Calendar aging

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Separate mechanisms, observations and fitted models.

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Learn it in Lesson 4 · Battery aging →

Connected concepts

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Arrhenius law

The rule that a rate constant is proportional to exp(−Ea/RT), so a thermally activated reaction speeds up steeply with temperature. Near room temperature many degradation reactions roughly double their rate for every +10 °C.

Calendar life

How long a cell lasts in years, regardless of cycling, before it reaches its end-of-life criterion. It is set by calendar aging, which runs fastest at high temperature and high state of charge.

Cycle aging

Degradation caused by charging and discharging: mechanical strain in the particles, fresh SEI on cracked surfaces and, at high rate or low temperature, lithium plating. It scales with charge throughput and grows with depth of discharge and C-rate.

Solid–electrolyte interphase

A film of electrolyte reaction products on the negative-electrode particles — graphite, and also silicon or lithium metal. It protects the electrode from further reaction but grows slowly for the whole life of the cell, consuming cyclable lithium.

Square-root-of-time law

The observation that SEI-driven capacity loss in storage grows roughly with the square root of time, because the growing film slows its own growth. A cell that lost 4 % in its first year will lose about 1.7 % more in the second.

References & further reading

Technical references

1. Lithium ion battery degradation: what you need to know

   Physical Chemistry Chemical Physics · 2021

   Technical reference · Degradation mechanisms, modes, operational effects and their interactions.