墨水涂覆法制备硫化物全固态锂离子电池

摘要

An ink coating method was developed to prepare sulfide solid electrolyte for all-solid-state lithium ion batteries. The crystalline Li8P2S9synthesized by vacuum sintering was dispersed in N-methyl-2-pyrrolidone (NMP) solvent to form a homogeneous ink. The results show that during the action of NMP, the particle size of Li8P2S9 decreases from 10 μm to 1 μm while the crystalline structure of Li8P2S9is unchanged, which benefits contacts between Li8P2S9 particles. Through adding a certain amount of poly(vinylidene fluoride) (PVDF) as an organic binder, the ink is directly dropped on LiFePO4 cathode sheet and then heated at 120℃ to remove NMP. When the mass ratio of Li8P2S9 to PVDF is 10:1, the solid electrolyte has an ionic conductivity of 2.03×10−4 S/cm at 30℃ and an electrochemical window of 5.15 V at 25℃. In addition, the LiFePO4/electrolyte/Li batteries assembled by such facile method show good charge/discharge performance. At the rate of 0.2C, the average specific capacities of 113.7 mA∙h/g for 100 cycles are delivered at room temperature with the Coulombic efficiencies close to 99% for each cycle.%采用墨水涂覆技术制备基于硫化物的电解质薄膜及其全固态锂离子电池。通过N-甲基吡咯烷酮(NMP)溶剂对真空烧结法制得的Li8P2S9粉末进行处理，获得均匀、稳定的湛蓝色Li8P2S9墨水。研究结果表明：NMP溶剂处理后的Li8P2S9颗粒粒径从10μm降低到1μm左右，物相晶体结构不变，但改善颗粒间的接触性能。在Li8P2S9墨水中添加一定量的聚偏二氟乙烯(PVDF)黏结剂，溶解完全后将墨水滴涂在磷酸铁锂正极表面，除去溶剂即可一步实现电解质的成膜及电解质与正极的复合。当PVDF与Li8P2S9的质量比为1：10时，电解质膜30℃下的锂离子电导率为2.03×10−4S/cm，25℃电化学窗口为5.15 V。以该墨水涂覆法制得的LiFePO4/Li电池可在室温下稳定工作，0.2C下循环100圈的平均比容量为113.7 mA∙h/g，库仑效率为99%。