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Unique walnut-shaped porous MnO<inf>2</inf>/C nanospheres with enhanced reaction kinetics for lithium storage with high capacity and superior rate capability

Huang, SZ and Cai, Y and Jin, J and Liu, J and Li, Y and Wang, HE and Chen, LH and Hasan, T and Su, BL (2016) Unique walnut-shaped porous MnO<inf>2</inf>/C nanospheres with enhanced reaction kinetics for lithium storage with high capacity and superior rate capability. Journal of Materials Chemistry A, 4. pp. 4264-4272. ISSN 2050-7488

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Abstract

© The Royal Society of Chemistry 2016. Unique walnut-shaped porous MnO 2 /carbon nanospheres (P-MO/C-NSs) with high monodispersity have been designed and prepared for lithium storage via in situ carbonization of amorphous MnO 2 nanospheres. Polyvinylpyrrolidone (PVP) is utilized as both the surfactant for morphology control and carbon source for carbon scaffold formation accompanied with MnO 2 crystallization. Such a unique walnut-shaped porous nanostructure with an intimate carbon layer provides a large contact area with the electrolyte, short transport path length for Li + , low resistance for charge transfer and superior structural stability. The P-MO/C-NS electrode demonstrates high lithium storage capacity (1176 mA h g -1 at 100 mA g -1 ), very good cycling stability (100% capacity retention versus the second cycle) and excellent rate capability (540 mA h g -1 at 1000 mA g -1 ). We propose that it is the deep oxidation of Mn 2+ to Mn 3+ in P-MO/C-NSs, which results in an extraordinarily high capacity of 1192 mA h g -1 at a current density of 1000 mA g -1 after a long period of cycling, very close to the maximum theoretical reversible capacity of MnO 2 (1230 mA h g -1 ). This is the highest value ever observed for MnO 2 -based electrodes at such a rate. The high lithium storage capacity and rate capability can be attributed to the enhanced reaction kinetics owing to the walnut-shaped porous nanostructure with an intimate carbon layer. This work provides a meaningful demonstration of designing porous nanostructures of carbon-coated metal oxides undergoing deep conversion reactions for enhanced electrochemical performances.

Item Type: Article
Subjects: UNSPECIFIED
Divisions: Div B > Solid State Electronics and Nanoscale Science
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 19:07
Last Modified: 21 Sep 2017 01:35
DOI: