Long Life Fully Reversible Lithium-CO2 Battery

Abstract

Although far less studied, lithium-CO2 (Li-CO2) batteries are attractive energy storage systems for fulfilling the demand for the future large-scale applications such as electric vehicles and grid systems due to their higher specific energy density (~1876 Wh/kg) compared to those of commonly used lithium-ion (~265 Wh/kg) and lead-acid (~30-40 Wh/kg) batteries. However, the major challenges with these batteries are the low cyclability and poor reversibility of discharge products (e.g., Li2CO3 and carbon) during the battery cycling. An ideal system must operate in carbon neutral conditions in order to reversibly balance the electrochemical reactions during discharge and charge processes. In this work, using molybdenum disulfide nanoflakes as a cathode catalyst combined with an ionic liquid and dimethyl sulfoxide hybrid electrolyte, we have obtained a Li-CO2 battery with a long cycle life while maintaining a carbon neutrality in the system. The battery shows a superior cycle life of 500 for a fixed 500 mAh/g capacity per cycle and a remarkable deep discharge capacity of 60,000 mAh/g, which are by far the best cycling stability and highest capacity reported in Li-CO2 batteries, respectively. The presented Li-CO2 battery system demonstrates for the first time that C-O bond making and breaking chemical transformations can be used in energy storage systems with a long cycle life, in addition to the widely studied alkali metal (Li, Na, K) – oxygen bond making and breaking transformations. Theoretical calculations are used to provide insight into the reaction mechanisms for the reversible formation and decomposition of the products during the discharge and charge processes. The achievement of a reversible, long cycle life Li-CO2 battery helps to improve Li-CO2 chemical performance and energy storage systems.