{ "node": { "id": "term:cei", "type": "Term", "label": "Cathode–electrolyte interphase", "properties": { "id": "cei", "name": "Cathode–electrolyte interphase", "abbr": "CEI", "section": "topic-aging", "definition": "The counterpart of the SEI on the positive electrode: a thin layer of electrolyte oxidation products on the oxide surface. It is thinner and less stable than the SEI, and its growth contributes to impedance rise, especially at high voltage.", "related": [ "sei", "electrolyte-decomposition", "impedance-rise", "high-nickel" ], "url": "https://lemonergy.com/learn/glossary/cei/", "mentions": [ "impedance", "electrode", "positive-electrode", "electrolyte", "oxidation" ] } }, "edges": [ { "id": "edge:547", "source": "term:cei", "target": "topic:topic-aging", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:548", "source": "term:cei", "target": "term:sei", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:549", "source": "term:cei", "target": "term:electrolyte-decomposition", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:550", "source": "term:cei", "target": "term:impedance-rise", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:551", "source": "term:cei", "target": "term:high-nickel", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/cei/impedance", "source": "term:cei", "target": "term:impedance", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:mentions/cei/electrode", "source": "term:cei", "target": "term:electrode", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:mentions/cei/positive-electrode", "source": "term:cei", "target": "term:positive-electrode", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:mentions/cei/electrolyte", "source": "term:cei", "target": "term:electrolyte", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:mentions/cei/oxidation", "source": "term:cei", "target": "term:oxidation", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:557", "source": "term:cei", "target": "visual:film", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } }, { "id": "edge:558", "source": "term:cei", "target": "reference:edge-degradation", "type": "cites", "properties": { "sourceFile": "wiki-references.json", "scope": "direct technical reference" } } ], "neighbors": [ { "id": "topic:topic-aging", "type": "Topic", "label": "Aging and degradation", "properties": { "id": "topic-aging", "name": "Aging and degradation", "lede": "Why a cell loses capacity and gains resistance, and the mechanisms behind it.", "context": "Separate mechanisms, observations and fitted models.", "example": "Capacity loss and resistance rise can have different causes; a film-growth curve cannot identify both.", "lesson_url": "https://lemonergy.com/learn/fundamentals/battery-aging/", "lesson_label": "Open aging" } }, { "id": "term:sei", "type": "Term", "label": "Solid–electrolyte interphase", "properties": { "id": "sei", "name": "Solid–electrolyte interphase", "abbr": "SEI", "section": "topic-aging", "definition": "A film of electrolyte reaction products on the negative-electrode particles — graphite, and also silicon or lithium metal. It protects the electrode from further reaction but grows slowly for the whole life of the cell, consuming cyclable lithium.", "related": [ "passivation", "formation", "calendar-aging", "loss-of-lithium-inventory", "cei" ], "lesson": "fundamentals/battery-aging/#sei", "url": "https://lemonergy.com/learn/glossary/sei/", "mentions": [ "electrode", "graphite", "electrolyte" ] } }, { "id": "term:electrolyte-decomposition", "type": "Term", "label": "Electrolyte decomposition", "properties": { "id": "electrolyte-decomposition", "name": "Electrolyte decomposition", "section": "topic-aging", "definition": "Reduction of the electrolyte at the negative electrode and oxidation at the positive, outside its stability window. A little is useful — it builds the SEI — but continued decomposition consumes lithium, dries the cell and makes gas.", "related": [ "sei", "cei", "electrochemical-stability-window", "gas-generation", "electrolyte-dry-out" ], "url": "https://lemonergy.com/learn/glossary/electrolyte-decomposition/", "mentions": [ "electrode", "negative-electrode", "electrolyte", "oxidation", "reduction" ] } }, { "id": "term:impedance-rise", "type": "Term", "label": "Impedance rise", "properties": { "id": "impedance-rise", "name": "Impedance rise", "aka": [ "resistance growth", "power fade" ], "section": "topic-aging", "definition": "An increase in a cell’s internal resistance as it ages. It costs voltage under load and therefore power, even while the stored charge is still there.", "related": [ "internal-resistance", "sei", "cei", "state-of-power", "state-of-health" ], "lesson": "fundamentals/battery-aging/#crystals", "url": "https://lemonergy.com/learn/glossary/impedance-rise/", "mentions": [ "closed-circuit-voltage" ] } }, { "id": "term:high-nickel", "type": "Term", "label": "High-nickel cathode", "properties": { "id": "high-nickel", "name": "High-nickel cathode", "aka": [ "Ni-rich" ], "section": "topic-chemistries", "definition": "A layered oxide with 80 % or more nickel, such as NMC811 or NCA. Nickel raises capacity and lowers cobalt content, but the material is less thermally stable, more sensitive to moisture and ages faster at high voltage.", "related": [ "nmc", "nca", "cathode-active-material", "thermal-runaway", "cei", "mid-nickel" ], "url": "https://lemonergy.com/learn/glossary/high-nickel/", "mentions": [ "cobalt", "layered-oxide" ] } }, { "id": "term:impedance", "type": "Term", "label": "Impedance", "properties": { "id": "impedance", "name": "Impedance", "abbr": "Z", "section": "topic-units", "definition": "The frequency-dependent generalisation of resistance, with a magnitude and a phase. A cell’s impedance separates ohmic, charge-transfer and diffusion contributions that a single DC resistance lumps together.", "unit": "Ω", "related": [ "internal-resistance", "electrochemical-impedance-spectroscopy", "nyquist-plot" ], "url": "https://lemonergy.com/learn/glossary/impedance/", "mentions": [ "diffusion" ] } }, { "id": "term:electrode", "type": "Term", "label": "Electrode", "properties": { "id": "electrode", "name": "Electrode", "section": "topic-components", "definition": "A solid conductor where the cell’s reaction happens, in contact with the electrolyte. A lithium-ion cell has a negative electrode and a positive electrode, each a porous coating on a metal foil.", "related": [ "negative-electrode", "positive-electrode", "porous-electrode", "current-collector" ], "lesson": "fundamentals/cell-anatomy/#components", "example": { "title": "Two transport paths", "text": "Electrons need connected solid paths to the collector; ions need electrolyte paths to reaction sites. More of one constituent displaces others at fixed volume." }, "url": "https://lemonergy.com/learn/glossary/electrode/", "mentions": [ "electrolyte", "coating" ] } }, { "id": "term:positive-electrode", "type": "Term", "label": "Positive electrode", "properties": { "id": "positive-electrode", "name": "Positive electrode", "section": "topic-components", "definition": "The electrode at the higher potential: a lithium metal oxide or phosphate coated on aluminium foil. It is the lithium source when a cell is built, and industry calls it the cathode.", "related": [ "cathode", "cathode-active-material", "negative-electrode", "aluminium-foil" ], "lesson": "fundamentals/cell-anatomy/#anode-cathode", "example": { "title": "Polarity and reaction", "text": "The positive electrode retains its polarity label while its electrochemical reaction reverses between charge and discharge." }, "url": "https://lemonergy.com/learn/glossary/positive-electrode/", "mentions": [ "electrode" ] } }, { "id": "term:electrolyte", "type": "Term", "label": "Electrolyte", "properties": { "id": "electrolyte", "name": "Electrolyte", "section": "topic-electrolytes", "definition": "The ion-conducting medium between the electrodes. In a liquid-electrolyte cell it fills the pores of both electrodes and the separator, so it is not a separate structural layer.", "related": [ "lithium-salt", "carbonate-solvent", "electrolyte-additive", "ionic-conductivity", "solid-electrolyte", "ionic-liquid-electrolyte" ], "lesson": "fundamentals/cell-architecture/#electrolyte", "example": { "title": "Ions and electrons", "text": "Electrolyte carries ions between electrodes; the external circuit carries electrons. The two paths serve different roles." }, "url": "https://lemonergy.com/learn/glossary/electrolyte/", "mentions": [ "separator" ] } }, { "id": "term:oxidation", "type": "Term", "label": "Oxidation", "properties": { "id": "oxidation", "name": "Oxidation", "section": "topic-electrochemistry", "definition": "Loss of electrons by a species. On discharge the negative electrode is oxidised as lithium leaves it as Li⁺, which is why that electrode is called the anode.", "related": [ "reduction", "anode", "redox-reaction" ], "url": "https://lemonergy.com/learn/glossary/oxidation/", "mentions": [ "electrode", "negative-electrode" ] } }, { "id": "visual:film", "type": "Visual", "label": "Diffusion-limited film growth", "properties": { "title": "Diffusion-limited film growth", "summary": "Four times the elapsed time gives twice the film thickness in this model.", "readout": "At four reference time units, thickness is 2× the reference thickness.", "formula": "δ / δ_ref = √[(t / t_ref) A]", "note": "Normalized analytical relation, not a capacity-loss or SOH prediction.", "software": { "status": "implemented", "label": "Implemented in battery-core", "body": "parabolic_film_thickness uses reference thickness × √(relative time × acceleration). Converting film thickness to capacity loss requires a calibrated relationship.", "href": "../fundamentals/battery-aging/" }, "html": "
Relative film growth
Relative film growthTime / reference time versus Thickness / reference thickness. Selected acceleration; Reference conditions. Interpretation follows the graphs.002448612816Time / reference timeThickness / referencethickness
Selected accelerationReference conditions (dashed)
" } }, { "id": "reference:edge-degradation", "type": "Reference", "label": "Lithium ion battery degradation: what you need to know", "properties": { "title": "Lithium ion battery degradation: what you need to know", "publisher": "Physical Chemistry Chemical Physics", "url": "https://doi.org/10.1039/D1CP00359C", "type": "Review article", "scope": "Degradation mechanisms, modes, operational effects and their interactions.", "year": 2021, "accessed": "2026-10-27" } } ] }