法拉第效率
材料科学
煅烧
过渡金属
电化学
阴极
分析化学(期刊)
锂(药物)
固溶体
金属
碱金属
电极
冶金
物理化学
化学
催化作用
有机化学
内分泌学
医学
生物化学
色谱法
作者
Siham Doubaji,Lu Ma,Habtom Desta Asfaw,Ilyasse Izanzar,Rui Xu,Jones Alami,Jun Lü,Tianpin Wu,Khalil Amine,Kristina Edström,Ismae͏̈l Saadoune
标识
DOI:10.1021/acsami.7b13472
摘要
P2-type NaMO2 sodiated layered oxides with mixed transition metals are receiving considerable attention for use as cathodes in sodium-ion batteries. A study on solid solution (1 – y)P2-NaxCoO2–(y)P2-NaxMn2/3Ni1/3O2 (y = 0, 1/3, 1/2, 2/3, 1) reveals that changing the composition of the transition metals affects the resulting structure and the stability of pure P2 phases at various temperatures of calcination. For 0 ≤ y ≤ 1.0, the P2-NaxCo(1–y)Mn2y/3Niy/3O2 solid-solution compounds deliver good electrochemical performance when cycled between 2.0 and 4.2 V versus Na+/Na with improved capacity stability in long-term cycling, especially for electrode materials with lower Co content (y = 1/2 and 2/3), despite lower discharge capacities being observed. The (1/2)P2-NaxCoO2–(1/2)P2-NaxMn2/3Ni1/3O2 composition delivers a discharge capacity of 101.04 mAh g–1 with a capacity loss of only 3% after 100 cycles and a Coulombic efficiency exceeding 99.2%. Cycling this material to a higher cutoff voltage of 4.5 V versus Na+/Na increases the specific discharge capacity to ≈140 mAh g–1 due to the appearance of a well-defined high-voltage plateau, but after only 20 cycles, capacity retention declines to 88% and Coulombic efficiency drops to around 97%. In situ X-ray absorption near-edge structure measurements conducted on composition NaxCo1/2Mn1/3Ni1/6O2 (y = 1/2) in the two potential windows studied help elucidate the operating potential of each transition metal redox couple. It also reveals that at the high-voltage plateau, all of the transition metals are stable, raising the suspicion of possible contribution of oxygen ions in the high-voltage plateau.
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