Cr³⁺-doped α-MnO₂ electrode with high specific capacitance and ultra-long cycle life

In the realm of energy storage, α-MnO₂-based supercapacitors exhibit salient features such as elevated specific capacitance and pronounced safety in aqueous electrolytes. However, the inherent Jahn-Teller effect compromises long-term cycling stability. This study investigates the mitigating impact of Cr³⁺ doping on the Jahn-Teller effect, culminating in a marked enhancement of electrode cycling resilience. After 10,000 cycles of charging and discharging (5A/g), a remarkable capacitance retention rate of 107.3 % was observed, while the capacitance retention of the undoped sample was only 83.4 %. Experimental and computational findings revealed that trivalent chromium (Cr(III)) ions effectively infiltrated the α-MnO₂ lattice, replacing Mn(III) ions and resulting in the formation of [CrO₆] octahedral units. These units serve as anchoring points during electrode cycling, thereby improving material stability. In summary, this study offers a viable solution to address the issue of poor cycling stability in manganese-based energy storage materials.