The Studies On Preparation And Electrochemical Performances Of Porous Carbons Electrode Material For Lithium Air Battery

Crucial environmental issues together with energy resource crisis make thedevelopment of improved lithium batteries a worldwide imperative. Although largecapacity lithium-ion battery for electric vehicle (EV) has attracted much attention, itsenergy density is still limited by the positive electrode. Lithium air batteries exhibit amuch higher theoretical specific energy than any other energy storage systems in thattheir active cathode material, oxygen, does not have to be stored in the battery, butrather it can be accessed from the environment. Lithium air battery has the highesttheoretical specific energy of11,140Wh kg-1, excluding O2, which provides energydensity an order of magnitude larger than conventional batteries and has the potentialto become a new generation of secondary battery. But, the discharge product Li2O2and Li2O are both not soluble in organic electrolyte and deposited in a carbon-basedporous air electrode only. Therefore, the design of a carbon matrix with a favorablestructure will be an important step to improve cell performance. Meanwhile, the airelectrode needs to add catalyst to improve the O2reduction reaction. In this paper, thestudies on preparation and electrochemical performances of catalyst and porouscarbons electrode material were investigated.(1) A series of manganese dioxides were prepared by hydrothermal. The preparedα-MnO2nanord with a diameter of100nm and a length of2um, and the β-MnO2wasgranular. The α-MnO2shows a highest initial discapacity of1239.9mAh g-1anddischarge plateau of2.5V at a current density of0.15mA cm-2.(2) The MOF-PC was a graphitized amorphous caborn and synthetized byhydrothermal. The as-prepared MOF-PC with a specific surface area of654m2g-1,pore volume of0.76cm3g-1. The MOF-PC carbon black air electrode shows a highercapacity of1502.9mAh g-1at a current density of0.15mA cm-2, compared totraditional Super P carbon black. And the cell retention remains with the dischargecapacity of287.6mAh g-1after ten cycles.(3) A series of hierarchically porous carbons were prepared by nickel nitrate andsurfactant. All carbon samples were mainly mesoporous materials and possess similarpore size and pore size distribution. The HPCs-3shows the largest specific surfacearea of691cm3g-1, and the highest discharge capacity of2050mAh g-1at the currentdensity of0.1mA cm-2. In the case of deep discharge at a rate of0.1mA cm-2, thecapacity retention remains of HPCs-3was rather poor, by avoiding deep discharge and restricting discharge capacity only to800mAh g1, the cell exhibits good capacityretention for10cycles.