Uniform and porous nacre-like cellulose nanofibrils/nanoclay composite membrane as separator for highly safe and advanced Li-ion battery

Although nacre-like membrane composed of cellulose nanofibrils (CNFs) with nanoclays has excellent mechanical and thermal stability, its dense and uneven structure impedes its application as separator for Li-ion batteries (LIBs). In this work, in order to design a suitable nacre-like membrane to achieve a safe and advanced LIB, a novel biobased, uniform, porous and nacre-like CNF/Laponite composite membrane was fabricated via simple and scalable sol-gel process for the first time. Meanwhile, a mild and green structure optimization strategy was carried out in which polyethylene glycol (PEG) was added to regulate the interface between CNF and Laponite and then removed to develop uniform porous structure for membrane. The uniform and porous structure of the composite membrane was demonstrated by TEM-EDX and SEM-EDX characterizations. The nacre-like membrane showed excellent safety, high porosity (68 %), enhanced electrolyte uptake (260 %) and high ionic conductivity (0.977 mS cm(-1)). Cells assembled with nacre-like membrane as separator showed enhanced cycling performance (92.6 % of discharged capacity retention after 100 cycles at 0.5 C) and improved rate capability compared to commercial PP separator. Hence, these advantages make the novel and ecofriendly CNF/Laponite nacre-like membrane a promising candidate for fabricating safe and high-performance sustainable LIBs.

Automated summary

A novel biobased CNF/Laponite composite membrane with uniform, porous and nacre-like structure was fabricated for safe and high-performance sustainable lithium-ion batteries. This membrane showed excellent safety, high porosity, enhanced electrolyte uptake and high ionic conductivity, leading to improved cycling performance and rate capability of the batteries compared to commercial separators.