Li-ion batteries

1. Li-ion batteries • Positive electrode: Lithiated form of a transition metal oxide (lithium cobalt oxide-LiCoO2 or lithium manganese oxide LiMn2O4) • Negative electrode: Carbon (C), • usually graphite (C6) • Electrolyte: solid lithium-salt electrolytes • (LiPF6, LiBF4, or LiClO4) • and organic solvents (ether) discharge http://www.fer.hr/_download/repository/Li-ION.pdf

2. Li-ion batteries • Chemical reaction (discharge) • Positive electrode • Negative electrode • Overall • In the above reaction x can be 1 or 0 • With discharge the Co is oxidized from Co3+ to Co4+. The reverse process (reduction) occurs when the battery is being charged. LiCoO2 Li1-xCoO2+ xLi+ + xe- Through electrolyte Through load xLi+ + xe- + 6C LixC6 LiCoO2 + C6 Li1-xCoO2+ C6Lx

3. Li-ion batteries • Contrary to lead-acid batteries, Li-ion batteries do not accept well a high initial charging current. • In addition, cells in a battery stack needs to be equalized to avoid falling below the minimum cell voltage of about 2.85 V/cell. • Thus, Li-ion batteries need to be charged at least initially with a constant-current profile. Hence they need a charger • Typical float voltage is above 4 V • (typically 4.2 V). “Advanced Lithium Ion Battery Charger” V.L. Teofilo, L.V. Merritt and R.P. Hollandsworth Saft Intensium 3 Li-ion battery

4. Li-ion batteries • Effects of temperature: http://www.gpbatteries.com/html/pdf/Li-ion_handbook.pdf

5. Li-ion batteries • Controlled charging has 2 purposes: • Limiting the current • Equalizing cells “Increased Performance of Battery Packs by Active Equalization” Jonathan W. Kimball, Brian T. Kuhn and Philip T. Krein “Advanced Lithium Ion Battery Charger” V.L. Teofilo, L.V. Merritt and R.P. Hollandsworth Saft Intensium 3 Li-ion battery

6. Li-ion batteries • Factors affecting life: • Charging voltage. • Temperature • Age (time since manufacturing) • Degradation process: oxidation

7. Li-ion batteries • Advantages with respect to lead-acid batteries: • Less sensitive to high temperatures (specially with solid electrolytes) • Lighter (compare Li and C with Pb) • They do not have deposits every charge/discharge cycle (that’s why the efficiency is 99%) • Less cells in series are need to achieve some given voltage. • Disadvantages: • Cost

8. Ni-MH batteries • Negative electrode: Metal Hydride such as AB2 (A=titanium and/or vanadium, B= zirconium or nickel, modified with chromium, cobalt, iron, and/or manganese) or AB5 (A=rare earth mixture of lanthanum, cerium, neodymium, praseodymium, B=nickel, cobalt, manganese, and/or aluminum) • Positive electrode: nickel oxyhydroxide (NiO(OH)) • Electrolyte: Potassium hydroxide (KOH) Cobasys batteries

9. Ni-MH batteries • Chemical reaction (discharge) • Positive electrode • Negative electrode • Overall • The electrolyte is not affected because it does not participate in the reaction. NiO(OH) + H2O + e- Ni(OH)2+ OH- Through electrolyte Through load MH + OH- M + H2O + e- NiO(OH) + MH Ni(OH)2+ M

10. Ni-MH batteries • It is not advisable to charge Ni-MH batteries with a constant-voltage method. Ni-MH batteries do not accept well a high initial charging current. • Float voltage is about 1.4 V • Minimum voltage is about 1 V. Cobasys Nigen battery Saft NHE module battery

11. Ni-MH batteries • Effects of temperature: Saft NHE module battery http://www.panasonic.com/industrial/battery/oem/images/pdf/panasonic_nimh_overview.pdf

12. Ni-MH batteries • Advantages: • Less sensitive to high temperatures than Li-ion and Lead-acid • Handle abuse (overcharge or over-discharge better than Li-ion bat • Disadvantages: • More cells in series are need to achieve some given voltage. • Cost

13. Ni-Cd batteries • Negative electrode: Cadmium (Cd) – instead of the MH in Ni-MH batteries • Positive electrode: nickel oxyhydroxide (NiO(OH)) – the same than in Ni-MH • batteries • Electrolyte: Potassium hydroxide • (KOH) solution Saft batteries

14. Ni-Cd batteries • Chemical reaction (discharge) • Positive electrode • Negative electrode • Overall • The electrolyte is not affected because it does not participate in the reaction. 2NiO(OH) + 2H2O + 2e- 2Ni(OH)2+ 2OH- Through electrolyte Through load Cd + 2OH- Cd(OH)2 + 2e- 2NiO(OH) + Cd + 2H2O 2Ni(OH)2+ Cd(OH)2

15. Ni-Cd batteries • It is not advisable to charge Ni-Cd batteries with a constant-voltage method. Ni-Cd batteries do not accept well a high initial charging current, but they can withstand it sporadically. • Float voltage is about 1.4 V • Minimum voltage is about 1 V. Saft Ultima plus http://www.saftbatteries.com/doc/Documents/telecom/Cube788/tel_tm_en_0704.26962445-6b1b-44fb-aea7-42834c32be40.pdf

16. Ni-Cd batteries • Effects of temperature: http://www.saftbatteries.com/doc/Documents/telecom/Cube788/tel_tm_en_0704.26962445-6b1b-44fb-aea7-42834c32be40.pdf

17. Ni-Cd batteries • Due to their better performance at high temperatures, Ni-Cd batteries are replacing Lead-acid batteries in outdoor stationary applications. But, they do not resist hurricanes very well, yet……(AT&T’s DLC at Sabine Pass CO, Saft NCX batteries)

18. Ni-Cd batteries • Advantages: • Less sensitive to high temperatures than all the other batteries • Handle some abuse (overcharge or over-discharge better than Li-ion bat) • Disadvantages: • More cells in series are need to achieve some given voltage. • Cost

19. Ni-Cd batteries • Comparison with Ni-MH batteries (not much of a difference) Portable NiCd- and Ni-MH-Batteries for Teiecom Applications J. Heydecke and H.A. Kiehne

20. Battery technologies Cobasys: “Inside the Nickel Metal Hydride Battery”