Composite polymer electrolytes containing Co(NO3)2 can construct Li3N-rich interfacial layers in lithium-metal batteries

Abstract

Lithium metal batteries (LMBs) hold significant promise for energy storage applications, yet they are hindered by low ionic conductivity and severe interfacial issues with the electrolyte. In this study, we developed a Co(NO₃)₂@CPEs system to address these challenges. By incorporating Co(NO₃)₂ additives and LLZTO nanoparticles into the PEO matrix, we aimed to reduce PEO crystallization and enhance Li⁺ transport. Additionally, this approach facilitated the formation of a Li₃N-rich solid electrolyte interphase (SEI) layer. The study demonstrate that the inclusion of Co(NO₃)₂ promotes the generation of more Li₃N, LiF, and Li₂Co. These inorganic constituents enhance effectively Li⁺ mobility and mitigate the inhomogeneous lithium metal deposition. Co(NO₃)₂@CPEs has an ionic conductivity of 4.96 × 10^–4 S·cm^-2 at 60 °C (ionic conductivity of 2.4 × 10^–5 S·cm^-2 at 30 °C), a Li⁺ migration number of 0.41, and an electrochemical window of 4.5 V. In addition, the lithium-symmetric battery can be stably cycled for 800 h at a current density of 0.2 mA·cm^-2. The lithium metal battery with lithium iron phosphate (LiFePO₄) as the cathode, on the other hand, has good multiplication capability and cycling stability, in which it can be cycled for 200 revolutions at 0.5 C and has an initial specific capacity of 148.08 mAh·g^-1.