Application Of Biochar As Cathode Materials Of Lithium Oxygen Battery

With the improvement of people’s living standard and further demand for energy,developing high energy,clean and safe chemical power system has become an important demand of social development.Lithium air batteries show a high theoretical specific capacity and specific energy,environmentally friendly,reversible and other advantages.The mechanism of lithium air batteries are base on reaction of oxygen with lithium in non-aqueous electrolyte.At present,the research on lithium air batteries is still in its initial stage and there are still a lot of technical problems need to be resolved.In this paper,a friendly,cheap and full life cycle green material is selected,pomelo peel.A lithium air battery with better cycle stability and higher energy density is obtained by controlling the structure of the positive electrode material.This research is mainly to select a kind of biomass-pomelo peel,which is modified by three different methods and then assembled lithium air battery to test its performance.Its good electrochemical performance reflects the good performance of the material,and it also reflects the operability of material preparation method which provides an important theoretical basis for the research of the lithium air battery.The mixture of pomelo peel and KOH was placed in a nitrogen atmosphere and then pyrolyzed at 900℃for 2h to obtain activated biochar.At the same time,the non-activated pomelo peel prepared under the same conditions and was used as blank control.On the basis of activated biochar,a metal catalyst(Fe)was added in order to further reduce its overpotential and optimize battery performance.Activated biochar as the air cathode of lithium-air battery exhibits higher specific capacity and stable cycling performance.This material has good catalytic activity for OER and ORR.Its porous honeycomb structure cab control the morphology of the cathode and can significantly enhance the performance of the lithium air battery.Activated biochar has porous structure and large surface area(900㎡/g)and pore volume(0.090 cm3/g).On the one hand,it promotes the transmission of reactants such as oxygen and electrolytes.On the other hand,it provides sufficient space for the accumulation and storage of discharge products,reducing concentration polarization and slowing the polarization degree of electrodes.Compared with a lithium-air battery with an inactive carbon as an cathode,the activated carbon exhibits better discharge specific capacity(7800 mAh/g at 0.02 mA/cm~2)and long-life performance(466 cycles with a cut-off capacity of 500 mAh/g at 0.1 mA/cm~2)and good rate capability.Biochar added with catalyst also has a larger surface(768㎡/g)and pore volume(0.079 cm3/g).By the scanning electron microscope,it can be seen that the added metal catalyst is evenly distributed in the pore structure.Compared with the activated biochar,the first charge discharge performance has improved,the discharge platform to improve 120mV and the charging platform fell 120 mV.