Nanoporous Li2S and MWCNT-linked Li2S powder cathodes for lithium-sulfur and lithium-ion battery chemistries

Abstract

In order to achieve high capacity utilization and high rate performance of lithium sulfide (Li₂S) cathode materials, it is critical to identify scalable methods for low-cost preparation of nanostructured Li₂S or Li₂S-carbon composites. Here, we report on the preparation and characterization of nanoporous Li₂S and multiwalled (MW) carbon nanotube (CNT) – linked Li₂S powders, prepared for the first time via a versatile solution-based method. The addition of MWCNTs enhances electrical conductivity and structural stability of the Li₂S-based cathodes and reduces polarization of cells operating at high current densities. The nanostructured Li₂S-based cathodes containing 20 wt% MWCNT showed promising discharge capacities of up to ∼1050 mA h g⁻¹_S at a slow rate of C/20 and ∼800 mA h g⁻¹_S at a C/2 rate. Quite remarkably, without any electrolyte additives (such as polysulfides or lithium nitrate) MWCNT-linked Li₂S cathodes demonstrated up to ∼90% capacity retention after 100 cycles in half cells (vs. Li foil) at a C/5 and C/10 rates.