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Home > News > Understanding the cycle life and Performance Factors of Lithium-Ion and LIFEPO4 Batteries

Understanding the cycle life and Performance Factors of Lithium-Ion and LIFEPO4 Batteries

2017-10-18

Understanding the cycle life and Performance Factors of Lithium-Ion and LIFEPO4 Batteries


Over time, the performance of lithium-ion batteries gradually degrades to varying extents, representing a slow yet irreversible progression. 

Lifespan, a pivotal performance metric, is presently gauged in accordance with industry norms, which define it by the number of full cycles (with 80% capacity retention)

 during standard charge-discharge cycle tests.


Nevertheless, real-world operating scenarios deviate substantially from these standardized tests. Fluctuations in environmental factors, operating speeds, 

charge-discharge depths, and other variables make it infeasible to directly ascertain the lifespan of lithium-ion batteries in practical use merely through cycle counting.

Take, for instance, a mobile phone battery fully charged at 100%. Draining it to 0% and subsequently recharging it back to 100% constitutes one full charge-discharge cycle. 

Here, both the battery cycle count and the charge count stand at 1. However, if in the first instance, the battery is used until it reaches 40% and then charged back to 100%, 

and in the second instance, depleted to 60% and recharged to 100%, these two usage episodes together still amount to one complete charge-discharge cycle. In this scenario, 

the battery cycle count remains 1, while the charge count totals 2.


The equivalent full cycle count for lithium-ion batteries is computed by cumulatively summing the capacity under diverse operating conditions and dividing it by the battery's nominal capacity. 

A single 100% discharge/charge cycle can involve one, two, three, or even more charging events. 

Ultimately, it is the equivalent full cycle count at 80% of the initial capacity that dictates the lifespan of a lithium-ion battery, rather than the sheer number of charges.


Research on the lifespans of various batteries under different temperature, charge-discharge depth, and rate conditions reveals that LFP batteries boast longer cycle lifespans, 

spanning from 2500 to 9000 EFC (Equivalent Full Cycles), with most LFP batteries yet to reach the 80% capacity threshold. 


NCA batteries fare relatively poorly, with lifespans ranging from 250 to 1500 EFC, and NMC batteries fall within the 200 to 2500 EFC range. 

All batteries exhibit linear degradation patterns, albeit with marginally accelerated degradation rates at the commencement and conclusion of cycles.


The capacity degradation rate of LFP batteries ascends with rising temperatures, whereas that of NMC batteries declines. NCA batteries, within the experimental parameters, 

do not display a pronounced temperature dependency. For all batteries, the capacity degradation rate amplifies with deeper discharge depths.


Rapid volume changes exert augmented pressure on the electrodes, and thus, higher discharge rates are anticipated to hasten capacity degradation. 

NMC and LFP batteries demonstrate a relatively lower susceptibility to discharge rates, yet for NCA batteries, the capacity degradation rate diminishes with elevated discharge rates.


The tendencies of battery dependence on temperature, discharge depth, and discharge rate diverge across different chemical systems. Findings from one chemical system cannot be indiscriminately 

extrapolated to all lithium-ion batteries. In the 15°C to 35°C temperature bracket, the capacity degradation rate of LFP batteries climbs with increasing temperatures,

 while that of NMC batteries drops, signifying the presence of disparate dominant degradation mechanisms. NMC and NCA batteries exhibit a more pronounced dependence on discharge depth and are more responsive to full SOC (State of Charge) range cycling compared to LFP batteries.


In summary, it is crucial to underscore that one charge-discharge cycle pertains to a complete charge-discharge procedure of a lithium-ion battery. 

This implies that when the battery attains a 100% state of charge, it has accomplished one charging cycle, albeit not necessarily via a solitary charge

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