Highly ordered carbon nanotubes to improve the conductivity of LiNi_0.8Co_0.15Al_0.05O₂ for Li-ion batteries

The low electronic conductivity of the cathode in rechargeable Li-ion batteries results in a large overpotential at high charge/discharge rate and reduces the power density of the batteries. Here, vertically aligned carbon nanotubes (VACNTs), which exhibited a higher purity and a better rate of dispersion than the agglomerated carbon nanotubes (ACNTs), were synthesized to improve the electronic conductivity of the cathode and to optimize the performance of the batteries at high rates. 1.5 wt% of the VACNTs in LiNi_0.8Co_0.15Al_0.05O₂ (LNCA) is sufficient to build an electronic conductive network, and the cell exhibited an improved performance with a high capacity of 167.4 and 157.5 mAh g⁻¹ at 5 C and 10 C, respectively; moreover, the cell showed a good cycling stability with a capacity retention of 85.2% after 120 cycles at 1 C, which is much better than the cell with ACNTs and even better than the cell with a uniformly dispersed ACNTs slurry. The prepared 0.6 Ah pouch cell with only 0.5 wt% VACNTs and 1 wt% Super P (SP) in the cathode displayed better cycling and rate performance than the cell with 3 wt% SP in the electrode.