{
  "node": {
    "id": "term:nickel-hydrogen",
    "type": "Term",
    "label": "Nickel–hydrogen battery",
    "properties": {
      "id": "nickel-hydrogen",
      "name": "Nickel–hydrogen battery",
      "abbr": "NiH₂",
      "aka": [
        "Ni–H₂"
      ],
      "section": "topic-other-chemistries",
      "definition": "A cell pairing a nickel oxyhydroxide positive with hydrogen gas on a platinum-catalysed electrode, sealed in a pressure vessel whose pressure tracks state of charge. With no negative electrode to wear out it lasts tens of thousands of cycles, powering satellites, the Hubble Space Telescope and, until lithium-ion replaced it, the International Space Station.",
      "related": [
        "nickel-metal-hydride",
        "cycle-life",
        "fuel-cell",
        "state-of-charge",
        "stationary-storage"
      ],
      "url": "https://lemonergy.com/learn/glossary/nickel-hydrogen/",
      "mentions": [
        "electrode",
        "negative-electrode"
      ]
    }
  },
  "edges": [
    {
      "id": "edge:5952",
      "source": "term:nickel-hydrogen",
      "target": "topic:topic-other-chemistries",
      "type": "belongsTo",
      "properties": {
        "sourceFile": "terms.json"
      }
    },
    {
      "id": "edge:5953",
      "source": "term:nickel-hydrogen",
      "target": "term:nickel-metal-hydride",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5954",
      "source": "term:nickel-hydrogen",
      "target": "term:cycle-life",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5955",
      "source": "term:nickel-hydrogen",
      "target": "term:fuel-cell",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5956",
      "source": "term:nickel-hydrogen",
      "target": "term:state-of-charge",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5957",
      "source": "term:nickel-hydrogen",
      "target": "term:stationary-storage",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:mentions/nickel-hydrogen/electrode",
      "source": "term:nickel-hydrogen",
      "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/nickel-hydrogen/negative-electrode",
      "source": "term:nickel-hydrogen",
      "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"
      }
    }
  ],
  "neighbors": [
    {
      "id": "topic:topic-other-chemistries",
      "type": "Topic",
      "label": "Other and emerging chemistries",
      "properties": {
        "id": "topic-other-chemistries",
        "name": "Other and emerging chemistries",
        "lede": "Batteries beyond today’s lithium-ion: lead, nickel and primary cells, flow and metal–air batteries, solid-state and lithium-metal cells, and the multivalent and sodium chemistries in development.",
        "context": "Do not carry lithium-ion assumptions into every chemistry.",
        "example": "Two chemistries can meet the same energy target with different voltage windows and charge termination.",
        "lesson_url": "https://lemonergy.com/learn/fundamentals/cell-anatomy/",
        "lesson_label": "Open cell anatomy"
      }
    },
    {
      "id": "term:nickel-metal-hydride",
      "type": "Term",
      "label": "Nickel–metal hydride battery",
      "properties": {
        "id": "nickel-metal-hydride",
        "name": "Nickel–metal hydride battery",
        "abbr": "NiMH",
        "section": "topic-other-chemistries",
        "definition": "A 1.2 V aqueous cell with a nickel hydroxide positive electrode and a hydrogen-absorbing alloy negative. It powered hybrid cars for two decades and is tolerant of abuse, but lithium-ion stores two to three times more energy per kilogram.",
        "related": [
          "hybrid-vehicle",
          "memory-effect",
          "specific-energy",
          "bipolar-battery",
          "nickel-hydrogen"
        ],
        "url": "https://lemonergy.com/learn/glossary/nickel-metal-hydride/",
        "mentions": [
          "electrode",
          "positive-electrode"
        ]
      }
    },
    {
      "id": "term:cycle-life",
      "type": "Term",
      "label": "Cycle life",
      "properties": {
        "id": "cycle-life",
        "name": "Cycle life",
        "section": "topic-ratings",
        "definition": "The number of full charge–discharge cycles a cell completes before its capacity falls to a stated fraction, usually 80 %, of its initial value under defined conditions. LFP cells reach several thousand cycles; high-energy NMC fewer.",
        "unit": "cycles",
        "related": [
          "end-of-life",
          "capacity-fade",
          "depth-of-discharge",
          "calendar-life",
          "equivalent-full-cycle",
          "cycle-life-test"
        ],
        "url": "https://lemonergy.com/learn/glossary/cycle-life/",
        "mentions": []
      }
    },
    {
      "id": "term:fuel-cell",
      "type": "Term",
      "label": "Fuel cell",
      "properties": {
        "id": "fuel-cell",
        "name": "Fuel cell",
        "section": "topic-other-chemistries",
        "definition": "An electrochemical converter that makes electricity from a fuel, usually hydrogen, and oxygen as long as both are supplied, rather than storing energy in its electrodes. Fuel-cell vehicles still carry a battery to buffer power.",
        "related": [
          "flow-battery",
          "hybrid-vehicle",
          "redox-reaction"
        ],
        "url": "https://lemonergy.com/learn/glossary/fuel-cell/",
        "mentions": []
      }
    },
    {
      "id": "term:state-of-charge",
      "type": "Term",
      "label": "State of charge",
      "properties": {
        "id": "state-of-charge",
        "name": "State of charge",
        "abbr": "SOC",
        "section": "topic-state",
        "definition": "How full a cell is, as a fraction of its available capacity. State of charge, like temperature, affects how fast a stored cell ages.",
        "unit": "%",
        "related": [
          "depth-of-discharge",
          "ocv-soc-curve",
          "coulomb-counting",
          "state-of-health",
          "bms"
        ],
        "lesson": "fundamentals/battery-aging/#storage-soc",
        "example": {
          "title": "Interpret a charge inventory",
          "text": "If available capacity is 5 Ah and 3 Ah remains by the chosen estimator, SOC is 60%. A different estimate of available capacity changes this percentage, so compare SOC values only with the capacity convention recorded."
        },
        "url": "https://lemonergy.com/learn/glossary/state-of-charge/",
        "mentions": [
          "usable-capacity"
        ]
      }
    },
    {
      "id": "term:stationary-storage",
      "type": "Term",
      "label": "Stationary storage",
      "properties": {
        "id": "stationary-storage",
        "name": "Stationary storage",
        "abbr": "BESS",
        "aka": [
          "battery energy storage system",
          "ESS"
        ],
        "section": "topic-applications",
        "definition": "Batteries installed in a fixed place — a container at a solar farm, a cabinet in a home — to shift energy in time or support the grid. LFP cells dominate because cost per cycle and safety matter more than mass.",
        "related": [
          "lfp",
          "energy-management-system",
          "inverter",
          "energy-arbitrage",
          "long-duration-storage",
          "ul-9540a"
        ],
        "url": "https://lemonergy.com/learn/glossary/stationary-storage/",
        "mentions": []
      }
    },
    {
      "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"
        ]
      }
    }
  ]
}