Enhanced sulfur utilization in lithium-sulfur batteries by hybrid modified separators
Lei Zhou, Hao Li, Yue Zhang, Ming Jiang, Dmitri L. Danilov, Rüdiger‐A. Eichel, Peter H. L. Notten
Abstract
The extraordinary energy density and low cost enable lithium-sulfur (Li-S) batteries to be a promising alternative to traditional energy storage systems. The principal hurdle facing Li-S batteries is the unsatisfactory utilization of sulfur cathodes. The detrimental shuttle issue of polysulfides and the sluggish charge transfer kinetics result in quick capacity degradation of Li-S batteries. An MFLC hybrid material composed of manganese-iron layered double hydroxides (Mn-Fe LDH) and carbon nanotubes (CNT) has been developed. Such heterostructure combines the advantages of effective chemical bonding of Mn-Fe LDH towards polysulfides with the high conductivity of CNT. When modified on a polypropylene (PP) separator, the hybrid material is proven to significantly inhibit the shuttle issue of polysulfides and accelerate their redox reaction kinetics. Li-S batteries with MFLC-modified separators revealed considerably improved electrochemical performance. A high initial capacity of 1138 mA h g−1 and 70 % capacity retention after 200 cycles were achieved at 0.2 C. The enhanced sulfur utilization can be directly evaluated from the discharge voltage plateaus. The results indicate a new solution for the practical application of Li-S batteries and provide a simple approach to determine the efficiency of sulfur utilization.