Air-Stable and High-Voltage Layered P3-Type Cathode for Sodium-Ion Full Battery

The development of highly efficient and stable cathodes for sodium-ion batteries (SIBs) is strategically critical to achieving large-scale electrical energy storage. Creating air-stable and high-voltage layered cathodes for sodium-ion full batteries still remains a challenge. Herein, we describe a rational design and preparation of a stable P3-Na_2/3Ni_1/4Mg_1/12Mn_2/3O₂ cathode. The cathode displays a satisfactory working voltage of 3.6 V and excellent cyclic stability over 100 cycles at a 1 C rate without obvious capacity fading. The results of ex situ X-ray diffraction (XRD) demonstrate that the P3-type structure is well retained even when charged to 4.4 V. Furthermore, the structural characterization by XRD Rietveld refinement, scanning electron microscopy, and electrochemical testing certifies that the cathode maintains its structure commendably even when soaked in water for 12 h. In particular, the P3- Na_2/3Ni_1/4Mg_1/12Mn_2/3O₂∥hard carbon full battery exhibits a desired competitively high voltage of 3.45 V and an attractive energy density of up to 412.2 W h kg^-1 based on the cathode. The comprehensive results achieved by the specially designed strategy provide guidance toward the exploration of stable cathodes in the application of SIBs as modern energy-storage devices.