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Capacity loss
View on WikipediaCapacity loss or capacity fading is a phenomenon observed in rechargeable battery usage where the amount of charge a battery can deliver at the rated voltage decreases with use.[1][2]
In 2003 it was reported the typical range of capacity loss in lithium-ion batteries after 500 charging and discharging cycles varied from 12.4% to 24.1%, giving an average capacity loss per cycle range of 0.025–0.048% per cycle.[3]
Stress factors
[edit]Capacity fading in Li-ion batteries occurs by a multitude of stress factors, including ambient temperature, discharge C-rate, and state of charge (SOC).
Capacity loss is strongly temperature-dependent. Aging rates increase as temperatures rise or fall above or below 25 °C. [4][5]
Capacity loss is C-rate sensitive and higher C-rates lead to a faster capacity loss on a per cycle. Chemical mechanisms of degradation in a Li-ion battery dominate capacity loss at low C-rates, whereas, mechanical degradation dominates at high C-rates.[6][7]
Graphite/LiCoO2 battery capacity degradation is reported to be affected by mean SOC as well as the change in SOC (ΔSOC) during the cycling operation. For the first 500 equivalent full cycles mean SOC is found to have a major effect on the capacity fade of cells as compared to ΔSOC. However, towards the end of the testing (600~800 equivalent cycles) ΔSOC becomes the major factor affecting the capacity loss rate of the cells.[8]
See also
[edit]- Recovery effect
- Nickel-iron battery, a battery that is highly resistant to capacity loss
- Memory effect
References
[edit]- ^ Xia, Y. (1997). "Capacity Fading on Cycling of 4 V Li/LiMn2O4 Cells". Journal of the Electrochemical Society. 144 (8): 2593–2600. Bibcode:1997JElS..144.2593X. doi:10.1149/1.1837870.
- ^ Amatucci, G. (1996). "Cobalt dissolution in LiCoO2-based non-aqueous rechargeable batteries". Solid State Ionics. 83 (1–2): 167–173. doi:10.1016/0167-2738(95)00231-6.
- ^ Spotnitz, R. (2003). "Simulation of capacity fade in lithium-ion batteries". Journal of Power Sources. 113 (1): 72–80. Bibcode:2003JPS...113...72S. doi:10.1016/S0378-7753(02)00490-1.
- ^ Waldmann, Thomas (September 2014). "Temperature dependent ageing mechanisms in Lithium-ion batteries – A Post-Mortem study". Journal of Power Sources. 262: 129–135. Bibcode:2014JPS...262..129W. doi:10.1016/j.jpowsour.2014.03.112.
- ^ W. Diao, Y. Xing, S. Saxena, and M. Pecht (2018). "Evaluation of Present Accelerated Temperature Testing and Modeling of Batteries". Applied Sciences. 8 (10): 1786. doi:10.3390/app8101786.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ C. Snyder (2016). "The Effects of charge/discharge Rate on Capacity Fade of Lithium Ion Batteries". Bibcode:2016PhDT.......260S.
{{cite journal}}: Cite journal requires|journal=(help) - ^ S. Saxena, Y. Xing, D. Kwon, and M. Pecht (2019). "Accelerated degradation model for C-rate loading of lithium-ion batteries". International Journal of Electrical Power & Energy Systems. 107: 438–445. Bibcode:2019IJEPE.107..438S. doi:10.1016/j.ijepes.2018.12.016. S2CID 115690338.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ S. Saxena, C. Hendricks, and M. Pecht (September 2016). "Cycle life testing and modeling of graphite/LiCoO2 cells under different state of charge ranges". Journal of Power Sources. 327: 394–400. Bibcode:2016JPS...327..394S. doi:10.1016/j.jpowsour.2016.07.057.
{{cite journal}}: CS1 maint: multiple names: authors list (link)
Capacity loss
View on GrokipediaFundamentals
Definition
Capacity loss, also known as capacity fading, refers to the progressive and often irreversible reduction in the amount of charge a rechargeable battery can store and deliver at its rated voltage over time or through repeated charge-discharge cycles.[4] This decline arises from various degradation processes that diminish the battery's active material availability or lithium-ion transport efficiency, leading to a shorter runtime for a given load.[5] The nominal capacity of a battery, denoted as , is fundamentally defined by the relation , where is the discharge current and is the discharge time; capacity loss manifests as a consistent decrease in this value with aging or cycling.[6] Capacity loss is distinct from related degradation phenomena such as efficiency loss or power fade. Efficiency loss typically involves a drop in coulombic efficiency, reflecting the mismatch between charge input and output due to side reactions, whereas power fade stems from increased internal resistance that limits the battery's ability to deliver high currents or rates.[7] In contrast, capacity loss focuses exclusively on the erosion of the battery's total deliverable charge storage, independent of rate or round-trip energy recovery.[8] The phenomenon was first prominently observed in nickel-cadmium batteries during the 1970s, where capacity reductions were frequently misattributed to a "memory effect" from incomplete discharges, though true fading involved electrode degradation and electrolyte issues.[9] Since the commercialization of lithium-ion batteries in the early 1990s, capacity loss has become a central focus of research, driven by the need to extend cycle life for applications like electric vehicles and portable electronics, with studies emphasizing solid-electrolyte interphase growth as a primary culprit.[10]Measurement and Quantification
Capacity loss in batteries is primarily assessed through standardized cycling protocols that involve repeated full charge and discharge operations. The most common technique is the constant current (CC) charge-discharge cycling test, where the battery is charged to its full capacity and then discharged at a fixed current rate, such as 1C (equivalent to the current that fully discharges the battery in one hour), while monitoring the delivered discharge capacity over successive cycles. This method allows for direct tracking of capacity fade by comparing the discharge capacity at each cycle against the initial value, providing a reliable baseline for evaluating degradation in lithium-ion and other rechargeable systems.[11][12] Key metrics derived from these tests quantify the extent of capacity loss in a standardized manner. The capacity retention ratio (CR) is calculated aswhere is the discharge capacity at cycle and is the initial discharge capacity; this ratio expresses the percentage of original capacity remaining after cycling. Cycle life is typically defined as the number of full cycles until CR drops to 80%, marking a common threshold for end-of-life in practical applications. For lithium-ion batteries, empirical data from early comprehensive reviews indicate typical loss rates of 0.025–0.048% per cycle after 500 cycles, corresponding to overall losses of 12.4–24.1% at that point, with end-of-life often reached at approximately 20% total capacity loss (80% retention).[13][14][4] For more nuanced evaluation, advanced techniques like electrochemical impedance spectroscopy (EIS) enable differentiation between reversible and irreversible capacity loss components. EIS applies a small alternating current perturbation across a range of frequencies to measure the battery's impedance spectrum, revealing contributions from processes such as solid electrolyte interphase (SEI) growth (associated with irreversible lithium loss) versus reversible charge transfer or diffusion limitations. This separation aids in isolating permanent degradation from recoverable effects, enhancing predictive models for battery health without relying solely on cycling data.[15][16]
