高锂盐含量聚氨酯基固态电解质的制备与性能

Preparation and Properties of Solid Electrolytes Based on Polyurethane with High Lithium Salt Content

以异佛尔酮二异氰酸酯、聚碳酸酯二元醇和一缩二乙二醇为原料,合成硬段质量分数为30%的聚碳酸酯型聚氨酯(PCPU),将合成的聚氨酯和双三氟甲烷磺酰亚胺锂(LiTFSI)复合制得不同锂盐质量分数的固态聚合物电解质(SPE)。通过红外光谱分析了聚氨酯结构,采用TG、DSC测试了聚氨酯及电解质的热学性能,并采用交流阻抗、线性扫描伏安测试探究了不同LiTFSI质量分数对电解质电化学性能的影响。结果表明,随着LiTFSI质量分数的增加,聚氨酯基固态聚合物电解质的室温离子电导率呈现先增大后减小再增大的趋势,当锂盐质量分数为70%时,制备的电解质离子电导率达到最大值(1.28×10^(–8)S/cm),以此固态电解质与LiFePO4正极组装的固态电池在60℃、0.2 C电流密度时放电比容量为153 mA·h/g,循环100次容量保持率为84%。

Polycarbonate polyurethane(PCPU) with 30% mass fraction of hard segment was synthesized from isophorone diisocyanate, polycarbonate diol and diethylene glycol. The synthesized PCPU and lithium bis(trifluoromethanesulfonyl)imide(LiTFSI) were combined to prepare solid polymer electrolytes(SPEs)with various lithium salt mass fractions. The structure of polyurethane was analyzed by infrared spectroscopy. The thermal properties of polyurethane and electrolytes were tested by TG and DSC. The effects of different Li TFSI mass fractions on the electrochemical properties of the prepared electrolytes were investigated by AC impedance and linear sweep voltammetry. The results indicated that with the increase of LiTFSI mass fraction, the ionic conductivity of PCPU-based solid polymer electrolyte at room temperature firstly increases then decreases and then increases. Especially, when the mass fraction of Li TFSI was 70%, the ionic conductivity of the resulting solid polymer electrolyte reached the maximum value(1.28×10–8 S/cm) among the as-prepared electrolytes. The all-solid-state battery using this PCPUbased electrolyte and LiFePO4 delivered the discharge capacity of 153 mA·h/g at rate of 0.2 C at 60 ℃, and the capacity retention reached 84% after 100 cycles.