Bio-template fabrication of nitrogen-doped Li3V2(PO4)3/carbon composites from cattail fibers and their high-rate performance in lithium-ion batteries

This is the first report of the use of an original precursor obtained from an abundant, green and economical bio-mass waste: cattail fibers. Nitrogen-doped Li3V2(PO4)3/carbon composites with copious conductive networks have been successfully synthesized using cattail fibers as a bio-template employing facile, repeated solution immersions. The morphologies and microstructure of the nitrogen-doped Li3V2(PO4)3/carbon composites were characterized using an X-ray diffractometer and scanning electron microscopy. A nitrogen-doped Li3V2(PO4)3/carbon composite (sample C-3) was obtained through three times solution immersion, which completely covered the carbon fibers with thin, porous layers of Li3V2(PO4)3. These orderly nitrogen-doped Li3V2(PO4)3/carbon (C-3) were orderly interconnected porous Li3V2(PO4)3 nanoconnections. This novel structure was found to have interlaced conductive networks that were formed between the N-doped carbon fibers and porous Li3V2(PO4)3 nanoconnections. However, the Li3V2(PO4)3/carbon composites, termed sample (C-V), obtained using the immersion process in a vacuum, displayed a random accumulation of rod-like Li3V2(PO4)3/carbon composites. Sample C-3 exhibited the highest reversible capacity of 113.2 mAh g−1 after 500 cycles at 15 C between 3.0 and 4.3 V, but at under these same conditions, the remaining reversible capacity of sample C-V was only 82.3 mAh g−1.