Engineering Lithium Metal Surface to Enable Long-Term Cycling with Carbonate-Based Electrolytes

Abstract

The continued commercialization of electric vehicles in the transportation industry relies on developing high energy density batteries capable of long cycle life. Of all battery anode materials being studied, lithium (Li) metal affords the highest theoretical capacity (3,860 mAh/g) and lowest electrochemical potential (-3.04 C vs SHE) which offers the highest specific energy density. While Li-ion batteries are capable of delivering energy densities of 400-600 Wh/kg-1, the development of Li-S and Li-air batteries may boost this number to ~650 and ~950 Wh/kg-1, respectively. However, significant progress towards the passivation of Li metal anodes must occur before any of the anode’s potential can fully be realized. Issues with Li dendrite formation, anode volume expansion and continual SEI buildup often result in significant safety concern and poor cycle life of Li metal batteries. To circumvent these problems the use of electrolyte additives, high salt concentration electrolytes and the formation of Li metal anode interfaces have been studied. However, the intrinsic high reactivity between Li metal with conventional Li ion electrolyte (organic carbonated-based solvents) makes it extremely difficult to overcome these problems. To this end, Wildcat Discovery Technologies has developed both in situ and ex situ surface passivation method for Li metal to significantly boost the cycling performance of Li metal batteries. Thanks to Wildcat proprietary high-throughput technology, we are able to screen numerous passivation materials in combination with a variety of electrolyte compositions. As a result, we found several protection layers of the Li metal anode surface that showed significant improvement on cycling even at 0.9mA/cm2 charging current.