Excellent Electrochemical Performance of Potassium Ion Capacitor Achieved by a High Nitrogen Doped Activated Carbon - Chen, Zhi; Li, Wenlei; Yang, Jian; Liao, Jiaxuan; Chen, Cheng; Song, Yaochen; Ali Shah, Syed Abbas; Xu, Ziqiang; Wu, Mengqiang (Journal of the Electrochemical Society, 2020)