The undesirable interactions between the charge carriers (Li + ) and various objects in the special microenvironment of batteries would cause uneven lithium (Li) metal deposition behavior, which severely impedes the application of Li metal batteries (LMBs). In recent years, many works focus on optimizing these interactions by functional molecules/ions modification. Nevertheless, related reviews are still absent. Here, this review introduces the regulation methods of Li metal deposition from molecular/ionic designs, which is a new perspective including Li + flux homogenization, the de-solvation process regulation, optimizing the solid electrolyte interphase (SEI) in conventional solvation structure and anion-rich solvation structure. Also, the general design principles are studied in each mechanism and some suggestions are proposed in the prospective future directions, aiming to guide the development of molecular/ionic designs and the actual application of LMBs with high energy densities.
Due to the unique safety qualities, solid composite polymer electrolyte (SCPE) has achieved considerable attentions to fabricate high‐energy‐density lithium metal batteries, but its overall performance still has to be improved. Herein, a high lithium salt content poly(vinylidene fluoride) (PVDF)‐based SCPE was developed, enhanced by hexagonal boron nitride (h‐BN) nanosheets, presenting perfect electrochemical performance, fast ion transport, and efficient inhibition of lithium dendrite growth. The optimized SCPE (PVDF‐L70‐B5) could deliver high ionic conductivity (2.98×10−4 S cm−1), ultra‐high Li+ ion transfer number (0.62), wide electrochemical stability window (5.24 V), and strong mechanical strength (3.45 MPa) at room temperature. Density functional theory calculation further confirmed that the presence of h‐BN could promote the dissociation of bis(trifluoromethanesulfonyl)imide lithium (LiTFSI) and the rapid transfer of Li+ ions. As a result, the assembled symmetric Li/Li battery and asymmetric Li/LiFePO4 battery using PVDF‐L70‐B5 SCPEs both exhibited high reversible capacity, long‐term cycle stability, and high‐rate performance when cycled at 60 or 30 °C. The designed SCPEs will open up a new route to synthesize solid‐state lithium batteries with high energy density and high safety.
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