Solvent-free design of argyrodite sulfide composite solid electrolyte with superb interface and moisture stability in anode-free lithium metal batteries

Abstract

Anode-free lithium metal batteries (AFLMBs) reveal as future potential high-energy devices. Solidifying the electrolyte enables safer and more reliable battery operation. However, the commercial pristine sulfide and slurry-based preparation of sulfide composite solid electrolytes induce numerous pores on the pellet and membrane surfaces, respectively, which cause severe interface reactions and internal short circuits during cell performance. To overcome these challenges, we propose a solvent-free approach by fabricating deformable sulfide composite solid electrolyte (SCSE-4) via incorporating lithium argyrodite (Li6PS5Cl, LPSC) into a eutectic solution (succinonitrile (SN) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)) together with polyvinylidene fluoride (PVDF) binder and LiF salt additive, then shearing the composite for an hour. As a result, the Li|SCSE-4|Li cell achieves a high critical current density of 8 mA cm−2, suggesting its high Li-dendrite inhibition capability. Furthermore, the new SCSE-4 electrolyte with surface-modify Li and silver modify copper (Cu@Ag) at 0.2 mA cm−2 delivers ultra-stable cycling above 3000 h with high coulombic efficiency of 97.34% after 150 cycles with no sign of short circuit issue in comparison with the LPSC cycles only for 200 h. A promising anode-free full cell demonstrates successfully by inserting the SCSE-4 electrolyte between Cu@Ag current collector and high voltage NMC811 cathode.