Engineering hollow polyhedrons structured from carbon-coated CoSe2 nanospheres bridged by CNTs with boosted sodium storage performanceElectronic supplementary information (ESI) available. See DOI: 10.1039/c7ta02665j

• Main Authors: Tang, Yongchao, Zhao, Zongbin, Hao, Xiaojuan, Wang, Yuwei, Liu, Yang, Hou, Yanan, Yang, Qi, Wang, Xuzhen, Qiu, Jieshan
• Format: Journal Article
• Language: English
• Published: 04.07.2017
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c7ta02665j

Nanostructured CoSe 2 anode materials hold great promise for sodium ion batteries (SIBs), drawing much recent research attention. However, high-performance CoSe 2 based anodes are still challenging to obtain. Herein, using zeolitic imidazolate framework-67 (ZIF-67) particles as the starting material, nondestructive hollow polyhedral hybrids have been synthesized successfully, which are structured from CNT-bridged carbon-coated CoSe 2 nanospheres (CoSe 2 @C/CNTs). During the synthesis, the controlled in situ growth of CNTs introduces additional mesopores and open channels to the hybrids, and avoids serious agglomeration of the CoSe 2 nanospheres. When employed as anode materials for SIBs with ether-based electrolyte, the CoSe 2 @C/CNTs show overwhelming merits over graphitic carbon-coated CoSe 2 nanosphere polyhedral hybrids (CoSe 2 @GC) and bare CoSe 2 particles. Specifically, the CoSe 2 @C/CNTs anode displays a high reversible capacity (∼470 mA h g −1 at 0.2 A g −1 ), a good rate capability of ∼373 mA h g −1 even at 10 A g −1 , and an excellent cycling stability of over 1000 cycles with a capacity retention of ∼100% calculated from the 70 th cycle. In addition, the electrochemical reaction dynamics analysis indicates a considerable capacitive contribution during the discharge-charge cycles, which is beneficial to enhance the rate capability and cyclability of the CoSe 2 @C/CNTs anode. Such results could be ascribed to the stable ether-based electrolyte-active material intermediates, improved electrolyte-active material contact, and shortened charge transfer paths afforded by the unique hybrid nanostructure. Hollow polyhedrons were structured from carbon-coated CoSe 2 nanospheres bridged by CNTs, and showed a boosted rate capability/robust cyclability for sodium storage.