Manganese-Based Tunnel and Layered Oxide Cathodes for Secondary Alkali-Ion Batteries

Abstract

Designing new cathode materials remains crucial in developing (post) Li-ion batteries. Mn-based oxide cathodes have received wide attention due to their sustainable nature, low cost, elemental abundance, structural diversity/polymorphism, and rich oxidation states (2+ to 7+), offering tunable redox potential [1]. Here, we have investigated different oxide-based cathode insertion compounds for secondary metal-ion batteries.i) We have demonstrated tunnel-type sodium insertion material Na44MnO2(NMO) as an intercalation host for Li-ion and K-ion batteries. The solution combustion synthesized Na0.44MnO2 assuming an orthorhombic structure (space group Pbam), exhibited rod-like morphology. After electrochemical ion exchange from NMO, we obtained Na0.11K0.27MnO2 (NKMO) and Na0.18Li0.51MnO2 (NLMO) cathodes for K-ion batteries and Li-ion batteries, respectively [2]. These new compositions, NKMO and NLMO, showed excellent cycling stability with capacities of ∼74 and 141 mAh g–1 (first cycle, C/20 current rate). The underlying mechanistic features concerning charge storage and structural modifications in these cathode compositions were probed by combining ex-situ structural, spectroscopy, and electrochemical tools [3].ii) Using composite formation, we have tried to improve the P2-type layered material. Here, the stable Na7(Li1/18Mn1/18Ni3/18Fe2/18χ1/18)O2–xNa2MoO4 biphasic composite was synthesized using Mo doping. Overall, the redox chemistry was investigated using various spectroscopy techniques to prove the net capacity resulted from both cationic and anionic redox reactions [4]. Keywords: energy storage; batteries; cathode; manganese oxides; intercalation; doping