An ultrastable anode for long-life room-temperature sodium-ion batteries

Sodium-ion batteries are important alternative energy storage devices that have recently come again into focus for the development of large-scale energy storage devices because sodium is an abundant and low-cost material. However, the development of electrode materials with long-term stability has remained a great challenge. A novel negative-electrode material, a P2-type layered oxide with the chemical composition Na_2/3Co_1/3Ti _2/3O₂, exhibits outstanding cycle stability (ca. 84.84% capacity retention for 3000 cycles, very small decrease in the volume (0.046%) after 500 cycles), good rate capability (ca. 41% capacity retention at a discharge/charge rate of 10C), and a usable reversible capacity of about 90 mAhg^-1 with a safe average storage voltage of approximately 0.7 V in the sodium half-cell. This P2-type layered oxide is a promising anode material for sodium-ion batteries with a long cycle life and should greatly promote the development of room-temperature sodium-ion batteries.