Sustainable Release of Mg(NO3)2 from Separator Boosts Electrochemical Performance of Lithium Metal as Anodes for Secondary Batteries

Abstract

Lithium metal batteries (LMBs) can alleviate the ‘range anxiety’ and have broad prospects due to their high energy densities. However, poor safety and cycling performances of the LMBs due to the unconstrained lithium metal anodes (LMAs) limit their further application. Many solutions have been tried to address the problems in LMBs, but few studies focused on cheap separators. Here, a separator modified by conductive Super P and Mg(NO₃)₂ (MN) (SP@MND) is prepared for LMBs. The Super P can promote the reaction kinetics of cathodes. The MN can be sustainably released from the modified separator into the electrolyte and dissociates into Mg²⁺ and NO^3-, which standardizes the deposition of Li+ cations and forms an ionic-conductive protective layer on the LMA, respectively. The SP@MND has an outstanding performance in both ether-based and ester-based electrolytes, and LMAs can sustain long cycling life of over 4800 h at 0.5 mA cm^-2 of 0.5 mAh cm^-2 and high current density up to 50 mA cm^-2. The assembled LMBs exhibit low capacity decay rate of 0.059% after 1000 cycles at 3 C for Li//S battery and a high average coulombic efficiency of 99.2% at 10 C for Li//LiFePO₄ one after 1000 cycles. This work provides a solid basis for the production of LMBs with a high ratio of performance/cost.