Mechanistic insights of Li+ diffusion within doped LiFePO4 from Muon Spectroscopy

The Li+ ion diffusion characteristics of V- and Nb-doped LiFePO4 were examined with respect to undoped LiFePO4 using muon spectroscopy (mu SR) as a local probe. As little difference in diffusion coefficient between the pure and doped samples was observed, offering D-Li values in the range 1.8-2.3 x 10(-10) cm(2) s(-1), this implied the improvement in electrochemical performance observed within doped LiFePO4 was not a result of increased local Li+ diffusion. This unexpected observation was made possible with the mu SR technique, which can measure Li+ self-diffusion within LiFePO4, and therefore negated the effect of the LiFePO4 two-phase delithiation mechanism, which has previously prevented accurate Li+ diffusion comparison between the doped and undoped materials. Therefore, the authors suggest that mu SR is an excellent technique for analysing materials on a local scale to elucidate the effects of dopants on solid-state diffusion comparison between the doped and undoped materials. Therefore, the authors suggest that mu SR is an excellent technique for analysing materials on a local scale to elucidate the effects of dopants on solid-state diffusion behaviour.