Preparation And Electricity Storage Performance Of The Sand-particle Interlayer Capacitor(SIC)

In order to cope with the climate problems caused by traditional energy sources,wind power,photovoltaic and other new energy generation methods are gradually becoming important national development planning power generation methods.Most of the large wind power and photovoltaic bases are built in desert and desert areas which are less populated but rich in resources.Supercapacitors are regarded as one of the most potential energy storage devices because of their high capacity,fast charging and discharging,and high cycling life.However,the application of supercapacitors in large-scale integrated new energy systems is limited due to their high cost and environmental pollution drawbacks.Sand,as a very common natural substance,is rarely used on a large scale in productive activities for the benefit of human beings,except for construction purposes.Sand grains(mainly composed of silica),not only have stable physical and chemical properties,good dielectric properties,and high specific surface area,but also exhibit excellent electrical storage behavior.This paper,based on the research of sand particles charging and power storage,focuses on the goal of using sand particles for energy storage devices to develop a new type of low-cost electricity storage device.The main work is as follows.Firstly,a capacitor with sand interlayer(SIC)device was fabricated by using flat graphite paper as the two electrodes,a mixture of fine sand and saturated sodium chloride solution as the quasi-solid interlayer,and a ring-shaped rubber ring as the side support.A comparison was made with pure solution capacitors and diaphragm capacitors made in the same way,and the results showed the SIC device with the best capacitance performance.Secondly,the storage performance and cost analysis of SIC devices were studied separately.In terms of performance,the SIC device showed good electric double-layer capacitor behavior with a high area specific capacitance ratio of 12.34 m F/cm~2and an energy density of 1.72 Wh/cm~2,as well as excellent cycling performance(up to 100%capacitance retention at 5000 cycles).In addition,it demonstrated outstanding power storage performance with repeatability and performance stability for one month of continuous operation.In terms of economy,the total investment cost of SIC devices in the desert integrated energy system is only 8,793 yuan per kilowatt,which is much lower than the battery type energy storage equipment,and there is no environmental restriction.Besides,on the basis of"photovoltaic sand treatment",it can also drive the development of the new energy industrial park of"sand treatment with sand".In terms of environment,the main materials of the SIC device are composed of graphite,brine and sand,which are essentially harmless to the environment.The use of countless sand grains in the desert for energy storage provides a new way to"turn waste into treasure".Finally,the influence of the surface of sand grains on the charge distribution of the interface was added to the original"electrode-solution"interface,and the reason why the addition of sand grains greatly increases the electric capacity-the special surface morphology and high specific surface area of sand grains-was well explained,and the sand charging model was proposed.A simplified model of SIC was also proposed based on the approximate formula of specific capacitance of porous electrodes.Then the effects of area,thickness,sodium chloride solution addition and sand particle size on the storage performance of SIC were investigated from the two theoretical models and experiments,respectively.The experimental results showed a basic agreement with the results of both theoretical models,but most of the experimental values showed a better agreement with the sand grain charging model.With the theoretical models,the optimal average particle size of sand particles and the content of sodium chloride solution were given as 111μm and 21%,respectively.