A stable high-power Na2Ti3O7/LiNi0.5Mn1.5O4 Li-ion hybrid energy storage device

Li-ion batteries (LIBs) are ubiquitous in mobile devices and increasingly popular for powering large-sized transportation applications. However, current LIBs are undesirable to drive the further penetration of electric vehicles due to insufficient kinetics (long charging time, limited power) and high cost. In the quest of high-power, affordable, and environmentally friendly energy storage, here we design a new type of hybrid device composed of a low-cost Na2Ti3O7 anode and a high-voltage LiNi0.5Mn1.5O4 cathode. For the first time, we investigated Na2Ti3O7 nanotubes as Li+ host, which exhibit superior rate performance due to the domination of Li+ capacitance (over 85%) in a safe potential window (1-3V vs. Li/Li+). Attributing to the synergy between the pseudo-capacitive anode and the fast Li+ intercalating cathode, the newly designed device delivers an extraordinary power density of 18631 W kg(-1) while maintaining an energy density of 85 W h kg(-1) based on total mass of cathode and anode materials. Such a combination of energy and power densities makes it exceptional compared to known LIBs and capacitors. The device also shows excellent capacity retention of 71% after 1000 cycles, highlighting the key advantages of this type of low-cost configuration towards scalable high-power energy storage application. (C) 2018 Published by Elsevier Ltd.