Phase transition observed in potential–composition profiles of LixMn2O4

Abstract

Open circuit voltage (OCV) profiles of spinel type lithium manganese oxide Li x Mn 2 O 4 ( x ≤1) have been recorded at several temperatures ( 243 K ≤T≤323 K ) using a single three-electrode glass cell. Deintercalation of Li ions from Li x Mn 2 O 4 has been carried out at low temperature (243 K), and then OCV profile has been measured at both the processes of raising and descending temperatures on each state of lithium content ( x ). Quasi-equilibrium potential profiles above room temperature ( 298 K ≤T ), which are results of continuous measurements by first charge, overlap with OCV profiles in the process of raising temperature well. However, around x =0.5, quasi-equilibrium potential profiles and OCV profiles do not overlap at low temperature ( T ≤278 K). This result indicates that the low-temperature phase at x =0.5 in Li x Mn 2 O 4 is very sensitive to temperature change. Temperature dependence of OCV profiles in the process of descending temperature corresponds to a simulation based on assumption that distribution of Li ions is disordered in Li x Mn 2 O 4 (0.5≤ x <1).