Unusual mixed spin-state of Co3+ in the ground state of LaSrCoO4: Combined high-pressure and high-temperature study

Haw, Shu Chih; Hu, Zhiwei; Lin, Hong Ji; Lee, J. M.; Ishii, Hirofumi; Hiraoka, Nozomu; Melendez-Sans, A.; Komarek, A. C.; Tjeng, L. H.; Chen, Kai; Luo, Chen; Radu, F.; Chen, Chien Te; Chen, Jin‐Ming

doi:10.1016/j.jallcom.2020.158050

Cited by 11 publications

(5 citation statements)

References 52 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Haw et al explored the dependence of the Co L2,3-edge XAS on the electronic structure and spin state of Co 3+ in layered perovskite LaSrCoO4 by systematically tuning the crystal-field interaction via high pressure and heating. [40] They demonstrated that the presence of shoulders on both sides of the Co L3-edge, as we observed in pristine state of Li2CoO2F (Figure 4a), indicate the existence of a mixture of high and low-spin Co +3 . As Li2CoO2F was annealed at high temperature, the shoulder at 779.2 eV vanished and gave only the presence of the high-energy shoulder, ascribed to the dominance of the low-spin configuration.…”

Section: Resultssupporting

confidence: 66%

Structural and Chemical Evolution of Highly Fluorinated Li-rich Disordered Rocksalt Oxyfluorides as a Function of Temperature

Sunariwal¹,

Kumar²,

Doğan

et al. 2023

Preprint

View full text Add to dashboard Cite

Li-rich disordered rocksalt (DRS) oxyfluorides have emerged as promising high-energy cathode materials for lithium-ion batteries. While a high level of fluorination in DRS materials offers performance advantages, it can only be achieved via mechanochemical synthesis, which poses challenges of reproducibility and scalability. The definition of relationships between fluorination and thermal stability is required to devise alternative methods that overcome these challenges. In this study, we investigated the thermal stability of three highly fluorinated Li2MO2F (M=Mn, Co, and Ni) in inert atmosphere. We utilized diffraction and spectroscopic techniques to examine changes in their electronic and chemical states up until conditions of decomposition. The analysis revealed that the materials phase-separate above 400C, at most. We also observed that heat-treated DRS materials exhibited intricate changes in local coordination and ordering compared to the pristine states. Furthermore, the heat-treated materials displayed a reduced voltage hysteresis on the electrochemical voltage profiles compared to pristine states. These results provide an in-depth understanding of the fundamental crystal chemistry of DRS materials in view of their promising role as next generation of Li-ion cathodes.

show abstract

Section: Resultssupporting

confidence: 66%

Structural and Chemical Evolution of Highly Fluorinated Li-rich Disordered Rocksalt Oxyfluorides as a Function of Temperature

Sunariwal¹,

Kumar²,

Doğan

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

“…Several studies have established the sensitivity of the Co L 3 ‐edge to spin configurations in octahedral environments associated with the presence of the low‐energy (for HS configurations) or high‐energy shoulder (for LS). They include evaluations of temperature dependence in LaCoO 3 , [ 44 ] pressure dependence in layered perovskite LaSrCoO 4 , [ 45 ] and several chemical substitutions associated with lattice distortions that can create spin instabilities. [ 46 ] In our data for the pristine state of Li 2 CoO 2 F (Figure 4a), significant shoulders were present on both sides of the main edge, indicating the existence of a mixture of high and low‐spin Co +3 .…”

Section: Resultsmentioning

confidence: 99%

Structural and Chemical Evolution of Highly Fluorinated Li‐Rich Disordered Rocksalt Oxyfluorides as a Function of Temperature

Sunariwal,

Dogan,

Roy

et al. 2023

Adv Funct Materials

View full text Add to dashboard Cite

Li‐rich disordered rocksalt (DRS) oxyfluorides have emerged as promising high‐energy cathode materials for lithium‐ion batteries. While a high level of fluorination in DRS materials offers performance advantages, it can only be achieved via mechanochemical synthesis, which poses challenges of reproducibility and scalability. The definition of relationships between fluorination and structural stability is required to devise alternative methods that overcome these challenges. In this study, the thermal evolution of three highly fluorinated phases, Li2TMO2F (TM = Mn, Co, and Ni), is investigated in an inert atmosphere. Diffraction and spectroscopic techniques are utilized to examine their electronic and chemical states up until conditions of decomposition. The analysis reveals that the materials phase‐separate above 400 °C, at most. It is also observed that heat‐treated DRS materials exhibit intricate changes in the local coordination of the metals, including their spin, and ordering compared to the pristine states. The changes upon annealing are accompanied by a modulation of the voltage profile, including reduced hysteresis, when used as electrodes. These results provide an in‐depth understanding of the fundamental crystal chemistry of DRS oxyfluorides in view of their promising role as the next generation of Li‐ion cathodes.

show abstract

“…IS Co 3+ with an electronic configuration t 2g 5 e g 1 is a Jahn–Teller active ion, and with sufficiently distorted octahedra, IS Co 3+ can gain energy to become the ground state. This very pointthat the distortion of octahedra might be an indicator for the existence of IS Co 3+ in cobaltateshas been a sparring topic. − …”

Section: Introductionmentioning

confidence: 93%

Room-Temperature Mixed Spin State of Co³⁺ in Sr₂Co_0.02Ga_0.98NbO₆ Double Perovskites: Combined NMR and EPR Studies in a Potential Inorganic Pigment

et al. 2022

View full text Add to dashboard Cite

Unusual mixed spin-state of Co3+ in the ground state of LaSrCoO4: Combined high-pressure and high-temperature study

Cited by 11 publications

References 52 publications

Structural and Chemical Evolution of Highly Fluorinated Li-rich Disordered Rocksalt Oxyfluorides as a Function of Temperature

Structural and Chemical Evolution of Highly Fluorinated Li-rich Disordered Rocksalt Oxyfluorides as a Function of Temperature

Structural and Chemical Evolution of Highly Fluorinated Li‐Rich Disordered Rocksalt Oxyfluorides as a Function of Temperature

Room-Temperature Mixed Spin State of Co³⁺ in Sr₂Co_0.02Ga_0.98NbO₆ Double Perovskites: Combined NMR and EPR Studies in a Potential Inorganic Pigment

Contact Info

Product

Resources

About

Unusual mixed spin-state of Co3+ in the ground state of LaSrCoO4: Combined high-pressure and high-temperature study

Cited by 11 publications

References 52 publications

Structural and Chemical Evolution of Highly Fluorinated Li-rich Disordered Rocksalt Oxyfluorides as a Function of Temperature

Structural and Chemical Evolution of Highly Fluorinated Li-rich Disordered Rocksalt Oxyfluorides as a Function of Temperature

Structural and Chemical Evolution of Highly Fluorinated Li‐Rich Disordered Rocksalt Oxyfluorides as a Function of Temperature

Room-Temperature Mixed Spin State of Co3+ in Sr2Co0.02Ga0.98NbO6 Double Perovskites: Combined NMR and EPR Studies in a Potential Inorganic Pigment

Contact Info

Product

Resources

About

Room-Temperature Mixed Spin State of Co³⁺ in Sr₂Co_0.02Ga_0.98NbO₆ Double Perovskites: Combined NMR and EPR Studies in a Potential Inorganic Pigment