Abstract
Hard carbon as an anode is critical for the near-future commercialization of Na-ion batteries. However, where Na ions are located at different states of charge with respect to the local structures of hard carbon remains a topic that is under debate. Recently, some groups, including ours, have suggested a structure-property correlation that assigns the slope capacity in galvanostatic charge/discharge curves to the binding of Na ions to structural defects of hard carbon. To test this correlation, herein, we prepared a highly defective hard carbon by microwaving a carbon that was obtained by pyrolysis of cellulose at 650 °C. After this microwave treatment for just 6 s, the reversible capacity of the hard carbon increased from 204 to 308 mAh/g, which is significantly higher than that of hard carbon annealed at 1100 °C for 7 h (274 mAh/g). The microwave treatment not only is energy-efficient but also retains a high extent of the structural vacancies in hard carbon, as demonstrated by neutron total scattering and the associated pair distribution function results. Indeed, such a defective structure exhibits a slope capacity much higher than that of the conventional hard carbon. This work serves as one of the first examples of rationally designed hard carbon guided by the new Na-ion storage mechanism. Furthermore, microwave heating represents a promising strategy for fine-tuning the structures of hard carbon for Na-ion batteries.
Original language | English |
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Pages (from-to) | 4536-4542 |
Number of pages | 7 |
Journal | Chemistry of Materials |
Volume | 30 |
Issue number | 14 |
DOIs | |
State | Published - Jul 24 2018 |
Funding
X.J. is thankful for the financial support from the U.S. National Science Foundation (Grants 1507391 and 1551693). The authors thank Professor Chih-Hung Chang and Mr. Changq-ing Pan for Raman analyses. The authors appreciate the help from Professor Mas Subramanian and Mr. Maxwell Wallace with the electronic conductivity tests. The authors thank Professor Michelle Dolgos and Mr. Todd Wesley Surta for the density tests. This research used resources at the Spallation Neutron Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated by Oak Ridge National Laboratory. The facility is supported by the DOE, Office of Science, under Contract DE-AC05-00OR22725.