| abstract |
A solvent, an electrolyte salt, and at least one heteropoly acid salt compound represented by the following formulas (I) and (II). (I) H x A y [BD 12 O 40 ] .zH 2 O (I) ≪ H p A q [B 5 D 30 O 110 ] rH 2 O (II) Wherein, A is Li, Na, K, Rb, Cs, Mg, Ca, Al, NH 4 or an ammonium salt, or represents a phosphonium salt; B represents P, Si, As, or Ge; D is selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Tc, Rh, Cd, In, Sn, Ta, At least one element; x, y and z are values of ranges (0? x? 1), (2? y? 4) and (0? z? 5), respectively; p, q and r are values in the range of 0? p? 5, 10? q? 15 and 0? r? 15, respectively. |