Reconfiguring Quinone Cathodes via Transition Metal Coordination for Advanced Calcium Batteries

Calcium-ion batteries (CIBs) are promising for next-generation energy storage. However, their development is hindered by the lack of high-performance cathode materials. Organic carbonyl compounds possess structural flexibility and redox activity, yet their overall energy density remains fundamentally constrained. Here, we report a molecular engineering strategy to prepare metal (Cu and Ni)-coordinated quinone cathodes. The incorporation of transition-metal centers reconfigures the conjugated molecular framework, simultaneously enhancing reversible capacity and operating voltage. The optimized cathodes deliver reversible capacities of up to 203 mAh g–1 at an average voltage of ∼3.1 V vs Ca2+/Ca, corresponding to an energy density exceeding 600 Wh kg–1. Mechanistic investigations based on in situ characterizations and theoretical calculations reveal a bipolar charge-storage mechanism involving Ca2+ coordination with the carbonyl and imine sites during discharge and TFSI– storage at high charging potentials. This metal-coordination strategy provides a promising strategy for developing high-energy multivalent battery systems.