High-performance Electrolytes for Li-CO2 Batteries

Abstract

Global climate change caused by the rapid increase of carbon dioxide (CO2) emissions has stimulated intensive research on how to achieve CO2 conversion and utilization with high efficiency and low cost. Transformation of CO2 into other chemicals, accompanied by an additional energy input and possible environmental pollution, struggles to fully meet eco-efficient and environmentally sustainable demand. Rechargeable Li-CO2 batteries with high discharge potential (2.80 V vs. Li+/Li) and theoretical energy density (1876 Wh kg-1), based on the reversible redox reaction of 3CO2 + 4Li+ + 4e- ↔ 2Li2CO3 + C, provide a win-win solution to carbon neutrality and high-energy-density storage systems. In addition, it has been projected by NASA in the field of space exploration that uptake of Li-CO2 batteries would enable significant weight and cost savings for Mars exploration missions because 96% of the Martian atmosphere is CO2.Because of the sluggish CO2 reaction kinetics, however, and the presence of highly reactive *CO22- radicals during discharge, Li-CO2 batteries currently suffer from huge polarization potential, unstable electrode/electrolyte interfaces, and poor cyclability. Most previous efforts have been focused on bifunctional catalyst design for cathodes to reduce battery overpotential and protect lithium anode/cathode protection through electrolyte additives. Even so, the critical role of anions/solvents in the formation of a robust solid electrolyte interphase (SEI) layer on cathodes and the solvation structure have never been investigated.