The large abundance of Na combined with the feasibility of Na-based insertion compounds, such as Na 3 V 2 (PO 4 ) 2 F 3 , makes the Na-ion battery an attractive technology compared with Li-ion battery for a few applications. Nonetheless, one identified limitation of the Na 3 V 2 (PO 4 ) 2 F 3 /HC system is its poor long-term cycling performance at elevated temperature, hence the sorely need to screen the proper electrolyte formulation. Here, we report a thorough survey aiming to assess the pros and cons of cyclic vs. linear carbonates with respect to the performances of Na 3 V 2 (PO 4 ) 2 F 3 /HC cells. Through complementary in-situ UV and CV analytical techniques we reveal the formation of soluble species stemming from the partial decomposition of linear carbonates (DMC and EMC) in reduction into soluble products, hence stressing their failure to provide a stable solid electrolyte interphase (SEI) at the hard carbon electrode and by the same token accounting for the poor performance of the overall cell. We discuss the decomposition reaction paths, and propose a shuttle mechanism to account for the cell deterioration. Our results, which underscores the detrimental effects of linear carbonates in full Na-ion Na 3 V 2 (PO 4 ) 2 F 3 /HC cells, should serve as an impetus to identify superior electrolyte formulation for increasing the high temperature robustness of this technology.
The cationic pincer-type complexes [{(i-Pr2PCH2CH2)2CH}Ni(NCCH3)][BPh4] (1), [{2,6-(i-Pr2PCH2)2-C6H3}Ni(NCCH3)][BPh4] (2), [{2,6-(i-Pr2PO)2-C6H3}Ni(NCCH3)][BPh4] (3), and [{2,6-(i-Pr2PO)2-3,5-Cl2-C6H}Ni(NCCH3)][BPh4] (6) have been prepared and fully characterized by NMR spectroscopy and X-ray crystallography. Cyclic voltammetry measurements of the Ni−Br precursors of 2, 3, and 6 indicated that substituting the CH2 moiety in the ligand skeleton by O, or some of the aromatic protons by Cl, renders the metal center less susceptible to oxidation. Evaluating the catalytic activities of 1−3, 6, and the t-Bu analogue of 1 for addition of aniline to acrylonitrile showed 3 to be the most competent catalyst precursor. Isolation of [{(t-Bu2PCH2CH2)2CH}Ni(NCCH2CH2NHPh)][BPh4] (7) from the reaction of [{(t-Bu2PCH2CH2)2CH}Ni(NCCHCH2)][BPh4] with aniline suggests that these cationic precursors act as Lewis acids that bind the nitrile moiety of acrylonitrile, thereby activating the olefinic moiety toward nucleophilic attack by aniline.
Organometallic complexes of the general formula [(η(6)-arene)Ru(N⁁N)Cl](+) and [(η(5)-Cp*)Rh(N⁁N)Cl](+) where N⁁N is a 2,2'-dipyridylamine (DPA) derivative carrying a thiol-targeted maleimide group, 2,2'-bispyridyl (bpy), 1,10-phenanthroline (phen) or ethylenediamine (en) and arene is benzene, 2-chloro-N-[2-(phenyl)ethyl]acetamide or p-cymene were identified as catalysts for the stereoselective reduction of the enzyme cofactors NAD(P)(+) into NAD(P)H with formate as a hydride donor. A thorough comparison of their effectiveness towards NAD(+) (expressed as TOF) revealed that the Rh(III) complexes were much more potent catalysts than the Ru(II) complexes. Within the Ru(II) complex series, both the N⁁N and arene ligands forming the coordination sphere had a noticeable influence on the activity of the complexes. Covalent anchoring of the maleimide-functionalized Ru(II) and Rh(III) complexes to the cysteine endoproteinase papain yielded hybrid metalloproteins, some of them displaying formate dehydrogenase activity with potentially interesting kinetic parameters.
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