JP7119956B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention relates to a non-aqueous electrolyte secondary battery.

Non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries are attracting attention as power sources for mobile devices and as power sources for driving vehicles such as electric vehicles and hybrid vehicles. For example, Patent Document 1 describes a non-aqueous electrolyte secondary battery in which a wound electrode body in which a strip-shaped positive electrode sheet, a strip-shaped negative electrode sheet, and a strip-shaped separator sheet are wound around an axis; A battery case for housing an electrode body; and an insulating member made of an electrically insulating film in the form of a bag, wherein the wound electrode body is arranged inside the insulating member and the insulating member is housed in the battery case. and a non-aqueous electrolyte contained inside the wound electrode body.

JP 2016-219143 A

By the way, when a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery is charged at a high rate, the wound electrode body heats up and expands, and the non-aqueous electrolyte contained in the wound electrode body expands. is heated and expands. As a result, the non-aqueous electrolyte contained inside the wound electrode body flows from the end surfaces located at both ends in the axial direction of the wound electrode body (between the positive electrode sheets adjacent in the radial direction of the wound electrode body, It sometimes flowed out of the wound electrode body through between the negative electrode sheets or between the separator sheets. The non-aqueous electrolyte that has flowed out of the wound electrode body spreads over the entire inner bottom surface of the insulating member, for example, and is difficult to return to the inside of the wound electrode body.

Therefore, when high-rate charging and discharging is performed, the non-aqueous electrolyte flows out from the inside of the wound electrode body to the outside, so that the inside of the wound electrode body (more specifically, in the axial direction) becomes non-aqueous. The salt concentration of the electrolytic solution (concentration of electrolyte such as Li salt) may be uneven. As a result, the resistance value may vary (unevenness) inside the wound electrode body (more specifically, in the axial direction). As a result, the battery characteristics (battery capacity, output characteristics, etc.) may deteriorate.

The present invention has been made in view of such a situation, and solves the variation (unevenness) in the resistance value that occurs inside the wound electrode body (in particular, in the axial direction) even when high-rate charging and discharging is performed. An object of the present invention is to provide a non-aqueous electrolyte secondary battery capable of reducing the

One aspect of the present invention is a wound electrode body in which a strip-shaped positive electrode sheet, a strip-shaped negative electrode sheet, and a strip-shaped separator sheet are wound around an axis; a battery case that houses the wound electrode body; An insulating member made of an electrically insulating film in the form of a bag, wherein the wound electrode body is arranged inside the insulating member, and the insulating member is accommodated in the battery case, and the inside of the wound electrode body In the non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte contained in a non-aqueous electrolyte secondary battery, the inner surface of the insulating member includes: and an intermediate portion positioned between the one side portion and the other side portion in the axial direction, wherein the one side portion and the other side portion The non-aqueous electrolyte secondary battery has a higher affinity for the non-aqueous electrolyte than the middle portion.

The above-mentioned non-aqueous electrolyte secondary battery includes a wound electrode body, a battery case for housing the wound electrode body, an insulating member formed by a bag-shaped electrically insulating film, and a wound electrode body. and a non-aqueous electrolyte. Among these, the wound electrode body is a wound electrode body obtained by winding a strip-shaped positive electrode sheet, a strip-shaped negative electrode sheet, and a strip-shaped separator sheet around an axis. In addition, the insulating member has the wound electrode body disposed inside the insulating member and is accommodated in the battery case.
In this non-aqueous electrolyte secondary battery, the inner surface of the insulating member in which the wound electrode assembly is arranged (the surface facing the wound electrode assembly, that is, the surface facing the opposite side to the battery case) serves as the wound electrode. one side portion located on one side in the axial direction of the wound electrode body (the direction along the axis of the wound electrode body), the other side portion located on the other side in the axial direction of the wound electrode body, and the wound electrode body It is composed of an intermediate portion positioned between one side portion and the other side portion in the axial direction.

Furthermore, in the nonaqueous electrolyte secondary battery described above, the one side portion and the other side portion of the inner surface of the insulating member have a higher affinity for the nonaqueous electrolyte than the intermediate portion. Therefore, when the non-aqueous electrolyte secondary battery described above is subjected to high-rate charge/discharge, the non-aqueous electrolyte contained inside the wound electrode body is discharged from both ends of the wound electrode body in the axial direction. (a first end surface located on one side and a second end surface located on the other side in the axial direction) to the outside of the wound electrode assembly, the non-aqueous electrolyte that has flowed out is placed on the inner surface of the insulating member. It becomes possible to accumulate (collect) the one side portion and the other side portion having a high affinity for the non-aqueous electrolyte.

As described above, in the non-aqueous electrolyte secondary battery described above, the non-aqueous electrolyte that has flowed out of the wound electrode body is displaced from the inner surface of the insulating member at both ends of the wound electrode body in the axial direction. It can be accumulated (collected) in one side and the other side near the end faces (the first end face located on one side and the second end face located on the other side in the axial direction).

As a result, the non-aqueous electrolyte that has flowed out to the outside of the wound electrode body can easily return to the inside of the wound electrode body through the first end face and the second end face of the wound electrode body. Specifically, the non-aqueous electrolyte flowing out of the wound electrode body flows from the first end surface and the second end surface of the wound electrode body to the positive electrode sheet adjacent to the wound electrode body in the radial direction by capillary action, It becomes easy to return to the inside of the wound electrode body through the gaps of the negative electrode sheet or the separator sheet.

Therefore, in the above-described non-aqueous electrolyte secondary battery, even when high-rate charging and discharging are performed, the salt concentration of the non-aqueous electrolyte (Li salt, etc.) concentration of the electrolyte) is less likely to occur, and the resistance value is less likely to vary (in particular, in the axial direction) inside the wound electrode assembly.
As described above, in the non-aqueous electrolyte secondary battery described above, even when high-rate charge/discharge is performed, variation (unevenness) in the resistance value occurs inside the wound electrode body (in detail, in the axial direction). can be reduced.

The one side portion of the inner surface of the insulating member is, for example, a portion located on one side of the first end surface located on one side in the axial direction of the wound electrode body disposed inside, and a portion thereof. It is composed of adjacent (adjacent to the other side) portions. Further, the other side portion of the inner surface of the insulating member is, for example, a portion of the wound electrode body disposed inside which is located on the other side of the second end surface located on the other side in the axial direction, and It is composed of adjacent (adjacent to one side) portions. The end face of the wound electrode body is the end face of at least one of the positive electrode sheet, the negative electrode sheet, and the separator sheet, and is the end face exposed to the outside. It is the side facing the

1 is a partial cross-sectional view of a non-aqueous electrolyte secondary battery according to an embodiment; FIG. 1 is a perspective view of a wound electrode body according to an embodiment; FIG. 1 is a perspective view of an insulating member according to an embodiment; FIG. FIG. 4 is a plan view of an electrically insulating film that constitutes the same insulating member; FIG. 4 is a diagram showing a state in which a wound electrode assembly is arranged inside an insulating member; It is a figure which shows the result of a high-rate charging/discharging test.

(embodiment)
Next, embodiments of the present invention will be described with reference to the drawings.
The non-aqueous electrolyte secondary battery 1 of the present embodiment, as shown in FIG. Battery. The battery case 10 includes a rectangular box-shaped housing portion 11 having an opening 11 d and a terminal-fitted battery case lid 15 having a lid body 13 that closes the opening 11 d of the housing portion 11 . The housing portion 11 and the lid 13 are integrally welded together.

The wound electrode body 50 has an oval cross section, and is a flat type formed by interposing a separator sheet 57 between a strip-shaped positive electrode sheet 55 and a strip-shaped negative electrode sheet 56 and winding them around an axis line AX. (see FIGS. 1 and 2). The wound electrode body 50 is positioned on one side (left side in FIG. 1) in the axial direction DX (the direction along the axis AX, the left-right direction in FIG. 1), and only a portion of the positive electrode sheet 55 is spirally wound. It has an overlapping positive electrode winding portion 55b and a negative electrode winding portion 56b located on the other side (right side in FIG. 1) where only a part of the negative electrode sheet 56 is spirally overlapped.

A portion of the wound electrode body 50 positioned between the positive electrode wound portion 55b and the negative electrode wound portion 56b in the axial direction DX is defined as an electrode body intermediate portion 50g. A positive electrode mixture layer containing a positive electrode active material is formed on the positive electrode sheet 55 except for the positive electrode wound portion 55b. Similarly, a negative electrode mixture layer containing a negative electrode active material is formed on the negative electrode sheet 56 except for the negative electrode wound portion 56b. A non-aqueous electrolyte 90 is contained inside the wound electrode body 50 . The non-aqueous electrolyte 90 is a non-aqueous solvent obtained by dissolving lithium hexafluorophosphate, which is an Li salt, in a non-aqueous solvent in which EC (ethylene carbonate), DMC (dimethyl carbonate), and EMC (ethyl methyl carbonate) are mixed. Aqueous electrolyte.

The terminal-equipped battery case lid 15 has a lid body 13 , a first insulating member 80 , a positive electrode terminal member 30 , a negative electrode terminal member 40 and a second insulating member 70 . Of these, the lid 13 has an elongated flat plate shape, and circular through-holes passing through the lid 13 are formed at both ends in the axial direction DX. A safety valve 13j is provided in the central portion of the lid 13 in the longitudinal direction X. As shown in FIG. Also, in the cover 13, between the safety valve 13j and the through hole, a liquid injection port 13n is formed for injecting the non-aqueous electrolyte 90 into the housing portion 11 (specifically, the insulating member 60). It is The liquid injection port 13n is sealed by a liquid injection plug 13m (see FIG. 1).

The positive electrode terminal member 30 is composed of a positive electrode connecting member 35, a positive external terminal 37, and a positive electrode fastening member 39 (see FIG. 1). Among them, the positive electrode connection member 35 is made of metal, is connected to the positive electrode wound portion 55 b of the wound electrode body 50 , and extends to the outside through the through hole of the lid 13 . The positive electrode external terminal 37 is made of metal, is positioned above the lid 13 (outside the battery case 10 ), and is electrically connected to the positive electrode connection member 35 outside the battery case 10 . The positive electrode fastening member 39 is a bolt made of metal, is positioned outside the battery case 10, and fastens the positive electrode external terminal 37 and a bus bar (not shown).

The negative electrode terminal member 40 is composed of a negative electrode connecting member 45, a negative external terminal 47, and a negative electrode fastening member 49 (see FIG. 1). Among them, the negative electrode connecting member 45 is made of metal, is connected to the negative electrode winding portion 56 b of the wound electrode body 50 , and extends to the outside through the through hole of the lid 13 . The negative electrode external terminal 47 is made of metal, is positioned above the lid 13 (outside the battery case 10 ), and is electrically connected to the negative electrode connection member 45 outside the battery case 10 . The negative electrode fastening member 49 is a bolt made of metal, is positioned on the lid 13 (outside the battery case 10), and fastens the negative electrode external terminal 47 and a bus bar (not shown).

Further, the non-aqueous electrolyte secondary battery 1 of the present embodiment is made of an electrically insulating film 60A, and is provided with an insulating member 60 in which the electrically insulating film 60A is shaped like a rectangular bag (FIGS. 1, 3, and 4). 4). The insulating member 60 of this embodiment is manufactured by folding an electrically insulating film 60A along the folding lines indicated by broken lines in FIG.

The insulating member 60 arranges (accommodates) the wound electrode body 50 inside the insulating member 60 and is accommodated in the battery case 10 . 3 is a perspective view of the insulating member 60. FIG. FIG. 4 is a plan view of an electrically insulating film 60A that constitutes the insulating member 60 (corresponding to a developed view of the insulating member 60). 5 is a schematic perspective view showing a state in which the wound electrode body 50 is arranged inside the insulating member 60 in the non-aqueous electrolyte secondary battery 1. As shown in FIG. 5, illustration of the terminal-fitted battery case lid 15 and the like is omitted.

In the non-aqueous electrolyte secondary battery 1 of the present embodiment, as shown in FIGS. One side portion 61 positioned on one side DX1 (the left side in FIG. 1) with respect to DX (the direction along the axis AX of the wound electrode body 50) and the other side DX2 (the direction along the axis AX of the wound electrode body 50) with respect to the axial direction DX of the wound electrode body 50 ( and an intermediate portion 65 positioned between the one side portion 61 and the other side portion 62 in the axial direction DX of the wound electrode assembly 50 .

In addition, the inner surface 60b of the insulating member 60 is the surface facing the wound electrode body 50 side (inside) in the non-aqueous electrolyte secondary battery 1, that is, the surface facing the side opposite to the battery case 10 side (outside). be. In FIG. 5, the boundary between the one side portion 61 and the intermediate portion 65 and the boundary between the other side portion 62 and the intermediate portion 65 of the inner surface 60b are indicated by two-dot chain lines. Furthermore, in FIG. 5, the one side portion 61 and the other side portion 62 of the inner surface 60b are hatched with dots, and the intermediate portion 65 is hatched with oblique lines. The same applies to FIGS. 3 and 4 as well.

In the present embodiment, the one side portion 61 of the inner surface 60b of the insulating member 60 is the first end surface 50j facing the one side DX1 of the wound electrode body 50 in the axial direction DX (the end surface of the positive electrode wound portion 55b is spirally wound). It is composed of a portion located on one side DX1 and a portion adjacent thereto (close to the other side DX2) (see FIGS. 1 and 5). Specifically, one side portion 61 of the inner surface 60b of the insulating member 60 includes a first surface 61b facing the first end surface 50j of the wound electrode body 50 in the axial direction DX, and a positive electrode wound portion of the wound electrode body 50. The second surface 61c facing the first side surface of the portion 55b (the side surface on the front side in FIGS. 1 and 5) and the second side surface of the positive electrode winding portion 55b (the side surface on the back side in FIGS. 1 and 5) face each other. and a fourth surface 61f facing the arc-shaped bottom surface of the positive electrode wound portion 55b (see FIG. 5).

Further, the other side portion 62 of the inner surface 60b of the insulating member 60 is a second end surface 50k facing the other side DX2 of the wound electrode body 50 in the axial direction DX (a portion where the end surfaces of the negative electrode wound portion 56b spirally overlap). It is composed of a portion located on the other side DX2 and a portion adjacent thereto (close to one side DX1) (see FIGS. 1 and 5). Specifically, the other side portion 62 of the inner surface 60b of the insulating member 60 includes a first surface 62b facing the second end surface 50k of the wound electrode body 50 in the axial direction DX, and a negative electrode wound portion of the wound electrode body 50. The second surface 62c facing the first side surface of the portion 56b (the side surface on the front side in FIGS. 1 and 5) and the second side surface of the negative electrode winding portion 56b (the side surface on the back side in FIGS. 1 and 5) face each other. and a fourth surface 62f facing the arcuate bottom surface of the negative electrode wound portion 56b (see FIG. 5).

The intermediate portion 65 of the inner surface 60b of the insulating member 60 includes a first surface 65b facing the first side surface (the side surface on the front side in FIGS. 1 and 5) of the electrode body intermediate portion 50g of the wound electrode body 50, It has a second surface 65c that faces the second side surface of the electrode intermediate portion 50g (the side surface on the far side in FIGS. 1 and 5) and a third surface 65d that faces the arc-shaped bottom surface of the electrode intermediate portion 50g (see FIG. 5). 5).

By the way, conventionally, when a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery is subjected to high-rate charging or high-rate charging and discharging, the wound electrode body heats up and expands, and furthermore, the inside of the wound electrode body The contained non-aqueous electrolyte may be heated and expanded. As a result, the non-aqueous electrolyte contained inside the wound electrode body flows from the end surfaces located at both ends in the axial direction of the wound electrode body (between the positive electrode sheets adjacent in the radial direction of the wound electrode body, It sometimes flowed out of the wound electrode body through between the negative electrode sheets or between the separator sheets. The non-aqueous electrolyte that has flowed out of the wound electrode body spreads over the entire inner bottom surface of the insulating member, for example, and is difficult to return to the inside of the wound electrode body.

Therefore, when high-rate charging and discharging is performed, the non-aqueous electrolyte flows out from the inside of the wound electrode body to the outside, so that the inside of the wound electrode body (more specifically, in the axial direction) becomes non-aqueous. The salt concentration of the electrolytic solution (concentration of electrolyte such as Li salt) may be uneven. As a result, the resistance value may vary (unevenness) inside the wound electrode body (more specifically, in the axial direction). As a result, the battery characteristics (battery capacity, output characteristics, etc.) may deteriorate.

On the other hand, in the non-aqueous electrolyte secondary battery 1 of the present embodiment, the one side portion 61 and the other side portion 62 of the inner surface 60 b of the insulating member 60 are more likely to contain the non-aqueous electrolyte 90 than the intermediate portion 65 . has a high affinity for More specifically, in the present embodiment, the insulating member 60 is formed of the inner surface of a resin film (for example, a resin film made of polyolefin such as polypropylene or polyethylene) that has poor affinity (low affinity) for the non-aqueous electrolyte 90. Of the 60b, the portions that become the one side portion 61 and the other side portion 62 are formed of an electrically insulating film 60A (see FIG. 4) that has a high affinity for the non-aqueous electrolyte 90 by corona treatment. .

Such an electrically insulating film 60A can be produced, for example, as follows. Specifically, first, a resin film (for example, a resin film made of polyolefin such as polypropylene or polyethylene) having poor affinity (low affinity) for the non-aqueous electrolytic solution 90 is prepared. Then, a portion of the inner surface 60b of the resin film that will become the intermediate portion 65 (the portion hatched with oblique lines in FIG. 4) is covered with a sheet for preventing corona treatment (corona discharge irradiation prevention sheet). , the inner surface 60b of the resin film is subjected to corona treatment (that is, only the portions of the inner surface 60b of the resin film that become the one side portion 61 and the other side portion 62 are subjected to corona discharge irradiation). Thereby, the electrically insulating film 60A described above can be obtained.

Therefore, in the nonaqueous electrolyte secondary battery 1 of the present embodiment, the one side portion 61 and the other side portion 62 of the inner surface 60b of the insulating member 60 have relatively high affinity for the nonaqueous electrolyte 90 ( hydrophilic), and the intermediate portion 65 has relatively low affinity for the non-aqueous electrolyte 90 (also hydrophobic).

Therefore, when the non-aqueous electrolyte secondary battery 1 of the present embodiment is subjected to high-rate charging and discharging, the non-aqueous electrolyte 90 contained inside the wound electrode body 50 is When flowing out to the outside of the wound electrode body 50 (inside the insulating member 60) from the first end face 50j located on the one side DX1 in the axial direction DX and the second end face 50k located on the other side DX2 of the axial direction DX, The non-aqueous electrolyte 90 can be collected (accumulated) in the one side portion 61 and the other side portion 62 of the inner surface 60 b of the insulating member 60 that have a high affinity for the non-aqueous electrolyte 90 .

As described above, in the non-aqueous electrolyte secondary battery 1 of the present embodiment, the non-aqueous electrolyte 90 that has flowed out of the wound electrode body 50 is removed from the inner surface 60 b of the insulating member 60 by the wound electrode body 50 . One side portion 61 and the other side portion located near end faces located at both ends in the axial direction DX (a first end face 50j located on one side DX1 and a second end face 50k located on the other side DX2 in the axial direction DX). 62 can be collected (accumulated).

This makes it easier for the non-aqueous electrolyte 90 that has flowed out of the wound electrode body 50 to return to the inside of the wound electrode body 50 through the first end face 50j and the second end face 50k of the wound electrode body 50 . Specifically, the non-aqueous electrolyte 90 collected (accumulated) in the one side portion 61 and the other side portion 62 of the insulating member 60 after flowing out from the inside of the wound electrode body 50 is used as the wound electrode body. From the first end face 50j and the second end face 50k of the wound electrode body 50, the wound electrode body 50 is caused to flow through the gaps between the positive electrode sheet 55, the negative electrode sheet 56, or the separator sheet 57 adjacent in the radial direction of the wound electrode body 50 due to capillary action. It becomes easier to return to the inside of the

Therefore, in the non-aqueous electrolyte secondary battery 1 of the present embodiment, even when high-rate charging and discharging are performed, the non-aqueous electrolyte 90 is Nonuniformity in the salt concentration (concentration of lithium hexafluorophosphate, which is a Li salt) is less likely to occur, and in the wound electrode body 50 (more specifically, in the axial direction DX), the resistance value varies ( unevenness) is less likely to occur.
As described above, in the non-aqueous electrolyte secondary battery 1 of the present embodiment, even if high-rate charge/discharge is performed, the resistance value generated inside the wound electrode body 50 (in detail, in the axial direction DX) variation (unevenness) can be reduced.

(High rate charge/discharge test)
The non-aqueous electrolyte secondary battery 1 of the present embodiment was subjected to cyclic charging and discharging at a current value of 13 C, and the internal resistance value of the wound electrode assembly 50 was measured. In this test, the resistance values were measured at a plurality of positions different in the axial direction DX over the entire wound electrode body 50 (more specifically, the electrode body intermediate portion 50g) in the axial direction DX. The results are shown in FIG. 6 (dashed curve). FIG. 6 shows the correlation between the position of the wound electrode body 50 in the axial direction DX and its internal resistance value. In FIG. 6, the left side of the horizontal axis is the one side DX1 in the axial direction DX, and the right side of the horizontal axis is the other side DX2 in the axial direction DX.

In addition, the non-aqueous electrolyte secondary battery (not shown) of the comparative embodiment differs from the non-aqueous electrolyte secondary battery 1 of the embodiment in the affinity of the inner surface of the insulating member for the non-aqueous electrolyte 90. Non-aqueous electrolyte secondary batteries that differed only in this were prepared. Specifically, in the comparative embodiment, the inner surface of the electrically insulating film was not subjected to corona treatment, and the portion to be one side portion and the portion to be the other side portion of the inner surface of the electrically insulating film were separated from each other in the intermediate portion. An insulating member formed of an electrically insulating film having a low affinity for the non-aqueous electrolytic solution 90 is used, as in the case of the corresponding portion. That is, in the comparative embodiment, an insulating member whose entire inner surface is formed of an electrically insulating film having a low affinity (also hydrophobic) for the non-aqueous electrolyte 90 is used as the insulating member.

Therefore, in the non-aqueous electrolyte secondary battery of the comparative example, the affinity for the non-aqueous electrolyte 90 on one side and the other side of the inner surface of the insulating member is higher than that of the non-aqueous electrolyte secondary battery 1 of the embodiment. getting low. Specifically, in the non-aqueous electrolyte secondary battery of the comparative example, the inner surface of the insulating member has a lower affinity for the non-aqueous electrolyte 90 at the one side and the other side, as with the intermediate portion. (It is also hydrophobic). That is, in the comparative embodiment, an insulating member whose entire inner surface has a low affinity for the non-aqueous electrolyte 90 (also hydrophobic) is used as the insulating member. The non-aqueous electrolyte secondary battery of this comparative example was also subjected to cycle charging and discharging in the same manner as the non-aqueous electrolyte secondary battery 1 of the embodiment, and the internal resistance value of the wound electrode assembly 50 was measured. The results are shown in FIG. 6 (solid curve).

As shown in FIG. 6, in the non-aqueous electrolyte secondary battery 1 of the embodiment, the resistance value inside the wound electrode body 50 (specifically, the axis line The variation (unevenness) of the internal resistance value in the direction DX could be reduced. More specifically, in the non-aqueous electrolyte secondary battery 1 of the embodiment, the maximum value of the internal resistance of the wound electrode body 50 is significantly reduced compared to the non-aqueous electrolyte secondary battery of the comparative embodiment. I was able to The variation in the internal resistance value of the wound electrode body 50 correlates with the variation in the salt concentration (concentration of Li salt) of the non-aqueous electrolyte 90 inside the wound electrode body.

In the non-aqueous electrolyte secondary battery 1 of the embodiment, the variation (unevenness) in the internal resistance value of the wound electrode assembly 50 was able to be reduced as compared with the non-aqueous electrolyte secondary battery of the comparative form. , can be considered as follows.

Specifically, in the non-aqueous electrolyte secondary battery of the comparative example, the insulating member is an insulating member whose entire inner surface is formed of an electrically insulating film having a low affinity (also hydrophobic) for the non-aqueous electrolyte 90. is used, in the high-rate charge/discharge test, the non-aqueous electrolyte 90 contained inside the wound electrode body 50 flows from the first end face 50j and the second end face 50k of the wound electrode body 50 to the wound electrode When flowing out to the outside of the body 50 (inside the insulating member 60 ), the non-aqueous electrolytic solution 90 that has flowed out spreads over the entire insulating member 60 (entire inner bottom surface), and spreads inside the wound electrode assembly 50 . It is thought that it has become difficult to return.

Therefore, in the non-aqueous electrolyte secondary battery of the comparative example, the non-aqueous electrolyte flows out from the inside of the wound electrode assembly 50 to the outside. DX), it is considered that the non-aqueous electrolyte 90 has a large variation in the salt concentration (concentration of Li salt). It is believed that this caused a large variation (unevenness) in the resistance value inside the wound electrode body 50 (in detail, in the axial direction DX).

On the other hand, in the non-aqueous electrolyte secondary battery 1 of the embodiment, non-aqueous electrolysis is performed on the one side portion 61 and the other side portion 62 of the inner surface 60b of the insulating member 60 in which the wound electrode body 50 is arranged. The affinity for the liquid 90 is relatively high (also hydrophilic), and the intermediate portion 65 has relatively low affinity for the non-aqueous electrolyte 90 (also hydrophobic).

Therefore, in the non-aqueous electrolyte secondary battery 1 of the embodiment, the non-aqueous electrolyte 90 contained inside the wound electrode assembly 50 is applied to the first end surface of the wound electrode assembly 50 in the high-rate charge/discharge test. 50 j and the second end surface 50 k to the outside of the wound electrode assembly 50 (inside the insulating member 60 ). It is thought that it was possible to collect (accumulate) in the one side portion 61 and the other side portion 62 having a high affinity for. That is, in the non-aqueous electrolyte secondary battery 1 of the embodiment, the non-aqueous electrolyte 90 that has flowed out of the wound electrode body 50 is placed near the first end face 50j and the second end face 50k of the wound electrode body 50. It is thought that it was possible to collect (accumulate).

It is believed that this makes it easier for the non-aqueous electrolyte 90 that has flowed out of the wound electrode body 50 to return to the inside of the wound electrode body 50 through the first end face 50j and the second end face 50k of the wound electrode body 50. be done. Specifically, the non-aqueous electrolyte 90 flowing out from the inside of the wound electrode body 50 is collected in the one side portion 61 and the other side portion 62 of the insulating member 60 , thereby From the first end face 50j and the second end face 50k, due to capillary action, through the gaps between the positive electrode sheet 55, the negative electrode sheet 56, or the separator sheet 57 adjacent to each other in the radial direction of the wound electrode body 50, into the wound electrode body 50. It is thought that it became easier to return.

Therefore, in the non-aqueous electrolyte secondary battery 1 of the embodiment, compared to the non-aqueous electrolyte secondary battery of the comparative embodiment, the non-aqueous Nonuniformity (variation) in the salt concentration (concentration of Li salt) of the electrolytic solution 90 is less likely to occur, and variation (nonuniformity) in the resistance value occurs inside the wound electrode body 50 (in detail, in the axial direction DX). It is considered that it has become difficult to occur.

From the results of this high-rate charge/discharge test, in the non-aqueous electrolyte secondary battery 1 of the present embodiment, even when high-rate charge/discharge is performed, inside the wound electrode assembly 50 (in detail, in the axial direction DX) It can be said that the variation (unevenness) in the resistance value that occurs can be reduced, and the deterioration of battery characteristics (battery capacity, output characteristics, etc.) can be suppressed. That is, it can be said that the non-aqueous electrolyte secondary battery 1 of the present embodiment is a non-aqueous electrolyte secondary battery with good high-rate charge/discharge characteristics.

Although the present invention has been described above with reference to the embodiments, it goes without saying that the present invention is not limited to the above-described embodiments, and can be appropriately modified and applied without departing from the gist of the present invention.

For example, in the embodiment, the one side portion 61 and the other side portion 62 of the inner surface 60b of the insulating member 60 (electrically insulating film 60A) are subjected to corona treatment (hydrophilization treatment) to provide affinity for the non-aqueous electrolyte 90. heightened. However, the outer surface 60c (the surface opposite to the inner surface 60b) of the insulating member 60 (electrically insulating film 60A) may be subjected to corona treatment (hydrophilization treatment) in the same manner as the inner surface 60b.

1 Non-aqueous electrolyte secondary battery 10 Battery case 30 Positive electrode terminal member 40 Negative electrode terminal member 90 Non-aqueous electrolyte 50 Wound electrode body 50j First end surface 50k Second end surface 55 Positive electrode sheet 56 Negative electrode sheet 57 Separator sheet 60 Insulating member 60A Electrical insulating film 60b Inner surface 60c Outer surface 61 One side 62 Other side 65 Intermediate part AX Axis line DX Axial direction DX1 One side DX2 Other side

Claims (1)

A wound electrode body in which a strip-shaped positive electrode sheet, a strip-shaped negative electrode sheet, and a strip-shaped separator sheet are wound around an axis;
a battery case that houses the wound electrode body;
an insulating member made of an electrically insulating film in the form of a bag, wherein the wound electrode assembly is arranged inside the insulating member, and the insulating member is accommodated in the battery case;
A non-aqueous electrolyte secondary battery comprising:
The inner surface of the insulating member includes one side portion located on one side in the axial direction along the axis, the other side portion located on the other side in the axial direction, and the one side portion in the axial direction. and an intermediate portion located between the other side portion,
The non-aqueous electrolyte secondary battery, wherein the one side portion and the other side portion have a higher affinity for the non-aqueous electrolyte than the intermediate portion.

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