Study On Preparation Of Electrode Materials Based On Carboxylic Acid Pyrolysis To Reduction Of Acid Pickling Iron Oxide Red

Lithium-ion batteries have dominated the portable electronics market in the past decade,and are now being paid attention to by the automotive industry.However,large-scale application is limited by cost and performance,among which electrode material is one of the most important factor.On the other hand,with the development of iron and steel industry,the iron oxide produced by acid pickling waste liquor is increasing year by year,so improper treatment will lead to waste of resources and environmental pollution.In order to solve these problems,we systematically studied the preparation parameters of iron oxide and LiFePO4 with excellent performance by using the cheap acid pickling iron oxide red as raw material.Firstly,the pyrolysis process,gas generation type and kinetic parameters of different carboxylic acids were studied by TG-FTIR and TG-MS techniques.The results show that the gases of malonic acid produced during the pyrolysis are mainly H2O,CO2 and compounds containing C=O and C-O functional groups,while the production of maleic acid are only compounds containing C=O,C-O and C-H functional groups.On the other hand,the pyrolysis mechanism of citric acid is similar to tartaric acid,which is divided into two steps:decarboxylationdehydration and decarboxylation.The difference of production between them is that citric acid also generates a small amount of CH4 besides H2O,CO2,CO and compounds containing C=O and C-O functional groups,which illustrates that the production of citric acid has better reducibility.Then,we synthesized heterostructure Fe2O3/Fe3O4/C anode materials by onestep carbothermal reduction method using acid pickling iron oxide red as iron source,citric acid as reductant and carbon source.Among them,the carbon layer improves the conductivity of anode and limits the volume change of iron oxide.Fe3O4 as a transition layer improves the conductivity,too,and Fe2O3 provides high specific capacity,which complements the advantages of the three.The electrochemical tests show that after 100 cycles at 0.5 A g-1,the capacity is 844.5/857.6 mAh g-1 and the coulomb efficiency is 98.5%.Based on the pyrolysis of carboxylic acid,the effects of reaction temperature,citric acid content and soluble starch content on the properties of LiFePO4 were studied.By means of TEM and Raman spectroscopy,we proved that the double carbon coating of LiFePO4 had been successfully prepared.The results show that when the sintering temperature of 650℃,the mass ratio of citric acid to acid picking iron oxide red of 0.4:1 and the content of soluble starch of 20%are chosen,the prepared material has the best electrochemical performance.This is mainly due to the double-layer carbon coating which effectively improves the conductivity of the sample and increases the diffusion rate of lithium ion.