Poly(3-butylthiophene)-based positive-temperature-coefficient electrodes for safer lithium-ion batteries

A new positive temperature coefficient (PTC) electrode is prepared simply by coating a thin layer of redox-active poly (3-butylthiophene) (P3BT) in between the electroactive Li[Ni0.5Co0.2Mn0.3]O2 [523] layer and the Al foil substrate to improve the safety of lithium-ion batteries. The experimental results demonstrate that the electrical conductivity of the PF6−-doped P3BT decreases sharply at 120–150 °C, showing a remarkable PTC effect. As for the P3BT-523 composite electrodes, a rate capacity nearly reaching the reference electrode is obtained at less than 1C rate, while the rate discharge capacities increase obviously with the decrease of the P3BT solution concentration. Moreover, after being exposed to 150 °C for 5 min, the P3BT-523 composite electrodes are hardly discharged and the discharge voltage of the composite electrodes drop drastically below the cut-off voltage at a current density of 3 C, suggesting an effective thermal shutdown switch for lithium-ion batteries.