Study On The Organic Acid Leaching Performance Of Valuable Metals From Waste Lithium-ion Batteries

With the wide application of lithium ion battery as a new energy in electronic equipment and power industry,a large number of waste lithium-ion batteries will be produced in the future.The treatment and disposal of waste lithium-ion batteries is one of the environmental focus issues.The content of valuable metals in the positive electrode active materials of spent lithium-ion batteries is higher than that of natural ores.Recycling valuable metals from waste lithium ions can reduce the pollution to the environment and solve the shortage of valuable metal resources such as lithium and manganese in China.Lithium iron phosphate（LFP）and lithium manganate batteries（LMO）,which are commonly used in the market,were selected as the research objects.After disassembling and obtaining the positive electrode material,the alkaline leaching test for separating the positive electrode active material was carried out,and the alkaline leaching conditions were optimized.After calcining the positive electrode active material at high temperature,citric acid and glycine were used as leaching agents,and the influence of acid leaching conditions on the leaching of metal Li and Mn from the positive electrode active material was analyzed,and the acid leaching conditions were optimized.The leaching kinetic model fitting and X-ray diffraction were used（XRD）characterization and other means were used to analyze the reaction law of organic acid leaching of valuable metals and explore the reaction mechanism.The recovery conditions of valuable metals were optimized by precipitation of Mn and Li in the leaching solution with KMnO₄ solution and Na₃PO₄ solution.Alkali leaching test showed that 2 mol·L^-1 NaOH solution can effectively leaching aluminum foil.When the reaction time of positive active material of LFP and LMO battery is 45 and 60 min respectively,the leaching rates of metal Al are 96.91%and96.37%,respectively.The acid leaching test shows that under the condition of citric acid and glycine concentration of 1.5 mol·L^-1,solid-liquid ratio of 20 g·L^-1,adding 7 vol.%H₂O₂solution,the reaction temperature is 60℃,and leaching for 60 min.The metals Li and Mn in the positive electrode active material of the electrode can be effectively leached into the solution,and the metal Fe remains in the residue after leaching in the form of FePO₄ precipitation.The leaching rates of citric acid and glycine from the positive electrode active material of LFP battery were 96.07%and 92.62%respectively;the leaching rates of citric acid and glycine from the positive electrode active material of LMO battery were 96.70%and 93.25%.The leaching rates of leaching metal Mn were94.25%and 92.98%,respectively.The fitting results of the acid leaching kinetic equations show that the process of leaching the metals Li and Mn in the positive electrode active materials of LFP and LMO batteries by organic acids conforms to the interface chemical reaction kinetic model（R²>0.990）.The apparent activation energy of Li and Mn leaching reaction calculated by Arrhenius formula is more than 20 kJ·mol^-1,which shows that the leaching reaction accords with the interface chemical reaction model.XRD characterization analysis shows that the main components of the LFP and LMO positive electrode active materials obtained after alkaline leaching are lithium iron phosphate,lithium manganate and graphite;after calcination at 600℃,the LFP and LMO battery positive electrodes The content of graphite in the active material is reduced;the main component of the positive electrode active material residue of the LFP battery after acid leaching is FePO₄,and the content of metal Mn in the lithium manganate battery is reduced.Valuable metal recovery test shows that the use of KMnO₄ and Na₃PO₄ solution can effectively recover the Mn²⁺and Li⁺ions in the leachate in the form of MnO₂ and Li₃PO₄ precipitation.When recovering Mn²⁺ions,the pH value of the leaching solution was adjusted to 2.0,the[MnO₄-]:[Mn²⁺]concentration ratio was 1.2:1,and the reaction was performed at 85℃for 60 min.The recovery rate of metal Mn was95.02%.When recovering Li⁺ions,adjust the pH value of the leaching solution to 7.5,[PO₄^3-]:[Li⁺]concentration ratio is 1.2:1,and the leached solution of LFP and LMO battery reacted at 90℃and 85℃for 60 min,and the recovery of metal Li was 94.23%and 95.29%,respectively.Economic evaluation shows that,based on the recovery effect of the valuable metal organic acid test,it is estimated that each ton of LFP battery can obtain about 89kg of Li₃PO₄ and about 320 kg of FePO₄,and can obtain economic profit of about CNY 8041.43-9025.43.LMO battery can get about 105 kg of Li₃PO₄ and about 450kg of MnO₂ per ton of lithium manganate battery,and can obtain economic profit of about CNY 2523.43-3107.43.In summary,this study analyzed the effect of acid leaching conditions on the recovery of valuable metals in the positive active materials of waste LFP and LMO batteries through the acid leaching test of citric acid and glycine.The leaching mechanism provides scientific basis and technical support for the resourceful utilization of waste lithium-ion batteries.