{
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"label": "Electric double layer",
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"id": "double-layer",
"name": "Electric double layer",
"section": "topic-electrochemistry",
"definition": "The thin region at an electrode surface where ions in the electrolyte line up against the charge on the electrode, behaving like a capacitor. It stores a little charge without any reaction and shapes the high-frequency part of an impedance spectrum.",
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"charge-transfer",
"electrochemical-impedance-spectroscopy",
"supercapacitor"
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"id": "edge:1930",
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"id": "edge:mentions/double-layer/impedance",
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"lede": "The reactions and potentials that make a cell a battery.",
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"id": "term:charge-transfer",
"type": "Term",
"label": "Charge transfer",
"properties": {
"id": "charge-transfer",
"name": "Charge transfer",
"section": "topic-electrochemistry",
"definition": "The step in which an electron crosses the interface between electrode and electrolyte as an ion is inserted or removed. Its resistance appears as a semicircle in impedance spectra and grows as films thicken and the cell cools.",
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"id": "term:electrochemical-impedance-spectroscopy",
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"id": "electrochemical-impedance-spectroscopy",
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"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.",
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"nyquist-plot",
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{
"id": "term:supercapacitor",
"type": "Term",
"label": "Supercapacitor",
"properties": {
"id": "supercapacitor",
"name": "Supercapacitor",
"aka": [
"ultracapacitor",
"EDLC"
],
"section": "topic-electrochemistry",
"definition": "A device that stores charge in the electric double layer on high-surface-area carbon rather than in a reaction. It delivers very high power and lasts a million cycles but stores only a few watt-hours per kilogram.",
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"double-layer",
"specific-power",
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"mentions": []
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{
"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"
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"mentions": [
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{
"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"
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"example": {
"title": "Two transport paths",
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},
"url": "https://lemonergy.com/learn/glossary/electrode/",
"mentions": [
"electrolyte",
"coating"
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{
"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"
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"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:capacitor",
"type": "Term",
"label": "Capacitor",
"properties": {
"id": "capacitor",
"name": "Capacitor",
"section": "topic-units",
"definition": "A component that stores energy as charge on two conducting plates separated by an insulator; its voltage rises in proportion to the charge, unlike a battery’s nearly flat curve. The large DC-link capacitors at an inverter’s input draw a huge inrush current when connected to a pack, which is why a pre-charge circuit fills them first.",
"formula": "Q = C·V; E = ½·C·V²",
"unit": "F (farad)",
"related": [
"pre-charge",
"inverter",
"supercapacitor",
"double-layer",
"contactor"
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"example": {
"title": "Calculate stored charge and energy",
"text": "An ideal 100 F capacitor charged to 2 V stores 200 C and 200 J. Doubling voltage quadruples its stored energy when capacitance remains constant."
},
"url": "https://lemonergy.com/learn/glossary/capacitor/",
"mentions": [
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},
{
"id": "visual:capacitor",
"type": "Visual",
"label": "Capacitor charge and energy",
"properties": {
"title": "Capacitor charge and energy",
"summary": "Charge rises linearly with voltage; energy rises with voltage squared.",
"readout": "At 5 V: 25 C and 62.5 J.",
"formula": "Q = CV; E = ½CV²",
"note": "Ideal constant capacitance; leakage, series resistance and voltage rating excluded.",
"software": {
"status": "reference",
"label": "Reference concept",
"body": "Q = CV and E = ½CV² explain capacitor storage. The battery nominal-energy helper alone does not simulate capacitor precharge.",
"href": "../fundamentals/battery-basics/"
},
"html": "Stored charge