JP5955721B2 - Lithium ion secondary battery and manufacturing method thereof - Google Patents

Description

  The present invention relates to a lithium ion secondary battery and a method for manufacturing the same.

  A lithium ion secondary battery is a secondary battery that can be charged and discharged by moving lithium ions in a non-aqueous electrolyte between a positive electrode and a negative electrode that occlude and release lithium ions.

  Patent Document 1 discloses a technique related to a lithium ion secondary battery that can effectively prevent deterioration of the battery due to charge and discharge. In the charge / discharge control method for a lithium ion secondary battery disclosed in Patent Document 1, a reference electrode that is electrically independent from the electrode body is installed inside the battery container, the potential difference between the reference electrode and the positive external terminal, and the reference The potential difference between the electrode and the negative electrode external terminal is constantly monitored, and charging or discharging is stopped when at least one of the potential differences exceeds a predetermined threshold value.

JP 2001-015177 A

  In a lithium ion secondary battery, the potential of the positive electrode or the negative electrode can be detected by providing a reference electrode. By detecting the potential of the positive electrode or the negative electrode in this way, for example, charge / discharge control of a lithium ion secondary battery can be appropriately performed.

  However, for example, when metallic lithium is used as the reference electrode material, the non-aqueous electrolyte is decomposed due to the low oxidation-reduction potential of metallic lithium, and a decomposition product of the non-aqueous electrolytic solution is formed on the surface of the metallic lithium. Is done. For this reason, when the reference electrode is used for a long period of time, there is a problem that the potential of the reference electrode varies, and the potential of the positive electrode and the negative electrode measured based on the reference electrode also varies. Moreover, since the reference electrode is used, for example, when controlling charge / discharge of a lithium ion secondary battery, sufficient durability is required.

  In view of the above problems, an object of the present invention is to provide a lithium ion secondary battery having a reference electrode having stability and durability, and a method for producing the lithium ion secondary battery.

  A lithium ion secondary battery according to the present invention includes a positive electrode and a negative electrode, a separator interposed between the positive electrode and the negative electrode, a non-aqueous electrolyte containing lithium ions and filled between the positive electrode and the negative electrode, A reference electrode disposed so as to be in contact with the non-aqueous electrolyte, and the reference electrode includes a base material made of aluminum and a coating layer containing a lithium aluminum alloy.

In the lithium ion secondary battery, the base material may be a core material made of aluminum, and the covering layer may be disposed around the core material.
The covering layer may extend radially from the core material to the periphery of the core material, and may have a plurality of protrusions having a higher aluminum ratio than the lithium aluminum alloy. It may be arranged between the protrusions.
The cross-sectional area of the core material may be 10% or more and 90% or less of the cross-sectional area of the reference electrode. The diameter of the cross section of the reference electrode may be 0.2 mm or less, or 0.1 mm or less.

In the lithium ion secondary battery, the base material may be a planar substrate made of aluminum, and the coating layer may be disposed on at least a part of at least one surface of the planar substrate, The thickness of the reference electrode may be smaller than the positive electrode mixture layer of the positive electrode and the negative electrode mixture layer of the negative electrode.
The reference electrode may further have a thickness of 1/20 or less of the thinnest mixture layer of the positive electrode mixture layer or the negative electrode mixture layer. The covering layer may be disposed on at least a part of one surface of the planar substrate, and an insulating layer may be formed on the other surface of the planar substrate, and the planar substrate may be the insulating layer. An aluminum film formed thereon may also be used.

  In the method for producing a lithium ion secondary battery according to the present invention, a separator is disposed between a positive electrode and a negative electrode, a nonaqueous electrolytic solution containing lithium ions is filled between the positive electrode and the negative electrode, and the nonaqueous electrolytic solution An aluminum material is placed in contact with the aluminum material, and a current is passed between the aluminum material and the positive electrode or between the aluminum material and the negative electrode to form a coating layer containing a lithium aluminum alloy on the surface of the aluminum material Thus, each step of forming the reference electrode is included.

  In the method for manufacturing a lithium ion secondary battery, the aluminum material may be an aluminum wire. When forming the reference electrode, the aluminum wire may be rotated, and the cross-sectional area of the core material of the aluminum wire on which the lithium aluminum alloy is not formed is 10% or more of the cross-sectional area of the reference electrode. % Or less.

The aluminum material may be planar, and the coating layer may be formed on at least a part of at least one surface of the aluminum material, and the thickness of the reference electrode may be the positive electrode. The reference electrode may be formed so as to be smaller than the negative electrode mixture layer and the negative electrode mixture layer of the negative electrode.
You may form the said reference electrode so that the thickness of the said reference electrode may become 1/20 or less of the thinnest mixture layer among the said positive mix layer or the said negative mix layer further.

  According to the present invention, it is possible to provide a lithium ion secondary battery having a reference electrode having stability and durability, and a method for producing a lithium ion secondary battery.

It is sectional drawing in the longitudinal direction of the reference electrode with which the lithium ion secondary battery concerning 1st Embodiment is provided. It is sectional drawing in II-II of the reference electrode shown in FIG. It is the cross-sectional photograph which image | photographed the reference electrode with which the lithium ion secondary battery concerning 1st Embodiment is equipped with the scanning electron microscope. (A) is a cross-sectional photograph when the diameter of the core material is relatively large, and (b) is a cross-sectional photograph when the diameter of the core material is relatively small. 1 is a perspective view showing a lithium ion secondary battery according to a first embodiment. It is sectional drawing in VV of the lithium ion secondary battery shown in FIG. It is a figure for demonstrating the manufacturing method of the lithium ion secondary battery concerning 1st Embodiment. It is a figure for demonstrating the usage example of the reference electrode with which the lithium ion secondary battery concerning 1st Embodiment is provided. It is a graph which shows the relationship between the time which is using a reference electrode, and the electric potential of a reference electrode. It is the cross-sectional photograph which image | photographed the reference electrode of the comparative example with the scanning electron microscope. (A) is a cross-sectional photograph of a reference electrode mainly composed of aluminum, and (b) is a cross-sectional photograph of a reference electrode mainly composed of a lithium aluminum alloy. It is a graph which shows the relationship between the ratio of the cross-sectional area of the core material of a reference electrode, and time for a reference electrode to operate | move stably. It is a top view of the reference electrode with which the lithium ion secondary battery concerning Embodiment 2 is provided. It is sectional drawing in XII-XII of the reference electrode shown in FIG. It is a perspective view which shows the lithium ion secondary battery concerning 2nd Embodiment. It is a top view of the reference electrode with which the lithium ion secondary battery concerning an Example is provided. It is sectional drawing in XV-XV of the reference electrode shown in FIG. It is a perspective view which shows the lithium ion secondary battery concerning an Example. It is sectional drawing in XVII-XVII of the lithium ion secondary battery shown in FIG. It is a cross-sectional photograph of a wound electrode body. (A) is an Example and (b) is a comparative example. It is a graph which shows the time change of the electrical resistance of the battery incorporating a reference electrode.

Embodiments of the present invention will be described below.
[First embodiment]
The lithium ion secondary battery according to the first embodiment includes a positive electrode and a negative electrode, a separator interposed between the positive electrode and the negative electrode, a non-aqueous electrolyte containing lithium ions and filled between the positive electrode and the negative electrode, And a reference electrode arranged to be in contact with the non-aqueous electrolyte.

<Positive electrode>
The positive electrode has a positive electrode active material. The positive electrode active material is a material capable of inserting and extracting lithium. For example, lithium cobaltate (LiCoO ₂ ), lithium manganate (LiMn ₂ O ₄ ), lithium nickelate (LiNiO ₂ ), and the like can be used. _{Moreover, LiCoO 2, LiMn 2 O 4} , LiNiO 2 and may be a material obtained by firing mixed at an arbitrary ratio. An example of the composition is, for example, LiNi _1/3 Co _1/3 Mn _1/3 O _{2 in} which these materials are mixed at an equal ratio.

  The positive electrode may contain a conductive material. As the conductive material, for example, carbon black such as acetylene black (AB) and ketjen black, and graphite (graphite) can be used.

  The positive electrode of the lithium ion secondary battery according to the present embodiment includes, for example, a positive electrode active material, a conductive material, a solvent, and a binder (binder), and the positive electrode mixture after kneading is mixed with the positive electrode current collector. It can be produced by applying to the body and drying. Here, as the solvent, for example, an NMP (N-methyl-2-pyrrolidone) solution can be used. As the binder, for example, polyvinylidene fluoride (PVdF), styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), or the like can be used. As the positive electrode current collector, aluminum or an alloy containing aluminum as a main component can be used.

<Negative electrode>
The negative electrode active material is a material capable of inserting and extracting lithium, and for example, a powdery carbon material made of graphite or the like can be used. Then, similarly to the positive electrode, the negative electrode can be produced by kneading the negative electrode active material, the solvent, and the binder, applying the kneaded negative electrode mixture to the negative electrode current collector, and drying. Here, as the negative electrode current collector, for example, copper, nickel, or an alloy thereof can be used.

<Non-aqueous electrolyte>
The nonaqueous electrolytic solution is a composition in which a supporting salt is contained in a nonaqueous solvent. Here, as the non-aqueous solvent, one or two selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and the like. More than one type of material can be used. The supporting salts include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiI 1 type, or 2 or more types of lithium compounds (lithium salt) selected from these etc. can be used.

<Separator>
An insulating porous film can be used for the separator. For example, as the separator, a porous polymer film such as a polyethylene film, a polyolefin film, and a polyvinyl chloride film, or a lithium ion or ion conductive polymer electrolyte film can be used alone or in combination.

<Reference electrode>
FIG. 1 is a cross-sectional view in the longitudinal direction of a reference electrode provided in the lithium ion secondary battery according to the present embodiment. 2 is a cross-sectional view taken along the line II-II of the reference electrode shown in FIG.

  As shown in FIG. 1, the reference electrode 10 included in the lithium ion secondary battery according to the present embodiment includes a core material 11 made of aluminum and a coating layer 12 including a lithium aluminum alloy disposed around the core material 11. And have. That is, the reference electrode 10 is in contact with the nonaqueous electrolytic solution, and the periphery of the tip portion functioning as the reference electrode is covered with the coating layer 12 containing a lithium aluminum alloy. Since the core material 11 is surrounded by the coating layer 12, the core material 11 does not come into contact with the non-aqueous electrolyte. Further, in the core material 11, the core material 11 is a portion other than the tip portion where the coating layer 12 is formed, and around the portion inserted into the lithium ion secondary battery. An insulating layer 13 is formed so as not to contact. For the insulating layer 13, for example, polyimide can be used.

  As shown in the cross-sectional view of FIG. 2, the covering layer 12 includes a lithium aluminum alloy 14 and a plurality of protrusions extending radially from the core material 11 to the periphery of the core material 11 and having a higher aluminum ratio than the lithium aluminum alloy 14. Part 15. Here, the lithium aluminum alloy 14 is disposed between the plurality of protrusions 15. The lithium aluminum alloy 14 has the property of being porous and having a large surface area.

  3A and 3B are cross-sectional photographs obtained by photographing the reference electrode 10 included in the lithium ion secondary battery according to the present embodiment with a scanning electron microscope (SEM). The core material 11 in FIG. 3B is thinner than the core material 11 in FIG. 3A, and the coating layer 12 in FIG. 3B is thicker than the coating layer 12 in FIG. The thickness of the coating layer 12 can be arbitrarily changed by adjusting the conditions for forming the reference electrode.

  For example, when metallic lithium is used as the material for the reference electrode, the non-aqueous electrolyte is decomposed due to the low oxidation-reduction potential (hereinafter also simply referred to as potential) of metallic lithium, and non-aqueous electrolysis occurs on the surface of metallic lithium. A liquid decomposition product is formed. For this reason, when a reference electrode made of metallic lithium is used for a long period of time, the potential of the reference electrode varies, and the potentials of the positive electrode and the negative electrode measured based on the reference electrode also vary.

  On the other hand, since the lithium aluminum alloy has a higher potential than metallic lithium, it is possible to suppress the decomposition of the nonaqueous electrolytic solution. Therefore, by using a material containing a lithium aluminum alloy for the coating layer 12 of the reference electrode 10 as in the lithium ion secondary battery according to the present embodiment, the decomposition product of the nonaqueous electrolyte solution on the surface of the reference electrode 10 Can be prevented from being formed. Therefore, deterioration of the reference electrode can be suppressed, and the potential indicated by the reference electrode can be stabilized. Further, since the lithium aluminum alloy has a large surface area, for example, even if there is some electrical fluctuation on the detection circuit side, a stable potential can be exhibited over a long period of time.

  The reference electrode 10 of the lithium ion secondary battery according to the present embodiment has a core material 11 made of aluminum at the center of the reference electrode 10. Therefore, the mechanical strength of the reference electrode 10 can be increased. For example, when the charging / discharging of the lithium ion secondary battery is repeated, the volume of the positive and negative electrodes changes due to the insertion / extraction of lithium ions, so that the reference electrode 10 is stressed. Even in such a case, it is possible to suppress the disconnection of the reference electrode 10 by providing the core material 11 made of aluminum at the center of the reference electrode 10.

  As shown in FIG. 2, the covering layer 12 is formed with protruding portions 15 having a higher aluminum ratio than the lithium aluminum alloy 14 so as to extend radially from the core material 11. The lithium aluminum alloy 14 is disposed between the plurality of protrusions 15. Here, since the protrusion 15 has a high aluminum ratio, the electrical resistance is low. Therefore, a conductive path that connects the surface of the reference electrode 10 and the core material 11 can be provided, and the lithium aluminum alloy 14 disposed between the surface of the reference electrode 10 and the core material 11 can be effectively used. it can. Thereby, the electric potential which a reference electrode shows can be stabilized for a long term.

  Moreover, since the lithium aluminum alloy 14 is porous, its strength is relatively weak. On the other hand, the protrusion 15 has a relatively high strength due to a high aluminum ratio. Therefore, as shown in FIG. 2, the strength of the covering layer 12 can be improved by disposing the lithium aluminum alloy 14 having a relatively low strength between the protrusions 15 having a relatively high strength.

  The reference electrode is provided between the positive electrode and the negative electrode. At this time, if the cross-sectional diameter of the reference electrode 10 is large, the battery performance of the lithium ion secondary battery may be deteriorated. Therefore, although it is preferable that the diameter of the reference electrode is smaller, there is a problem that the strength of the reference electrode is reduced when the diameter of the reference electrode is reduced.

  On the other hand, in the reference electrode 10 included in the lithium ion secondary battery according to the present embodiment, since the core material 11 made of aluminum is provided, the mechanical strength of the reference electrode 10 can be increased. Therefore, even if the diameter of the reference electrode 10 is reduced, the strength of the reference electrode 10 can be ensured. The diameter of the cross section of the reference electrode 10 can be, for example, 0.2 mm or less, more preferably 0.1 mm or less.

  By providing the reference electrode 10 in the lithium ion secondary battery, the charge / discharge state of the lithium ion secondary battery and the deterioration state of the electrode can be separately monitored by the positive electrode and the negative electrode. Further, by controlling the charging of the battery according to the positive electrode potential or the negative electrode potential measured using the reference electrode, it is possible to control the deterioration of the electrode during rapid charging.

  By using the reference electrode 10 described above, the stability and durability of the reference electrode can be ensured.

<Lithium ion secondary battery>
Hereinafter, a lithium ion secondary battery provided with a wound electrode body will be described as an example. FIG. 4 is a perspective view showing a lithium ion secondary battery according to the present embodiment. 5 is a cross-sectional view taken along VV of the lithium ion secondary battery shown in FIG.

  As shown in FIGS. 4 and 5, the lithium ion secondary battery 1 includes a wound electrode body 20 having a positive electrode sheet (positive electrode) 21, a negative electrode sheet (negative electrode) 22 and a separator 23, and the wound electrode body 20. A battery case 40 to be accommodated, a non-aqueous electrolyte containing lithium ions and impregnated in the separator 23 of the wound electrode body 20, and a reference electrode 10 in contact with the non-aqueous electrolyte are provided. Further, a conductive wire 17 connected to the reference electrode 10 and a reference electrode terminal 18 connected to the conductive wire 17 are provided. The conducting wire 17 is covered with an insulating layer.

  The battery case 40 includes a battery case main body 41 and a sealing lid 42. The battery case body 41 has a rectangular box shape, and an insulating film (not shown) made of resin and bent into a box shape is provided between the battery case body 41 and the wound electrode body 20. The sealing lid 42 has a rectangular plate shape, closes the opening of the battery case body 41, and is welded to the battery case body 41. As a material constituting the battery case 40, a metal material such as aluminum or steel is preferable. For example, the battery case 40 may be formed using a resin material such as polyphenylene sulfide resin (PPS) or polyimide resin.

  A positive electrode member 33 that is electrically connected to the positive electrode sheet 21 of the wound electrode body 20 is provided on the sealing lid 42 so as to protrude from the surface of the sealing lid 42. A portion of the positive electrode member 33 that protrudes from the surface of the sealing lid 42 constitutes the positive electrode terminal portion 31. An insulating member 32 is provided between the positive terminal portion 31 and the sealing lid 42 to electrically insulate them. Similarly, the sealing lid 42 is provided with a negative electrode member 36 that is electrically connected to the negative electrode sheet 22 of the wound electrode body 20 so as to protrude from the surface of the sealing lid 42. The portion of the negative electrode member 36 that protrudes from the surface of the sealing lid 42 constitutes the negative electrode terminal 34. An insulating member 35 is provided between the negative electrode terminal portion 34 and the sealing lid 42 to electrically insulate them. The sealing lid 42 is provided with a rectangular plate-shaped safety valve 47.

  In the wound electrode body 20, a long positive electrode sheet 21 and a long negative electrode sheet 22 are wound flatly via a long separator 23. The positive electrode sheet 21 has a structure in which a positive electrode mixture layer containing a positive electrode active material is held on both surfaces of a foil-shaped positive electrode current collector. Similarly to the positive electrode sheet, the negative electrode sheet 22 has a structure in which a negative electrode mixture layer containing a negative electrode active material is held on both surfaces of a foil-like negative electrode current collector. When producing the wound electrode body 20, the positive electrode sheet 21 and the negative electrode sheet 22 are laminated via the separator 23. And the laminated body laminated | stacked in this way is wound, and the obtained wound body is crushed from the side surface direction, and the flat wound electrode body 20 is produced.

  As shown in FIG. 5, the reference electrode 10 is provided between the positive electrode sheet 21 and the negative electrode sheet 22. At this time, in order to prevent the reference electrode 10 and the positive electrode sheet 21 from being in direct contact with each other and to prevent the reference electrode 10 and the negative electrode sheet 22 from being in direct contact with each other, for example, between the reference electrode 10 and the positive electrode sheet 21 and A part of the separator 23 may be disposed between the reference electrode 10 and the negative electrode sheet 22.

<Method for producing reference electrode>
Next, the manufacturing method (especially the manufacturing method of a reference electrode) of the lithium ion secondary battery concerning this Embodiment is demonstrated using FIG. When manufacturing the lithium ion secondary battery according to the present embodiment, first, the separators 23_1 and 23_2 are disposed between the positive electrode (positive electrode sheet) 21 and the negative electrode (negative electrode sheet) 22. Here, the positive electrode 21 includes a positive electrode current collector 51 and a positive electrode active material 52. The negative electrode 22 includes a negative electrode current collector 54 and a negative electrode active material 55.

  Next, a nonaqueous electrolytic solution 27 containing lithium ions is filled between the positive electrode 21 and the negative electrode 22. At this time, the non-aqueous electrolyte solution 27 is impregnated in the separators 23_1 and 23_2. Next, the aluminum wire 11 (which becomes the core material 11 after the reference electrode is formed) is disposed so as to be in contact with the non-aqueous electrolyte solution 27. At this time, the insulating layer 13 is provided in a portion of the aluminum wire 11 other than the tip portion. By providing the insulating layer 13, it is possible to prevent a portion other than the tip portion where the reference electrode is formed from coming into contact with the non-aqueous electrolyte.

Then, a current of a predetermined amount of electricity is passed between the aluminum wire 11 and the positive electrode 21 to form a coating layer 12 containing a lithium aluminum alloy on the surface of the aluminum wire 11, thereby forming the reference electrode 10. That is, by supplying a current from the aluminum wire 11 to the positive electrode 21, electrons are supplied from the positive electrode 21 to the aluminum wire 11. Since the non-aqueous electrolyte 27 contains lithium ions (Li ⁺ ), lithium is deposited on the surface of the aluminum wire 11 by the lithium ions taking in the electrons supplied to the aluminum wire 11. The deposited lithium forms a lithium aluminum alloy with a part of the aluminum wire 11. The thickness of the coating layer 12 containing a lithium aluminum alloy can be changed by adjusting the magnitude and time of the current flowing between the aluminum wire 11 and the positive electrode 21.

  As shown in FIG. 2, the coating layer 12 includes a lithium aluminum alloy 14 and a protrusion 15 having a higher aluminum ratio than the lithium aluminum alloy 14. When the reference electrode 10 is formed by the method described above, the lithium aluminum alloy 14 is formed from the surface of the aluminum wire 11 toward the inside. Therefore, the portion of the coating layer 12 where the lithium aluminum alloy 14 is formed corresponds to the portion where the reaction for forming the lithium aluminum alloy has progressed well, and the portion where the protruding portion 15 is formed is This corresponds to the portion where the reaction for forming the lithium aluminum alloy did not proceed well.

  By forming the reference electrode 10 by the method described above, the reference electrode can be stably manufactured. That is, although lithium aluminum alloy is porous, its strength is weak. However, as described above, the reference electrode 10 is formed by forming the reference electrode 10 after the aluminum wire 11 is provided inside the lithium ion secondary battery. After that, the external force applied to the reference electrode 10 can be reduced as compared with the case where the reference electrode 10 is installed inside the lithium ion secondary battery.

  Further, when the reference electrode 10 is formed, the coating layer 12 can be more uniformly formed on the surface of the aluminum wire 11 by rotating the aluminum wire 11. For example, after passing a current between the aluminum wire 11 and the positive electrode 21 for a predetermined time, the aluminum wire 11 is rotated by a predetermined angle, and further, a current is supplied between the aluminum wire 11 and the positive electrode 21 for a predetermined time. You may make it flow. Further, a current may be passed between the aluminum wire 11 and the positive electrode 21 while the aluminum wire 11 is continuously rotated.

  In the above example, the case where the reference electrode 10 is formed by flowing a current between the positive electrode 21 and the aluminum wire 11 has been described. However, the reference electrode 10 is formed by flowing a current between the negative electrode 22 and the aluminum wire 11. You may comprise so that it may form. In this case, the coating layer 12 containing a lithium aluminum alloy can be formed on the surface of the aluminum wire 11 by passing a current from the aluminum wire 11 to the negative electrode 22.

<Usage example of reference electrode>
FIG. 7 is a diagram for explaining an example of use of the reference electrode 10 included in the lithium ion secondary battery according to the present embodiment. In the usage example shown in FIG. 7, a case where the potential of the negative electrode 22 with respect to the reference electrode 10 is measured is shown. That is, the potential of the negative electrode 22 with respect to the reference electrode 10 can be determined by determining the potential difference between the potential of the negative electrode 22 and the potential of the reference electrode 10.

  Although FIG. 7 shows the case where the potential of the negative electrode 22 with respect to the reference electrode 10 is measured, the potential of the positive electrode 21 can also be measured by the same method. That is, the potential of the positive electrode 21 with respect to the reference electrode 10 can be obtained by obtaining the potential difference between the potential of the positive electrode 21 and the potential of the reference electrode 10.

<Description of the effect of the present invention>
Next, a comparative example between the case where the reference electrode is configured using the conventional technique and the case where the reference electrode 10 is configured using the method described above will be described. FIG. 8 is a graph showing the relationship between the time during which the reference electrode is used and the potential of the reference electrode. The reference electrode of Comparative Example 1 shown in FIG. 8 is a reference electrode in which the amount of lithium aluminum alloy is insufficient, that is, a reference electrode mainly composed of aluminum. FIG. 9A shows a cross-sectional photograph of the reference electrode of Comparative Example 1 taken with a scanning electron microscope (SEM). As shown in FIG. 9A, most of the reference electrodes of Comparative Example 1 are made of aluminum 111.

  Moreover, the reference electrode of the comparative example 2 shown in FIG. 8 is a reference electrode mainly comprised with the lithium aluminum alloy, and the center axis | shaft (core material) is also comprised with the lithium aluminum alloy. FIG. 9B shows a cross-sectional photograph of the reference electrode of Comparative Example 2 taken with a scanning electron microscope (SEM). As shown in FIG. 9B, since most of the reference electrode of Comparative Example 2 is composed of the lithium aluminum alloy 112, the entire reference electrode including the central axis has a porous structure. Note that a portion indicated by reference numeral 116 is a portion that is missing during analysis.

  As shown in FIG. 8, in the reference electrode of Comparative Example 1, the potential indicated by the reference electrode varies with time. The reason for this is considered to be that lithium is detached from the reference electrode because the amount of the lithium aluminum alloy is insufficient in the reference electrode of Comparative Example 1. Further, it is considered that a decomposition product of the nonaqueous electrolytic solution is formed on the surface of the reference electrode. Since the reference electrode of Comparative Example 2 contains a lithium aluminum alloy, the potential indicated by the reference electrode is stable. However, the reference electrode of Comparative Example 2 is weak in strength because the central axis (core material) is also made of a lithium aluminum alloy, and is broken halfway as shown in FIG.

  On the other hand, the reference electrode 10 provided in the lithium ion secondary battery according to the present embodiment shows a stable potential over a long period of time. That is, the reference electrode 10 includes a lithium aluminum alloy in the coating layer 12. Since the lithium aluminum alloy has a high oxidation-reduction potential, the decomposition reaction of the nonaqueous electrolytic solution can be suppressed, and the potential indicated by the reference electrode can be stabilized. Moreover, since the reference electrode 10 is provided with the core 11 made of aluminum, the mechanical strength of the reference electrode 10 can be increased.

  FIG. 10 is a graph showing the relationship between the ratio of the cross-sectional area of the core material 11 of the reference electrode 10 (that is, the area of the substantially circular portion of the core material 11) and the time during which the reference electrode 10 operates stably. Here, the time for which the reference electrode 10 operates stably is the time until the potential indicated by the reference electrode 10 exceeds a predetermined allowable range after the measurement of the potential of the reference electrode 10 is started, in other words, the potential indicated by the reference electrode 10. Corresponds to a time for operating within a predetermined tolerance.

  As shown in FIG. 10, when the ratio of the cross-sectional area of the core material 11 is about 4%, the time for which the reference electrode 10 operates stably is short. The reason for this is considered to be that the strength of the reference electrode 10 is weakened when the ratio of the cross-sectional area of the core material 11 is too small. Moreover, when the ratio of the core material 11 is 90% or more, the time for which the reference electrode 10 operates stably is short. This is because when the ratio of the core material 11 is 90% or more, lithium ions are gradually desorbed from the reference electrode 10 and become only aluminum, so that the potential becomes unstable. In addition, aluminum alone does not become a reference electrode because the potential is unstable.

  On the other hand, when the cross-sectional area of the core material 11 is 10% or more and 90% or less of the cross-sectional area of the reference electrode 10, the reference electrode operates stably over a long period of time. That is, by setting the cross-sectional area of the core material 11 to 10% or more and 90% or less of the cross-sectional area of the reference electrode 10, while maintaining the strength of the reference electrode 10 by the core material 11, the surface of the reference electrode is not made by lithium aluminum alloy It is possible to suppress the formation of decomposition products of the water electrolyte.

[Second Embodiment]
In the description of the second embodiment, overlapping description of elements equivalent to those of the first embodiment is omitted.
<Positive electrode>
The positive electrode mixture layer having a predetermined thickness is formed by applying the positive electrode mixture to the positive electrode current collector and drying it. The thickness of the positive electrode mixture layer can be, for example, 50 to 65 μm in total on both sides.

<Negative electrode>
The negative electrode mixture layer having a predetermined thickness is formed by applying the negative electrode mixture to the negative electrode current collector and drying it. The thickness of the negative electrode mixture layer can be, for example, 60 to 70 μm in total on both sides.

<Reference electrode>
A reference electrode having a predetermined thickness described later is disposed between the positive electrode and the negative electrode. 11 and 12 show a reference electrode 60 included in the lithium ion secondary battery according to the second embodiment. The reference electrode 60 is a sheet-like or plate-like electrode. The reference electrode 60 has an electrode surface on at least one surface. In FIG. 12, an electrode surface is provided above the figure. Since the electrode surface is in contact with the non-aqueous electrolyte, the potential can be measured. A planar substrate 61 is shown as a base material of the reference electrode 60.

  One function of the planar substrate 61 is to be a base material for laminating the coating layer 62 as an electrode surface having a lithium alloy. As the lithium alloy, one having a redox potential higher than that of metallic lithium can be used. The covering layer 62 is preferably made by forming a part of a metal film, a metal foil, a metal sheet, or a metal plate as a material of the planar substrate 61 into a lithium alloy. Further, the planar substrate 61 may be combined with another support material (not shown) or another member to constitute an electrode, and the other member is formed of a metal or other material different from the planar substrate 61. May be.

The planar substrate 61 preferably contains a metal capable of generating the lithium alloy. As such a metal, aluminum, indium, bismuth, antimony, tin and silver can be used. As the lithium alloy, lithium alloys of these metals can be used.
Since the planar substrate 61 according to the present embodiment is made of aluminum, the electrical resistance is sufficiently low, and the reference electrode 60 exhibits stable performance over the long term.

  When aluminum is used as the planar substrate 61, Si, Fe, Cu, Mn, Mg, Zn, Cr, Ti, Al, and other elements may be included as impurities. From the viewpoint of corrosion resistance, the purity of aluminum is preferably 99.0% or more, and particularly preferably 99.9% or more.

  The planar substrate 61 may be a plate material or a thin plate material that can maintain the shape independently, or may be a film or a thin film that cannot maintain the shape independently. Moreover, it may be flat and may have a curved surface. From the viewpoint of increasing the mechanical strength of the reference electrode 60, the thickness of the planar substrate 61 is preferably 2 μm or more.

  The reference electrode 60 includes a coating layer 62 including a porous lithium aluminum alloy that covers the planar substrate 61 in a region of a predetermined length at the tip. The covering layer 62 constitutes an electrode surface and is formed on at least a part of the upper surface of the planar substrate 61 in FIG. By including the lithium aluminum alloy in the coating layer 62, it is possible to suppress the decomposition product of the nonaqueous electrolytic solution from being formed on the electrode surface of the reference electrode 60. For this reason, the potential indicated by the reference electrode 60 is stabilized. When the lithium aluminum alloy is porous, the strength is weak, and the electrode constituted only by it is insufficient in mechanical strength. Therefore, it is preferable that the upper substrate 61 carries the coating layer 62.

  When charging / discharging of the lithium ion secondary battery is repeated, the volume of the positive and negative electrodes changes due to the insertion / extraction of lithium ions. Further, the positive and negative electrodes expand and contract due to temperature changes, and the volume changes. For this reason, mechanical stress is applied to the reference electrode 60. Even in such a case, it is possible to suppress disconnection of the reference electrode 60 by providing the planar substrate 61 made of aluminum at the center of the reference electrode 60.

In the reference electrode 60, the insulating layer 63 covers at least a region disposed between the positive electrode and the negative electrode other than a region covered with the coating layer 62. That is, the portion of the planar substrate 61 that is not covered with the coating layer 62 and that can come into contact with the nonaqueous electrolytic solution is directly or indirectly covered with the insulating layer 63.
As a material of the insulating layer 63, for example, it is preferable to use a thermosetting resin such as polyimide and paraxylylene resin, and it is particularly preferable to use polyimide.

The insulating layer 63 can be designed in a suitable shape according to the embodiment from the viewpoint of avoiding contact with the non-aqueous electrolyte and short circuit with the positive and negative electrodes included in the lithium ion secondary battery. More specifically, the thickness of the insulating layer 63 is preferably 1 μm or more from the viewpoint of ensuring insulation. Further, from the viewpoint of reducing the thickness of the reference electrode 60, the thickness of the insulating layer 63 formed on at least one surface is preferably 20 μm or less.
Further, the support material (not shown) may be covered with the insulating layer 63, and a part of the support material (not shown) may not be covered with the insulating layer. In FIG. 12, the insulating layer 63 is formed so as to cover the lower surface of the planar substrate 61. Also, in FIG. 12, the insulating layer 63 is formed so as to cover a portion of the upper surface of the planar substrate 61 where the electrode surface is not formed.

By appropriately disposing the insulating layer 63 in accordance with the above, the mechanical strength of the reference electrode 60 is further increased and it is not easily disconnected. Specifically, damage to the substrate 61 on the surface due to mechanical stress based on ion insertion / desorption or expansion / contraction of the positive electrode or the negative electrode accompanying temperature change is suppressed.
The above effect is particularly prominent when the planar substrate 61 is formed of a thin film. That is, when the planar substrate 61 is formed of a thin film, the strength of the planar substrate 61 is lowered. However, the planar substrate 61 can be prevented from being damaged by forming the planar substrate 61 on the insulating layer 63 having high strength.

  Moreover, it can suppress that the planar base material 61 contacts a nonaqueous electrolyte by covering the planar base material 61 with the coating layer 62 and the insulating layer 63. Further, since the surface area of the covering layer 62 can be increased, the secondary battery exhibits a stable potential for a long time even if there is some electrical fluctuation on the detection circuit side.

  Since the reference electrode 60 is provided between the positive electrode and the negative electrode, the thickness of the reference electrode 60 is preferably smaller than the positive electrode mixture layer and the negative electrode mixture layer. Moreover, it is preferable that this thickness is 1/20 or less of the thinnest mixture layer among a positive mix layer or a negative mix layer. By adopting such a configuration, the adhesion between the mixture layer and the separator is maintained, so that a decrease in battery performance is suppressed. The thickness of the reference electrode may be 1/20 or less of the thinnest mixture layer of the positive electrode mixture layer or the negative electrode mixture layer.

  The reference electrode 60 preferably has a predetermined width in the direction perpendicular to the direction from the electrode portion toward the lead portion from the electrode portion to the lead portion. The predetermined width is preferably 0.1 mm or less, and particularly preferably 0.05 mm or less. When the width of the reference electrode 60 is in the above range, a decrease in battery performance is suppressed. In addition, the reliability of electrode potential measurement is improved.

<Lithium ion secondary battery>
By providing the reference electrode 60 in the lithium ion secondary battery, the charge / discharge state of the lithium ion secondary battery and the deterioration state of the electrode can be separated and monitored by the positive electrode and the negative electrode. Further, by controlling the charging of the battery according to the positive electrode potential or the negative electrode potential measured using the reference electrode, it is possible to control the deterioration of the electrode during rapid charging. For this reason, the stability and durability of the battery can be ensured.

  As shown in FIG. 13, the lithium ion secondary battery 2 is different from the first embodiment in that a reference electrode 60 is provided instead of the reference electrode 10 (see FIG. 4). The reference electrode 60 has a tip portion including a coating layer 62 disposed inside the wound electrode body 20, but a part of the lead portion protrudes outside the wound electrode body 20. For this reason, the conducting wire 17 that is a lead wire connected to the reference electrode 60 is not disposed inside the wound electrode body 20.

  The reference electrode 60 may be formed integrally with an insulating film (not shown) folded in a box shape between the battery case body 41 and the wound electrode body 20. In this case, the reference electrode terminal 18 can be directly connected to the reference electrode 60. For this reason, since it has only the reference electrode 60 which has the said thickness other than the separator 23 between the positive electrode sheet 21 and the negative electrode sheet 22 regardless of having a lead wire, between mixture layers and separators Adhesion is maintained.

The reference electrode 60 is disposed between the positive electrode sheet 21 and the negative electrode sheet 22 as in the first embodiment. In addition, if the reference electrode 60, the positive electrode sheet 21, and the negative electrode sheet 22 are flat at a portion where the reference electrode 60 is disposed, the reference electrode 60 is disposed so as to be parallel to each other. If the reference electrode 60, the positive electrode sheet 21, and the negative electrode sheet 22 are curved surfaces, the average distance between the positive electrode sheet 21 and the negative electrode sheet 22 is arranged to be the smallest. By setting it as this structure, the fall of the adhesiveness between the mixture layer and separator by arrangement | positioning of the reference electrode 60 can be suppressed.

<Method for producing reference electrode>
With reference to FIGS. 11 to 13, a method for manufacturing the lithium ion secondary battery 2 having the reference electrode 60 will be described focusing on differences from the first embodiment. In place of the aluminum wire 11 of the reference electrode 10, the reference electrode 60 is made of a planar substrate 61 (planar aluminum material) made of aluminum and covered with an insulating layer 63 except for the portion that becomes the electrode surface at the tip. Form as a base material.

  The covering layer 62 is formed at the exposed tip of the planar substrate 61 so as to cover the planar substrate 61. As shown in FIG. 13, the reference electrode 60 is connected to the conducting wire 17. Further, the reference electrode 60 may be routed and directly connected to the reference electrode terminal 18. Further, the tip portion of the reference electrode 60 and the lead portion without the coating layer are sandwiched between the positive electrode and the negative electrode of the wound electrode body 20. At this time, the conductive wire 17 is preferably not sandwiched between the wound electrode bodies 20.

  After assembling the battery, the reference electrode 60 is energized to form the covering layer 62 and complete. In the first embodiment, the uniform coating layer 12 is formed by rotating the aluminum wire 11. However, in this embodiment, the planar substrate 61 is sandwiched between the positive electrode sheet 21 and the negative electrode sheet 22. Therefore, it cannot be performed when the coating layer 62 is formed.

  Therefore, if the planar substrate 61, the positive electrode sheet 21, and the negative electrode sheet 22 are flat at the portion where the reference electrode 60 is disposed, the planar substrate 61 is disposed so that they are parallel to each other. Further, if the planar substrate 61, the positive electrode sheet 21, and the negative electrode sheet 22 are curved surfaces, the planar substrate 61 is adjusted by bending as much as possible so that there is no gap between the positive electrode sheet 21 and the negative electrode sheet 22. Deploy. If the reference electrode 60 is sufficiently thin and flexible and does not hinder the bending of the wound electrode body 20, the reference electrode 60 is disposed so as to be laminated between the positive electrode sheet 21 and the negative electrode sheet 22.

By passing through this process, after energizing between the positive electrode 21 or the negative electrode 22, the coating layer 62 can be uniformly formed on the surface to be the electrode surface. With this manufacturing method, it is possible to obtain a reference electrode including a porous lithium aluminum alloy having low strength on the electrode surface.
With the invention according to the second embodiment described above, it is possible to provide a lithium ion secondary battery having a reference electrode with stability and durability, and a method for manufacturing the lithium ion secondary battery.

  As a modification of the embodiment, the first coating layer may be formed on one surface of the planar substrate and the second coating layer may be formed on the other surface. Further, the portion of the planar substrate covered by the first coating layer and the portion of the planar substrate covered by the second coating layer have overlapping portions with the planar substrate interposed therebetween. You may do it. That is, in the overlapping portion, the planar substrate may not be covered with the insulating layer. In this case, it is preferable that the planar substrate has mechanical strength to such an extent that the shape can be maintained independently.

Next, an example according to the second embodiment will be described with reference to FIGS. 14 to 19 showing configurations of a reference electrode and a lithium ion secondary battery.
The lithium ion secondary battery 100 was manufactured as follows. First, as shown in FIGS. 14 and 15, a 2 μm-thick aluminum film 161 (described above) is formed on a convex 20 μm-thick polyimide resin sheet 169 (part of the insulating layer 63 described above). A planar substrate 61) was formed. The wide portion of the polyimide resin sheet 169 that did not protrude was formed in accordance with the size of the inner surface of the battery case so as to be an insulating film provided between the battery case body and the wound electrode body.

  The aluminum film 161 was drawn from the tip of the protruding portion of the polyimide resin sheet 169 to the upper end of the wide portion of the figure through the wide area of the polyimide resin sheet 169. The end of the aluminum film 161 on the wide portion side of the polyimide resin sheet 169 was connected to the reference electrode terminal 168 in FIG. 16 when the battery was assembled. Further, a polyimide resin film 163 having a thickness of 1 to 2 μm (a part of the insulating layer 63 described above) was formed so as to cover the aluminum film 161 while leaving the left end portion 170 serving as an electrode surface. The width of the tip portion 170 was 0.05 μm.

  As described above, by adopting a configuration in which the polyimide resin sheet 169 supports the aluminum film 161, the mechanical strength of the aluminum film 161 is increased and the wire is not easily disconnected. Specifically, breakage of the aluminum film 161 due to mechanical stress based on the expansion / contraction of the positive electrode or the negative electrode accompanying ion insertion / desorption or temperature change is suppressed.

  As described above, the first lead portion 174 was formed as a portion including the aluminum film 161 whose both surfaces were covered with the insulating film and the polyimide resin film and the region of the insulating film surface was routed. Further, the second lead portion 167 was formed so as to connect the tip portion 170 and the first lead portion 174.

  After assembling the lithium ion secondary battery, the reference electrode 160 was formed by energizing and forming the coating layer 162 containing a lithium aluminum alloy. For this reason, the coating layer 162 is not formed at this stage. For convenience, the electrode before energization is also referred to as the reference electrode 160. In FIG. 15, the coating layer 162 is formed so as to cover the surface of the aluminum film 161 at the tip portion 170.

  Next, as shown in FIGS. 16 and 17, the reference electrode before forming the positive and negative electrodes and the coating layer containing the lithium aluminum alloy was assembled. In FIG. 16, the battery case 140 including the battery case main body 141 and the sealing lid 142 and the safety valve are not shown.

The thickness of the mixture layer is preferably 20 to 32.5 times, and particularly preferably 20 times the thickness of the aluminum thin film (aluminum film 161). For example, if the mixture layer thickness is 40 μm, the thickness of the aluminum thin film can be 2 μm. By setting it as this thickness, the fall of the battery performance by reference electrode insertion can be suppressed.
In this example, the positive electrode sheet 121 has a positive electrode mixture layer of 60 μm in consideration of the balance with battery performance. The negative electrode sheet 122 had a negative electrode mixture layer of 65 μm.

  The positive electrode sheet 121 and the negative electrode sheet 122 were laminated via a polyethylene film 123, and another polyethylene film was laminated so that the positive electrode sheet 121 was further sandwiched between polyethylene films. When laminating the negative electrode sheet 122 and the polyethylene film 123, the tip part 170 of the reference electrode 160 and a part of the second lead part 167 are sandwiched between the positive electrode sheet 121 and the negative electrode sheet 122. .

The direction in which the reference electrode is sandwiched is the direction in which the electrode surface comes to the polyethylene film 123 side, so that the electrode surface and the negative electrode sheet are not in direct contact.
The laminated body thus superposed was wound, and the obtained wound body was crushed from the side surface direction to produce a flat wound electrode body 120. Further, as shown in the figure, the first lead portion 174 of the reference electrode 160 was bent into a box shape to form an insulating film between the battery case body 141 made of aluminum and the wound electrode body 120.

  The positive electrode member 133 and the positive electrode sheet 121 were connected, and the negative electrode member 136 and the negative electrode sheet 122 were further connected. Further, the reference electrode terminal 168 and the reference electrode were connected, and the sealing lid 142 was attached. Insulating members 132 and 135 were attached to the positive electrode member 133 and the negative electrode member 136, respectively, and the exposed portions were used as the positive electrode terminal portion 131 and the negative electrode terminal portion 134, respectively.

A rectangular plate-shaped safety valve was attached to the sealing lid 142. The positive electrode terminal portion 131 and the reference electrode terminal 168 were electrically connected, current was passed from the reference electrode 160 toward the positive electrode sheet 121, and the coating layer 162 containing a lithium aluminum alloy was formed on the surface of the aluminum film 161.
The lithium ion secondary battery 100 was completed by completing the reference electrode.

  The reference electrode and lithium ion secondary battery according to the example were evaluated. FIG. 18A shows a cross section of the wound electrode body. In the drawing, a negative electrode mixture layer 155, a polyethylene film 123, a positive electrode mixture layer 152, and a positive electrode current collector plate 151 are laminated in order from the negative electrode current collector plate 154 of the negative electrode sheet 122 to the right. The second lead portion 167 of the reference electrode 160 appears as a thin layer sandwiched between the negative electrode mixture layer 155 and the polyethylene film 123.

  As shown to Fig.18 (a), the reference electrode concerning a present Example is an electrode of the thin film sensor shape which has only a part thinner than any of a positive mix layer and a negative mix layer. Even if such a reference electrode is disposed between the mixture layer and the separator, the adhesion between the mixture layer and the separator is maintained, so that a decrease in battery performance is suppressed.

  On the other hand, FIG. 18B shows a reference electrode in the form of a sensor with a lead wire as a comparative example. Instead of the second lead portion 167 of the reference electrode 160, the lead wire 117 is connected in the reference electrode of the comparative example. In the cross section in the figure, the lead wire 117 is sandwiched between two layers of polyethylene film 123.

As shown in FIG. 18B, this comparative example includes a lead wire having a diameter larger than the thickness of the positive electrode mixture layer or the negative electrode mixture layer. When such a reference electrode is inserted between the mixture layer and the separator or in the separator layer, the adhesion between the mixture layer and the separator is deteriorated and the battery performance is deteriorated.
On the other hand, when the diameter of the lead wire 117 is smaller than any thickness of the positive electrode mixture layer and the negative electrode mixture layer, the adhesion between the mixture layer and the separator is maintained, but the mechanical strength is low. There is a risk of disconnection.

FIG. 19 shows the change over time in the electrical resistance of a battery incorporating the reference electrode. Since the reference electrode according to this example is a thin film sensor-shaped electrode, the increase in the electric resistance of the battery is slower than that of the sensor-shaped reference electrode with a lead wire according to the comparative example.
This is explained as follows. That is, when a reference electrode smaller than the thickness of the positive electrode mixture layer or the negative electrode mixture layer is incorporated, the gap between the positive electrode and the negative electrode does not occur so much that the movement of the electrolyte solution can be suppressed. On the other hand, when a reference electrode larger than the thickness is incorporated, the movement of the electrolyte solution becomes active due to the gap formed between the positive and negative electrodes, and a reaction distribution is generated. For this reason, it is considered that a difference occurs in the increase rate of the electric resistance.

  As mentioned above, although this invention was demonstrated according to the said embodiment and Example, it is not limited only to the structure of the said embodiment and Example, In the scope of the invention of the claim of a claim of this application It goes without saying that various variations, modifications, and combinations that can be made by those skilled in the art are included.

10 Reference electrode 11 Core material (aluminum wire)
DESCRIPTION OF SYMBOLS 12 Covering layer 13 Insulating layer 14 Lithium aluminum alloy 15 Protrusion part 21 Negative electrode sheet 22 Negative electrode sheet 23 Separator 27 Non-aqueous electrolyte 51 Negative electrode collector 52 Negative electrode active material (negative electrode mixture layer)
54 Negative electrode current collector 55 Negative electrode active material (negative electrode mixture layer)
Reference electrode 61 Planar substrate 62 Cover layer 63 Insulating layer

Claims (15)

A positive electrode and a negative electrode;
A separator interposed between the positive electrode and the negative electrode;
A non-aqueous electrolyte containing lithium ions and filled between the positive electrode and the negative electrode;
A reference electrode disposed in contact with the non-aqueous electrolyte, and
The reference electrode has a base material made of aluminum and a coating layer containing a lithium aluminum alloy.
Lithium ion secondary battery. The base material is a core made of aluminum,
The coating layer is disposed around the core material,
The lithium ion secondary battery according to claim 1. The coating layer extends radially from the core material to the periphery of the core material, and has a plurality of protrusions having a higher aluminum ratio than the lithium aluminum alloy,
The lithium aluminum alloy is disposed between the plurality of protrusions.
The lithium ion secondary battery according to claim 2.   4. The lithium ion secondary battery according to claim 2, wherein a cross-sectional area of the core material is 10% or more and 90% or less of a cross-sectional area of the reference electrode.   The lithium ion secondary battery according to any one of claims 2 to 4, wherein a diameter of a cross section of the reference electrode is 0.2 mm or less.   The lithium ion secondary battery according to any one of claims 2 to 4, wherein a diameter of a cross section of the reference electrode is 0.1 mm or less. The base material is a planar substrate made of aluminum,
The coating layer is disposed on at least a part of at least one surface of the planar substrate,
The thickness of the reference electrode is smaller than the positive electrode mixture layer of the positive electrode and the negative electrode mixture layer of the negative electrode,
The lithium ion secondary battery according to claim 1.   The thickness of the said reference electrode is a lithium ion secondary battery of Claim 7 which is below 1/20 of the thinnest mixture layer among the said positive mix layer or the said negative mix layer. The coating layer is disposed on at least a part of one surface of the planar substrate,
An insulating layer is disposed on the other surface of the planar substrate;
The planar substrate is an aluminum film formed on the insulating layer.
The lithium ion secondary battery according to claim 7 or 8. Placing a separator between the positive and negative electrodes,
Filling a non-aqueous electrolyte containing lithium ions between the positive electrode and the negative electrode;
An aluminum material is disposed so as to come into contact with the non-aqueous electrolyte,
A reference electrode is formed by forming a coating layer containing a lithium aluminum alloy on the surface of the aluminum material by passing a current between the aluminum material and the positive electrode or between the aluminum material and the negative electrode.
A method for producing a lithium ion secondary battery.   The method for manufacturing a lithium ion secondary battery according to claim 10, wherein the aluminum material is an aluminum wire.   The method of manufacturing a lithium ion secondary battery according to claim 11, wherein the aluminum wire is rotated when the reference electrode is formed.   The cross-sectional area of the core material in which the lithium aluminum alloy of the aluminum wire is not formed when forming the reference electrode is formed so as to be 10% or more and 90% or less of the cross-sectional area of the reference electrode. A method for producing a lithium ion secondary battery according to 11 or 12. The aluminum material is planar,
The covering layer is formed on at least a part of at least one surface of the aluminum material,
Forming the reference electrode such that the thickness of the reference electrode is smaller than the positive electrode mixture layer of the positive electrode and the negative electrode mixture layer of the negative electrode;
The manufacturing method of the lithium ion secondary battery of Claim 10. The reference electrode is formed so that the thickness of the reference electrode is 1/20 or less of the thinnest mixture layer of the positive electrode mixture layer or the negative electrode mixture layer.
The manufacturing method of the lithium ion secondary battery of Claim 14.