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Multiregion Janus-Featured Cobalt Phosphide-Cobalt Composite for Highly Reversible Room-Temperature Sodium-Sulfur Batteries

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journal contribution
posted on 30.07.2020, 10:04 by Zichao Yan, Yaru Liang, Weibo Hua, Xia-Guang Zhang, Weihong Lai, Zhe Hu, Wanlin Wang, Jian Peng, Sylvio Indris, Yunxiao Wang, Shu-Lei Chou, Huakun Liu, Shi-Xue Dou
Electrode materials with high conductivity, strong chemisorption, and catalysis toward polysulfides are recognized as key factors for metal-sulfur batteries. Nevertheless, the construction of such functional material is a challenge for room-temperature sodium-sulfur (RT-Na/S) batteries. Herein, a multiregion Janus-featured CoP-Co structure obtained via sequential carbonization–oxidation–phosphidation of heteroseed zeolitic imidazolate frameworks is introduced. The structural virtues include a heterostructure existing in a CoP-Co structure and a conductive network of N-doped porous carbon nanotube hollow cages (NCNHCs), endowing it with superior conductivity in both the short- and long-range and strong polarity toward polysulfides. Thus, the S@CoP-Co/NCNHC cathode exhibits superior electrochemical performance (448 mAh g–1 remained for 700 times cycling under 1 A g–1) and an optimized redox mechanism in polysulfides conversion. Density functional theory calculations present that the CoP-Co structure optimizes bond structure and bandwidth, whereas the pure CoP is lower than the corresponding Fermi level, which could essentially benefit the adsorptive capability and charge transfer from the CoP-Co surface to Na2Sx and therefore improve its affinity to polysulfides.