Mg²⁺-doped LiFePO₄/C cathode from expired lithium carbonate and ferrous sulfate tablets

The wide application and oversupply of various medicines are inevitably accompanied by the production of massive amounts of expired medicines, which can trigger the environmental contamination and waste of resources if these are not reasonably managed. For this reason, the efforts were made to recycle two expired medicines (lithium carbonate (Li₂CO₃) and ferrous sulfate (FeSO₄) tablets) simultaneously into magnesium ion-doped lithium iron phosphate (LiFePO₄; LFP)/carbon (C) powders through a facile high-temperature solid-state reaction. In addition, the economic feasibility was analyzed and discussed. The results suggested that 0·51 wt% magnesium ions were successfully doped into the lithium (Li) site of LFP/carbon, and the corresponding molecular formula was Li_0·92Mg_0·04FePO₄/C, which resulted in the double effects: a decrease in the unit cell volume and an increase in the electronic conductivity. Furthermore, the magnesium ion/LFP/carbon cathode also exhibited better electrochemical lithium-storage performance compared with the undoped LFP/carbon cathode, indicating high application feasibility in lithium-ion batteries. Additionally, the recycling process was economically profitable, which would stimulate the development of the circular economy of waste expired medicines and lithium-ion batteries.