Hydrometallurgical recovery of lithium carbonate and iron phosphate from blended cathode materials of spent lithium-ion battery

The recycling of cathode materials from spent lithium-ion battery has attracted extensive attention,but few research have focused on spent blended cathode materials.In reality,the blended materials of lithium iron phosphate and ternary are widely used in electric vehicles,so it is critical to design an effective recycling technique.In this study,an efficient method for recovering Li and Fe from the blended cathode materials of spent LiFePO_(4)and LiNi_(x)Co_(y)Mn_(1-x-y)O_(2)batteries is proposed.First,87%A1 was removed by alkali leaching.Then,91.65%Li,72.08%Ni,64.6%Co and 71.66%Mn were further separated by selective leaching with H_(2)SO_(4)and H_(2)O_(2).Li,Ni,Co and Mn in solution were recovered in the form of Li_(2)CO_(3)and hydroxide respectively.Subsequently,98.38%Fe was leached from the residue by two stage process,and it is recovered as FePO_(4)·2H_(2)O with a purity of 99.5%by precipitation.Fe and P were present in FePO_(4)·2H_(2)O in amounts of 28.34%and 15.98%,respectively.Additionally,the drift and control of various components were discussed,and cost-benefit analysis was used to assess the feasibility of potential application.

Thermal stability of LiFePO_4/C-LiMn_2O_4 blended cathode materials

Safety is important to lithium ion battery materials. The thermal stability of LiFePOa/C-LiMn204 blended cathode materials is characterized by using TG, XRD, and SEM etc. The results show that LiFePO4/C-LiMn2O4 possesses a worse thermal stability than pure spinel LiMn2O4 and pure olivine LiFePO4/C. When LiFePO4/C-LiMn2O4 blended cathode materials are sintered at 500℃ under Ar atmosphere, the sintered cathode materials emit O2, and appear impurity phases （Li3PO4, Fe2O3, Mn3O4）. It is deduced that some chemical reactions take place between different materials, which leads to a worse discharge specific capacity. LiFePO4/C-LiMn2O4 blended cathode materials, therefore, need to be managed and controlled strictly for the sake of ther- mal stability and safety.

Electrochemical Performance of LiMn2O4/LiFePO4 Blend Cathodes for Lithium Ion Batteries

A series of LiMn2O4/LiFePO4 blend cathodes was prepared by hand milling and ball milling in order to compensate the disadvantage of spinel LiMnaO4 and olivine LiFePO4. The morphologies of the blends were studied by scanning electron microscopy, and their electrochemical properties were studied by charge-discharge cycling, cyclic voltarnmetry and electrochemical impedance spectroscopy. It is easy to obtain uniform LiMn2Oa/LiFePO4 blends by the hand milling technique, while significant particle agglomeration is caused by the ball milling technique. When the LiMn2O4：LiFePO4 mass ratio is 1：1, the nano-sized LiFePO4 powders not only uniformly cover the micron-sized LiMn2O4 particles but also effectively fill in the cavities of the LiMn2O4 space. Such morphology offers a good electrical contact and a high tap density, which leads to a high discharge capacity and good cycle stability.

Synergetic effects of blended materials for Lithium-ion batteries

LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2, LiMn_2O_4 and LiCoO_2 are paired to make the blended materials for the cathode of lithium-ion batteries. The factors impacting on the characteristics of blended materials are studied using constant current charge/discharge measurement and electrochemical impedance spectroscopy. The results show that the three pairs of blended materials exhibit very different synergetic effects in high C-rate discharging. The mechanism of particle synergetic effect has a physical root on the compensating material property of blending components, which fundamentally correlates with their similarity and difference in crystalline and electronic structures. The AC impedance show the obvious changes that alternate the high C-rate performance, due to reduced particle impedance in blended materials. The pairs of LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2-LiMn_2O and LiCoO_2-LiMn_2O_4 present obvious increases in high C-rate reversible capacities than does the pair LiCoO_2-LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2.