Self-adaptive layered oxide cathodes driven by charge reconfiguration for sodium-ion batteries

Layered oxide cathodes have attracted worldwide attention due to environmentally friendliness, structural diversity, and economic benefits. However, poor long-term cycling and unsatisfactory rate performance hinder the practical application. Hence, an oxide cathode with self-adaptive volume has been designed, achieving stable capacity retention of 82% after 1000 cycles at 2 C. The enhanced long-term performance is attributed to its dynamically adjustable volume reducing the acceleration of stress, enabled by a tunable interlayer distance that expands at the beginning of the charging process and then compresses at the highest voltage. Uniform electric field distribution is depicted by 4-dimensional scanning transmission electron microscopy showing even Coulombic interactions between the oxide layers leading to high mechanical integrity. Such self-adaptable behavior originates from the reduced repulsive force between interlayered oxygen due to the charge reconfiguration of intralayer oxygen and transition metal ions. Additionally, the charge compensation behavior is detected by in situ X-ray absorption spectra, which would be beneficial to high-rate performance. The self-adaptive volume change driven by charge reconfiguration provides a pathway toward durable materials for sustainable sodium-ion energy storage.