Redox-active Janus separator based on polyaniline nanosheets and bacterial cellulose nanofibers for lithium-ion batteries.

Cellulose nanofibers (CNFs) have received widespread attention in energy storage as an environmentally friendly and stable separator for lithium-ion batteries (LIBs). Polyaniline (PANI) is one representative kind of electroactive pseudocapacitance electrode material. In order to manufacture an electrochemically PANI-functionalized CNF separator which can increase the capacities of the LIBs, this work presents a novel redox-active Janus separator for LIBs incorporating an insulated bacterial cellulose (BC) nanofiber layer with a redox-active PANI layer. The PANI nanosheets synthesized via an emulsion polymerization method is easily covered on the BC layer by filtration, which could provide extra capacity of the LIBs due to the redox reactions of PANI during charge/discharge. The PANI@BC separator exhibits superior electrolyte compatibility and uptake capacity. The specific capacity of the battery paired with the PANI@BC separator, LiFePO, and Li metal can be increased to 129.6 mAh g at a current density of 2C. After 100 cycles at a current density of 2C, the capacity retention of the battery with the PANI@BC separator is about 90 %. Undoubtedly, this research provides valuable insights into developing novel functional separators for the improved performance of LIBs.