Calcium Molybdenum Bronze as a Stable High-Capacity Cathode Material for Calcium-Ion Batteries

Abstract

Calcium-ion batteries (CIBs) are gaining increasing attention due to their theoretically high capacity, owing to the divalency of calcium, and low cost. However, only a few calcium insertion electrode materials are reported, and most of them exhibit low capacity or poor cyclability in nonaqueous electrolytes. Herein, we demonstrated high-performance calcium molybdenum bronze Ca0.13MoO3·(H2O)0.41 as a potential CIB cathode material at room temperature, with a reversible discharge capacity of 192 mAh g–1 at 86 mA g–1, an average voltage of 2.4 V (vs Ca/Ca2+), and excellent cyclability. This work provides the feasibility of developing high-capacity CIB cathode materials.

A Computational Study on the Ca2+ Solvation, Coordination Environment, and Mobility in Electrolytes for Calcium Ion Batteries

“…The two salts were selected based on their commercial availability, high solubility, and use in previous experimental work. 2,[35][36] Ca(BF4)2 has been excluded from our studies owing to its decomposition products being impermeable to calcium owing to CaF2 and carboxylates, 12 and its examination previously. 28 The solvents and their classes have been shown to be stable in previous theoretical and experimental work.…”

“…Overall, differences among the electrolytes may become more apparent with regards to solvation and desolvation during redox reactions. Identified favorable electrolytes herein such as ACN, THF and EC+PC Ca(TFSI)2 show good diffusivities and are notably used in current battery studies, [35][36][37][50][51] as well as THF and EC+PC, and even EC+EMC+DMC to enable redox activity at a calcium metal interface. 11-12, 14, 23, 25 Single solvents such as DMF, DEC, DMC, and EMC should also show good solubility and mobility, combined with possibly good desolvation to enable redox activity.…”

“…17,33 Other noncarbonates yield good electrolyte properties in calcium ion batteries. 26,34 Yet, as is the case for many of them, such as acetonitrile, [34][35][36] THF 24 and DMF, 26 complimentary theoretical studies are lacking. Ca(TFSI)2 and Ca(ClO4)2 are also understudied, despite the former showing one of the highest conductivities for the explored calcium salts and having been employed in battery studies, 26,35,37 and the latter appears to have been overlooked, perhaps owing to the low plating/stripping kinetics.…”

A Computational Study on the Ca2+ Solvation, Coordination Environment, and Mobility in Electrolytes for Calcium Ion Batteries

“…Overall, differences among the electrolytes may become more apparent with regards to solvation and desolvation during redox reactions. Identified favorable electrolytes herein such as ACN, THF and EC+PC with Ca(TFSI)2 show good diffusivities and are notably used in current battery studies, [35][36][37][50][51] as well as THF and EC+PC, and even EC+EMC+DMC to enable redox activity at a calcium metal interface. 11-12, 14, 23, 25 Single solvents such as DMF, DEC, DMC, and EMC should also show good solubility and mobility, combined with possibly good desolvation to enable redox activity.…”

Layered Iron Vanadate as a High-Capacity Cathode Material for Nonaqueous Calcium-Ion Batteries

“…In addition, no promising cathode materials have been developed yet, probably because of a lack of understanding regarding the unique calcium intercalation chemistry, despite the extensive research, including theoretical/computational studies [3]. The calcium-insertion materials in nonaqueous electrolytes reported so far include Prussian-blue analogues [10][11][12][13][14], CaCo 2 O 4 [15], NaFePO 4 F [16], NH 4 V 4 O 10 [17], α-MoO 3 [18], Ca x MoO 3 [19], TiS 2 [20], α-V 2 O 5 [21], CaMnO 3 [22], Mg 0.25 [24], NaV 2 (PO 4 ) 3 [25,26], and Ca 0.13 MoO 3 •(H 2 O) 0.41 [27]. Most of these materials exhibit low Coulombic efficiency, capacity, or cyclability in dried nonaqueous electrolytes.…”