The Preparation And Lithium Storage Performance Of LiFePO₄ Cathode Materials Recovered Based On Expired Waste Medicine Lithium Carbonate Tablets And Ferrous Sulfate Tablets

Lithium carbonate tablets and ferrous sulfate tablets are specially used as the symptomatic medicines for the clinic therapy of the bipolar disorder and iron deficiency anemia,respectively.Lithium carbonate tablets consist of the active ingredient of Li₂CO₃ and the excipient,and ferrous sulfate tablets are also composed of effective constituent FeSO₄?7H₂O and excipient.However,not all drugs can be completely consumed prior to the period of validity,so some medicines would be inevitably surplus and invalid.If secondary non-medical values in expired lithium carbonate and ferrous sulfate tablets weren't fully exploited,it may result in not only the waste of resources in expired drugs but also the pollution to the environment.As one of promising cathode materials in lithium ion battery?LIB?,LiFePO₄ has attracted much attention due to its good electrochemical performances.Li₂CO₃ and FeSO₄?7H₂O are often used as Li-source and Fe-source for synthesizing LiFePO₄ in LIB.Based on this,expired medicines of lithium carbonate and ferrous sulfate tablets were recycled in the form of LiFePO₄/C and Mg²⁺doped LiFePO₄/C via facile high temperature solid state reaction,then the electrochemical Li-storage performances were also investigated.The research contents are as follows:?1?Firstly,expired lithium carbonate tablets were recycled in the form of LiFePO₄/C via facile high temperature solid state reaction.The structure,morphology and element composition of LiFePO₄/C were characterized by XRD,SEM and EDX.The electrochemical properties and reaction mechanism of LiFePO₄/C were investigated by means of galvanostatic charge/discharge and cyclic voltammetry?CV?.The recovery rate and a simple technical-economic analysis of the recycling process were carried out.The results showed that irregular LiFePO₄/C nanoparticles were obtained by recovering,and the particle size was 400-700 nm;the discharge specific capacity could reach 147.0 mAh/g at 0.5 C,and it could maintain the reversible discharge specific capacity above 106.7 mAh/g at 2.0 C for 400 cycles,showing good electrochemical performances.The recovery rate of expired lithium carbonate was85.8%,and the results of technical-economic analysis showed that the recovery process was feasible.?2?In order to further improve the electrochemical Li-storage performances of LiFePO₄/C,expired lithium carbonate and ferrous sulfate tablets were simultaneously recycled in the form of Mg²⁺doped LiFePO₄/C,while magnesium stearate within ferrous sulfate tablets was used as magnesium source,and the effects of Mg²⁺-doping on structure and electrochemical performances of LiFePO₄ were also investigated.At the same time,the recovery rate and economic analysis were also carried out.The results showed that the Mg²⁺in the expired ferrous sulfate tablets was assuredly doped at Li site of LiFePO₄,and the doping amount of Mg²⁺was 0.51 wt%.The transformation of LiFePO₄ into good P-type semiconductor after Mg²⁺-doping may improve electron conductivity,and the decrease of the cell volume could facilitate the Li⁺diffusion.The initial discharge specific capacity of Mg²⁺doped LiFePO₄/C cathode was 155.6 mAh/g at 0.1 C,and the reversible discharge specific capacity could still deliver as high as 142.2 mAh/g at further 2 C for 500 cycles,higher than that of undoped LiFePO₄/C,indicating that the electrochemical performances of LiFePO₄/C were improved after Mg²⁺-doping.The total recovery process of expired lithium carbonate and ferrous sulfate tablets was feasible.