{
  "node": {
    "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"
      ]
    }
  },
  "edges": [
    {
      "id": "edge:786",
      "source": "term:nickel-metal-hydride",
      "target": "topic:topic-other-chemistries",
      "type": "belongsTo",
      "properties": {
        "sourceFile": "terms.json"
      }
    },
    {
      "id": "edge:787",
      "source": "term:nickel-metal-hydride",
      "target": "term:hybrid-vehicle",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:788",
      "source": "term:nickel-metal-hydride",
      "target": "term:memory-effect",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:789",
      "source": "term:nickel-metal-hydride",
      "target": "term:specific-energy",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:790",
      "source": "term:nickel-metal-hydride",
      "target": "term:bipolar-battery",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:791",
      "source": "term:nickel-metal-hydride",
      "target": "term:nickel-hydrogen",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:mentions/nickel-metal-hydride/electrode",
      "source": "term:nickel-metal-hydride",
      "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-metal-hydride/positive-electrode",
      "source": "term:nickel-metal-hydride",
      "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"
      }
    }
  ],
  "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:hybrid-vehicle",
      "type": "Term",
      "label": "Hybrid and plug-in hybrid vehicle",
      "properties": {
        "id": "hybrid-vehicle",
        "name": "Hybrid and plug-in hybrid vehicle",
        "abbr": "HEV, PHEV",
        "section": "topic-applications",
        "definition": "A hybrid pairs an engine with a small battery, around 1 kWh, that is cycled hard for power rather than energy; a plug-in hybrid adds a 10–25 kWh pack that can be charged from the grid for electric-only driving. Their cells are designed for power and life rather than energy.",
        "related": [
          "electric-vehicle",
          "specific-power",
          "nickel-metal-hydride",
          "cycle-life",
          "48v-system"
        ],
        "url": "https://lemonergy.com/learn/glossary/hybrid-vehicle/",
        "mentions": [
          "kilowatt-hour"
        ]
      }
    },
    {
      "id": "term:memory-effect",
      "type": "Term",
      "label": "Memory effect",
      "properties": {
        "id": "memory-effect",
        "name": "Memory effect",
        "section": "topic-charging",
        "definition": "A loss of usable capacity in nickel–cadmium cells repeatedly recharged from the same partial state. Lithium-ion cells do not show it in any practical sense, though LFP has a small related voltage memory.",
        "related": [
          "nickel-cadmium",
          "nickel-metal-hydride",
          "lfp"
        ],
        "url": "https://lemonergy.com/learn/glossary/memory-effect/",
        "mentions": [
          "usable-capacity"
        ]
      }
    },
    {
      "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:bipolar-battery",
      "type": "Term",
      "label": "Bipolar battery",
      "properties": {
        "id": "bipolar-battery",
        "name": "Bipolar battery",
        "aka": [
          "bipolar electrode",
          "bipolar stacking"
        ],
        "section": "topic-other-chemistries",
        "definition": "A battery built from bipolar electrodes: one shared current collector carries positive material on one face and negative material on the other, so stacked layers form cells in series inside one housing. Current flows straight through the stack instead of through tabs and busbars, cutting resistance and parts; Toyota’s 2021 Aqua hybrid used a bipolar nickel–metal hydride pack.",
        "related": [
          "series-parallel",
          "current-collector",
          "nickel-metal-hydride",
          "solid-state-battery",
          "busbar",
          "lead-acid"
        ],
        "url": "https://lemonergy.com/learn/glossary/bipolar-battery/",
        "mentions": []
      }
    },
    {
      "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"
        ]
      }
    },
    {
      "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: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"
        ]
      }
    }
  ]
}