A Strategy for Preparing Solid Polymer Electrolytes Containing In Situ Synthesized ZnO Nanoparticles with Excellent Electrochemical Performance

ZnO nanoparticles were successfully in situ synthesized in the form of PEO–COO(−) modified ZnO by a three-step method, based on which the solid polymer electrolytes (SPEs), based on polyethylene oxide (PEO) with excellent electrochemical performance, were prepared. The evolution of the electrochemical and mechanical performances of the SPEs with the ZnO content (0–5 wt.%) was investigated in detail. The mechanical property of the SPEs demonstrated a Λ-shaped change trend as increasing the ZnO content, so that the highest value was acquired at 3 wt.% ZnO. The SPE containing 3 wt.% ZnO had the most outstanding electrochemical performance, which was significantly better than that containing directly-added ZnO (2 wt.%). Compared with the latter, the ion conductivity of the former was improved by approximately 299.05% (1.255 × 10(−3) S·cm(−1) at 60 °C). The lithium-ion migration number was improved from 0.768 to 0.858. The electrochemical window was enhanced from 5.25 V to 5.50 V. When the coin cell was subject to the cycling (three cycles in turn from 0.1 C to 3 C, and subsequent fifty cycles at 1 C), the 68.73% specific capacity was retained (106.8 mAh·g(−1)). This investigation provides a feasible approach to prepare the SPEs with excellent service performance.