The Synthesis Of Multi-doped LiFePO₄/C Prepared From The Converter Sludge

This paper aims at simultaneous recovery of Fe and various valuable elementsselectively from the converter sludge through carbothermal process to prepare acathode material for Lithium ion batteries——multi-doped LiFePO₄.The relevantfactors and control method influencing the structure and electrochemical activity ofthe product were investigated preciously. The outstanding characteristic of thisprocess different from the published reseaches is that all the Fe and doping-elementsneeded in synthesis of multi-doped LiFePO₄come from the industry solidwastes——converter sludge. The results indicated that a materialized recycling of thevaluable elements in converter sludge can be achieved, moreover, a more economicand green route to prepare the cathode materials of Li-ion batteries from the wastes isproposed.In this study, the selective carbothermic method, graded, milling and magneticseparation were used to recover the target elements from converter sludge. To get thefinal product, the converter sludge, mixed with carbon powder, was reducted in anoven at1350℃for2.0hours. Under this technics parameter, the recovery of iron andthe total of doping elements were92%and1.788%respectively. At this time, theproduct was grinded easily and energy was saved. After high grade ore’s grinding, ballmilling and magnetic separation, microalloyed iron powder was obtained, that madethe alloy of Fe and other diphtheria interim metal elements such as Mn, V, Cr, Tisolved. Fe-based compound oxides were prepared at the condition of700℃,5h in thewell furnace to get the precursor of multi-doped LiFePO₄/C. One step solid phasesintering was made, whose calcining parameter was700℃,8h. According to theexperiment, the both of LiFePO₄samples prepared from precursors which wereobtained with carbothermic method in1350℃×2h and1350℃×3h emerging withbulbiform or kind bulbiform pellets, and no obvious reunion were found. Furthermore,integrity crystals were showed, not impurity peaks by X-ray crystallographicanalysis. The batteries prepared from these two samples gave a specific capacity of154mAh g-1and149mAh g-1at0.1C first discharge rate respectively, and they hadbetter multiplying powers, respectively, with a retention of90.2%and91.0%within 30cycles, which indicated good cycling performances.The feature of this study is separating Fe and various transition-metals from non-magnetic substances for great value utilizations with carbothermal process. The restof non-magnetic portion is plunged into building field. In summary, a novel route torecycle the converter sludge in a high added-value and all-components utilization isproposed in this work.The general principle derived from this work is expected tosupply a constructive reference for the studies on other solid industrial wastes.