Doping-induced memory effect in Li-ion batteries: the case of Al-doped Li4Ti5O12.

In Li-ion batteries (LIBs), a memory effect has been revealed in two-phase electrode materials such as olivine LiFePO4 and anatase TiO2, which complicates the two-phase transition and influences the estimation of the state of charge. Practical electrode materials are usually optimized by the element doping strategy, however, its impact on the memory effect has not been reported yet. Here we firstly present the doping-induced memory effect in LIBs. Pristine Li4Ti5O12 is free from the memory effect, while a distinct memory effect could be induced by Al-doping. After being discharged to a lower cutoff potential, Al-doped Li4Ti5O12 exhibits poorer electrochemical kinetics, delivering a larger overpotential during the charging process. This dependence of the overpotential on the discharging cutoff leads to the memory effect in Al-doped Li4Ti5O12. Our discovery emphasizes the impact of element doping on the memory effect of electrode materials, and thus has implications for battery design.