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My2-Acetone-diacetone[my3-trisÂ(trifluoroÂmethÂyl)methanoÂlato]bisÂ[my2-trisÂ(trifluoroÂmethÂyl)methanoÂlato]trilithium
The title compound, [Li3(C4F9O)3(C3H6O)3], features an open Li/O cube with an Li ion missing at one corner. Three of the four bridging O atoms of the cube carry a fluorinated tert-butyl residue, whereas the fourth is part of an acetone molÂecule. Two of the Li atoms are further bonded to a non-bridging acetone molÂecule. Two of the lithium ion coordination geometries are very distorted LiO4 tetraÂhedra; the third could be described as a very distorted LiO3 T-shape with two distant F-atom neighbours. The Li[cdots, three dots, centered]Li contact distances for the three-coordinate Li+ ion [2.608 (14) and 2.631 (12) Ã…] are much shorter that the contact distance [2.940 (13) Ã…] between the tetraÂhedrally coordinated species
Electron affinity of Li: A state-selective measurement
We have investigated the threshold of photodetachment of Li^- leading to the
formation of the residual Li atom in the state. The excited residual
atom was selectively photoionized via an intermediate Rydberg state and the
resulting Li^+ ion was detected. A collinear laser-ion beam geometry enabled
both high resolution and sensitivity to be attained. We have demonstrated the
potential of this state selective photodetachment spectroscopic method by
improving the accuracy of Li electron affinity measurements an order of
magnitude. From a fit to the Wigner law in the threshold region, we obtained a
Li electron affinity of 0.618 049(20) eV.Comment: 5 pages,6 figures,22 reference
Graphene/Li-Ion battery
Density function theory calculations were carried out to clarify storage
states of Lithium (Li) ions in graphene clusters. The adsorption energy, spin
polarization, charge distribution, electronic gap, surface curvature and dipole
momentum were calculated for each cluster. Li-ion adsorbed graphene, doped by
one Li atom is spin polarized, so there would be different gaps for different
spin polarization in electrons. Calculation results demonstrated that a smaller
cluster between each two larger clusters is preferable, because it could
improve graphene Li-ion batteries; consequently, the most proper graphene anode
structure has been proposed.Comment: 19 pages, 7 figures, 1 tabl
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Cathode chemistries and electrode parameters affecting the fast charging performance of li-ion batteries
Li-ion battery fast-charging technology plays an important role in popularizing electric vehicles (EV), which critically need a charging process that is as simple and quick as pumping fuel for conventional internal combustion engine vehicles. To ensure stable and safe fast charging of Li-ion battery, understanding the electrochemical and thermal behaviors of battery electrodes under high rate charges is crucial, since it provides insight into the limiting factors that restrict the battery from acquiring energy at high rates. In this work, charging simulations are performed on Li-ion batteries that use the LiCoO2 (LCO), LiMn2O4 (LMO), and LiFePO4 (LFP) as the cathodes. An electrochemical-thermal coupling model is first developed and experimentally validated on a 2.6Ah LCO based Li-ion battery and is then adjusted to study the LMO and LFP based batteries. LCO, LMO, and LFP based Li-ion batteries exhibited different thermal responses during charges due to their different entropy profiles, and results show that the entropy change of the LCO battery plays a positive role in alleviating its temperature rise during charges. Among the batteries, the LFP battery is difficult to be charged at high rates due to the charge transfer limitation caused by the low electrical conductivity of the LFP cathode, which, however, can be improved through doping or adding conductive additives. A parametric study is also performed by considering different electrode thicknesses and secondary particle sizes. It reveals that the concentration polarization at the electrode and particle levels can be weaken by using thin electrodes and small solid particles, respectively. These changes are helpful to mitigate the diffusion limitation and improve the performance of Li-ion batteries during high rate charges, but careful consideration should be taken when applying these changes since they can reduce the energy density of the batteries
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