{ "node": { "id": "term:np-ratio", "type": "Term", "label": "N/P ratio", "properties": { "id": "np-ratio", "name": "N/P ratio", "section": "topic-components", "definition": "The areal capacity of the negative electrode divided by that of the positive electrode facing it, usually set at 1.05–1.15. The excess negative capacity ensures there is always a graphite site for every lithium ion on charge, which guards against lithium plating.", "formula": "N/P = Q_neg / Q_pos", "related": [ "areal-loading", "lithium-plating", "cell-design", "overhang-alignment", "anode-overhang" ], "example": { "title": "Compare electrode capacity budgets", "text": "A negative-electrode capacity of 3.3 mAh/cm² paired with a positive-electrode capacity of 3.0 mAh/cm² gives an N/P ratio of 1.10. The chosen capacity definitions and operating windows must match." }, "url": "https://lemonergy.com/learn/glossary/np-ratio/", "mentions": [ "electrode", "negative-electrode", "positive-electrode", "graphite" ] } }, "edges": [ { "id": "edge:588", "source": "term:np-ratio", "target": "topic:topic-components", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:589", "source": "term:np-ratio", "target": "term:areal-loading", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:590", "source": "term:np-ratio", "target": "term:lithium-plating", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:591", "source": "term:np-ratio", "target": "term:cell-design", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:592", "source": "term:np-ratio", "target": "term:overhang-alignment", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:593", "source": "term:np-ratio", "target": "term:anode-overhang", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/np-ratio/electrode", "source": "term:np-ratio", "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/np-ratio/negative-electrode", "source": "term:np-ratio", "target": "term:negative-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/np-ratio/positive-electrode", "source": "term:np-ratio", "target": "term:positive-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/np-ratio/graphite", "source": "term:np-ratio", "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:598", "source": "term:np-ratio", "target": "visual:electrode-balance", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } } ], "neighbors": [ { "id": "topic:topic-components", "type": "Topic", "label": "Cell components and electrode materials", "properties": { "id": "topic-components", "name": "Cell components and electrode materials", "lede": "What a cell is physically made of — active materials, binders, additives, foils and tabs — and how its electrodes are put together.", "context": "Connect each material with its function.", "example": "Electrons travel through additive, foil and tab; ions use electrolyte and separator pathways.", "lesson_url": "https://lemonergy.com/learn/fundamentals/cell-anatomy/", "lesson_label": "Open cell anatomy" } }, { "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": "term:lithium-plating", "type": "Term", "label": "Lithium plating", "properties": { "id": "lithium-plating", "name": "Lithium plating", "section": "topic-aging", "definition": "Lithium metal depositing on the negative-electrode surface instead of intercalating into it. It is promoted by charging at low temperature or high current.", "related": [ "dendrite", "fast-charging", "intercalation", "np-ratio", "dead-lithium", "electrodeposition" ], "lesson": "fundamentals/battery-aging/#plating", "url": "https://lemonergy.com/learn/glossary/lithium-plating/", "mentions": [] } }, { "id": "term:cell-design", "type": "Term", "label": "Cell design", "properties": { "id": "cell-design", "name": "Cell design", "section": "topic-manufacturing", "definition": "Choosing the chemistry, electrode loadings, porosities, N/P ratio, separator, electrolyte volume and format that together meet an energy, power, life, safety and cost target. Each choice trades against the others: thicker electrodes raise energy and lower power.", "related": [ "np-ratio", "areal-loading", "porosity", "energy-density", "specific-power" ], "url": "https://lemonergy.com/learn/glossary/cell-design/", "mentions": [ "electrode", "separator", "electrolyte" ] } }, { "id": "term:overhang-alignment", "type": "Term", "label": "Electrode overhang and alignment", "properties": { "id": "overhang-alignment", "name": "Electrode overhang and alignment", "aka": [ "separator overhang", "alignment tolerance", "electrode registration" ], "section": "topic-manufacturing", "definition": "The margins by which, on every edge, the separator extends beyond the negative electrode and the negative beyond the positive, and the placement tolerance that must preserve them. If a positive edge ever sits outside the negative, lithium plates there; if the separator falls short, the electrodes can touch. Lines check alignment by camera and X-ray.", "related": [ "stacking", "winding", "lithium-plating", "np-ratio", "separator", "anode-overhang" ], "url": "https://lemonergy.com/learn/glossary/overhang-alignment/", "mentions": [ "electrode", "negative-electrode" ] } }, { "id": "term:anode-overhang", "type": "Term", "label": "Anode overhang", "properties": { "id": "anode-overhang", "name": "Anode overhang", "aka": [ "negative electrode overhang", "overhang effect" ], "section": "topic-components", "definition": "The margin, of the order of a millimetre, by which the negative electrode extends beyond the positive electrode at every edge, so lithium leaving the cathode edge always finds graphite to enter rather than plating. The overhang slowly soaks up and gives back lithium itself, which causes small apparent capacity drifts in storage and efficiency tests.", "related": [ "np-ratio", "lithium-plating", "cell-design", "coulombic-efficiency", "calendar-aging" ], "url": "https://lemonergy.com/learn/glossary/anode-overhang/", "mentions": [ "electrode", "negative-electrode", "positive-electrode", "cathode", "graphite" ] } }, { "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:negative-electrode", "type": "Term", "label": "Negative electrode", "properties": { "id": "negative-electrode", "name": "Negative electrode", "section": "topic-components", "definition": "The electrode at the lower potential, usually graphite on copper foil in a lithium-ion cell. It holds the lithium when the cell is charged and releases it on discharge, and industry calls it the anode.", "related": [ "anode", "graphite", "positive-electrode", "copper-foil" ], "lesson": "fundamentals/cell-anatomy/#anode-cathode", "example": { "title": "Keep the polarity name", "text": "Graphite remains the negative electrode during charge and discharge, while the anode/cathode reaction labels change with operating direction." }, "url": "https://lemonergy.com/learn/glossary/negative-electrode/", "mentions": [ "electrode" ] } }, { "id": "term:positive-electrode", "type": "Term", "label": "Positive electrode", "properties": { "id": "positive-electrode", "name": "Positive electrode", "section": "topic-components", "definition": "The electrode at the higher potential: a lithium metal oxide or phosphate coated on aluminium foil. It is the lithium source when a cell is built, and industry calls it the cathode.", "related": [ "cathode", "cathode-active-material", "negative-electrode", "aluminium-foil" ], "lesson": "fundamentals/cell-anatomy/#anode-cathode", "example": { "title": "Polarity and reaction", "text": "The positive electrode retains its polarity label while its electrochemical reaction reverses between charge and discharge." }, "url": "https://lemonergy.com/learn/glossary/positive-electrode/", "mentions": [ "electrode" ] } }, { "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": "visual:electrode-balance", "type": "Visual", "label": "Compare electrode capacities", "properties": { "title": "Compare electrode capacities", "summary": "A capacity ratio describes how the two facing electrodes are balanced.", "readout": "At N/P = 1.1, negative capacity is 3.3 mAh/cm² for 3 mAh/cm² on the positive side.", "formula": "N/P = Q_negative / Q_positive", "note": "The curves compare authored capacities. They omit utilization, electrode potentials, transport, aging and manufacturing variation.", "software": { "status": "reference", "label": "Reference concept", "body": "This ratio is a reference electrode-design relationship. A ratio alone does not predict plating or establish that an electrode design is safe.", "href": "../chapter-1/" }, "html": "
Areal capacity balance
Areal capacity balanceN/P ratio versus Areal capacity (mAh/cm²). Positive capacity; Negative capacity; Selected N/P. Interpretation follows the graphs.00.82.250.954.51.16.751.2591.4N/P ratioAreal capacity (mAh/cm²)
Positive capacityNegative capacity (dashed)Selected N/P
" } } ] }