A Molecular Model of Secondary Battery Cycle-life Pointing Towards a Final Regularity Resembling Carnot-efficiency

28 June 2021, Version 2
This content is a preprint and has not undergone peer review at the time of posting.


A transition state theory-influenced ideal model of battery cycle-life is outlined and validated by example of the Panasonic NCR18650B Li-battery cell, which shows after 500 cycles a residual capacity of 68.2 % at 100 % depth of discharge (DoD) as by its datasheet. The ideal model, which bases on a minimum failure causality of one reaction event failing per half-cycle, overstates on the logarithmic scale by just 1.9 % for the conditions given, corresponding to an ideal cycle-life of 563 cycles. Generalization of the model towards DoD-ranges yields for the exemplary (70; 30) % and (100; 60) % margins the cycle-life values of 43252 and 23480, respectively. Because the model relies solely on natural constants, temperature(s) and C-rate(s), the conclusion is drawn that a thermodynamic final regularity similar to Carnot-efficiency governs secondary battery cycle-life; this is in contrast to hitherto academic consensus opinion attesting the matter a basically empiric nature.


Eyring equation
secondary battery
Secondary Batteries
cycle-life performance
Reversible Energy Storage
Carnot efficiency
equilibrium thermodynamics
Eyring theory formalism
battery cycle-life

Supplementary materials

Exemplary plot of equations 13, 15a and 15b
This graphic illustrates how the distribution function of cycle-life develops from a quadratic approach towards its final form of a negated e-function, in figures of the discussed example.


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