Inhibiting the P2-O2 phase transition of P2-Na0.67Ni0.33Mn0.67O2 via high-valence tungsten doping for sodium-ion batteries

P2-type layered oxide cathode materials have attracted extensive attention due to their simple preparation, high specific capacity, adjustable voltage range, and high packing density. However, the harmful phase transitions that occur at high voltage severely limit their practical application. Herein, a novel high-valence tungsten doped P2-Na0.67Ni0.33Mn0.67O2 cathode material was prepared using the sol-gel method. Through diffusion kinetics analysis and in situ X-ray diffraction (in situ XRD), it has been proven that W6+ not only enhances the Na+ diffusion coefficient but also reduces the P2-O2 phase transition. The optimized NNMO-W1% delivers a high discharge specific capacity of 163 mAh<middle dot>g-1 at 0.1C, and the capacity retention rate is as high as 77.6% after 1000 cycles at 10C. This is mainly due to that W6+ enters the lattice, optimizing the arrangement of primary particles. This work sheds light on the design and construction of high-performance layered oxides cathode materials. P2(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)-(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)P2-Na0.67Ni0.33Mn0.67O2(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)X(sic)(sic)(sic)(sic), (sic)(sic)W6+(sic)(sic)(sic)(sic)(sic)Na+(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)P2-O2(sic)(sic)(sic).(sic)(sic)(sic)(sic)NNMO-W1%(sic)0.1C(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)163 mAh<middle dot>g-1, (sic)(sic)(sic)10C(sic)(sic)(sic)1000(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)77.6%.(sic)(sic)(sic)(sic)(sic)(sic)W6+(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).