JP5002188B2 - Power storage device and power storage cell - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a power storage device and a power storage cell, and in particular, a series connection of power storage cells that perform a reversible charge / discharge process by anion storage / release at a positive electrode and lithium ion storage / release at a negative electrode in a non-aqueous electrolyte. It relates to what is used.

  In recent years, wind power generation and solar cells have attracted attention as clean energy sources with a low environmental impact. However, the power supplied from these sources is unstable depending on natural conditions such as wind and sunshine, and as such, The utility value as electric power is low.

  If this unstable electric power can be stored once and released at any time as needed, it is possible to obtain electric power with high utility value even with the same amount of energy. For this purpose, a power storage device capable of storing electric power so that it can be released at any time is required.

  As a power storage means used in such a power storage device, a lithium ion secondary battery having a high energy density and capable of being charged is provided. This lithium ion secondary battery includes a positive electrode using a composite oxide of lithium and other transition metals such as cobalt (for example, lithium cobaltate), a negative electrode capable of inserting and extracting lithium ions, and a non-aqueous solution containing a lithium salt. It is comprised using electrolyte solution, and reversible operation | movement of charging / discharging can be performed by exchange of the lithium ion between the positive electrode and negative electrode performed via electrolyte solution.

  However, the lithium ion secondary battery is rapidly deteriorated in characteristics due to repeated charge and discharge, and the number of charge and discharge cycles is limited. Moreover, the time required for charging is generally long, and it has been difficult to shorten it. That is, there was a problem in charge / discharge cycle characteristics. This is a problem that is not limited to lithium-ion secondary batteries but is also common to all secondary batteries. With this, in power storage devices that use this type of secondary battery, check the secondary battery that is the storage means. There was a problem that the maintenance burden such as replacement was heavy.

  For example, in a system for storing power generation energy such as wind power generation or a solar battery, an electric double layer capacitor is more suitable than the secondary battery. Electric double layer capacitors have good charge / discharge cycle characteristics and require little maintenance. However, the electric double layer capacitor can have a very large capacity (capacitance) as a capacitor, but the chargeable / dischargeable capacity is considerably inferior to that of the lithium ion secondary battery.

  Therefore, an energy storage cell has been proposed that has characteristics such as a compromise between an electric double layer capacitor and a lithium ion secondary battery. This power storage cell is configured using a positive electrode capable of occluding and releasing anions, a negative electrode capable of occluding and releasing lithium ions, and a non-aqueous electrolyte containing a lithium salt (see Patent Documents 1 and 2). .

  In the lithium ion secondary battery, a composite oxide containing lithium is used for the positive electrode, and charge / discharge reversible operation is performed by exchanging lithium ions between the positive electrode and the negative electrode through a non-aqueous electrolyte. On the other hand, the storage cell performs a reversible operation of charge and discharge by occlusion / release of anions at the positive electrode and occlusion / release of lithium ions at the negative electrode.

  This power storage cell has such a property that the lithium ion secondary battery and the electric double layer capacitor have the advantages of each. That is, the charge / discharge cycle characteristics are superior to each stage as compared with the lithium ion secondary battery, and the charge / discharge capacity (capacity capable of being charged / discharged) is greater than each stage of the electric double layer capacitor.

Of course, this storage cell can be suitably used as a high-performance capacitor-type secondary battery. However, for example, if it is used as a storage means of the above-mentioned storage device, it is almost maintenance-free along with downsizing and high performance of the device. The power storage device can be realized.
JP-A-2005-19762 JP2002-305034

The storage cell is often used in a state where a plurality of cells are connected in series, that is, a so-called collective cell, as in the case of a conventional lithium ion secondary battery, but charging is performed by connecting a plurality of storage cells in series. In this case, it is necessary that the charging voltage is evenly distributed between the positive electrode and the negative electrode of each cell. When this voltage distribution balance is lost, a specific high voltage is applied between the positive electrode and the negative electrode of a specific cell, a gas generation reaction occurs, and the cell is destroyed.
Therefore, as shown in FIG. 7, it has been conventionally studied to connect in parallel a constant voltage control circuit 59 that controls the voltage between the positive electrode 21 and the negative electrode 23 to a predetermined value or less in each of the plurality of storage cells 101 connected in series. It was done.

  FIG. 7 shows a power storage device in which two power storage cells 101 are connected in series. A charging voltage from the charging power supply 60 is applied in series to each cell 101 of the power storage device. Each power storage cell 101 has an electrode body 20 in which a positive electrode 21 and a negative electrode 23 are opposed to each other with a separator 22 interposed therebetween, and the electrode body 20 is accommodated in a sealed cell container 11 together with a nonaqueous electrolytic solution 24 containing a lithium salt. Has been.

  The positive electrode 21 is formed by forming a positive electrode material capable of occluding and releasing anions on a current collector, and the current collector is connected to a positive electrode terminal 31. The negative electrode 23 is formed by forming a negative electrode material capable of occluding and releasing lithium ions on a current collector, and the current collector is connected to a negative electrode terminal 33.

  The constant voltage control circuit 59 is a voltage control circuit of a parallel control system called a so-called shunt regulator. When the cell voltage appearing between the positive terminal 31 and the negative terminal 33 exceeds a predetermined value, a shunt current (parallel current) is generated. To suppress the cell voltage to a predetermined value. This constant voltage control circuit 59 is provided for each storage cell 101.

  However, the present inventors have clarified that the conventional power storage cell 101 including the constant voltage control circuit 59 has the following problems.

  That is, when a charging voltage is applied between the positive electrode and the negative electrode of the storage cell, each potential of the positive electrode and the negative electrode reaches a predetermined potential assumed in the design of the storage cell. After that, when the voltage is continuously applied, the potential changes according to the magnitudes of the leakage currents at the positive electrode and the negative electrode, and finally the equilibrium state is reached at the point where the leakage currents at the positive and negative electrodes become equal.

  When the ambient temperature is low or room temperature, in the above equilibrium state, each potential of the positive and negative electrodes settles in the vicinity of a predetermined potential that is assumed in advance, but when the ambient temperature becomes high, the leakage current at the negative electrode becomes negative. Beyond that, the potentials of both poles gradually shift to the noble side. As a result, the potential of the positive electrode reaches a potential that causes a gas generation reaction, thereby increasing the internal pressure of the cell and eventually causing a problem that the cell is destroyed. This problem is more likely to occur as the number of cells connected in series increases.

  When both the positive and negative potentials rise, the potential rise is not reflected in the potential difference between the positive and negative electrodes, that is, the cell voltage appearing between the positive electrode 21 and the negative electrode 23. Therefore, as shown in FIG. 7, even if the cell voltage appearing between the positive electrode 21 and the negative electrode 23 is controlled, the problem cannot be solved.

  The present invention has been made in view of the above-described problems, and its purpose is to charge and discharge by storing and releasing anions at the positive electrode and storing and releasing lithium ions at the negative electrode in the non-aqueous electrolyte. In a power storage device using a plurality of power storage cells connected in series and performing a reversible process, and the power storage cell, it is easy and reliable that a positive electrode potential becomes high and a gas generation reaction occurs when charging the serial cell. It is to suppress and increase the reliability of a power storage device using a series cell.

  Other objects and configurations of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  The present invention provides the following solutions.

  (1) An electricity storage cell in which an electrode body in which a positive electrode capable of occluding and releasing anions and a negative electrode capable of occluding and releasing lithium ions are opposed to each other via a separator is housed in a sealed container together with a non-aqueous electrolyte. Are connected in series, and each cell has a third electrode having lithium metal disposed in the non-aqueous electrolyte, and the potential difference between the third electrode and the positive electrode is greater than or equal to a predetermined value. The electrical storage device is characterized in that the potential of the positive electrode is controlled with respect to the third electrode by conducting a conductive connection between the third electrode and the positive electrode.

  (2) In the means (1), when the potential difference between the third electrode and the positive electrode exceeds a predetermined value, the operation of conducting the conductive connection between the third electrode and the positive electrode is performed only when the cell is charged. A power storage device characterized by being configured as described above.

  (3) The power storage device according to (1) or (2), wherein the operation is performed only when a charging current of the cell is a predetermined value or less.

  (4) A power storage cell used in the power storage device of the means (1) to (3), wherein when the potential difference between the third electrode and the positive electrode is equal to or greater than a predetermined value, A storage cell comprising circuit means for conducting and connecting the positive electrodes.

  (5) In the means (4), as the circuit means, voltage detecting means for monitoring a potential difference between the third electrode and the positive electrode, and when the voltage detecting means detects a potential difference of a predetermined value or more, the circuit means is turned on. And a switch means for electrically connecting the positive electrode and the third electrode.

  (6) A storage cell characterized in that, in the means (4), a constant voltage element having a predetermined voltage threshold is used as the circuit means.

  (7) The electricity storage cell according to any one of the means (4) to (6), wherein the negative electrode uses graphite as a negative electrode material capable of inserting and extracting lithium ions.

  (8) A method of manufacturing a power storage cell used in the power storage device according to the means (4) to (7), wherein a lithium ion is preoccluded in the negative electrode by passing a current between the negative electrode and the third electrode. A method of manufacturing a storage cell, characterized by comprising:

  (9) In the electric storage cell according to (8), in order to pass a current between the negative electrode and the third electrode, the negative electrode and the third electrode are conductively connected directly or via a current limiting element. Production method.

  A power storage device using a plurality of power storage cells connected in series and performing a reversible charging / discharging process by occlusion / release of anions at a positive electrode and occlusion / release of lithium ions at a negative electrode in a non-aqueous electrolyte and the power storage cell Therefore, it is possible to easily and reliably suppress the occurrence of a gas generation reaction due to the positive electrode potential being increased when the series cell is charged, thereby improving the reliability of the power storage device using the series cell. Can do.

  Operations / effects other than those described above will be apparent from the description of the present specification and the accompanying drawings.

  FIG. 1 shows an embodiment of a power storage cell 10 used in a power storage device according to the present invention. In the figure, (a) is a broken front view, and (b) is a cross-sectional view taken along line AA of (a).

  In the electricity storage cell 10 shown in the figure, an electrode body 20 in which a positive electrode 21 and a negative electrode 23 are opposed to each other via a separator 22 is housed in a sealed cell container 11 together with a nonaqueous electrolyte solution 24. At the same time, the third electrode 25 having the lithium metal 41 is disposed in the non-aqueous electrolyte 24.

  The positive electrode 21 is formed by laminating a positive electrode material 211 using a carbon material capable of occluding and releasing anions on both surfaces of a sheet-like current collector 212 made of a metal foil (Al) by coating or the like, and the whole is a sheet. It is formed in a shape. Similarly, the negative electrode 23 has a negative electrode material 231 capable of occluding and releasing lithium ions attached to both surfaces of a sheet-like current collector 232 made of a metal foil (Cu) by coating or the like, and the whole is formed into a sheet shape. Is formed. The positive electrode 21 and the negative electrode 23 are sequentially stacked while sandwiching the separator 22 to form a rectangular flat stacked electrode body 20.

  The current collectors 212 and 232 are integrally formed with lead-like tabs 213 and 233 for connecting to external terminals, respectively. The tabs 213 of the positive electrode current collector 212 are commonly connected to each other and connected to the positive electrode terminal 31. Similarly, the tabs 233 of the negative electrode current collector 232 are commonly connected to each other and connected to the negative electrode terminal 33. Each of the positive electrode terminal 31 and the negative electrode terminal 33 is installed across the inside and outside of the cell container 11 while maintaining the sealed state of the cell container 11.

  The positive electrode 21 occludes anions in the electrolyte during charging and releases them during discharging. The negative electrode 23 occludes lithium ions (cations) in the electrolyte during charging and releases it during discharging. A reversible charging / discharging process is performed by reversible occlusion / release of these anions and lithium ions.

  As the material of the positive electrode material 211 and the negative electrode material 231, a carbon material is suitable. In particular, the positive electrode material 211 is preferably a graphite material, and the negative electrode material 231 is preferably a non-graphitizable carbonaceous material.

  The third electrode 25 is obtained by attaching lithium metal 41 to one side of a metal foil (or a metal thin plate), and is installed so that the lithium metal 41 faces the side end surface of the laminated electrode body 20 in parallel. ing. The third electrode 25 is connected to a third electrode terminal 35 installed across the inside and outside of the cell container 11 while keeping the cell container 11 sealed.

  The cell container 11 is not particularly limited as long as it can stably and hermetically contain the cell components including the non-aqueous electrolyte 24. In this embodiment, the cell container 11 is rectangular by airtight flexible packaging material such as a laminate film. Soft containers processed into bags are used.

  A voltage control energization circuit 51 is connected between the positive electrode terminal 31 and the third electrode terminal 35. The voltage control energization circuit 51 is configured to electrically connect the third electrode 25 and the positive electrode 21 when the potential difference between the third electrode 25 and the positive electrode 21 becomes a predetermined value or more.

  FIG. 2 shows an embodiment of the voltage control energization circuit 51. The voltage control energization circuit 51 shown in the figure includes a voltage detector 511, a transistor Q1 as a switching element, resistors R1 to R3, and the like, and a voltage Vab applied between the control terminals a and b is formed by resistors R1 and R2. The voltage is divided and input to the voltage detector 511.

  The voltage detector 511 compares the input voltage (potential difference) with a predetermined reference voltage Vr1, and turns on the transistor Q1 when the input voltage exceeds the reference voltage Vr1. The transistor Q1 is connected in parallel to the control terminals a and b via the resistor R3. Therefore, when the voltage Vab between the control terminals a and b exceeds a predetermined voltage set by the resistors R1 and R2 and the reference voltage Vr1, the control terminals a and b are conductively connected via the transistor Q1 and the resistor R3. The

  The voltage control energization circuit 51 is individually provided in each storage cell 10, and one of the control terminals a and b is connected to the positive electrode terminal 31 and the other b is connected to the third electrode terminal 25.

  The voltage control energization circuit 51 can also be configured using a two-terminal type constant voltage element having a predetermined voltage threshold value. Examples of the constant voltage element include a Zener diode, a diode connected in series so that the forward voltage becomes a predetermined threshold voltage, and a two-terminal voltage switch using a MOS or bipolar transistor. If these constant voltage elements are used, a circuit function corresponding to the voltage control energization circuit 51 can be provided very simply and at low cost.

  On the other hand, like the voltage control energization circuit 51 shown in FIG. 2, the voltage detection means for monitoring the potential difference, and when the voltage detection means detects a potential difference of a predetermined value or more, it is turned on and the positive electrode 21 and the third If an active circuit system including a switch means for conductively connecting the electrodes 25 is used, there is an advantage that it is easy to perform control for performing energization control between the positive electrode 21 and the third electrode 25 under optimum conditions, as will be described later. It is done. Therefore, in this embodiment, an active voltage control energization circuit 51 as shown in FIG. 2 is used.

  The operating power supply of the voltage control energization circuit 51 uses the voltage appearing between the positive electrode terminal 31 and the third electrode terminal 35, but the current necessary for the operation is so small that it can be ignored.

  FIG. 3 is a circuit diagram schematically showing the outline of the first embodiment of the power storage device according to the present invention. The power storage device shown in the figure is configured using the power storage cell 10 shown in FIG. 1 and the voltage control energization circuit 51 shown in FIG.

  A plurality (two in the illustrated example) of storage cells 10 are connected in series and connected to the charging power source 60. Each storage cell 10 is provided with the voltage control energization circuit 51 externally. For each cell 10, the control terminals a and b of the voltage control energization circuit 51 are connected to the positive electrode terminal 31 and the third electrode terminal 35. Thus, for each cell 10, when the potential difference between the third electrode 25 and the positive electrode 21 becomes equal to or greater than a predetermined value, the third electrode 25 and the positive electrode 21 are conductively connected.

  In FIG. 3, when a charging voltage is applied from the charging power supply 60 to the storage cells 10 connected in series, the charging current Ic is supplied to each cell 10 and charging is performed. At the time of this charging, the anion in the nonaqueous electrolytic solution 24 is occluded in the positive electrode 21, and the lithium ion in the nonaqueous electrolytic solution 24 is occluded in the negative electrode 23. At the time of discharge, on the contrary, the anions occluded in the positive electrode 21 are released into the non-aqueous electrolyte 24 and the lithium ions occluded in the negative electrode 23 are released into the non-aqueous electrolyte 24. .

  Here, when the potential of the positive electrode 21 shifts to a high potential due to an increase in the ambient temperature or when the voltage balance of each cell collapses for some reason, the potential of the positive electrode 21 causes a gas generation reaction. The potential may be reached.

In that case, a voltage (potential difference) appearing between the positive electrode 21 and the third electrode 25 is detected, and the third electrode 25 and the positive electrode 21 are conductively connected when the voltage exceeds a predetermined value. At this time, the potential of the third electrode 25 is kept at a constant lithium potential in the non-aqueous electrolyte 24. Therefore, the voltage control energization circuit 51 accurately monitors the behavior of the positive electrode potential regardless of the behavior of the negative electrode potential, and conducts the positive electrode 21 and the third electrode 25 when the positive electrode potential exceeds a predetermined value. Can be connected.

  When the positive electrode 21 and the third electrode 25 are conductively connected, the anion is released into the non-aqueous electrolyte 24 at the positive electrode 21, and a part of the lithium metal 41 becomes an ion at the third electrode 25. Dissolve in 24. On the other hand, during charging in which a voltage is applied between the positive electrode 21 and the negative electrode 23 from the outside, the positive electrode 21 stores anions and the negative electrode 23 stores lithium ions. As a result, when the positive electrode 21 and the third electrode 25 are conductively connected, the positive electrode 21 apparently does not perform anion occlusion / release reaction, and only the negative electrode 23 side generates lithium metal 41 dissolved. I will occlude ions. When the negative electrode 23 occludes lithium ions, the negative electrode potential shifts toward a certain lithium potential. Thereby, even if the leakage current in the negative electrode 23 increases by applying the charging voltage at a high temperature, the positive electrode 21 can be prevented from becoming a predetermined potential or higher.

  That is, in each cell 10, the high potential shift of the positive electrode potential with respect to the lithium metal 41 can be balance-corrected. Therefore, if the voltage (predetermined value) at which the voltage control energization circuit 51 operates is set lower than the potential at which the gas generation reaction occurs, the gas generation reaction due to the increase in the positive electrode potential can be reliably suppressed and the cell can be destroyed Can be prevented.

  Although the fatal problem of cell destruction is solved by the above configuration, the voltage appearing between the positive and negative electrodes of each cell 10 during charging varies spontaneously depending on the behavior of the negative electrode potential even if the positive electrode potential is stabilized. There are things to do. On the other hand, when a plurality of cells 10 are connected in series and a charging voltage is applied, it is desirable that the voltages appearing between the positive and negative electrodes of each cell 10 are evenly aligned. That is, it is desirable that the charging voltage is equally distributed to each cell 10.

  This problem can be achieved by using a carbon material whose potential change with respect to the amount of occlusion (dope) of lithium ions is relatively flat as the negative electrode material 231. Further, in the manufacturing process of the cell 10, the negative electrode 23 using the carbon material is preliminarily occluded (pre-doped), so that the negative electrode potential is changed to the lithium potential in the entire operation range from the initial stage to the final stage of charging. It becomes possible to settle stably at almost the same potential. As a result, the charging voltage can be evenly distributed to each cell 10 in the entire operation range from the initial stage to the end stage of charging.

  The pre-occlusion process can be performed easily and efficiently after the storage cell 10 is completed by using the third electrode terminal 35. The pre-occlusion can be performed by flowing a current between the negative electrode 23 and the third electrode 25, but in order to flow the current, the negative electrode 23 and the third electrode 25 are simply connected as shown in FIG. All that is required is a conductive connection. In this case, the negative electrode 23 and the third electrode 25 may be directly short-circuited, but as shown in the figure, the negative electrode 23 and the third electrode 25 are connected through a resistor Ri that is a current limiting element. The current flowing between them can be optimized and set with a resistance value.

  FIG. 5 is a circuit diagram schematically showing the outline of the second embodiment of the power storage device according to the present invention. If it demonstrates paying attention to the difference with 1st Embodiment mentioned above, in this 2nd Embodiment, while providing each voltage control electricity circuit 51 in each electrical storage cell 10, the voltage control electricity circuit 51 of each cell 10 is shared. A charge detection circuit 52 to be controlled is provided.

  The charge detection circuit 52 detects the presence / absence of application of the charge voltage and the magnitude of the charge current, and controls the operation (voltage detection and conduction control operation) of the voltage control energization circuit 51 of each cell 10 based on the detection. Thereby, the voltage control energization circuit 51 of each cell 10 operates in the following control mode.

  That is, voltage detection and conduction control operations between the third electrode 25 and the positive electrode 21 are performed only when the cell 10 is charged. That is, during non-charging, the voltage detection and conduction control operations are suspended (sleep mode).

  Further, the operation is performed only when the charging current of the cell 10 is not more than a predetermined value. The positive electrode potential is likely to be increased when the charging current starts to decrease at the end of charging. Therefore, the purpose of stabilizing the positive electrode potential is achieved by performing the control operation for stabilizing the positive electrode potential only during this period.

  The consumption current of the electronic circuit such as the voltage control energization circuit 51 is very small but not zero. Therefore, the current consumption can be further reduced by performing the voltage detection and conduction control operations by the electronic circuit only when necessary as described above. In this case, the current consumption of the charge detection circuit 52 becomes a problem. Since only one charge detection circuit 52 is provided for the plurality of cells 10 connected in series, the current consumption as a whole may be reduced. it can.

  In addition, by restricting the operation of the voltage control energization circuit 51 only when necessary, it is possible to avoid unnecessary consumption of the lithium metal 41 of the third electrode 25.

  FIG. 6 is a circuit diagram showing a main part of a third embodiment of the power storage device according to the present invention. In the third embodiment, each of the storage cells 10 connected in series includes the voltage control energization circuit 51 and the charge detection circuit 52.

  In a power storage device, the number of power storage cells 10 in series is often arbitrarily determined by a user as necessary. Moreover, the said electrical storage cell 10 may be used instead of the conventional secondary battery. Assuming such usage, if the voltage control energization circuit 51 and the charge detection circuit 52 are provided independently for each storage cell 10 so that they can be handled as one cell, the user can Series connection wiring on the side can be simplified, and compatibility with a conventional secondary battery can be ensured.

  In FIG. 6, the charge detection circuit 52 includes a first current detection circuit 521 that detects the presence or absence of a charge current Ic that is greater than or equal to zero, and whether or not the charge current Ic is equal to or less than a predetermined value set by the reference voltage Vr2. Whether or not charging current Ic is greater than or equal to zero and less than or equal to a predetermined value based on the outputs of second current detection circuit 522 and level determination unit 523 to be detected, and first current detection circuit 521 and level determination unit 523 is determined. A logic unit 524 for determination is included. The determination output signal of the logic unit 524 is used as a control signal for turning on / off the operation of the voltage control energization circuit 51.

  The voltage control energization circuit 51 is the same as that shown in FIG. 2, but a transistor Q2 is added as a switch element for receiving on / off operation control by the determination output signal.

  Due to the two circuits 51 and 52, each cell 10 is charged between the positive electrode 21 and the third electrode 25 only when the charging current Ic is zero or more and the charging current Ic is not more than a predetermined value. The voltage detection and conduction control operations are performed.

  In the embodiment shown in FIG. 6, the two circuits 51 and 52 are provided for each cell 10. Of the two circuits 51 and 52, the charge detection circuit 52 has a plurality connected in series. Can be shared among other cells 10. In this case, only one charge detection circuit 52 needs to be provided in the entire circuit regardless of the number of cells, and the operation of the voltage control energization circuit 51 of each cell 10 is emitted from the one charge detection circuit 52. They are simultaneously turned on / off by a control signal.

  Also in this case, in each cell 10, voltage detection and conduction control between the positive electrode 21 and the third electrode 25 are performed only when the charging current Ic is zero or more and the charging current Ic is equal to or less than a predetermined value. Although the operation is performed, since there is only one charge detection circuit 52, it is possible to reduce power consumption as a whole.

  Note that the presence / absence of charging can be detected by detecting a voltage applied between the positive terminal 31 and the negative terminal 33.

<Example 1>
Production of positive electrode: Graphite powder as a positive electrode material and carboxymethylcellulose (Daiichi Kogyo Kagaku Co., Ltd., Cellogen 4H) as a positive electrode material are mixed at a weight ratio of 97: 3, and ion-exchanged water is added thereto to form a paste. A mixture was prepared. This mixture was applied to both surfaces of a 20 μm thick aluminum foil serving as a current collector. This was dried and rolled, and then cut into a predetermined shape to produce a sheet-like positive electrode. The cut positive electrode also includes an uncoated portion that becomes a tab for connection with the positive electrode terminal.

  Production of negative electrode: A non-graphitizable carbon material (PIC manufactured by Kureha Chemical Co., Ltd.) which is a negative electrode material and a polyvinylidene fluoride resin (KF # 1100 of Kureha Chemical Co., Ltd.) which is a binder of 95: 5 It mixed by weight ratio, N-methyl-2-pyrrolidinone was added as a solvent to this, and the paste-form mixture was prepared. This mixture was applied to both sides of a 14 μm thick copper foil serving as a current collector. This was dried and rolled, and then cut into a predetermined shape to produce a sheet-like negative electrode. The cut negative electrode also includes an uncoated portion that becomes a tab for connection with the negative electrode terminal.

  Production of electrode body: The produced negative electrode and positive electrode are laminated with a polyolefin separator between them so that the uncoated part (tab) of the positive electrode and the uncoated part (tab) of the negative electrode do not overlap each other, and are rectangular A flat laminated electrode body was constructed. This electrode body was accommodated in a cell container made of an aluminum laminate film.

  Production of cell: A nickel lead having a predetermined amount of lithium metal adhered thereto is placed in the cell container. A part of this nickel lead is taken out of the container as a third electrode terminal.

  Next, the uncoated portion (tab) of the positive electrode was bundled and welded to the positive electrode terminal. Similarly, the uncoated portion (tab) of the negative electrode was bundled and welded to the negative electrode terminal. Thereafter, a non-aqueous electrolyte was poured into the container. And the opening part of the container was sealed by heat sealing | fusion in the state which made each one end side of a positive electrode terminal, a negative electrode terminal, and a 3rd electrode terminal come out of a container, respectively. The electrical storage cell of Example 1 was produced by attaching the electronic circuit (voltage control energization circuit 51) described above to this (see FIG. 1).

<Example 2>
The negative electrode and lithium metal were short-circuited for a predetermined time with respect to the cell of Example 1, and the electrical storage cell of Example 2 was produced. That is, in Example 2, the step of preoccluding lithium ions in the negative electrode was performed. The short circuit between the negative electrode and the lithium metal was performed between the third electrode terminal, which is an external terminal, and the negative electrode terminal (see FIG. 4).

<Comparative example>
For the cell of Example 1, a lithium metal, a third electrode, and an electronic circuit (a storage cell not provided with the voltage control energization circuit 51) was produced (see FIG. 7).

<Test>
The cell of Example 1 and the cell of Example 2 were each connected in series and left in a constant temperature bath at 60 ° C. with a predetermined voltage applied, and the changes in the standing time, discharge electric capacity, and voltage between positive and negative electrodes were measured. did. In the measurement of the voltage between the positive and negative electrodes, attention was paid to the difference between the positive and negative voltages appearing in two cells connected in series, that is, the variation in voltage distribution between the cells. For comparison, two conventional cells were connected in series, and a test was performed under the same conditions as in Examples 1 and 2. The results of this test are shown in Tables 1 and 2.

Table 1 shows a change state of electric capacity. The numbers in the table indicate relative values when the initial capacity of the conventional cell is 100.

  As is clear from Table 1, it was confirmed that each of Examples 1 and 2 had better capacity retention characteristics for each stage during long-term storage at high temperatures than in the conventional example.

Table 2 shows a change state of the difference between the positive and negative voltages (voltage distribution variation). The numbers in the table indicate the voltage difference (V) between two series-connected cells.

  In Table 2, in the cell of Example 1, the voltage difference between the cells and the variation in the voltage distribution between the cells appear slightly larger. This is evidence that the stabilization control of the positive electrode potential was performed. Can see. In Example 2, the variation is reduced, and this can be considered as an effect of stabilization of the negative electrode potential by pre-occlusion of lithium ions. The cell of the comparative example had a small variation, but instead, a gas generation reaction occurred and the cell leaked and was destroyed. This is because the positive electrode potential has shifted to a high potential together with the negative electrode potential.

  As mentioned above, although this invention was demonstrated based on the typical Example, this invention can have various aspects other than having mentioned above.

  A power storage device using a plurality of power storage cells connected in series and performing a reversible charging / discharging process by occlusion / release of anions at a positive electrode and occlusion / release of lithium ions at a negative electrode in a non-aqueous electrolyte and the power storage cell Therefore, it is possible to easily and reliably suppress the occurrence of a gas generation reaction due to the positive electrode potential being increased when the series cell is charged, thereby improving the reliability of the power storage device using the series cell. Can do.

It is the fracture | rupture front view and side sectional view which show embodiment of the electrical storage cell used with the electrical storage apparatus which concerns on this invention. It is a circuit diagram showing one embodiment of a voltage control energization circuit suitable for use in the present invention. 1 is a circuit diagram schematically showing an outline of a first embodiment of a power storage device according to the present invention. It is a figure which shows the process principal part of the manufacturing method of the electrical storage cell used by this invention. It is a circuit diagram which shows typically an outline of a 2nd embodiment of a power storage device concerning the present invention. It is a circuit diagram which shows the principal part of 3rd Embodiment of the electrical storage apparatus which concerns on this invention. It is a circuit diagram which shows the outline of the electrical storage apparatus using the conventional electrical storage cell typically.

Explanation of symbols

10 cell container, 20 electrode body, 21 positive electrode,
211 positive electrode material, 212 positive electrode current collector, 213 tab,
22 separator, 23 negative electrode,
231 negative electrode material, 232 negative electrode current collector, 233 tab,
24 non-aqueous electrolyte, 25 3rd electrode, 31 positive electrode terminal,
33 negative electrode terminal, 35 third electrode terminal, 41 lithium metal,
51 voltage control energization circuit, 52 charge detection circuit,
59 constant voltage control circuit, 60 charging power supply,
Ri resistance (current limiting element)

Claims (9)

  An electrode body in which a positive electrode capable of occluding and releasing anions and a negative electrode capable of occluding and releasing lithium ions are opposed to each other through a separator includes a plurality of storage cells housed in a sealed container together with a non-aqueous electrolyte. A power storage device connected in series, wherein each cell has a third electrode having lithium metal disposed in the non-aqueous electrolyte, and the potential difference between the third electrode and the positive electrode is equal to or greater than a predetermined value. A power storage device characterized in that the potential of the positive electrode is controlled with respect to the third electrode by sometimes electrically connecting the third electrode and the positive electrode.   2. The operation according to claim 1, wherein when the potential difference between the third electrode and the positive electrode is equal to or greater than a predetermined value, the operation of conducting the conductive connection between the third electrode and the positive electrode is performed only when the cell is charged. A power storage device.   The power storage device according to claim 1, wherein the operation is performed only when a charging current of the cell is equal to or less than a predetermined value.   4. The power storage cell used in the power storage device according to claim 1, wherein when the potential difference between the third electrode and the positive electrode exceeds a predetermined value, the third electrode and the positive electrode are conductively connected. An electricity storage cell comprising circuit means.   5. The voltage detecting means for monitoring a potential difference between the third electrode and the positive electrode as the circuit means, and when the voltage detecting means detects a potential difference of a predetermined value or more, the circuit means is turned on to operate the positive electrode and the positive electrode. A storage cell comprising switch means for conducting and connecting between the third electrodes.   5. The storage cell according to claim 4, wherein a constant voltage element having a predetermined voltage threshold is used as the circuit means.   7. The storage cell according to claim 4, wherein the negative electrode uses graphite as a negative electrode material capable of inserting and extracting lithium ions.   8. A method of manufacturing a power storage cell used in the power storage device according to claim 4, wherein a current is passed between the negative electrode and the third electrode to preliminarily store lithium ions in the negative electrode. Cell manufacturing method. 9. The method for manufacturing a storage cell according to claim 8, wherein the negative electrode and the third electrode are conductively connected directly or via a current limiting element in order to allow a current to flow between the negative electrode and the third electrode.

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