Synergy of Nyquist and Bode Electrochemical Impedance Spectroscopy Studies to Assess the Effect of Morphology on the Electrochemical Properties of Li-Ni-Mn-Al-O Materials

The agglomerated and sheet Li_1.2Ni_0.3Mn_0.6Al_0.1O_2.2 materials were synthesized by hydrothermal method (HT-NMA) and sol-gel method (SG-NMA) respectively. Compared with sheet particles, agglomerated particles had better mutual contact. The specific surface area calculated by Brunauer–Emmett–Teller (BET) method was 8.92 m²/g for HT-NMA and 5.90 m²/g for SG-NMA. Larger specific surface area achieved better connections between cathode material and conductive agent. Better electron transitivity contributed to better electrochemical performance of HT-NMA, at the potential range of 2.0 V–4.8 V, the retention of capacity was 86 % at the current density of 20 mA/g after 31 cycles and the discharge capacity was 108mAh/g at the current density of 1000 mA/g. Both Nyquist and Bode plots were used to deeply investigate the reason for better performance of HT-NMA, the results showed that agglomerated particles had better electron migration capacity both before and after cycle.