JP2010161001A - Electrochemical cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical cell capable of simultaneously separating simply and accurately inner resistances such as a battery and a capacitor or the like into each of resistances of a cathode, an anode and an electrolyte solution (separator). <P>SOLUTION: The electrochemical cell comprises a cathode, an anode and at least two reference electrodes, and at least one reference electrode is a positive reference electrode arranged near on a positive electrode surface, and at least one reference electrode is a negative reference electrode arranged near on a negative electrode surface, and the width (W) of the reference electrode is 0.15 mm or less, and the distance (d1) between the cathode and the positive reference electrode arranged on the positive electrode surface and the distance (d2) between the anode and the negative reference electrode arranged on the negative electrode surface are W or more. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrochemical cell that can easily and accurately simultaneously separate internal resistances of batteries, capacitors, and the like into resistances of a positive electrode, a negative electrode, and an electrolyte (separator).

  In recent years, development of lithium-ion batteries, lithium-ion capacitors, electric double layer capacitors, etc., which are state-of-the-art power storage devices, has been accelerated toward high-current load applications such as hybrid electric vehicles and instantaneous power failure backups. In this development, the input / output characteristics of power storage devices are the most important characteristics, and rapid and useful input / output characteristics evaluation and analysis methods are required. Conventionally, input / output characteristics have been evaluated by analyzing and calculating a charge curve or discharge curve obtained by applying a plurality of charging currents (inputs) or discharging currents (outputs) to an electricity storage device. It was a laborious work. As an evaluation method that directly correlates input / output characteristics and internal resistance, Yada applied the DC internal resistance measurement method (current pause method) that measures the time dependence of internal resistance from the voltage change when DC current application was paused. (Non-Patent Document 1). In this Non-Patent Document 1, the resistance calculated from the voltage change from immediately after the pause to 1 second is the “ohm component” of the pause method resistance, and the resistance calculated from the voltage change after the second is the “balance component” of the pause method resistance. It is defined as According to this current pause method, it is possible to predict the actual input / output characteristics using the time change of the DC internal resistance (pause method resistance) obtained by this method (Non-Patent Documents 2 and 3). As described above, the direct current internal resistance (resting method resistance) is closely related to the actual input / output characteristics, and the evaluation / analysis thereof has become very important particularly in a high-power storage device.

  On the other hand, the internal resistance of the electricity storage device includes an internal resistance due to the positive electrode (positive electrode resistance), an internal resistance due to the negative electrode (negative electrode resistance), and an internal resistance due to the separator containing the electrolytic solution (separator resistance). . Each resistor is a basic element that determines the input / output characteristics of the electricity storage device. Conventionally, in the analysis of these resistances, the positive electrode, the negative electrode, and the separator are individually analyzed, and the respective resistances in the device are estimated from this analysis information. This separates the internal resistance, especially the DC internal resistance (quiescent resistance), which is directly related to the input / output characteristics, within the device and at the same time evaluates each resistance (positive resistance, negative resistance, separator resistance). This is due to difficulties. In response to this problem, Yada proposed and reported a separation method using a quadrupole cell in Non-Patent Document 1. In addition to the positive electrode and the negative electrode, the structure of this quadrupole cell has two reference electrodes, a positive reference electrode disposed near the positive electrode and a negative reference electrode disposed near the negative electrode. If this quadrupole cell is used, the positive electrode resistance, the negative electrode resistance, and the separator resistance can be separated at the same time. The associated quiescent resistance of the entire device can be separated into positive quiescent resistance, negative quiescent resistance, and separator quiescent resistance, allowing more detailed resistance analysis (input / output characteristic analysis). .

  With respect to this quadrupole cell, Patent Document 1 has a positive electrode, a negative electrode, and at least two reference electrodes, wherein at least one reference electrode is located in the vicinity of the positive electrode and at least one other reference electrode is located in the vicinity of the negative electrode. The distance (D) between the positive electrode and the negative electrode is 1 mm or less, the distance between the reference electrode and the positive electrode located in the vicinity of the positive electrode, and the reference electrode and the negative electrode located in the vicinity of the negative electrode. An electrochemical cell in which at least one of the distances is D or less is disclosed. In the specific example disclosed in Patent Document 1, the surface of the reference electrode located near the positive electrode is inside the positive electrode surface, and the surface of the reference electrode located near the negative electrode is inside the negative electrode surface. However, when this cell is actually assembled, positioning of the reference electrode (position relationship / distance between the positive electrode and the reference electrode located near the positive electrode, or position relationship / distance between the negative electrode and the reference electrode located near the negative electrode ) Is difficult, the positioning of the reference electrode is easy, and an electrochemical cell capable of accurately separating the resistance is required.

JP-A-2005-19116

Shigekuni Yada, “Practical evaluation technology for lithium-ion batteries and capacitors”, Technical Information Association (September 2006) Yada Shizukuni, Mori Goro, Satake Hisashi, 48th Battery Discussion Meeting Proceedings: 3C-09 (2007) S. Yata, S .; Mori and H.M. Satake, ECS Transactions, 16 (1), 13 (2008)

  As described above, using an electric cell having a positive electrode, a negative electrode, and at least two reference electrodes, wherein at least one reference electrode is located in the vicinity of the positive electrode and at least one other reference electrode is located in the vicinity of the negative electrode. A method is known in which the internal resistance of the electricity storage device is simultaneously separated in the device and each resistance (positive electrode resistance, negative electrode resistance, separator resistance) is evaluated. A quadrupole cell having a positive electrode, a negative electrode, and at least one positive reference electrode and at least one negative reference electrode, the positive reference electrode being disposed in the vicinity on the positive electrode surface, and the negative reference electrode being disposed in the vicinity on the negative electrode surface This structure is disclosed in Non-Patent Document 1. As described above, when the positive reference electrode is disposed in the vicinity of the positive electrode surface and the negative reference electrode is disposed in the vicinity of the negative electrode surface, the positive electrode resistance, the negative electrode resistance, and the separator resistance can be separately evaluated in the device. Although positioning of the reference electrode is facilitated, there are problems in measurement accuracy and separation accuracy of each resistor. An object of the present invention is to provide an electrochemical cell capable of easily and accurately separating internal resistances of a battery, a capacitor and the like from positive and negative electrodes and an electrolyte (separator).

  As a result of conducting research while paying attention to the problems of the prior art as described above, the present inventor has a positive electrode, a negative electrode, and at least two reference electrodes, and at least one reference electrode is located near the positive electrode surface. In an electrochemical cell that is a positive reference electrode that is disposed and at least one reference electrode is a negative reference electrode disposed in the vicinity on the negative electrode surface, when the shape and position of the reference electrode are within specific conditions The present inventors have found that internal resistances of batteries, capacitors, etc. can be easily and accurately separated into positive, negative, and electrolytic solution (separator) resistances at the same time.

  That is, the present invention is characterized by having the following configuration and solves the above problems.

(1) An electrochemical cell having a positive electrode, a negative electrode, and at least two reference electrodes, wherein at least one reference electrode is a positive reference electrode disposed in the vicinity on the positive electrode surface, and at least one reference electrode is , A negative reference electrode disposed in the vicinity of the negative electrode surface, the width (W) of the reference electrode being 0.15 mm or less, a distance (d1) between the positive electrode and the positive reference electrode disposed on the positive electrode surface, and An electrochemical cell, wherein a distance (d2) between the negative electrode and the negative reference electrode disposed on the negative electrode surface is W or more.
With this configuration, the internal resistance of a battery, a capacitor, or the like can be easily and accurately simultaneously separated into each resistance of the positive electrode, the negative electrode, and the electrolytic solution (separator). The vicinity on the positive electrode surface or the negative electrode surface is an arbitrary position between the positive electrode and the negative electrode, and some or all of the positive reference electrode and the negative reference electrode are on the positive electrode surface and the negative electrode surface, respectively. That means. The d1 and d2 are the shortest distance between the positive electrode surface (the separator-side electrode surface) and the positive reference electrode, and the shortest distance between the negative electrode surface (the separator-side electrode surface) and the negative reference electrode.
The width (W) of the reference electrode may be not less than a width that allows the reference electrode to be manufactured and not more than 0.15 mm. However, if the resistance to be measured is small, the width (W) of the reference electrode is reduced. As a result, the internal resistance can be measured with higher accuracy. That is, the width (W) of the reference electrode is preferably not less than the width that allows the reference electrode to be manufactured and not more than 0.1 mm, and more preferably not more than 0.08 mm.

(2) In the electrochemical cell, the thickness (H) of the reference electrode is 0.15 mm or less.
If the thickness (H) of the reference electrode can also be manufactured, it is preferable that it is as thin as possible. According to the configuration of (2), it is possible to further improve the separation accuracy of the resistance of the electrolytic solution (separator).

(3) The electrochemical cell characterized in that in the electrochemical cell, all of the positive reference electrode and the negative reference electrode are arranged on the inner side of the electrode end face of the positive electrode or the negative electrode.
According to the configuration of (3), in particular, it is possible to further improve the measurement accuracy of the “ohm component” in the pause method resistance described in Non-Patent Document 1.

(4) The electrochemical cell characterized in that the reference electrode has a length (L) of 5 mm or less in the electrochemical cell.
As long as the length (L) of the reference electrode can be manufactured, it is preferable that the length is as short as possible. According to the configuration of (4), in particular, it is possible to further improve the measurement accuracy of the “equilibrium component” in the pause method resistance described in Non-Patent Document 1.

(5) The electrochemical cell, wherein the positive reference electrode and / or the negative reference electrode is obtained by electrochemically depositing a reference electrode material on a conductive substrate.
According to the configuration of (5), it is possible to easily manufacture a reference electrode having a fine size.

  The electrochemical cell of the present invention has an effect that the internal resistance of a battery, a capacitor or the like can be easily and accurately simultaneously separated into each resistance of a positive electrode, a negative electrode, and an electrolyte (separator).

An example of the structure of the electrochemical cell of this invention is shown. 2 shows a cross-sectional structure of the electrochemical cell shown in FIG. An example of the position of the positive reference pole of this invention and a negative reference pole is shown. FIG. 3 shows an example of the positions of the positive reference electrode and the negative reference electrode when the parts A and B are viewed from the arrow direction. 4A is an explanatory view of the positive electrode side A portion and FIG. 4B is an explanatory view of the negative electrode side B portion viewed from the direction of the arrow. The distance (d1) between the positive electrode and the positive reference electrode disposed on the positive electrode surface and the distance (d2) between the negative electrode and the negative reference electrode disposed on the negative electrode surface will be described. It is a figure explaining the dimension of a positive reference pole and a negative reference pole. It is a figure which shows the measurement result of this invention Example 1. FIG. It is a figure which shows the measurement result of B point of this invention Example 1. FIG.

  An embodiment of the present invention will be described as follows. The electrochemical cell of the present invention is an electrochemical cell having a positive electrode, a negative electrode, and at least two reference electrodes, and at least one reference electrode is a positive reference electrode disposed in the vicinity on the positive electrode surface, and at least One reference electrode is a negative reference electrode disposed in the vicinity on the negative electrode surface, and the width (W) of the reference electrode is 0.15 mm or less, and the positive reference electrode is disposed in the vicinity on the positive electrode and the positive electrode surface. (D1) and the distance (d2) between the negative electrode and the negative reference electrode disposed in the vicinity on the negative electrode surface are W or more. FIG. 1 shows an example of the structure of the electrochemical cell of the present invention, and FIG. 2 shows the cross-sectional structure of the electrochemical cell shown in FIG. The electrochemical cell of the present invention is disposed between a positive electrode made of a positive electrode layer 1 formed on a positive electrode current collector 1 ′, a negative electrode made of a negative electrode layer 2 formed on a negative electrode current collector 2 ′, a positive electrode, and a negative electrode. Separator 5, positive reference electrode 3 disposed near the positive electrode surface, lead 3 ′ for extracting the potential of the positive reference electrode, negative reference electrode 4 disposed near the negative electrode surface, and potential of the negative reference electrode It is comprised from the lead 4 'for taking out. The separator 5 is impregnated with an electrolytic solution. The vicinity on the positive electrode surface or the negative electrode surface is an arbitrary position between the positive electrode and the negative electrode, and the positive reference electrode arranged in the vicinity on the positive electrode surface is at a distance (d1) from the positive electrode and in the vicinity on the negative electrode surface. The arranged negative reference electrode is arranged at a distance (d2) from the negative electrode. At least one of the positive reference electrode 3 and the negative reference electrode 4 is required, and a plurality of positive reference electrodes 3 and a plurality of negative reference electrodes 4 may be used. These constituent materials are put in a case 11 made of plastic material, aluminum laminate material, metal material or the like to form a sealed electrochemical cell, or an open-type electrochemical cell is immersed in a container filled with an electrolytic solution. For example, the cell shape can be arbitrarily selected.

  In FIG. 1, the positive electrode current collector 1 ′ and the negative electrode current collector 2 ′ are provided with a portion where no electrode layer is formed and this portion is used as an external terminal. The current collection structure can be selected arbitrarily, such as welding the external terminal separately to the current collector 2 ', and bonding and pressure-contacting the positive electrode current collector 1' and the negative electrode current collector 2 'to the metal exterior that also serves as the cell case. Is possible. Similarly, the lead 3 ′ for extracting the potential of the positive reference electrode and the lead 4 ′ for extracting the potential of the negative reference electrode are also separately integrated with the positive reference electrode 3 and the negative reference electrode 4. It is possible to configure by any method such as connection.

  The positive reference electrode 3 and the negative reference electrode 4 can be used by appropriately selecting a material that generates a potential in the electrochemical system (electrolytic solution system) to be measured. For example, the positive reference electrode 3 and the negative reference electrode 4 are organic electrolytic systems containing lithium salts. If it exists, lithium metal, a lithium alloy, etc. can be used. The positive reference electrode 3 and the negative reference electrode 4 in the present invention refer to a portion where a material that can be a reference electrode is in contact with an electrolyte solution (electrolyte). Hereinafter, the case where lithium metal is used as the positive reference electrode 3 and the negative reference electrode 4 will be specifically described as an example. However, the material of the reference electrode of the present invention is not limited to only lithium metal. When the material of the reference electrode is lithium metal, the positive reference electrode 3 and the negative reference electrode 4 are, for example, metal wires in which lithium metal having a predetermined dimension is crimped to the tip of a metal wire such as platinum, nickel, copper, iron, stainless steel, etc. It is possible to manufacture by a method such as attaching lithium metal to a partial surface of the metal wire, electrodepositing lithium metal on a partial surface of the metal wire, or coating lithium metal on a partial surface of the metal wire. In these cases, the positive reference electrode 3 and the negative reference electrode 4 indicate portions where lithium metal is present, and the portions where lithium metal is not present are the lead 3 ′ and the lead 4 ′. In the present invention, the dimensions of the positive reference electrode 3 and the negative reference electrode 4 are defined. For example, when the positive reference electrode 3 and the negative reference electrode 4 are manufactured by attaching lithium metal to a part of the surface of the metal wire, It is the size including the metal wire where the metal exists.

  FIG. 3 is a diagram for explaining an example of the positions of the positive reference electrode and the negative reference electrode of the present invention. FIG. 4 is a diagram of the positive reference electrode and the negative reference electrode viewed from the direction of the arrow A and B in FIG. It is drawing explaining an example of a position. A portion surrounded by a broken line Y in FIGS. 4A and 4B is a range where the positive electrode and the negative electrode exist on the back surface of the separator 5. In the present invention, the reference electrode can be easily positioned by arranging the positive reference electrode in the vicinity on the positive electrode surface and the negative reference electrode in the vicinity on the negative electrode surface. Here, although the positive reference electrode 3 and the negative reference electrode 4 are all shown on the positive electrode surface and the negative electrode surface, the positive reference electrode 3 and a part of the negative reference electrode 4 are respectively positive electrode surfaces. It may be on the negative electrode surface. The broken line X in FIGS. 3 and 4 represents the electrode end face of the positive electrode or the negative electrode, and the positive reference electrode 3 and the negative reference electrode 4 are all from the electrode end face of the positive electrode or the negative electrode as shown in FIGS. More preferably, the positive reference electrode 3 and the negative reference electrode 4 are preferably arranged so as not to be aligned on a vertical line between the positive electrode and the negative electrode. In this case, for example, as described in the background art It is possible to further increase the measurement accuracy of the “ohmic component” of the pause method resistance.

  FIG. 5 is a diagram for explaining the distance (d1) between the positive electrode and the positive reference electrode 3 disposed on the positive electrode surface and the distance (d2) between the negative electrode and the negative reference electrode 4 disposed on the negative electrode surface. d1 and d2 are the shortest distance between the positive electrode surface (electrode surface on the separator 5 side) and the positive reference electrode, and the shortest distance between the negative electrode surface (electrode surface on the separator 5 side) and the negative reference electrode. Here, d1 is equal to or greater than the width (W) of the positive reference electrode 3, d2 is equal to or greater than the width (W) of the negative reference electrode 4, preferably 2W or more, and more preferably 3W or more. Although the upper limit is not specifically limited, it is 10 W or less, and when it exceeds this, the internal resistance of the electrochemical cell increases, and resistance measurement may be difficult. In addition, when d1 and d2 are less than the width of each reference electrode, positioning becomes difficult, and each reference electrode easily inhibits the charge / discharge reaction between the positive and negative electrodes. It becomes difficult to carry out the measurement of the pause method resistance described with high accuracy.

  FIG. 6 is a diagram for explaining the dimensions of the positive reference electrode 3 and the negative reference electrode 4. In the present invention, the shapes of the positive reference electrode 3 and the negative reference electrode 4 are not particularly limited. In FIG. 6 (a), a rectangular parallelepiped is illustrated and described as a cylinder, but it is usually indefinite. Various shapes such as a substantially rectangular parallelepiped and a substantially cylindrical shape are taken. The widths (W) of the positive reference electrode and the negative reference electrode are as shown in FIG. 6, but in the case of a cylinder, W is the maximum value of the distance in the width direction of each reference electrode. In the present invention, the width (W) of the positive reference electrode and the negative reference electrode is 0.15 mm or less, preferably 0.1 mm or less, more preferably 0.08 mm or less, as long as the reference electrode can be manufactured. . The width of the reference electrode of the present invention is extremely small compared to the width (1 mm) described in Patent Document 1, but this level of width is required for placement in the vicinity on the positive electrode surface or in the vicinity on the negative electrode surface. Is required. The reason is that when the width (W) of the positive reference electrode and the negative reference electrode exceeds the upper limit, d1 and d2 must be set to be larger than W. Therefore, the internal resistance of the entire electrochemical cell is increased and resistance measurement is performed. It becomes difficult. In addition, each reference electrode is likely to inhibit the charge / discharge reaction between the positive and negative electrodes, and for example, it becomes difficult to accurately measure the quiescent resistance described in the background art. In addition, it is necessary to reduce the width (W) of the positive reference electrode and the negative reference electrode for a device having a lower resistance such as a capacitor. For example, W may be required to be 0.05 mm or less.

  The thicknesses (H) of the positive reference electrode and the negative reference electrode are as shown in FIG. 6, but in the case of a cylinder, W is the maximum value of the distance in the thickness direction of each reference electrode. In the present invention, the thickness (H) of the positive reference electrode and the negative reference electrode is not particularly limited, and can be appropriately determined depending on the distance between the positive electrode and the negative electrode, but is preferably 0.15 mm or less, and 0.1 mm or less. If the thickness (H) of the reference electrode can be manufactured, it is preferable that it is as thin as possible. When the thickness (H) of the positive reference electrode and the negative reference electrode is within this range, it is possible to further improve the separation accuracy of the resistance of the electrolytic solution (separator).

  The lengths (L) of the positive reference electrode and the negative reference electrode are as shown in FIG. 6, but W in the case of an indefinite shape is the maximum value of the distance in the length direction of each reference electrode. In the present invention, the lengths (L) of the positive reference electrode and the negative reference electrode are not particularly limited and can be appropriately determined depending on the size of the positive electrode and the negative electrode, but are preferably 5 mm or less, and more preferably 3 mm or less. Preferably, the length (L) of the reference electrode is preferably as short as possible if it can be manufactured. When the length (L) of the positive reference electrode and the negative reference electrode is in this range, for example, it is possible to further improve the measurement accuracy of the “equilibrium component” in the pause method resistance described in the background art.

  As long as the positive reference electrode and the negative reference electrode are in the above-mentioned range, there is no problem even if the dimensions and distances of d1 and d2 are different, but it is preferable to make them the same size as much as possible.

  As described above, the positive reference electrode and the negative reference electrode in the present invention may be difficult to manufacture because of their small dimensions. In such a case, the positive reference electrode and / or the negative reference electrode can be manufactured by electrochemically depositing a reference electrode material such as lithium metal on the conductive substrate. When this method is used, for example, the reference electrode width (W) is 0.08 mm or less, the reference electrode thickness (H) is 0.05 mm or less, and the reference electrode length (L) is 0.5 mm or less. A reference electrode having a simple shape can be easily manufactured. For example, a stainless steel plate having a thickness of 0.03 mm is cut into a width of 0.03 mm by fine processing such as etching, and a conductive base material is prepared which is covered with an insulating material while leaving a tip of 0.1 mm. The reference electrode manufactured by electrochemically depositing 5 μm in thickness is 0.03 mm in width (W), 0.04 mm in thickness (H), and 0.1 mm in length (L). It is a thing.

  The electrochemical cell of the present invention is not particularly limited in scope of application, but the input / output characteristics, that is, the DC internal resistance evaluation is important lithium ion battery, electric double layer capacitor, new lithium-based electricity storage device, Ni The effect is great when applied to an electricity storage device such as a hydrogen battery.

  EXAMPLES Examples will be shown below to further clarify the features of the present invention, but the present invention is not limited to the examples.

Example 1
The positive electrode was mixed with 89 parts by weight of LiCoO ₂ (average particle size 7.4 μm), 6 parts by weight of acetylene black as a conductive material, and 5 parts by weight of polyvinylidene fluoride as a binder in N-methylpyrrolidone, and applied onto an aluminum foil. The mixture layer was formed by drying and obtained by pressing. The thickness of the electrode layer was 80 μm, and the electrode density was 2.93 g / cc. The electrical conductivity of the electrode was 1.8 × 10 ⁻² S / cm. For the negative electrode, 93 parts by weight of graphitized MCMB (average particle size 25 μm), 2 parts by weight of acetylene black as a conductive material, and 5 parts by weight of polyvinylidene fluoride as a binder are mixed in N-methylpyrrolidone, and coated on copper foil and dried. This was obtained by molding and pressing the mixture layer. The thickness of the electrode layer was 80 μm, and the electrode density was 1.45 g / cc. Electrical conductivity of the electrodes was 1.5 × ¹⁰ -1 S / cm.

A quadrupole cell having the structure shown in FIG. The lithium cobaltate electrode is used as the positive electrode, the graphite electrode is used as the positive electrode, and the electrolyte solution is LiPF ₆ -3EC / 7MEC (lithium hexafluorophosphate ethylene carbonate / methyl ethyl carbonate [weight ratio 3: The separator 5 is composed of eight glass fiber nonwoven fabrics (thickness 190 μm, porosity 90%). The size of the positive electrode layer 1 and the negative electrode layer 2 is 14 mm × 20 mm. As shown in FIG. 4, the positive electrode current collector 1 ′ and the negative electrode current collector 2 ′ are provided with portions that do not form electrode layers as external terminals. Further, the positive electrode layer 1, the negative electrode layer 2, and the separator 5 are impregnated with an electrolytic solution.

  The positive reference electrode 3 and the negative reference electrode 4 have a width (W) of 0.1 mm by crimping 30 μm-thick lithium from both sides to a stainless steel wire with a wire diameter of 0.06 mm and then cutting them in the width and length directions. The thickness (H) was 0.12 mm and the length (L) was 2 mm. As shown in FIG. 2, the positive reference electrode 3 is disposed in the vicinity of the positive electrode surface, and the negative reference electrode 4 is disposed in the vicinity of the negative electrode surface via the one separator, and the positive reference electrode 3 disposed on the positive electrode and the positive electrode surface. The distance (d1) from the reference electrode and the distance (d2) from the negative electrode to the negative reference electrode arranged on the negative electrode surface are 0.19 mm. Thus, the distance (d1) between the positive electrode and the positive reference electrode and the distance (d2) between the negative electrode and the negative reference electrode can be determined more easily and accurately because the reference electrode is disposed using the separator as a spacer. All of the positive reference electrode 3 and the negative reference electrode 4 were arranged 0.1 mm inside the electrode end surfaces of the positive electrode and the negative electrode as shown in FIGS.

  The obtained electrochemical cell was measured using the current pause method described in Non-Patent Document 1. The measurement condition is a cycle in which a current of 4.5 mA is applied for 12 minutes / pause for 60 seconds. In the charging process, the cell voltage is 2 until the cell voltage (positive electrode-negative electrode voltage) reaches 4.2 V from the end of the discharge. It carried out until it reached 5V. At this time, the positive electrode-negative electrode voltage (described as P-N), the positive electrode-positive reference electrode potential (described as P-RP), and the negative electrode-negative reference electrode potential (described as N-RN) were measured. For voltage measurement, it is preferable to use a measuring instrument with an input resistance of 10 MΩ or more in order to prevent the consumption of the reference electrode. In this embodiment, an electrometer with an input resistance of 10 GΩ was used.

  The resting resistance was obtained by dividing the voltage difference immediately before resting from the voltage immediately before resting and the voltage difference after resting for 60 seconds by the applied current of 4.5 mA. Further, as described in Non-Patent Document 1, a resistance calculated from a voltage change from 0 to 1 second (referred to as an ohmic component of a pause method resistance) is calculated from a voltage change from 1 second to 60 seconds. The resistance (referred to as the equilibrium component of the quiescent resistance) was similarly calculated.

  FIG. 7 shows voltage curves of the charging process and discharging process. The discharge capacity of this cell was 7.3 mAh. In FIG. 7, there are three charge or discharge curves. The voltage curve between 2.5V and 4.2V is the voltage between the positive electrode and the negative electrode (PN), and the voltage curve near 4V above it is the potential between the positive electrode and the positive reference electrode (P-RP), 0V The voltage curve between ˜1V is the negative electrode-negative reference electrode potential (N-RN). In the figure, the portion on the corner of each curve is the rest point. Hereinafter, the present invention will be described using the result of the first discharge rest point.

  FIG. 8 shows an enlarged view of the first discharge rest point (point B in FIG. 7). The cell pause method resistance was obtained by dividing the voltage change immediately before the pause of the voltage change during the pause of PN (FIG. 8a) and the voltage difference after the 60 second pause by the applied current of 4.5 mA. The cell pause method resistance was 17.0Ω. The same applies to the resistance calculated from the voltage change from 0 to 1 second (ohmic component of the pause method resistance) and the resistance calculated from the voltage change from 1 second to 60 seconds (the equilibrium component of the pause method resistance). Calculated. The ohmic component of the quiescent resistance of the cell is 12.5Ω and the equilibrium component is 4.5Ω. According to Non-Patent Document 1, it is shown that the positive electrode pause method resistance can be separated from the voltage change during P-RP pause (FIG. 8b), and the negative electrode pause method resistance can be separated from the voltage change during N-RN pause (FIG. 8c). Has been. According to this, the calculation was made in the same manner as the cell pause method resistance, and the positive electrode pause method resistance and the negative electrode pause method resistance were calculated. The positive electrode pause method resistance was 4.2Ω, its ohmic component was 2.7Ω, the equilibrium component was 1.5Ω, the negative electrode pause method resistance was 7.7Ω, the ohmic component was 4.4Ω, and the equilibrium component was 3.3Ω.

  Further, the separator (including the electrolyte) resistance (including 6 separators in the positive reference electrode 3 and the negative reference electrode 4 in FIG. 2) is calculated from the difference between the cell pause method resistance, the separated positive electrode pause method resistance, and the negative electrode pause method resistance. Resistance). Subtracting the positive electrode pause method resistance (4.2Ω) and the negative electrode pause method resistance (7.7Ω) from the cell pause method resistance (17.0Ω) is 5.1Ω, and this is the pause method resistance for six separators. To 0.9Ω per separator (including electrolyte). In addition, each of the positive electrode pause method resistance and the negative electrode pause method resistance includes the resistance of one separator (including electrolytic solution), and therefore, by accurately subtracting one separator (including electrolytic solution) from the above value, The positive electrode resistance and the negative electrode resistance can be separated.

  Like the said Example, each resistance of a positive electrode, a negative electrode, and electrolyte solution (separator) is separable simultaneously with sufficient precision by using the electrochemical cell of this invention.

(Example 2)
A quadrupole cell was prototyped in the same manner as in Example 1 except that the reference electrode in Example 1 was changed as follows. The positive reference electrode 3 and the negative reference electrode 4 were obtained by electrochemically depositing lithium from both sides of a stainless plate having a width of 0.03 mm and a thickness of 0.03 mm in the cell. The length of the reference electrode was determined by masking with a modified polyethylene film except for the portion where lithium was electrodeposited. The positive reference electrode 3 and the negative reference electrode 4 have a width (W) of 0.03 mm, a thickness (H) of 0.04 mm, and a length (L) of 0.2 mm. As shown in FIG. 2, the positive reference electrode 3 is disposed in the vicinity of the positive electrode surface, and the negative reference electrode 4 is disposed in the vicinity of the negative electrode surface via the one separator, and the positive reference electrode 3 disposed on the positive electrode and the positive electrode surface. The distance (d1) from the reference electrode and the distance (d2) from the negative electrode to the negative reference electrode arranged on the negative electrode surface are 0.19 mm. As shown in FIGS. 4 and 5, the positive reference electrode 3 and the negative reference electrode 4 were all arranged 0.1 mm inside from the electrode end surfaces of the positive electrode and the negative electrode.

  The resistance was evaluated by the current pause method as in Example 1. The cell pause method resistance is 17.3Ω, the ohmic component of the cell pause method resistance is 12.4Ω, the equilibrium component is 4.9Ω, the positive electrode pause method resistance is 4.4Ω, the ohmic component is 2.8Ω, and the equilibrium component is The resistance of the negative electrode resting method was 7.5Ω, the ohmic component was 4.1Ω, the equilibrium component was 3.4Ω, and the separator (including electrolyte) resistance was 0.9Ω. The same result as in Example 1 was obtained.

(Comparative Example 1)
A quadrupole cell was prototyped in the same manner as in Example 1 except that the reference electrode in Example 1 was changed as follows. The positive reference electrode 3 and the negative reference electrode 4 are bonded to a stainless steel wire having a wire diameter of 0.06 mm with a thickness of 50 μm from both sides, and then cut in the width direction and the length direction so that the width (W) is reduced to 0.0. The thickness (H) was 0.16 mm and the length (L) was 2 mm. As shown in FIG. 2, the positive reference electrode 3 is disposed in the vicinity of the positive electrode surface, and the negative reference electrode 4 is disposed in the vicinity of the negative electrode surface via the one separator, and the positive reference electrode 3 disposed on the positive electrode and the positive electrode surface. The distance (d1) from the reference electrode and the distance (d2) from the negative electrode to the negative reference electrode arranged on the negative electrode surface are 0.19 mm. All of the positive reference electrode 3 and the negative reference electrode 4 were arranged 0.1 mm inside the electrode end surfaces of the positive electrode and the negative electrode as shown in FIGS.

  The resistance was evaluated by the current pause method as in Example 1. The cell pause method resistance was 17.7Ω, the ohmic component of the cell pause method resistance was 12.9Ω, and the equilibrium component was 4.8Ω, and the same results as in Example 1 and Example 2 were obtained. However, the separated positive electrode pause method resistance is 5.1Ω, its ohmic component is 2.9Ω, the equilibrium component is 2.2Ω, the negative electrode pause method resistance is 6.7Ω, the ohmic component is 4.1Ω, and the equilibrium component is 2.6Ω. Met. Further, the resistance of the separator (including the electrolytic solution) was 1.0Ω per sheet. In particular, the separated equilibrium components were shifted from the values of Example 1 and Example 2. Thus, the width (W) of the positive reference electrode 3 and the negative reference electrode 4 is 0.15 mm or more, and the distance (d1) between the positive electrode and the positive reference electrode arranged on the positive electrode surface and the negative electrode and the negative electrode surface are arranged. When the distance (d2) from the negative reference electrode is W or less, it becomes difficult to accurately separate the resistances of the positive electrode, the negative electrode, and the electrolytic solution (separator) at the same time.

  For internal resistance of lithium-ion batteries, lithium-ion capacitors, electric double-layer capacitors, etc., which are state-of-the-art storage devices for high-current load applications such as hybrid electric vehicles and instantaneous power outages, positive electrodes, negative electrodes, electrolytes (separators) It is possible to provide an electrochemical cell capable of easily and accurately simultaneously separating the resistors. By using the electrochemical cell of the present invention, it is possible to analyze in more detail important resistances in an electricity storage device for large current loads, and at the same time, new charges based on the resistances of the positive electrode, negative electrode, and electrolyte (separator) are used. Discharge control and the like are also possible.

DESCRIPTION OF SYMBOLS 1 Positive electrode layer 1 'Positive electrode collector 2 Negative electrode layer 2' Negative electrode collector 3 Positive reference pole 3 'Positive reference pole lead 4 Negative reference pole 4' Negative reference pole lead 5 Separator (including electrolyte)
11 cases

Claims (5)

  An electrochemical cell having a positive electrode, a negative electrode and at least two reference electrodes, wherein at least one reference electrode is a positive reference electrode disposed in the vicinity on the positive electrode surface, and at least one reference electrode is a negative electrode surface A negative reference electrode disposed in the vicinity of the upper electrode, the width (W) of the reference electrode being 0.15 mm or less, a distance (d1) between the positive electrode and the positive reference electrode disposed on the positive electrode surface, and the negative electrode and the negative electrode An electrochemical cell, wherein a distance (d2) from a negative reference electrode disposed on a surface is W or more.   The electrochemical cell according to claim 1, wherein a thickness (H) of a reference electrode in the electrochemical cell is 0.15 mm or less.   3. The electrochemical cell according to claim 1, wherein all of the positive reference electrode and the negative reference electrode are disposed inside the positive or negative electrode end face in the electrochemical cell.   The electrochemical cell according to any one of claims 1 to 3, wherein a length (L) of a reference electrode in the electrochemical cell is 5 mm or less. 5. The electrochemical cell according to claim 1, wherein the positive reference electrode and / or the negative reference electrode is obtained by electrochemically depositing a reference electrode material on a conductive substrate. An electrochemical cell according to claim 1.

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