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

Abstract

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 (C 6 F 3 LiN 4 ) is reported as valid electrolyte additive for bi-electrode protective films formation in practical Li metal-based batteries. The C 6 F 3 LiN 4 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 C 6 F 3 LiN 4 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 LiNi 0.5 Co 0.2 Mn 0.3 O 2 || Li metal battery with C 6 F 3 LiN 4 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. • The C 6 F 3 LiN 4 is prior to form films on bi-electrodes more preferentially. • The lithium dendrites suppression is verified by experiment and simulation. • Highly stable electrochemical performance in practical Li metal batteries has been achieved. • This work reveals the importance of bi-electrode film in practical applications.