A thermoregulating separator based on black phosphorus/MOFs heterostructure for thermo-stable lithium-sulfur batteries

Apart from the traditional problems of shuttling effect of polysulfides and unmanageable growth of lithium dendrites, lithium-sulfur batteries (LSBs) could also unavoidably undergo drastic changes in internal temperature for high-rate charging/discharging process, which could shorten the cycle lifespan of the batteries. Herein, a novel asymmetric thermoregulating separator based on MOFs/black phosphorus heterostructure ([email protected]) was developed to address the issues above-mentioned effectively. The asymmetric separator was fabricated by encapsulating the phase-change material of paraffin wax (PW) in polyacrylonitrile nanofibers followed by vacuum filtration of [email protected] hybrids onto the surface of the electrospun separator. The block-adsorb-catalyze process of polysulfides in [email protected] heterostructure interface contributed to the smooth and effective conversion of the captive polysulfides, therefore the cell exhibited ultralow fading rate of 0.016% per cycle over 1000 cycles, which was comparable to other relative reports of Li-S cells. Moreover, the thermoregulating separator could alleviate the internal temperature rise timely since the melting process of PW could absorb large amounts of heat. The experimental results also showed that the heat absorption and preservation properties of the encapsulated PW endowed the separator with good performance in temperature adjustment, therefore the cells presented smooth and stable cycling stability as well as stable coulomb efficiency compared to none PW-based separator. This work proposed a new insight of phase-change material-based separator contributing to stable solid electrolyte interface and cycling stability of the battery in temperature-varying condition, anticipating its promising application in stable and long-life cycles Li-S batteries.