Performances Enhanced High-nickel Lithium Metal Batteries through Stabling Cathode and Anode Electrolyte Interfaces
The interfaces stability between the cathode and anode with the electrolyte is the key to the performances of the lithium metal batteries (LMBs). A FEC optimized LiTFSI-LiBOB dual salt (Dual-salt + FEC) electrolyte is employed to systematically investigate its effects on the LMBs. The high nickel Li||NCM full LMBs using the Dual-salt + FEC electrolyte presents significantly enhanced long-term cycling stability with 83.8% capacity retention after 500 cycles, which is much higher than 65.4% for LiPF6-based electrolyte. The improving mechanism has been studied using aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging combined with the X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). HAADF-STEM results firstly provide direct evidences in atomic scale that the corrosion and transition metal dissolution for the high nickel NCM cathode cycled in Dual-salt + FEC electrolyte could be effectively suppressed. Moreover, the HRTEM and XPS results further disclose that, a stable CEI on cathode and a thinner, smoother and strong adhesion of SEI on Li metal anode in the high nickel Li||NCM cell could be achieved using the Dual-salt + FEC electrolyte. This holistic analysis of the cathode and anode electrolyte interfaces will significantly advance the LMBs design principles through manipulation of the electrolyte chemistry.