The development of stable electrolytes for lithium metal batteries is urgently required. In this work, nanoporous alumina/lithium salt-containing glyme liquid–solid composite electrolytes are proposed. The beneficial interfacial effect and transport properties such as ionic conductivity and lithium transference number can be tuned by variation of the cell temperature and electrolyte salt concentration. In symmetrical lithium/electrolyte/lithium cells, glyme-based liquid–solid electrolytes show superior performance compared to their liquid counterparts. However, even in the high lithium transference number cases, unfavorable mossy lithium deposits can be observed.