Thermal study on single electrodes in lithium-ion battery

The thermodynamic parameters: ΔG, ΔS and ΔH of LixC6/1 M LiPF6/Li1−xCoO2 battery reaction were measured by potentiometric method. The ΔS and reversible Peltier heat qr of cathode and anode reactions in lithium-ion battery were calculated from the ΔS of Li/1 M LiPF6/Li1−xCoO2 and Li/1 M LiPF6/LixC6 cell reactions, and the ΔS of Li electrode reaction, respectively. For Li electrode reaction, the ΔS and qr were detected by both potentiometric and electrochemical-calorimetric methods. For a fully charged LixC6/1 M LiPF6/Li1−xCoO2 battery during reversible discharge process, the overall reaction Li1−xCoO2 + LixC6 → LiCoO2 + 6C presents exothermal heat effect with ΔS of −29.78 J K−1 mol−1 and qr of 8.874 kJ mol−1. Furthermore, the cathode reaction xLi+ + xe− + Li1−xCoO2 → LiCoO2 shows larger exothermic effect with ΔS of −121.8 J K−1 mol−1 and qr of 36.30 kJ mol−1, and the anode reaction LixC6 → xLi+ + xe− + 6C shows smaller endothermic effect with ΔS of 92.08 J K−1 mol−1 and qr of −27.46 kJ mol−1. The heat produced at the positive electrode reaction is about three times more than that of overall battery reaction.