The electrochemical behaviors of Zn-Al-La-hydrotalcite in Zn-Ni secondary cells

Zn-Al-La-CO3 layered double hydroxides (LDHs) are prepared by the constant pH co-precipitation method and proposed as a novel anodic material in Zinc-Nickel secondary cells. The X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images reveal that the as-prepared samples are well-crystallized and hexagon layer structure. Electrochemical performances of Zn-Al-La-hydrotalcites with different Zn/Al/La molar ratios are investigated by galvanostatic charge-discharge measurements, cyclic voltammograms (CV) and Tafel polarization curves. In comparison with the Zn-Al-hydrotalcite, Zn-Al-La-hydrotalcites with different Zn/Al/La molar ratios have more stable cycling performance. After 400 cell cycles, Zn-Al-La-LDH with Zn/Al/La = 3:0.8:0.2 retains specific discharge capacity of 297 mAh g−1 with a retention rate of 79.0%, which is much superior to that of 205 mAh g−1 with a retention rate of 53.5% for the Zn-Al-La-LDH with Zn/Al/La = 3:0.9:0.1 and 241 mAh g−1 with a retention rate of 69.0% for the Zn-Al-La-LDH with Zn/Al/La = 3:0.6:0.4. The results demonstrate that the Zn-Al-La-LDH with Zn/Al/La = 3:0.8:0.2 has the best reversible cycling behavior. The CV exhibits well reversibility and the Tafel polarization curves reveal more positive corrosion potential for Zn-Al-La-hydrotalcite.