(Invited) Nanostructured High-Capacity Positive Electrode Materials for Li-Ion Batteries

Abstract

In the past decade, lithium-enriched compounds, Li2 MO3 (M = Mn4+, Ru4+ etc.), have been extensively studied for high-capacity positive electrode materials of Li-ion batteries. Large reversible capacities originate from charge compensation by anions species (anionic redox) coupled with partial cationic redox of transition metal ions. Recently, many cation-disordered rocksalt oxides have been proposed as a new series of electrode materials, which utilize reversible anionic redox. Nevertheless, insufficient electrode kinetics for the cation-disordered rocksalt system limits its use for practical applications. One simple strategy is synthesizing nanosized materials to overcome a problem of electrode kinetics (for electrons, holes and ions), and electrode kinetics are significantly improved through nanosizing even for a non-lithium-excess and stoichiometric system.1) Moreover, Nanosized Li/Na-excess oxides also deliver large reversible capacities at room temperature,2-4) which shows much better electrode kinetics compared with as-prepared samples.From these findings, we discuss the advantages/disadvantages of “nanostructured” electrode materialsto develop high energy advanced Li-ion batteries.References1) Sato et al., and N. Yabuuchi., Journal of Materials Chemistry A, 6, 13943 (2018).2) Kobayashi et al., and N. Yabuuchi, Small, 15, 1902462 (2019).3) Kobayashi et al., and N. Yabuuchi, Materials Today, 37, 43 (2020).4) Sawamura et al., and N. Yabuuchi, ACS Central Science, 6, 2326 (2020).