Exploring Minimalistic Cells With High Energy Density

Cells with high energy density have played an increasingly important role in modern society.In order to meet various application requirements,cell systems become increasingly complicated and elaborate.If this trend overspread excessively without intervening measure,the cell systems will most likely be in plight.Because during the manufacturing process of cells and relevant materials,this will lead to unnecessary wastes in the aspect of time,human resource,energy,material and so on.Besides,this will lead to a higher environmental burden.On the basis of this concern,an attempt to apply the idea of "minimalism" to cell systems when select electrode material and design cell configuration is made.The specific research work can be divided into the following two aspects:(1)Mesocarbon microbeads(MCMB),with abundant sources and simple processing,are the industrial raw material for the manufacture of spherical artificial graphite electrode materials.We try to directly use MCMB raw materials as electrode materials to assemble symmetrical carbon batteries based on quaternary ammonium salt organic electrolytes.The volumetric energy density of the cell is close to that of electric double-layer capacitors composed of symmetrical activated carbon electrodes(AC).In this paper,traditional electrochemical testing methods such as galvano-static charge and discharge,cyclic voltammetry,electrochemical impedance spectroscopy(EIS)as well as insitu characterization methods such as electrochemical dilatometer(ECD)and electrochemical quartz crystal microbalance(EQCM)are used to explore the behavior of MCMB storing ions.Moreover,the de-solvation phenomenon of ions during the electrochemical intercalation of MCMB has been revealed.(2)In this section,the negative electrode material is not used when assembling the battery,but the metal ions in the electrolyte undergo an electrochemical reduction reaction during the first charging process of the battery.Then the deposition process is happened on the negative current collector to insitu form a layer of metal and the metal plays the role of the negative electrode.This kind of "Anode-free battery" can greatly increase the energy density of metal batteries.In the past,cathode materials capable of reversibly storing metal ions were generally used in anode-free batteries.However,the preparation process of this kind of material is generally cumbersome and this kind of material may also involve metal materials which have the valence change.Therefore,we try to use anion-storage materials,such as activated carbon,graphite,and conductive polymers,as the cathode material of anode-free batteries.This kind of materials are abundant in sources and have been industrially produced on a large scale.In this section,traditional electrochemical tests are conducted to preliminarily explore the effects of alkali metal ions,cathode materials,and current collectors on battery performance.