Surface-Engineered Li4Ti5O12 Nanostructures for High-Power Li-Ion Batteries

Materials with high-power charge–discharge capabilities are of interest to overcome the power limitations of conventional Li-ion batteries.In this study,a unique solvothermal synthesis of Li4Ti5O12 nanoparticles is proposed by using an off-stoichiometric precursor ratio.A Li-deficient off-stoichiometry leads to the coexistence of phaseseparated crystalline nanoparticles of Li4Ti5O12 and TiO2 exhibiting reasonable high-rate performances.However,after the solvothermal process,an extended aging of the hydrolyzed solution leads to the formation of a Li4Ti5O12 nanoplate-like structure with a self-assembled disordered surface layer without crystalline TiO2.The Li4Ti5O12 nanoplates with the disordered surface layer deliver ultrahighrate performances for both charging and discharging in the range of 50–300C and reversible capacities of 156 and 113 mAh g−1 at these two rates,respectively.Furthermore,the electrode exhibits an ultrahigh-charging-rate capability up to 1200C(60 mAh g−1;discharge limited to 100C).Unlike previously reported high-rate half cells,we demonstrate a high-power Li-ion battery by coupling Li4Ti5O12 with a high-rate LiMn2O4 cathode.The full cell exhibits ultrafast charging/discharging for 140 and 12 s while retaining 97 and 66% of the anode theoretical capacity,respectively.Room-(25℃),low-(−10℃),and high-(55℃)temperature cycling data show the wide temperature operation range of the cell at a high rate of 100C.

Materials with high-power charge–discharge capabilities are of interest to overcome the power limitations of conventional Li-ion batteries. In this study, a unique solvothermal synthesis of Li4Ti5O12 nanoparticles is proposed by using an o-stoichiometric precursor ratio. A Li-deficient o-stoichiometry leads to the coexistence of phaseseparated crystalline nanoparticles of Li4Ti5O12and TiO2 exhibiting reasonable high-rate performances. However, after the solvothermal process, an extended aging of the hydrolyzed solution leads to the formation of a Li4Ti5O12nanoplate-like structure with a self-assembled disordered surface layer without crystalline TiO2. The Li4Ti5O12nanoplates with the disordered surface layer deliver ultrahighrate performances for both charging and discharging in the range of 50–300 C and reversible capacitiesof 156 and 113 m Ah g-1 at these two rates, respectively. Furthermore, the electrode exhibits an ultrahigh-charging-rate capability up to 1200 C(60 m Ah g-1; discharge limited to 100 C). Unlike previously reported high-rate half cells, we demonstrate a high-power Li-ion battery by coupling Li4Ti5O12with a high-rate Li Mn2 O4 cathode. The full cell exhibits ultrafast charging/discharging for 140 and 12 s while retaining 97 and 66% of the anode theoretical capacity, respectively. Room-（25 °C）, low-（-10 °C）, and high-（55 °C） temperature cycling data show the wide temperature operation range of the cell at a high rate of 100 C.