Multi-walled carbon nanotube paper anodes for lithium ion batteries

The lithium ion capacity has been measured for multi-walled carbon nanotubes (MWCNTs) synthesized by injection chemical vapor deposition (CVD) using a cyclopentadienyl iron dicarbonyl dimer catalyst. The high quality of the as-synthesized MWCNTs has enabled free-standing electrodes to be fabricated independent of polymeric binder or copper support. Galvanostatic cycling of these electrodes demonstrates excellent reversibility and coulombic efficiency (> 97% after cycle 3) using propylene carbonate based electrolytes, with no evidence for material degradation. A reversible capacity exceeding 225 mAh/g was measured after 20 cycles when using the electrolyte combination of (1:1:1 v/v) ethylene carbonate (EC):propylene carbonate (PC):diethyl carbonate (DEC) at a constant current of 74 mA/g (equivalent of C/5 for LiC6). Modification of the catalyst solvent during synthesis from xylenes to pyridine improved the lithium ion capacity in the resulting MWCNT paper to 340 mAh/g. In addition, this MWCNT paper showed a stable reversible capacity after 10 cycles, exceeding 225 mAh/g when cycled at an equivalent 1C rate. Therefore, the use of a nitrogen source during synthesis can lead to improved lithium ion capacity in novel MWCNT anodes.