다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

The Na-ion battery is currently the focus of much research interest due to its cost advantages and the relative abundance of sodium as compared to lithium. Olivine NaMPO4 (M = Fe, Fe0.5Mn0.5, Mn) and layered Na2FePO4F are interesting materials that have been reported recently as attractive positive electrodes. Here, we report their Na-ion conduction behavior and intrinsic defect properties using atomistic simulation methods. In the olivines, Na ion migration is essentially restricted to the [010] direction along a curved trajectory, similar to that of LiMPO4, but with a lower migration energy (0.3 eV). However, Na/M antisite defects are also predicted to have a lower formation energy: the higher probability of tunnel occupation with a relatively immobile M2+ cation – along with a greater volume change on redox cycling – contributes to the poor electrochemical performance of the Na-olivine. Na+ ion conduction in Na2FePO4F is predicted to be two-dimensional (2D) in the interlayer plane with a similar low activation energy. The antisite formation energy is slightly higher; furthermore, antisite occupation would not be predicted to impede transport significantly owing to the 2D pathway. This factor, along with the much lower volume change on redox cycling, is undoubtedly responsible for the better electrochemical performance of the layered structure. Where volume change and structural effects do not incur impediments, Na-ion materials may present significant advantages over their Li counterparts.

Na-ion mobility in layered Na2FePO4F and olivine Na[Fe,Mn]PO4

Metal oxides and polysaccharides: an efficient hybrid association for materials chemistry

LiNi0.5-xP2xMn1.5-xO4 (x = 0, 0.005, 0.01, and 0.02) submicrograins in regular octahedral shape with merely {111} surface facets and truncated octahedral shape with both {111} and {100} surface planes were obtained by the solid-state reaction method. The effect of doping P on ions arrangement, grain morphology, and the electrochemical performance of lithium nickel manganese oxide was investigated. The characterizations of X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), and selected area electron diffraction (SAED) confirm more Mn3+ ions in the structure to enhance the cationic disorder degree of LiNi0.5Mn1.5O4 after P-doping. Comparing the LiNi0.5Mn1.5O4 and LiNi0.495P0.01Mn1.495O4 samples both with regular octahedral morpology, their electrochemical performance could be remarkably improved by more disordered transition metal ions arrangement leading to higher conductivity of Li-ions and electrons. However, when the amount of P-doping further increased, the rate and cycle ability o...

Impact of P-Doped in Spinel LiNi0.5Mn1.5O4 on Degree of Disorder, Grain Morphology, and Electrochemical Performance

Crystal structure analysis and first principle investigation of F doping in LiFePO4

Recent developments of Na4M3(PO4)2(P2O7) as the cathode material for alkaline-ion rechargeable batteries: challenges and outlook

The influence of fluorine doping on the structural and electrical properties of the LiFePO4 powder

Effects of fluorination on the structure, magnetic and electrochemical properties of the P2-type NaxCoO2 powder

Structural study of monoclinic Li2FeSiO4 by X-ray diffraction and Mössbauer spectroscopy

Miloš Milović

Papers

Crystal structure analysis and first principle investigation of F doping in LiFePO4

Recent developments of Na4M3(PO4)2(P2O7) as the cathode material for alkaline-ion rechargeable batteries: challenges and outlook

The influence of fluorine doping on the structural and electrical properties of the LiFePO4 powder

Effects of fluorination on the structure, magnetic and electrochemical properties of the P2-type NaxCoO2 powder

Structural study of monoclinic Li2FeSiO4 by X-ray diffraction and Mössbauer spectroscopy