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

Abstract

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%.