{ "node": { "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" ] } }, "edges": [ { "id": "edge:292", "source": "term:impedance", "target": "topic:topic-units", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:293", "source": "term:impedance", "target": "term:internal-resistance", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:294", "source": "term:impedance", "target": "term:electrochemical-impedance-spectroscopy", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:295", "source": "term:impedance", "target": "term:nyquist-plot", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/impedance/diffusion", "source": "term:impedance", "target": "term:diffusion", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:297", "source": "term:impedance", "target": "visual:impedance", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } } ], "neighbors": [ { "id": "topic:topic-units", "type": "Topic", "label": "Units and electrical basics", "properties": { "id": "topic-units", "name": "Units and electrical basics", "lede": "The quantities every datasheet is written in, and how they relate.", "context": "Use consistent units and cell/pack basis.", "example": "10 A for 30 min transfers 5 Ah. At constant 3.6 V this is 18 Wh; varying voltage requires integration.", "lesson_url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/", "lesson_label": "Open capacity and C-rate" } }, { "id": "term:internal-resistance", "type": "Term", "label": "Internal resistance", "properties": { "id": "internal-resistance", "name": "Internal resistance", "abbr": "IR", "aka": [ "DC resistance", "DCIR" ], "section": "topic-units", "definition": "The resistance a cell presents to current, from its foils, electrolyte, interfaces and the reactions themselves. It converts part of the delivered energy into heat, sets the voltage drop under load, and rises as the cell ages; a large automotive cell has about a milliohm, a small cylindrical cell tens.", "unit": "mΩ", "related": [ "ohms-law", "ir-drop", "impedance-rise", "dcir", "area-specific-resistance", "resistance-capacity-product" ], "lesson": "fundamentals/battery-basics/#datasheet", "url": "https://lemonergy.com/learn/glossary/internal-resistance/", "mentions": [ "electrolyte", "cylindrical-cell" ] } }, { "id": "term:electrochemical-impedance-spectroscopy", "type": "Term", "label": "Electrochemical impedance spectroscopy", "properties": { "id": "electrochemical-impedance-spectroscopy", "name": "Electrochemical impedance spectroscopy", "abbr": "EIS", "section": "topic-testing", "definition": "Measuring a cell’s impedance across a range of frequencies, from kilohertz to millihertz, with a small alternating signal. The spectrum separates ohmic, interface and diffusion processes by their time scale and is read on a Nyquist plot.", "related": [ "nyquist-plot", "impedance", "randles-circuit", "charge-transfer", "warburg-impedance" ], "url": "https://lemonergy.com/learn/glossary/electrochemical-impedance-spectroscopy/", "mentions": [ "diffusion" ] } }, { "id": "term:nyquist-plot", "type": "Term", "label": "Nyquist plot", "properties": { "id": "nyquist-plot", "name": "Nyquist plot", "section": "topic-transport", "definition": "The usual display of an impedance spectrum: negative imaginary part against real part, one point per frequency. Reading left to right, the ohmic intercept, one or two semicircles for interfaces and a diffusion tail each tell a different story about the cell.", "related": [ "electrochemical-impedance-spectroscopy", "impedance", "warburg-impedance", "randles-circuit" ], "url": "https://lemonergy.com/learn/glossary/nyquist-plot/", "mentions": [ "diffusion" ] } }, { "id": "term:diffusion", "type": "Term", "label": "Diffusion", "properties": { "id": "diffusion", "name": "Diffusion", "section": "topic-transport", "definition": "The net movement of a species from where it is concentrated to where it is scarce, driven by random thermal motion. In a cell lithium diffuses through the electrolyte in the pores and, far more slowly, through the solid particles themselves.", "related": [ "ficks-first-law", "diffusion-coefficient", "solid-state-diffusion", "concentration-gradient", "migration" ], "lesson": "transport/ficks-first-law/#in-a-cell", "url": "https://lemonergy.com/learn/glossary/diffusion/", "mentions": [ "electrolyte" ] } }, { "id": "visual:impedance", "type": "Visual", "label": "Read an impedance semicircle", "properties": { "title": "Read an impedance semicircle", "summary": "A series resistance plus one parallel RC branch gives a single semicircle.", "readout": "High-frequency intercept: 10 mΩ. Arc width: 30 mΩ. Low-frequency intercept: 40 mΩ.", "formula": "Z = R₀ + R₁ / (1 + jωR₁C)", "note": "No diffusion tail or inductive loop. The plotted aspect ratio may distort the semicircle.", "software": { "status": "reference", "label": "Reference concept", "body": "An analytical R₀ + (R₁ ∥ C) example. Diffusion and inductance are omitted; this is neither a measured spectrum nor an identified cell model.", "href": "../chapter-1/" }, "html": "
R₀ + parallel RC impedance
R₀ + parallel RC impedanceReal impedance Z′ (mΩ) versus −Imaginary impedance −Z″ (mΩ). High frequency → low frequency. Interpretation follows the graphs.005.6311.311.322.516.933.822.545Real impedance Z′ (mΩ)−Imaginary impedance −Z″(mΩ)
High frequency → low frequency
" } } ] }