.

[0077] In the embodiment, an example has been shown in which the comb-tooth ribs 74 are formed on the spacer 72. However, the comb-tooth ribs may be formed on the end plates 76.

[0078] In the embodiment, an example has been described in which the secondary battery is a battery module (battery pack). However, the secondary battery may be a battery cell (single cell). [Explanation of symbols]

[0079] 1. Battery module (an example of a secondary battery) 30 Wound body 30A R section 40 Negative electrode sheet 42 Negative electrode active material layer 50 Positive electrode sheet 60 cases 72 Spacer (an example of a restraining member) 74A 1st Rib 74B 2nd Rib G Winding axis direction W Electrolyte

Claims

1. a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet, which are wound together to form a flat wound body; a case in which the winding body is housed together with an electrolyte; a restraining member including a first rib extending in a direction intersecting a winding axis direction of the wound body and pressed against the case, and a second rib extending in the winding axis direction of the wound body and pressed against the case, and forming an air passage between the winding member and the case, A plasma treatment is performed on a portion of at least one of the positive electrode sheet and the negative electrode sheet against which the first rib is pressed. Secondary battery.

2. A plasma treatment is applied to the portion of the winding that corresponds to the portion of the case where the cooling air first hits. The secondary battery according to claim 1 .

3. The portion of the winding body that corresponds to the portion of the case where the cooling air first hits is the R portion of the winding body. The secondary battery according to claim 2 .

4. The plasma treatment is performed on at least one of the positive electrode sheet and the negative electrode sheet near the center in the winding axis direction. The secondary battery according to claim 1 .

5. The plasma treatment is performed on the negative electrode active material layer of the negative electrode sheet.

2. The secondary battery according to claim 1.

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