Dual-functional cobalt phosphide nanoparticles for performance enhancement of lithium-sulfur battery

Metal phosphides fabricated using metal organic frameworks (MOF) have recently been widely studied in lithium-sulfur (Li–S) battery because of the unique microstructure and electrocatalytic activity. However, the growth of MOF is very rapid and the particle size mainly focuses on micrometer, which severely limits the catalytic effect. Herein, we fabricate nanoscale MOF embedded with carbon nanotube (CNT), owing to the ultra-small CoP (25 nm, denoted as S-CoP) derived from the phosphating of MOF and unique network of CNT, the designed micro-nano structure S-CoP/CNT accelerates the conversion of lithium polysulfides (LiPSs), boosts the precipitation/decomposition processes of lithium sulfide (Li 2 S) and provides an effective adsorption barrier. Meanwhile, the fabricated S-CoP/CNT separator endows an ultralong dendrite-free Li deposition up to 1714 h. The Li–S battery with S-CoP/CNT modified separator can deliver an initial capacity of 1513.22 mAh g −1 at 0.1 °C, a reversibility capacity of 574.95 mAh g −1 up to 500 cycles at 0.5 °C. The satisfactory performance is also verified at a high sulfur loading of 4.2 mg cm −2 and a favorable initial capacity of 1161.8 mAh g −1 can be maintained. This study provides a facile strategy to fabricate nano metal phosphides derived from MOF for Li–S battery. Graphical abstract The S-CoP/CNT can not only promotes the electrolyte infiltration into the dual-functional separator, accelerates the redox kinetics of LiPSs and suppresses the corresponding shuttle effect, but also homogenizes the Li-ion distribution and leads to the dendrite-free lithium deposition.