Synthesis, characterizations, and applications of vacancies-containing materials for energy storage systems

Introduction of vacancies is a widely practiced method to improve the performance of active materials in different energy systems, such as secondary batteries, electrocatalysis, and supercapacitors. Because vacancies can generate abundant localized electrons and unsaturated cations, the incorporation of vacancies will significantly improve the electrical conductivity, ion migration, and provides additional active sites of energy storage materials. This article systematically reviews different methods to generate oxygen, nitrogen, or selenium vacancies, and techniques to characterize these vacancies. We summarize the specific roles that vacancies play for the active materials in each type energy storage device. Additionally, we provide insights into the research progress and challenges associated with the future development of vacancies technology in various energy storage systems.