Inorganic pseudocapacitors often select synthetic solid materials as electrode materials, which show low utilization of pseudocapacitive metal cations. We reported the crystallization transformation of YbCI3 pseudocapacitor electrodes in alkaline electrolytes, which can show high cation utilization ratio. The electrochemical reactive YbOOH colloids were crystallized through the chemical coprecipitation and Faradaic redox reactions. The effect of crystallization kinetics on electrochemical performances of YbCI3 pseudocapacitor was studied. YbCI3 pseudocapacitor can show ultrahigh specific capacitance of 2210 F/g, where the commercial YbCl3 salts were used directly as pseudocapacitor electrodes in an aqueous electrolyte neglecting the complex synthesis procedures. The present strategy provides a novel route to crystallize electrochemical active compounds with unusual reactivity toward Faradaic redox reaction. The development of ion-based pseudocapacitors can advance the understating of the redox mechanism of active cations. (C) 2014 Elsevier Inc. All rights reserved.