High Performance Aqueous and Nonaqueous Ca-Ion Cathodes Based on Fused-Ring Aromatic Carbonyl Compounds

Calcium-based battery systems are promising postlithium candidates; however, only a few amenable calcium materials were reported in nonaqueous electrolytes. Here, reversible storage of Ca2+ ions in aqueous and nonaqueous electrolyte solutions is shown for crystalline 3,4,9,10-perylene tetracarboxylic dianhydride. The carbonyl functional groups and the π-electrons constitute redox centers, which can reversibly interact with divalent ions. This phenomenon was clearly uncovered by combined electrochemistry, Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and ex situ X-ray diffraction analyses. Very promising calcium storage performances are shown with a highly reversible capacity around ∼158 mAh g-1 at a rate of 10 mA g-1 with an average voltage of ∼2.3 V band sufficient capacity retention in saturated Ca(ClO4)2 in propylene carbonate solutions. This saturated electrolyte system prevents the usual material's dissolution problems and provides a highly active interfacial reaction with the organic cathode materials. Consequently, these positive contributions offer much better electrochemical performance in terms of higher specific capacity, higher rate capability, and stability during prolonged cycling.