High-Performance Cathodes Prepared Via Liquid-Phase Method and Catalyzed by Co9s8 for All-Solid-State Lithium-Sulfur Batteries

Abstract

While all-solid-state lithium batteries and lithium-sulfur batteries are two advanced systems beyond the current generation of lithium-ion batteries and have been extensively studied for years, their combination of all-solid-state lithium-sulfur batteries (ASSLSBs) is seldomly explored. This paper herein demonstrates the success of making high-performance lithium sulfide cathodes for ASSLSBs. The composite cathode consists of the active material Li2S, a sulfide solid electrolyte Li6PS5Cl, a conductive carbon Ketjen Black, and a catalyst Co9S8 nanoparticles. Its preparation has the following features: mixing precursors via a liquid-phase method, in situ making Li6PS5Cl via calcination, and adding Co9S8 in the liquid-phase stage. Thanks to the presence of Co9S8 nanoparticles and the liquid-phase process for ensuring excellent solid-solid interfaces among electrode constituents, the maximum capacity of the obtained electrode with Li2S-loading of 2 mg/cm2 in Li-In|Li6PS5Cl|cathode batteries is enhanced by 0.8 times and the maintaining capacity at the 100th cycle by 4.3 times. With high loadings of 10 mg/cm2, the cathode achieves a high areal capacity of 6.4 mAh/cm2 at room temperature, equivalent to energy densities of 598 Wh/kg, and maintain the retention ratio of over 80% after 100 cycles. At 60 °C, ultrahigh real capacities of 9.4 mAh/cm2 and 14.1 mAh/cm2 can be achieved, equivalent to energy densities of 871 Wh/kg and 653 Wh/kg. Moreover, the mechanistic studies reveal that Co9S8 catalyzes all Li2S and also expedites the conversion between Li2S↔S by suppressing the polysulfides intermediates. Thus, this work opens the door of making high-performance Li2S cathodes for developing practical ASSLSBs.

Keywords: All-Solid-State Lithium-Sulfur Batteries, Li2S Cathodes, Co9S8 Catalyst, reaction mechanism