Enhanced discharge voltage by CuO and RuO_2 modification of ferrate(VI) cathode in alkaline super-iron/TiB_2 batteries

摘要

The K_2FeO_4/TiB_2 battery has a significant advantage of battery capacity due to their multi-electron discharge reaction both of the cathode K_2FeO_4 (3e~-) and the anode TiB_2 (6e~-). However, the more positive reduction potential of TiB_2 anode results in a lower discharge voltage plateau of K_2FeO_4/TiB_2 battery, compared with the K_2FeO_4/Zn battery. The simple modification of Fe(VI) cathode with CuO additive was used to improve the cathode reduction kinetics and decrease the polarization potential in the discharge process. Another electrocatalysis media RuO_2 with excellent electric conductivity is used as additive in K_2FeO_4 cathode to demonstrate which effect is more important for the discharge voltage plateau, electrocatalysis or electron conductivity of additives. The results show that the 5% CuO additive modified K_2FeO_4/TiB_2 battery exhibits an enhanced discharge voltage plateau (1.5 V) and a higher cathode specific capacity (327 mAh/g). The advanced discharge voltage plateau can be due to the electrocatalysis of additives on the electrochemical reduction kinetics of Fe(VI) cathode in the whole discharge process, rather than the good electronic conductivity of additives.