Journal
FRONTIERS IN CHEMISTRY
Volume 10, Issue -, Pages -Publisher
FRONTIERS MEDIA SA
DOI: 10.3389/fchem.2022.1019493
Keywords
spent lithium-ion batteries; cathode material; hydrogen reduction; Ni-Co alloy; reaction mechanism; kinetics
Categories
Funding
- Hunan Natural Science Foundation
- National Natural Science Foundation of China
- Hunan Key Research and Development Program
- [2021JJ30854]
- [51904350]
- [51922108]
- [51874371]
- [2020SK2005]
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Hydrogen reduction is a promising method for recycling lithium-ion battery cathode materials, but its reaction mechanism and kinetics remain unclear. This study conducted experiments to evaluate the temperature dependence of hydrogen reduction kinetics and characterized the reduction products using XRD and SEM. The results showed that hydrogen reduction could be divided into three stages and the temperature had a significant impact on the reduction rate.
Hydrogen reduction is becoming a promising method for recycling lithium-ion battery cathode materials. However, the reaction mechanism and kinetics during hydrogen reduction are unclear, requiring further investigation. Therefore, non-isothermal and isothermal reduction experiments were conducted to evaluate the temperature dependence of the hydrogen reduction kinetics using simultaneous thermogravimetric and differential thermal analysis equipped with mass spectrometry. XRD and SEM were used to characterize the reduction products to understand the underlying reduction mechanisms. The hydrogen reduction profile could be divided into three main stages: decomposition of cathode materials, reduction of the resultant nickel and cobalt oxides, and reduction of LiMnO2 and residual nickel and cobalt oxides. The hydrogen reduction rate increased with increasing temperature, and 800 ? was the optimum temperature for separating the magnetic Ni-Co alloy from the non-magnetic manganese oxide particles. The apparent activation energy for the isothermal tests in the range of 500-700 ? was 84.86 kJ/mol, and the rate-controlling step was the inward diffusion of H-2(g) within each particle. There was an downward progression of the reduction through the material bed for the isothermal tests in the range of 700-900 ?, with an apparent activation energy of 51.82 kJ/mol.
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