Detection of secondary phase in NMC811(OH)2 precursor using x-ray powder diffraction and Raman spectroscopy
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Kemian tekniikan korkeakoulu |
Master's thesis
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Authors
Date
2023-12-11
Department
Major/Subject
Energy Storage
Mcode
CHEM3063
Degree programme
Master's Programme in Energy Storage
Language
en
Pages
68
Series
Abstract
Nowadays, the popularity of lithium-ion batteries (LIBs) has surged across various sectors, from consumer electronics to electric vehicles and even higher-capacity stationary energy storage. Among the different types of cathode active materials for LIBs, Ni-rich oxides, have gained prominence in LIBs technology due to their cost effectiveness and high energy density. Various dopants for Ni-rich cathode materials further enhance their electrochemical performance. In this research work, an initial investigation is carried out to explore and approximate the potential for the dopant's detection when adding various compounds to the Ni-rich precursor. This study employs the identification of the crystal structure of NMC811(OH)2 precursor and precursor mixed with compounds was investigated using X-ray diffraction (XRD) and Raman spectroscopy. To investigate the precursor more in detail, in-situ high temperature XRD (in-situ HT-XRD) was utilized to study the phase transformations and crystallization processes of the precursor during temperature increasing from 25oC to 900oC in the air atmosphere. Then, four compounds were investigated (mixing with precursor), MoO3, Al(OH)3, Zr(OH)4, and Mg(OH)2. The preliminary XRD pattern supports the NMC811(OH)2 precursor’s strong crystallinity. The precursors in-situ HT-XRD analysis reveal the development of new crystallites from nickel (Ni), manganese(Mn), and cobalt (Co) hydroxides to oxides. When precursor mix with compounds, according to research findings from XRD, for MoO3 and Al(OH)3 case, the best secondary phase detection happens when a compound is added to the precursor at a concentration of roughly 1% by weight, giving information on the compound’s doping potential. As for Raman, Ni, Mn, Co, and OH functional groups were found in the precursor. When precursor mixed with MoO3 (1% by weight), Raman peaks were strong, evident, and matched the XRD findings. However, Al(OH)3 had weak Raman signals, which cannot be detected when mixed with the precursor. For Zr(OH)4 as it has an amorphous structure and the secondary peaks were not detectable by XRD; and Mg(OH)2 XRD pattern match close to the precursor XRD, which is hard to be distinguished, so both Mg(OH)2 and Zr(OH)4 were not investigated further. A detailed characterization by using XRD, in-situ HT-XRD, and Raman spectroscopy can offer possibilities for learning about Ni-rich precursors, complex chemical interactions, phase transformation, and secondary phase detection. The knowledge gained holds the potential to serve as a valuable guide for enhancing the development of future doping Ni-rich cathode materials for LIBs.Description
Supervisor
Kallio, TanjaThesis advisor
Kong, XiangzeKeywords
NMC811(OH)2 precursor, XRD, in-situ HT-XRD, Raman spectroscopy, secondary phase