Effects Of As-doped Graphene Oxide And Porous Structure On The PVDF-HFP Polymer Electrolyte

As a key component of lithium ion battery,polymer electrolytes have attracted extensive attention due to their unique safety property.In this thesis,polymer membranes were designed and fabricated through a phrase inversion method,and graphene oxide（GO）was doped in the poly（vinylidene fluoride-co-hexafluoropropylene）（PVDF-HFP）polymer matrix.After immersing in the liquid electrolyte for activation,GO doped PVDF-HFP gel polymer electrolytes were obtained.Then,a series of measurements were carried out the GO doped polymer membranes as well as the electrolytes.Their surface morphologies,crystallinity,thermal stability,porosity,liquid electrolyte uptake and retention and ionic conductivity were explored thoroughly,and the results showed that the enhancement of ionic conductivity is attributed to the following three factors.Firstly,GO can reduce the crystallinity of polymer matrix.Secondly,as the Lewis-acid,GO can promote the dissociation of lithium salts.Thirdly,GO can provide more passways for the migration of lithium ions.Moreover,the Li/as-prepared electrolyte/LiFePO₄ cells were fabricated and their rate performance and cycle stability were studied.On the other hand,calcium carbonate（CaCO₃）was added in the PVDF-HFP polymer matrix and the porous polymer membranes were fabricated through subsequently CaCO₃ corrosion by hydrochloric acid during the phrase inversion process.The properties of the porous polymer membranes and electrolytes were tested,and the promotion of ionic conductivity is attributed to the crystallinity reduction of polymer matrix and the increase of porosity.In addition,the Li/as-prepared electrolyte/LiFePO₄ cells were fabricated and their rate performance and cycle stability were studied.