A β-VOPO4/ε-VOPO4 composite Li-ion battery cathode

•We show that vanadyl phosphate can intercalate more than one lithium.•We show that the beta phase enhances the cycling capability of the e-phase.•We show excellent capacity retention over more than 750 cycles.•We determine the lithium diffusion coefficient in the composite.

VOPO4 is an example of a Li-ion battery cathode that can achieve over 300 Ah/kg when two Li-ions are intercalated. A two phase β-VOPO4/ε-VOPO4 composite was found to improve the cycling capacity of ε-VOPO4 from tetragonal H2VOPO4, particularly as the rate is increased. In the potential range of 2.0–4.5 V, this composite showed an initial electrochemical capacity of 208 mAh/g at 0.08 mA/cm2, 190 mAh/g at 0.16 mA/cm2, and 160 mAh/g at 0.41 mA/cm2.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide