3 research outputs found
Standard for Synthesis of Customized Peptides by Non-Ribosomal Peptide Synthetases
The purpose of this RFC is to introduce a standardized framework for the engineering of customizable non-ribosomal peptide synthetases (NRPS) and their application for in vivo and in vitro synthesis of short non-ribosomal peptides (NRPs) of user-defined sequence and structure
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Probing Jahn-Teller distortions and antisite defects in LiNiO2 with 7Li NMR spectroscopy and Density Functional Theory
The long- and local-range structure and electronic properties of the high-voltage lithium-ion cathode material for Li-ion batteries, LiNiO2, remain widely debated, as are the degradation phenomena at high states of delithiation, which limit the more widespread use of this material. In particular, the local structural environment and the role of Jahn-Teller distortions are unclear, as are the interplay of distortions and point defects, and their influence on cycling behaviour. Here, we use ex-situ 7Li NMR measurements in combination with density functional theory (DFT) calculations to examine Jahn-Teller distortions and anti-site defects in LiNiO2. We calculate the 7Li Fermi contact shifts for the Jahn-Teller distorted and undistorted structures,
the experimental 7Li room temperature spectrum being ascribed to an appropriately weighted
time-average of the rapidly fluctuating structure comprising, collinear, zigzag and undistorted domains. The 7Li NMR spectra are sensitive to the nature and distribution of anti-site defects, and in combination with DFT calculations of different configurations, we show that the 7Li resonance at approximately -89 ppm is characteristic of separated Li – Ni antisite defects, these and the anti-site defect with Li in next-nearest Li-Ni neighbour configurations accounting for approximately 1/3 and 2/3, respectively of the total anti-site defect concentrations at room temperature in the pristine material. Via ex-situ 7Li MAS NMR, X-ray diffraction and electrochemical experiments, we identify the 7
Li spectral signatures of the different crystallographic phases on delithiation. The results imply fast Li-ion dynamics in the monoclinic phase and indicate that the hexagonal H3 phase near the end of charge is largely devoid of Li.This work was supported by the Faraday Institution degradation project (FIRG011, FIRG020). This project has received funding from the European Union’s Horizon 2020
research and innovation program under grant agreement No 957189 (BIGMAP). The project
is part of BATTERY 2030+, the large-scale European research initiative for inventing the sustainable batteries of the future, funded by the European Union's Horizon 2020 research
and innovation program under Grant Agreement No. 957213. A.R.G.-S. gratefully acknowledges funding from the German National Academy of Sciences Leopoldina. We thank Teresa Insinna for fruitful discussions. Generous computing resources were provided by the Sulis HPC service (EP/T022108/1)
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Probing Jahn-Teller Distortions and Antisite Defects in LiNiO2 with 7Li NMR Spectroscopy and Density Functional Theory.
Publication status: PublishedThe long- and local-range structure and electronic properties of the high-voltage lithium-ion cathode material for Li-ion batteries, LiNiO2, remain widely debated, as are the degradation phenomena at high states of delithiation, limiting the more widespread use of this material. In particular, the local structural environment and the role of Jahn-Teller distortions are unclear, as are the interplay of distortions and point defects and their influence on cycling behavior. Here, we use ex situ7Li NMR measurements in combination with density functional theory (DFT) calculations to examine Jahn-Teller distortions and antisite defects in LiNiO2. We calculate the 7Li Fermi contact shifts for the Jahn-Teller distorted and undistorted structures, the experimental 7Li room-temperature spectrum being ascribed to an appropriately weighted time average of the rapidly fluctuating structure comprising collinear, zigzag, and undistorted domains. The 7Li NMR spectra are sensitive to the nature and distribution of antisite defects, and in combination with DFT calculations of different configurations, we show that the 7Li resonance at approximately -87 ppm is characteristic of a subset of Li-Ni antisite defects, and more specifically, a Li+ ion in the Ni layer that does not have an associated Ni ion in the Li layer in its 2nd cation coordination shell. Via ex situ7Li MAS NMR, X-ray diffraction, and electrochemical experiments, we identify the 7Li spectral signatures of the different crystallographic phases on delithiation. The results imply fast Li-ion dynamics in the monoclinic phase and indicate that the hexagonal H3 phase near the end of charge is largely devoid of Li.This work was supported by the Faraday Institution degradation project (FIRG011, FIRG020). This project has received funding from the European Union’s Horizon 2020
research and innovation program under grant agreement No 957189 (BIGMAP). The project
is part of BATTERY 2030+, the large-scale European research initiative for inventing the sustainable batteries of the future, funded by the European Union's Horizon 2020 research
and innovation program under Grant Agreement No. 957213. A.R.G.-S. gratefully acknowledges funding from the German National Academy of Sciences Leopoldina. We thank Teresa Insinna for fruitful discussions. Generous computing resources were provided by the Sulis HPC service (EP/T022108/1)