Introducing KI as a functional electrolyte additive to stabilize Li metal anode

A lithium metal battery (LMBs) is an excellent battery system for advanced electrochemical energy storage. However, the growth of lithium dendrites, the accumulation of inactive lithium, and the side reactions between lithium metal and electrolytes limit the cycling stability of LMBs. Herein, we introduce KI additive into lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)/ether-based electrolyte and lithium hexafluorophosphate (LiPF6)/ ester-based electrolyte for cycling stability improvement of LMBs. Cu-mesh@Ag||Li half-cell with 0.01 M KI additive exhibits a Coulombic efficiency as high as 98.8 % over 200 cycles. The improved performance due to the electrostatic shielding effect formed by K+ at low concentration and the rapid recovery of inactive lithium by iodine redox. The corresponding Li||Li symmetrical cell shows an outstanding lifespan of 1400 h at 1.0 mA cm-2 with 1.0 mAh cm- 2. Meanwhile, in the 1 M LiTFSI + 0.01 M KI electrolyte, the Cu-mesh@Ag-Li||LiFePO4 (LFP) full cell holds capacity retention of 91.7 % over 800cycles at 2.0 C, the Li||LiNi0.8Co0.1Mn0.1O2 (NCM811) full cell possesses much better capacity retention of 54 % after 500 cycles at 1.0 C. This work offers a cost-effective proposal to improve application potential with the electrolyte engineering of rechargeable Li metal batteries.