Electrochemical Properties of Monoclinic NaMnO2

TLDR

Monoclinic α‑NaMnO₂ is re‑investigated electrochemically as a positive electrode material for sodium‑ion batteries. About 0.85 Na can be deintercalated from NaMnO₂ and 0.8 Na can be re‑intercalated during potentiostatic intermittent charge and discharge. Galvanostatic cycling between 2.0 V and 3.8 V yields 185 mAh g⁻¹ discharge capacity in the first cycle at C/10, dropping to 132 mAh g⁻¹ after 20 cycles, with pronounced hysteresis compared to lithium intercalation compounds and a notable difference from layered LiMnO₂ upon alkali removal.

Abstract

Monoclinic α- NaMnO2 is re-investigated electrochemically as a positive electrode material for sodium ion batteries. About 0.85 Na can be deintercalated from NaMnO2 and 0.8 Na be intercalated back during potentiostatical intermittent charge and discharge. Galvanostatical cycling between 2.0 V and 3.8 V gives 185 mAh/g discharge capacity for the first cycle at C/10 rate and 132 mAh/g remains after 20 cycles. Charge and discharge curves are significantly different indicating more hysteresis than is typical for lithium intercalation compounds. We also explain the remarkable difference between layered LiMnO2 and NaMnO2 upon alkali removal.