Effect of Annealing on the Discharging Performance of Carbon Nanotubes for Nickel Hydrogen Secondary Battery Negative Material

Abstract

The effect of annealing temperature for carbon nanotubes (CNTs) in vacuum on its performance as a nickel hydrogen battery negative material is investigated by high resolution transmission electron microscopy (HRTEM), Raman, and discharge capacity. The electrochemical discharge performance of CNTs can be improved by annealing treatment because of few amorphous carbon impurities and defects in annealed CNTs by observations of HRTEM and Raman spectra. With the increase in annealing temperature, the discharge capacity increases initially and then decreases. The optimum annealing temperature is around 750°C. Among investigated CNTs with different diameters, the effect of annealing on the discharge performance for CNTs with a diameter of 40-60 nm is most significant. It has the best discharging capacity of 585 mAh/g with annealing at 750°C, which is 1.4 times compared to CNTs without annealing. The discharging performance of annealed CNTs under different discharging currents is also investigated. The annealed CNT electrodes at 750°C still have 300 mAh/g discharging capacity in a discharging current of 2000 mA/g, showing that annealed CNTs have good discharging performance under great current discharging. © 2010 The Electrochemical Society.