A renewable membrane with high ionic conductivity and thermal stability for Li-ion batteries

Traditional polyolefin membrane for lithium ion batteries (LIBs) is not renewable and it has poor thermal stability and wettability. Here, we designed a porous membrane based on the hydrogen bonding effect between the renewable cellulose nanofibers (CNF) and lignosulphonates (LS). In the membrane, the CNF endows it with good flexibility, and the functional groups can improve its wettability with the electrolyte. The LS plays the role of dispersing the CNF to form uniform porous structure. Moreover, the sulfonate groups in LS can also enhance the ionic conductivity. Under the synergistic effect of CNF and LS, the membrane exhibits high ion conductivity of 1.99 mS cm-1, high electrolyte uptake of 213% and high thermal stability up to 270 °C, which is much higher than those of commercial Celgard 2325. The LIBs with the designed separators display high capacity of 188 mAh g−1 and high voltage of 4.8 V. This research provided an efficient strategy for fabricating the membrane with low cost and high performance for LIBs.