Electrolyte chemistry of adaptive hydrogen bonded domains for high voltage lithium metal batteries

The practical implementation of lithium metal batteries is hindered by unstable electrode-electrolyte interfaces and sluggish ion transport kinetics. Here, we report a molecular design strategy that remodels electrolyte solvation structures via the formation of hydrogen-bonded domains, thereby enhancing both the thermodynamics and interfacial dynamics of Li+ transport. Specifically, we introduce 2-cyano-N-methylacetamide, an electrochemically stable hydrogen bond donor, as a cosolvent to construct stable nanoscale hydrogen-bonded domains ( < 3.5 Å). 2-Cyano-N-methylacetamide generates both classical (H-bond, Hδ⁺–Oδ⁻) and nonclassical (Z-bond, Nδ⁻–Hδ⁺) hydrogen bonding, which disrupts loosely bound solvated clusters and induces tightly coordinated Li+ solvation structures. The hydrogen-bonded domains facilitate the formation of oriented fast Li+ transport channels. Accordingly, in Li | |LiNi0.8Co0.1Mn0.1O2 cells cycled under demanding conditions of 4.7 V with a high areal capacity of ~3.0 mAh cm−2, the electrolyte enables a capacity retention of 78.8% after 400 cycles. In addition, a stable 4.7 V lithium metal pouch cell is demonstrated with a specific energy (based on the mass of all components) of 418.2 Wh kg−1. This work offers a useful electrolyte design principle on solvation chemistry and interfacial engineering for high-voltage lithium metal batteries. Lithium metal batteries face challenges of unstable interfaces and slow ion transport. Here, authors report a hydrogen-bonded domain electrolyte based on addition of 2-cyano-N-methylacetamidethat as cosolvent which enhances ion transport and interface stability, enabling long cycling high voltage (up to 4.7 V) Li | |LiNi0.8Co0.1Mn0.1O2 batteries with high specific energy of 418.2 Wh kg−1.