Capacity loss

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Capacity 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]

Contents

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

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, the aging rates increase with decreasing temperature below 25 °C, while above 25 °C aging is accelerated with increasing temperature. [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

Related Research Articles

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The lithium iron phosphate battery or LFP battery is a type of lithium-ion battery using lithium iron phosphate as the cathode material, and a graphitic carbon electrode with a metallic backing as the anode. The energy density of an LFP battery is lower than that of other common lithium ion battery types such as Nickel Manganese Cobalt (NMC) and Nickel Cobalt Aluminum (NCA), and also has a lower operating voltage; CATL's LFP batteries are currently at 125 watt hours (Wh) per kg, up to possibly 160 Wh/kg with improved packing technology, while BYD's LFP batteries are at 150 Wh/kg, compared to over 300 Wh/kg for the highest NMC batteries. Notably, the energy density of Panasonic’s “2170” NCA batteries used in 2020 in Tesla’s Model 3 is around 260 Wh/kg, which is 70% of its "pure chemicals" value.

State of charge

State of charge (SoC) is the level of charge of an electric battery relative to its capacity. The units of SoC are percentage points. An alternative form of the same measure is the depth of discharge (DoD), the inverse of SoC. SoC is normally used when discussing the current state of a battery in use, while DoD is most often seen when discussing the lifetime of the battery after repeated use.

Lithium iron phosphate Chemical compound

Lithium iron phosphate (LFP) is an inorganic compound with the formula LiFePO
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Depth of discharge (DoD) is an important parameter appearing in the context of rechargeable battery operation. Two non-identical definitions can be found in commercial and scientific sources. The depth of discharge is defined as:

  1. the maximum fraction or percentage of a battery's capacity which is removed from the charged battery on a regular basis. "Charged" does not necessarily refer to fully or 100 % charged, but rather to the state of charge (SoC), where the battery charger stops charging, which is achieved by different techniques.
  2. the fraction or percentage of the battery's capacity which is currently removed from the battery with regard to its (fully) charged state. For fully charged batteries, the depth of discharge is connected to the state of charge by the simple formula . The depth of discharge then is the complement of state of charge: as one increases, the other decreases. This definition is mostly found in scientific sources.
Lithium–sulfur battery

The lithium–sulfur battery is a type of rechargeable battery. It is notable for its high specific energy. The low atomic weight of lithium and moderate atomic weight of sulfur means that Li–S batteries are relatively light. They were used on the longest and highest-altitude unmanned solar-powered aeroplane flight by Zephyr 6 in August 2008.

Thin-film lithium-ion battery Type of battery

The thin film lithium-ion battery is a form of solid-state battery. Its development is motivated by the prospect of combining the advantages of solid-state batteries with the advantages of thin-film manufacturing processes.

The lithium–air battery (Li–air) is a metal–air electrochemical cell or battery chemistry that uses oxidation of lithium at the anode and reduction of oxygen at the cathode to induce a current flow.

A metal–air electrochemical cell is an electrochemical cell that uses an anode made from pure metal and an external cathode of ambient air, typically with an aqueous or aprotic electrolyte.

Separator (electricity)

A separator is a permeable membrane placed between a battery's anode and cathode. The main function of a separator is to keep the two electrodes apart to prevent electrical short circuits while also allowing the transport of ionic charge carriers that are needed to close the circuit during the passage of current in an electrochemical cell.

A lithium ion manganese oxide battery (LMO) is a lithium-ion cell that uses manganese dioxide, MnO
2, as the cathode material. They function through the same intercalation/de-intercalation mechanism as other commercialized secondary battery technologies, such as LiCoO
2. Cathodes based on manganese-oxide components are earth-abundant, inexpensive, non-toxic, and provide better thermal stability.

Research in lithium-ion batteries has produced many proposed refinements of lithium-ion batteries. Areas of research interest have focused on improving energy density, safety, rate capability, cycle durability, flexibility, and cost.

Lithium hybrid organic batteries are an energy storage device that combines lithium with an organic polymer. For example, polyaniline vanadium (V) oxide (PAni/V2O5) can be incorporated into the nitroxide-polymer lithium iron phosphate battery, PTMA/LiFePO4. Together, they improve the lithium ion intercalation capacity, cycle life, electrochemical performances, and conductivity of batteries.

Lithium–silicon battery is a name used for a subclass of lithium-ion battery technology that employs a silicon-based anode and lithium ions as the charge carriers. Silicon based materials generally have a much larger specific capacity, for example 3600 mAh/g for pristine silicon, relative to graphite, which is limited to a maximum theoretical capacity of 372 mAh/g for the fully lithiated state LiC6. Silicon's large volume change (approximately 400% based on crystallographic densities) when lithium is inserted is one of the main obstacles along with high reactivity in the charged state to commercializing this type of anode. Commercial battery anodes may have small amounts of silicon, boosting their performance slightly. The amounts are closely held trade secrets, limited as of 2018 to at most 10% of the anode. Lithium-silicon batteries also include cell configurations where Si is in compounds that may at low voltage store lithium by a displacement reaction, including silicon oxycarbide, silicon monoxide or silicon nitride.

Lithium nickel manganese cobalt oxides (abbreviated Li-NMC, LNMC, NMC or NCM) are mixed metal oxides of lithium, nickel, manganese and cobalt. They have the general formula LiNixMnyCozO2. The most important representatives have a composition with x + y + z that is near 1, with a small amount of lithium on the transition metal site. In commercial NMC samples, the composition typically has < 5% excess lithium. Structurally materials in this group are closely related to lithium cobalt(III) oxide (LiCoO2) and have a layered structure but possess an ideal charge distribution of Mn(IV), Co(III), and Ni(II) at the 1:1:1 stoichiometry. For more nickel-rich compositions, the nickel is in a more oxidized state for charge balance. NMCs are among the most important storage materials for lithium ions in lithium ion batteries. They are used on the positive side, which acts as the cathode during discharge.

Solid-state electrolyte

A solid-state electrolyte (SSE) is a solid ionic conductor and electron-insulating material and it is the characteristic component of the solid-state battery. It is useful for applications in electrical energy storage (EES) in substitution of the liquid electrolytes found in particular in lithium-ion battery. The main advantages are the absolute safety, no issues of leakages of toxic organic solvents, low flammability, non-volatility, mechanical and thermal stability, easy processability, low self-discharge, higher achievable power density and cyclability. This makes possible, for example, the use of a lithium metal anode in a practical device, without the intrinsic limitations of a liquid electrolyte thanks to the property of lithium dendrite suppression in the presence of a solid-state electrolyte membrane. The utilization of a high capacity anode and low reduction potential, like lithium with a specific capacity of 3860 mAh g−1 and a reduction potential of -3.04 V vs SHE, in substitution of the traditional low capacity graphite, which exhibits a theoretical capacity of 372 mAh g−1 in its fully lithiated state of LiC6, is the first step in the realization of a lighter, thinner and cheaper rechargeable battery. Moreover this allows the reach of gravimetric and volumetric energy densities, high enough to achieve 500 miles per single charge in an electric vehicle. Despite the promising advantages, there are still many limitations that are hindering the transition of SSEs from academia research to large-scale production, depending mainly on the poor ionic conductivity compared to that of liquid counterparts. However, many car OEMs (Toyota, BMW, Honda, Hyundai) expect to integrate these systems into viable devices and to commercialize solid-state battery-based electric vehicles by 2025.

References

  1. ↑ Xia, Y. (1997). "Capacity Fading on Cycling of 4 V Li/LiMn2O4 Cells". Journal of the Electrochemical Society. 144 (8): 2593–2600. doi:10.1149/1.1837870.
  2. ↑ 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.
  3. ↑ 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.
  4. ↑ 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.
  5. ↑ 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)
  6. ↑ 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)
  7. ↑ 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. doi:10.1016/j.ijepes.2018.12.016. S2CID   115690338.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  8. ↑ 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)


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