Quasi-solid-state potassium-ion batteries (QSPIBs) are regarded as one of the most promising safety-enhanced energy storage devices. Herein, a facile method for preparing a potassium-ion composite electrolyte membrane on a large scale is presented for the first time. The as-synthesized membrane displays excellent electrochemical stability, good mechanical flexibility, and high ionic conductivity (9.31 x 10(-5) S cm(-1) at 25 degrees C). Furthermore, QSPIBs prepared with this membrane and commercial raw material-based electrodes show superior electrochemical performance even at low temperatures (99.7 mAh g(-1) at -20 degrees C for half QSPIBs and 90.7 mAh g(-1) at-15 degrees C for full QSPIBs), and a promising rate performance (115.6 mAh g(-1) for half QSPIBs and 90.9 mAh g(-1) for full QSPIBs at 800 mA g(-1)). The reaction mechanism and structure evolution of a 3,4,9,10-perylene-tetracarboxylicacid-dianhydride (PTCDA) cathode is also systematically studied. The promising characteristics of the prepared low-cost quasi-solid-state potassium-ion batteries in this work open up new possibilities for safer and more durable batteries and a wide range of practical applications in the electronics industry. (C) 2020 Elsevier Inc. All rights reserved.