Electrodes#

An electrode is the component of an electrochemical system where oxidation and reduction reactions occur. Electrodes act as interfaces between electronic and ionic conductors — storing, releasing, or transferring charge during operation.

In the ontology, electrodes are represented as physical objects that can be decomposed into functional and structural subparts such as coatings, current collectors, and materials.

Common electrode types include:

  • Anode — oxidation occurs here (negative during discharge).

  • Cathode — reduction occurs here (positive during discharge).

  • Reference Electrode — provides a stable reference potential in measurement cells.

Conceptual Structure#

An electrode typically consists of:

  • Current Collector — conducts electrons to/from the external circuit.

  • Coating — the functional layer that includes: - Active Material — participates in electrochemical reactions. - Binder — provides mechanical integrity. - Conductive Additive — enhances electronic conductivity.

Structure of an electrode

Example structure of a coated electrode.#

Guidelines for Use#

Follow these steps when describing an electrode:

1. Identify the Electrode#

Start by selecting the appropriate class, such as Electrode, Anode, or Cathode. If the electrode has one or more coatings, use the subclasses SingleCoatedElectrode or DoubleCoatedElectrode.

{
  "@context": "https://w3id.org/emmo/domain/electrochemistry/context",
  "@type": "Electrode"
}

2. Assign Properties#

Attach measurable or conventional properties using hasProperty. Common examples include thickness, porosity, mass loading, or specific capacity.

{
  "@context": "https://w3id.org/emmo/domain/electrochemistry/context",
  "@type": "Electrode",
  "hasProperty": [
    {
      "@type": "Thickness",
      "hasNumericalPart": {
        "@type": "RealData",
        "hasNumberValue": 50
      },
      "hasMeasurementUnit": "emmo:MicroMetre"
    }
  ]
}

3. Define Structural Composition#

Link the electrode to its subparts using domain-specific relations such as:

  • hasCoating

  • hasCurrentCollector

  • hasActiveMaterial

  • hasBinder

  • hasAdditive

These are subproperties of `hasPart`, which allows reasoning systems to automatically infer part–whole hierarchies.

Representation Patterns#

Single Coated Electrode#

A SingleCoatedElectrode has one functional coating on its current collector.

{
  "@context": "https://w3id.org/emmo/domain/electrochemistry/context",
  "@type": "SingleCoatedElectrode",
  "hasCoating": {
    "@type": "ElectrodeCoating",
    "hasActiveMaterial": { "@type": "LiFePO4" },
    "hasBinder": { "@type": "PVDF" },
    "hasAdditive": { "@type": "CarbonBlack" }
  },
  "hasCurrentCollector": { "@type": "AluminiumFoil" },
  "hasProperty": [
    {
      "@type": "Thickness",
      "hasNumericalPart": { "@type": "RealData", "hasNumberValue": 75 },
      "hasMeasurementUnit": "emmo:MicroMetre"
    }
  ]
}

This example describes a lithium iron phosphate (LFP) cathode with a single coating applied to an aluminum current collector.

Double Coated Electrode#

A DoubleCoatedElectrode has two coatings applied on opposite sides of the same current collector — a common configuration in both laboratory and commercial electrodes.

{
  "@context": "https://w3id.org/emmo/domain/electrochemistry/context",
  "@type": "DoubleCoatedElectrode",
  "hasCoating": [
    {
      "@type": "BaseCoating",
      "hasActiveMaterial": { "@type": "LiNi0.8Mn0.1Co0.1O2" },
      "hasBinder": { "@type": "PVDF" },
      "hasAdditive": { "@type": "CarbonBlack" }
    },
    {
      "@type": "TopCoating",
      "hasActiveMaterial": { "@type": "LiMn2O4" },
      "hasBinder": { "@type": "PVDF" },
      "hasAdditive": { "@type": "CarbonBlack" }
    }
  ],
  "hasCurrentCollector": { "@type": "AluminiumFoil" },
  "hasProperty": [
    {
      "@type": "Thickness",
      "hasNumericalPart": { "@type": "RealData", "hasNumberValue": 150 },
      "hasMeasurementUnit": "emmo:MicroMetre"
    }
  ]
}

Here, the two coatings can represent different active materials or formulations applied to each side of the foil. This pattern can also be extended for gradient or layered electrodes.

Reasoning Implications#

Because hasCoating, hasCurrentCollector, hasActiveMaterial, etc. are all subproperties of `hasPart`, reasoning engines can infer relationships such as:

::

If Electrode hasCoating Coating, and Coating hasActiveMaterial Material, then Electrode hasPart Material.

This enables queries like “find all electrodes that contain a given active material,” regardless of how deeply it is nested in the structure.

Best Practices#

  • Use Anode and Cathode when polarity or reaction direction is known; use Electrode when not.

  • When modeling coatings, prefer SingleCoatedElectrode or DoubleCoatedElectrode subclasses for clarity.

  • Include hasCurrentCollector even for self-supporting electrodes to maintain consistency.

  • Use hasCoating to encapsulate active, binder, and additive materials.

  • Represent measurable properties like thickness or porosity through hasProperty.

  • If describing manufacturing variants, you may define coating subclasses (e.g., BaseCoating, TopCoating) for specific architectures.

Summary#

Electrodes link chemical composition, geometric structure, and functional role within electrochemical systems. The ontology captures this hierarchy through well-defined relations and specialized subclasses.

Concept | Relation | Example |

|----------|-----------|----------| | Electrode | hasCoating | functional layer of active material | | SingleCoatedElectrode | hasCoating | one coating on current collector | | DoubleCoatedElectrode | hasCoating | coatings on both sides | | ElectrodeCoating | hasActiveMaterial, hasBinder, hasAdditive | describes internal composition | | Electrode | hasCurrentCollector | connects to substrate foil |

This structure allows for rich, reusable, and machine-interpretable descriptions of electrode architectures across different experimental, modeling, and manufacturing contexts.