Y‑Doped Na2ZrO3: A Na-Rich Layered Oxide as a High-Capacity Cathode Material for Sodium-Ion Batteries

The renewed interest in sodium-ion batteries reflects the persistent concern about the lithium resources that have widespread applications but an uneven distribution, and the overwhelming need for large-scale energy storage. Most exploration has focused on the conventional layered oxides Na x MO2 that stem from lithium-ion cathodes. However, exploring cathode materials with high capacities, long cycle lives, and low costs because of the large ionic radius and high atomic weight of sodium is a great challenge. Here we report a Na-rich layered oxide, yttrium-doped Na2ZrO3, that serves as a cathode material in sodium-ion batteries. This material delivers a large reversible capacity of ∼180 mAh g–1 and a good cycle life with no sign of obvious capacity decay over 1500 cycles along with a low cost. The redox reactivity of oxygen is shown to be involved in the sodium extraction–insertion processes. This work not only provides a cathode contender to conventional layered oxides Na x MO2 but also suggests that broad classes of defective Na-rich layered oxides could be discovered.