Enhanced electrochemical performance in an aluminium doped δ-MnO2 supercapacitor cathode: experimental and theoretical investigations

One of the biggest challenges faced by the layered manganese oxide MnO2 used as a supercapacitor cathode is the capacity fading caused by chemo-mechanical degradation and/or structural transformation occurring in the discharging/charging process. Here, based on systematical experimental measurements and theoretical calculations, we show that both the stability and rate performance of the delta-MnO2 supercapacitor cathode can be significantly enhanced by Al doping. Compared with pure delta-MnO2, Al doping (delta-Al0.06MnO2) clearly improves the specific capacitance (7% enhancement at 0.1 mA cm(-2)) and cycling stability (12% enhancement after 5000 cycles) simultaneously. These improvements can be attributed to the enhanced electronic transport and formation of more active sites, which are introduced by Al doping. Additionally, our calculations demonstrate that the doped systems (Al atoms located at Mn or O sites) show smaller surface energies than that of pure delta-MnO2, which hinders side reactions or structure transformations and leads to a better cycling lifetime. Our work gives a comprehensive understanding of the impacts on the performance of delta-MnO2 introduced by Al doping, and provides a feasible scheme to study the electrochemical mechanism of metal-doped delta-MnO2.

Automated summary

This study demonstrates that Al doping can significantly enhance the specific capacitance and cycling stability of delta-MnO2 supercapacitor cathode, attributed to the introduction of more active sites and improved electronic transport. Additionally, calculations show that doped systems have smaller surface energies, leading to better cycling lifetime.