Highly stable and robust bi-electrodes interfacial protective films for practical lithium metal batteries

Unstable solid electrolyte interphase between lithium metal and electrolyte results in low coulombic efficiency and limited cycle life, which hinder the utility of lithium metal anode. Besides, how to settle the cathode material corrosion in practical lithium metal batteries is also a key challenge. Here, lithium 2 trifluoromethyl-4,5-dicyanoimidazolide (C6F3LiN4) is reported as valid electrolyte additive for bi-electrode protective films formation in practical Li metal-based batteries. The C6F3LiN4 plays distinct functions in bi-electrode interface, it attributes to robust F, N-rich polymer interphase layer on the cathode which effectively protect the cathode from deterioration. And it promotes the even distribution of LiF and polycarbonate species on anode and prevent the formation of Li dendrites. The symmetric cell of C6F3LiN4 exhibits stable cycling performance with 1 mA cm−2 (700 h). In addition, the improvement in the Li metal deposition uniformity has been confirmed by atomic force microscope and simulation. Benefiting from the synergistic enhanced stability and uniformity of electrode interphase, the LiNi0.5Co0.2Mn0.3O2 || Li metal battery with C6F3LiN4 can maintain high capacity retention of 82.6% after 400 cycles. Importantly, the Li metal pouch battery pairing high-loading cathode (16.12 mg cm−2) also deliver longer cycle life, validating its feasibility in practical applications.