Suppressing Hydrogen Evolution in Aqueous Lithium-Ion Batteries with Double-Site Hydrogen Bonding
Lixue Zhou, Songwei Tian, Xiaofan Du, Tingting Liu, Hao Zhang, Jinning Zhang, Jinning Zhang, Sijia Hu, Zheng Chen, Jianjun Zhang, Jianjun Zhang, Guanglei Cui
Abstract
The recent concept of “molecular crowding agents” offering hydrogen bond (H-bond) accepting sites for free water molecules has alleviated parasitic hydrogen evolution in aqueous electrolytes. However, their cathodic limits are still not low enough to be compatible with the energy-dense Li4Ti5O12 anode (1.55 V vs Li+/Li). Inspired by nature’s choice of a peptide unit featuring an amide group in forming extensive H-bond networks with water, herein, we select caprolactam, an imide analogous to the amide group in a peptide, to reduce water activity via regulating the H-bond. The introduced caprolactam containing both an H-bond acceptor and donor effectively confines water molecules in a double-site anchoring configuration with strengthened H-bonding interactions and interrupts the original H-bonding among water molecules. This unique solution structure delays the onset potential of hydrogen evolution to 1.3 V vs Li+/Li, which enables the cycling of a Li4Ti5O12/LiMn2O4 full cell with an average Coulombic efficiency of 99.7% and 78% capacity retention after 350 cycles.