Hollow Keggin-Type Hybrid Polyoxometalate as a Stable Redox Electrode for Safe and Fast-Charging Lithium-Ion Batteries

The preparation of high-capacity and fast-charging electrode materials to provide more efficient and stable Li+ storage sites in lithium-ion batteries (LIBs) remains a key challenge for room-temperature LIBs. Herein, the first molybdenum–tungsten hybrid polyoxometalate [MoIV6WVI6O28(OH)6py6]·2[H2N(CH3)2]·6.5H2O (MoIV6W6) is applied as an electrode material for LIBs, which has a completely different mechanism from previously reported compounds. Meanwhile, a novel synthetic route was employed to prepare crystals with a higher yield and free of impurities. Using MoIV6W6 as the anode material, a reversible capacity of 1134 mAh g–1 (2 A g–1) is achieved after 700 cycles with excellent cycling stability and rate performance. The XPS and XRD results indicate that the stable structure of MoIV6W6 and the highly reversible valence changes of Mo and W during charging and discharging contributed to their outstanding performance. In addition, the MoIV6W6 electrode exhibits a low volume expansion of 3.5% after 1000 cycles, contributing to the safety and cycle life of LIBs. This work not only demonstrates the potential of the hollow MoIV6W6 cluster as a high-performance LIB anode material but also provides a new strategy for the rational design of electrode materials for POMs in advanced energy storage systems.