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The development of safe and long-term stable solid polymer electrolytes is a major challenge for all solid-state batteries because good interfacial stability toward electrodes is the main concern. In this paper, a triblock copolymer polystyrene-poly(ethylene glycol)-polystyrene (PS-PEG-PS) is synthesized and investigated as solid polymer electrolyte. This polymer electrolyte exhibits a high ionic conductivity of 1.1 × 10−3 S cm −1 at 70 °C, transference number of 0.17, high degree flexibility, good mechanical strength and thermal stability. The interface stability of the solid-polymer electrolyte is investigated in Li metal cell and the comprehensive electrochemical properties are studied in cells with either LiFePO4 or LiNi0.5Co0.3Mn0.2O2 cathode materials. Good rate capability and excellent cyclability of the solid polymer electrolyte is demonstrated, with an electrochemical stability window extending above 4.5 V vs. Li+/Li. Furthermore, constant voltage impedance measurements give evidence of the better interface stability and rate capability of LiNi0.5Co0.3Mn0.2O2//Li battery. Meanwhile, molecular orbital energy levels calculated by density functional theory are consistent with experiments.

Nano-crystallized LiFePO4 has been synthesized with a simple three-step-synthesis technology in the presence of nano-ferric oxide as iron source and polyacence (PAS) as a reductive agent and high conductive carbon source. The use of PAS increases the conductivity and prevents the particles growth. The most feasible calcined temperature and time was investigated and the best cell performance was delivered by the sample calcined at 700 °C for 4 h. This material shows excellent specific capacity and cycle efficiency at high current rates, almost no capacity loss can be observed up to 100 cycles which make it more superior as an optimum power cell cathode material.