Performance Test Of Organic Electrolyte Lithium Air Battery And Mesoscropic Mass Transfer In Its Membrane

Lithium-air batteries,as an efficient and clean energy storage system,are expected to become the mainstream direction of chemical batteries due to their ultra-high energy density,smooth discharge form,and long storage life.However,due to the problems of low cycle times and large over-potential during charging and discharging,application range of lithium-air batteries is limited to a certain extent.Polymer electrolyte separator is one of the key material in lithium-air batteries.Study on the transfer characteristics of lithium ions in the separator is of great significance to improve the performance of lithium-air batteries.This article referred to a large number of domestic and foreign literature on lithium-air batteries,and introduced the classification,working principle and key materials of lithium-air in detail.Based on the theoretical research foundation,an organic electrolyte lithium-air battery test platform was established,and electrochemical performance test research was conducted on the organic electrolyte lithium-air battery.The influence of the thickness of the electrolyte separator on the performance of the lithium-air battery and the lithium-air battery separator,as well as analysis of lithium-air battery separator's Mesoscopic Transmission Characteristics were studied with intention.The specific research content of the paper is as follows:Lithium perfluorosufonate(PFSA-Li)ion-exchange membranes with different thicknesses were prepared by chemical neutralization and assembled in battery molds.The charge and discharge characteristics,cyclic voltammetry characteristics and AC impedance characteristics are analyzed and summarized through the overall battery charge and discharge test,cyclic voltammetry(CV)test and electrochemical impedance spectroscopy(EIS)test.The results show that the thickness of the ion exchange membrane will affect the discharge capacity of the battery.The discharge capacity of the battery increases along with reduction of ion exchange membrane thickness.Reducing the thickness of the ion exchange membrane can reduce the ohmic resistance of the lithium air battery and increase the number of cycles of the lithium air battery.In order to investigate the diffusion law of lithium ions in the separator of lithium air battery,a self-designed ion exchange is adopted.The membrane mass transfer tester tested the transfer characteristics of lithium ions in the ion exchange membrane.The absorbance of the solution was measured using a dual-beam ultraviolet-visible spectrophotometer.The lithium ion diffusion coefficient was calculated using Darcy's law.Effects of the temperature,organic liquid volume and Lithium salt concentration on the transmembrane transfer of Lithium Ions in PFSA-Li Film are analyzed in this paper.The test found that:improving the ambient temperature,increasing the organic liquid content in the PFSA-Li film,and selecting the appropriate lithium salt concentration can help lithium ions pass through the PFSA-Li film.The simulation part studied the transfer characteristics of lithium ions in the organic electrolyte lithium air battery separator from the mesoscopic perspective.By using the dissipative particle dynamics DPD simulation method,the coarse-grained model of lithium perflourinated acid(PFSA-Li)ion exchange membrane,organic solvent ethylene glycol dimethyl ether(DME)and lithium herafluoroph osphate(LiPF6)by means of molecular simulation software Materials Studio are constructed.The three-dimensional topology of lithium-ion channels in the PFSA-Li membrane is analyzed,and effects of temperature,organic liquid volume and lithium salt concentration on the diffusion behavior of lithium ion in the PFSA-Li membrane is studied.When the content of organic liquid in the PFSA-Li membrane reaches a certain level,the ionic clusters are connected to each other,and finally form a continuous cavernous channels through the membrane.Rising the temperature and increasing the content of the organic liquid are beneficial to the diffusion of lithium ion in the PFSA-Li membrane.When the concentration of lithium salt is 1.0 mol/L,the diffusion of lithium ion is the best.