Improved electrochemical property of nanoparticle polyoxovanadate K7NiV13O38 as cathode material for lithium battery

Molecular cluster ion compound K7NiV13O38 (KNiV) has been studied as a novel cathode material for lithium ion battery. The nanoparticles are prepared by a simple re-crystallization method adding different volumes of acetone to the water solution containing the dissolved KNiV. The KNiV re-crystallized from water/acetone ratio of 1:5 shows the most uniform particle size distribution and the smallest particles with thickness of ~100 nm and width of ~150 nm. The nanoparticle KNiV shows significant improvement in initial discharge capacity and capacity retention after 50 cycles compared to the as-prepared micro-sized particles at various current densities. Ex situ XRD patterns demonstrate that the discharge–charge process proceeds with amorphous KNiV, which is independent from the crystal structure. Ex situ FT-IR spectra indicate that [NiV13O38]7− cluster ion is stable and reacts reversibly with lithium ion in the discharge–charge process.