All-in-one Janus separator for lithium–sulfur batteries with lithium polysulfide and dendrite growth suppressed at temperature gradient effect

Designing an optimum separator configuration that can address severe lithium polysulfide (LiPS) shuttling and uncontrollable Li dendrite growth at the evaluated temperature is imperative for developing a high-performance, reliable, and safe Li–S battery (LSB). Herein, a promising LSB separator design is proposed, which consists of LiPS catalytic layer (LCL) and thermal conductive layer (TCL) fabricated by dual side filtrating the flower-like vanadium pentoxide (V2O5) microspheres and aluminum oxide (Al2O3) nanosheets, respectively. The LCL between the separator and S-cathode as combined LiPS trapper and catalyst significantly improves the redox reaction and sulfur utilization. At the anode/separator interface, the TCL uniforms Li-ion flux and thermal distribution to prevent undesirable Li dendrite growth under the temperature gradient (TG) effect. The Janus-type LCL-TCL separator with two parallel functions can achieve synchronous improvements in cathodic and anodic performance in LSB. Consequently, the LSB with Janus-type LCL-TCL separator exhibits excellent cycling stability with an ultralow capacity decay rate of 0.036% per cycle over 2000 cycles at 1C and superior rate capability up to 4C. The novel strategy can pave a new way to simultaneously tackle the limitations faced by anode and cathode in LSB.