Jiang Ping, Lei Zhenyu, Chen Liang, Shao Xuecheng, Liang Xinmiao, Zhang Jun, Wang Yanchao, Zhang Jiujun, Liu Zhaoping, Feng Jiwen
Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences , Wuhan 430071 , P.R. China.
Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences , Ningbo 315201 , P.R. China.
ACS Appl Mater Interfaces. 2019 Aug 14;11(32):28762-28768. doi: 10.1021/acsami.9b04849. Epub 2019 Jul 31.
Vanadium hexacyanoferrate (VHCF) with an open-framework crystal structure is a promising cathode material for rechargeable aqueous metal-ion batteries owing to its high electrochemical performance and easy synthesis. In this paper, vanadium hexacyanoferrate cathodes were first used for constructing rechargeable aqueous sodium-ion batteries (VHCF/WO) and tested in the new-type electrolyte (NaP-4.6) consisting of a polyethylene glycol (PEG)/HO/NaClO electrolyte with a low H concentration (molar ratio of [HO]/[Na] is 4.6), which has high stability at a high current density as high as 1000 mA g with a capacity retention of 90.3% after 2000 cycles at high coulombic efficiency (above 97.8%). To understand their outstanding performance, the proton-assisted sodium-ion storage mechanism and interphase chemistry of VHCF are investigated by solid-state NMR (ssNMR) technology. It is suggested that the H storage reaction is accompanied by the redox of vanadium atoms and Na intercalation is accompanied by the redox of iron atoms. It is also observed that the complex of polyethylene glycol (PEG) with Na (PEG-Na) exists on the VHCF surface, which facilitates the stability of VHCF and promotes the alkali-ion transfer at a high current density. The results of the ssNMR study offer new insights into the intercalation chemistry of Prussian blue analogues with open-framework-structured compounds, which can greatly broaden our horizons for battery research.
具有开放框架晶体结构的六氰合铁酸钒（VHCF）因其高电化学性能和易于合成，是一种很有前景的可充电水系金属离子电池阴极材料。本文首次将六氰合铁酸钒阴极用于构建可充电水系钠离子电池（VHCF/WO），并在由低H浓度（[HO]/[Na]摩尔比为4.6）的聚乙二醇（PEG）/HO/NaClO电解质组成的新型电解质（NaP - 4.6）中进行测试，该电解质在高达1000 mA g的高电流密度下具有高稳定性，在高库仑效率（高于97.8%）下经过2000次循环后容量保持率为90.3%。为了解其优异性能，通过固态核磁共振（ssNMR）技术研究了VHCF的质子辅助钠离子存储机制和界面化学。结果表明，H存储反应伴随着钒原子的氧化还原，而Na嵌入伴随着铁原子的氧化还原。还观察到聚乙二醇（PEG）与Na的络合物（PEG-Na）存在于VHCF表面，这有助于VHCF的稳定性并促进高电流密度下的碱金属离子转移。ssNMR研究结果为具有开放框架结构化合物的普鲁士蓝类似物的嵌入化学提供了新的见解，这可以极大地拓宽我们在电池研究方面的视野。
