Dong Wujie, Lin Tianquan, Huang Jian, Wang Yuan, Zhang Zhichao, Wang Xin, Yuan Xiaotao, Lin Jie, Chen I-Wei, Huang Fuqiang
State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China.
State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
Research (Wash D C). 2020 Oct 9;2020:4178179. doi: 10.34133/2020/4178179. eCollection 2020.
Aqueous supercapacitors are powerful energy sources, but they are limited by energy density that is much lower than lithium-ion batteries. Since raising the voltage beyond the thermodynamic potential for water splitting (1.23 V) can boost the energy density, there has been much effort on water-stabilizing salvation additives such as LiSO that can provide an aqueous electrolyte capable of withstanding ~1.8 V. Guided by the first-principles calculations that reveal water can promote hydrogen and oxygen evolution reactions, here, we pursue a new strategy of covering the electrode with a dense electroplated polymerized polyacrylic acid, which is an electron insulator but a proton conductor and proton reservoir. The combined effect of salvation and coating expands the electrochemical window throughout pH 3 to pH 10 to 2.4 V for both fast and slow proton-mediated redox reactions. This allows activated carbon to quadruple the energy density, a kilogram of nitrogen-doped graphene to provide 127 Watt-hour, and both to have improved endurance because of suppression of water-mediated corrosion. Therefore, aqueous supercapacitors can now achieve energy densities quite comparable to that of a lithium-ion battery, but at 100 times the charging/discharging speed and cycle durability.
水系超级电容器是强大的能源，但它们受到能量密度的限制，其能量密度远低于锂离子电池。由于将电压提高到超过水分解的热力学电位（1.23 V）可以提高能量密度，因此人们对水稳定溶剂添加剂（如LiSO）进行了大量研究，这种添加剂可以提供能够承受约1.8 V电压的水系电解质。基于第一性原理计算揭示水可促进氢和氧析出反应，在此，我们采用一种新策略，即用致密的电镀聚合聚丙烯酸覆盖电极，聚丙烯酸是一种电子绝缘体，但却是质子导体和质子储存库。溶剂化和涂层的综合作用将整个pH 3至pH 10范围内的电化学窗口扩大到2.4 V，适用于快速和慢速质子介导的氧化还原反应。这使得活性炭的能量密度提高四倍，一千克氮掺杂石墨烯可提供127瓦时的能量，并且由于抑制了水介导的腐蚀，二者的耐久性均得到改善。因此，水系超级电容器现在可以实现与锂离子电池相当的能量密度，但充电/放电速度和循环耐久性却是锂离子电池的100倍。
