Designing Functional Insertion Materials for Practical Battery Applications

Abstract

Energy storage technology is indispensable, and Li-ion batteries are currently widely used as power sources for portable electronics and automobile applications. The Li-ion battery market for electric vehicles has expanded rapidly over the past decade. High-energy Ni-rich electrode materials, such as LiNi_0.8Co_0.1Mn_0.1O₂, and cost-effective Fe-based materials, such as LiFePO₄, are commonly employed as positive electrode materials for electric vehicles. In this article, recent research progress and design strategies for positive electrode materials are summarized. Defect engineering has proven effective in enhancing electrode reversibility, enabling the development of high-performance, pure Ni-based layered materials. Furthermore, a Co-/Ni-free Mn-based Li insertion material with a domain structure and optimum surface area has been successfully synthesized. The electrode reversibility of cation-disordered rocksalt oxides containing V and Ti ions is also significantly improved through the structural defect enrichment and increased surface area. Highly concentrated electrolyte solutions, which possess high oxidation tolerance and reduced solubility for transition metal ions, further contribute to enhanced reversibility of these electrode materials. Similarly, the electrode reversibility of Mn-based Na insertion materials is greatly improved by using highly concentrated electrolyte solutions, due to the suppression of Mn dissolution. The practical feasibility of these Li/Na insertion materials is also discussed based on these findings.