Layer-structured oxide cathodes have a lot of phases, which can be varied depending on Na ion contents and finally determine their electrochemical properties. Therefore, the off-stoichiometry of layer-structured oxides with the Na ions may differentiate not only their capacities but also the cyclic stabilities, kinetics, and so on, highlighting the importance of Na ion content. However, Na₂CO₃ tends to be irreversibly formed on surface by making use of the Na ions lost from the lattice. Thereby, the O3 phase with stoichiometric Na content changes into the off-stoichiometric P2 phase bringing about significant disadvantages. To address this issue, a thermal activation process is suggested to simultaneously decompose Na₂CO₃ into electrochemically active Na ions and modulate the off-stoichiometric P2 phase into the stoichiometric O3 phase. This study indicates that minimizing the loss of Na ions and maintaining the lattice framework with higher contents of Na ions during the synthesis of Na-incorporating layered cathodes should be a key toward attaining electrochemical superiority.

中文翻译：

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热活化 P2-O3 混合层状阴极对钠离子电池的协同电化学增强

层状结构的氧化物阴极有很多相，可以根据钠离子含量而变化，最终决定其电化学性能。因此，具有 Na 离子的层状结构氧化物的非化学计量不仅可以区分它们的容量，还可以区分循环稳定性、动力学等，突出了 Na 离子含量的重要性。然而，Na ₂ CO ₃倾向于通过利用从晶格中损失的Na离子不可逆地形成在表面上。因此，具有化学计量的 Na 含量的 O3 相转变为非化学计量的 P2 相，带来了显着的缺点。为了解决这个问题，建议采用热活化过程同时分解 Na ₂ CO ₃转化为具有电化学活性的 Na 离子，并将非化学计量的 P2 相调节为化学计量的 O3 相。该研究表明，在合成含钠层状阴极的过程中，最大限度地减少钠离子的损失并保持具有较高钠离子含量的晶格骨架应该是获得电化学优势的关键。