Identification of Solid-Electrolyte Interphase Species by Joint Characterization of Li-Ion Battery Chemistry by Mass Spectrometry and Electrochemical Reaction Networks

The formation and stability of the solid-electrolyte
interphase
(SEI) play central roles in determining the long-term performance
and safety of modern electrochemical energy storage systems. Despite
decades of research, the SEI’s heterogeneous, dynamic, and
multiphase nature has defied comprehensive molecular-level characterization,
creating a critical knowledge gap that limits rational battery design.
In this work, we introduce a computational–experimental framework
that integrates high-throughput quantum chemistry calculations, data-driven
electrochemical reaction networks (eCRNs), stochastic algorithms,
and laser desorption/ionization Fourier transform ion cyclotron resonance
mass spectrometry (LDI-FTICR-MS) to unravel SEI formation in carbonate-based
electrolytes without imposing predefined mechanisms. We constructed
the most comprehensive eCRN to date, spanning over 10,000 species
and 209 million reactions. Through stochastic network analysis, we
successfully recovered 27 species that were previously reported in
the literature and predicted 28 novel SEI speciesnearly doubling
our scientific knowledge in this area. Each new species was rigorously
confirmed through advanced mass spectral analysis of its distinct
molecular and isotopic signatures. We kinetically refined the formation
pathways for a select set of both previously reported and novel SEI
products, revealing kinetically feasible elementary reaction mechanisms
with activation barriers below 1 eV. This computational–experimental
approach deepens our molecular-level understanding of SEI chemistry
by resolving which species form and through which decomposition mechanisms
they emerge. Such knowledge provides the foundation necessary to connect
electrolyte composition to the resulting SEI components, a critical
step toward a more informed electrolyte development in next-generation
lithium-based batteries.