Alluaudite LiMnPO4: a new Mn-based positive electrode for Li rechargeable batteries

Abstract

A novel, Na-pillared LiMnPO₄ (Li_0.78Na_0.22MnPO₄) with an alluaudite structure is successfully prepared for the first time and proposed as a new positive electrode for Li rechargeable batteries. Approximately 0.8 Li⁺ ions are reversibly extracted from and reinserted into LiMnPO₄via Mn²⁺/Mn³⁺ redox reactions. The alluaudite LiMnPO₄ (a-LiMnPO₄) structure is sufficiently robust during repeated Li extraction/insertion such that ∼92% of the initial capacity is retained after 50 charge/discharge cycles. An ex situ XRD study of the electrochemical cell during cycling indicates that Li de/intercalation in alluaudite LiMnPO₄ occurs via the one-phase (solid–solution) reaction instead of the two-phase reaction observed in olivine LiMnPO₄.