The article "Tunneling Interpenetrative Lithium Ion Conduction Channels in Polymer-in-Ceramic Composite Solid Electrolytes" by Lei Zhu et al. addresses the challenges in achieving high ionic conductivity and mechanical strength in polymer-in-ceramic composite solid electrolytes (PIC–CSEs). The authors introduce the use of polymer-compatible ionic liquids (PCILs) to mediate between ceramics and the polymer matrix, solving two key issues: ceramic aggregation and the lack of conducting pathways at the ceramic-polymer interfaces. By coating ceramic particles with PCILs, the ceramic particles become active Li+ ion superconductors, enhancing the ionic conductivity and mechanical properties of the PIC–CSEs. The resulting PIC–CSE, denoted as PELL60, exhibits an ionic conductivity of 0.83 mS cm−1, a Li+ transference number of 0.81, and an elongation of ~300% at 25 °C. Electrochemical tests on full cells based on PELL60 show satisfactory cycling performance, with energy densities of approximately 310.0 Wh kg−1 (424.9 Wh kg−1 excluding packing materials) and excellent safety characteristics under abuse tests. This work paves the way for the commercial viability of PIC–CSEs in solid-state lithium metal batteries (SSLMBs).The article "Tunneling Interpenetrative Lithium Ion Conduction Channels in Polymer-in-Ceramic Composite Solid Electrolytes" by Lei Zhu et al. addresses the challenges in achieving high ionic conductivity and mechanical strength in polymer-in-ceramic composite solid electrolytes (PIC–CSEs). The authors introduce the use of polymer-compatible ionic liquids (PCILs) to mediate between ceramics and the polymer matrix, solving two key issues: ceramic aggregation and the lack of conducting pathways at the ceramic-polymer interfaces. By coating ceramic particles with PCILs, the ceramic particles become active Li+ ion superconductors, enhancing the ionic conductivity and mechanical properties of the PIC–CSEs. The resulting PIC–CSE, denoted as PELL60, exhibits an ionic conductivity of 0.83 mS cm−1, a Li+ transference number of 0.81, and an elongation of ~300% at 25 °C. Electrochemical tests on full cells based on PELL60 show satisfactory cycling performance, with energy densities of approximately 310.0 Wh kg−1 (424.9 Wh kg−1 excluding packing materials) and excellent safety characteristics under abuse tests. This work paves the way for the commercial viability of PIC–CSEs in solid-state lithium metal batteries (SSLMBs).