Coulombic efficiency (CE) shares a direct relationship with battery efficiency. Hence a high CE means a longer battery cycle life, or the period between recharges. However, we don’t yet fully understand how this relates to battery degradation. Much battery research attempts to resolve this mystery.
Battery Scientists Investigate Coulombic Efficiency
Researchers may compare different batteries and types under matching conditions. They typically observe two trends. These are loss of the active material, and accompanying battery degradation. This short post outlines the roles coulombic efficiency and capacity degradation play.
All batteries experience efficiency losses as they age. CE is the efficacy with which charge electrons transfer. Moreover, we know that ultra-fast charging reduces this rate, and hence battery cycle life. Deteriorating charge-life is a hassle when it comes to phones and computers. However it becomes a far more serious matter in the context of battery storage.
More About the CE in Rechargeable Batteries
Lithium-ion batteries have one of the best coulombic efficiency ratings. Indeed, this can be as high as 99% when charging with a moderate current at a cool ambient temperature. Interestingly enough, Panasonic found the rating improved slightly after a number of cycles.
However, these tests often run over hundreds of repetitions. This makes repeating them at home a challenge for our patience. Although the CE efficiency of lead-acid batteries is 10% lower than lithium-ion there are similarities. It’s a generally accepted fact that batteries become warmer as they approach their full charge, and heat has an adverse effect on CE efficacy.
For these reasons batteries are therefore most efficient between 30% and 70% of their charge. This is not always an ideal situation from a user perspective. Perhaps we are only at the early stage of truly efficient batteries, using coulombic efficiency as our guide.
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Preview Image: Old Battery Technology (Dennis Jarvis)
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