Oxygen-vacancy europium-doped MnO2 ultrathin nanosheets used as asymmetric supercapacitors

In term of supercapacitors application, MnO2 has been recognized as a popular pseudocapacitive material on account of its environmental friendliness, cost inexpensive, plentiful abundance and high theoretical capacitance. However, its inherently low conductivity and structural instability lead to low specific capacitance and short cycle life, which greatly limit its development. Rare-earth doping can manipulate the size, shape, and crystallographic phase of doped nanomaterials. For the sake of hoisting the supercapacitors performance of MnO2, herein, we synthesized europium-doping MnO2 (Eu5%-MnO2) ultrathin nanosheets (3.4 nm) possessing rich oxygen vacancies via a facile co-precipitation strategy. The specific capacitance of Eu5%-MnO2 at 1 A g−1 is 361.2 F g−1 and remains 100% after 10,000 cycles, outperforming of MnO2 nanosheets (198 F g−1, 82.8%). The reason of enhancing performance may be mainly correlation to the heighten conductivity, boosted surface reactivity and electrochemical active sites. The assembled Eu5%-MnO2//AC device at 1 A g−1 can reach 63.36 F g−1 with high voltage of 3 V and exerts 19.8 Wh kg−1 of energy density when the power density is 373.2 W kg−1. This synthesis technique is a simple and convenient means for the development of high-performance MnO2-based energy storage electrodes.