Ultrasmall Li₂S-Carbon Nanotube Nanocomposites for High-Rate All-Solid-State Lithium–Sulfur Batteries

Due to the intrinsic poor ionic/electronic conductivities of Li₂S, it is a great challenge to realize high-rate all-solid-state lithium-sulfur batteries (ASSLSBs) with long cyclic performance. Herein, ultrasmall Li₂S (∼15 nm) is evenly deposited on a carbon nanotube (CNT) via a facile liquid-phase method to address these issues. The unique structure of the Li₂S deposited on a CNT composite cathode can improve ionic/electronic conductivities of Li₂S effectively and relieve the generated internal stress/strain during cycling. Specifically, the resultant Li/75%Li₂S-24%P₂S₅-1%P₂O₅/Li₁₀GeP₂S₁₂/Li₂S-53%CNT ASSLSBs show a reversible capacity of 651.4 mAh g^-1 under 1.0C at 60 °C after 300 cycles and even at a much higher cathode load of 5.08 mg cm^-2, a high discharge capacity of 556 mAh g^-1 can still be obtained under 0.1C after 20 cycles. The outstanding electrochemical performances are also attributed to the high diffusion coefficient of Li₂S-53%CNT, which is 39 times that of pristine Li₂S. This work presents an efficient procedure to design cathode materials with high ionic/electronic conductivities and paves the way for the successful commercialization of high-rate ASSLSBs.