Electrochemical Intercalation of Li into Heteropoly 12 Molybdophosphoric Acid Ion-exchanged with Cs

Abstract

Electrochemical Li intercalation properties in 12-molybdophosphoric and 12-tangstophosphoric acids were investigated. It was found that both 12-molybdophosphoric and 12-tangstophosphoric acids exhibit fairly large capacity for the Li intercalation. Flat potential of 12-tangstophosphoric acids was 0.5 V, which could be used for the anode of Li ion battery. 12-molybdophosphoric acid exhibits the flat potential of 1.5 V, although cycle stability is not high. XRD measurement shows the formation of Li₂MoO₄ after the intercalation of Li. Therefore electrochemical Li intercalation occurs by redox between Mo⁶⁺ and Mo⁴⁺ and so the theoretical Li intercalation capacity in 12-molybdophosphoric acid is 373 mAh/g. Ion-exchanging H⁺ in 12-molybdophosphoric acid to Cs⁺ is effective to improve the cycle stability and capacity of ca. 200 mAh/g is sustained after 10 cycles. De-intercalation potential of 4.0 V is newly appeared by substitution of Mo in 12-molybdophosphoric acid with V although the capacity is still not large. Therefore, substitution of V is effective for increasing the Li intercalation potential.