Enhancing cellulose‑based separator with polyethyleneimine and polyvinylidene fluoride‑hexafluoropropylene interpenetrated 3D network for lithium metal batteries

Abstract

Aside from the electrolyte, a separator is another important component in lithium-based batteries that has a direct impact on the safety feature and electrochemical performances. To overcome the thermal shrinkage and poor electrolyte affinity of commonly used polyolefin separators, cellulosed-based separators are appealing due to their abundant polar functional groups, thermal stability, and environmental friendliness, especially for large-sized and high-energy-density batteries. Herein, a porous 3D network of polymer cellulose-based separator modified with polyethyleneimine and polyvinylidene fluoride-hexafluoropropylene was created using a non-solvent induced phase separation approach. The lithium metal batteries consisting of PIC separator can deliver up to a specific capacity of 114 mAh g -1 even at high C-rate of 8 C (1.36 A g -1 ) after 300 cycles. Such superior performances of the lithium metal batteries can be attributed to the good wetting ability (390% electrolyte absorption) and high ionic conductivity (0.754 mS cm -1 ) of the as-prepared PIC separator. More importantly, the introduction of polyethyleneimine as a cross-linking agent significantly improves the mechanical strength of the separator, promote the uniform deposition of lithium and compatibility with high voltage (4.4 V) cathode materials LiNi 0.8 Mn 0.1 Co 0.1 O 2 . This work demonstrates a new strategy for the separator design towards high-performance lithium metal battery applications.