Lithium-ion batteries (LIBs) have widely revolutionized our lifestyle, from electronic devices and electric vehicles (EVs) to energy storage systems (ESSs) along with decarbonization trends for sustainable perspective. Unfortunately, the future application of conventional LIBs using liquid organic electrolytes has shown limitation in terms of their energy density and safety concerns. All-solid-state battery (ASSB) are attractive as a next-generation battery to address these issues. Among various solid-state electrolytes, composite solid polymer electrolyte (CSPE) is of particular interest by inheriting the advantages of both inorganic and solid polymer electrolytes. The CSPEs are generally constructed by dispersing (in)active fillers into the polymer matrix to facilitate the dissociation of lithium salts and decrease the crystallinity of polymer matrix, leading to an increase in the ionic conductivity of CSPEs. To further improve the ionic conductivity of CSPEs, the fillers with various morphologies from 0D, 1D, 2D, and 3D frameworks can be used to enhance the conductive pathways for lithium-ions diffusion. In particular, the 3D frameworks greatly improved ionic conductivity by supplying “highways” for lithium-ion diffusion. In addition, 3D frameworks can also prevent the agglomeration of filler particles and the growth of lithium dendrite.

In this study, by employing a 3D ionic transport framework, Li|3D-CSPE|Li symmetric cell could cycle over 1000 h at a current density of 0.1 mA cm^-2. Moreover, all-solid-state Li|3D-CSPE|LiNi_0.8Co_0.1Mn_0.1O₂ cell retained a high capacity retention of 79.4% after 230 cycles at 30 °C. In addition, this novel concept is successfully applied to all-solid-state sodium batteries. The Na|3D-CSPE| Na₃V_1.97Mg_0.03(PO₄)₃/C cell demonstrateed long-term cycling stability at 2 C. This approach provides a practical strategy to address the bottleneck of CSPE to enable safe and high-energy solid-state batteries.