Advanced asymmetric supercapacitors with a squirrel cage structure FeO@carbon nanocomposite as a negative electrode.

Carbon materials have been used as negative electrodes for supercapacitor applications; nevertheless, owing to the low capacitance, they have limited ability to enhance the supercapacitor electrochemical properties. Here, we employ a facile chemical precipitation method for preparing a squirrel cage structure FeO@carbon nanocomposite. In this architecture, the carbonized crosslinked bovine serum albumin (C) will play critical roles, serving as a skeleton for the deposition of FeO and a transportation pathway like "high-speed rail" for electrons, maintaining the structural stability as well as accommodating the volume expansion of FeO and facilitating electron transportation and the electrolyte ion diffusion.