Achieving high-energy-density lithium-ion batteries through oxygen redox of cathode: From fundamentals to applications

Constructions of high-energy-density lithium-ion batteries (LIBs) largely rely on the breakthrough of cathode materials. In contrast to conventional layered oxide cathodes (LiTMO2, TM denotes transition metal), invoking oxygen redox by increasing the chemical ratio of Li/O in oxide cathode can further boost the development of new types of high-capacity cathodes which theoretically enable the realization of LIBs of above 400 Wh/kg and are even attainable for 600 Wh/kg, meeting the future demands of various application scenarios for high energy density, such as electrical aircraft. However, the revolution of high-capacity cathodes is far from the realistic elevation of cell-level energy density and their practical applications in LIBs, which involves the considerations of other indispensable metrics in terms of both materials and technologies. Therefore, in this perspective, an in-depth discussion from fundamentals to applications of oxygen-based cathode materials is provided. First, we briefly summarized the representative investigations on oxygen redox mechanisms. Moreover, intrinsic properties of materials based on oxygen redox are multidimensionally evaluated. Furthermore, cell-level gravimetric energy density, potentials for practical applications, and possible design strategies are critically analyzed.