Thermal studies of a lithium-ion battery

Thermo-Chemical Process Associated with Lithium Cobalt Oxide Cathode in Lithium Ion Batteries

“…As the x in Li x CoO 2 shifts from 0.45 to 0.3, a large anisotropic volume change of 3% occurs due to the phase transition between hexagonal and monoclinic H1-3 phases (Jang et al, 2002& Amatucci et al, 1996. Such crystal-phase change is also presumed to induce thermal stability of the positive electrode (Saito et al, 1997). Fig.…”

“…When the electrode mass is larger than the mass of the solvent, the solvent becomes insufficient to reduce fully the higher valent cobalt to Co metal. The temperature dependency of the heat generation between 283 and 333 K (Saito et al, 1997) shows an exothermic peak and an endothermic peak at around 4V caused by a phase transition of the positive electrode material Li x CoO 2 between the hexagonal and monoclinic structures observed at around x = 0.5. At the point of phase change cathode also faces instability.…”

“…Voltage and thermal behaviour of Cell-1 on overcharge at 1 C rate, (Doh et al, 2008) As the cathode is completely de-lithiated, the cell voltage moves above 4.5V, the ionic conduction completely ceases, and the passage of current through the cell becomes purely ohmic resulting in heat generation due to I 2 R loss. The poor heat dissipation of the cell components causes an exponential increase in cell temperature (Saito et al, 1997)), which induces decomposition of Li x CoO 2 according to equation. (1).…”

“…This proton interacts with LiF deposit present in the SEI film and forms H 2 F 2 . The acidic species HF 2¯ formed from H 2 F 2 then reacts with Li 2 CO 3 present in SEI film making it more fragile (Lorey et al, Doh et al, 2008& Saito et al, 1997. The reactions are presented as equation (2) and (3).…”

Degradation Reactions in SONY-Type Li-Ion Batteries

“…The range of stability of the Li,CoO2 crystal structure limits the charged state of the cathode to about x=0.5, giving a nominal composition of Lio.sC002 for the fully charged cathode [3,4]. The potential of the fully charged cathode referenced to Li/Li' is 4.1 V while that in the discharged state ( Lil.oCoO2) is 3.0 V. The corresponding potential of the fully charged anode (Lil.oC6) is 0.0 V and 3.0 V in the discharge state (Lio.oC6).…”