Study On Recovery Technology Of Valuable Metals From Cathode Material Of Spent Ternary Lithium-ion Batteries

Ternary lithium-ion batteries have been vigorously promoted in the field of new energy vehicles due to their excellent overall performance,and the rapid growth of battery production and sale has brought about a proliferation of spent lithium-ion batteries.Since the cathode material of spent lithium-ion batteries contains various valuable metal elements,the recovery of these metal elements will produce multiple environmental and economic benefits.In this paper,the cathode material of spent lithium-ion batteries was used as research object,and the key influencing factors on the wet leaching and recycling process of cathode materials were systematically studied.The main contents and research results are as follows:（1）The sulfuric acid-tea polyphenol leaching system was constructed with natural product of tea polyphenol as the innovative reducing agent for the reductive acid leaching of cathode materials of spent ternary lithium-ion battery.The optimal leaching conditions were obtained as follows:C_（H2SO4）=1.0 mol/L,solid-liquid ratio of cathode materials=30 g/L,solid-liquid ratio of tea polyphenol=3.5 g/L,T=60℃,and t=60 min.Under these conditions,the leaching efficiencies of lithium,nickel,cobalt and manganese were 99.54%,98.88%,99.37%and 98.45%,respectively.After leaching,a stepwise precipitation method was used to separate and recover the valuable metals from the leachate,and（NH₄）₂S₂O₈,DMG,H₂C₂O₄ and Na₂CO₃ were used as the precipitation agents to obtain high value-added precipitation products of four metal ions.The overall recovery efficiencies of lithium,nickel,cobalt and manganese were 67.74%,93.63%,94.97%and 98.54%,respectively.The one-stage precipitation efficiency of lithium was 70.15%and the purity of the obtained lithium carbonate product reached up to 99.50%.（2）Since the cathode material of lithium iron phosphate battery has the reductive characteristic in acidic environment,the sulfuric acid-lithium iron phosphate leaching system was constructed with the lithium iron phosphate as the reducing agent for wet leaching of cathode material of ternary lithium-ion battery.It not only avoids the introduction of additional reducing agent,but also realizes the joint recovery of cathode materials of lithium iron phosphate and ternary lithium-ion batteries.The optimal leaching conditions were obtained as follows:C（7）_{H 2S O4}（8）=0.9 mol/L,molar ratio of Li Fe PO4 to SNCM523=1.3,T=70℃,solid-liquid ratio=100 g/L and t=180 min.Under these conditions,the leaching efficiencies of lithium,nickel,cobalt,manganese and iron were 99.54%,93.26%,96.28%,97.16%and 28.37%,respectively.After adjusting the p H of the leachate to remove impurities like iron ion,the oxalate co-precipitation method was used to co-precipitate nickel,cobalt and manganese ions in the leachate to prepare ternary precursor of Ni_0.5Co_0.2Mn_0.3C₂O₄.The residual liquid was lithium-rich solution.The optimum process conditions were investigated and obtained as follows:molar amount of ammonium oxalate=0.4 mol/L,reaction time=60 min,and reaction temperature=40°C.After co-precipitation,the leaching efficiencies of lithium,nickel,cobalt and manganese changed to95.76%,2.42%,0.01%and 0.07%,respectively.The lithium-rich solution was chemically precipitated by adding saturated sodium carbonate solution to obtain lithium carbonate with a primary precipitation efficiency of 82.78%and purity of 99.7%.The repreparation of ternary cathode materials was realized by high temperature solid state method with precipitation products of the co-precipitation method and lithium carbonate.The optimum process conditions were obtained as follows:addition of 1.05 times of the theoretical amount of Li₂CO₃,T=850°C and t=16 h.The cathode materials regenerated under these conditions were used to prepare button batteries,and the first discharge specific capacity at 25°C and 1 C multiplicity reached 133.6 m Ah/g,demonstrating good cycling stability.In summary,two complete recycling process routes of cathode materials of spent ternary lithium-ion batteries were constructed in this paper,while the recovery process of various metal ions in the leachate were systematically explored.The proposed process routes have the advantages of innovative and highly operational,providing a solid theoretical basis and technical support for the efficient and clean recycling of spent lithium-ion batteries.