Unveiling the Electrocatalytic Activity of 1T′-MoSe<sub>2</sub> on Lithium-Polysulfide Conversion Reactions
Kiran Mahankali, Sundeep Varma Gottumukkala, Nirul Masurkar, Naresh Kumar Thangavel, Rahul Jayan, Abdulrazzag Sawas, Sudhan Nagarajan, Md Mahbubul Islam, Leela Mohana Reddy Arava
Abstract
The dissolution of intermediate lithium polysulfides (LiPS) into an electrolyte and their shuttling between the electrodes have been the primary bottlenecks for the commercialization of high-energy density lithium–sulfur (Li–S) batteries. While several two-dimensional (2D) materials have been deployed in recent years to mitigate these issues, their activity is strictly restricted to their edge-plane-based active sites. Herein, for the first time, we have explored a phase transformation phenomenon in a 2D material to enhance the number of active sites and electrocatalytic activity toward LiPS redox reactions. Detailed theoretical calculations demonstrate that phase transformation from the 2H to 1T′ phase in a MoSe2 material activates the basal planes that allow for LiPS adsorption. The corresponding transformation mechanism and LiPS adsorption capabilities of the as-formed 1T′-MoSe2 were elucidated experimentally using microscopic and spectroscopic techniques. Further, the electrochemical evaluation of phase-transformed MoSe2 revealed its strong electrocatalytic activity toward LiPS reduction and their oxidation reactions. The 1T′-MoSe2-based cathode hosts for sulfur later provide a superior cycling performance of over 250 cycles with a capacity loss of only 0.15% per cycle along with an excellent Coulombic efficiency of 99.6%.