Prolonged cycle life for Li4Ti5O12//[Li3V2(PO4)3/multiwalled carbon nanotubes] full cell configuration via electrochemical preconditioning

Abstract

Full cells consisting of nanocrystalline Li3V2(PO4)3 (LVP) positive and standard commercial Li4Ti5O12 (LTO) negative electrodes demonstrated outstanding cyclability: capacity retention of 77% over 10,000 cycles. We achieved this stable cycle performance by electrochemical preconditioning of LTO with Li prior to full-cell cycling. The strategy of Li preconditioning not only allows adjustment of the state of charge (SOC) between negative and positive electrodes, but also gives rise to the formation of a protective covering layer on the LTO surface. As we show, this covering layer plays an important role in preventing a key performance-limiting phenomenon—namely, the deposition of vanadium eluted from LVP onto LTO, which degrades the coulombic efficiency of Li+ intercalation/ deintercalation into LTO crystals—yielding minimal SOC shifts and stable full-cell cycling.