Study On The Performance Of Recovery And Regeneration From LiFePO₄ Cathode Scraps

LiFePO4 batteries have been considered as an important battery system in power batteries and energy storage.As the market of power batteries has become the largest engine in the global lithium battery market,the demand and usage of LiFePO4 batteries have also increased.Along with this,there will be a large number of LiFePO4 batteries that face the problem of end-of-life disposal in the near future.It is estimated that there will be about 9400 tons of LiFePO4 batteries scrapped in China by 2021.If these LiFePO4 batteries are discarded without recycling,it will undoubtedly lead to serious environmental pollution and waste of resources.For example,LiPF6 in organic electrolytes will gradually transfer to soil and groundwater,causing environment pollution.LiFePO4 batteries are still rich in Li resource,the Li content in spent LiFePO4 batteries is even higher than natural ore.Lithium salt is indispensable material for lithium batteries,with the increasing consumption of lithium batteries year by year,the shortage of lithium resources has increased.No matter from the point of view of recovery or the perspective of environmental protection,it is imperative to recycle the spent lithium batteries.And the primary study tasks are as follow:(1)A simple and economical method for recovery and repair is proposed for the leftover materials in the production process of LiFePO4 cathode materials.The LiFePO4 cathode material was soaked in NaOH solution to separate aluminum foil and soaked in NMP to initially remove the PVDF.The effect of calcination temperature on the morphology and electrochemical performance of the material was explored.The results show that the LiFePO4/C composites calcined at 500 ? have relatively uniform morphology and high tap density,The initial discharge specific capacity is 157.5 mAh g-1 at a rate of 0.2C.(2)For those LiFePO4 cathode scraps that cannot be well-repaired for their electrochemical performance,the valuable elements of Al?Li and Fe in LiFePO4 cathode scraps were recovered by hydrometallurgy process.When the concentration of HC1 is 5 mol/L,the ratio of liquid to solid is 12.5.After heating and stirring at 60 ? for 4 h,the dissolution rate of the mixed material reaches 98%.Li is recovered as Li3PO4 and Fe is recovered as FePO4.The results of SEM show that adding SDS as a dispersant during precipitation of FePO4 can lead to better morphology.(3)New LiFePO4 cathode material was prepared through hydrothermal method by using recovered Li3PO4 as lithium source.The effect of hydrothermal reaction temperature on the morphology and electrochemical performance of the final LiFePO4 material was explored.The LiFeP0O/C prepared at 200 ? has a smaller particle size and a more regular morphology.The small particle size can effectively shorten the diffusion path of lithium ions,thus exhibiting the best electrochemical performance.The first discharge specific capacity at 1C current density is as high as 148.5 mAh g-1.After 200 cycles,the capacity can still maintain 143.5 mAh g-1,the capacity retention was as high as 96.3%.