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

Abstract 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 2 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 −1 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.