Hollow Cu-Cu2O/Ni-NiO/C as cathodes for magnesium-sulfur batteries

Abstract

To address the issue of active substance (sulfur) loss caused by the polysulfide shuttle effect, we designed and developed a hollow Cu-Cu2O/Ni-NiO/C derived from a bimetallic Cu/Ni-MOF as a host material for magnesium-sulfur batteries (MSBs). The nitrogen-doped carbon skeleton provides good electrical conductivity for magnesium ion and electron transport and also offers abundant active sites to adsorb and anchor polysulfides. The Cu-Cu2O/Ni-NiO in situ distribution on the carbon skeleton ensures the integrity of the internal redox reaction due to its high catalytic activity. In addition, the Cu and Ni sites can inhibit the shuttle effect and reduce the loss of active substances by anchoring polysulfides. Hence, Cu-Cu2O/Ni-NiO/C-S exhibits a high discharge-specific capacity of 1050.6, 950.6, 890.4, 820.7, and 677.1 mAh g−1 at 0.1, 0.2, 0.5, 1, and 2 A g−1, respectively. Cu-Cu2O/Ni-NiO/C-S shows remarkable cycling stability with capacity retention of 77.07% and a decay rate of 0.14% per cycle after 200 cycles at 0.2 A g−1, and maintains a lower decay rate of 0.06% per cycle after 500 cycles at 1 A g−1. Furthermore, Cu-Cu2O/Ni-NiO/C-S exhibits high discharge capacity and cycling stability even with a surface loading of 3.5 mg cm−2. This study provides an example of the design and synthesis of highly catalytically active cathode materials for MSBs.