Dual-Ion Stabilized Layered Structure of OVO for Zero-Strain Potassium Insertion and Extraction

Potassium-ion batteries (KIB) have similar energy storage mechanism with lithium-ion battery, but the potassium (K) resource is rich, which shows great potential for large-scale energy storage system. Recently, the anode materials of KIB studied mainly include carbon materials, transition metal oxides, and alloy materials. The amorphous hard carbon shows the best comprehensive performance, but its intercalation potential is close to 0 V (versus K⁺ /K), which is easy to cause K dendrite and brings security risks. The oxide materials have high capacity but high intercalation potential, low first cycle efficiency, and unstable cycle. Here, based on the understanding of the K intercalation mechanism of vanadium oxides, a novel zero strain anode material with layered structure of dual-ions (Na⁺ /K⁺ ) is designed (NaK(VO₃ )₂ V₂ O₅ ). The introduction of Na/K ion contributed to the transmission and further stabilized the structure. It has an excellent rate performance (10 A g^-1 , up to 25 000th cycle), and its special K storage mechanism and zero-strain characteristics are revealed for the first time by ex situ scanning electron microscope, X-ray powder diffraction, X-ray photoelectron spectroscopy, and other test methods. Considering the excellent performance endowed by these unique inherent properties, NaK(VO₃ )₂ V₂ O₅ shows great potential for commercial anode materials and may promote the innovation of KIB.