Na-ion batteries (NIBs) are promising for grid-scale energy storage applications. However, the lack of Co, Ni-free cathode materials has made them less cost-effective. In this work, Mg²⁺ is successfully utilized to activate the oxygen redox reaction in earth-abundant Fe/Mn-based layered cathodes to achieve reversible hybrid anionic and cationic redox capacities. A high first charge capacity of ≈210 mAh g⁻¹ with balanced charge–discharge efficiency is achieved without O-loss, showing a promising energy cost of $2.02 kWh⁻¹. Full cell against hard carbon anode without pre-sodiation shows energy density exceeding ≈280 Wh kg⁻¹ with a decent capacity retention of 85.6% after 100 cycles. A comprehensive analysis of the charge compensation mechanisms and structural evolution is conducted. Voltage and capacity loss resulting from partially reversible Fe³⁺ migration to the Na layer is confirmed, shedding light on further improvements for low-cost NIB cathodes in application scenarios.

中文翻译：

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地球储量丰富的 Na-Mg-Fe-Mn-O 阴极，具有可逆混合阴离子和阳离子氧化还原作用

钠离子电池（NIB）在电网规模的储能应用中前景广阔。然而，缺乏不含钴、镍的正极材料使其成本效益较低。在这项工作中，Mg ²⁺被成功地用来激活地球上丰富的铁/锰基层状阴极中的氧氧化还原反应，以实现可逆的混合阴离子和阳离子氧化还原能力。^{在没有 O 损失的情况下实现了约 210 mAh g -1}的高首次充电容量和平衡的充放电效率，显示出 2.02 kWh ^-1美元的有前景的能源成本。未经预钠化的硬碳阳极的全电池显示能量密度超过 ≈280 Wh kg ⁻¹100次循环后容量保持率为85.6%。对电荷补偿机制和结构演变进行了全面分析。^{部分可逆的 Fe 3+}迁移到 Na 层导致的电压和容量损失得到证实，这为低成本 NIB 阴极在应用场景中的进一步改进提供了线索。