JP6260218B2 - Aqueous secondary battery - Google Patents

Description

  The present invention relates to an aqueous secondary battery, and more particularly to an aqueous secondary battery in which lithium ions and / or sodium ions are dissolved.

Conventionally, as this type of aqueous secondary battery, a negative electrode containing a composite compound containing titanium and phosphorus (for example, LiTi ₂ (PO ₄ ) ₃ or NaTi ₂ (PO ₄ ) ₃ ) as a negative electrode active material, sodium ion And an electrolytic solution that is an aqueous solution in which is dissolved (for example, see Patent Document 1). This battery can be operated with an aqueous electrolyte containing sodium ions. As the aqueous secondary battery, a negative electrode active material such as Na ₃ V ₂ (PO ₄₎ and the positive electrode active material represented by _3, for example, LiTi ₂ (PO _{4) 3} and NaTi ₂ (PO _{4) 3} Have been proposed (see, for example, Patent Document 1). This battery can occlude and release sodium ions in the positive electrode and the negative electrode, has high durability, and has higher output and higher rate than non-aqueous secondary batteries and aqueous lithium secondary batteries. It has characteristics. For example, sodium ions in an aqueous solution have a relatively small interaction with hydration water, so that the dehydration energy during insertion and desorption of sodium ions, which is an electrode reaction, is small, and the insertion and desorption is faster than lithium ions. It is because it shows a separation characteristic.

JP 2011-86402 A JP 2012-3928 A

  However, the aqueous secondary batteries of Patent Documents 1 and 2 described above can operate relatively stably, but the cycle durability may be lower than that of a non-aqueous lithium secondary battery or the like. In the case of aqueous secondary batteries, there are currently only a few types of active materials that can be used, and whether or not they can be charged / discharged is being investigated. It wasn't.

  This invention is made | formed in view of such a subject, and it aims at providing the aqueous solution type secondary battery which can improve cycling durability more.

  As a result of diligent research to achieve the above-described object, the inventors of the present invention assume that in an aqueous battery using lithium ions and sodium ions as charge carriers, the electrolyte contains either one of zinc ions and lead ions. Thus, the present inventors have found that the cycle durability can be further improved and completed the present invention.

  That is, the aqueous secondary battery of the present invention has a positive electrode, a negative electrode, a lithium ion and / or sodium ion dissolved between the positive electrode and the negative electrode, and at least one of zinc ion and lead ion. And an electrolytic solution that is an aqueous solution.

The aqueous secondary battery of the present invention can further improve cycle durability. The reason why such an effect is obtained is presumed as follows. For example, an aqueous electrolyte solution has a problem that electrolysis of water occurs during charging and discharging. In the aqueous secondary battery of the present invention, zinc ions and lead ions contained in the electrolytic solution are adsorbed on the surface of the negative electrode active material and the conductive material as anion or a part of an OH ⁻ ion. It is presumed that the overvoltage of the hydrogen generation reaction of the negative electrode is increased, hydrogen generation on the negative electrode that is charged and discharged is further suppressed, and the deviation in capacity balance between the positive and negative electrodes is further suppressed. For this reason, it is thought that cycle durability can be improved more.

The schematic diagram which shows an example of the aqueous solution type secondary battery 10 of this invention.

  The aqueous secondary battery of the present invention is an aqueous solution containing at least one of zinc ions and lead ions, which is interposed between the positive electrode, the negative electrode, and the positive electrode and the negative electrode, in which lithium ions and / or sodium ions are dissolved. An electrolyte solution. In addition, when lithium ion is melt | dissolved in electrolyte solution, it is an aqueous solution type lithium secondary battery, and when sodium ion is melt | dissolved in electrolyte solution, it is an aqueous solution type sodium secondary battery.

The positive electrode of the aqueous secondary battery of the present invention may include a positive electrode active material that absorbs and releases lithium ions. The positive electrode of the aqueous secondary battery of the present invention may contain a positive electrode active material that occludes and releases sodium ions. The positive electrode active material can be used without particular limitation as long as it can occlude and release alkali (lithium or sodium) ions in an aqueous solution. For example, at least one of lithium iron phosphate and Prussian blue analogs can be used. One may be included. Among these, the Prussian blue analog is more preferable because the upper limit voltage during charging can be further increased and cycle durability can be further improved. Lithium iron phosphate occludes and releases lithium ions and may have the basic composition formula LiFePO ₄ . In addition, Prussian blue analogs containing sodium occlude and release sodium ions. The Prussian blue analog may include, for example, sodium and further one or more of nickel, copper, manganese, and zinc. This positive electrode active material includes basic composition formula Na ₂ NiFe (CN) ₆ , basic composition formula Na ₂ CuFe (CN) ₆ , basic composition formula Na ₂ MnFe (CN) ₆ , basic composition formula Na ₂ Zn ₃ [Fe ( CN) ₆ ] ₂ may be a Prussian blue analogue, of which the Prussian blue analogue of the basic composition formula Na ₂ MnFe (CN) ₆ and the basic composition formula Na ₂ Zn ₃ [Fe (CN) ₆ ] ₂ is more preferable. The positive electrode active material has a basic composition formula Na _x K _y M _z Fe (CN) ₆ .aH ₂ O (where M is one or more of Mn and Zn, 0.5 <x ≦ 2.0, 0 ≦ It may be a Prussian blue analog represented by y ≦ 0.50, 1.0 ≦ z ≦ 2.0, and a is an arbitrary number). At this time, the Prussian blue analog may not contain K, but it is more preferable to contain K. For example, in the above basic composition formula, it is preferable that 0.05 ≦ y ≦ 0.20. In addition, lithium iron phosphate and Prussian blue analogs may have a part of each element in the basic composition formula substituted with other elements, and not only in a stoichiometric composition, but also in some elements. It may have a non-stoichiometric composition that is deficient or excessive. In the aqueous secondary battery of the present invention, as the positive electrode active material, the above-mentioned Prussian blue analogs may be used alone or in combination of two or more, or other compounds may be included.

  The Prussian blue analog as the positive electrode active material can be prepared by mixing an aqueous solution containing any one or more of nickel ions, copper ions, manganese ions and zinc ions with an aqueous solution of sodium hexacyanoferrate (II). it can. Examples of the aqueous solution containing these ions include a nitrate aqueous solution and a sulfate aqueous solution. Mixing of this aqueous solution can be performed at room temperature (20 degreeC or 25 degreeC), for example. The aqueous solution is preferably mixed in an inert atmosphere such as nitrogen or a rare gas. Further, it is more preferable to stir for a predetermined time after mixing the aqueous solutions. In this way, the particle size of the generated powder can be adjusted.

  The positive electrode of the aqueous secondary battery of the present invention may be, for example, a positive electrode material obtained by mixing a positive electrode active material, a conductive material, and a binder, and may be pressure-bonded to the surface of the current collector. A paste obtained by adding a suitable solvent may be applied to the surface of the current collector and dried, and may be compressed to increase the electrode density as necessary. The conductive material contained in the positive electrode is not particularly limited as long as it is an electron conductive material that does not adversely affect the battery performance of the positive electrode. For example, graphite such as natural graphite (scale-like graphite, scale-like graphite) or artificial graphite, acetylene black , Carbon black, ketjen black, carbon whisker, needle coke, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) or a mixture of two or more thereof can be used. Among these, as the conductive material, carbon black and acetylene black are preferable from the viewpoints of electron conductivity and coatability. The binder serves to bind the active material particles and the conductive material particles. For example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), fluorine-containing resin such as fluorine rubber, or polypropylene, Thermoplastic resins such as polyethylene, ethylene-propylene-dienemer (EPDM), sulfonated EPDM, natural butyl rubber (NBR), styrene butadiene rubber (SBR), polyacrylonitrile (PAN), etc. alone or as a mixture of two or more Can be used. As a solvent for dispersing the positive electrode active material, the conductive material, and the binder, water or an organic solvent can be used. As the organic solvent, for example, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran and the like can be used. Examples of the application method include roller coating such as applicator roll, screen coating, doctor blade method, spin coating, bar coater, and the like, and any of these can be used to obtain an arbitrary thickness and shape. As the current collector, aluminum, titanium, stainless steel, nickel, baked carbon, a conductive polymer, conductive glass, or the like can be used. Among these, in consideration of conductivity and corrosion resistance, it is preferably formed of at least one selected from aluminum, nickel and titanium. Two or more types of current collectors may be used in combination. Examples of the shape of the current collector include foil, film, sheet, net, punched or expanded, lath, porous, foam, and formed fiber group. The thickness of the current collector is, for example, 1 to 500 μm.

The negative electrode of the aqueous secondary battery of the present invention may contain a negative electrode active material that occludes and releases lithium ions. The negative electrode of the aqueous secondary battery of the present invention may contain a negative electrode active material that occludes and releases sodium ions. The negative electrode active material is not particularly limited as long as it can occlude and release alkali (lithium or sodium) ions in an aqueous solution. For example, the negative electrode active material may be a composite compound containing titanium and phosphorus. The composite compound is, for example, A _x Ti ₂ (PO ₄ ) ₃ (where A is one or more selected from alkali metals and alkaline earth metals, and X is 0 or more and 3 or less). Also good. This element A is preferably lithium and sodium. For example, the composite compound is preferably at least one of a basic composition formula LiTi ₂ (PO ₄ ) ₃ and a basic composition formula NaTi ₂ (PO ₄ ) ₃ having a NASICON type structure. LiTi ₂ (PO ₄ ) ₃ and NaTi ₂ (PO ₄ ) ₃ can occlude and release lithium ions and sodium ions. For example, both insertion and desorption potentials of sodium ions are −0.75 V (vs. Ag / AgCl) grade. This is preferable because, when sodium ions are occluded and released, the potential of the negative electrode taking into account the overvoltage of hydrogen generation at the negative electrode is a favorable potential, and a larger battery voltage can be realized. In the aqueous secondary battery of the present invention, as the negative electrode active material, a NASICON negative electrode active material may be used alone or in combination of two or more, or other compounds may be included. Note that the negative electrode active material may not have a NASICON type structure. Further, the surface of the negative electrode active material is preferably coated with a conductive phase. The composite compound described above is often an insulator and preferably has high conductivity. The conductive phase is not particularly limited as long as it can increase conductivity, and for example, one or more of carbon, metal, nitride, boride, oxide, conductive polymer, and the like can be used.

  The negative electrode of the aqueous secondary battery of the present invention may be prepared by, for example, mixing a negative electrode active material, a conductive material, and a binder to form a negative electrode material, which may be pressure-bonded to the surface of the current collector. A paste obtained by adding a suitable solvent may be applied to the surface of the current collector and dried, and may be compressed to increase the electrode density as necessary. As the conductive material, binder, solvent and the like used for the negative electrode, those exemplified for the positive electrode can be used. For the current collector of the negative electrode, aluminum, nickel, stainless steel, titanium, baked carbon, a conductive polymer, conductive glass, or the like can be used. Among these, in consideration of conductivity and corrosion resistance, it is preferably formed of at least one selected from aluminum, nickel and titanium. This current collector may be used in combination of two or more. The shape of the current collector can be the same as that of the positive electrode.

In the aqueous secondary battery of the present invention, the aqueous electrolyte is not particularly limited as long as it has a lithium salt as a main electrolyte or a sodium salt as a main electrolyte. Examples of the lithium salt include LiNO ₃ , Li ₂ SO ₄ , LiOH, LiCl, and CH ₃ COOLi. Among these, LiNO ₃ and Li ₂ SO ₄ are preferable from the viewpoint of solubility in water. These lithium salts can be used alone or in combination of two or more. Examples of the sodium salt include NaNO ₃ , Na ₂ SO ₄ , NaOH, NaCl, and CH ₃ COONa. Among these, NaNO ₃ and Na ₂ SO ₄ are preferable from the viewpoint of solubility in water. These sodium salts can be used alone or in combination of two or more. The aqueous electrolyte solution preferably contains 1 mol / L or more of alkali ions (lithium ions and / or sodium ions). This is because the exchange current density of the electrode reaction is considered to be sufficiently high, and high output characteristics can be realized. In addition, it is preferable that the density | concentration of an alkali ion is below a solubility limit. The pH of the aqueous electrolyte solution is preferably 3 or more and 11 or less. If the pH of the aqueous electrolyte is 3 or higher, the hydrogen generation overvoltage on the negative electrode does not become too small, so that hydrogen generation, which is a side reaction, competes with the battery reaction to reduce the charge / discharge efficiency. Can be preferred. Further, if the pH of the aqueous electrolyte is 11 or less, the oxygen generation overvoltage on the positive electrode does not become too small, so that oxygen generation, which is a side reaction, competes with the battery reaction and the charge / discharge efficiency decreases. Can be suppressed, which is preferable. Moreover, if pH of aqueous electrolyte solution is 3 or more and 11 or less, it can suppress more that a metal elutes from the collector of a positive / negative electrode etc., for example, and is preferable.

  In the aqueous secondary battery of the present invention, the aqueous electrolyte contains at least one of zinc ions and lead ions. This aqueous electrolyte solution preferably contains 0.01 mol / L or more of zinc ions, and more preferably contains 0.05 mol / L or more. When the zinc ions are 0.01 mol / L or more, the effect of adding zinc ions, for example, the effect of improving cycle durability can be further expressed. The aqueous electrolyte solution preferably contains zinc ions in a range of less than 0.50 mol / L, and more preferably in a range of 0.20 mol / L or less. When the zinc ion is less than 0.50 mol / L, precipitation as zinc metal on the negative electrode can be further suppressed, which is preferable. The aqueous electrolyte solution preferably contains 0.01 mol / L or more of lead ions, and more preferably contains 0.05 mol / L or more. When the lead ion is 0.01 mol / L or more, the effect of adding lead ion, for example, the effect of improving cycle durability can be further expressed. The aqueous electrolyte solution preferably contains lead ions in a range of less than 0.50 mol / L, and more preferably in a range of 0.20 mol / L or less. In the range where lead ions are less than 0.50 mol / L, it is possible to further suppress the precipitation of lead metal on the negative electrode, which is preferable. This aqueous electrolyte solution preferably contains at least one of zinc ions and lead ions, and may contain two types. In addition, zinc ions and lead ions may be added to the aqueous electrolyte solution by nitrates, sulfates, hydroxides, chlorides, acetates, or the like. Of these, nitrates and sulfates are preferred. That is, the counter anion of zinc ion and lead ion may be at least one of nitrate ion and sulfate ion.

  The aqueous secondary battery of the present invention may include a separator between the positive electrode and the negative electrode. The separator is preferably subjected to a hydrophilic treatment so that the aqueous electrolyte solution can penetrate and ions can easily pass therethrough. The separator is not particularly limited as long as it is a composition that can withstand the range of use of an aqueous sodium secondary battery. For example, polymer nonwoven fabrics such as polypropylene nonwoven fabrics and polyphenylene sulfide nonwoven fabrics, and olefinic resins such as polyethylene and polypropylene are used. A thin microporous membrane can be mentioned. These may be used alone or in combination.

  The shape of the aqueous secondary battery of the present invention is not particularly limited, and examples thereof include a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, and a square type. Moreover, you may apply to the large sized thing etc. which are used for an electric vehicle etc. FIG. 1 is a schematic view showing an example of the aqueous solution type secondary battery 10 of the present invention. This aqueous secondary battery 10 includes a positive electrode sheet 13 in which a positive electrode active material 12 is formed on a current collector 11, a negative electrode sheet 18 in which a negative electrode active material 17 is formed on the surface of a current collector 14, a positive electrode sheet 13 and a negative electrode The separator 19 provided between the sheet 18 and the electrolytic solution 20 filling the space between the positive electrode sheet 13 and the negative electrode sheet 18 are provided. In this aqueous secondary battery 10, a separator 19 is sandwiched between a positive electrode sheet 13 and a negative electrode sheet 18, these are wound and inserted into a cylindrical case 22, and a positive electrode terminal 24 and a negative electrode sheet connected to the positive electrode sheet 13. And a negative electrode terminal 26 connected to each other. Here, the electrolytic solution 20 is an aqueous solution in which lithium ions and / or sodium ions are dissolved and contains at least one of zinc ions and lead ions.

In the aqueous solution type secondary battery of the present embodiment described in detail above, cycle durability can be further improved. The reason why such an effect is obtained is presumed as follows. For example, an aqueous electrolyte solution has a problem that electrolysis of water occurs during charging and discharging. In the aqueous secondary battery of the present invention, zinc ions and lead ions contained in the electrolytic solution are adsorbed on the surface of the negative electrode active material and the conductive material as anion or a part of an OH ⁻ ion. It is presumed that the overvoltage of the hydrogen generation reaction of the negative electrode is increased, hydrogen generation on the negative electrode that is charged and discharged is further suppressed, and the deviation in capacity balance between the positive and negative electrodes is further suppressed. For this reason, it is thought that cycle durability can be improved more. In the aqueous sodium secondary battery of the present embodiment, an aqueous solution containing abundant sodium ions and relatively abundant zinc ions and lead ions in the earth's crust and seawater is used as an electrolyte solution. From the viewpoint of quantity, it is superior in terms of cost and mass productivity. Furthermore, in the case where the Prussian blue analog containing sodium is used as the positive electrode active material, it can be prepared by mixing a nitrate of manganese or zinc and a sodium hexacyanoferrate (II) solution, and an easier manufacturing process Can be manufactured.

  It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

  Hereinafter, an example in which an aqueous solution type secondary battery including an electrolytic solution that is an aqueous solution containing zinc ions or lead ions and in which lithium ions or sodium ions are dissolved will be described as an example. First, a method for manufacturing an active material will be described.

<Preparation of LiFePO ₄ >
As a starting material, iron fumarate having a valence of iron and lithium dihydrogen phosphate are mixed at a molar ratio of Fe: P of 1: 1, and formed into a pellet shape at 650 ° C. in an Ar atmosphere. LiFePO ₄ was produced by firing for 16 hours underneath.

<Preparation of Na ₂ MnFe (CN) ₆ >
Manganese nitrate and sodium hexacyanoferrate (II) were each sufficiently dissolved in deoxygenated deionized water in an inert atmosphere. The aqueous solution in which manganese nitrate was dissolved was mixed with an aqueous solution of sodium hexacyanoferrate (II) and stirred overnight under an inert atmosphere. The resulting white powder was filtered and dried to obtain a powder of the basic composition formula Na ₂ MnFe (CN) ₆ . The composition analysis of the obtained powder was performed by ICP analysis, the amount of water of crystallization was measured by thermogravimetry, and expressed as a relative value with the number of moles of iron taken as 1, the composition formula was Na _1.51 K _0.09 Mn _1.13 Fe (CN) ₆ .3.0H ₂ O.

<Preparation of LiTi ₂ (PO ₄ ) ₃ >
Titanium isopropoxide, lithium acetate, and ammonium dihydrogen phosphate were used as raw materials. A solution in which titanium isopropoxide is diluted with 2-propanol and a solution in which lithium acetate and ammonium dihydrogen phosphate are dissolved in water are mixed so as to have a composition of LiTi ₂ (PO ₄ ) ₃ , and titanium isopropoxide is mixed. Was hydrolyzed. The resulting cloudy solution was vacuum-dried to obtain a white powder. The obtained powder was heat-treated at 400 ° C. for 12 hours and then calcined in air at 700 ° C. for 16 hours to obtain a LiTi ₂ (PO ₄ ) ₃ powder. The obtained LiTi ₂ (PO ₄ ) ₃ powder was subjected to carbon coating to enhance conductivity. LiTi ₂ (PO ₄ ) ₃ powder is put into an aqueous solution in which sucrose as a carbon source is dissolved, dried, and then treated at 650 ° C. for 4 hours in an inert atmosphere (Ar). Coated.

<Preparation of NaTi ₂ (PO ₄ ) ₃ >
A powder of NaTi ₂ (PO ₄ ) ₃ was obtained through the same process as the preparation of LiTi ₂ (PO ₄ ) ₃ except that sodium acetate was used instead of lithium acetate as a raw material. The obtained powder was carbon coated in the same manner as LiTi ₂ (PO ₄ ) ₃ .

[Example 1]
An aqueous secondary battery using a positive electrode containing LiFePO ₄ as a positive electrode active material, a negative electrode containing LiTi ₂ (PO ₄ ) ₃ as a negative electrode active material, and an electrolytic solution which is an aqueous solution containing LiNO ₃ as an electrolyte was produced. 80% by mass of the positive electrode active material, 10% by mass of carbon black as a conductive material, 10% by mass of a mixture of carboxymethyl cellulose and styrene butadiene rubber as a binder, and mix well, and an appropriate amount of water is added and dispersed. Thus, a slurry-like positive electrode mixture was obtained. The positive electrode mixture was applied to both sides of an aluminum foil having a thickness of 20 μm, dried, and then densified with a roll press to obtain a positive electrode sheet electrode. The positive electrode sheet electrode was cut into a predetermined shape, and an Al tab was welded to the exposed portion of the current collector foil. Next, 80% by mass of the negative electrode active material, 10% by mass of carbon black as a conductive material, 10% by mass of a mixture of carboxymethyl cellulose and styrene butadiene rubber as a binder are mixed well, and an appropriate amount of water is added as a dispersant. And dispersed to obtain a slurry-like negative electrode mixture. This negative electrode mixture was applied to both sides of an aluminum foil having a thickness of 20 μm and dried, and then densified with a roll press to obtain a negative electrode sheet electrode. This negative electrode sheet electrode was cut into a predetermined shape, and an Al tab was welded to the exposed portion of the current collector foil. The prepared positive / negative electrode sheet electrodes were wound into a roll shape through a polyolefin separator subjected to a hydrophilic treatment, inserted into a cylindrical aluminum laminate outer package, injected with an electrolytic solution, and then welded and sealed. This battery was a positive electrode regulated battery having a positive electrode capacity smaller than the negative electrode capacity, and a design capacity of 200 mAh. As the electrolytic solution, a 6 mol / L LiNO ₃ aqueous solution in which 0.05 mol / L ZnSO ₄ was dissolved was used. The pH of the electrolytic solution was 5. The obtained aqueous secondary battery was referred to as Example 1.

[Examples 2 and 3]
An aqueous secondary battery was prepared in the same manner as in Example 1 except that a 6 mol / L LiNO ₃ aqueous solution was dissolved in 0.10 mol / L and 0.20 mol / L ZnSO ₄ as the electrolytic solution. These were designated as Examples 2 and 3, respectively.

[Example 4]
An aqueous secondary battery was prepared in the same manner as in Example 1 except that a ₂ mol / L Li ₂ SO ₄ aqueous solution was dissolved in 0.05 mol / L ZnSO ₄ as an electrolytic solution. It was set to 4. The pH of the electrolytic solution was 5.

[Example 5]
An aqueous secondary battery was prepared in the same manner as in Example 1 except that a 6 mol / L LiNO ₃ aqueous solution was used and an 0.05 mol / L PbSO ₄ solution was used as the electrolytic solution. did.

[Example 6]
Na ₂ MnFe (CN) ₆ is used as the positive electrode active material, NaTi ₂ (PO ₄ ) ₃ is used as the negative electrode active material, and 0.05 mol / L ZnSO ₄ is dissolved in 5 mol / L NaNO ₃ aqueous solution as the electrolyte. An aqueous solution type secondary battery was produced in the same manner as in Example 1 except that the prepared one was used, and Example 6 was obtained.

[Example 7]
An aqueous secondary battery was prepared in the same manner as in Example 6 except that a ₂ mol / L Na ₂ SO ₄ aqueous solution was dissolved in 0.05 mol / L ZnSO ₄ as the electrolyte. It was set to 7.

[Example 8]
An aqueous secondary battery was prepared in the same manner as in Example 6 except that a 5 mol / L NaNO ₃ aqueous solution in which 0.05 mol / L PbSO ₄ was dissolved was used as the electrolytic solution. did.

[Comparative Example 1]
An aqueous secondary battery was prepared in the same manner as in Example 1 except that a 6 mol / L LiNO ₃ aqueous solution that did not dissolve ZnSO ₄ or PbSO ₄ was used as an electrolytic solution.

[Comparative Example 2]
An aqueous secondary battery was prepared in the same manner as in Example 1 except that a 6 mol / L LiNO ₃ aqueous solution dissolved in 0.50 mol / L ZnSO ₄ was used as the electrolytic solution. did.

[Comparative Example 3]
An aqueous secondary battery was prepared in the same manner as in Example 1 except that a ₂ mol / L Li ₂ SO ₄ aqueous solution that did not dissolve ZnSO ₄ or PbSO ₄ was used as an electrolytic solution. .

[Comparative Example 4]
An aqueous secondary battery was prepared in the same manner as in Example 6 except that a 5 mol / L NaNO ₃ aqueous solution that did not dissolve ZnSO ₄ or PbSO ₄ was used as an electrolytic solution.

[Comparative Example 5]
An aqueous secondary battery was prepared in the same manner as in Example 6 except that a ₂ mol / L Na ₂ SO ₄ aqueous solution that did not dissolve ZnSO ₄ or PbSO ₄ was used as an electrolytic solution. . Table 1 shows the positive electrode active material, the negative electrode active material, the electrolytic solution, the types and amounts of additives, the upper limit voltage and the lower limit voltage for battery performance evaluation of each example and comparative example.

(Battery performance evaluation)
The activation process was performed with respect to each produced battery. First, charging and discharging were performed for 3 cycles at 0.2 C between the upper limit voltage and the lower limit voltage set according to the active material. Next, after constant current charging at 0.1 C up to the upper limit voltage, constant voltage charging was performed, and then constant current discharging was performed up to the lower limit voltage at 0.1 C. The capacity obtained at this time was defined as the initial capacity (mAh). Table 2 shows the configuration, upper limit voltage, and lower limit voltage of each battery. Moreover, the cycle durability test was done using each battery which performed the activation process. Between the upper limit voltage and the lower limit voltage set according to the active material, 200 cycles were charged and discharged at 25 ° C. and 1 C. Next, constant current charging was performed at 0.1 C up to the upper limit voltage, followed by constant voltage charging, and then constant current discharging was performed at 0.1 C up to the lower limit voltage. Further, (capacity after endurance) / (initial capacity) × 100 was defined as a capacity retention rate (%).

(Experimental result)
Table 2 shows the results of battery performance evaluation of Examples 1 to 8 and Comparative Examples 1 to 5. As shown in Table 2, as compared with Comparative Examples 1 and 3 to 5, in Examples 1 to 8 to which the additive was added, the capacity maintenance rate was about 80% or more, and a higher capacity maintenance rate was shown. . In particular, with the same electrode and electrolyte composition, with an appropriate amount of additive added, an improvement of 10% or more in capacity retention was confirmed. This was presumed to be because the capacity shift between the positive electrode and the negative electrode could be reduced by suppressing the hydrogen generation at the negative electrode. On the other hand, in Comparative Example 2 in which zinc sulfate was added at 0.5 mol / L, the capacity retention rate was lowered. Although the reason for this has not been confirmed, it is considered that a precipitation reaction of zinc that cannot be ignored has probably occurred, and the capacity retention rate has therefore decreased. It was revealed that the cycle durability of the aqueous lithium secondary battery and aqueous sodium secondary battery can be further improved by adding appropriate amounts of zinc ions and lead ions to the electrolytic solution. Moreover, it was guessed that the addition amount of a zinc ion and lead ion has the preferable range of 0.05 mol / L or more and 0.20 mol / L or less, and it is more preferable that it is about 0.10 mol / L.

  The present invention is applicable to the battery industry.

  DESCRIPTION OF SYMBOLS 10 Aqueous-type secondary battery, 11 Current collector, 12 Positive electrode active material, 13 Positive electrode sheet, 14 Current collector, 17 Negative electrode active material, 18 Negative electrode sheet, 19 Separator, 20 Electrolytic solution, 22 Cylindrical case, 24 Positive electrode terminal, 26 Negative terminal.

Claims (4)

A positive electrode containing at least one of lithium iron phosphate and a Prussian blue analog as a positive electrode active material that occludes and releases lithium ions and / or sodium ions;
A negative electrode including a composite compound containing titanium and phosphorus as a negative electrode active material that occludes and releases lithium ions and / or sodium ions;
An electrolyte solution that is an aqueous solution that is interposed between the positive electrode and the negative electrode and in which lithium ions and / or sodium ions are dissolved and contains at least one of zinc ions and lead ions,
The electrolytic solution contains the zinc ions and / or the lead ions in a range of 0.20 mol / L or less,
The Prussian blue analog has a basic composition formula Na _x K _y M _z Fe (CN) ₆ .aH ₂ O (where M is one or more of Mn and Zn, 0.5 <x ≦ 2.0, 0 ≦ y ≦ 0.50, 1.0 ≦ z ≦ 2.0, and a is an arbitrary number)
Aqueous secondary battery. The electrolyte, the zinc ion and / or the lead ions is contained in a range on 0.01 mol / L or less, aqueous secondary battery according to claim 1. The electrolyte, the zinc ion and / or the lead ions is contained in a range on 0.05 mol / L or less, aqueous secondary battery according to claim 1 or 2.   The aqueous electrolyte secondary battery according to claim 1, wherein the electrolytic solution contains at least one of nitrate ions and sulfate ions.

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