Molecular engineering of an ether–nitrile constructs robust dual-interphases for ultra-stable 4.5 V lithium metal batteries

Abstract

High-voltage lithium metal batteries (LMBs) face a critical barrier to practical deployment: conventional electrolytes fail to stabilize both the cathode and anode interfaces, triggering rapid degradation and safety risks. To overcome this limitation, we designed 3-methoxypropanenitrile (MPN), a molecularly tailored ether–nitrile additive, and integrated it into a diluted high-concentration electrolyte (DHCE). Computational studies reveal that the ether–oxygen heteroatom in MPN redistributes electron density and fine-tunes Li⁺ solvation, effectively circumventing the notorious reactivity of nitrile groups with lithium metal. This molecular intervention enables dual-interphase stabilization—on the lithium anode, MPN promotes anion-derived decomposition through weak yet selective Li⁺ coordination, forming an inorganic-rich SEI (LiF/Li₃N) that ensures 99.5% coulombic efficiency and uniform lithium deposition. At the LiMn_xFe_1−xPO₄ cathode operating above 4.5 V, MPN adsorbs preferentially via Mn/Fe coordination, shields the surface from oxidative attack, and participates in hydrogen-transfer reactions with FSI⁻ anions to construct a robust inorganic CEI, substantially suppressing transition metal dissolution. As a result, the MPN-enhanced electrolyte enables Li||LMFP full cells to achieve breakthrough cycling stability, maintaining 86.4% capacity after 1400 cycles at 0.5C while sustaining 300 cycles under lean-lithium conditions (N/P = 2). This work establishes a heteroatom-functionalization strategy that transforms conventionally incompatible nitriles into bifunctional interphase regulators, thereby providing a universal platform for constructing durable high-voltage lithium metal batteries.