Synergistic Effect of Cycling Strategies and Electrolyte for Effective Plating/Stripping of Anode Free Li Metal Batteries.

Abstract

Anode-free batteries (AFBs) are impressive and recent phenomena in the era of energy storage devices due to their high energy density and relative ease of production. However, dendrite formation during plating and stripping and low coulombic efficiency (CE) are the main challenges that impede practical implementation of these batteries. Here we report an extremely stable dual-salt electrolyte, 2M LiFSI+1M LiTFSI (2FSI+1TFSI)) in DME-DOL (1:1, v/v), system in comparison to the single salt 3M LiTFSI (3TFSI) in DME-DOL (1:1, v/v), to effectively stabilize AFB composed of LiFePO4 (LFP) cathode and bare Cu-foil anode for the first time. The electrolyte stabilized anode-free cell with the configuration Cu||LFP via reductive decomposition of its anions and enabled the cell to be cycled with CE of 98.9% for more than 60 cycles, which by far exceeds all the few reports in this field using other kinds of electrolytes. This results from formation of stable, ion conductive inorganic components rich Solid Electrolyte Interface (SEI) layer on the surface of in-situ formed Li-metal that prevent its direct contact with the electrolytes and hence intercepts undesirable parasitic reaction between Li and the electrolyte. Thus aforesaid SEI formed from reductive decomposition components of the dual-salt mitigates formation of dead lithium and dissolution of the in-situ formed Li surface during repeated cycling and prolongs cycle life of the battery.