Síntese, caracterização e aplicações de materiais reciclados a partir de baterias íon-Li exauridas
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Data
2018-08-31
Autores
Pegoretti, Vitor Cezar Broetto
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Universidade Federal do Espírito Santo
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In this work, cobalt is recycled from a spent lithium-ion battery (LIB) to synthetize high-temperature HT-LiCoO2. In the leaching process, the cathode and anode materials are mixed with sulfuric acid and hydrogen peroxide under stirring and heating. The leaching liquor is filtrated to separate the carbon graphite anode. Cobalt hydroxide is precipitated after the addition of potassium hydroxide to the leaching solution. Cobalt hydroxide and lithium carbonate are the precursor materials for the thermal synthesis of HT LiCoO2 at 800 °C for 5 h. Raman spectroscopyconfirmedthe presence of the ??3¯??phase in HTLiCoO2.Transmission electron microscopy (TEM)analysis showed that the synthesized material has microcracks and defects.The electrochemical behavior of the synthesized material is tested by cyclic voltammetry and cycling tests. The results indicate intercalation and de-intercalation of lithium ions into and from the HT LiCoO2structure. The material presents the highest capacity value of 61.5 mAh g–1for discharge time of 4.4 h in the 4thcycle, and 32.5 mAh g–1in the 15thcycle for discharge time of 2 h. HT LiCoO2is also tested as an electrocatalyst for the oxygen evolution reaction (OER). Cyclic voltammetry and chronoamperometry tests show that the evolution of oxygen starts at 0.35 V accompanied by the formation of Co4+ions. The activation free energy of the reaction calculated using Tafel plot is 28.0 kJ mol-1and electrochemical impedance spectroscopy elucidates an equivalent circuit with a transfer charge resistance of 1.55 O, Warburg impedance of 150.3 O, and constant phase elements of 3.50 and 1.35 mF inside the pores and at the double layer, respectively.A green method was evaluated on route B. A cathodeLiCoxNiyMn1-x-yO2type form aspent lithium-ion battery was leached withmalic acid and the synthesis followed by sol–gelmethod. Three compoundswere prepared varying the synthesis time and the amount of lithium in the reaction medium. CNM10-10h material was obtained after 10 h under muffle furnace at 900 °C with Li:(Co+Ni+Mn)ratio of1.1:1.XRD with Rietveld refinementrevealed that the material is composed of64.3% Li0.31Ni0.5Mn0.5O2(??3¯??)and 35.7% Co3O4(??43¯??).SEM imagesshowedthe presence of octahedral Co3O4particles of approximately 1µmand TEM presented nanorods particles attributed to the lithiated phase. Cyclic voltammetry tests confirmed themultifunctional properties of the mixed oxide, which can be used as pseudocapacitor, catalyst,and non-enzymaticelectrochemical sensor for ascorbic acid determination. The synthesizedmaterial had a specific capacitance of 4.6 F g-1at the 1000thvoltammetric cycleat 10 mV s-1, an ascorbic acid sensitivity of 238.4 µA L mmol-1cm-2,and alinear working range of0.5–5 mmolL-1.CNM10-3h and CNM20-3h materials were obtained after 3 h under muffle furnace. The Li:(Co+Ni+Mn) ratio was 1.1:1 on the first material and 1.2:1 on the second one. XRD with Rietveld refinementrevealed that CNM10-3h material is composed by21.8% of Co3O4(??43¯??) and 78.2%of LiCo0,28Ni0,33Mn0,34O2(??3¯??).CNM20-3h is composed by 14.7 % ofCo3O4(??43¯??) and85.3 % ofLi0.94Co0.25Ni0.34Mn0.41O2(??3¯??).The electrochemical behavior of the synthesized materialswas tested by cyclic voltammetry and cycling tests. The results indicate intercalation and de-intercalation of lithium ions into and from thelithiated phase. Charge/discharge tests under C/10 rate realized on CNM10-3h and CNM20-3h presentedthe highest capacity value of 80and 119 mAh g–1onthe 1stcycle, respectively. Prolonged tests realized in 15 cycles only on CNM20-3h showed the capacity of 39,7 mAh g-1on the last cycle and a 9efficiency of 88,8%. Therefore, the recycling routes proposed in this work are efficient for the production of materials with different technological applications
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Baterias ion-Li , Reciclagem - Indústria , Materiais multifuncionais