NASICON-type Na3V2(PO4)3 as a new positive electrode material for rechargeable aluminium battery

Abstract

Although rechargeable aluminium-ion batteries could be very promising, there are only a few materials described in the literature that can insert aluminium. NASICON-type Na3V2(PO4)3 (NVP) is here investigated as a new positive electrode, using aluminium chloride dissolved in O2-free water as electrolyte solution. The reversible capacity is around 60–100 mAh g−1, depending on the cycling conditions. The electrochemical, analytical, NMR, XPS and XRD results all together corroborate that sodium is deinserted during first charge and then aluminium is inserted during the discharge. Both bulk insertion and surface capacitance can contribute to the specific capacity. This is the first report about true insertion of a trivalent cation into a NASICON-type structure. In addition, this material is also electrochemically active vs. Al metal in non-aqueous cell, using ionic liquid as electrolyte solution, with a revesible capacity about 60–70 mAh g−1 at ca. 1.25 V vs. Al. However, in the case of using ionic liquid, sodium (and not aluminium) is reversibly (de)inserted [23]. The results demonstrate that NVP is promising as electrode for rechargeable aluminium batteries, and that the electrolyte solution strongly influence on the electrochemical reaction.