A Protein-Based Janus Separator for Trapping Polysulfides and Regulating Ion Transport in Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are a promising candidate for the next-generation energy storage system, yet their commercialization is primarily hindered by polysulfide shuttling and uncontrollable Li dendrite growth. Here, a protein-based Janus separator was designed and fabricated for suppressing both the shuttle effect and dendrite growth, while facilitating the Li transport. The Li metal-protecting layer was a protein/MoS nanofabric with high ionic conductivity and good Li affinity, thus capable of homogenizing the Li flux and facilitating the Li transport. The polysulfide-trapping layer was a conductive protein nanofabric enabling strong chemical/electrostatic interactions with polysulfides. Combination of the two layers was achieved by an integrated electrospinning method, yielding a robust and integral Janus separator. As a result, a long-lived symmetric Li|Li cell (>700 h) with stable cycling performance was demonstrated. More significantly, the resulting Li-S battery delivered greatly improved electrochemical performance, including excellent rate capacity and remarkable cycle stability (with a low decay rate of 0.063 % per cycle at 0.5 A g over 500 cycles). This study demonstrates the effectiveness of the Janus separator configurations for simultaneously addressing the shuttle effect and dendrite growth issues of Li-S batteries and broadens the applications of electrospinning in electrochemistry community.