Tortuosity

Example

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Use in Lemonergy

Specify phase, direction and boundaries.

This is a reference concept. No executable Lemonergy block has been verified for this term.

Learn it in Lesson 1B · Cell architecture →

Connected concepts

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Bruggeman relation

The common estimate of effective transport in a porous layer: multiply the bulk conductivity or diffusivity by porosity to the power 1.5. Real electrodes often deviate, so measured tortuosity is preferred when available.

Ionic path

The route lithium ions take: out of one electrode’s particles, through the electrolyte in its pores, across the separator and into the particles of the other electrode. The electrons and ions arrive together, so the slower of the two paths limits the cell.

Porosity

The fraction of a layer’s volume that is empty space. In a lithium-ion electrode the pores — roughly 20–35 % of the volume after calendering — are filled with electrolyte, which carries ions to the particles.

Porous electrode

An electrode made of active-material particles, conductive additive and binder with electrolyte-filled pores between them. Its large internal surface is where the reaction happens.

Rate capability

How much of its capacity a cell can still deliver as the C-rate rises. It is measured by discharging at a series of rates and falls faster for thick, dense electrodes and at low temperature.

References & further reading

Technical references

1. Modeling of Galvanostatic Charge and Discharge of the Lithium/Polymer/Insertion Cell

   Marc Doyle, Thomas F. Fuller, John Newman · Journal of The Electrochemical Society · 1993

   Technical reference · Porous-electrode transport and insertion-cell modeling; foundational work rather than a specification for a particular commercial cell.

Further reading on this topic

These sources provide broader context; they are not presented as citations for every statement in this entry.

2. Quantities, Units and Symbols in Physical Chemistry, 3rd edition, 2nd printing

   IUPAC · 2011

   Topic background · Physical-chemistry notation, thermodynamics, electrochemistry and transport quantities.