Synergetic Anion-Cation Redox Ensures a Highly Stable Layered Cathode for Sodium-Ion Batteries.
Synergetic Anion-Cation Redox Ensures a Highly Stable Layered Cathode for Sodium-Ion Batteries.
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DOI：
10.1002/advs.202105280
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发表时间：
2022-05
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钠离子电池通常被认为是大规模储能的有前途的候选者。层状铁锰氧化物阴极由于其丰富的元素含量和较大的理论容量而受到广泛关注。然而，这些材料通常经历明显的电化学性能下降，由于在连续的钠释放和吸收过程中的Mn溶解和Fe迁移的趋势。本文提出了阴阳离子协同氧化还原的策略，以抑制过度使用过渡金属离子的电化学活性引起的结构劣化，同时实现降低的晶格应变以及上级电化学性能。结果表明，Na0.8Li0.2Fe0.2Mn0.6O2（NLFM）电极具有与传统Mn/Fe基电极不同的高度耐湿气侵蚀性。此外，NLFM电极在循环过程中表现出固溶体行为而没有相变。0.85%的超小体积变化归因于可忽略的锰溶解和不可见的过渡金属迁移。高稳定性的层状结构确保了高达165 mA h g-1的上级可逆容量、优异的倍率性能以及100次循环后超过98.3%的出色容量保持率。这些发现加深了对阴离子和阳离子氧化还原之间协同作用的理解，并为设计钠离子电池的高稳定性层状阴极提供了新的见解。提出了一种阴阳离子协同氧化还原策略来抑制钠离子层状铁锰基阴极的结构劣化。该电极具有与传统电极不同的高抗湿气侵蚀性。此外，该电极在循环过程中表现出固溶体行为而没有相变。0.85%的超小体积变化归因于可忽略的锰溶解和不可见的Fe迁移。高稳定性的分层结构确保了卓越的上级可逆容量和出色的倍率性能。
Sodium‐ion batteries are commonly regarded as a promising candidate in large‐scale energy storage. Layered iron/manganese oxide cathodes receive extensive attentions due to the element abundance and large theoretical capacity. However, these materials usually undergo obvious degradation of electrochemical performance due to the tendency of Mn dissolution and Fe migration during continuous sodium release and uptake. Herein, a strategy of anion–cation synergetic redox is proposed to suppress the structural deterioration originated from overusing the electrochemical activity of transition‐metal ions, and decreased lattice strain as well as superior electrochemical performance are realized simultaneously. Results show that the Na0.8Li0.2Fe0.2Mn0.6O2 (NLFM) electrode is highly resistant to the erosion of moisture that is distinct from the traditional Mn/Fe‐based electrodes. Moreover, the NLFM electrode demonstrates solid solution behavior without phase transition during cycles. The ultra‐small volume change of 0.85% is ascribed to the negligible manganese dissolution and invisible transition‐metal migration. The high‐stable layered structure assures superior reversible capacity of ≈165 mA h g–1, excellent rate capability, and splendid capacity retention of over 98.3% with 100 cycles. The findings deepen the understanding of the synergy between anion and cation redox and provide new insights to design the high‐stable layered cathode for sodium‐ion batteries. A strategy of anion–cation synergetic redox is proposed to suppress the structural deterioration of sodium‐ion layered Fe/Mn‐based cathodes. The electrode is of high resistance to the erosion of moisture that is distinct from the traditional electrodes. Moreover, the electrode demonstrates solid solution behavior without phase transition during cycles. The ultra‐small volume change of 0.85% is ascribed to the negligible manganese dissolution and invisible Fe migration. The high‐stable layered structure assures superior reversible capacity and excellent rate capability.