{ "node": { "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" ] } }, "edges": [ { "id": "edge:21", "source": "term:sei", "target": "workflow:film-growth", "type": "usedIn", "properties": { "sourceFile": "wiki-blocks.json" } }, { "id": "edge:534", "source": "term:sei", "target": "topic:topic-aging", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:535", "source": "term:sei", "target": "term:passivation", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:536", "source": "term:sei", "target": "term:formation", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:537", "source": "term:sei", "target": "term:calendar-aging", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:538", "source": "term:sei", "target": "term:loss-of-lithium-inventory", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:539", "source": "term:sei", "target": "term:cei", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/sei/electrode", "source": "term:sei", "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/sei/graphite", "source": "term:sei", "target": "term:graphite", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:mentions/sei/electrolyte", "source": "term:sei", "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:543", "source": "term:sei", "target": "lesson:fundamentals/battery-aging/", "type": "explainedIn", "properties": { "sourceFile": "terms.json", "url": "https://lemonergy.com/learn/fundamentals/battery-aging/#sei" } }, { "id": "edge:544", "source": "term:sei", "target": "visual:film", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } }, { "id": "edge:545", "source": "term:sei", "target": "reference:edge-degradation", "type": "cites", "properties": { "sourceFile": "wiki-references.json", "scope": "direct technical reference" } }, { "id": "edge:546", "source": "term:sei", "target": "reference:wang-sei", "type": "cites", "properties": { "sourceFile": "wiki-references.json", "scope": "direct technical reference" } } ], "neighbors": [ { "id": "workflow:film-growth", "type": "Workflow", "label": "Explore film growth", "properties": { "id": "film-growth", "title": "Explore film growth", "kind": "core", "summary": "Lemonergy Core evaluates this relation.", "steps": [ "Open the lesson and inspect the equation.", "Change one input while holding the others fixed." ], "example": "At a factor of one, 10 nm at 1 h becomes 20 nm at 4 h and 30 nm at 9 h.", "observe": "Compare the result with the equation and units.", "limits": "This does not identify SEI chemistry or fit state of health.", "url": "https://lemonergy.com/learn/fundamentals/battery-aging/#sei", "label": "Open the worked lesson", "evidence": [ "src/battery_core/aging.py" ] } }, { "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:passivation", "type": "Term", "label": "Passivation", "properties": { "id": "passivation", "name": "Passivation", "section": "topic-aging", "definition": "The formation of a surface film that slows further reaction. In lithium-ion cells, the SEI passivates the graphite negative electrode.", "related": [ "sei", "aluminium-foil", "formation" ], "lesson": "fundamentals/battery-aging/#sei", "url": "https://lemonergy.com/learn/glossary/passivation/", "mentions": [ "electrode", "negative-electrode", "graphite" ] } }, { "id": "term:formation", "type": "Term", "label": "Formation", "properties": { "id": "formation", "name": "Formation", "section": "topic-manufacturing", "definition": "The first controlled charge and discharge cycles of a newly assembled cell, during which the SEI forms. It is part of cell production, before aging and grading.", "related": [ "sei", "degassing", "aging-step", "first-cycle-loss", "cell-finishing" ], "lesson": "fundamentals/cell-production/#finishing", "example": { "title": "Distinguish first finishing cycles", "text": "Initial controlled cycles are a cell-finishing operation; their purpose and observations differ from later customer charging." }, "url": "https://lemonergy.com/learn/glossary/formation/", "mentions": [ "cell-production" ] } }, { "id": "term:calendar-aging", "type": "Term", "label": "Calendar aging", "properties": { "id": "calendar-aging", "name": "Calendar aging", "section": "topic-aging", "definition": "Degradation that happens with time even when a cell is not cycled — in storage, for example. It is driven mainly by side reactions such as SEI growth and accelerates with temperature.", "related": [ "cycle-aging", "sei", "arrhenius", "square-root-of-time", "calendar-life" ], "lesson": "fundamentals/battery-aging/#whole-cell", "url": "https://lemonergy.com/learn/glossary/calendar-aging/", "mentions": [] } }, { "id": "term:loss-of-lithium-inventory", "type": "Term", "label": "Loss of lithium inventory", "properties": { "id": "loss-of-lithium-inventory", "name": "Loss of lithium inventory", "abbr": "LLI", "section": "topic-aging", "definition": "The degradation mode in which cyclable lithium is consumed by side reactions — SEI growth, plating, electrolyte decomposition — and can no longer shuttle between the electrodes. It is the dominant cause of capacity fade in most lithium-ion cells.", "related": [ "sei", "lithium-plating", "capacity-fade", "loss-of-active-material", "coulombic-efficiency" ], "url": "https://lemonergy.com/learn/glossary/loss-of-lithium-inventory/", "mentions": [ "electrolyte", "aging-mechanism", "electrolyte-decomposition" ] } }, { "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" ] } }, { "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:graphite", "type": "Term", "label": "Graphite", "properties": { "id": "graphite", "name": "Graphite", "section": "topic-components", "definition": "Layered carbon, the negative active material of nearly all lithium-ion cells. Lithium intercalates between its layers up to LiC₆, a theoretical 372 mAh/g, at a potential about 0.1 V above lithium metal.", "related": [ "anode-active-material", "intercalation", "natural-graphite", "synthetic-graphite", "lithium-plating" ], "lesson": "fundamentals/cell-anatomy/#components", "example": { "title": "Compare matching mass bases", "text": "A graphite value per gram of active material cannot be directly compared with a value including binder, additive and foil." }, "url": "https://lemonergy.com/learn/glossary/graphite/", "mentions": [ "milliampere-hour", "active-material" ] } }, { "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": "lesson:fundamentals/battery-aging/", "type": "Lesson", "label": "Lesson 4 · Battery aging", "properties": { "url": "https://lemonergy.com/learn/fundamentals/battery-aging/" } }, { "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" } }, { "id": "reference:wang-sei", "type": "Reference", "label": "Identifying the components of the solid–electrolyte interphase in Li-ion batteries", "properties": { "title": "Identifying the components of the solid–electrolyte interphase in Li-ion batteries", "publisher": "Nature Chemistry", "url": "https://doi.org/10.1038/s41557-019-0304-z", "type": "Research article", "scope": "Experimental identification of SEI components in the studied systems.", "year": 2019, "authors": [ "Luning Wang et al." ], "accessed": "2026-10-27" } } ] }