Polymeric Lithium Battery using Membrane Electrode Assembly

Abstract

Alternative configuration of lithium cell exploits electrode and polymer electrolyte cast all-in-one to form a membrane electrode assembly (MEA), in analogy to fuel cell technology. The electrolyte is based on polyethylene oxide (PEO), lithium bis-trifluoromethane sulfonyl imide (LiTFSI) conducting salt, LiNO₃ sacrificial film-forming agent to stabilize the lithium metal, and fumed silica (SiO₂) to increase the polymer amorphous degree. The membrane has conductivity ranging from ~5×10⁻⁴ S cm⁻¹ at 90 °C to 1×10⁻⁴ S cm⁻¹ at 50 °C, lithium transference number of ~0.4, and relevant interphase stability. The MEA including LiFePO₄ (LFP) cathode is cycled in polymer lithium cells operating at 3.4 V and 70 °C, with specific capacity of ~155 mAh g⁻¹ (1 C=170 mA g_LFP⁻¹) for over 100 cycles, without signs of decay or dendrite formation. The cell exploiting the MEA shows enhanced electrochemical performance as compared with the one using simple polymeric membrane stacked between cathode and anode. Furthermore, the MEA reveals the key advantage of possible scalability and applicability in roll-to-roll systems for achieving high-energy lithium metal battery, as demonstrated by pouch-cell application. These data may trigger new interest on this challenging battery exploiting the polymer configuration for achieving environmentally/economically sustainable, and safe energy storage.