{ "node": { "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" ] } }, "edges": [ { "id": "edge:2176", "source": "term:nyquist-plot", "target": "topic:topic-transport", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:2177", "source": "term:nyquist-plot", "target": "term:electrochemical-impedance-spectroscopy", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:2178", "source": "term:nyquist-plot", "target": "term:impedance", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:2179", "source": "term:nyquist-plot", "target": "term:warburg-impedance", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:2180", "source": "term:nyquist-plot", "target": "term:randles-circuit", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/nyquist-plot/diffusion", "source": "term:nyquist-plot", "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:2182", "source": "term:nyquist-plot", "target": "visual:impedance", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } } ], "neighbors": [ { "id": "topic:topic-transport", "type": "Topic", "label": "Transport and modelling", "properties": { "id": "topic-transport", "name": "Transport and modelling", "lede": "How ions move, and the equations and models that describe a cell.", "context": "Specify phase, direction and boundaries.", "example": "The same concentration difference across 10 μm gives ten times the gradient across 100 μm; at equal D, first-law flux magnitude is ten times greater.", "lesson_url": "https://lemonergy.com/learn/transport/ficks-first-law/", "lesson_label": "Open diffusion" } }, { "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. 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Its slope and onset frequency give a route to the diffusion coefficient.", "related": [ "randles-circuit", "nyquist-plot", "diffusion-coefficient", "electrochemical-impedance-spectroscopy" ], "url": "https://lemonergy.com/learn/glossary/warburg-impedance/", "mentions": [ "impedance", "diffusion" ] } }, { "id": "term:randles-circuit", "type": "Term", "label": "Randles circuit", "properties": { "id": "randles-circuit", "name": "Randles circuit", "section": "topic-transport", "definition": "The classic equivalent circuit for one electrode interface: electrolyte resistance in series with a double-layer capacitance that shunts the charge-transfer resistance and a Warburg diffusion element. 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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
" } } ] }