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

Abstract

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, H^δ⁺-O^δ⁻) and nonclassical (Z-bond, N^δ⁻-H^δ⁺) 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 | |LiNi_0.8Co_0.1Mn_0.1O₂ 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.