Exploring Battery Materials for Ca Batteries

Abstract

Rechargeable calcium (Ca) batteries have the prospects of high energy, low-cost and sustainability. Ca metal has a low reduction potential of -2.9 V vs. NHE (close to that of lithium -3.0 V)) and a high capacity, and thus the voltage and energy density of Ca batteries is potentially comparable with lithium-ion batteries. However, divalent Ca-ions and reactive Ca metal strongly interact with cathode materials and electrolyte solutions, leading to high charge-transfer barriers at the electrode-electrolyte interfaces and consequently low electrochemical performance. Herein, we will present the recent progress in the development of stable calcium tetrakis(hexafluoroisopropyloxy) borate Ca[B(hfip)4]2 (hfip = CH(CF3)2) electrolytes and the search for suitable cathode materials. We will discuss the interfacial properties of Ca anodes in liquid electrolytes and the chemistry of sulfur conversion electrodes in Ca batteries. References Li, O. Fuhr, M. Fichtner, Z. Zhao-Karger, Towards stable and efficient electrolytes for room-temperature rechargeable calcium batteries.Energy Environ. Sci. 12, 3496 (2019).Li, Z. M. Fichtner, Z. Zhao-Karger, Rechargeable Calcium–Sulfur Batteries Enabled by an Efficient Borate-Based Electrolyte. Small 16, 1–6 (2020).Zhao-Karger, Y. Xiu, Z. Li, A. Reupert, T. Smok, M. Fichtner, Calcium-tin alloys as anodes for rechargeable non-aqueous calcium-ion batteries at room temperature, Nature Comm. 13, 3849 (2022).