Investigation Of The Novel PPy/OMMT Composite Battery Membranes

The Li-ion battery plays an increasingly important part in portable equipment with high energy storage and electric vehicle.As an essential part of Li-ion battery,the membrane can improve cycle performance,conductivity and so on.The preparation of a novel composite Li-ion battery membrane has been the focus of a large number of researchers.In this essay,at first,polypyrrole/organic montmorillonite（PPy/OMMT）composite material is prepared.And then we make out what influence PPy/OMMT composite material has on the mrophology of membrane,the electrode interface and the cycle performance.Finally,referring to the preparation process of PPy/OMMT-PVDF/PMMA composite membrane,PPy/OMMT-PVDF/PMMA,a novel solid electrolyte composite membrane is prepared.The results are gotten as follows:（1）During the organic cation exchange reaction and the step-growth polymerization of pyrrole（Py）monomer,with MMT as the raw material,PPy/OMMT,a novel composite material with high interlayer spacing（2.75 nm）and high specific surface（28.32 m²/g）is prepared.（2）As the basic material,the surface of PE membrane is coated with PPy/OMMT by the draw-off method,which is known as PPy/OMMT-PE composite membrane.The composite membrane with a spongy micro-pore structure,featured by high specific surface area and porosity plays an important role in improving the thermal stability,mechanical capacity（3.39 MPa）,liquid absorption rate（349%）and ionic conductivity（4.3×10^-33 S/cm）of PE membrane.Equipped with PPy/OMMT-PE composite membrane,Li-ion cell battery takes on better electrochemical cycling performance and the capacity retention ratio at the high temperature.（3）PPy/OMMT-PVDF/PMMA composite membrane is prepared by doping with PPy/OMMT.Because of the"agglomeration"function of PPy/OMMT,the porous structure on the outside and inside of PPy/OMMT-PVDF/PMMA composite membrane contributes to improving its electrolyte uptake.The physical and electrochemical properties of the composite membrane are both improved by doping with PPy/OMMT.Meanwhile,PPy/OMMT will eliminate HF and thus increase the content of LiNi_1/3Co_1/3Mn_1/3O₂ cathode material.（4）PPy/OMMT-PVDF/PMMA solid electrolyte composite membrane is prepared by the doping method.By contrasting physical and electrochemical characterization of PPy/OMMT-PVDF/PMMA solid electrolyte composite membrane with that of PVDF/PMMA solid electrolyte composite membrane,PVDF/PMMA solid electrolyte composite membrane doping with PPy/OMMT has smaller aperture,larger volume and more Li-ion conductive paths,which enhance the ability of Li-ion mobility.By doing so,the interface resistance between LiNi_1/3Co_1/3Mn_1/3O₂ and PVDF/PMMA solid electrolyte composite membrane reduces.and then improve the cycle performance and specific capacity of Li-ion battery.