The Unified Electrochemical Band Diagram Framework: Understanding the Driving Forces of Materials Electrochemistry

Abstract Recent work that establishes a picture of the driving forces that govern material transformations and degradation in electrochemical environments to enable the ab initio design of electrochemical materials is highlighted. Select prototype systems are used to describe how the interplay between materials properties such as crystal field splitting, band edge energies, surface termination, material length scale, dielectric constant, and isoelectric point, and electrolyte properties such as pH and ion type, impacts electrochemical behavior—i.e., redox potentials, reaction enthalpies, reactivity, and decoupled ionic/electronic processes. Ab initio modeling of charged defects and intercalants within the grand canonical unified electrochemical band‐diagram (UEB) framework is shown to enable the quantitative prediction of electrochemical materials behavior. UEB combines electrochemical theory, charged defect theory, and band diagram descriptions and can be used both for materials discovery and development. First, a pedagogical description of the UEB framework is presented, and then the application of this framework to reveal mechanisms for high rate electronic charge storage in cation incorporated α‐MnO 2 and λ‐MnO 2 , high desalination efficiency of thin‐film NaMn 4 O 8 , and the flat charge/discharge profile of FePO 4 is reviewed. Finally, new prospects for the application of the UEB framework to electrolyte design, interfacial engineering, and catalysis are suggested.