Enhancing the rate and cycling performance of spherical ZnO anode material for advanced zinc-nickel secondary batteries by combined in-situ doping and coating with carbon

High-performance ZnO microspheres doped and coated with carbon has been successfully fabricated by a facile three-step process using trisodium citrate as doping carbon source and glucose as coating carbon source. Compared with carbon free ZnO precursor, the resulting ZnO-N2@Cmicrospheresexhibitsuperiorrateperformanceandenhancedcyclingstability.(*) At a rate of 10C (5000 mA g−1), the ZnO-N2@C exhibits specific discharge capacity and volumetric capacities of 283.4 mAh g−1 and 858.7 mAh cm−3, respectively, while the values for the carbon free ZnO precursor are only 140.2 mAh g−1 and 423.4 mAh cm−3. After cycling 200 times at 500 mA g−1, the obtained ZnO-N2@C can maintain a satisfying capacity of 508.2 mAh g−1, corresponding to a superior capacity retention (94.7%). In contrast, carbon free ZnO can only deliver the capacity of 109.4 mAh g−1 and a capacity retention of 24.7% after 200 cycles. This outstanding improvement is attributed to the synergistic effect of the combined in-situ doping and coating carbon, including reduced charge-transfer resistance, enhanced electrochemical reversibility, and better anti-corrosion capabilities. As a result, it is believed that ZnO-N2@C should be an attractive and promising anode material for high power Zinc-Nickel batteries.