Hollow quasi-polyhedron structure of NiCoP with strong constraint sulfur effect for lithium sulfur battery

Abstract Double metal phosphide NiCoP with hollow quasi-polyhedron structure was rationally designed and synthesized via acidic etching, precipitation of ZIF-67 polyhedra and further phosphorization treatment. The outer and inside shells of the hollow quasi-polyhedral structure were formed by many interconnected nanosheets with a lot of micro-holes. It could be found that this unique 3D structure material could be well applied to lithium sulfur battery (LSB). The NiCoP material with a huge specific surface area (1539.2 m2 g−1) allowed for high loading of sulfur. The NiCoP material strongly adsorbed polysulfides because their natural oxidation (forming Ni-O-P, Co-O-P-like species) activated the Co/Ni sites for binding polysulfides via strong Co S, Ni S bonding. In particular, NiCoP hollow quasi-polyhedra exhibited higher binding energy than CoP. The results revealed that this composite had a specific discharge capacity up to 815.3 mAh/g at the first cycle and remained 620 mAh/g after cycling for 200 at 0.1C with almost 100% coulombic efficiency.