| 1. |
- Baur, Christian, et al.
(författare)
-
Improved cycling stability in high-capacity Li-rich vanadium containing disordered rock salt oxyfluoride cathodes
- 2019
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 7:37, s. 21244-21253
-
Tidskriftsartikel (refereegranskat)abstract
- Lithium-rich transition metal disordered rock salt (DRS) oxyfluorides have the potential to lessen one large bottleneck for lithium ion batteries by improving the cathode capacity. However, irreversible reactions at the electrode/electrolyte interface have so far led to fast capacity fading during electrochemical cycling. Here, we report the synthesis of two new Li-rich transition metal oxyfluorides Li2V0.5Ti0.5O2F and Li2V0.5Fe0.5O2F using the mechanochemical ball milling procedure. Both materials show substantially improved cycling stability compared to Li2VO2F. Rietveld refinements of synchrotron X-ray diffraction patterns reveal the DRS structure of the materials. Based on density functional theory (DFT) calculations, we demonstrate that substitution of V3+ with Ti3+ and Fe3+ favors disordering of the mixed metastable DRS oxyfluoride phase. Hard X-ray photoelectron spectroscopy shows that the substitution stabilizes the active material electrode particle surface and increases the reversibility of the V3+/V5+ redox couple. This work presents a strategy for stabilization of the DRS structure leading to improved electrochemical cyclability of the materials.
|
|
| 2. |
- Hood, D W, et al.
(författare)
-
Genetic basis for expression of the major globotetraose-containing lipopolysaccharide from H-influenzae strain Rd (RM118)
- 2001
-
Ingår i: Glycobiology. - : Oxford University Press (OUP). - 0959-6658 .- 1460-2423. ; 11:11, s. 957-967
-
Tidskriftsartikel (refereegranskat)abstract
- A genetic basis for the biosynthetic assembly of the globotetraose containing lipopolysaccharide (LPS) of Haemophilus influenzae strain RM118 (Rd) was determined by structural analysis of LPS derived from mutant strains. We have previously shown that the parent strain RM118 elaborates a population of LPS molecules made up of a series of related glycoforms differing in the degree of oligosaccharide chain extension from the distal heptose residue of a conserved phosphorylated inner-core element, L-alpha -D-Hepp-(1-->2)-L-alpha -D-Hepp-(1-->3)-[beta -D-Glcp-(1-->4)-]-L-alpha -D-Hepp-(1-->5)-alpha -Kdo. The fully extended LPS glycoform expresses the globotetraose structure, beta -D-GalpNAc-(1-->3)-alpha -D-Galp(1-->4)-beta -D-Galp-(1-->4)-beta -D-Glcp. A fingerprinting strategy was employed to establish the structure of LPS from strains mutated in putative glycosyltransferase genes compared to the parent strain. This involved glycose and linkage analysis on intact LPS samples and analysis of O-deacylated LPS samples by electrospray ionization mass spectrometry and 1D H-1-nuclear magnetic resonance spectroscopy. Four genes, lpsA, lic2A, lgtC, and lgtD, were required for sequential addition of the glycoses to the terminal inner-core heptose to give the globotetraose structure. lgtC and lgtD were shown to encode glycosyltransferases by enzymatic assays with synthetic acceptor molecules. This is the first genetic blueprint determined for H. influenzae LPS oligosaccharide biosynthesis, identifying genes Involved in the addition of each glycose residue.
|
|
