In-situ solidification POSS-crosslinked polymer electrolytes in multiscale nanocellulose membranes for high-performance all-solid-state lithium batteries

All-solid-state lithium batteries (ASSLBs) are in the spotlight due to their superior safety and enhanced energy density. However, the inferior interface compatibility of electrolyte/electrodes and room temperature ionic conductivity hinder their practical application. Here, we innovatively utilize POSS-crosslinked high-permittivity vinylene carbonate and ionic liquids in multiscale nanocellulose membranes to in-situ solidify polymer electrolytes, achieving ASSLBs with excellent interface compatibility and ionic conductivity. Specifically, multiscale nanocellulose membranes prepared from cellulose nanocrystals and cellulose nanofibers serve as support separators, which can effectively absorb polymer precursors and facilitate lithium-ion transport through abundant hydroxyl groups and nanostructures, realizing high ionic conductivity of 1.10 × 10⁻⁴ S cm⁻¹ at 30 °C. Moreover, the octa-functionalized POSS further enhances the solid-solid interface by forming a highly crosslinked polymer network through in-situ polymerization with active monomers, thereby strengthening the stability of ASSLBs. The above in-situ solidification strategy ultimately achieves robust electrode/electrolyte interfaces and optimizes the long cycle capability of ASSLBs. Li||Li cells can run stably for more than 1200 h at a current density of 0.2 mA cm⁻² without noticeable polarization. Furthermore, Li||LFP cells maintain excellent stability after 800 cycles at 1C with a superior capacity retention of 70 % at 55 °C and exhibit excellent rate performance. This work provides an effective strategy to fabricate high-performance ASSLBs and a new solution for the high-value utilization of naturally renewable cellulose resources.