Faculty of Materials Science and Chemistry, China University of Geosciences (Wuhan), Wuhan 430074, China.
Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China.
Nanoscale. 2023 Feb 16;15(7):3345-3350. doi: 10.1039/d2nr06602e.
Polyanion-type phosphate materials with Na-super-ionic conductor structures are promising for next-generation sodium-ion battery cathodes, although the intrinsically low electroconductivity and limited energy density have restricted their practical applications. In this study, we put forward substituting an inert phosphate with a redox-active silicate to improve the energy density and intrinsic electroconductivity of polyanion-type phosphate materials, thus enabling an advance in sodium-ion battery cathodes. As a proof of concept, some of the phosphate of NaV(PO) was replaced by silicate to fabricate NaV(PO)(SiO), which exhibited a higher average discharge voltage of 3.36 V and a higher capacity of 115.8 mA h g than pristine NaV(PO) (3.31 V, 109.6 mA h g) at 0.5 C, therefore improving the energy density. Moreover, the introduced silicate enhanced the intrinsic electroconductivity of NaV(PO) materials, as confirmed by both theoretical simulation and electrochemical measurements. After pairing with a commercial hard carbon anode, the optimized NaV(PO)(SiO) cathode enabled a stable-cycling full cell with 90.1% capacity retention after 300 cycles at 5 C and a remarkable average coulombic efficiency of 99.88%.
具有钠离子超导体结构的聚阴离子型磷酸盐材料是下一代钠离子电池正极的理想选择，尽管其本征电导率低和能量密度有限，限制了它们的实际应用。在这项研究中，我们提出用具有氧化还原活性的硅酸盐取代惰性磷酸盐，以提高聚阴离子型磷酸盐材料的能量密度和本征电导率，从而推动钠离子电池正极的发展。作为概念验证，我们用一些 NaV(PO)磷酸盐来制备 NaV(PO)(SiO)，这使得正极材料的平均放电电压提高到 3.36V，容量提高到 115.8mA h g-1，高于未掺杂的 NaV(PO)（3.31V，109.6mA h g-1）在 0.5C 下的容量，从而提高了能量密度。此外，引入的硅酸盐增强了 NaV(PO)材料的本征电导率，这一点通过理论模拟和电化学测量得到了证实。将优化后的 NaV(PO)(SiO)正极与商业硬碳负极配对后，在 5C 下循环 300 次后，容量保持率为 90.1%，平均库仑效率高达 99.88%，实现了稳定的循环全电池。
