Additives strategies to improving cycling stability of Li metal batteries by modifying electrode electrolyte interphases

Li metal batteries (LMBs) have attracted much attention due to the ultra-high theoretical capacity of the Li metal anode (LMA). However, the uncontrollable dendrites growth and low coulombic efficiency hinder their practical application. Here, we explore 3,5-difluoropyridine (2F-BD) as a novel electrolyte additive to enable high-performance LMBs. The 2F-BD additive participates in and modifies the solvation structure of Li ions by reducing the coordinated number of PF₆⁻ at the electrode surface, leading to the formation of a LiF and Li₃N-rich solid electrolyte interphase (SEI). The LiF component increases the robustness of SEI and suppresses the formation of Li dendrites, while the Li₃N component facilitates the transportation and reaction kinetics of Li ions. As a result, the Li||Li symmetric cell presents a stable cycling performance of up to 500 ​h at a current density of 1 ​mA ​cm⁻². After coupling with LiFePO₄ cathode, the obtained full cell achieves high specific capacities of 106.06 ​mA ​h ​g⁻¹ and 84.98 ​mA ​h ​g⁻¹ at 2.55 ​mA ​cm⁻² and 5.10 ​mA ​cm⁻², respectively, and maintains a high capacity retention of 84.0% after 1000 cycles at 0.13 ​mA ​cm⁻², with an average cycling CE of 99.58%.