High porosity, excellent mechanical strength, interpenetrating network-reinforced double network regenerated cellulose separators for lithium-ion battery

Cellulose material is emerging as a promising alternative to polyolefin separators in lithium-ion batteries (LIBs) due to its wide availability, electrolyte wettability and thermal stability. Based on the non-solvent induced phase separation, dissolving and regenerating the cellulose material by environmentally friendly solvents and non-solvent enables the efficient and pollution-free preparation of porous regenerated cellulose separator (RCS), greatly expanding their application potential in LIBs. However, the mechanical strength of pure RCS still hardly satisfactory, due to the weak intermolecular bonding and loose porous structure. Therefore, this study introduced an acrylic acid/acrylamide (AA/AM) polymer cross-linking system forming an interpenetrating network with the cellulose framework to produce a double network regenerated cellulose separator (DN-RCS) with high mechanical strength and high porosity. At meantime, the special functional group on AA/AM can influence the transport process of Li⁺ and PF₆^- in the electrolyte, helping to form a stable interface on the electrolyte/lithium anode surface to reduce the formation of lithium dendrites. The results showed that DN-RCS possessed excellent mechanical strength and porosity compared to RCS. The high ionic conductivity of DN-RCS (1.03 mS cm^-1) enabled the assembled cell with excellent cycling stability (90.8 % at 0.5C for 100 cycles) and rate performance (65.2 % at 5C). This work provides a further feasible strategy for the preparation of a high-performance cellulose-based separator.