Construction of Ni/Ni3N heterojunctions as reversible micro-reaction centers for lithium polysulfides

Lithium-sulfur batteries (LSBs) are one of the most promising next-generation energy storage systems. However, some intractable issues such as "shuttle effect", low electronic conductivity and large volume change of the S cathode seriously limit their application. In this work, a composite of Ni/Ni3N heterojunction-decorated hollow carbon nanotubes (Ni/Ni3N-CNT) was fabricated and used as a sulfur host, meanwhile, the mechanism of Ni/Ni3N heterojunctions in inhibiting the shuttle effect of lithium polysulfides (LiPSs) was investigated in detail. Density functional theory (DFT) calculations and experimental conclusions reveal that the Ni/Ni3N heterojunctions promote the nucleation and growth of Li2S2/Li2S and accelerate the redox process of LiPSs. Consequently, the Ni/Ni3N-CNT/S electrode demonstrates satisfactory electrochemical performance. It delivers a superior reversible capacity of 643.3 mA h g(-1) at 5C rate with an average decay rate of 0.10% per cycle over 400 cycles. Besides it can present a specific capacity of 439.7 mA h g(-1) with a high S loading of 5.0 mg cm(-2) after 100 cycles. Most importantly, this work proposes a simple method for the preparation of Ni/Ni3N heterostructures which can be used as reversible catalytic micro-reaction centers for LiPSs. In particular, our results will provide an experimental and theoretical basis for the application of other metal/metal nitride heterostructures in LSBs.