Microstructural controls of titanate nanosheet composites using carbon fibers and high-rate electrode properties for lithium ion secondary batteries

Composite electrodes of reassembled titanate and two kinds of carbon fibers were prepared and their high-rate electrode properties were examined. Multi-walled carbon nanotubes (MWNT) and vapor-grown carbon fibers (VGCF) were used for preparing the composites. The electronic conductivity of the MWNT composites increased with increasing contents of MWNT and exhibited a typical insulator-conductor transition. The MWNT composite with a MWNT content of 50 wt.% showed a capacity of 150 ± 5 mAh (g titanate)−1 at a discharge rate of 0.67 C, and did not show a good high-rate capability due to the large content of hydrated water. The effect of the porous structure of the electrodes was revealed in the high-rate electrode properties of the microstructurally controlled composites with both MWNT and VGCF. The composites with 50 wt.% VGCF and 10 wt.% MWNT showed a reversible capacity of approximately 160 mAh (g titanate)−1 at a discharge rate of 0.63 C and almost no capacity fading at relatively large discharge rate up to 19 C. A composite electrode with excellent high-rate capability was obtained by the microstructural control with carbon fibers.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights▶ Homogeneous mixture of nanosheets and carbon nanotubes was obtained. ▶ Mixing with carbon nanotubes resulted in increase in electronic conductivity. ▶ Nanosheet–carbon fiber composite electrode was porous. ▶ Microstructural controls contributed to excellent high-rate capability.