The thermodynamic parameters: ΔG, ΔS and ΔH of Li x C6/1M LiPF6/Li1−x CoO2 battery reaction were measured by potentiometric method. The ΔS and reversible Peltier heat q r of cathode and anode reactions in lithium-ion battery were calculated from the ΔS of Li/1M LiPF6/Li1−x CoO2 and Li/1M LiPF6/Li x C6 cell reactions, and the ΔS of Li electrode reaction, respectively. For Li electrode reaction, the ΔS and q r were detected by both potentiometric and electrochemical-calorimetric methods. For a fully charged Li x C6/1M LiPF6/Li1−x CoO2 battery during reversible discharge process, the overall reaction Li1−x CoO2 +Li x C6 →LiCoO2 +6C presents exothermal heat effect with ΔS of −29.78JK−1 mol−1 and q r of 8.874kJmol−1. Furthermore, the cathode reaction xLi+ + xe− +Li1−x CoO2 →LiCoO2 shows larger exothermic effect with ΔS of −121.8JK−1 mol−1 and q r of 36.30kJmol−1, and the anode reaction Li x C6 → xLi+ + xe− +6C shows smaller endothermic effect with ΔS of 92.08JK−1 mol−1 and q r of −27.46kJmol−1. The heat produced at the positive electrode reaction is about three times more than that of overall battery reaction.