Fast-charge high-voltage layered cathodes for sodium-ion batteries

Abstract

Sodium-ion batteries have not only garnered substantial attention for grid-scale energy storage owing to the higher abundance of sodium compared with lithium, but also present the possibility of fast charging because of the inherently higher sodium-ion mobility. However, it remains a phenomenal challenge to achieve a combination of these merits, given the complex structural chemistry of sodium-ion oxide materials. Here we show that O3-type sodium-ion layered cathodes (for example, Na_5/6Li_2/27Ni_8/27Mn_11/27Ti_6/27O₂) have the potential to attain high power density, high energy density (260 Wh kg⁻¹ at the electrode level) and long cycle life (capacity retention of 80% over 700 cycles in full cells). The design involves introduction of characteristic P3-structural motifs into an O3-type framework that serves to promote sodium-ion diffusivity and address detrimental transition metal migration and phase transition at a high state of charge. This study provides a principle for the rational design of sodium-ion layered oxide electrodes and advances the understanding of the composition–structure–property relationships of oxide cathode materials.