共沉淀中热力学耦合对正极材料电化学性能的影响

以共沉淀法制备钠离子层状氧化物正极材料NaNi_0.4Mn_0.4Fe_0.2O₂，采用Al³⁺有效控制和平衡共沉淀反应的过程.考察了加入Al元素带来的热力学耦合效应及对正极材料电化学性能的影响.结果表明，在Mn²⁺，Ni²⁺和Fe²⁺离子共存的环境中，由于Al³⁺更高的过饱和度和更负的吉布斯自由能变(ΔG)所产生的热力学耦合效应，显著改变了溶液离子之间的沉淀驱动力，加速Ni²⁺和Mn²⁺的沉淀并抑制Fe³⁺的沉淀.Na［Ni_0.4Mn_0.4Fe_0.2］_0.995Al_0.005O₂正极材料表现出优异的电化学性能，这归因于引入Al³⁺制备得到高质量的前驱体(［0.4MnCO₃·0.4NiCO₃·0.2Fe(OH)₃］_0.995·0.005Al(OH)₃).

Coupling Effects of Thermodynamics in Co-precipitation on Electrochemical Performance of Cathode Materials

The sodium ion layered oxide cathode material NaNi_0.4Mn_0.4Fe_0.2O₂ was synthesized by the co-precipitation method， and Al³⁺was used to effectively control and balance the co-precipitation reaction process. The thermodynamic coupling effect brought by the addition of Al element and its influence on electrochemical performance of cathode materials were investigated. In an environment where Mn²⁺， Ni²⁺ and Fe³⁺ ions coexist， owing to the thermodynamic coupling effect， the superior high supersaturation of Al³⁺ and the more negative change in the Gibbs free energy(ΔG)can efficiently changes the precipitation driving force between the solution ions， accelerating the precipitation of Ni²⁺and Mn²⁺ ions and inhibiting the precipitation of Fe³⁺ ions. The obtained Na［Ni_0.4Mn_0.4Fe_0.2］_0.995Al_0.005O₂ cathode material has demonstrated excellent electrochemical performance which can be attributed to the high quality precursor(［0.4MnCO₃·0.4NiCO₃·0.2Fe(OH)₃］_0.995·0.005Al(OH)₃) brought about by the introduction of Al³⁺.