Mao Zhifei, Wang Rui, He Beibei, Gong Yansheng, Wang Huanwen
Faculty of Material Science and Chemistry, China University of Geosciences, Wuhan, 430074, China.
Small. 2019 Sep;15(36):e1902466. doi: 10.1002/smll.201902466. Epub 2019 Jul 22.
Sodium-vanadium fluorophosphate (Na V O (PO ) F , NVPF, 0 ≤ x ≤ 1) is considered to be a promising Na-storage cathode material due to its high operation potentials (3.6-4 V) and minor volume variation (1.8%) during Na -intercalation. Research about NVPF is mainly focused on powder-type samples, while its ordered array architecture is rarely reported. In this work, large-area and uniform Na (VO) (PO ) F cuboid arrays are vertically grown on carbon nanofiber (CNF) substrates for the first time. Owing to faster electron/ion transport and larger electrolyte-electrode contact area, the as-prepared NVPF array electrode exhibits much improved Na-storage properties compared to its powder counterpart. Importantly, a quasi-solid-state sodium-ion hybrid capacitor (SIHC) is constructed based on the NVPF array as an intercalative battery cathode and porous CNF as a capacitive supercapacitor anode together with the P(VDF-HFP)-based polymer electrolyte. This novel hybrid system delivers an attractive energy density of ≈227 W h kg (based on total mass of two electrodes), and still remains as high as 107 Wh kg at a high specific power of 4936 W kg , which pushes the energy output of sodium hybrid capacitors toward a new limit. In addition, the growth mechanism of NVPF arrays is investigated in detail.
氟磷酸钠钒（NaVOPO₄Fₓ，NVPF，0≤x≤1）因其较高的工作电位（3.6 - 4V）以及在钠离子嵌入过程中较小的体积变化（1.8%），被认为是一种很有前景的钠存储阴极材料。关于NVPF的研究主要集中在粉末型样品上，而其有序阵列结构鲜有报道。在这项工作中，首次在碳纳米纤维（CNF）基底上垂直生长出大面积且均匀的Na(VO)(PO₄)F长方体阵列。由于具有更快的电子/离子传输速率以及更大的电解质 - 电极接触面积，所制备的NVPF阵列电极相较于其粉末对应物展现出显著改善的钠存储性能。重要的是，基于NVPF阵列作为嵌入型电池阴极、多孔CNF作为电容性超级电容器阳极以及基于P(VDF - HFP)的聚合物电解质，构建了一种准固态钠离子混合电容器（SIHC）。这种新型混合系统具有约227 W h kg⁻¹的诱人能量密度（基于两个电极的总质量），并且在4936 W kg⁻¹的高比功率下仍高达107 Wh kg⁻¹，这将钠混合电容器的能量输出推向了一个新的极限。此外，还详细研究了NVPF阵列的生长机制。
