Boosting lithium-sulfur battery performance using a phosphating nano-sulfur anchored on graphene framework anode

The shuttle effect of the intermediate lithium polysulfide and low sulfur utilization rate are two core issues restricting the further development of lithium-sulfur batteries (LSBs). Herein, a hierarchical sandwich super-structure (abbreviate as P-NS/GQDs/MGO) compose of phosphating nano-sulfur (P-NS) particles disperse and anchor on monolayer graphene oxide (MGO) with graphene quantum dots (GQDs) as the intermediate phase is constructed by hydrothermal method under oxygen-assist atmosphere and apply to the cathodes of LSBs. Notably, the phosphating and the robustly anchored P-NS effectively restricts the dissolution of intermediates in ether-based electrolytes and boosts charge/ion transport, which promotes the redox kinetics and maintains the electrode integrity during electrochemical cycling. Moreover, GQDs can facilitate the formation of specific bonding environments and interfacial interactions, resulting in accelerate heterogeneous nucleation, which effectively prevents P-NS agglomeration and volume change, improves sulfur utilization. Density functional theory (DFT) calculations reveal that the synergy of strategies relate to phosphating and interfacial interactions lead to high energy density and ultra-long cycle life with specific discharge capacities of 1117 and 838 mAh g-1 at 0.1 and 1.68A g-1, respectively. The capacity decay rate per cycle is 0.041% after 1000 charge-discharge cycles at 1.68A g-1.