Jiang Heng, Hong Jessica J, Wu Xianyong, Surta T Wesley, Qi Yitong, Dong Shengyang, Li Zhifei, Leonard Daniel P, Holoubek John J, Wong Jane C, Razink Joshua James, Zhang Xiaogang, Ji Xiulei
Department of Chemistry , Oregon State University , Corvallis , Oregon 97331-4003 , United States.
Jiangsu Key Laboratory of Materials and Technology for Energy Conversion, College of Material Science and Engineering , Nanjing University of Aeronautics and Astronautics , Nanjing 210016 , People's Republic of China.
J Am Chem Soc. 2018 Sep 19;140(37):11556-11559. doi: 10.1021/jacs.8b03959. Epub 2018 Sep 10.
This study reveals the transport behavior of lattice water during proton (de)insertion in the structure of the hexagonal WO·0.6HO electrode. By monitoring the mass evolution of this electrode material via electrochemical quartz crystal microbalance, we discovered (1) WO·0.6HO incorporates additional lattice water when immersing in the electrolyte at open circuit voltage and during initial cycling; (2) The reductive proton insertion in the WO hydrate is a three-tier process, where in the first stage 0.25 H is inserted per formula unit of WO while simultaneously 0.25 lattice water is expelled; then in the second stage 0.30 naked H is inserted, followed by the third stage with 0.17 HO inserted per formula unit. Ex situ XRD reveals that protonation of the WO hydrate causes consecutive anisotropic structural changes: it first contracts along the c-axis but later expands along the ab planes. Furthermore, WO·0.6HO exhibits impressive cycle life over 20 000 cycles, together with appreciable capacity and promising rate performance.
本研究揭示了在六方WO·0.6HO电极结构中质子（脱）嵌入过程中晶格水的传输行为。通过电化学石英晶体微天平监测该电极材料的质量变化，我们发现：（1）WO·0.6HO在开路电压下浸入电解液时以及初始循环过程中会吸收额外的晶格水；（2）WO水合物中的还原性质子嵌入是一个三层过程，在第一阶段，每分子式单元的WO插入0.25个H，同时排出0.25个晶格水；然后在第二阶段插入0.30个裸H，接着在第三阶段每分子式单元插入0.17个HO。非原位XRD表明，WO水合物的质子化会导致连续的各向异性结构变化：它首先沿c轴收缩，但随后沿ab平面膨胀。此外，WO·0.6HO在超过20000次循环中表现出令人印象深刻的循环寿命，同时具有可观的容量和良好的倍率性能。
