JP2020087832A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

To provide a non-aqueous electrolyte secondary battery capable of reducing the variation (unevenness) of a resistance value generated inside a wound electrode body (specifically, in the axial direction) even when high-rate charging/discharging is performed.SOLUTION: An insulating member 60 has a wound electrode body 50 arranged therein and is housed in a battery case 10. An inner surface 60b of the insulating member 60 includes one side portion 61 located on one side DX1 in the axial direction DX that is a direction along an axis AX, an other side portion 62 located on the other side DX2 in the axial direction DX, and an intermediate portion 65 located between the one side portion 61 and the other side portion 62 in the axial direction DX. The one side portion 61 and the other side portion 62 have higher affinity for a non-aqueous electrolyte solution 90 than the intermediate portion 65.SELECTED DRAWING: Figure 1

Description

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

Non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries have been attracting attention as power sources for mobile devices and as driving power sources for vehicles such as electric vehicles and hybrid vehicles. For example, Patent Document 1 discloses, as a non-aqueous electrolyte secondary battery, a strip-shaped positive electrode sheet, a strip-shaped negative electrode sheet, and a wound electrode body in which a strip-shaped separator sheet is wound around an axis, and the wound electrode body. A battery case accommodating the electrode body, and an insulating member having a bag-like shape of an electrically insulating film, wherein the wound electrode body is disposed inside the insulating member, and the insulating member is accommodated in the battery case. And a non-aqueous electrolytic solution contained in the wound electrode body, the non-aqueous electrolytic solution secondary battery is disclosed.

JP, 2016-219143, A

By the way, when high rate charging is performed on a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, the wound electrode body generates heat and expands, and further, the non-aqueous electrolyte solution contained inside the wound electrode body. Is heated and expands. Thereby, the non-aqueous electrolytic solution contained in the wound electrode body, from the end faces 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, In some cases, it leaked to the outside of the wound electrode body (through the negative electrode sheet or the separator sheet). The nonaqueous electrolytic solution that has flowed out of the wound electrode body spreads, for example, on the entire inner bottom surface of the insulating member, and is difficult to return to the inside of the wound electrode body.

For this reason, when high-rate charging/discharging is performed, the non-aqueous electrolytic solution flows out from the inside of the wound electrode body to the outside, so that the non-aqueous electrolyte is generated inside the wound electrode body (specifically, in the axial direction). In some cases, the salt concentration of the electrolytic solution (concentration of the electrolyte such as Li salt) varied. As a result, the resistance value may vary (uneven) inside the wound electrode body (specifically, in the axial direction). As a result, battery characteristics (battery capacity, output characteristics, etc.) may deteriorate.

The present invention has been made in view of the present situation, and even if high-rate charging/discharging is performed, there is a variation (unevenness) in the resistance value generated inside the wound electrode body (specifically, in the axial direction). It is an object to provide a non-aqueous electrolyte secondary battery that can be reduced.

One embodiment of the present invention, a strip-shaped positive electrode sheet, a strip-shaped negative electrode sheet, and a strip-shaped separator sheet, a wound electrode body wound around an axis line, and a battery case containing the wound electrode body, An insulating member in the form of a bag made of an electrically insulating film, wherein the wound electrode body is arranged inside the insulating member, and the insulating member housed in the battery case and the inside of the wound electrode body are also provided. In the non-aqueous electrolyte secondary battery comprising, and the non-aqueous electrolyte secondary battery, the inner surface of the insulating member, one side portion located on one side in the axial direction that is a direction along the axis, and the axis The other side portion located on the other side with respect to the direction, and an intermediate portion located between the one side portion and the other side portion with respect to the axial direction, the one side portion and the other side portion, the The non-aqueous electrolyte secondary battery has a higher affinity for the non-aqueous electrolyte than that of the intermediate portion.

The above-mentioned non-aqueous electrolyte secondary battery includes a wound electrode body, a battery case accommodating the wound electrode body, an insulating member in the shape of a bag made of an electrically insulating film, and a wound electrode body. And a non-aqueous electrolyte solution. Among them, the wound electrode body 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 line. The insulating member has the wound electrode body disposed inside the insulating member and is housed in the battery case.
In this non-aqueous electrolyte secondary battery, the inner surface of the insulating member in which the wound electrode body is arranged (the surface facing the wound electrode body side, that is, the surface facing the side opposite to the battery case side) is the wound electrode body. One side portion located on one side in the axial direction of the body (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 configured by an intermediate portion located between one side portion and the other side portion in the axial direction.

Furthermore, in the above-described non-aqueous electrolyte secondary battery, the one side portion and the other side portion of the inner surface of the insulating member have higher affinity for the non-aqueous electrolyte solution than the intermediate portion. Therefore, in the above-mentioned non-aqueous electrolyte secondary battery, when performing high-rate charging/discharging, the non-aqueous electrolyte contained inside the wound electrode body is When flowing out to the outside of the wound electrode body from the end surface located at the end surface (the first end surface located at one side and the second end surface located at the other side in the axial direction), the outflowing nonaqueous electrolytic solution is transferred to the inner surface of the insulating member. It becomes possible to collect (collect) on one side and the other side of which the affinity for the non-aqueous electrolyte is increased.

As described above, in the above-mentioned non-aqueous electrolyte secondary battery, the non-aqueous electrolyte that has flowed out of the wound electrode body is located at both ends of the wound electrode body in the axial direction on the inner surface of the insulating member. It is possible to collect (collect) the one side portion and the other side portion 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).

This makes it easier for the nonaqueous electrolytic solution that has flowed out of the wound electrode body to 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 nonaqueous electrolytic solution flowing out of the wound electrode body is a positive electrode sheet that is adjacent in the radial direction of the wound electrode body from the first end surface and the second end surface of the wound electrode body by a capillary phenomenon. It becomes easy to return to the inside of the wound electrode body through the gap between the negative electrode sheet or the separator sheet.

Therefore, in the above-mentioned non-aqueous electrolyte secondary battery, even when high-rate charging/discharging is performed, the salt concentration (Li salt etc.) of the non-aqueous electrolyte is inside the wound electrode body (specifically, in the axial direction). Of the electrolyte concentration) is less likely to occur, and the resistance value is less likely to vary within the wound electrode body (specifically, in the axial direction).
As described above, in the above-mentioned non-aqueous electrolyte secondary battery, even if high-rate charging/discharging is performed, the variation (unevenness) of the resistance value generated inside the wound electrode body (specifically, in the axial direction). Can be reduced.

In addition, one 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 one side of the first end surface which is located on one side in the axial direction, and It is composed of parts that are close to each other (close to the other side). The other side portion of the inner surface of the insulating member is, for example, a portion of the wound electrode body disposed inside that 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 parts that are close to each other (close to one side). The end surface of the wound electrode body is a surface formed by at least one of the end surfaces of the positive electrode sheet, the negative electrode sheet, and the separator sheet that is exposed to the outside, and the axial direction of the wound electrode body. Is the surface facing.

FIG. 3 is a partial cross-sectional view of the non-aqueous electrolyte secondary battery according to the embodiment. It is a perspective view of the wound electrode body concerning embodiment. It is a perspective view of the insulating member concerning embodiment. It is a top view of the electrically insulating film which comprises the same insulating member. It is a figure which shows the state by which the wound electrode body was arrange|positioned inside the insulating member. It is a figure which shows the result of a high rate charge/discharge test.

(Embodiment)
Next, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a non-aqueous electrolyte secondary battery 1 of the present embodiment is a lithium ion secondary battery including a rectangular parallelepiped battery case 10 and a wound electrode body 50 housed inside the battery case 10. It is a battery. The battery case 10 includes a rectangular box-shaped housing portion 11 having an opening 11d, and a battery case lid 15 with a terminal having a lid 13 that closes the opening 11d of the housing portion 11. The accommodating portion 11 and the lid 13 are integrally formed by welding all around.

The wound electrode body 50 has an oval cross section, and a separator sheet 57 is interposed between a strip-shaped positive electrode sheet 55 and a strip-shaped negative electrode sheet 56, and these are wound around an axis AX. Is a wound electrode body (see FIGS. 1 and 2). The wound electrode body 50 is located on one side (left side in FIG. 1) of the axial direction DX (direction along the axis AX, left-right direction in FIG. 1), and only a part of the positive electrode sheet 55 is spirally formed. The overlapping positive electrode winding portion 55b and the negative electrode winding portion 56b located on the other side (right side in FIG. 1) and overlapping only a part of the negative electrode sheet 56 in a spiral shape.

A portion of the wound electrode body 50 located between the positive electrode wound portion 55b and the negative electrode wound portion 56b in the axial direction DX is referred to as an electrode body intermediate portion 50g. Further, in the positive electrode sheet 55, a positive electrode mixture layer containing a positive electrode active material is formed in a portion excluding the positive electrode winding portion 55b. Similarly, in the negative electrode sheet 56, a negative electrode mixture layer containing a negative electrode active material is formed in a portion excluding the negative electrode winding portion 56b. The non-aqueous electrolytic solution 90 is contained inside the wound electrode body 50. The non-aqueous electrolytic solution 90 is a non-aqueous solvent prepared by mixing EC (ethylene carbonate), DMC (dimethyl carbonate), and EMC (ethyl methyl carbonate) with lithium hexafluorophosphate, which is a Li salt, dissolved in a non-aqueous solvent. It is a water electrolyte.

The terminal-equipped battery case lid 15 includes 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 penetrating the lid 13 are formed at both ends in the axial direction DX. A safety valve 13j is provided at the center of the lid 13 in the longitudinal direction X. In addition, a liquid injection port 13n for injecting the non-aqueous electrolyte solution 90 into the accommodating portion 11 (specifically, the insulating member 60) is formed between the safety valve 13j and the through hole in the lid body 13. Has been done. The injection port 13n is sealed by an injection plug 13m (see FIG. 1).

The positive electrode terminal member 30 is composed of a positive electrode connecting member 35, a positive electrode external terminal 37, and a positive electrode fastening member 39 (see FIG. 1). Of these, the positive electrode connecting member 35 is made of metal, is connected to the positive electrode winding portion 55b of the wound electrode body 50, and extends to the outside through the through hole of the lid body 13. The positive electrode external terminal 37 is made of metal, is located above the lid 13 (outside the battery case 10), and is electrically connected to the positive electrode connecting member 35 outside the battery case 10. The positive electrode fastening member 39 is a bolt made of metal, is located 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 includes a negative electrode connecting member 45, a negative electrode external terminal 47, and a negative electrode fastening member 49 (see FIG. 1). Of these, the negative electrode connecting member 45 is made of metal, is connected to the negative electrode winding portion 56b of the wound electrode body 50, and extends to the outside through the through hole of the lid body 13. The negative electrode external terminal 47 is made of metal, is located above the lid 13 (outside the battery case 10), and is electrically connected to the negative electrode connecting member 45 outside the battery case 10. The negative electrode fastening member 49 is a bolt made of metal, is located 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 composed of an electrically insulating film 60A, and is provided with an insulating member 60 in which the electrically insulating film 60A is formed into a rectangular bag shape (FIGS. 1, 3, and 4). The insulating member 60 of the present embodiment is manufactured by bending the electrically insulating film 60A along a bending line shown by a broken line in FIG. 4 to form a rectangular bag shape and heat-sealing the overlapped portions.

The insulating member 60 has the wound electrode body 50 arranged (accommodated) inside the insulating member 60, and is accommodated in the battery case 10. Note that FIG. 3 is a perspective view of the insulating member 60. FIG. 4 is a plan view (corresponding to a developed view of the insulating member 60) of the electrically insulating film 60A forming the insulating member 60. Further, FIG. 5 is a schematic perspective view showing a state where the wound electrode body 50 is arranged inside the insulating member 60 in the non-aqueous electrolyte secondary battery 1. In addition, in FIG. 5, illustration of the battery case lid 15 with terminals is omitted.

In the non-aqueous electrolyte secondary battery 1 of the present embodiment, as shown in FIGS. 1 and 5, the inner surface 60b of the insulating member 60 in which the wound electrode body 50 is arranged is the axial direction of the wound electrode body 50. One side portion 61 located on one side DX1 (left side in FIG. 1) with respect to DX (direction along the axis AX of the wound electrode body 50) and the other side DX2 with respect to the axial direction DX of the wound electrode body 50 (FIG. 1). The other side portion 62 located on the right side of FIG. 2) and the intermediate portion 65 located between the one side portion 61 and the other side portion 62 in the axial direction DX of the wound electrode body 50.

The inner surface 60b of the insulating member 60 is a surface facing the wound electrode body 50 side (inner side) in the non-aqueous electrolyte secondary battery 1, that is, a surface facing the side opposite to the battery case 10 side (outer side). is there. In addition, 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. Further, in FIG. 5, 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 diagonal lines. The same applies to FIGS. 3 and 4.

Further, in the present embodiment, the one side portion 61b of the inner surface 60b of the insulating member 60 has the first end surface 50j (the end surface of the positive electrode winding portion 55b is swirled at the first end surface 50j facing the one side DX1 in the axial direction DX of the wound electrode body 50). (A portion that overlaps in a circular shape) and a portion that is located on the one side DX1 and a portion that is close to this (close to the other side DX2) (see FIGS. 1 and 5). Specifically, the one side portion 61 of the inner surface 60b of the insulating member 60 includes a first surface 61b that faces the first end surface 50j of the wound electrode body 50 in the axial direction DX, and the positive electrode wound portion of the wound electrode body 50. The second surface 61c that faces the first side surface (the side surface on the front side in FIGS. 1 and 5) of the portion 55b, and the second side surface (the back side surface in FIGS. 1 and 5) that faces the positive electrode winding portion 55b. And a fourth surface 61f that faces the arc-shaped bottom surface of the positive electrode winding portion 55b (see FIG. 5).

Further, the other side portion 62 of the inner surface 60b of the insulating member 60 is the 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 surface of the negative electrode wound portion 56b overlaps spirally). It is composed of a part located on the other side DX2 and a part adjacent thereto (closer to the 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 that faces 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 that faces the first side surface (the front side surface in FIGS. 1 and 5) of the portion 56b, and the second side surface (the back side surface in FIGS. 1 and 5) of the negative electrode winding portion 56b. And a fourth surface 62f that faces the arc-shaped bottom surface of the negative electrode winding portion 56b (see FIG. 5).

Further, the intermediate portion 65 of the inner surface 60b of the insulating member 60 has a first surface 65b that faces the first side surface (the front side surface 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 (the back side surface in FIGS. 1 and 5) of the electrode body intermediate portion 50g, and a third surface 65d that faces the arc-shaped bottom surface of the electrode body intermediate portion 50g (FIGS. 5).

By the way, conventionally, for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, when high rate charging or high rate charge/discharge is performed, the wound electrode body generates heat and expands, and further, inside the wound electrode body. The contained non-aqueous electrolyte solution was sometimes heated and expanded. Thereby, the non-aqueous electrolytic solution contained in the wound electrode body, from the end faces 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, In some cases, it may flow out of the wound electrode body (through the negative electrode sheet or the separator sheet). The non-aqueous electrolyte solution that has flowed out of the wound electrode body spreads, for example, on the entire inner bottom surface of the insulating member and is difficult to return to the inside of the wound electrode body.

For this reason, when high-rate charging/discharging is performed, the non-aqueous electrolytic solution flows out from the inside of the wound electrode body to the outside, so that the non-aqueous electrolyte is generated inside the wound electrode body (specifically, in the axial direction). In some cases, there was unevenness in the salt concentration of the electrolytic solution (concentration of the electrolyte such as Li salt). As a result, the resistance value may vary (uneven) inside the wound electrode body (specifically, in the axial direction). As a result, 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 60b of the insulating member 60 are different from the intermediate portion 65 in the non-aqueous electrolyte solution 90. Has a high affinity for. More specifically, in the present embodiment, the insulating member 60 is formed on the inner surface of a resin film having a low affinity (low affinity) with the non-aqueous electrolyte 90 (for example, a resin film made of polyolefin such as polypropylene or polyethylene). Of the 60b, the portions to be the one side portion 61 and the other side portion 62 are configured by an electrically insulating film 60A (see FIG. 4) having a high affinity for the non-aqueous electrolyte solution 90 by corona treatment. .

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

Therefore, 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 60b of the insulating member 60 have a relatively high affinity for the non-aqueous electrolyte solution 90 ( It is also hydrophilic), and the intermediate portion 65 has a relatively low affinity (also hydrophobic) for the non-aqueous electrolytic solution 90.

Therefore, in the non-aqueous electrolyte secondary battery 1 of the present embodiment, the non-aqueous electrolyte solution 90 contained in the wound electrode body 50 when the high-rate charge/discharge is performed is the wound electrode body 50. Out of the first end surface 50j located on one side DX1 and the second end surface 50k located on the other side DX2 of the axial direction DX, when flowing out to the outside of the wound electrode body 50 (inside the insulating member 60). The nonaqueous electrolytic solution 90 can be collected (stored) in the one side portion 61 and the other side portion 62 of the inner surface 60b of the insulating member 60, which have high affinity for the nonaqueous electrolytic solution 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 wound electrode body 50 on the inner surface 60b of the insulating member 60. One side portion 61 and the other side portion located near the end faces located at both ends in the axial direction DX (the first end face 50j located on the one side DX1 and the second end face 50k located on the other side DX2 in the axial direction DX). Can be collected (stored) in 62.

As a result, the non-aqueous electrolyte solution 90 flowing out of the wound electrode body 50 easily returns to the inside of the wound electrode body 50 through the first end surface 50j and the second end surface 50k of the wound electrode body 50. Specifically, the non-aqueous electrolyte solution 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 wound electrode body. From the first end surface 50j and the second end surface 50k of 50, the wound electrode body 50 passes through the gap between the positive electrode sheet 55, the negative electrode sheet 56, and the separator sheet 57 that are adjacent in the radial direction of the wound electrode body 50 due to the capillary phenomenon. It becomes easier to return to the inside of.

Therefore, in the non-aqueous electrolyte secondary battery 1 according to the present embodiment, the non-aqueous electrolyte solution 90 is generated inside the wound electrode body 50 (specifically, in the axial direction DX) even when high-rate charging/discharging is performed. Variations in the salt concentration (concentration of lithium hexafluorophosphate that is a Li salt) are less likely to occur, and the resistance value varies within the wound electrode body 50 (specifically, in the axial direction DX) ( Unevenness is less likely to occur.
As described above, in the non-aqueous electrolyte secondary battery 1 of the present embodiment, the resistance value generated inside the wound electrode body 50 (specifically, in the axial direction DX) even when performing high-rate charging/discharging. Can be reduced.

(High-rate charge/discharge test)
Regarding the non-aqueous electrolyte secondary battery 1 of the present embodiment, cycle charge/discharge was performed at a current value of 13 C, and the resistance value inside the wound electrode body 50 was measured. In this test, the resistance value is measured at a plurality of positions at different positions in the axial direction DX over the entire axial direction DX of the wound electrode body 50 (specifically, the electrode body intermediate portion 50g). The results are shown in FIG. 6 (broken line curve). Note that 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.

Further, as a non-aqueous electrolyte secondary battery (not shown) of the comparative embodiment, the affinity of the inner surface of the insulating member for the non-aqueous electrolyte 90 is different from that of the non-aqueous electrolyte secondary battery 1 of the embodiment. Non-aqueous electrolyte secondary batteries having different only were prepared. Specifically, in the comparative embodiment, the inner surface of the electrically insulating film is not subjected to corona treatment, and the inner surface of the electrically insulating film has a portion serving as one side portion and a portion serving as the other side portion, an intermediate portion. The 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 That is, in the comparative embodiment, as the insulating member, the entire inner surface is formed of an electrically insulating film having a low affinity (also hydrophobic) for the non-aqueous electrolytic solution 90.

Therefore, in the non-aqueous electrolyte secondary battery of the comparative form, the affinity for the non-aqueous electrolyte 90 on one side portion and the other side portion of the inner surface of the insulating member is higher than that of the non-aqueous electrolyte secondary battery 1 of the embodiment. It's getting low. Specifically, in the non-aqueous electrolyte secondary battery of the comparative form, the one side portion and the other side portion of the inner surface of the insulating member have low affinity to the non-aqueous electrolyte solution 90, like the intermediate portion. (It is also hydrophobic). That is, in the comparative embodiment, an insulating member whose entire inner surface has a low affinity (also hydrophobic) for the non-aqueous electrolyte 90 is used as the insulating member. Also in the non-aqueous electrolyte secondary battery of this comparative example, cycle charge/discharge was performed in the same manner as the non-aqueous electrolyte secondary battery 1 of the embodiment, and the resistance value inside the wound electrode body 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 internal resistance value of the wound electrode body 50 (specifically, the axis It was possible to reduce the variation (unevenness) in the internal resistance value in the direction DX. More specifically, in the non-aqueous electrolyte secondary battery 1 of the embodiment, the maximum internal resistance value of the wound electrode body 50 is significantly reduced as compared with the non-aqueous electrolyte secondary battery of the comparative embodiment. I was able to do it. The variation in the internal resistance value of the wound electrode body 50 correlates with the variation in the salt concentration (Li salt concentration) of the non-aqueous electrolyte solution 90 inside the wound electrode body.

In the non-aqueous electrolyte secondary battery 1 of the embodiment, the reason why the variation (unevenness) of the internal resistance value of the wound electrode body 50 can be reduced as compared with the non-aqueous electrolyte secondary battery of the comparative embodiment is. , Can be thought of as follows.

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

Therefore, in the non-aqueous electrolyte secondary battery of the comparative embodiment, the non-aqueous electrolyte flows out from the inside of the wound electrode body 50 to the outside, so that the inside of the wound electrode body 50 (specifically, the axial direction). Regarding DX), it is considered that the unevenness (variation) of the salt concentration (concentration of Li salt) of the non-aqueous electrolytic solution 90 became large. It is considered that, as a result, a large variation (unevenness) in the resistance value occurred inside the wound electrode body 50 (specifically, in the axial direction DX).

On the other hand, in the non-aqueous electrolyte secondary battery 1 of the embodiment, the non-aqueous electrolysis is performed for 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 a relatively low affinity for the non-aqueous electrolyte 90 (also hydrophobic).

Therefore, in the non-aqueous electrolyte secondary battery 1 of the embodiment, in the high rate charge/discharge test, the non-aqueous electrolyte 90 contained in the wound electrode body 50 is the first end surface of the wound electrode body 50. When the nonaqueous electrolytic solution 90 flows out of the wound electrode body 50 (inside the insulating member 60) from the second end surface 50k and the second end surface 50k, the nonaqueous electrolytic solution 90 in the inner surface 60b of the insulating member 60 is discharged. It is considered that they were able to be collected (stored) 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 surface 50j and the second end surface 50k of the wound electrode body 50. It is thought that they were able to collect (collect).

It is considered that, as a result, the nonaqueous electrolytic solution 90 flowing out of the wound electrode body 50 is likely to return to the inside of the wound electrode body 50 through the first end surface 50j and the second end surface 50k of the wound electrode body 50. Be done. Specifically, the non-aqueous electrolyte solution 90 that has flowed from the inside to the outside 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, so that From the first end surface 50j and the second end surface 50k to the inside of the wound electrode body 50 through the gap between the positive electrode sheet 55, the negative electrode sheet 56, or the separator sheet 57 that are adjacent in the radial direction of the wound electrode body 50 due to the capillary phenomenon. It is thought that it became easier to return.

Therefore, in the non-aqueous electrolyte secondary battery 1 of the embodiment, as compared with the non-aqueous electrolyte secondary battery of the comparative embodiment, the non-aqueous electrolyte secondary battery 1 is nonaqueous in the wound electrode body 50 (specifically, in the axial direction DX). Variations in the salt concentration (concentration of Li salt) of the electrolytic solution 90 are less likely to occur, and variations (unevenness) in the resistance value occur inside the wound electrode body 50 (specifically, in the axial direction DX). It is thought that it became 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 was performed, inside the wound electrode body 50 (specifically, in the axial direction DX). It can be said that the variation (unevenness) of the generated resistance value can be reduced and the deterioration of the 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 having good high-rate charge/discharge characteristics.

Although the present invention has been described above according to the embodiment, it goes without saying that the present invention is not limited to the above embodiment and can be appropriately modified and applied without departing from the scope of the invention.

For example, in the embodiment, the corona treatment (hydrophilization treatment) is performed on 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) to make it compatible with the non-aqueous electrolyte solution 90. I have a high quality. However, the outer surface 60c (the surface opposite to the inner surface 60b) of the insulating member 60 (electrically insulating film 60A) may be corona-treated (hydrophilized) 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 Terminal Member 90 Non-Aqueous Electrolyte Solution 50 Winding Electrode 50j First End Face 50k Second End Face 55 Positive Electrode Sheet 56 Negative Sheet 57 Separator Sheet 60 Insulating Member 60A Electrically insulating film 60b Inner surface 60c Outer surface 61 One side part 62 Other side part 65 Intermediate part AX Axis DX Axis direction DX1 One side DX2 Other side

Claims (1)

A strip-shaped positive electrode sheet, a strip-shaped negative electrode sheet, and a strip-shaped separator sheet, and a wound electrode body wound around an axis,
A battery case accommodating the wound electrode body,
An insulating member in the form of a bag of an electrically insulating film, wherein the wound electrode body is disposed inside the insulating member, and an insulating member housed in the battery case,
In a non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte contained inside the wound electrode body,
The inner surface of the insulating member has one side portion located on one side in the axial direction that is a 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 in which the one side portion and the other side portion have higher affinity for the non-aqueous electrolyte solution than the intermediate portion.

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