Pseudocapacitive oxide materials for high-rate electrochemical energy storage

TLDR

Electrochemical energy storage devices aim for high energy or high power density, yet there is a growing need for materials that combine both; pseudocapacitance via surface redox reactions can achieve high energy density at high rates. The study focuses on the pseudocapacitive properties of transition metal oxides and reviews the most relevant materials in aqueous and non‑aqueous electrolytes. The authors introduce pseudocapacitance, describe its electrochemical features, review key materials, and outline major challenges and future outlook. The paper identifies major challenges for pseudocapacitive materials and proposes a future outlook.

Abstract

Electrochemical energy storage technology is based on devices capable of exhibiting high energy density (batteries) or high power density (electrochemical capacitors). There is a growing need, for current and near-future applications, where both high energy and high power densities are required in the same material. Pseudocapacitance, a faradaic process involving surface or near surface redox reactions, offers a means of achieving high energy density at high charge–discharge rates. Here, we focus on the pseudocapacitive properties of transition metal oxides. First, we introduce pseudocapacitance and describe its electrochemical features. Then, we review the most relevant pseudocapacitive materials in aqueous and non-aqueous electrolytes. The major challenges for pseudocapacitive materials along with a future outlook are detailed at the end.