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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) http://www.fer.hr/_download/repository/Li-ION.pdf 1 © Alexis Kwasinski, 2012 Li-ion batteries • Chemical reaction (discharge) • Positive electrode Li1-xCoO2 + xLi+ + xe- LiCoO2 Through electrolyte • Negative electrode •Overall xLi+ + xe- + 6C LiCoO2 + C6 LixC6 Through load Li1-xCoO2 + C6Lx • 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. 2 © Alexis Kwasinski, 2012 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 constantcurrent profile. Hence they need a charger • Typical float voltage is above 4 V (typically 4.2 V). Saft Intensium 3 Li-ion battery 3 “Advanced Lithium Ion Battery Charger” V.L. Teofilo, L.V. Merritt and R.P. Hollandsworth © Alexis Kwasinski, 2012 Li-ion batteries • Effects of temperature: http://www.gpbatteries.com/html/pdf/Li-ion_handbook.pdf 4 © Alexis Kwasinski, 2012 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 Saft Intensium 3 Li-ion battery 5 “Advanced Lithium Ion Battery Charger” V.L. Teofilo, L.V. Merritt and R.P. Hollandsworth © Alexis Kwasinski, 2012 Li-ion batteries • Factors affecting life: • Charging voltage. • Temperature • Age (time since manufacturing) • Degradation process: oxidation 6 © Alexis Kwasinski, 2012 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 7 © Alexis Kwasinski, 2012 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 8 © Alexis Kwasinski, 2012 Ni-MH batteries • Chemical reaction (discharge) • Positive electrode NiO(OH) + H2O + e- Ni(OH)2 + OHThrough electrolyte •Negative electrode •Overall MH + OH- NiO(OH) + MH Through load M + H2O + e- Ni(OH)2 + M • The electrolyte is not affected because it does not participate in the reaction. 9 © Alexis Kwasinski, 2012 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 10 © Alexis Kwasinski, 2012 Ni-MH batteries • Effects of temperature: Saft NHE module battery http://www.panasonic.com/industrial/battery/oem/images/pdf /panasonic_nimh_overview.pdf 11 © Alexis Kwasinski, 2012 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 12 © Alexis Kwasinski, 2012 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 13 © Alexis Kwasinski, 2012 Ni-Cd batteries • Chemical reaction (discharge) • Positive electrode 2NiO(OH) + 2H2O + 2e- 2Ni(OH)2 + 2OHThrough electrolyte • Negative electrode •Overall Cd + 2OH- 2NiO(OH) + Cd + 2H2O Through load Cd(OH)2 + 2e- 2Ni(OH)2 + Cd(OH)2 • The electrolyte is not affected because it does not participate in the reaction. 14 © Alexis Kwasinski, 2012 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 15 http://www.saftbatteries.com/doc/Documents/telecom/Cube788/tel _tm_en_0704.26962445-6b1b-44fb-aea7-42834c32be40.pdf © Alexis Kwasinski, 2012 Ni-Cd batteries • Effects of temperature: http://www.saftbatteries.com/doc/Documents/telecom/Cube788/tel _tm_en_0704.26962445-6b1b-44fb-aea7-42834c32be40.pdf 16 © Alexis Kwasinski, 2012 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) 17 © Alexis Kwasinski, 2012 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 18 © Alexis Kwasinski, 2012 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 19 © Alexis Kwasinski, 2012 Battery technologies Cobasys: “Inside the Nickel Metal Hydride Battery” 20 © Alexis Kwasinski, 2012