Thermodynamic Fundamentals of Differential Capacity Analysis
Differential capacity analysis extracts thermodynamic phase boundaries to deconvolve lithium inventory loss from active material degradation non destructively.
Partial Molar Enthalpy
Meaning
Change in the total heat content of a system per mole of a specific component added at constant temperature and pressure. Calculating the partial molar enthalpy of lithium in host electrodes yields the thermal energy released during insertion steps. This calculation is a standard part of modeling the thermal behavior of cells during fast charging.
Thermodynamic Gradient
Heat generation during electrochemical cycling consists of both reversible and irreversible components. The reversible portion depends directly on the partial molar enthalpy of the intercalating ions. This relationship means that as the state of charge changes, the local heat generation rate also shifts.
Heat Release
Accurate measurements of heat release are obtained using isothermal microcalorimetry during slow discharge experiments. Calculating the partial molar enthalpy helps engineers design cooling systems that can handle the peak thermal loads. This is particularly important for high-power applications where the cell temperature must be kept within safe limits.
Operating Limit
At high rates of charge, irreversible heating dominates over the thermodynamic effects. This dominance restricts the usefulness of the partial molar enthalpy calculations to the lower-rate regions of the cycle. This boundary must be considered when designing real-time thermal management software for electric vehicle packs, as the software must transition to empirical thermal models when the current density exceeds the threshold of thermodynamic equilibrium.