Tuning Surface Energy of Pristine Separator with γ-AlO(OH) Nanocapsules for Inhibiting Lithium Polysulfide Shuttle and Lithium Dendrite Growth

The severe shuttling of dissolved lithium polysulfides (LiPSs) (Li2Sx, 4 ≤ x ≤ 8) and the generation of lithium dendrites upon cycling have hampered the safety and performance of lithium–sulfur batteries (LSB). Herein, we report the strategy of tuning the surface energy of the pristine separator with γ-AlO(OH) nanocapsules to address the aforementioned problems. The enhanced surface energy from 26.62 to 63.64 mJ m–2 yields multiple benefits, including impeding the migrating polysulfides by chemically binding them with γ-AlO(OH) nanocapsules, enhancing the lithium–ion migration through the separator by promoting hydrophilicity in the separator and mitigating the generation of lithium dendrites by a uniform distribution of Li+ on top of lithium metal via interaction with γ-AlO(OH) nanocapsules. Live discharging of the H-cell demonstrated that the LiPS mitigation can be curtailed by using γ-AlO(OH) nanocapsules modified separator (BNC). Moreover, the BNC separator's thermally insulating properties render the Li–S battery stable behavior while cycling at an even temperature of 75 °C. The spray coating technology used for coating γ-AlO(OH) nanocapsules on top of pristine separator offers a scalable solution for commercializing such modified separators.