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Expanded graphite as superior anode for sodium-ion batteries

2014; Nature Portfolio; Volume: 5; Issue: 1 Linguagem: Inglês

10.1038/ncomms5033

2041-1723

Wen Yang, Kai He, Yujie Zhu, Fudong Han, Yunhua Xu, Isamu Matsuda, Yoshitaka Ishii, John Cumings, Chunsheng Wang,

Advanced Battery Materials and Technologies

Graphite, as the most common anode for commercial Li-ion batteries, has been reported to have a very low capacity when used as a Na-ion battery anode. It is well known that electrochemical insertion of Na+ into graphite is significantly hindered by the insufficient interlayer spacing. Here we report expanded graphite as a Na-ion battery anode. Prepared through a process of oxidation and partial reduction on graphite, expanded graphite has an enlarged interlayer lattice distance of 4.3 Å yet retains an analogous long-range-ordered layered structure to graphite. In situ transmission electron microscopy has demonstrated that the Na-ion can be reversibly inserted into and extracted from expanded graphite. Galvanostatic studies show that expanded graphite can deliver a high reversible capacity of 284 mAh g−1 at a current density of 20 mA g−1, maintain a capacity of 184 mAh g−1 at 100 mA g−1, and retain 73.92% of its capacity after 2,000 cycles. Graphite is a common anode material for lithium-ion batteries, but small interlayer spacing makes it unsuitable for sodium-ion batteries. Here, Wen et al.synthesize a graphite material with expanded layer distances, which could be a promising anodic material for sodium-ion batteries.