A Polyoxovanadate-Based Metal-Organic Framework Unlocks the Potential for Advanced Calcium-Ion Storage

Abstract

Calcium-ion batteries (CIBs) offer great potential due to their high capacity and natural abundance of calcium. Nevertheless, the large radius and high charge density of Ca²⁺ ions cause severe electrode degradation and sluggish kinetics, thus hindering their electrochemical performance. Herein, an organic-inorganic hybrid composite ([Co₃(4-NH₂-trz)₆][V₆O₁₈]•3H₂O@GO, Co,V-POMOF) cathode is designed as an efficient cathode for CIBs. This design synergistically integrates multi-electron redox-active polyoxometalates (POMs) with a stable Co-MOF framework, while GO serves as a conductive and volume-buffering agent. As a result, the composite delivers a high capacity of 320.45 mAh g^-1 at 50 mA g^-1 after 50 cycles along with extended cycling stability, demonstrating an effective strategy for designing advanced divalent/trivalent battery cathodes.