Sodium intercalation into α- and β-VOSO4

Abstract

Na-ion battery is one of the best alternatives to Li-ion battery. Abundance of sodium on earth is three orders of magnitude higher than lithium, which should make Na-ion battery technology cheaper. But alkaline-ion battery prices, which tend to increase because of the massive world demand, also depend on the choice of electrode materials. Therefore, cost-effective electrode development remains an important subject of research because this will allow Na-ion battery to be even more competitive. Electrochemical performances of anhydrous VOSO₄ as electrode for Na-ion battery are reported in this letter. Two anhydrous phases of vanadyl sulfate have been studied. The first one, α-VOSO₄, shows that up to 0.8 sodium per formula unit (Na/f.u.) can be intercalated in this phase, and a reversible intercalation of 0.4 Na/f.u. has been observed with a strong polarization. The second one, β-VOSO₄, can intercalate up to 0.9 Na/f.u. with a reversible intercalation of 0.4 Na/f.u. leading to a reversible capacity of 64 mAh/g.