Battery knowledge · Electrochemistry fundamentals
Entropy coefficient
The change of open-circuit voltage with temperature, dE/dT, usually a fraction of a millivolt per kelvin and varying with state of charge. It sets the reversible heat a cell absorbs or releases, which can be a large share of total heat at low current. [1]
- Unit
- mV/K
- Relationship
- q_rev = I·T·(dE/dT)
Example
Interpretation & limits
- The glossary plot takes positive heat as heat released. Other sources may use positive-discharge current and a different written sign.
Explore the graph
The OCV temperature slope sets the reversible heat term for the stated current convention.
At +10 A the stated term is 0.2981 W. Reversing current reverses the term.
q_reversible = I × T × (dE/dT)
Illustrative model. Positive current charges the cell; positive q means heat released. Check the solver convention before combining it with other heat terms. The coefficient is held constant across SOC.
Use in Lemonergy
Connect reaction sites and transport paths.
This is a reference concept. No executable Lemonergy block has been verified for this term.
References & further reading
Technical references
- A General Energy Balance for Battery Systems
Dawn Bernardi, Ellen Pawlikowski, John Newman · Journal of The Electrochemical Society · 1985
Technical reference · Battery energy balance and irreversible and reversible heat contributions. Reduced thermal models require explicit assumptions and current-sign conventions.
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.