JP2010073558A - Electrochemical cell, battery pack, and vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical cell in which an electrode potential can be measured accurately. <P>SOLUTION: The electrochemical cell 10 includes a plurality of electrodes 23, 26 and reference electrodes 30. The plurality of the electrodes 23, 26 are laminated in electrolytic solution via separators 27. The reference electrodes 30 are electrically insulated from the plurality of electrodes 23, 26, and arranged in projection planes of the electrodes 23, 26 in the laminating direction of the electrodes 23, 26. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrochemical cell, a battery pack, and a vehicle. The present invention particularly relates to an electrochemical cell and an assembled battery and vehicle using the same as a secondary battery.

  Secondary batteries such as lithium batteries and nickel metal hydride batteries are actively developed as power sources for driving motors of electric vehicles (EV) and hybrid electric vehicles (HEV).

As such a secondary battery, an electrochemical cell as shown in Patent Document 1 below is known from the viewpoint of evaluating output characteristics. The electrochemical cell disclosed in Patent Document 1 has a positive electrode, a negative electrode, and two reference electrodes arranged near the sides of the positive electrode and the negative electrode. According to the electrochemical cell having such a configuration, the internal resistance of the electrochemical cell is separated into the positive electrode, the negative electrode, and the resistance component of the electrolytic solution by measuring the potential of the positive electrode and the negative electrode with reference to each reference electrode. Can be detected.
2005-19116

  However, the electrochemical cell has a problem in that the potentials of the positive electrode and the negative electrode cannot be accurately measured because the reference electrode is disposed adjacent to the sides of the positive electrode and the negative electrode.

  The present invention has been made to solve the above-described problems. Accordingly, an object of the present invention is to provide an electrochemical cell that can accurately measure the potential of an electrode.

  Another object of the present invention is to provide an assembled battery and a vehicle using the electrochemical cell as a secondary battery.

  The above object of the present invention is achieved by the following means.

  The electrochemical cell of the present invention has a plurality of electrodes and a reference electrode. The plurality of electrodes are stacked in the electrolytic solution via a separator. The reference electrode is electrically insulated from the plurality of electrodes and is disposed within a projection plane of the electrode in the stacking direction of the electrodes.

  In the assembled battery of the present invention, a plurality of secondary batteries composed of the electrochemical cells are connected in series, in parallel, or a combination of series and parallel.

  The vehicle of the present invention is equipped with a secondary battery made of the electrochemical cell or the assembled battery as a driving power source.

  According to the electrochemical cell of the present invention, since the reference electrode is arranged in the projection plane of the electrode, the potential in the plane of the electrode can be measured. Therefore, the potential of the electrode can be accurately measured.

  According to the assembled battery and the vehicle of the present invention, since the output characteristics of the electrochemical cell are accurately measured, the reliability is improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following embodiments, a case where the electrochemical cell of the present invention is applied to a secondary battery will be described as an example.

(First embodiment)
FIG. 1 is a cross-sectional view showing a schematic configuration of an electrochemical cell according to the first embodiment of the present invention. In the electrochemical cell 10 of the present embodiment, a reference electrode is disposed at the center of the projection surface in the stacking direction of a plurality of electrodes stacked in the electrolytic solution via a separator. In addition, the electrochemical cell 10 of this Embodiment is a lithium secondary battery, for example.

  As shown in FIG. 1, the electrochemical cell 10 of the present embodiment includes a power generation element 20, a reference electrode 30, and an exterior member 40. The power generation element 20 and the reference electrode 30 are accommodated in the exterior member 40 together with the electrolytic solution.

  The power generation element 20 generates electricity using a chemical reaction of a substance. The power generation element 20 has a flat rectangular shape, and a positive electrode 23 in which a positive electrode active material layer 22 is formed on both surfaces of a positive electrode current collector 21, and a negative electrode active material layer 25 is formed on both surfaces of a negative electrode current collector 24. A plurality of the negative electrodes 26 are stacked with a separator 27 interposed therebetween. A terminal negative electrode 26 a in which a negative electrode active material layer 25 is formed on one surface of a negative electrode current collector 24 is stacked on a top layer of a plurality of positive electrodes 23 and negative electrodes 26 via a separator 27. A terminal positive electrode 23 a in which a positive electrode active material layer 22 is formed on one surface of a positive electrode current collector 21 is stacked via a separator 27 on the lowermost layer of a plurality of positive electrodes 23 and negative electrodes 26. Each of the positive electrode current collector 21 and the negative electrode current collector 24 is formed of a conductive material such as an aluminum foil and a stainless steel (SUS) foil, and is connected to an electrode tab (not shown). The electric power generated by the power generation element 20 is taken out through the electrode tab. Since the power generation element 20 itself is the same as the power generation element of a general secondary battery, detailed description thereof is omitted. Further, unlike the present embodiment, the power generating element 20 has a bipolar electrode in which a positive electrode active material is formed on one surface of a current collector and a negative electrode active material is formed on the other surface via a separator. A stacked structure may be used.

  The reference electrode 30 is used for measuring the potential of the positive electrode 23 or the negative electrode 26 of the power generation element 20. The reference electrode 30 includes a first reference electrode 30a disposed above the uppermost terminal negative electrode 26a of the power generation element 20, and a second reference electrode disposed below the lowermost terminal positive electrode 23a of the power generation element 20. 30b. The first and second reference electrodes 30a and 30b have a flat elliptical shape and are made of metallic lithium. The first reference electrode 30 a is disposed on the upper side of the negative electrode current collector 24 of the uppermost terminal negative electrode 26 a of the power generation element 20 while being electrically insulated by the porous insulating member 31. The second reference electrode 30 b is disposed under the positive electrode current collector 21 of the lowermost terminal positive electrode 23 a of the power generation element 20 while being electrically insulated by the porous insulating member 31. Lead wires 32 are connected to the end portions of the first and second reference electrodes 30 a and 30 b, and the lead wires 32 extend through the inside of the insulating member 31 to the outside of the power generation element 20. The lead wire 32 is made of nickel, and the tip portion is led out of the exterior member 40. From the standpoint of accurately measuring the potential at the measurement point while suppressing the influence from other parts, the area of the reference electrode 30 is preferably 15% or less of the area of the positive electrode and the negative electrode. Further, unlike the present embodiment, the reference electrode 30 may be formed in a flat circular shape or a flat polygonal shape (triangle, quadrangle) in which corners are formed in an arc shape.

  The exterior member 40 accommodates the power generation element 20 and the reference electrode 30. The exterior member 40 has a flat rectangular shape and is formed of first and second exterior members 40a and 40b having electrical insulation. The first exterior member 40a has a recess that houses the power generation element 30, and the second exterior member 40b is connected to the first exterior member 40a so as to sandwich the power generation element 30 at the peripheral edge of the recess. They are joined together by thermal fusion. In the exterior member 40, an electrolytic solution is housed together with the power generation element 20 and the reference electrode 30.

  Next, with reference to FIG. 2, the structure of the electrochemical cell 10 of this Embodiment is demonstrated in detail. FIG. 2 is a partially enlarged view of the electrochemical cell shown in FIG.

  As shown in FIG. 2, the electrochemical cell 10 according to the present embodiment is disposed between the uppermost terminal negative electrode 26 a of the power generation element 20 and the first exterior member 40 a (hereinafter simply referred to as the exterior member 40). The first reference electrode 30a (hereinafter simply referred to as the reference electrode 30).

  The reference electrode 30 is disposed inside the porous insulating member 31 and is electrically insulated from the negative electrode current collector 24 of the terminal negative electrode 26a of the uppermost layer of the power generation element 20, while the porous insulating member 31 Ion conduction is possible by the electrolyte that penetrates through the pores.

  The exterior member 40 is a laminate film composed of a three-layer sheet, and has a thermal fusion layer 41, a metal layer 42, and an outermost layer 43 from the inner surface facing the reference electrode 30 toward the surface. .

  The insulating member 31 is formed of, for example, a porous material such as polypropylene and absorbs the electrolytic solution therein. The insulating member 31 is disposed between the terminal negative electrode 26 a and the reference electrode 30 to electrically insulate the terminal negative electrode 26 a and the reference electrode 30, and is disposed between the exterior member 40 and the reference electrode 30. And an upper insulating member (protective insulating member) to be laminated. The reference electrode 30 is disposed inside the insulating member 31 so as to be sandwiched between the upper insulating member and the lower insulating member. Such an insulating member 31 is formed using, for example, a general casting method. More specifically, the insulating member is formed by first forming the lower insulating member, placing the reference electrode 30 on the lower insulating member, and then forming the upper insulating member so as to cover the lower insulating member and the reference electrode 30. 31 is formed.

  From the viewpoint of reliably absorbing the viscous electrolyte in the insulating member 31, the porosity (porosity) of the porous insulating member 31 is preferably 20% or more. Further, from the viewpoint of preventing deterioration of the insulating member 31, the insulating member is preferably formed of a material that does not react with lithium metal (for example, polypropylene resin, polyethylene resin, etc.). Furthermore, from the viewpoint of suppressing overvoltage, the distance D of the reference electrode 30 from the terminal negative electrode 26a is preferably 1 mm or less.

  As described above, according to the electrochemical cell 10 of the present embodiment configured, the reference electrode 30 is located near the lower portion of the central portion of the terminal positive electrode 23a and the central portion of the terminal negative electrode 26a via the porous insulating member 31. It is arrange | positioned in the upper part vicinity of. Therefore, it is possible to measure the potential at the center of the electrode, which can be considered as the average potential of the electrode, using the reference electrode 30. In addition, since the technique itself which measures the electric potential of an electrode using a reference electrode is a general electric potential measurement technique, detailed description is abbreviate | omitted.

  Next, with reference to FIG. 3, the effect of the electrochemical cell of this Embodiment is demonstrated.

  FIG. 3 is a diagram for explaining the operation and effect of the electrochemical cell shown in FIG. FIG. 3A is a schematic diagram illustrating the relationship between the position of the reference electrode in the electrode and the potential of the electrode measured using the reference electrode, and FIG. 3B corresponds to FIG. It is a figure for demonstrating the position of a reference pole. The broken line in FIG. 3A shows the variation in the potential of the electrode when the output immediately after the current output is not stable, and the solid line in FIG. 3B shows the variation in the potential of the electrode after the output is stabilized. Yes.

  As indicated by a broken line in FIG. 3A, a large potential variation occurs in the electrode surface immediately after the current is output. Specifically, immediately after the current output from which the current starts to be taken out from the electrode tab 45, the potential in the region near the end of the electrode to which the electrode tab 45 is connected increases, while the electrode to which the electrode tab 45 is connected. The potential in the region far from the end of the region tends to be low. More specifically, at the five measurement positions (a) to (e) shown in FIG. 3B, the highest potential is measured at the position (b) closest to the electrode tab 45 and the farthest from the electrode tab 45. The lowest potential is measured at position (d). Note that at position (c) and position (e), a higher potential is measured at position (c). At the center position (a) of the electrode surface, the average potential of the five points (a) to (e) is measured.

  Then, as lithium ions diffuse in the electrode surface over time, the potential variation in the electrode surface is reduced, and the potential is stabilized to the potential indicated by the solid line in FIG. At this time, if the solid line and the broken line in FIG. 3A are compared, it can be seen that the potential measured before and after the stabilization changes greatly at the positions (b) and (d). It can also be seen that the potential measured at the position (c) and the position (e) changes before and after the stabilization. On the other hand, at the center position (a) of the electrode surface, it can be seen that there is no change in the potential measured before and after stabilization. It can also be seen that the potential measured at the center position (a) of the electrode surface shows the average potential of the entire electrode.

  Therefore, a more accurate electrode potential can be obtained by arranging the reference electrode 30 near the center of the electrode surface and measuring the potential of the center of the electrode surface using the reference electrode 30. From the viewpoint of suppressing the potential difference between the measured potential and the potential at the center of the electrode surface to 50% or less, the reference electrode 30 is centered on the center position of the electrode and the distance from the center position of the electrode to the electrode tab. It is preferable to arrange in a region on the inner periphery of the circumference having a radius of half the length.

  Next, the relationship between the distance of the reference electrode from the electrode and the overvoltage will be described with reference to FIG.

  FIG. 4 is a diagram showing the relationship between the distance of the reference electrode from the negative electrode and the overvoltage in the electrochemical cell shown in FIG. The horizontal axis in FIG. 4 is the distance of the reference electrode from the negative electrode, and the vertical axis is the overvoltage (negative electrode potential).

  As shown in FIG. 4, in the electrochemical cell 10 of the present embodiment, the distance of the reference electrode from the negative electrode (that is, the distance between the lower surface of the reference electrode 30 and the opposing surface of the negative electrode current collector 24 of the terminal negative electrode 26a) D It can be seen that the overvoltage increases with increasing. This is because the insulating member 31 acts as an electrical resistance. Therefore, in order to measure the potential of the electrode more accurately, it is preferable that the distance D of the reference electrode from the electrode is smaller. From the viewpoint of suppressing the ratio of the overvoltage component due to the distance of the reference electrode from the negative electrode to the entire overvoltage (about 200 to 240 mV) to 20% or less, the distance of the reference electrode from the negative electrode, that is, the thickness of the lower insulating member The thickness is preferably 1 mm or less.

  And according to the electrochemical cell 10 of this Embodiment comprised in this way, the reference pole 30 is the lower part vicinity of the center part of the terminal positive electrode 23a through the porous insulating member 31, and the center of the terminal negative electrode 26a. It is arrange | positioned in the upper part vicinity of a part. Therefore, it is possible to measure the potential at the center of the electrode, which is small in potential fluctuation and considered as the average potential of the electrode. As a result, the electrode potential is accurately measured.

(Modification)
In the above-described embodiment, the porous material is used as an insulating member that electrically insulates the reference electrode and the electrode so that the reference electrode is in contact with the electrolytic solution. However, an insulating member may be disposed only between the reference electrode and the electrode to electrically insulate the reference electrode and the electrode.

  FIG. 5 is a view for explaining a modification of the electrochemical cell of the present embodiment.

  As shown in FIG. 5, in the electrochemical cell according to this modification, the insulating member 33 is disposed only between the terminal negative electrode 26 a of the uppermost layer of the power generation element 20 and the reference electrode 30. The insulating member 33 is formed from an insulating material having no holes. The upper surface and side surfaces of the reference electrode 30 are exposed in the electrolytic solution. With such a configuration, the process of forming holes in the insulating member using a casting method or the like is omitted, and the manufacturing process of the electrochemical cell is simplified.

  In the electrochemical cell 10 described above, a plurality of battery modules 50 are connected in series or in parallel as secondary batteries to form a battery module 50, and a plurality of battery modules 50 are further connected in series or in parallel to form a battery pack 60. Can do. In the battery module 50, a plurality of the electrochemical cells 10 are stacked and accommodated in a module case, and the electrochemical cells 10 are connected in parallel. FIG. 6 is a perspective view of the assembled battery in the present embodiment. The produced battery modules 50 are connected to each other using an electrical connection member such as a bus bar, and are stacked in a plurality of stages. The number of electrochemical cells 10 used in the assembled battery 60 and the number of stacked battery modules 50 are determined according to the battery capacity and output of the vehicle on which the battery is mounted.

  FIG. 7 is a schematic configuration diagram showing an electric vehicle as a vehicle in the present embodiment. The above-described electrochemical cell 10, battery module 50, and / or assembled battery 60 can be mounted on a vehicle such as an automobile or a train and used as a power source for driving an electric device such as a motor. As shown in FIG. 7, the electric vehicle 70 of the present embodiment has the assembled battery 60 mounted under the seat at the center of the vehicle body. The drive wheels are rotated by the motor supplied with electric power from the assembled battery 60, and the electric vehicle 70 travels.

  As described above, the described embodiment has the following effects.

  (A) The electrochemical cell according to the present embodiment includes a plurality of electrodes stacked in an electrolyte solution via a separator, and is electrically insulated from the plurality of electrodes, and within the projection plane of the electrodes in the electrode stacking direction. And a reference electrode disposed on the substrate. Therefore, since the reference electrode is disposed in the projection plane of the electrode, the potential in the plane of the electrode can be measured. As a result, the potential of the electrode can be measured more accurately than when the reference electrode is arranged near the side of the electrode and the potential at the end of the electrode is measured. Further, the distance between the electrode and the reference electrode can be kept constant for a long time.

  (B) The electrochemical cell according to the present embodiment further includes a lower insulating member that is disposed between the electrode facing the reference electrode and the reference electrode and electrically insulates the electrode and the reference electrode. Therefore, the reference electrode and the electrode can be electrically insulated.

  (C) The electrochemical cell of the present embodiment further includes an exterior member that accommodates a plurality of electrodes, and the reference electrode is disposed between the outermost layer electrode and the exterior member in the stacking direction among the plurality of electrodes. Is done. Therefore, the potential of the outermost electrode can be accurately measured.

  (D) The shape of the reference pole is a circle, an ellipse, or a polygon whose corners are arcs. Therefore, it is possible to prevent power from being concentrated on the reference extreme part. As a result, the potential of the electrode can be measured over the entire reference electrode.

  (E) The electrochemical cell of the present embodiment further includes an electrode tab connected to the end portion of the electrode, and the reference electrode is centered on the center position of the electrode in the projection plane of the electrode, and the center of the electrode It arrange | positions in the area | region inside the circumference which makes a radius the length of the half of the distance from a position to an electrode tab. Therefore, the potential difference between the measured potential and the potential at the center of the electrode surface can be suppressed to 50% or less.

  (F) The reference electrode is disposed at the center of the projection plane of the electrode. Therefore, the potential fluctuation at the time of current output is small, and the potential at the center of the electrode which can be considered as the average potential of the electrode can be measured. As a result, the electrode potential can be measured more accurately.

  (G) It further has an upper insulating member disposed between the exterior member and the reference electrode, and the reference electrode is disposed between the upper insulating member and the lower insulating member. Therefore, when the upper insulating member and the lower insulating member sandwich the reference electrode, the reference electrode can be more reliably insulated. Moreover, an electrochemical cell can be smoothed by disposing an insulating member so as to surround the reference electrode.

  (H) The thickness of the lower insulating member disposed between the reference electrode and the electrode is 1 mm or less. Therefore, the ratio of the overvoltage component due to the distance of the reference electrode from the electrode to the entire overvoltage can be suppressed to 20% or less. As a result, the potential can be measured more accurately.

  (I) At least one of the plurality of electrodes includes lithium as an electrode active material, and the insulating member is formed of an insulating material that is stable against lithium. Therefore, deterioration of the insulating member is prevented.

  (J) The insulating member is made of a porous material having a porosity of 20% or more. Therefore, the electrolytic solution is reliably absorbed inside the insulating member.

  (K) In the assembled battery of the present embodiment, a plurality of secondary batteries made of the electrochemical cells are connected in series, in parallel, or a combination of series and parallel. Therefore, since the output characteristics of the electrochemical cell are accurately measured, the reliability is improved.

  (L) The electric vehicle of the present embodiment is equipped with a secondary battery made of the electrochemical cell or the assembled battery as a driving power source. Therefore, since the output characteristics of the electrochemical cell are accurately measured, the reliability is improved.

(Second Embodiment)
Next, with reference to FIG. 8, the electrochemical cell in the 2nd Embodiment of this invention is demonstrated. In the present embodiment, a reference electrode is disposed between electrodes adjacent to each other in the stacking direction.

  FIG. 8 is a cross-sectional view showing a schematic configuration of an electrochemical cell according to the second embodiment of the present invention. As shown in FIG. 8, in the electrochemical cell of the present embodiment, reference electrodes 30 are respectively disposed between the positive electrodes 23 and the negative electrodes 26 adjacent in the stacking direction. The configuration of the electrochemical cell in the present embodiment is the same as that in the first embodiment except that a reference electrode is disposed between electrodes adjacent to each other in the stacking direction. Description is omitted.

  In the power generation element 20, a positive electrode 23 in which a positive electrode active material layer 22 is formed on one side of a positive electrode current collector 21 and a negative electrode 26 in which a negative electrode active material layer 25 is formed on one side of a negative electrode current collector 24 are separators. 27, a plurality of unit cell layers 28 are stacked.

  The reference electrode 30 is disposed between the unit cell layers 28 adjacent in the stacking direction while being electrically insulated by the porous insulating member 31. The insulating member 31 includes an upper insulating member and a lower insulating member, and the reference electrode 30 is disposed inside the insulating member 31 so as to be sandwiched between the upper insulating member and the lower insulating member.

  With such a configuration, in addition to the uppermost and lowermost electrodes of the power generation element 20, the potential of the electrode inside the power generation element 20 can be measured. The order in which the single battery layers 28 are stacked is not limited to the above embodiment in which the reference electrodes 30 are disposed between the positive electrodes 23 and the negative electrodes 26 adjacent to each other in the stacking direction. The single battery layer 28 may be laminated so that the reference electrode 30 is disposed between the two.

  As described above, the described embodiment has the following effects in addition to the effects of the first embodiment.

  (M) In the electrochemical cell of the present embodiment, a reference electrode is disposed between electrodes adjacent in the stacking direction. Therefore, in addition to the potential of the outermost electrode in the stacking direction, the potential of the inner electrode can be measured.

(Third embodiment)
In the present embodiment, the reference electrode is disposed inside the separator.

  FIG. 9 is a diagram for explaining an electrochemical cell according to the third embodiment of the present invention.

  As shown in FIG. 9, in the electrochemical cell of the present embodiment, a reference electrode 30 is disposed inside the separator 27. Except for the point that the reference electrode is arranged inside the separator, the configuration of the electrochemical cell in the present embodiment is the same as that in the first embodiment, and a detailed description thereof will be omitted.

  The separator 27 is configured by stacking an upper separator member and a lower separator member, and the reference electrode 30 is disposed inside the separator 27 so as to be sandwiched between the upper separator member and the lower separator member.

  With such a configuration, the separator 27 is also used as an insulating member that electrically insulates the reference electrode and the electrode, thereby simplifying the configuration of the electrochemical cell.

  As described above, the described embodiment has the following effects in addition to the effects of the first and second embodiments.

  (N) The reference electrode in the present embodiment is disposed inside the separator. Therefore, the structure of the electrochemical cell can be simplified by using the separator also as the insulating member.

  As described above, the electrochemical cell, the assembled battery, and the vehicle of the present invention have been described in the first to third embodiments. However, it goes without saying that the present invention can be appropriately added, modified, and omitted by those skilled in the art within the scope of the technical idea.

  For example, in the first to third embodiments, the reference electrodes are arranged on both the uppermost layer and the lowermost layer of the power generation element. However, the arrangement form of the power generation elements is not limited to the above-described embodiment. For example, in the first embodiment, the reference electrode may be arranged only in one of the uppermost layer and the lowermost layer of the power generation element. Good. In the second and third embodiments, at least one of the uppermost layer and the lowermost reference electrode of the power generation element may be omitted.

  In the first to third embodiments, the case where the electrochemical cell of the present invention is used as a secondary battery has been described. However, the electrochemical cell of the present invention may be used as a capacitor for storing electric charges. Moreover, an electrode can be called a working electrode, a counter electrode, etc. according to the objective.

It is sectional drawing which shows schematic structure of the electrochemical cell in the 1st Embodiment of this invention. It is the elements on larger scale of the electrochemical cell shown in FIG. FIG. 3A is a schematic diagram illustrating the relationship between the position of the reference electrode in the electrode and the potential of the electrode measured using the reference electrode, and FIG. 3B corresponds to FIG. It is a figure for demonstrating the position of a reference pole. It is a figure which shows the relationship between the distance of the reference electrode from the negative electrode and overvoltage in the electrochemical cell shown in FIG. It is a figure for demonstrating the modification of the electrochemical cell shown in FIG. It is a perspective view of the assembled battery which used the electrochemical cell shown in FIG. 1 as a secondary battery. It is a schematic block diagram which shows the electric vehicle which used the electrochemical cell shown in FIG. 1 as a secondary battery. It is a figure for demonstrating the electrochemical cell in the 2nd Embodiment of this invention. It is a figure for demonstrating the electrochemical cell in the 3rd Embodiment of this invention.

Explanation of symbols

10 electrochemical cell,
20 power generation elements,
23 positive electrode,
26 negative electrode,
27 separator,
28 cell layer,
30 reference electrode,
31, 33 Insulating member (insulating member, protective insulating member),
40 exterior members,
45 electrode tabs,
50 battery module,
60 battery packs,
70 vehicle.

Claims (13)

A plurality of electrodes laminated via a separator in an electrolyte solution;
An electrochemical cell comprising: a reference electrode that is electrically insulated from the plurality of electrodes and disposed in a projection plane of the electrodes in the stacking direction of the electrodes.   2. The electrochemical cell according to claim 1, further comprising an insulating member disposed between the electrode facing the reference electrode and the reference electrode, and electrically insulating the electrode and the reference electrode. . An exterior member that accommodates the plurality of electrodes;
The electrochemical cell according to claim 2, wherein the reference electrode is disposed between an outermost layer electrode in the stacking direction of the plurality of electrodes and the exterior member.   The electrochemical cell according to claim 1, wherein the reference electrode is disposed inside the separator.   The electrochemical cell according to any one of claims 1 to 4, wherein the shape of the reference electrode is a circle, an ellipse, or a polygon whose corners are arcs. An electrode tab connected to an end of the electrode;
In the projection plane of the electrode, the reference pole is in a region in the circumference centered at the center position of the electrode and having a radius that is half the distance from the center position of the electrode to the electrode tab. The electrochemical cell according to claim 1, wherein the electrochemical cell is arranged.   The electrochemical cell according to claim 6, wherein the reference electrode is disposed at a central portion of a projection surface of the electrode. A protective insulating member disposed between the exterior member and the reference electrode;
The electrochemical cell according to claim 3, wherein the reference electrode is disposed between the insulating member and the protective insulating member.   The electrochemical cell according to claim 2, wherein the insulating member disposed between the reference electrode and the electrode has a thickness of 1 mm or less. At least one of the plurality of electrodes includes lithium as an electrode active material,
The electrochemical cell according to claim 2, wherein the insulating member is made of an insulating material that is stable against lithium.   The electrochemical cell according to claim 2, wherein the insulating member is made of a porous material having a porosity of 20% or more.   An assembled battery comprising a plurality of secondary batteries made of the electrochemical cell according to claim 1 connected in series, in parallel, or a combination of series and parallel.   A vehicle comprising the secondary battery comprising the electrochemical cell according to any one of claims 1 to 11 or the assembled battery according to claim 12 as a driving power source.

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