Long-Cycle-Life Calcium Battery with a High-Capacity Conversion Cathode Enabled by a Ca²⁺/Li⁺ Hybrid Electrolyte

Abstract

Calcium (Ca) batteries represent an attractive option for electrochemical energy storage due to physicochemical and economic reasons. The standard reduction potential of Ca (−2.87 V) is close to Li and promises a wide voltage window for Ca full batteries, while the high abundance of Ca in the earth's crust implicates low material costs. However, the development of Ca batteries is currently hindered by technical issues such as the lack of compatible electrolytes for reversible Ca 2+ plating/stripping and high-capacity cathodes with fast kinetics. Herein, we employed FeS 2 as a conversion cathode material and combined it with a Li + /Ca 2+ hybrid electrolyte for Ca batteries. We demonstrate that Li + ions ensured reversible Ca 2+ plating/ stripping on the Ca metal anode with a small overpotential. At the same time, they enable the conversion of FeS 2 , offering high discharge capacity. As a result, the Ca/FeS 2 cell demonstrated an excellent long-term cycling performance with a high discharge capacity of 303 mAh g −1 over 200 cycles. Even though the practical application of such an approach is questionable due to the high quantity of electrolytes, we believe that our scientific findings still provide new directions for studying Ca batteries with long-term cycling.

The effect of the pyrolysis temperature and biomass type on the biocarbons characteristics

“…[91] We expect that these ions are either trapped in the carbon material or released to the electrolyte and act as a charge carrier together with Li + -ions as in dual-ion batteries. [92,93] Since specific capacity of Ca-, Mgbatteries and dual-ion batteries with carbon electrodes do not reach theoretical capacity of graphite even at high concentration of Ca 2 + and Mg 2 + ions, their contribution to electrochemical characteristics of the materials presented in this work is considered insignificant.…”

Calcium Metal Batteries with Long Cycle Life Using a Hydride‐Based Electrolyte and Copper Sulfide Electrode

“…[25] In addition, Meng et al further developed a full cell using a FeS 2 cathode and a Ca metal anode that exhibited a capacity of 303 mAh g −1 at 200 cycles. [26] Although these electrolytes were compatible with Ca metal, the voltage window in the oxidative direction was as narrow as 2.4 V versus Ca 2+ /Ca because of the reducing nature of BH 4 anions. [27] A new hydride-type electrolyte-Ca(CB 11 H 12 ) 2 in dimethoxyethane/tetrahydrofuran (DME/THF)-was recently shown to exhibit a wide electrochemical potential window (up to 4 V vs Ca 2+ /Ca) and high conductivity (4 mS cm −1 ), in addition to supporting reversible Ca metal plating/stripping at room temperature.…”

A Structurally Flexible Halide Solid Electrolyte with High Ionic Conductivity and Air Processability

“…[ 9 ] The exponential growth in the cost of LIB raw materials has increased the scope for realizing batteries beyond lithium systems, such as Na‐ion [ 10 ] or multivalent/anion shuttle‐based batteries. [ 11 ] Anionic batteries solely depend on the charge transfer via anionic shuttle, originating from halide‐based electrode materials. In particular, chloride‐ion batteries (CIBs) attracted increasing interest, in the recent years, due to their high theoretical energy densities and the abundance of chloride‐based materials.…”