Studies On The Performance Degradation And Recovery Of LiFeO₄

LiFePO₄is still the one of the focus of the current study because of it’s advantagessuch as the high energy, high operating voltage, good safety performance, envoronmentalfriendly, low cost and so on, also account for a certain proportion of the market. With themature of production technology, the yied of LiFePO₄is incresing. the storage problemworthy of attention and research.as known to all, low intrinsic conductivity restricts itswidespread use, the modified methods are varied, also decide the factors influencing theperformance of LiFePO₄are varied, on the basis of the analysis, the paper mainly studythe influence of moist air and air-crushed treatment on the LiFePO₄.Explore the influence of damp treatment to the LiFePO₄and its precursor spraypowder, which are put into the constant humidity environment. weigh some LiFePO₄tomake the button batteries, compare the difference of electrochemical propertiesbetween before damp and after, analysis the influence of treatment time on properties.Sinter the precursor spray powder at the720℃,then make button batteries to compare theelectrochemical properties, use the thermal stability analysis method（TG-DSC） andstructure and morphology analysis method（XRD,SEM） to study the performancedegradation and recovery mechanism, finally find the best method to recover theperformance.Explore the influence of air-crush treatment on the structure and performance, usethe C12H22O11to make carbon coating, to decide the sinter temperature by TG-DSC,make the structure and morphology analysis by XRD,SEM, raman spectroscopy,summarize the performance degradation and recovery mechanism.Studies show that the performance of LiFePO₄have degradation after damptreatment, the degradation is worse with the extension of time. But after someappropriate treatment, the performance will make a big degree of recovery, add trace amounts of C12H22O11into the damped LiFePO₄then sinter at550℃, results showthat the specific capacity and cycle performance have95%recovery. the results showsthat LiFePO₄’s discharge capacity Sintered by the damped precursor spray powderobviously lower than non-damped powder. the time of exposure to moist air more shorter,then the sintered powder’s performance will has less decline in the rate of0.2C,but withtime increasing, the performance will have a tendency to decrease. different temperaturesof heat treatment were carried out on the damped powder. The results demenstrate thatkeep2hours at200℃，then sinter at725℃will make a considerable degree ofperformance recovery, especially for the high-rate performance.SEM results and the reduction of carbon content verified the broken of carboncoating layer, which deteriorates the conductivity of Lithium iron phosphate, with thedegradation of the capacity and cycle performance. The results show that coat somecontent carbon on the crushed Lithium iron phosphate then sinter at720℃will make agreat degree of performance recovery, the specific capacity will have150mAh/g.