Hybrid energy storage devices: Advanced electrode materials and matching principles

Hybrid energy storage devices (HESDs) combining the energy storage behavior of both supercapacitors and secondary batteries, present multifold advantages including high energy density, high power density and long cycle stability, can possibly become the ultimate source of power for multi-function electronic equipment and electric/hybrid vehicles in the future. In this review, the recent progress made in the field of HESDs, with the main focus on the electrode materials and the matching principles between the positive and negative electrodes are critically reviewed. In particular, the classification and new progress of HESDs based on the charge storage mechanism of electrode materials are re-combed. The newly identified extrinsic pseudocapacitive behavior in battery type materials, and its growing importance in the application of HESDs are specifically clarified. Prospects and the challenges for HESDs in the development of suitable electrode material and a comprehensive understanding on the matching principle are also discussed.