Recent advances and fundamentals of Pseudocapacitors: Materials, mechanism, and its understanding

•Historic evolution of pseudocapacitors: Concept, theory, and mechanism is discussed.•Fundamentals of Pseudocapacitors: intrinsic and extrinsic pseudocapacitors with clear distinction with those of battery like material is discussed.•High-rate performance can be achieved by employing a faceted structure.•Designing strategy for next generation materials for achieving high capacitance, high-rate, long-cyclability and several properties is discussed.•Novel next generation materials were discussed.