Lithium Metal Deposition and Stripping in Porous Hosts Coupled with Viscous Polymer Electrolytes

Abstract

High energy density rechargeable batteries are desired to meet global goals of increased use of renewable energy and vehicle electrification. Higher energy densities can be achieved by replacing graphite anodes with metal anodes. Among metal anode materials, lithium metal anodes are promising due to their high theoretical capacity and low reduction potential. However, obstacles such as dendrite growth and continuous electrolyte decomposition need to be addressed for successful commercialization of rechargeable batteries with lithium metal anodes. It is widely reported that porous 3D lithium metal hosts can mitigate dendrite growth by accommodating lithium deposition uniformly within the hosts during cycling. Continuous electrolyte decomposition can also be mitigated by replacing liquid electrolytes with solvent-free electrolytes. We incorporate both strategies in this work to address the critical issues described above by demonstrating lithium deposition/stripping cycling on 3D electrode hosts with viscous polymer electrolytes. First, lithium metal deposition/stripping cycling within non-conductive and conductive hosts were compared, where zinc oxide (ZnO) coated polyacrylonitrile (PAN) nanofibers was used as the non-conductive lithium metal host and ZnO coated copper nanowires were prepared as the conductive lithium metal host. The non-conductive host showed successful cycling of 5 mAh/cm2(25 µm thickness) of lithium metal without short circuiting. Further, deposition/stripping cycling with viscous star polymers (polystyrene-co-poly(polyethylene glycol) methyl ether acrylate (PS-co-PPEGMA)) and a linear oligomer polyethylene glycol dimethyl ether (PEGDME) were compared. The effects of the physical and electrochemical properties of the polymer electrolytes on lithium deposition and interfacial impedance will be discussed.