Recycling And Reusing Of Cathode Materials From Spent Lithium Ion Batteries

Lithium-ion batteries are widely used in portable electronic devices and new energy vehicles due to their high specific energy,high safety performance,and environmental protection,which inevitably results in a large number of spent lithium-ion batteries.Therefore,research on the recycling of high-value metals in spent lithium-ion batteries has become a hot issue.In this dissertation,the cathode materials of spent lithium-ion battery from Guizhou Zhenhua E-chem Co.Ltd.were dissolved by using SO₂The purification and separation process of the solution was studied,and LiNi_0.33Co_0.33Mn_0.33O₂ cathode material was prepared using the recycled product.The main results are summarized as following:1)The effects of S/L ratio,SO₂ gas flow rate,dissolving system,reaction time and temperature on the dissolution process of spent cathode materials were investigated.The results showed that the dissolution ratio of Li、Co、Mn and Ni was 98.1%、98.0%、97.8%and 98.2%respectively,when dissolved in SO₂/H₂SO₄/H₂O₂ system for 60 minutes at 80°C,at the S/L ratio and SO₂ gas flow rate of 50 g/L and 0.4 L/min.2)Iron ions in the solution were removed by oxidation neutralization method,the removal efficiency of iron reaches 98.2%.Al and Cu ions were removed by precipitation separation,and the removal efficiency of aluminum and copper reach 96.1%and 99.7%respectively.Lithium was recovered using（NH₄）₃PO₄,and the recycling ratio reached 84%.3)The layered LiNi_0.33Co_0.33Mn_0.33O₂ cathode material was prepared by using recycled materials,and its electrochemical performance were tested.The results showed that the initial charge and discharge capacity of the as-prepared material was 154.9/121.2 mAh·g^-1 at a current density of20 mA·g^-11 between 3.0-4.35 V,and a capacity retention ratio is 100%after 40 cycles.Tributyl（methoxymethyl）phosphoniumbis（trifluoromethylsulfonyl）i-mide(P_444（1O1）TFSI)and tributyl（2-methoxyethyl）phosphoniumbis（triflu-oromethylsulfonyl）imide(P_444（2O1）TFSI)were synthesized,and their influ-ences on the thermostability of organic electrolyte and electrochemical properties of LiCoO₂ electrode were investigated by thermogravimetric analysis and electrochemical methods.The results showed that the phosphoniumionic liquids could improve the thermostability of organic electrolyte,and the size of the cationic group had a larger influence on the electrochemical properties of LiCoO₂ electrode.The initial discharge capacity for the electrolyte with P_444（2O1）TFSI（volume ratio:15%）was164.6mAh·g^-1at the rate of 150 mA·g^-1and 3.0⁴.35 V.The discharge capacity upon 100 cycles was 144.7mAh·g^-1,and the capacity retention was 89.9%.The cycle performance was much better than that in conventional organic electrolytes.