PUB-2018-SCS

Solubility contrast strategy for enhancing intercalation pseudocapacitance in layered MnO2 electrodes

"Yun-Pei Zhu, Chuan Xia, Yongjiu Lei, Nirpendra Singh, Udo Schwingenschlögl, Husam N. Alshareef" Solubility contrast strategy for enhancing intercalation pseudocapacitance in layered MnO2 electrodes
​Nano Energy 56 (2019) 357–364​
Yun-Pei Zhu, Chuan Xia, Yongjiu Lei, Nirpendra Singh, Udo Schwingenschlögl, Husam N. Alshareef​
Salt effect, Oxygen vacancy, Nanostructure control, Modified pseudocapacitance
2018
Pseudocapacitance is generally associated with either surface redox reactions or ion intercalation processes without a phase transition. Typically, these two mechanisms have been independently studied, and most works have focused on optimizing one or the other in different material systems. Here we have developed a strategy based on solubility contrast, in which the contribution from the two capacitive mechanisms is simultaneously optimized. Taking layered birnessite MnO2 as a model, controllable nanostructures and oxygen vacancies are achieved through a simple coprecipitation process. Simultaneously controlling crystallite size and defect concentration is shown to enhance the charging-discharging kinetics together with both redox and intercalation capacitances. This synergistic effectresults from enhanced ionic diffusion, electronic conductivity, and large surface-to-volume ratio. In addition, considerable cycling durability is achieved, resulting from improved framework strength by defect creation and the absence of proton (de)intercalation during discharge/charge. This work underscores the importance of synergistically regulating nanostructure and defects in redox-active materials to improve pseudocapacitive charge storage.