Intrinsic factors affecting the catalytic activity of doped TiC as potential cathode in Li-O2 batteries

Abstract

First-principles calculations were performed to investigate the catalytic activity of LiO2 batteries based on TiC and X-doped TiC (X = B, N, Al, Si, and P) materials as potential cathode catalysts. Interfacial models of LixO2 (x = 4, 2, and 1) intermediates adsorbed on doped TiC surface were used to simulate the structural evolution during discharging/charging process. The catalytic activity was quantitatively assessed by specific ORR/OER overpotential, and some intrinsic factors affecting the catalytic activity of doped TiC were determined based on the structure-activity relationships established. The catalytic activity of doped TiC can be divided into two groups, wherein B-, N-, and P-doped TiC have better catalysis than Al- and Si-doped TiC. Among them, B-doped TiC displays the lowest ORR overpotential, suggesting that B-doped TiC has the best catalytic activity of ORR. The stronger (Li2O)2/Li2O2/LiO2 adsorption energy induces lower ORR and OER overpotentials. The stronger Li+ desorption energy attracts lower ORR overpotential, while the weaker O2 desorption energy induces lower OER overpotential. Consequently, adsorption energy of (Li2O)2/Li2O2/LiO2 and desorption energy of Li+/O2 are useful factors for characterizing the catalytic activity. These findings contribute to understand the doping effect on catalysis and provide insights into the screening and design of novel catalyst in LiO2 batteries.