Institute for Inorganic Chemistry, Christan-Albrechts-Universität zu Kiel , Max-Eyth-Str.2, 24118 Kiel, Germany.
Institute for Applied Materials - Energy Storage Systems (IAM-ESS), Karlsruhe Institute of Technology (KIT) , Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
ACS Appl Mater Interfaces. 2017 Jun 28;9(25):21283-21291. doi: 10.1021/acsami.7b04739. Epub 2017 Jun 16.
The ternary compound CuVS exhibits an excellent performance as anode material for sodium ion batteries with a high reversible capacity of 580 mAh g at 0.7 A g after 300 cycles. A Coulombic efficiency of ≈99% is achieved after the third cycle. Increase of the C-rate leads to a drop of the capacity, but a full recovery is observed after switching back to the initial C-rate. In the early stages of Na uptake first Cu is reduced and expelled from the electrode as nanocrystalline metallic Cu. An increase of the Na content leads to a full conversion of the material with nanocrystalline Cu particles and elemental V embedded in a NaS matrix. The formation of NaS is evidenced by Na MAS NMR spectra and X-ray powder diffraction. During the charge process the nanocrystalline Cu particles are retained, but no crystalline materials are formed. At later stages of cycling the reaction mechanism changes which is accompanied by the formation of copper(I) sulfide. The presence of nanocrystalline metallic Cu and/or CuS improves the electrical conductivity, leading to superior cycling and rate capability.
三元化合物 CuVS 作为钠离子电池的阳极材料具有优异的性能，在 0.7 A g 的电流密度下经过 300 次循环后可逆容量高达 580 mAh g。第三个循环后实现了 ≈99%的库仑效率。倍率的增加导致容量下降，但在切换回初始倍率后可以完全恢复。在钠吸收的早期阶段，首先 Cu 被还原并以纳米晶态金属 Cu 的形式从电极中排出。Na 含量的增加导致材料完全转化为纳米晶 Cu 颗粒和嵌入 NaS 基体中的元素 V。Na MAS NMR 光谱和 X 射线粉末衍射证明了 NaS 的形成。在充电过程中保留了纳米晶 Cu 颗粒，但没有形成结晶材料。在循环的后期阶段，反应机制发生变化，伴随着铜(I)硫化物的形成。纳米晶态金属 Cu 和/或 CuS 的存在提高了电导率，从而提高了循环性能和倍率性能。
