Mechanism of Lithium and Cobalt Recovery from Spent Lithium-ion Batteries by Sulfation Roasting Process
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doi: 10.1007/s40242-019-0010-9
Mechanism of Lithium and Cobalt Recovery from Spent Lithium-ion Batteries by Sulfation Roasting Process YU Yueshan1, WANG Dahui1*, CHEN Huaijing2, ZHANG Xiaodong1, XU Li1 and YANG Lixin1 1. State Key Laboratory of Advance Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou 730050, P. R. China; 2. College of Science, Lanzhou University of Technology, Lanzhou 730050, P. R. China Abstract Different from the traditional pyrometallurgical recovery process of Li and Co from spent lithium-ion batteries, a new recovery method for Li and Co was established by converting LiCoO 2 into water-soluble metal sulfates by roasting a mixture of LiCoO 2 and NaHSO4·H2O. The evolution law of the mixture with increased roasting temperature was investigated by thermogravimetry-differential scanning calorimetry(TG-DSC), in situ X-ray diffraction(XRD), XRD, and X-ray photoelectron spectroscopy(XPS). The results show that the phase transition of LiCoO2 mixed with NaHSO4·H2O with increased temperature proceeded as follows: LiCoO2, NaHSO4·H2O→LiCoO2, NaHSO4→Li1‒xCoO2, LiNaSO4, Na2S2O7, Na2SO4→Li1‒xCoO2, Co3O4, LiNaSO4, Na2SO4→Co3O4, LiNaSO4. The reaction mechanism of this roasting process may be as follows: LiCoO 2+NaHSO4·H2O→1/2Li2SO4+ 1/2Na2SO4+1/3Co3O4+1/12O2+3/2H2O, Li2SO4+Na2SO4=2LiNaSO4. Keywords LiCoO2; Chemical evolution; Roasting; In situ XRD
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Introduction
Li-ion batteries(LIBs) use LiCoO2 as a cathode material and present desirable electrochemical properties, including high energy density, good cycling stability, light mass, and low self-discharge. Thus, LIBs are widely used in mobile phones, video cameras, laptops, and other portable electronics[1―4]. However, owing to the service-life limitation of LIBs, a huge number of spent LIBs are generated annually with the rapid development and upgrading of electronic devices[5]. Spent LIBs contain toxic materials, and discarding them as domestic waste or disposing them improperly can cause environmental pollution and threaten human health[6]. In addition, spent LIBs contain valuable metals, such as Li, Co, and Ni with high economic value. Thus, the recovery of spent LIBs is favorable to the alleviation of environmental pollution and shows potential economic benefits as an important secondary resource[7]. The traditional recovery of spent LIBs is performed by hydrometallurgy, pyrometallurgy, and biometallurgy. LiCoO2 can be decomposed in an aqueous solution of inorganic or organic acids. Zhu et al.[8] used H2SO4 as a leaching agent with H2O2 addition to dissolve cathode materials, and LiCoO2 was converted into CoSO4 and Li2SO4. The results show that 96.3%(mass fraction) of Co and 87.5% of Li can be dissolved in the solution. Guo et al.[9] developed HCl as a leaching agent to dissolve LiCoO2, which was converted into CoCl2 and LiCl.
The leaching recovery reached 99.4% Li at a leaching temperature of 80 °C, 3 mol/L HCl, and solid:liquid(S/L) ratio of 1:50 g/mL for 90 min. Chen et al.[10] used H3PO4 as a leaching agent w
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