Because of its high specific capacity, silicon is regarded as the most promising candidate to be incrementally added to graphite‐based negative electrodes in lithium‐ion batteries. However, silicon suffers from significant volume changes upon (de‐)lithiation leading to continuous re‐formation of the solid electrolyte interphase (SEI) and ongoing active lithium losses. One prominent approach to compensate for active lithium losses is pre‐lithiation. Here, the “contact pre‐lithiation” of silicon/graphite (Si/Gr) negative electrodes in direct contact with passivated Li metal powder (PLMP) is studied, focusing on the pre‐lithiation mechanism in “dry state” and after electrolyte addition. PLMP is pressed onto the electrode surface to precisely adjust the degree of pre‐lithiation (25%, 50%, and 75%). By in situ XRD and ex situ 7Li NMR studies, it is proven that significant lithiation of Si/Gr electrodes occurs by direct contact to Li metal, that is, without electrolyte. After electrolyte addition, de‐lithiation of silicon and graphite is confirmed, resulting in SEI formation. The amount of Li metal highly impacts the presence and durability of the LixC and LixSi phases. Finally, the challenges for homogeneous pre‐lithiation and SEI formation are identified, and the impact of electrolyte addition is assessed by analysis of the lateral and in‐depth lithium distribution within the Si/Gr electrode.
Light-responsive modulation of the longitudinal (T1) and transversal (T2*) relaxation times of a fluorinated cyclodextrin has been achieved by host guest complexation with arylazopyrazole-modified metal complexes in aqueous solution. This...
Developmento fh igh-performance photocatalysts for the conversion of amines is of great importance, but has remained ac hallenging task. Here, ab is-anthracene fused porphyrin (AFP)w as synthesized in ah igh yield by af acile synthetic protocol, which involves aS uzuki coupling for the conjugation of two anthracene groups with ap orphyrin ring, followed by oxidative cyclodehydrogenation.W hen servinga saphotocatalyst, AFP exhibitsa no utstanding photocatalytic performance for the visible-light-induced aerobic oxidation of amines to iminesa tambient conditions. Density functional theory calculationsr evealed that the low energy band gap, caused by the large planar and p-extended porphyrins tructure of AFP,c ontributed to its high photocatalytic performance.
The monomeric aluminum hydrazide iBu 2 Al-N(C 10 H 15)(NC 5 H 10) (1) features a strained AlN 2 ring and is an efficient active Lewis pair. It reacted with 2,3-diphenyl-2-cyclopropen-1-one by insertion of the C=O group into an Al-N bond, cleavage of the C 3 ring and formation of an AlOC 3 heterocycle (2). Diacetyl, Me(O)C-C(O)Me, and 1 afforded by insertion of keto groups into both Al-N bonds a heterocyclic α-keto-hemihydrazinal coordinated to aluminum (3). 3 contains fused AlO 2 C 2 and C 2 N 2 heterocycles. In an unexpected reaction,
Methods for the detection of reactive intermediates such as transient radicals are important in organic chemistry, polymer chemistry, biology or medicine. Along these lines we recently reported that 1,5-diphenyl-6-oxo verdazyl radicals can be used as fluorescent spin sensors. In situ generated C-centered radicals are efficiently trapped by the verdazyls, which in turn undergo transformation from a paramagnetic non-fluorescent state to a diamagnetic fluorescent state. Whereas the N-phenyl substituent in the spin probes is of high importance for obtaining profluorescent behavior, the effect of the C(3)-substituent has not been investigated to date. We herein present the synthesis and characterization of various 1,5-diphenyl-6-oxo-verdazyl radicals bearing differently hybridized C-substituents at the C(3) position. Steady-state and time-resolved fluorescence spectroscopy in solution and in the solid state along with time-dependent density functional theory (TDDFT) calculations reveal that a C(3)-aryl substituent is crucial for obtaining fluorescence after spin trapping. In addition, it is shown that the emission wavelength of the C(3)-aryl substituted verdazyl derivatives can be tuned by selective destabilization of the HOMO and the LUMO.
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