A flexible, hierarchically porous PANI/MnO₂ network with fast channels and an extraordinary chemical process for stable fast-charging lithium-sulfur batteries

Lithium-sulfur batteries with high theoretical specific capacity are quite promising in energy storage systems. The application of lithium-sulfur batteries however has mainly been hampered by the severe shuttle effect of polysulfides during the charging/discharging process. Here, we report the in situ self-assembling of ultra-thin flexible polyaniline layer decorated manganese dioxide nanoparticles (PANI-MnO₂) to form a three-dimensional hierarchically porous network as a sulfur host for lithium-sulfur batteries. The hierarchically porous PANI-MnO₂ network not only provides a porous structure to alleviate the volume expansion, but also offers fast channels to accelerate the transfer of active species, electrons and ions to improve the redox reaction kinetics. The as-fabricated PANI-MnO₂-S electrode thus demonstrates excellent electrochemical performance, with a stable capacity up to 1195 mA h g^-1 at 0.5C after 100 cycles. In particular, the hierarchically porous PANI-MnO₂ network employs an extraordinary chemical process for polysulfides to form active thiosulfates, which are further converted into Li₂S. This significantly suppresses the shuttle effect, thus providing the possibility for fast charging. As a result, the PANI-MnO₂-S electrode exhibits a discharge capacity of 640 mA h g^-1 at 2C after 500 cycles. Even at a high sulfur loading of 4.0 mg cm^-2, a stable areal capacity of ∼3.12 mA h cm^-2 is achieved at 1C after 200 cycles.