Lithium Plating Using a Thermoplastic Vulcanizate Electrolyte

Lithium metal anodes have generated significant interest due to their high theoretical capacity. However, issues such as dendrite growth or cell failure caused by lithium loss with either liquid electrolytes or solid polymer electrolytes (SPEs) have hindered its widespread commercialization. In this work, we report on the electrochemical characterization of symmetric Li-SPE-Li cells made with a thermoplastic vulcanizate electrolyte, PCl:HNBR LiTFSI. Full plating of the lithium metal (LiM) electrode was achieved at 100 μA.cm −2 in pressurized pouch cells. This was confirmed ex situ using scanning electron microscopy which showed the absence of dendrites. The Sand equation was employed at higher current densities to determine that the lithium diffusion coefficient at 60 °C is 1.7 × 10 −8 cm 2 .s −1 . The calculated threshold current density j* was approximately 200 μA.cm −2 . The determination of the theoretical current density limit may provide critical information for the understanding of the behavior of cathode materials during cycling with lithium metal. Cell failure at high polarization or from short circuiting was experimentally confirmed in symmetric Li-Li cells where 100 cycles were performed at a current density below j* with 0.1 mAh.cm −2 of charge per cycle, while 0.5 mAh.cm −2 of charge rapidly induced cell failure.