Research On The Modification Of Lithium-ion Battery Separator Based On PVDF-HFP

As lithium ion batteries have been widely used in our daily lives,the safety,cycle life and high power usage of lithium ion batteries are becoming significant.The separator is one of the critical factors that ensure the safety of batteries.Thus,how to synthesize separators with a simple and effective method is one of the urgent issues in recent researches.To investigate those issues,the study has been focused on the separators with decent mechanical strength and remarkable thermal stability,leading to high rate performance,superior stability and excellent cycling stability of lithium ion batteries.Our study has concentrated on polyvinylidene fluoride-hexafluoropropylene?PVDF-HFP?separators,which are modified by different methods.The main contents of our study are shown as follows:Firstly,we summarized the applications of Li-ion batteries,including the working principle,classification and future development of Li-ion batteries.We illuminated the function,and requirements of separators in Li-ion batteries,and clarified the current researches situations of Li-ion battery separators.The research direction of this paper is related to the modification of the polymer electrolyte PVDF-HFP separators.Secondly,the PVDF-HFP-LMFP separators based on the cathode material LiMn_0.5Fe_0.5PO₄?LMFP?have been studied by adding cathode material LMFP into separators to enhance the battery performances.To study the effect of adding cathode materials into PVDF-HFP separators,LMFP has been selected as an additive to prepare PVDF-HFP-LMFP separators.Using the PVDF-HFP-LMFP separators,half-cells were assembled with LiMn_0.5Fe_0.5PO₄/C?LMFP/C?as cathode material and lithium mental discs as anode.Additionally,the PVDF-HFP separators were prepared using the mixed solvents N-methyl pyrrolidone?NMP?and acetone.The PVDF-HFP separators with a polylaminate structure were synthesized through an efficient and low-cost method.The tests on the contact angle,mechanical XRD,thermal stability and other aspects of the separators prove that the separators owns good wettability,excellent ionic conductivity and superior stability,that can meet the needs of the safety and stability for separators used in the high power Li-ion batteries.Finally,based on the mixed solvents method mentioned above,the ceramic material was recruited to further improve the performances of the separators.In this paper,the effect of ceramic material on various properties of PVDF-HFP separator was explored by comparing with pure PVDF-HFP separator with the example of alumina?Al₂O₃?.The influence of Al₂O₃ on the morphology and structure of the separators was explored by scanning electron microscopy?SEM?and X-ray diffraction?XRD?while a series of electrochemical tests were carried out to prove the advantageous properties of modified separators.In short,the polymer electrolyte PVDF-HFP separators were modified by adding additives or changing the solvent system of preparing solutions.We studied the effects of various factors on polymer separators including microstructure and macroscopic physical properties,and the results not only contribute to obtain an efficient,simple and cost effective approach to synthesize separators exhibits high rate capability,high stability,excellent mechanical properties,but also benifit to the further study of Li-ion battery separator.