Lithium intercalation into the polyoxovanadate K7MnV13O38 as cathode material of lithium ion batteries

• Nanosized polyoxovanadate K7MnV13O38 is easily prepared by simple re-crystallization.
• Nanosized KMV shows high discharge capacity, though its capacity retention is poor.
• The mixture of nanosize and microsize KMV shows high capacity retention.
• SEI formation on the cathode significantly influences cycle performance of KMV.

The polyoxovanadate K7MnV13O38 (KMV) has been studied as cathode material of lithium ion batteries. The nanosize particles show initial discharge capacities over 308 and 225 mAh g− 1 at current densities of 17 and 167 mA g− 1, respectively. However, the capacity fading of nanosize particles is notably high with increasing cycle number, particularly when cycling at high rate. An effective approach to reduce the capacity fading is to use a composite cathode consisting of a mixture of nanosize particles and microsize particles in the weight ratio of 1:1. This composite cathode exhibits excellent cycle performance with capacity retention over 97% after 50 cycles at both low rate and high rate.