3D-Structured Polyoxometalate Microcrystals with Enhanced Rate Capability and Cycle Stability for Lithium-Ion Storage.

The unsatisfactory rate capability and poor cycle stability are two major obstacles for polyoxometalates (POMs) in lithium-ion storage. On the other hand, how to endow POMs with 3D macrostructures for further practice is a challenge. To this end, a facile hydrothermal strategy was practiced to fabricate CoWO(OH)(HO) microcrystals or CoWO aggregates onto the foamed substrate (denoted as CoW-POM and CoW-Salt, respectively). Integrating the extraordinary redox stability and lattice deformability of POMs with the excellent volume accommodation, the as-prepared CoW-POM presents an extraordinary better electrochemical performance (specific capacity, rate capability, and cycle life) than that of CoW-Salt. In detail, the CoW-POM can deliver a reversible capacity of 737.8 mA h g at the current density of 0.1 A g and provide a capacity retention of 90.1% even after 100 cycles. This work not only promotes the application of POMs in energy storage and conversion but also guides an effect methodology to endow POMs with 3D structures.