Aqueous energy storage systems, e.g. aqueous lithium ion batteries (ARLIBs), are becoming increasingly important for its high theoretical specific power and safety, while the practical performance has been critically constrained by its narrow voltage window due to the electrochemical water splitting side reactions.[1, 2] Although the sluggish oxygen evolution usually requires a large overpotential, the hydrogen evolution reaction (HER) can easily take place when the applied potential increases, and critically constrains the battery voltage window as well as the Coulombic efficiency. The rational design of anode materials, where the hydrogen evolution also takes place, may suggest a new avenue for developing ARLIB with enhanced voltage window and power density.
Inspired by the high efficient hydrogen evolution catalysts,[4, 5] we designed an opposite strategy instead, aiming to create a large HER overpotential for inhibiting water reduction and subsequently boosting both the battery output voltage and Coulombic efficiency in aqueous solutions. Moreover, the electrode surface passivated with hydrogen evolution further enables high current density during battery cycling, leading to both an ultrahigh power density and an excellent energy density. Density functional theory calculations indicate polyimide nanosheets provide limited sites for hydrogen atom binding and large activation barriers for HER, especially for Li+ associated polyimides. After improving their electronic conductivity by carbon nanotube (CNT) networks, the polyimides/CNT aqueous lithium-ion battery anode exhibits hydrogen evolution onset overpotential as large as 820 mV in neutral aqueous electrolytes, an outstanding reversible capacity of 133.0 mA h g-1, and ultrafast charge-discharge capability (13.6 sec per cycle at 128C). Moreover, an aqueous polyimide-CNT//LiMn2O4 battery exhibits top-level performance, including a wide voltage window (> 2 V), exceptional capacity (68.8 mA h g-1), energy density (76.1 W h kg-1) and power density (12,610 W kg-1), and excellent cycling stability over 1000 cycles when fast operated within ~ 5 min.
1. Luo, J.; Cui, W.; He, P.; Xia, Y. Nat. Chem. 2010, 2, 760-765.
2. Kim, H.; Hong, J.; Park, K.; Kim, H.; Kim, S.; Kang, K. Chem. Rev. 2014, 114, 11788-11827.
3. Suo, L.; Borodin, O; Gao, T; Olguin, M; Ho, J; Fan, X; Luo, C; Wang, C; Xu, K. Science 2015, 350, 938-943.
4. Zhang, X.; Meng, F.; Mao, S.; Ding, Q.; Shearer, M. J.; Faber, M. S.; Chen, J.; Hamers, R. J.; Jin, S. Energy Environ. Sci. 2015, 8, 862-868.
5. Wang, D.; Gong, M.; Chou, H.; Pan, C.; Chen, H.; Wu, Y.; Lin, M. C.; Guan, M.; Yang, J.; Chen, C.; Wang, Y.; Hwang, B.; Chen, C.; Dai, H. J. Am. Chem. Soc. 2015, 137, 1587-1592.