Exploring the performance of carbonate and ether-based electrolytes for anode-free lithium metal batteries operating under various conditions

Abstract

Abstract An anode-free lithium metal battery (AFLMB) configuration can be used to develop electrolytes for wide-temperature applications. The charge/discharge performance of an electrolyte consisting of lithium hexafluorophosphate (LiPF6) in a mixture of fluoroethylene carbonate (FEC), 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), and ethyl methyl carbonate (EMC) has been is reported as an electrolyte for lithium metal batteries. It has a good passivating capability and wide electrochemical windows relative to the commercial electrolyte. Conversely, its lower ionic conductivity and high viscosity impede practical application. Hence, an electrolyte of 1\xa0M LiPF6 in EA/FEC/TTE/EMC (2:1:5:2 by vol.) is developed by adding a quaternary solvent of ethyl acetate (EA). The electrolyte exhibits a lower viscosity and higher ionic conductivity than 1\xa0M LiPF6 in FEC/TTE/EMC (3:5:2 by vol.). At 0\xa0°C, 1\xa0M LiPF6 in EA/FEC/TTE/EMC (2:1:5:2 by vol.) provides capacity retention of 30 % and the average Coulombic efficiency (av. CE) of 95 % using the Cu||NMC111 after 40 cycles at a current density of 0.2\xa0mA/cm2. The synergy of higher ionic conductivity and formation of LiF layer in the developed electrolyte extends the service-temperature range of AFLMB. This study opens an avenue in developing low-temperature electrolytes using an AFLMB.