Regulating Li-ion solvation structure and Electrode-Electrolyte interphases via triple-functional electrolyte additive for Lithium-Metal batteries

LiPF6-based carbonate electrolytes have been widely utilized in commercial Li-ion batteries; however, they encounter significant interfacial stability challenges when implemented in high-energy-density lithium-metal batteries (LMBs). Herein, we introduce innovative N,N-diethylcyclohexanamine (NDA) as a triple-functional electrolyte additive to enhance the stability and compatibility of carbonate electrolytes. Due to the high electronegativity of amino group, NDA additive not only eliminates HF/H2O but also modifies the Li+ solvation structure, effectively reducing the electrolyte decomposition, suppressing the hydrolysis of LiPF6 and inhibiting the transition metal (TM) dissolution. Moreover, NDA facilitates the formation of Li3N-rich solid-/cathodeelectrolyte interphase (SEI/CEI) layers thought preferential redox reactions at both the lithium metal anode (LMA) and Ni-rich cathode (LiNi0.8Co0.1Mn0.1O2, NCM811), which restrains the growth of Li dendrites, minimizes parasitic reactions, and promotes rapid Li+ transport. Therefore, the Li/NDA-added/Li symmetric cells exhibit remarkably stable cycling performance, lasting up to 630 hat 0.5 mA cm- 2/0.5 mAh cm-2. Compared to the baseline cells, the Li/LiNi0.8Co0.1Mn0.1O2 cells with 0.5 wt% NDA show higher capacity retention after 300 cycles at 1C (85.9% vs. 49.3%) and superior rate performance, even at 9C. These unique features of NDA present a promising solution for addressing the interfacial deterioration issue of LMBs.