A Ni/Ni2P heterostructure in modified porous carbon separator for boosting polysulfide catalytic conversion

Abstract

The intrinsic sluggish conversion kinetics and severe shuttle effect in lithium—sulfur (Li-S) batteries are responsible for their poor reversible capacity and cycling longevity, which have greatly hindered their practical applications. To address these drawbacks, herein, we design and construct a heterostructured Ni/Ni2P embedded in a mesoporous carbon nanosphere composite (Ni/Ni2P-MCN) for boosting polysulfide catalytic conversion in Li-S batteries. The Ni/Ni2P-MCN-modified separator could not only prevent the shuttle effect significantly through abundant chemical adsorptive sites, but also demonstrate superior catalytic reactivities for the conversion of polysulfides. More importantly, the conductive carbon matrix with an exposed mesoporous structure can serve as an effective physical barrier to accommodate deposited insoluble Li2S. Consequently, the cells with the Ni/Ni2P-MCN-modified separator exhibit greatly boosted rate capability (431 mA h g−1 at 5 C) and cycling stability (a capacity decay of 0.031% per cycle after 1500 cycles). Even at an enhanced sulfur loading of 4.2 mg cm−2, a stable and superior areal capacity (about 3.5 mA h cm−2) has been demonstrated. We envision that the unique Ni/Ni2P heterostructure in the porous carbon matrix could offer great potential for high-performance and sustained energy storage devices.[Figure not available: see fulltext.]