The effect of Al substitution on the lithium insertion properties of lithium vanadium fluorophosphate, LiVPO4F

The structural and electrochemical insertion properties of LiV1−xAlxPO4F (x = 0.00, 0.25 and 0.50) phases are presented. XRD data reveal that the basic triclinic amblygonite structure was retained for all experimental compositions. Although the material specific capacities decreased almost linearly with aluminum content, the substituted phases revealed some intriguing properties that appear to be ‘tunable’ within the compositional range under investigation. The main beneficial attributes include low voltage polarization, high operating voltage and comparatively low capacity fade on cycling. In all cases the observed lithium insertion behavior was restricted to the V3+/4+ redox couple.