Fibrous gel polymer electrolyte for an ultrastable and highly safe flexible lithium-ion battery in a wide temperature range

Replacement of flammable liquid electrolytes with gel polymer electrolytes（GPEs） is a promising route to improve the safety of lithium-ion batteries（LIBs）.However, polymer-based electrolytes have limited suitability at low/high temperatures due to the instability of the polymer at high temperatures and the low ionic conductivity of the gel state at low temperatures. Herein, an integrated design of electrodes/fibrous GPEs modified with graphene oxide（GO） is reported. Due to the integrated structure of electrodes/GPEs, the strong interface affinity between electrodes and GPEs ensures that the GPEs spun on electrodes do not shrink at high temperatures（160–180°C）, thus preventing a short circuit of electrodes. Moreover, after GO modification, oxygen-containing functional groups of GO can accelerate Li+ transport of GO-GPEs even at a low temperature of-15°C. When these GPEs are applied to flexible LIBs, the LIBs show excellent electrochemical performance, with satisfactory cycling stability of82.9% at 1 C after 1000 cycles at 25°C. More importantly, at a high temperature of 160°C, the LIBs can also discharge normally and light the green light-emitting diode. Furthermore, at a low temperature of-15°C, 92.7% of its roomtemperature capacity can be obtained due to the accelerated Li+transport caused by GO modification, demonstrating the great potential of this electrolyte and integrated structure for practical gel polymer LIB applications.