Li-ion batteries from an electronic structure viewpoint: From anionic redox to structural stability

Rechargeable Li-ion batteries must be systematically designed using durable, high-performance components to warrant a sustainable redox activity upon charge/discharge cycles. Investigating structure-property relationship is an inevitable part of research strategies concerning electrodes and their interfaces with electrolytes. Here, principles of atomic orbital overlap and molecular orbital in electrodes is applied to discuss the structure-property relationship. For instance, considering molecular orbital diagrams, the debate is over the dominant charge compensation mechanism of electrodes to ascertain to what extent an obtained long-lasting capacity is contingent on either transition metal or oxygen redox reaction. Inter-atomic distances and distortions in symmetry are described as the factors governing the structural integrity of electrodes. Internal reactions are discussed in context of energy band structures of active materials under cycling due to their significance for battery materials development. Chemical and structural stability of conventional cathode families including high-voltage sulfur cathodes are briefly discussed from an electronic structure viewpoint. Additionally, this study accentuates the assessment of electronic structure within ceramic solid electrolytes and their interfaces with the Li-metal anode, along with common cathodes, throughout cycling. Also, it addresses the local variations in electronic structure occurring within the grain boundaries of polycrystalline ceramic electrolytes, which may contribute to internal structural instability. Importance of incorporating electronic structures, apart from chemical composition and crystal structure to design battery materials is highlighted to provide a novel insight into design of new class of materials.