Polyimide binder by combining with polyimide separator for enhancing the electrochemical performance of lithium ion batteries

摘要

Lithium ion battery (LIB) has been assembled by a polyimide (PI) binder, which is prepared by one-pot solution polycondensation, and PI non-woven separator. Compared to the cell using the traditional PVDF binder and polyethylene (PE) separator, the cell with PI binder and PI separator (PI-PI) not only has a better thermal stability but also displays significantly improved electrochemical performance, especially rate performance and cycling behavior. The thermogravimetric analysis (TGA) shows that the temperature of the weight loss of 10% of PVDF and PI is 464.6 degrees C and 525.9 degrees C, respectively. The properties of the separator, including wettability, electrolyte uptake and mechanical performance are tested. Owing to the hydrophilic imide group and the rigid aromatic nucleus. These properties make a possibility of a battery to meet higher requirements. In the terms of electrochemistry, when the current density over 1C, the cell with PVDF binder and PE separator (PVDF-PE) only retains no more than 61% of its capacity at a rate of 0.05C. However the cell that based on PI-PI still maintains 72.6%. Besides, the cycle performance of PI-PI gains a significant improvement. It can stay over 85% capacitance retention ratio after 200 cycles at a rate of 1C, while the PVDF-PE is only 57.68%. The outstanding improvement of the rate capability is due to the reduction of internal resistance of the battery. (C) 2016 Elsevier Ltd. All rights reserved.