Low-Cost and Scalable Synthesis of High-Purity Li2S for Sulfide Solid Electrolyte

Sulfide solid electrolytes (SSEs) are preferable for all-solid-state lithium batteries (ASSLBs) to achieve high energy densities. However, the development of SSEs is impeded due to the high cost of the key raw material─Li 2 S. It is of great significance to synthesize high-purity Li 2 S with a more accessible and economic method. Herein, a new strategy for large-scale synthesis of Li 2 S with a low cost is developed on the basis of a lithium sulfate carbothermic reduction reaction in this work. A high yield of 81.78% and low raw material cost of $62 kg 1– are achieved, significantly lower than that of its commercial counterpart ($10,000–15,000 kg 1– ). To verify the effectiveness of this method, the as-prepared Li 2 S is further used to synthesize Li 6 PS 5 Cl (LPSC), and the corresponding electrochemical performances are evaluated. Room temperature ionic conductivity of LPSC reaches 2.63 mS cm –1 . In the [email protected] 2 O 3 ( [email protected] )//LPSC//Li–In ASSLB system, a high discharge specific capacity of 136 mAh g –1 is maintained after 700 cycles at 1C with an ultrahigh area loading of 35.6 mg cm –2 (calculated according to [email protected] 2 O 3, which is almost twice the other works). These performances are comparable to those using LPSC from expensive commercial Li 2 S in the control group, demonstrating the feasibility of the Li 2 S preparation strategy proposed in this work.