Solid polymer electrolytes provide high safety and good electrochemical stability in solid-state lithium batteries (SELBs) compared with conventional liquid electrolytes. In this work, a novel solid polymer composite electrolyte based on poly (ethylene oxide) (PEO) filled with rod-like Zn-2(OH)BO3 particles was prepared by a grinding process followed with a heating treatment process and a cold pressing process. The effect of the incorporation amount of rod-like Zn-2(OH)BO3 particles on the ionic conductivity was investigated systemically. It is found that 10 mol% of rod-like Zn-2(OH)BO3 particles addition resulted in a highest ionic conductivity of 2.78 x 10(-5) at 30 degrees C and the improved ionic conductivity was considered to be caused by the reducing of PEO crystallinity and the increasing of Li ion migrating pathway on the interface between the Zn-2(OH)BO3 and PEO. In addition, the optimum composite electrolyte exhibited a high electrochemical stability window of 4.51 V (vs. Li/Li+), good lithium stability and excellent thermal stability. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.