A mixed ion–electron conducting polymer interlayer is developed through a rapid ice-templating method, yielding hierarchically porous conducting polymer nanosheets functionalized with Li⁺-conducting polymeric nanoparticles. This interlayer enhances charge transport, suppresses redox shuttling, and achieves near-theoretical discharge capacities with good cycling stability in both lithium–organic and lithium–sulfur batteries.

Despite ongoing efforts to develop sustainable lithium batteries with eco-friendly cathode materials, such as organic or sulfur-based compounds, challenges such as poor charge transport and severe redox shuttling persist. Interface engineering at the electrode–electrolyte interface remains crucial for improving the performance of these batteries. Herein, an ice-templated synthesis of mixed ion-electron-conducting interlayers design is presented to enhance redox kinetics and cycling stability in lithium batteries. The interlayers consist of hierarchically porous conducting polymer nanosheets with Li⁺-conducting polymeric nanoparticles anchored to the pore walls. This architecture simultaneously enhances electrical conductivity (6.0 S cm^{− 1}) and ionic conductivity (0.22 mS cm^{− 1}), and effectively mitigates shuttle effects by confining soluble redox-active species within the porous interlayer. When applied to lithium-organic batteries with C₆O₆ cathodes, the batteries achieve a high specific capacity of 557 mAh g^{− 1} at 48 mA g^{− 1}. In lithium–sulfur cells with elemental sulfur cathodes, the cells deliver 912 mAh g^{− 1} at 167 mA g^{− 1}, 789 mAh g^{− 1} at 0.84 A g^{− 1}, 717 mAh g^{− 1} at 1.7 A g^{− 1}, and 544 mAh g^{− 1} at 3.3 A g⁻¹ with cycling stability over 120 cycles. This study establishes a scalable and adaptable platform for the advancement of sustainable lithium battery technologies.