Department of Energy Science and Engineering , Daegu Gyeongbuk Institute of Science and Technology , Daegu 42988 , Republic of Korea.
Inorg Chem. 2019 Mar 4;58(5):3065-3072. doi: 10.1021/acs.inorgchem.8b03081. Epub 2019 Feb 15.
Rhombohedral potassium-zinc hexacyanoferrate KZnFe(CN) (KZnHCF) synthesized using a precipitation method is demonstrated as a high-voltage cathode material for potassium-ion batteries (PIBs), exhibiting an initial discharge capacity of 55.6 mAh g with a discharge voltage of 3.9 V versus K/K and a capacity retention of ∼95% after 100 cycles in a nonaqueous electrolyte. All K ions are extracted from the structure upon the initial charge process. However, only 1.61 out of 1.88 K ions per formula unit are inserted back into the structure upon discharge, and it becomes the reversible ion of the second cycle onward. Despite the large ionic size of K, the material exhibits a lattice-volume change (∼3%) during a cycle, which is exceptionally small among the cathode materials for PIBs. The distinct feature of the material seems to come from the unique porous framework structure built by ZnN and FeC polyhedra linked via the C≡N bond and a Zn/Fe atomic ratio of 3/2, resulting in high structural stability and cycle performance.
使用沉淀法合成的菱面体钾锌六氰合铁酸钾 KZnFe(CN) 6 （KZnHCF）被证明是一种用于钾离子电池（PIB）的高压阴极材料，在非水电解质中具有 3.9 V 相对于 K/K 的初始放电容量 55.6 mAh g 和 100 次循环后的约 95%的容量保持率。在初始充电过程中，结构中的所有 K 离子都被提取出来。然而，在放电过程中，只有 1.88 个 K 离子中的 1.61 个被重新插入到结构中，并且从第二周期开始成为可逆离子。尽管 K 的离子尺寸较大，但该材料在循环过程中表现出约 3%的晶格体积变化，这在 PIB 的阴极材料中是非常小的。该材料的独特特征似乎来自于由 ZnN 和 FeC 多面体通过 C≡N 键连接而成的独特多孔骨架结构，以及 Zn/Fe 原子比为 3/2，从而具有高结构稳定性和循环性能。
