Enabling ultrafast ionic conductivity in Br-based lithium argyrodite electrolytes for solid-state batteries with different anodes

One of the primary obstacles that has inhibited the development of solid-state batteries is the lower conductivity of solid electrolytes compared to liquid electrolytes. Li6PS5Br is a promising solid electrolyte for solid-state batteries due to its high ionic conductivity and low cost. Herein, we enhance the lithium conductivity by replacing S with Br and systematically tailor the composition and synthesis parameters to optimize the conductivity. Li5.5PS4.5Br1.5 exhibits higher ionic conductivity and better lithium compatibility than the bare Li6PS5Br. Although lithium metal is chemically unstable with Li5.5PS4.Br-5(1.5), stable cycling behavior in lithium symmetrical cells with small overpotential and resistance after 2500 h are achieved. Both the bare NCM622 and LiNbO3-coated NCM622 shows long cycling life with Li5.5PS4.5Br1.5 electrolyte in combination with In or lithium metal anodes. The LiNbO3 layer can effectively improve the capacity and cycling behavior of the solid-state battery using different anodes. Moreover, the electrochemical performances of Li5.5PS4.5Br1.5-based solid-state batteries are influenced by the charge/discharge voltage windows.