Coordination-Tuned Layered Vanadium Oxide via Electroactive Organic Pre-Intercalation Enables High-Capacity, Long-Cycling Nonaqueous Calcium-Ion Batteries

Among multivalent energy-storage systems, calcium-ion batteries (CIBs) have emerged as promising candidates owing to calcium's low redox potential and natural abundance. However, their development is impeded by the scarcity of cathode materials capable of reversible Ca²⁺ storage with fast ion transport and structural stability. Here, we propose a rational intercalation-engineering strategy to construct an organic-inorganic hybrid cathode by introducing electroactive <i>meta</i>-benzoquinone (mBQ) into bilayered hydrated vanadium pentoxide, yielding a resulting material with a nominal composition of (mBQ)_0.07V₂O₅·0.2H₂O (mBQ-VO). The mBQ molecules act as interlayer pillars, expanding the spacing to 13.86 Å and providing open channels for Ca²⁺ diffusion, while simultaneously regulating the [VO₆] octahedral field to optimize V-O bonding and enhance ion kinetics, as explained by a "spring-like" lattice relaxation model. Additionally, mBQ serves as an extra redox-active site, improving both the capacity and reversibility. Benefiting from this synergistic structural and electronic design, mBQ-VO delivers a high capacity of ∼250 mAh g^-1 at 0.01 A g^-1, remarkable cycling stability with 81.5% retention after 4000 cycles, and low charge-transfer resistance (half that of V₂O₅·nH₂O). In addition, the combination of in situ X-ray diffraction (XRD) and <i>ex situ</i> X-ray photoelectron spectroscopy (XPS) analyses further confirm highly reversible Ca²⁺ intercalation with preserved structural integrity. This work demonstrates an effective strategy for designing hybrid cathodes with optimized ion dynamics and redox activity, offering guidance for the design of high-performance CIBs.