Battery knowledge · Electrochemistry fundamentals
Charge transfer
The step in which an electron crosses the interface between electrode and electrolyte as an ion is inserted or removed. Its resistance appears as a semicircle in impedance spectra and grows as films thicken and the cell cools.
Example
Overpotential drives reaction current
At equilibrium net current is zero. At +50 mV, current density is 2.268 A/m².
Fixed concentrations, symmetric transfer coefficients and no transport limitation.
Explore the graph
At equilibrium, forward and reverse reaction currents cancel.
At equilibrium net current is zero. At +50 mV, current density is 2.268 A/m².
i = 2i₀ sinh(Fη / 2RT)
Illustrative model. Fixed concentrations, symmetric transfer coefficients and no transport limitation.
Use in Lemonergy
Lemonergy Studio blocks
Single-particle cell worked example
Native spherical solid diffusion and Butler-Volmer kinetics with tabulated electrode OCPs. Isothermal material parameters; no electrolyte transport, aging or conserving adapter.
Blocks to use
- Single-particle cell
Solves spherical solid diffusion in separate negative and positive representative particles with conservative radial finite volumes. Opposite Faradaic fluxes transfer lithium between electrodes. Surface stoichiometries drive tabulated OCPs and Butler-Volmer overpotentials; temperature is prescribed.
Inputs & settings
- Use the parameter values in the block reference.
- Bundled example verified on the production release of 28 October 2026.
This overview identifies the components to use. Follow the example in Lemonergy for their connections and settings.
- Review the block inputs, units and model limits.
- Open the Studio example and run its bundled model.
- Compare the output channels with the numerical checks; change one input and run again.
Example. Use the defaults below with Signed cell current = 1 A, Kinetics temperature = 298.15 K. At 0 s, Terminal voltage is 3.912048435 V. Additional checks are listed below.
Observe. Inspect the outputs and numerical checks on the block reference page.
Fixed solid diffusion and material coefficients; no electrolyte transport, aging, thermal state or conserving boundary adapter. Surface concentrations must stay strictly inside their physical range. The cited paper explains model assumptions and a richer electrolyte extension; this block implements the stated solid-only model. The example verifies numerical behavior for synthetic parameters. Cell characterization and validation for an intended use are separate tasks.
Open Studio example →References & further reading
Further reading on this topic
These sources provide broader context; they are not presented as citations for every statement in this entry.
- Quantities, Units and Symbols in Physical Chemistry, 3rd edition, 2nd printing
IUPAC · 2011
Topic background · Physical-chemistry notation, thermodynamics, electrochemistry and transport quantities.