A rational design of solid polymer electrolyte with high salt concentration for lithium battery

With the development of electrical energy storage and electrical vehicle, high safety is indispensable for lithium ion battery, therefore, high performance solid polymer electrolytes are the relentless pursuit of numerous researches. However, low ionic conductivity restricts the polymer electrolyte usage in commercialized lithium ion batteries. Among the candidates of polymer electrolytes, poly (ethylene carbonate) is promising due to its ability of high lithium salt dissociation. Nonetheless, these polymer electrolytes with high concentration salt always accompanies with an obvious deterioration of mechanical properties. Herein, via controlling the ratio of poly (ethylene carbonate) and poly (vinylidene fluoride-co-hexafluoropropene), a biphasic solid polymer electrolyte possessing high concentration lithium salt phase and good mechanical strength is prepared. Specifically, considering the role of polymer groups in lithium ion transport, it is speculated that dual-path of Li⁺ transport forms in the polymer electrolyte, which improves the conductivity remarkably. The prepared electrolyte realizes sufficient ionic conductivity (1.08 × 10⁻⁴ S/cm) at 30 °C, with a wide electrochemical window about 4.5 V (vs. Li⁺/Li), meanwhile exhibits the capacity of `suppression to lithium dendrite growth. Notably, with the polymer electrolyte, Li/LiFePO₄ cell exhibits superior rate capacity and excellent cycling stability. This study proves new insights for polymer electrolyte design with high conductivity.