Toward Unified Interphase Engineering: The Solid-Electrolyte Interphase in Batteries and Supercapacitors

TL;DR

This work proposes a unified, cross-platform framework for solid-electrolyte interphases (SEIs) that treats SEI formation as a universal electrochemical process, governed by electron transfer beyond electrolyte stability and modulated by operating conditions rather than chemistry alone. It synthesizes fundamental mechanisms, experimental characterizations, multiscale modeling, and materials engineering to enable predictive interphase design across batteries and supercapacitors. By detailing shared formation pathways, dynamic reconstruction, and the impact of SEI on impedance and capacitance, the paper argues that transferable design rules and AI-enhanced workflows can deliver high energy density, rapid power, and ultralong lifetimes while supporting sustainability. The review then outlines a comprehensive research roadmap, including unified theory, open data, quantum-informed interfacial models, and green electrolytes, to accelerate the development of robust, adaptive SEIs across energy-storage technologies.

Abstract

The development of next-generation electrochemical energy storage requires devices that combine the high energy density of batteries with the power capability and long cycle life of supercapacitors. However, the interfacial phenomena governing performance in these systems remain poorly unified. The solid-electrolyte interphase (SEI), a nanoscale film formed by electrolyte decomposition, is well studied in batteries but its counterpart in supercapacitors has received limited systematic investigation despite growing experimental evidence. This review argues that SEI formation is a universal electrochemical process that occurs whenever electrode potentials drive electron transfer into electrolyte orbitals beyond their stability limits, independent of whether charge storage is Faradaic or non-Faradaic. Differences between battery SEIs and supercapacitor interphases arise mainly from operating conditions, not fundamental chemistry. Engineered interphases created through electrolyte additives, protective coatings, or surface functionalization suppress leakage currents, improve capacitance retention, and enable stable high-voltage operation. By identifying shared mechanisms and establishing transferable design rules, this unified framework provides a foundation for predictive interphase engineering that supports long-lived, high-performance energy-storage technologies.

Figures (9)

• Figure 1: The Electrochemical Energy–Power Landscape.
• Figure 2: The historical of solid electrolyte interphase.
• Figure 3: Schematic overview of SEI formation across energy-storage systems, showing five common stages: (1) electron injection and inorganic nucleationnojabaee2021understanding, (2) solvent/anion decompositionsaqib2018decomposition, and (3) mechanical relaxationli2025understanding.
• Figure 4: Schematic overview of SEI formation across energy-storage systems via Polymer condensationgao2019polymer.
• Figure 5: Recent advances in mechanistic understandings of Li deposition and SEI using advanced analytical techniques and theoretical modelling methods. a) Advanced characterization techniques for analyzing Li plating and stripping behaviors include Magnetic resonance imaging (MRI), SXCT), Cryo-TEM, SEM, AFM-ETEM, OM, liquid-cell TEM, Cryo-FIB, TGC, and Cryo-TEM. b) Analysis of SEI involves cryo-TEM, AFM, SIMS, NMR, and cryo-STEM tomography. c) Theoretical modelling methods include MC/MD, finite element method (FEM), DFT(B), SPH, and MC for calculation of the diffusion energy barriers and simulation of the Li deposition behavior and SEI structurexu2022promoting.