Relationship Between Electroechanical And Power Generation Properties Of Dielectric Elastomer In Uniaxial Tension Mode

With the increasing demand for electric energy in modern society,researchers are increasingly turning their attention to developing new ways to harvest electricity from clean,renewable sources of energy.Among them,dielectric elastomer generator(DEG)has shown great potential in electromechanical energy conversion.The basic operating element of a DEG includes a flexible dielectric elastomer(DE)film and two flexible electrodes sandwiching the film.Because DE materials have the ability to directly convert mechanical energy into electrical energy,they can potentially be used in energy conversion systems to collect energy from clean and renewable resources.However,the current research on DEG is mainly focused on material preparation and device structure,and there is a lack of theoretical research on the coupling relationship between electromechanical properties and power generation performance of DE materials.In this work,we prepared stretched crystalline brominated butyl rubber(BIIR)composite materials and non-stretched crystalline polymethyl vinyl siloxane(PMVS)composite materials,and characterized their mechanical,electrical and power generation properties.According to the test results,we discussed the relationship between the electromechanical properties(elastic modulus and dielectric constant)and power generation performance(single cycle power generation,energy density and electromechanical conversion efficiency)of DE materials in uniaxial tension mode.The specific experimental conclusions are as follows:(1)The single-cycle power generation and energy density of BIIR-based uniaxial DEG increase with the increase of tensile strain,bias voltage and dielectric constant of the material,and are basically independent of the change of elastic modulus of the material.Its maximum single-cycle power generation can reach 23.36 mJ,and its maximum energy density can reach 39.57 mJ/g.However,the electromechanical conversion efficiency of BIIR-based uniaxial DEG is positively correlated with the dielectric constant and negatively correlated with the elastic modulus of the material.When the tensile strain is small,the electromechanical conversion efficiency of DEG is mainly affected by the single cycle power generation,and increases with the increase of strain.When the tensile strain is large,the electromechanical conversion efficiency is mainly affected by the input mechanical work and gradually decreases with the increase of strain.(2)The single-cycle power generation and energy density of PMVS uniaxial DEG are positively correlated with tensile strain,bias voltage and dielectric constant of the material,and are basically not affected by the elastic modulus of the material.Its maximum single-cycle power generation can reach 17.53 mJ,and its maximum energy density can reach 29.74 mJ/g.However,the electromechanical conversion efficiency of PMVS uniaxial DEG increases first and then decreases with the increase of tensile strain,and is positively correlated with the dielectric constant of the material,and negatively correlated with the elastic modulus of the material.(3)Under the higher tensile strain,the mechanical work input of the tensile crystalline BIIR composites is much greater than that of the non-tensile crystalline PMVS composites due to its mechanical properties.As a result,the electromechanical conversion efficiency of the former is much lower than that of the latter under the same single cycle power generation and the same test conditions.(4)Due to the comprehensive influence of single-cycle power generation and mechanical input,there exists a "tensile strain threshold" in the electromechanical conversion efficiency-bias voltage curve of single-axis DEG.The maximum electromechanical conversion efficiency of tensile crystalline BIIR composites is 8.79%at the tensile strain threshold(400%-500%),while the maximum electromechanical conversion efficiency of non-tensile crystalline PMVS composites is 11.56%at the tensile strain threshold(300%).In summary,based on the study of the power generation performance of two DE materials with vastly different mechanical properties,this paper compared and analyzed the coupling relationship between the electromechanical properties and the power generation performance of DE materials under uniaxial tensile mode,and proposed the performance requirements for preparing uniaxial DEG materials with high energy collection performance:low elastic modulus,high elongation at break,low density,high dielectric constant and excellent insulation.It provides a new direction for the design and preparation of DEG.