Synthesis, characterization and applications of recycled materials from spent Li ion batteries

Name: VITOR CEZAR BROETTO PEGORETTI
Type: PhD thesis
Publication date: 31/08/2018
Advisor:

Name	Role
MARCOS BENEDITO JOSÉ GERALDO DE FREITAS	Advisor *

Examining board:

Name	Role
DEMETRIUS PROFETI	External Examiner *
LUIZ CARLOS PIMENTEL ALMEIDA	External Examiner *
MARCOS BENEDITO JOSÉ GERALDO DE FREITAS	Advisor *
MARIA DE FÁTIMA FONTES LELIS	Internal Examiner *
RAFAEL DE QUEIROZ FERREIRA	Internal Examiner *

Summary: 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 spectroscopy confirmed the presence of the R3 ̅m phase in HT LiCoO2. 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 LiCoO2 structure. The material presents the highest capacity value of 61.5 mAh g–1 for discharge time of 4.4 h in the 4th cycle, and 32.5 mAh g–1 in the 15th cycle for discharge time of 2 h. HT LiCoO2 is 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-1 and electrochemical impedance spectroscopy elucidates an equivalent circuit with a transfer charge resistance of 1.55 Ω, Warburg impedance of 150.3 Ω, 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 cathode LiCoxNiyMn1-x-yO2 type form a spent lithium-ion battery was leached with malic acid and the synthesis followed by sol–gel method. Three compounds were 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 of 1.1:1. XRD with Rietveld refinement revealed that the material is composed of 64.3% Li0.31Ni0.5Mn0.5O2 (R3 ̅m) and 35.7% Co3O4 (F43 ̅m). SEM images showed the presence of octahedral Co3O4 particles of approximately 1 µm and TEM presented nanorods particles attributed to the lithiated phase. Cyclic voltammetry tests confirmed the multifunctional properties of the mixed oxide, which can be used as pseudocapacitor, catalyst, and non-enzymatic electrochemical sensor for ascorbic acid determination. The synthesized material had a specific capacitance of 4.6 F g−1 at the 1000th voltammetric cycle at 10 mV s−1, an ascorbic acid sensitivity of 238.4 µA L mmol−1 cm−2, and a linear working range of 0.5–5 mmol L−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 refinement revealed that CNM10-3h material is composed by 21.8% of Co3O4 (F43 ̅m) and 78.2% of LiCo0,28Ni0,33Mn0,34O2 (R3 ̅m). CNM20-3h is composed by 14.7 % of Co3O4 (F43 ̅m) and 85.3 % of Li0.94Co0.25Ni0.34Mn0.41O2 (R3 ̅m). The electrochemical behavior of the synthesized materials was tested by cyclic voltammetry and cycling tests. The results indicate intercalation and de-intercalation of lithium ions into and from the lithiated phase. Charge/discharge tests under C/10 rate realized on CNM10-3h and CNM20-3h presented the highest capacity value of 80 and 119 mAh g–1 on the 1st cycle, respectively. Prolonged tests realized in 15 cycles only on CNM20-3h showed the capacity of 39,7 mAh g-1 on the last cycle and a efficiency 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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