Exploring Calcium Manganese Oxide as a Promising Cathode Material for Calcium-Ion Batteries

Abstract

The dependence on lithium for the energy needs of the world, coupled with its scarcity, has prompted the exploration of postlithium alternatives. Calcium-ion batteries are one such possible alternative owing to their high energy density, similar reduction potential, and naturally higher abundance. A critical gap in calcium-ion batteries is the lack of suitable cathodes for intercalating calcium at high voltages and capacities while also maintaining structural stability. Transition metal oxide postspinels have been identified as having crystal structures that can provide low migration barriers, high voltages, and facile transport pathways for calcium ions and thus can serve as cathodes for calcium-ion batteries. However, experimental validation of transition metal oxide postspinel compounds for calcium ion conduction remains unexplored. In this work, calcium manganese oxide (CaMn2O4) in the postspinel phase is explored as an intercalation cathode for calcium-ion batteries. CaMn2O4 is first synthesized via solid-state synthesis, and the phase is verified with X-ray diffraction (XRD). The redox activity of the cathode is investigated with cyclic voltammetry (CV) and galvanostatic (GS) cycling, identifying oxidation potentials at 0.2 and 0.5 V and a broad insertion potential at −1.5 V. CaMn2O4 can cycle at a capacity of 52 mAh/g at a rate of C/33, and calcium cycling is verified with energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) and modeled with density functional theory (DFT) simulations. The results from the investigation concluded that CaMn2O4 is a promising cathode for calcium-ion batteries.

Fluoride frameworks as potential calcium battery cathodes

“…Previous studies have employed both experimental and computational techniques that have explored select chemistries as possible CB cathodes. The set of inorganic cathodes that have been reported with Ca so far include CaMo 6 X 8 (X = S, Se, or Te), 21 VOPO 4 ·2H 2 O, 22 Ca x V 2 O 5 , 23–27 CaV 2 O 4 , 28,29 CaMn 2 O 4 , 30 MoO 3 , 31–33 NH 4 V 4 O 10 , 34 CaCo 2 O 4 , 35,36 NaFePO 4 F, 37 TiS 2 , 38 CaV 6 O 16 ·2.8H 2 O, 39 Prussian-blue analogues (PBAs), 40–44 and other polyanionic frameworks. 45–48 However, only a select few of these compounds show reasonable electrochemical performance, with most suffering from inadequate cycling stability, poor Ca-ion diffusion, and large volume changes during charge/discharge.…”

“…Recently, Chando et al 30 explored the post-spinel phase of CaMn 2 O 4 as a CB-cathode candidate using both experiments and density functional theory (DFT 50,51 ) calculations and reported a low cycling capacity of 52 mA h g −1 at a rate of C/33. Prabakar et al 26 used a water-free β-phase Ca 0.14 V 2 O 5 as a Ca-cathode and reported a reversible capacity of ∼247 mA h g −1 .…”

Calcium Cosalt Addition to Alter the Cation Solvation Structure and Enhance the Ca Metal Anode Performance

“…To meet society’s growing needs for renewable energy storage, novel battery chemistries with higher energy density and lower cost than Li-ion batteries need to be developed. , Ca metal batteries have been proposed as alternatives to Li-ion batteries due to the greater crustal abundance (41,500 mg/kg for Ca vs 20 mg/kg for Li) and anode capacity (1337 mAh/g for Ca metal anodes vs 372 mAh/g for Li/C 6 anodes). Despite these advantages, development of Ca metal batteries has been limited. ,− …”