JP2015115124A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology for preventing an oxidation reduction reaction from being varied during charging/discharging.SOLUTION: In a nonaqueous electrolyte secondary battery, an outermost peripheral laminate in an arc-shaped part 10b to which winding ends 11a, 12b and 13b are connected, between arc-shaped parts 10a and 10b in both ends of an electrode body 10 includes a deactivation region 20 in which the activity of a cathode active material applied to a cathode sheet 12 is lost, at an another side in a width direction with respect to one side of an anode sheet 13 to which an anode collector part 5 is fixed, in the width direction. In the deactivation region 20, the oxidation reduction reaction does not occur during charging/discharging. Therefore, even if winding is loosened at the other side of the anode sheet 13 in the width direction in the arc-shaped part 10b, since the portion where winding is loosened is included in the deactivation region 20, there is no oxidation reduction reaction originally. Thus, even if winding is loosened at the other side of the anode sheet 13 in the width direction, the oxidation reduction reaction during charging/discharging is not affected, such that the oxidation reduction reaction during charging/discharging is prevented from being varied by loosening winding in the arc-shaped part 10b.

Description

  The technology disclosed in the present specification relates to a non-aqueous electrolyte secondary battery having an electrode body in which a positive electrode sheet and a negative electrode sheet are wound in a flat shape with a separator interposed therebetween.

  A non-aqueous electrolyte secondary battery having an electrode body in which a laminate of a positive electrode sheet and a negative electrode sheet with a separator interposed therebetween is wound in a flat shape is known. An example of the technique is disclosed in Patent Document 1 below. There is technology. The electrode body wound in a flat shape has arc-shaped portions formed at both ends viewed from the winding axis (Patent Document 1; FIG. 1B). For example, as shown in FIG. 5A, the electrode body is formed by alternately stacking the positive electrode sheets 120 and the negative electrode sheets 130 such as the negative electrode sheet 130, the separator 110, the positive electrode sheet 120,. Is wound. The positive electrode sheet 120 includes a positive electrode plate 121 and a positive electrode mixture layer 123 applied on both surfaces thereof. The negative electrode sheet 130 includes a negative electrode plate 131 and a negative electrode mixture layer 133 applied on both surfaces thereof. As shown in FIG. 5B, the positive electrode sheet 120 and the negative electrode sheet 130 are stacked while being shifted by a predetermined width in their width direction. In the range of the predetermined width, a positive electrode current collector or a negative electrode current collector can be attached, and a negative electrode mixture or a positive electrode mixture uncoated part 120a or a negative electrode mixture uncoated part 130a where no negative electrode mixture or positive electrode mixture is applied. Is formed.

  As shown in FIGS. 6A and 6B, in the electrode body 100, the positive electrode current collector 140 is a positive electrode mixture uncoated part 120 a of the positive electrode sheet 120 at the end of winding (winding end) of the separator 110 or the like. (Reference numeral 143). Further, the negative electrode current collector 150 is welded and fixed to the negative electrode mixture uncoated portion 130a of the negative electrode sheet 130 (reference numeral 153). The positive current collector 140 is connected to the positive external terminal 170, and the negative current collector 150 is connected to the negative external terminal 180. The positive electrode current collector 140 and the negative electrode current collector 150 are fixed so that the winding ends of the positive electrode sheet 120 and the negative electrode sheet 130 together with the separator 110 cannot be unwound.

JP 2011-171250 A

  Here, when attention is paid to the negative electrode sheet 130 at the winding end of the electrode body 100, even if one side in the width direction of the negative electrode sheet 130 is fixed by the negative electrode current collector 150, what is the other side K in the width direction of the negative electrode sheet 130? It is not fixed to crab. Therefore, the negative electrode sheet 130 may be loosened on the other side K in the width direction of the negative electrode sheet 130. For example, the electrode body 100 repeats thermal expansion and contraction during charging and discharging. In that case, the separator 110 is loosened, and the winding of the negative electrode sheet 130 can be loosened together with the separator 110. In particular, among the arc-shaped portions formed at both ends of the flat shape, the negative electrode sheet 130 is easy to loosen on the other side K in the width direction of the arc-shaped portion to which the winding ends are connected (a dashed-dotted line range indicated by the symbol X). Such loosening of the negative electrode sheet 130 can form a gap SP between the negative electrode sheet 130 and the positive electrode sheet 120 (see FIG. 6A). For example, when the nonaqueous electrolyte secondary battery is a lithium ion battery, lithium may be deposited due to variations in the oxidation-reduction reaction during charge / discharge due to the gap SP. This specification provides the technique which suppresses the dispersion | variation in the oxidation reduction reaction at the time of charging / discharging.

  The nonaqueous electrolyte secondary battery disclosed in this specification has an electrode body in which a laminate of a positive electrode sheet and a negative electrode sheet with a separator interposed therebetween is wound in a flat shape. The electrode body has arc-shaped portions at both ends of the flat shape (both ends as viewed from the axial direction of the winding), and the arc that is connected to the winding ends (winding ends) of the arc-shaped portions at both ends of the electrode body. Deactivation region where the outermost laminate in the shape part loses the activity of the positive electrode active material applied to the positive electrode sheet on the other side in the width direction with respect to one side in the width direction of the negative electrode sheet to which the negative electrode current collector is fixed It has. In other words, the position of the deactivation region is the end portion on the positive electrode current collector portion side of the region where the positive electrode sheet, the negative electrode sheet, and the separator overlap in the stack of arc-shaped portions connected to the winding end. A region where the positive electrode sheet, the negative electrode sheet, and the separator overlap is generally referred to as a coating portion, and an active material is applied to a portion corresponding to this region of the positive electrode sheet and the negative electrode sheet.

  In the deactivation region described above, no oxidation-reduction reaction occurs during charge / discharge. For example, when the nonaqueous electrolyte secondary battery is a lithium ion battery, transfer of lithium ions is blocked. As a result, in the arc-shaped portion where the winding end is connected, even if winding looseness occurs on the other side in the width direction of the negative electrode sheet where the negative electrode current collector portion is not fixed, the portion where the winding looseness occurs is an inactive region. There is no redox reaction from the beginning. Therefore, even if winding looseness occurs on the other side in the width direction of the negative electrode sheet, there is no influence on the oxidation-reduction reaction during charge / discharge. Therefore, the variation of the oxidation-reduction reaction at the time of charging / discharging due to such loosening of the arc-shaped portion is suppressed. In addition, typically, the negative electrode sheet of a laminated body is wound outside the positive electrode sheet. The electrode body has a flat shape at both ends in a direction intersecting the winding axis of the electrode body. The typical structure for losing the activity of the positive electrode active material is that the active material is not applied to the positive electrode sheet in the above range (the end on the positive electrode current collector side of the region where the positive electrode sheet, the negative electrode sheet, and the separator overlap). Alternatively, the positive electrode sheet is subjected to a surface treatment that prevents the movement of ions.

  Details of the technology disclosed in this specification and further improvements will be described in the embodiments of the present invention.

  The present specification provides a technique for suppressing variation in oxidation-reduction reaction during charge / discharge in a non-aqueous electrolyte secondary battery.

It is a perspective view which shows the example of the external appearance structure of the nonaqueous electrolyte secondary battery of an Example. It is sectional drawing which shows the example of an internal structure of a nonaqueous electrolyte secondary battery. 2A is a cross-sectional view in a direction orthogonal to the winding axis of the electrode body, and FIG. 2B is a cross-sectional view taken along line 2B-2B in FIG. 2A. It is a perspective view which shows the structure outline | summary of an electrode body. It is explanatory drawing which shows the structure details of an electrode body. 4A is a side view of the electrode body, and FIG. 4B is an enlarged view of a portion indicated by a broken line region 4B in FIG. 4A. It is explanatory drawing which shows the lamination example of an electrode body. FIG. 6A is a cross-sectional view illustrating a configuration example of a conventional nonaqueous electrolyte secondary battery, and FIG. 6B is a perspective view illustrating a configuration example of a conventional electrode body.

  The nonaqueous electrolyte secondary battery of the embodiment will be described with reference to the drawings. First, with reference to FIG.1 and FIG.2, the structure outline | summary of the nonaqueous electrolyte secondary battery 1 is demonstrated. In FIG. 1, the perspective view which shows the example of the external appearance structure of the nonaqueous electrolyte secondary battery 1 is shown. FIG. 2 is a cross-sectional view showing an example of the internal configuration of the nonaqueous electrolyte secondary battery 1.

  The external appearance of the nonaqueous electrolyte secondary battery 1 is mainly composed of a battery case 2 having a deep and thin box shape with a deep bottom, a positive external terminal 7 and a negative external terminal 8 protruding from above the battery case 2, and The sleeve 9 is configured to support the terminals 7 and 8. In the present embodiment, the nonaqueous electrolyte secondary battery 1 is a square sealed lithium ion secondary battery. The battery case 2 includes, for example, a housing portion 2a formed of a metal plate in a bottomed rectangular parallelepiped shape by deep drawing and a metal lid portion 2b that seals the opening of the housing portion 2a.

  As shown in FIG. 2, the electrode body 10 and the like are accommodated inside the battery case 2. The positive electrode external terminal 7 and the negative electrode external terminal 8 are round bar-shaped metal terminals that are used when electric energy is taken out from the electrode body 10 or supplied to the electrode body 10 from the outside. The sleeve 9 is a cylindrical holding body that is interposed between the positive electrode external terminal 7 and the negative electrode external terminal 8 and the battery case 2 and mechanically supports the terminals 7 and 8. In this embodiment, since the battery case 2 is made of metal, the sleeve 9 is formed of a resin material that can be electrically insulated. 2A is a view in the direction of arrow X in which the battery case 2 is cut in the lateral direction from a substantially intermediate portion between the positive electrode external terminal 7 and the negative electrode external terminal 8 in the YZ plane in the coordinate system shown in FIG. It is sectional drawing. FIG. 2B is a cross-sectional view taken in the direction of the arrow Y in which the battery case 2 is cut in the longitudinal direction on the XZ plane along line 2B-2B shown in FIG.

  The electrode body 10 is a laminated wound body in which a laminated body of a positive electrode sheet 12 and a negative electrode sheet 13 with a separator 11 interposed therebetween is wound in a flat shape. As described with reference to FIG. 5 in the “Background Art” section, the electrode body 10 includes the negative electrode sheet 13, the separator 11, the positive electrode sheet 12,... Sheets 13 are alternately stacked and wound. One set of the separator 11, the negative electrode sheet 13, the separator 11, and the positive electrode sheet 12 is the smallest unit of the laminated body from the radially outer side to the inner side of the winding.

  From here, it demonstrates, referring FIG. 5 in addition to FIG.1 and FIG.2. The numbers in parentheses correspond to the symbols shown in FIG. The positive electrode sheet 12 and the negative electrode sheet 13 are configured similarly to the positive electrode sheet 120 and the negative electrode sheet 130 described with reference to FIG. That is, the positive electrode sheet 12 (120) is composed of the positive electrode plate (121) and the positive electrode mixture layer (123) coated on both surfaces thereof, and the negative electrode sheet 13 (130) is composed of the negative electrode plate (131) and both surfaces thereof. Each of the coated negative electrode mixture layers (133) is constituted. Further, as shown in FIG. 5B, the positive electrode sheet 12 (120) and the negative electrode sheet 13 (130) are stacked while being shifted by a predetermined width in the width direction thereof. In the range of the predetermined width, uncoated portions 12a and 13a where no negative electrode mixture or positive electrode mixture is applied are formed. The uncoated portions 12 a and 13 a do not overlap with the separator 110. In other words, the positive electrode sheet 120 and the negative electrode sheet 130 are coated with a mixture (active material) in a region overlapping with the separator 110. The area where the mixture is applied is called the coating part.

  Thus, the electrode body 10 is provided with the uncoated part 12a which does not apply a positive mix to the one end side of a winding axis direction. In the present embodiment, the positive electrode current collector 4 is welded and fixed to the uncoated part 12 a located at the flat part 10 c of the electrode body 10 by the weld part 4 a, and the positive electrode sheet 12 is interposed via the positive electrode current collector 4. Are electrically connected to the positive external terminal 7. On the other hand, an uncoated portion 13a where no negative electrode mixture is applied exists on the other end side in the winding axis direction. The negative electrode current collector 5 is welded and fixed to the uncoated part 13 a located in the flat part 10 c by a weld part 5 a, and the negative electrode sheet 13 is electrically connected to the negative electrode external terminal 8 via the negative electrode current collector 5. It is connected. The positive electrode current collector 4 and the negative electrode current collector 5 are strip-shaped metal plates and are bent in an inverted L shape (see FIG. 2A). The shapes of the current collectors 4 and 5 are determined by the relationship between the winding thickness of the electrode body 10 and the protruding positions of the positive electrode external terminal 7 and the negative electrode external terminal 8.

  The electrode body 10 contains a non-aqueous electrolyte in the laminated body wound in this way. For example, a solution obtained by dissolving lithium hexafluorophosphate in a non-aqueous solvent in which EC (ethylene carbonate), DMC (dimethyl carbonate) and EMC (ethyl methyl carbonate) are mixed is used as the non-aqueous electrolyte. Moreover, the positive electrode active material applied to the positive electrode mixture layer of the positive electrode sheet 12 is, for example, lithium nickelate. The negative electrode active material applied to the negative electrode mixture layer of the negative electrode sheet 13 is, for example, graphite. The separator 11 is a porous sheet made of, for example, polypropylene.

  The flat electrode body 10 includes arc-shaped portions 10a and 10b at both ends in the direction intersecting the winding axis, and the cross-sectional shape in the radial direction is an elongated oval shape (FIG. 2A )reference). By the way, in the electrode body 10 configured in this manner, the separator 11 is positioned on the outermost side (outermost circumference) at the end of winding of the laminated body, that is, at the winding end. In FIG. 3, the perspective view showing the structure outline | summary of the electrode body 10 is shown. FIG. 4A is an explanatory diagram showing the configuration details of the electrode body 10, and FIG. 4B is an enlarged view of a broken line region 4B shown in FIG. 4A. As can be seen from these drawings, the separator 11 has a winding end 11 a extending to one arc-shaped portion 10 a of the electrode body 10, whereas the winding end 12 b of the positive electrode sheet 12 and the negative electrode sheet 13 The winding end 13b stays up to the flat portion 10c of the electrode body 10 and does not extend to the one arc-shaped portion 10a. As described above, in the positive electrode sheet 12, the winding end 12 b is fixed by the welding portion 4 a of the positive electrode current collector 4, and in the negative electrode sheet 13, the winding end 13 b is fixed in the negative electrode current collector. It is for fixing with the 5 weld parts 5a. In FIG. 3, the alternate long and short dash line indicated by the symbol J indicates the winding axis of the electrode body 10.

  Thus, the separator 11 located on the outermost periphery extends the winding end 11a beyond the winding end 13b of the negative electrode sheet 13 in the direction of the arc-shaped portion 10a, so that the winding of the negative electrode sheet 13 is difficult to loosen. It is configured as follows. However, although one side in the width direction of the negative electrode sheet 13 is fixed by the negative electrode current collector 5, the other side L in the width direction of the negative electrode sheet 13 is not fixed to anything. Therefore, since the negative electrode sheet 13 positioned on the other side L in the width direction of the separator 11 is only restrained by the separator 11, the close contact due to winding remains in the restraining force by the separator 11. Therefore, the negative electrode sheet 13 may be loosened on the other side L in the width direction of the negative electrode sheet 13, and the other side L in the width direction of the arc-shaped portion 10b to which the winding ends 11a, 12b, 13b of the laminate are connected is particularly loose. Easy (dotted line range indicated by symbol Y). In other words, the other side L in the width direction is an end portion on the side of the positive electrode current collector 4 in a region where the positive electrode sheet 12, the negative electrode sheet 13, and the separator 11 overlap.

  For example, when the electrode body 100 repeatedly expands and contracts during the initial charging of the nonaqueous electrolyte secondary battery 1, the separator 11 is loosened on the other side L in the width direction, and the anode 11 Winding can also loosen. As described in [Problems to be Solved by the Invention], the looseness of the negative electrode sheet 13 is caused by the gap SP (see FIG. 6A) formed between the negative electrode sheet 13 and the positive electrode sheet 12. There is a possibility of causing precipitation of lithium due to variation in the oxidation-reduction reaction during charging and discharging. The loosening of the negative electrode sheet 13 can be made difficult to occur by, for example, winding the outermost separator 11 and the negative electrode sheet 13 one more time (double winding). However, such double winding causes an increase in the thickness, weight and cost of the electrode body 10.

  Therefore, in the electrode body 10 of the present embodiment, the arc-shaped portion 10b of the electrode body 10 includes a deactivation region 20 that loses the activity of the positive electrode mixture (positive electrode active material) applied to the positive electrode sheet 12 (FIG. 3 and the cross-hatching range shown in FIG. As a result, in the deactivated region 20, since the exchange of lithium ions is blocked, an oxidation reaction during discharge or a reduction reaction during charging does not occur. Therefore, even if loosening of the negative electrode sheet 13 occurs on the other side L in the width direction of the arc-shaped portion 10b, there is no effect on the oxidation-reduction reaction during charging / discharging. It is possible to suppress variation in the oxidation-reduction reaction.

  The deactivation region 20 is located on the other side L in the width direction of the electrode body 10 in the arc-shaped part 10b connected to the winding ends 11a, 12b, and 13b among the arc-shaped parts 10a and 10b at both ends of the electrode body 10. . In other words, the deactivation region 20 is a positive electrode current collector in a region where the positive electrode sheet 12, the negative electrode sheet 13, and the separator 11 overlap in the laminate of the arc-shaped portions 10 b connected to the winding ends 11 a, 12 b, and 13 b. 4 is an end on the side of 4 (the side of the uncoated portion 12a of the positive electrode). For example, in the positive electrode sheet 12 facing the negative electrode sheet 13 located on the outermost periphery, a part of the boundary line between the coated part of the positive electrode active material (dotted painted range shown in FIG. 4B) and the uncoated part 12a Then, a triangular range having sides of a part along the outermost edge of the curved surface portion of the arc-shaped portion 10 b is set in the inactivated region 20. The “part” of the boundary line is, for example, a portion included in a curved surface range by the arc-shaped portion 10b. The “part” of the line along the outermost edge of the curved surface portion is a portion included in at least the range of the other side L in the width direction of the separator 11. Note that a rectangular range including these sides, an elliptical range in which such a rectangular shape is inscribed, or the like may be set in the deactivation region 20.

  In this example, as a structural example for losing the activity of the positive electrode mixture (positive electrode active material) applied to the positive electrode sheet 12, for example, the positive electrode mixture also in the deactivated region 20 as in the uncoated portion 12a. A configuration in which (the positive electrode active material) is not applied is adopted. As a result, in the deactivated region 20, there is no positive electrode active material necessary for the exchange of lithium ions, so that an oxidation-reduction reaction occurs during charging / discharging of the nonaqueous electrolyte secondary battery 1 regardless of the presence or absence of winding looseness. Absent.

  Further, as another configuration example for losing the activity of the positive electrode mixture (positive electrode active material) applied to the positive electrode sheet 12, for example, in the deactivated region 20, the applied positive electrode mixture (positive electrode active material). A structure may be employed in which the surface is covered with a coating, coating film or tape that prevents the movement of lithium ions. As a result, in the deactivated region 20, even if a positive electrode active material necessary for the exchange of lithium ions is present, the exchange of lithium ions is hindered by a coating covering the surface, etc. No oxidation-reduction reaction occurs during charging / discharging of the water electrolyte secondary battery 1.

  Among these configurations, (1) a configuration in which the positive electrode mixture (positive electrode active material) is not applied in the deactivated region 20, and (2) the surface of the coated positive electrode mixture (positive electrode active material) is coated with a film or the like. When the effect verification test regarding the precipitation of lithium was conducted for the covering structure, the following results were obtained. In the test, a constant current charge of 125 A (ampere) was applied to a non-aqueous electrolyte secondary battery at an SOC of 20% at an ambient temperature of 0 ° C. under a SOC (State Of Charge: 100% charge) for 30 seconds. Added pulse charge was performed. As a result, in any of the configurations (1) and (2), lithium deposition was not confirmed in the arc-shaped portion 10 b of the electrode body 10, particularly in the deactivated region 20. On the other hand, in the conventional configuration in which the deactivation region 20 is not provided, lithium deposition was confirmed in the arc-shaped portion 10 b of the electrode body 10.

  As described above, in the nonaqueous electrolyte secondary battery 1, the outermost peripheral lamination in the arc-shaped portion 10b to which the winding ends 11a, 12b, and 13b are connected among the arc-shaped portions 10a and 10b at both ends of the electrode body 10. Deactivation in which the body loses the activity of the positive electrode mixture (positive electrode active material) applied to the positive electrode sheet 12 on the other side in the width direction with respect to one side in the width direction of the negative electrode sheet 13 to which the negative electrode current collector 5 is fixed. A region 20 is provided. In such a deactivated region 20, no oxidation-reduction reaction occurs during charging / discharging. Therefore, even in the arc-shaped portion 10 b, even if winding is loosened on the other side in the width direction of the negative electrode sheet 13 to which the negative electrode current collector 5 is not fixed. The part where the loosening of the winding occurs is the deactivation region 20, and therefore there is no redox reaction. Therefore, even if loose winding occurs on the other side in the width direction of the negative electrode sheet 13, there is no influence on the oxidation-reduction reaction during charge / discharge. Therefore, the variation of the oxidation-reduction reaction at the time of charging / discharging due to such loosening of the arc-shaped portion 10b is suppressed.

  Points to be noted regarding the example technology will be described. The arc-shaped portion 10b corresponds to an example of “an arc-shaped portion connected to the winding end”.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. Further, the technical elements described in the present specification or drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Moreover, the technique illustrated in this specification or the drawings achieves a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

1: Nonaqueous electrolyte secondary battery 2: Battery case 4: Positive electrode current collector 4a, 5a: Welded part 5: Negative electrode current collector 7: Positive electrode external terminal 8: Negative electrode external terminal 9: Sleeve 10: Electrode bodies 10a, 10b : Arc-shaped part 10c: Flat part 11: Separator 11a: Winding end 12: Positive electrode sheet 13: Negative electrode sheet 12a, 13a: Uncoated part 12b, 13b: Winding end 20: Deactivation region

Claims (1)

A non-aqueous electrolyte secondary battery having an electrode body obtained by winding a laminate of a positive electrode sheet and a negative electrode sheet with a separator interposed therebetween in a flat shape,
The electrode body has arc-shaped portions at both ends of the flat shape,
Of the arc-shaped portions at both ends of the electrode body, the outermost laminate in the arc-shaped portion to which the winding ends are connected is on the other side in the width direction with respect to one side in the width direction of the negative electrode sheet to which the negative electrode current collector is fixed. A non-aqueous electrolyte secondary battery comprising a deactivation region that loses the activity of a positive electrode active material applied to a positive electrode sheet.

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