Interface-Driven Pseudocapacitance Endowing Sandwiched CoSe₂/N-Doped Carbon/TiO₂ Microcubes with Ultra-Stable Sodium Storage and Long-Term Cycling Stability
2021
Zhao, Hongshun | Qi, Yanli | Liang, Gang | Li, Jianbin | Zhou, Liangyan | Chen, Jinyuan | Huang, Xiaobing | Ren, Yurong
Cobalt diselenide (CoSe₂) has drawn great concern as an anode material for sodium-ion batteries due to its considerable theoretical capacity. Nevertheless, the poor cycling stability and rate performance still impede its practical implantation. Here, CoSe₂/nitrogen-doped carbon-skeleton hybrid microcubes with a TiO₂ layer (denoted as TNC-CoSe₂) are favorably prepared via a facile template-engaged strategy, in which a TiO₂-coated Prussian blue analogue of Co₃[Co(CN)₆]₂ is used as a new precursor accompanied with a selenization procedure. Such structures can concurrently boost ion and electron diffusion kinetics and inhibit the structural degradation during cycling through the close contact between the TiO₂ layer and NC-CoSe₂. Besides, this hybrid structure promotes the superior Na-ion intercalation pseudocapacitance due to the well-designed interfaces. The as-prepared TNC-CoSe₂ microcubes exhibit a superior cycling capability (511 mA h g–¹ at 0.2 A g–¹ after 200 cycles) and long cycling life (456 mA h g–¹ at 6.4 A g–¹ for 6000 cycles with a retention of 92.7%). Coupled with a sodium vanadium fluorophosphate (Na₃V₂(PO₄)₂F₃)@C cathode, this assembled full cell displays a specific capacity of 281 mA h g–¹ at 0.2 A g–¹ for 100 cycles. This work can be potentially used to improve other metal selenide-based anodes for rechargeable batteries.
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