A P2/P3 Biphasic Layered Oxide Composite as a High‐Energy and Long‐Cycle‐Life Cathode for Potassium‐Ion Batteries

Layered transition metal oxides are extensively considered as appealing cathode candidates for potassium‐ion batteries (PIBs) due to their abundant raw materials and low cost, but their further implementations are limited by slow dynamics and impoverished structural stability. Herein, a layered composite having a P2 and P3 symbiotic structure is designed and synthesized to realize PIBs with large energy density and long‐term cycling stability. The unique intergrowth of P2 and P3 phases in the obtained layered oxide is plainly characterized by X‐ray diffraction refinement, high‐angle annular dark field and annular bright field‐scanning transmission electron microscopy at atomic resolution, and Fourier transformation images. The synergistic effect of the two phases of this layered P2/P3 composite is well demonstrated in K+ intercalation/extraction process. The as‐prepared layered composite can present a large discharge capacity with the remarkable energy density of 321 Wh kg−1 and also manifest excellent capacity preservation after 600 cycles of K+ uptake/removal. A biphasic P2/P3‐K0.7Mn0.67Ni0.33O2 composite is proposed for potassium‐ion batteries with large energy density and long‐term cycling stability and characterized by XRD refinement, HAADF and ABF‐STEM, and Fourier transformation. This P2/P3 intergrown layered composite can manifest a high energy density of 321 Wh kg−1 and also exhibit excellent capacity preservation during 600 cycles of K+ uptake/release.