Unraveling the synergistic effects and mechanisms of nano-carbon modification on metal hydride alloys for enhanced electrochemical performance in energy storage applications

The conflicting relationship between anti-corrosion ability and electrochemical kinetics significantly hinders the comprehensive performance of hydrogen storage alloys in nickel-metal hydride batteries. In this study, we successfully coated a nano carbon layer on the AB5-type hydrogen storage alloy to achieve exceptional peak power, high-rate discharge capability, low-temperature performance, and cycling stability simultaneously as the MH electrodes. The surface carbon layer could not only enhance the surface conductivity, but also result in a reduced state of the alloy to mitigate the oxidation of alloy owing to the electronic transfer from the carbon layer to metal. The carbon-coated alloy electrode thus exhibits superior electrochemical properties compared to the pure alloy electrodes. The discharge capacity of the carbon-coated electrode at a discharge current density of 4.5 A g−1 is 247.21 mAh/g, which is 2.37 times that of the master electrode (104.12 mAh/g). Additionally, the discharge capacity of the carbon-coated electrode at −40 °C reaches an impressive 250.85 mAh/g. More importantly, these carbon-coated alloy electrodes exhibit outstanding cycle performance. This technology offers a promising solution for high-power, low-temperature, and long-cycling Ni-MH batteries.