A Novel Calcium‐Ion Battery Based on Dual‐Carbon Configuration with High Working Voltage and Long Cycling Life

Rechargeable batteries based on multivalent cations (e.g., Mg(2+) and Al(3+)) have attracted increased interest in recent years because of the merits of natural abundance, low cost, good chemical safety, and larger capacity. Among these batteries, the Ca‐ion battery (CIB) shows attractive priority because Ca(2+) has the closest reduction potential (−2.87 V vs standard hydrogen electrode (SHE)), to that of Li (−3.04 V vs SHE), enabling a wide voltage window for the full battery. However, most Ca‐ion batteries have low working voltage (below 2 V), as well as poor cycling stability (less than 50 cycles). Here, a high‐performance Ca‐ion full battery with a novel dual‐carbon configuration design with low‐cost and environmentally friendly mesocarbon microbeads and expanded graphite as the anode and cathode, respectively, is reported. This Ca‐ion‐based dual‐carbon battery (Ca‐DCB) can work successfully in conventional carbonate electrolyte dissolving Ca(PF(6))(2), with a reversible discharge capacity of 66 mAh g(−1) at a current rate of 2 C and a high working voltage of 4.6 V. Moreover, the Ca‐DCB exhibits good cycling stability with a discharge capacity of 62 mAh g(−1) after 300 cycles with a high capacity retention of 94%, which is the best performance of the reported CIBs, suggesting it is a promising candidate for next‐generation energy storage devices.