JP2008041420A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery with high economic efficiency. <P>SOLUTION: The secondary battery is provided with a battery part 12 including a positive electrode 2, a negative electrode 1, and a diaphragm 3 provided between the positive electrode 2 and negative electrode 1, and the same phosphoric acid solutions are filled between the positive electrode 2 and diaphragm 3 and between the negative electrode 1 and diaphragm 3 of the battery part 12, respectively. Thereby, the phosphoric acid solution as an electrolyte solution can be varied in valency greatly without solubility limitation, has large energy density, is inexpensive, and provides high economic efficiency. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a secondary battery that stores electric power energy.

  One of the secondary batteries is a redox flow battery. A redox flow battery is a so-called redox ion solution having a plurality of ionic valences, such as iron divalent and trivalent cations, and taking different oxidation-reduction states, as an electrolytic solution from a storage tank to a flow-through electrolytic tank. Say what you use. As redox ions, iron, chromium, vanadium, titanium, and the like have been studied. Among them, a large apparatus has been put to practical use in vanadium. Usually, the electrode active material of many secondary batteries is solid and enclosed in the battery, whereas the electrode active material of a redox flow battery is a liquid electrolyte solution.

  A conventionally known albanadium redox flow battery (see, for example, Patent Document 1) is illustrated in FIG.

As shown in the figure, the positive electrode 30 and the negative electrode 31 transfer and receive equal charges. Therefore, at the time of charging, vanadium is changed from tetravalent to pentavalent in the electrolyte solution on the positive electrode 30 side, and at the same time, vanadium is changed from trivalent to divalent in the electrolyte solution on the negative electrode 31 side. Further, at the time of discharge, vanadium becomes pentavalent to tetravalent in the electrolyte solution on the positive electrode 30 side, and at the same time, vanadium becomes divalent to trivalent in the electrolyte solution on the negative electrode 31 side. Further, the electrolyte solution on the positive electrode 30 side and the negative electrode 31 side is partitioned by an ion exchange membrane 32, and the electrolyte solutions on both sides are mixed to prevent the valence from being neutralized and the loss of power. In addition, the storage tanks 33 and 34 and the pumps 36 and 37 are provided, and the storage tanks 33 and 34 can be set large to store a huge amount of electric power. Because of the simple configuration, the cycle life is long and maintenance management is easy. There are excellent features such as.
JP-A-6-188005

  However, in the conventional configuration, the solubility of the electrode active material such as vanadium is limited, so that the energy density is low and the large storage tanks 33 and 34 are required. Further, the electrode reaction is slow, and the battery unit 35 is also large. The electrolyte vanadium was expensive and never economically sufficient.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a secondary battery that can have high economic efficiency.

  In order to solve the conventional problems, the secondary battery of the present invention includes a battery unit having a positive electrode and a negative electrode, and a diaphragm provided between the positive electrode and the negative electrode, and between the positive electrode and the diaphragm of the battery unit, The same phosphoric acid solution is filled between the negative electrode and the diaphragm.

  As a result, the phosphoric acid solution as the electrolyte solution is not limited in solubility, can have a large valence change, has a large energy density, is inexpensive, and can be highly economical.

  The secondary battery of the present invention uses a phosphoric acid solution as an electrolyte solution and has high economic efficiency.

  1st invention is equipped with the battery part which has a positive electrode and a negative electrode, and the diaphragm provided between the positive electrode and the negative electrode, and the same phosphoric acid solution between the positive electrode and diaphragm of this battery part, and between the negative electrode and the diaphragm, respectively By using a secondary battery filled with, the phosphoric acid solution as the electrolyte solution has no limitation on solubility, can have a large valence change, has a large energy density, is inexpensive, and can be highly economical. .

  According to a second aspect of the invention, in particular, in the first aspect of the invention, a storage tank is provided outside the battery unit, and a phosphoric acid solution is circulated between the storage tank and the battery unit using a liquid delivery device, thereby allowing external power storage. A large storage capacity including the capacity can be realized.

  In the third invention, in particular, by using a cation exchange membrane as the diaphragm in the first invention, it is possible to ensure conductivity, facilitate ion movement, and promote an electrode reaction.

  According to a fourth invention, in particular, in the first or second invention, the positive electrode and the negative electrode are porous carbon electrodes, and the phosphoric acid solution is present in the gap in the porous carbon electrode, whereby the phosphoric acid solution and the electrode The electrode contact can be increased by increasing the contact area with the electrode and expanding the reaction area.

  In the fifth invention, in particular, in the fourth invention, the positive and negative porous carbon electrodes are heated and immersed in a phosphoric acid solution and bonded to the cation exchange membrane of the diaphragm, whereby the porous carbon electrode and the positive carbon electrode are positively bonded. The conductivity of the gap with the ion exchange membrane can be ensured to facilitate ion movement and promote the electrode reaction.

  In the sixth invention, in particular, in any one of the first, fourth, and fifth inventions, the electrode reaction can be promoted by adding gold to the positive electrode.

  In the seventh invention, in particular, in any one of the first, fourth, and fifth inventions, the electrode reaction can be promoted by adding tin to the negative electrode.

  In an eighth aspect of the invention, in particular, in any one of the first, second, and fourth to sixth aspects of the invention, by attaching a magnetic substance to the positive and negative porous carbon electrodes, ion migration is facilitated, The electrode reaction can be promoted.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a secondary battery according to Embodiment 1 of the present invention.

  As shown in the figure, a negative electrode 1 and a positive electrode 2 made of carbon felt, which are porous carbon materials, face each other with a diaphragm 3 made of a cation exchange membrane provided between the negative electrode 1 and the positive electrode 2, and the battery unit 12 is Constitute. The gap in the porous carbon material of the negative electrode 1 and the positive electrode 2 is filled with a mixed solution of phosphoric acid and water in the initial state, and the phosphoric acid solution is communicated with the circulation paths 4 and 5, respectively. The positive electrode side electrolyte tank 7 is connected, and the negative electrode side pump 8 and the positive electrode side pump 9 are filled between the positive electrode 2 and the diaphragm 3 of the battery unit 12 and between the negative electrode 1 and the diaphragm 3, respectively. Circulate. Note that current collectors 10 and 11 are provided on the negative electrode 1 and the positive electrode 2, respectively.

  Next, the operation during charging / discharging of the secondary battery will be described.

  During charging, a negative potential is applied to the negative electrode 1 and a positive potential is applied to the positive electrode 2 from an external power source (not shown). Thus, electrons are applied from the negative electrode 1 on the material surface of the negative electrode 1 to generate phosphorous acid from phosphoric acid shown in (Chemical Formula 1) and hypophosphorous acid from phosphorous acid shown in (Chemical Formula 2). Let it be done.

  Therefore, in the entire reaction on the negative electrode 1 side, hypophosphorous acid is generated from phosphoric acid as shown in (Chemical Formula 3).

  On the surface of the positive electrode 2, the positive electrode 2 receives electrons and generates superphosphoric acid from phosphoric acid shown in (Chemical Formula 4). The hydrogen ions generated in accordance with (Chemical Formula 4) at the positive electrode 2 move to the negative electrode 1 side beyond the diaphragm 3 (Chemical Formula 1) and are consumed by the reaction of (Chemical Formula 2).

  At the time of discharging, an external load (not shown) is connected between the negative electrode 1 and the positive electrode 2. Thereby, on the surface of the negative electrode 1, phosphoric acid is generated from phosphorous acid shown in (Chemical Formula 5) and phosphorous acid is generated from hypophosphorous acid shown in (Chemical Formula 6), and the negative electrode 1 receives electrons.

  Therefore, the entire reaction on the negative electrode 1 side is in an initial state by generating phosphoric acid from hypophosphorous acid as shown in (Chemical Formula 7).

  On the surface of the positive electrode 2, phosphoric acid is generated from the superphosphoric acid shown in (Chemical Formula 8) and electrons are supplied from the positive electrode 2.

  Hydrogen ions generated in the negative electrode 1 according to (Chemical Formula 5) and (Chemical Formula 6) move to the positive electrode 2 side beyond the partition wall 3 and are consumed by the reaction of (Chemical Formula 8). Electrons exchanged at the positive electrode 2 and the negative electrode 1 flow through an external load circuit.

  The equilibrium potential of (Chemical Formula 4) and (Chemical Formula 8) is around 1.4V. Further, since the equilibrium potentials of (Chemical Formula 1), (Chemical Formula 5), (Chemical Formula 2), and (Chemical Formula 6) are in the vicinity of −0.28V and −0.5V, respectively, and are approximately −0.39V, It is a secondary battery that operates near 1.8V. This is more advantageous in terms of electromotive force than 1.47V of the albanadium redox flow battery.

  In the secondary battery of this embodiment, there is no limitation on solubility because a phosphoric acid solution that is normally liquid is used. Compared with an all vanadium redox flow battery with limited solubility of vanadium, a high concentration of about 8 times in molar concentration can be taken. Further, in the allavana redox flow battery, vanadium has a monovalent change on each of the positive electrode side and the negative electrode side. However, in the secondary battery of the present embodiment, the positive electrode 2 side divalent and the negative electrode 1 side tetravalent change. There is a three-fold valence change on average for the positive and negative electrodes. Together, the charge density of the electricity storage can be increased by about 24 times.

  For this reason, the energy density determined by the product of the electromotive force and the charge density can be increased, and a small and inexpensive secondary battery can be produced with the same charge capacity. Furthermore, phosphorus is an element that has a much larger amount of crust than vanadium, and has a large circulation and is inexpensive.

  Thus, the secondary battery of this embodiment can obtain a high energy density and economy.

(Embodiment 2)
Next, the secondary battery according to Embodiment 2 of the present invention will be described. Since the configuration of the secondary battery is the same as that of Embodiment 1, the description thereof is omitted.

  A feature of the secondary battery in the present embodiment is that a storage tank which is a negative electrode side electrolyte tank 6 and a positive electrode side electrolyte tank 7 is provided outside the battery unit 12, and a liquid feeding device which is a negative electrode side pump 8 and a positive electrode side pump 9. Is used to circulate the phosphoric acid solution between the storage tank and the battery unit 12.

  As described above, a storage tank is provided outside the battery unit 12 of the secondary battery, and the phosphoric acid solution is circulated between the storage tank and the battery unit using the liquid feeding device, thereby providing a large storage capacity of the phosphoric acid solution. Is increased outside the battery unit 12, and a large storage capacity including the external storage capacity can be realized.

(Embodiment 3)
Next, the secondary battery according to Embodiment 3 of the present invention will be described. Since the configuration of the secondary battery is the same as that of Embodiment 1, the description thereof is omitted.

  The feature of the secondary battery in the present embodiment is that the diaphragm 3 is a cation exchange membrane.

  As shown in (Chemical Formula 1) to (Chemical Formula 8) of the first embodiment, hydrogen ions that are cations travel between the two electrodes 1 and 2 in accordance with the electrode reaction of the phosphate electrolyte. The diaphragm 3, which is a cation exchange membrane, is superior in permeability of hydrogen ions, which are cations, as compared to a porous film. The electrical resistance of the phosphoric acid solution is 100 micrometers thick and has a fairly large resistance of about 20 ohms per square centimeter. In the case of a porous film diaphragm, even a film having a sufficient porosity becomes the resistance of the phosphoric acid solution contained in the porous film, resulting in a large resistance.

  Thus, by making the diaphragm 3 into a cation exchange membrane, it is about 0.2 to 1 ohm per 1 square centimeter, can ensure electroconductivity, facilitate ion movement, and can promote an electrode reaction. .

(Embodiment 4)
Next, a secondary battery according to Embodiment 4 of the present invention will be described. Since the configuration of the secondary battery is the same as that of Embodiment 1, the description thereof is omitted.

  The feature of the secondary battery in the present embodiment is that the positive electrode 2 and the negative electrode 1 are porous carbon electrodes, and the phosphoric acid solution is present in the gaps in the porous carbon electrode.

  Thus, by making the positive electrode and the negative electrode porous carbon electrodes and allowing the phosphoric acid solution to exist in the gaps in the porous carbon electrode, the contact area between the phosphoric acid solution and the electrode is larger than that of the plate-like electrode. Can be taken. For this reason, an electrode reaction area can be expanded and an electrode reaction can be promoted.

(Embodiment 5)
Next, a secondary battery according to Embodiment 5 of the present invention will be described. Since the configuration of the secondary battery is the same as that of Embodiment 1, the description thereof is omitted.

  The feature of the secondary battery in the present embodiment is that the porous carbon electrodes of the positive electrode 2 and the negative electrode 1 are preliminarily heated and immersed in a phosphoric acid solution, heated under conditions of 230 ° C. or less, and then pressed to cut phosphoric acid. . After that, the cation exchange membrane of the diaphragm 3 was sandwiched between the positive electrode 2 and the negative electrode 1 and was pressed by a press machine.

  Thus, heat immersion and pressure bonding ensure the conductivity of the gap between the porous carbon electrode and the cation exchange membrane, facilitate ion movement, and promote the electrode reaction.

(Embodiment 6)
Next, a secondary battery according to Embodiment 6 of the present invention will be described. Since the configuration of the secondary battery is the same as that of Embodiment 1, the description thereof is omitted.

  The feature of the secondary battery in the present embodiment is that gold is attached to the positive electrode 2 which is a porous carbon electrode.

  Gold acts as a catalyst for the reaction of (Chemical Formula 4) at the time of charging and the reaction of (Chemical Formula 8) at the time of discharging, and promotes the electrode reaction. Furthermore, gold has a large overvoltage for oxygen generation, and a reaction for generating oxygen from water (chemical formula 9), which is a side reaction at the time of charging, does not occur at a practical charging voltage, and power loss is small.

  Various methods can be used to attach gold to the porous carbon electrode. A method of sucking gold tetrachloride alcohol solution into carbon felt and heating it out of air, a method of depositing gold by adding alkaline formaldehyde solution to carbon felt sucked with gold tetrachloride, electroplating from gold tetrachloride It is a method to do.

  Thus, the electrode reaction can be promoted by attaching gold to the positive electrode 2.

(Embodiment 7)
Next, the secondary battery according to Embodiment 7 of the present invention will be described. Since the configuration of the secondary battery is the same as that of Embodiment 1, the description thereof is omitted.

  The feature of the secondary battery in the present embodiment is that tin is attached to the negative electrode 1 which is a porous carbon electrode.

  Tin acts catalytically with respect to the reactions of (Chemical Formula 1) and (Chemical Formula 2) at the time of charging and (Chemical Formula 5) and (Chemical Formula 6) at the time of discharge, and promotes the electrode reaction. Further, tin has a large hydrogen overvoltage, and the side reaction during charging (Chemical Formula 10) in which hydrogen is generated from water does not occur at a practical charging voltage, and power loss is small.

  For the attachment of tin to the porous carbon electrode, there is a method of electroplating from a tin salt.

  Thus, the electrode reaction can be promoted by adding tin to the negative electrode 1.

(Embodiment 8)
Next, a secondary battery according to Embodiment 8 of the present invention will be described. Since the configuration of the secondary battery is the same as that of Embodiment 1, the description thereof is omitted.

  A feature of the secondary battery in the present embodiment is that a magnetic material is attached to the porous carbon electrodes of the positive electrode 2 and the negative electrode 1.

  In the above configuration, the flow of current in the porous carbon electrode will be described with reference to FIG.

  In the figure, the periphery of the carbon fiber 21 in the porous carbon electrode is a phosphoric acid solution 22. An electron flow 23 carries an electric current through the carbon fiber 21. In the phosphoric acid solution 22 near the surface of the carbon fiber 21 in a complementary manner to the electron flow 23, the hydrogen ion flow 24 carries an electric current. In this case, what connects the electron flow 23 and the hydrogen ion flow 24 is a magnetic field 25 that can be formed in a right-handed direction with respect to the current.

  However, the phosphoric acid solution 22 has a small negative permeability and has no effect of inducing a complementary current. On the other hand, in the present embodiment, a magnetic material is attached to the porous carbon electrode to give a large magnetic permeability around the carbon fiber 21. As a result, the magnetic field 25 is strengthened, and a large flow 24 of hydrogen ions can be created, which facilitates ion movement and promotes the electrode reaction.

  Thus, by attaching a magnetic substance to the porous carbon electrodes of the positive electrode 2 and the negative electrode 1, ion migration can be facilitated and the electrode reaction can be promoted, and the battery unit 12 can be reduced in size.

  As described above, the secondary battery according to the present invention uses a phosphoric acid solution as an electrolyte solution and has high economic efficiency, and therefore can be applied to various devices and apparatuses.

Configuration diagram of secondary battery in Embodiments 1 to 8 of the present invention Explanatory drawing of the electric current flow in the porous carbon electrode in Embodiment 8 of this invention Configuration of conventional albanadium redox flow battery

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Negative electrode 2 Positive electrode 3 Diaphragm 4, 5 Circulation path 6 Negative electrode side electrolyte tank (storage tank)
7 Positive electrolyte tank (storage tank)
8 Negative side pump (liquid feeding device)
9 Positive side pump (liquid feeding device)
12 Battery section

Claims (8)

A secondary battery comprising a battery part having a positive electrode and a negative electrode, and a diaphragm provided between the positive electrode and the negative electrode, the same phosphoric acid solution being filled between the positive electrode and the diaphragm of the battery part and between the negative electrode and the diaphragm, respectively. . The secondary battery according to claim 1, wherein a storage tank is provided outside the battery part, and the phosphoric acid solution is circulated between the storage tank and the battery part using a liquid feeding device. The secondary battery according to claim 1, wherein the diaphragm is a cation exchange membrane. The secondary battery according to claim 1, wherein the positive electrode and the negative electrode are porous carbon electrodes, and the phosphoric acid solution is present in a gap in the porous carbon electrode. The secondary battery according to claim 4, wherein the porous carbon electrodes of the positive electrode and the negative electrode are heated and immersed in a phosphoric acid solution and pressure-bonded to the cation exchange membrane of the diaphragm. The secondary battery according to claim 1, wherein gold is attached to the positive electrode. The secondary battery according to claim 1, wherein tin is attached to the negative electrode. 7. The secondary battery according to claim 1, wherein a magnetic material is attached to the porous carbon electrodes of the positive electrode and the negative electrode.