石榴石型固态电解质的掺杂与表面包覆改性研究

发展绿色能源是解决能源危机和保护环境的有效途径之一。锂离子电池作为一种高效的储能器件，利用锂离子的传导和氧化还原进行能量的转换与使用。相比化石能源，它具有绿色环保、自放电小和方便携带等优点，是当下广泛使用的生活和工业用品。传统锂离子电池因使用易燃有机液态电解液导致了易发生燃、爆安全事故，同时其较低的能量密度难以满足人们对高能量密度的要求。开发兼具高能量密度和安全特征的固态电池是当下一项重要课题。石榴石型固态电解质（Li₇La₃Zr₂O₁₂，LLZO）具有不可燃性与较高的机械强度，可以有效防止安全事故的发生；它的化学稳定性和宽电化学稳定窗口也使其有望被应用在高能量密度的固态电池中，因此受到广泛研究。然而，室温锂离子电导率低、空气稳定性差、容易产生锂枝晶等问题阻碍着石榴石型固态电解质的应用。本工作以LLZO作为研究对象，致力于通过创新LLZO合成方法来促进其实际应用。

针对锂离子电导率低的问题，采用后掺杂方法成功合成了Al掺杂LLZO基固态电解质，其室温下电导率为5.331 ×10^-4 S cm^-1、致密度为92%、活化能为0.25 eV，具有高离子电导率、高致密度和成本低等特点；以该电解质为基础的锂对称电池可以稳定循环1400 h，展现出良好的对锂稳定性；其在NCM811半电池体系中表现出良好的稳定性，与同类研究对比展现出高性能、低成本的优点。针对空气稳定性、容易产生锂枝晶的问题，创新地提出Li₃PO₄表面包覆LLZO颗粒的方法，成功降低了LLZO的表面残碱，使之可以用于合成聚己内酯（PCL）基复合固态电解质、以聚偏二氟乙烯（PVDF）作为粘结剂进行隔膜涂覆，扩展了LLZO的应用方向；在锂对称电池中，Li₃PO₄表面包覆的LLZO电解质的临界电流密度由0.7 mA cm^-2提升至1.6 mA cm^-2，可以更有效地抑制锂枝晶产生。

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