Extrinsic pseudocapacitance: Tapering the borderline between pseudocapacitive and battery type electrode materials for energy storage applications

Extrinsic pseudocapacitance, which can also be referred to as induced pseudocapacitance, is, at present, one of the most widely explored fields in energy storage. Extrinsic pseudocapacitive mechanism can be imparted to an otherwise diffusion-controlled faradaic energy storage material by external methods like size engineering, compositional modification, doping, anion intercalation, and morphological modifications. As a significant mechanism that plays a borderline role between battery-type and pseudocapacitive nature of energy storage, extrinsic pseudocapacitance tends to narrow down the boundary between these conventionally diverse systems, which in turn would contribute a lot to the development of hybrid energy storage technologies. For effective utilization in upcoming energy storage technologies, a critical analysis on the effect of this mechanism on reported devices shall turn into a valid account. This review gives a detailed insight into extrinsic pseudocapacitance, its significance, and recently reported materials, methods, and devices. The future outlook and challenges in transforming extrinsic pseudocapacitive mechanisms into a promising strategy for next-generation energy storage devices are also discussed.

Automated summary

Extrinsic pseudocapacitance is a widely explored field in the energy storage industry. It can be imparted to diffusion-controlled energy storage materials through external methods, which helps narrow the boundary between battery-type and pseudocapacitive systems. This review provides insight into the significance of extrinsic pseudocapacitance, as well as recently reported materials, methods, and devices. The future outlook and challenges in transforming this mechanism into next-generation energy storage devices are also discussed.