Sodium-ion batteries are moving from validation to deployment, and durable full-cell operation is now limited less by bulk-material discovery than by the chemistry, structure, and mechanics of the nanoscale electrode–electrolyte interphases. Our new article in Nanoscale Horizons argues that the solid (SEI) and cathode (CEI) electrolyte interphases in Na-ion cells cannot be read as scaled lithium analogs — they are nanoscale, mosaic, dynamically reorganizing layers set by a Na⁺ solvation sheath and double-layer environment that differ markedly from Li⁺.
The article reframes Na-ion interphase design around three linked ideas:
- Solvation-first: the primary Na⁺ solvation sheath — not the bulk electrolyte-stability window — selects first-layer chemistry at the nanoscale, through adsorption, desolvation, and absorption at the electrode surface.
- Cross-talk: under lean electrolyte and practical negative-to-positive (N/P) ratios, the two interphases co-evolve through cross-talk rather than passivating independently.
- Evidence tiers: credible mechanistic claims require an explicit evidence-tier hierarchy and a minimum reporting set, so that comparisons across laboratories mean something.
The discussion is anchored in deployment-relevant markers — a representative hard-carbon full-cell initial coulombic efficiency near 91.4%, a reported optimal N/P of about 0.9 in a layered-oxide/hard-carbon pairing, and emerging 1.5 and 3.5 Ah cylindrical Na-ion formats — and closes with a co-design logic and benchmarking checklist for Na-ion full-cell interphase studies.
Read the paper
Wisan T., Tangthuam P., Chang S.-H., Chou H.-H., Lin J.-Y., In I., Kheawhom S. Beyond the Lithium Template: A Solvation-First Framework for Nanoscale Sodium-Ion Interphases, Cross-Talk, and Full-Cell Translation. Nanoscale Horizons (2026), Advance Article, published online 25 August 2026. DOI 10.1039/D6NH00245E