A Cost-Effective Sulfide Solid Electrolyte Li 7 P 3 S 7.5 O 3.5 with Low Density and Excellent Anode Compatibility.

The commercialization of all-solid-state Li batteries (ASSLBs) demands solid electrolytes with strong cost-competitiveness, low density (for enabling satisfactory energy densities), and decent anode compatibility (the need for cathode compatibility can be circumvented by the cathode coating techniques that are widely applied in sulfide-based ASSLBs). However, none of the reported oxide, sulfide, or chloride solid electrolytes meets these requirements simultaneously. Here, we design a Li 7 P 3 S 7.5 O 3.5 (LPSO) solid electrolyte, which shows a combination of all the aforementioned characteristics. The synthesis of this material does not need the expensive Li 2 S, so the raw materials cost is only $14.42/kg, which, unlike most solid electrolytes, lies below the $50/kg threshold for commercialization. The density of LPSO is 1.70 g cm -3 , considerably lower than those of the oxide (typically above 5 g cm -3 ) and chloride (around 2.5 g cm -3 ) solid electrolytes. Besides, LPSO also shows excellent anode compatibility. The Li|LPSO|Li cell cycles stably with a potential of ~50 mV under 0.1 mA cm -2 for over 4200 h at 25 °C, and the all-solid-state pouch cell with the Si anode shows a capacity retention of 89.29 % after 200 cycles under 88.6 mA g -1 at 60 °C.