Reversible Calcium Plating and Stripping at Room Temperature Using a Borate Salt

Abstract

Interest has rekindled in reversible calcium plating and stripping, renewing hopes for the development of Ca-ion batteries. However, the development of an electrolyte that operates at room temperature and is stable to oxidation at practical potentials remains a significant barrier. Here we report the synthesis and crystal structure of a new fluorinated alkoxyborate Ca(B(Ohfip) 4 ) 2 •4DME salt. Reversible plating and the dissolution of calcium from pure solutions of this salt in dimethoxyethane are demonstrated at 25 °C with capacities of 1 mAh cm −2 at a rate of 0.5 mA cm −2 over 30−40 cycles, with an anodic stability of >4.1 V vs Ca/Ca 2+ (and up to 4.9 V in dimethyltriflamide). The dominant product is calcium, accompanied by CaF 2 that forms by the reduction of the fluorinated anion. Whereas the cathodic stability requires improvement, this work shows that facile calcium plating and stripping at room temperature can be achieved using bulk electrodes.

The ORR in Ca2+ Containing DMSO: Reaction Mechanism, Electrode Surface Characterization and Redox Mediation

“…Taking the consumption of oxygen and the electrons flowing into the reduction of DBBQ into account, one can calculate the expected ratio between transferred electrons per oxygen molecule on the basis of the postulated reactions. This results in 2 e -/O2 for reactions (4) and (5) and 1 e -/O2 for reaction (6). For reaction (6) a following disproportionation reaction of the superoxide is plausible as we also showed in the beginning of this paper (see Figure 5).…”

“…Another problem for lithium technology is the lack of the resource lithium and the water consuming mining (3). Thefore Calcium, being the fifth most abundant metal on earth, combines a high abundance with a competitive volumetric capacity of 2072 mAh⋅cm -3 (4,5) and thus, is a promising candidate as anode material in future battery applications. Early studies, however, showed the difficulties of Ca plating/stripping (6).…”

“…Early studies, however, showed the difficulties of Ca plating/stripping (6). Fortunately, more recent studies revealed electrochemical systems in which the Ca plating/stripping becomes accessible (4,5,7,8).…”

Wiederaufladbare Calcium‐Batterien

“…Abdruck mit Genehmigung aus Lit. . Copyright Royal Chemical Society und American Chemical Society (2019).…”

Appraisal of calcium ferrites as cathodes for calcium rechargeable batteries: DFT, synthesis, characterization and electrochemistry of Ca4Fe9O17

“…1,2 Advances in the development of such batteries are intricate due to the lack of competitive cathode materials and electrolytes. 3,4 While recent findings demonstrate the feasibility of Ca anode operation using different electrolytes, [5][6][7][8] the identification of suitable cathode materials has been facing several roadblocks. 4,9,10 Limited reversible electrochemical Ca intercalation has been reported for a handful of compounds 4 (V 2 O 5 , 11 TiS 2 , 12 MoO 3 , 13 Ca 0.5 CoO 2 , 14 and manganese hexacyanoferrate 1 ), all of them showing poor cycling, if any.…”