{ "node": { "id": "term:energy-density", "type": "Term", "label": "Energy density", "properties": { "id": "energy-density", "name": "Energy density", "aka": [ "volumetric energy density" ], "section": "topic-ratings", "definition": "Stored energy per unit volume, in watt-hours per litre. It is the figure that matters when space is the constraint, as in a phone or under a car floor; high-energy cylindrical cells pass 700 Wh/L.", "unit": "Wh/L", "related": [ "specific-energy", "nominal-energy", "ragone-plot", "areal-loading" ], "lesson": "fundamentals/capacity-and-c-rate/#energy", "url": "https://lemonergy.com/learn/glossary/energy-density/", "mentions": [] } }, "edges": [ { "id": "edge:933", "source": "term:energy-density", "target": "topic:topic-ratings", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:934", "source": "term:energy-density", "target": "term:specific-energy", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:935", "source": "term:energy-density", "target": "term:nominal-energy", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:936", "source": "term:energy-density", "target": "term:ragone-plot", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:937", "source": "term:energy-density", "target": "term:areal-loading", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:938", "source": "term:energy-density", "target": "lesson:fundamentals/capacity-and-c-rate/", "type": "explainedIn", "properties": { "sourceFile": "terms.json", "url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/#energy" } }, { "id": "edge:939", "source": "term:energy-density", "target": "visual:energy", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } } ], "neighbors": [ { "id": "topic:topic-ratings", "type": "Topic", "label": "Capacity, energy, power and ratings", "properties": { "id": "topic-ratings", "name": "Capacity, energy, power and ratings", "lede": "The numbers that size a cell and let two cells be compared.", "context": "Separate nameplate ratings from test results.", "example": "5 Ah at 3.6 V gives 18 Wh nominally. Integrated measured terminal power may give a different result.", "lesson_url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/", "lesson_label": "Open capacity and C-rate" } }, { "id": "term:specific-energy", "type": "Term", "label": "Specific energy", "properties": { "id": "specific-energy", "name": "Specific energy", "aka": [ "gravimetric energy density" ], "section": "topic-ratings", "definition": "Stored energy per unit mass, in watt-hours per kilogram. Commercial lithium-ion cells range from about 160 Wh/kg for LFP to around 270 Wh/kg for high-nickel chemistries; at pack level the figure drops by a quarter or more.", "unit": "Wh/kg", "related": [ "energy-density", "cell-to-pack-ratio", "specific-capacity", "ragone-plot" ], "lesson": "fundamentals/capacity-and-c-rate/#energy", "url": "https://lemonergy.com/learn/glossary/specific-energy/", "mentions": [] } }, { "id": "term:nominal-energy", "type": "Term", "label": "Nominal energy", "properties": { "id": "nominal-energy", "name": "Nominal energy", "section": "topic-ratings", "definition": "Nominal capacity times nominal voltage, in watt-hours: the headline energy figure on a datasheet. The energy actually delivered depends on the load, the temperature and how the voltage curve is weighted.", "formula": "E = Q × V_nominal", "unit": "Wh", "related": [ "nominal-capacity", "nominal-voltage", "watt-hour", "energy-density" ], "lesson": "fundamentals/capacity-and-c-rate/#energy", "example": { "title": "Turn capacity into a nominal energy", "text": "A 5 Ah cell with a nominal voltage of 3.6 V has 18 Wh of nominal energy. This estimate uses the nominal voltage; delivered energy is the integral of measured terminal voltage multiplied by current." }, "url": "https://lemonergy.com/learn/glossary/nominal-energy/", "mentions": [ "datasheet", "discharge-curve" ] } }, { "id": "term:ragone-plot", "type": "Term", "label": "Ragone plot", "properties": { "id": "ragone-plot", "name": "Ragone plot", "section": "topic-ratings", "definition": "A log–log chart of specific power against specific energy on which each storage technology occupies a region. Capacitors sit high and left, batteries lower and right, and a single cell traces a curve as it is discharged faster.", "related": [ "specific-energy", "specific-power", "rate-capability" ], "url": "https://lemonergy.com/learn/glossary/ragone-plot/", "mentions": [] } }, { "id": "term:areal-loading", "type": "Term", "label": "Areal loading", "properties": { "id": "areal-loading", "name": "Areal loading", "aka": [ "mass loading", "areal capacity" ], "section": "topic-components", "definition": "How much active material, or capacity, an electrode carries per square centimetre of foil, typically 2–5 mAh/cm². Higher loading raises energy density but lengthens the ion path, which limits fast charging.", "unit": "mAh/cm², mg/cm²", "related": [ "coating", "energy-density", "fast-charging", "tortuosity" ], "example": { "title": "Convert mass and area", "text": "200 mg active material over 20 cm² gives 10 mg/cm² loading. State whether the measurement includes one or both coated sides." }, "url": "https://lemonergy.com/learn/glossary/areal-loading/", "mentions": [ "milliampere-hour", "electrode", "active-material" ] } }, { "id": "lesson:fundamentals/capacity-and-c-rate/", "type": "Lesson", "label": "Lesson 2 · Capacity and C-rate", "properties": { "url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/" } }, { "id": "visual:energy", "type": "Visual", "label": "From charge to energy", "properties": { "title": "From charge to energy", "summary": "Voltage connects capacity in ampere-hours to nominal energy in watt-hours.", "readout": "5 Ah × 12 V = 60 Wh nominal energy.", "formula": "E_nominal = Q_nominal V_nominal; actual energy = ∫ VI dt", "note": "Specific energy divides energy by mass; energy density divides it by volume.", "software": { "status": "implemented", "label": "Implemented in battery-core", "body": "nominal_energy_wh multiplies nominal voltage by capacity. Actual discharge energy requires the integral of voltage × current.", "href": "../fundamentals/capacity-and-c-rate/" }, "html": "
Nominal energy versus capacity
Nominal energy versus capacityCapacity (Ah) versus Energy (Wh). 12 V rating. Interpretation follows the graphs.00605120101801524020Capacity (Ah)Energy (Wh)
12 V rating
" } } ] }