Iron-based polyanionic compounds exhibit promising potential as commercial cathode materials for sodium-ion batteries (SIBs) due to their abundant resources, low cost, environmental friendliness, and reliability. However, they still encounter challenges such as limited energy density, inadequate ionic/electronic conductivity, and sluggish Na⁺ diffusion kinetics. Herein, the Na storage performance of an iron-based pyrophosphate cathode is enhanced through a dual-strategy involving in situ carbon-coating and nanoengineering. Uniform carbon-coated Na_3.12Fe_2.44(P₂O₇)₂/C (NFPO/C) nanoflakes are synthesized via solid-state reaction in a molten surfactant–paraffin medium. Based on the synergistic effects of surface coating and nanotechnology, NFPO/C nanoflakes demonstrate excellent kinetic performance and remarkable structural reversibility during Na storage. Consequently, the NFPO/C cathode exhibits a high reversible capacity of 101.6 mA h g⁻¹ at 1C and demonstrates exceptional cycling stability, retaining 79% of its capacity after 3700 cycles at 2C. Furthermore, the full cell assembled using an NFPO/C cathode and a hard carbon (HC) anode demonstrates a high reversible capacity of 92 mA h g⁻¹ at 1C and exhibits excellent cycling stability with 72% capacity retention after 200 cycles at 1C. These findings suggest that the iron-based pyrophosphate cathode holds great promise as a potential candidate for commercial SIBs.

中文翻译：

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碳涂层和纳米工程的双重策略可在铁基焦磷酸盐阴极中实现可逆且持久的钠存储


铁基聚阴离子化合物由于其资源丰富、成本低廉、环境友好和可靠，作为钠离子电池（SIB）的商业正极材料具有广阔的潜力。然而，它们仍然面临能量密度有限、离子/电子电导率不足以及Na ⁺扩散动力学缓慢等挑战。在此，通过原位碳涂层和纳米工程的双重策略增强了铁基焦磷酸盐阴极的钠存储性能。通过在熔融表面活性剂-石蜡介质中的固态反应合成均匀碳包覆的Na _3.12 Fe _2.44 (P ₂ O ₇ ) ₂ /C (NFPO/C) 纳米片。基于表面涂层和纳米技术的协同效应，NFPO/C纳米片在钠存储过程中表现出优异的动力学性能和显着的结构可逆性。因此，NFPO/C正极在1C下表现出101.6 mA hg ^-1的高可逆容量，并表现出出色的循环稳定性，在2C下3700次循环后仍保留79%的容量。此外，使用NFPO/C阴极和硬碳（HC）阳极组装的全电池在1C下表现出92 mA hg ^-1的高可逆容量，并在1C下200次循环后表现出优异的循环稳定性，容量保持率为72%。这些发现表明，铁基焦磷酸盐阴极作为商业 SIB 的潜在候选者具有巨大的前景。