Robust pseudo-capacitive Li-I2 battery enabled by catalytic, adsorptive N-doped graphene interlayer

Abstract

Vehicle electrification and stationary energy storage urgently demand improved battery systems with high specific capacity and power density. Herein, we design a novel Li-I2 energy storage system by inserting a nitrogen-doped graphene interlayer between the cathode and the separator. This interlayer allows the electrochemical reaction and pseudo-capacitive faradaic reaction to occur at the same reaction sites and helps the resultant battery achieve high electrochemical performance. The Li-I2 battery constructed with the interlayer can achieve remarkable specific capacity (231.0 mAh g−1 at 2 C), excellent rate capability (up to 100 C), and ultra-long cycling life (5000 cycles). Such an outstanding performance can be attributed to the tri-functions of the interlayer which are to retain the iodine species (such as I-, I2, I3-) in the cathode region to alleviate the shuttle phenomenon, utilise the iodine species to afford remarkable pseudo-capacitive effect for energy storage, and accelerate the kinetic process of active materials to present an excellent rate performance owing to the catalytic effect of nitrogen doping. The concept of the tri-functional interlayer suggests a promising direction for the design of robust and high performance rechargeable Li-I2 batteries.