Electrochemical systems
Electrochemical systems
Scientific articles in which we characterized batteries, capacitors and fuel cells
Abstract
Presented is a lithium-ion battery degradation model, based on irreversible thermodynamics, which was experimentally verified, using commonly measured operational parameters. The methodology, applicable to all lithium-ion batteries of all chemistries and composition, combined fundamental thermodynamic principles, with the Degradation–Entropy Generation theorem, to relate instantaneous capacity fade (loss of useful charge-holding capacity) in the lithium-ion battery, to the irreversible entropy generated via the underlying dissipative physical processes responsible for battery degradation. Equations relating capacity fade—aging—to battery cycling were also formulated and verified. To show the robustness of the approach, nonlinear data from abusive and inconsistent battery cycling was measured and used to verify formulations. A near 100% agreement between the thermodynamic battery model and measurements was achieved. The model also gave rise to new material and design parameters to characterize all lithium-ion batteries.
Abstract
This article details a lead-acid battery degradation model based on irreversible thermodynamics, which is then verified experimentally using commonly measured operational parameters. The model combines thermodynamic first principles with the Degradation-Entropy Generation theorem, to relate instantaneous and cyclic capacity fade (loss of useful charge-holding capacity) in the lead-acid battery to the entropy generated via the underlying dissipative physical processes responsible for battery degradation. Equations relating capacity fade to battery cycling are also formulated and verified. To show robustness of the approach, nonlinear data from uncontrolled and severely abusive battery cycling—including overdischarge—was measured and used to verify formulations. A near 100% agreement between the thermodynamic battery model and measurements is achieved. The model also gives rise to new material and design parameters to characterize all lead-acid batteries.
Abstract
This study demonstrates a thermodynamics-based instantaneous characterization of electrochemical power sources (EPSs) of various chemistries, sizes, scales and configurations, cycled at different rates. Recently proposed Degradation-Entropy Generation (DEG) methodology is reviewed and characteristic DEG elements are generalized to all electrochemical power sources, experimentally verified via uncontrolled cycling of nickel-metal hydride batteries, lead-acid batteries, lithium-ion batteries, supercapacitors and fuel cells. Dissipation factor and entropic efficiency are introduced as new performance/degradation characterization factors in addition to existing DEG geometric and parametric elements. While data arise from several different power source types and process rates, results are similar and characteristic of system type and performance, consistently verifying and further elucidating anticipated system behaviors. Previously observed near-100% fit of experimental data to theoretical formulations persists in this study. A normalized DEG domain is introduced and compared to Voltage–Charge curves and Ragone plots in simultaneous comparative analysis of the various systems under different operational conditions. DEG methods can be used to adequately quantify the dissipative and degradation tendencies of electrochemical power sources for performance analysis and optimization.
Abstract
Lithium-ion batteries are consistently cycled and characterized using the Degradation-Entropy Generation (DEG) methodology. Irregular and abusive cycling was recently published in the literature. Here, DEG capacity fade is compared to Coulomb-counted capacity fade, and DEG elements—DEG coefficients Bi, dissipation factor J, entropic efficiency ηS—are evaluated and interpreted for battery performance and degradation analyses. The effect of cycling rate (C-rate) on the DEG elements is discussed using measured data from three same-model lithium-ion batteries discharged at different C-rates. The results and features of the DEG methodology accord with established lithium-ion battery behaviors and the laws of thermodynamics, rendering the approach easily adaptable to battery analysis.