Complexion-induced Cu²⁺ coordinated phase separation PBI membrane for lithium metal batteries

The uncontrolled dendritic lithium production issues and the highly reactive behavior of lithium with electrolytes has limited use of lithium metal batteries. Herein, we utilized a straightforward method of the Complexion-Induced Phase Separation (CIPS) to fabricate a Cu²⁺ coordinated polybenzimidazole (PBI) membrane for a lithium metal battery. CIPS offer improved control over the structure and composition of the membrane, potentially leading to improved selectivity in ion transport, enhancing the safety and longevity of the battery. The formation mechanism and influencing elements of PBI-Cu are analyzed through experimental analysis and density functional theory calculations (DFT). The PBI-Cu membrane is effective in facilitating reversible lithium stripping and plating processes, suppressing dendrite formation, and promoting stable long-term cycling. Notably, the PBI-Cu cell demonstrated stable cycling conditions for over 200 h at a very high current density of 4 mA cm⁻². The impressive rate performance was also confirmed during Li//LiFePO₄ full cell operation, where it maintained a stable capacity of 120 mAh g⁻¹ for more than 300 cycles. This research provides an in-depth insight into membrane design and paves the way for its application in various other energy-related technologies. © 2024 Elsevier B.V.