Sodium‐ion batteries have gained much attention for their potential application in large‐scale stationary energy storage due to the low cost and abundant sodium sources in the earth. However, the electrochemical performance of sodium‐ion full cells (SIFCs) suffers severely from the irreversible consumption of sodium ions of cathode during the solid electrolyte interphase (SEI) formation of hard carbon anode. Here, a high‐efficiency cathode sodiation compensation reagent, sodium oxalate (Na₂C₂O₄), which possesses both a high theoretical capacity of 400 mA h g⁻¹ and a capacity utilization as high as 99%, is proposed. The implementation of Na₂C₂O₄ as sacrificial sodium species is successfully realized by decreasing its oxidation potential from 4.41 to 3.97 V through tuning conductive additives with different physicochemical features, and the corresponding mechanism of oxidation potential manipulation is analyzed. Electrochemical results show that in the full cell based on a hard carbon anode and a P2‐Na_2/3Ni_1/3Mn_1/3Ti_1/3O₂ cathode with Na₂C₂O₄ as a sodium reservoir to compensate for sodium loss during SEI formation, the capacity retention is increased from 63% to 85% after 200 cycles and the energy density is improved from 129.2 to 172.6 W h kg⁻¹. This work can provide a new avenue for accelerating the development of SIFCs.

中文翻译：

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钠离子电池的高效阴极钠补偿。

钠离子电池由于其低成本和地球上丰富的钠源而在大型固定式能量存储中的潜在应用受到了广泛关注。但是，在硬碳阳极的固体电解质相（SEI）形成过程中，钠离子全电池（SIFC）的电化学性能严重受阴极钠离子不可逆消耗的影响。在此，提出了一种高效的阴极除钠补偿试剂草酸钠（Na ₂ C ₂ O ₄），它既具有400 mA hg ^-1的高理论容量，又具有高达99％的容量利用率。Na ₂ C ₂ O _4的实施通过调节具有不同理化特性的导电添加剂，成功地将其氧化电位从4.41 V降低到3.97 V，从而成功地实现了牺牲钠物质的存在，并分析了相应的氧化电位操纵机理。电化学结果表明，在基于硬碳阳极和P2-Na _2/3 Ni _1/3 Mn _1/3 Ti _1/3 O ₂阴极的完整电池中，Na ₂ C ₂ O ₄作为钠储存剂进行补偿对于SEI形成过程中的钠损失，在200个循环后，容量保持率从63％增加到85％，能量密度从129.2 W h kg ^-1提高到172.6 W h kg ^-1。这项工作可以为加快SIFC的发展提供一条新途径。