Highly Dispersed Catalytic CoS among a Hierarchical Carbon Nanostructure for High-Rate and Long-Life Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are next-generation energy storage systems with high energy density, and the rate performance is a very important consideration for practical applications. Recent approaches such as introducing catalytic materials to facilitate polysulfide conversion have been explored, yet the results remain unsatisfactory. Here, we present an optimized Li-S electrode featured by a large amount of highly dispersed CoS nanoparticles (∼10 nm in size) throughout a hierarchical carbon nanostructure hybridized from ZIF-67 and carbon nanotube (CNT) sponge. This enables homogeneous distribution and close contact between infiltrated sulfur and CoS nanoparticles within the ZIF-67-derived N-doped carbon nanocubes, leading to effective chemical interaction with polysulfides, maximum catalytic effect and enhanced lithium ion diffusion, while the built-in three-dimensional CNT network ensures high electrical conductivity of the electrode. As a consequence, the Li-S battery exhibits both extraordinary rate performance by maintaining a capacity of ∼850 mAh g at very high charge/discharge rate (5 C) and long-term cycling stability with 85% retention after 1000 cycles at 5 C (an average capacity fading rate of only 0.0137% per cycle).