Superior thermal stability of PVA/cellulose composite membranes for lithium-ion battery separators prepared by impregnation method with noncovalent cross-linking of intermolecular multiple hydrogen-bonds

Abstract

Commercial polymer separators in lithium-ion batteries (LIBs) usually have low thermal stability and electrolyte wettability, which can degrade battery performance, especially safety. Here, the novel PVA/cellulose composite membranes (P-CMs) are successfully prepared by noncovalent cross-linking of intermolecular multiple hydrogen-bonds and used as the separator for LIBs. P-CMs show superior thermal degradation (300 °C), and they are heat treated in the tube furnace at 300 °C for 30 min, The P-CMs exhibit negligible dimension change. The 3D-network porous structure produced by phase separation is more suitable for Li+ transport. After 200 cycles at 0.5C, the cell retains 92 % of its capacity retention. Cross-linking structure with abundant polar groups(-OH) improves the electrolyte affinity of the P-CMs. In the LiPF6 electrolyte system, the plentiful polar hydroxyl groups in the P-CMs can interact with the F atoms in the PF6− anionic by means of HF hydrogen bonds, thereby enhancing the affinity of the separator with the electrolyte. In addition, Noncovalent cross-linking of intermolecular multiple hydrogen-bonds reduces free hydroxyl group quantity and improves the interfacial compatibility of P-CMs, and decreases the impedance of LIBs. This study offers a new strategy for the fabrication of superior thermal stability in LIBs.