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An electrochemical electrophilic bromination/spirocyclization of N-benzyl-acrylamides with 2-bromoethan-1-ol as the brominating reagent has been developed. The paired electrolysis employs low concentrations of bromine produced from both cathodic reduction and anodic oxidation as an electrophile, and realizes an H2O-involved electrophilic spirocyclization. A number of unexplored brominated 2-azaspiro[4.5]decanes are obtained with satisfactory yields under mild conditions, and the reaction exhibits good efficiency at the gram-scale synthesis. In addition, this approach is further highlighted by late-stage transformations and synthetic applications in constructing cyclohepta[c]pyrrole-1,6-diones via debromination tandem cyclization of brominated 2-azaspiro[4.5]decanes. [ABSTRACT FROM AUTHOR]

The limited discharge capacity of LiCoO2 can be improved by increasing its working potential, but it suffers from Co4+ dissolution and decomposition of the electrolyte. Nitriles have attracted great interest as high-voltage electrolytes due to their wide electrochemical window. However, the cathodic interfacial stability of nitrile electrolytes with a high-voltage LiCoO2 cathode has yet to be explored. Herein, we adopted an SN-based deep eutectic electrolyte with SN as the only solvent and found that Co4+ could be reduced by the SN solvent on the interface of the LiCoO2 electrode, causing a reverse phase change of LiCoO2 and severe self-discharge of the LiCoO2‖Li and LiCoO2‖Li4Ti5O12 batteries. When LiDFOB was introduced into the electrolyte, the self-discharge behavior of cells could be largely decelerated. The series of characterizations performed in our work revealed that the cathode/electrolyte interface generated from the LiDFOB salt could stabilize the interface of LiCoO2 and suppress the dissolution of the ions of the transition metal Co. [ABSTRACT FROM AUTHOR]

We report a strategy employing a concentrated electrolyte to boost the cycling stability of LiCoO2/graphite cells at 90 °C for the first time. Such a concentrated electrolyte provides the cells with superb cycling stability (97% after 160 cycles) at 90 °C. Further investigations unveil that the concentrated electrolyte participates in the formation of a compact LiF-rich CEI layer, which effectively inhibits the decomposition of electrolyte solvent and the dissolution of Co2+, maintaining the structural integrity of the LiCoO2 cathode. [ABSTRACT FROM AUTHOR]

Polycarbonate electrolytes have attracted great interest in recent years due to their high ionic conductivity. However, the cathodic interfacial stability of polycarbonate electrolytes has yet to be explored. Herein, we reported an unusual reverse cation-redox reaction in which Fe3+ was reduced to Fe2+ by poly(propylene carbonate) (PPC) at the interface of a LiFePO4/PPC based solid polymer electrolyte during the first charge process at low current density. The XPS and in situ XRD results indicate the simultaneous existence of LiFePO4 (Fe2+) and FePO4 (Fe3+) in the overcharge process. Besides, the DEMS result indicates that CO2 could originate from the oxidation decomposition of PPC at the cathode surface. During this reaction, the oxidation of the polymer, rather than transition metal ions, serves as the source for charge compensation, leading to a significant overcharge issue. Furthermore, we found that the appearance of LiF on the cathode electrolyte interphase (CEI), tested by XPS, can stabilize the LFP/PPC interface. Consequently, a LiF layer is fabricated on the PPC-SPE surface, which significantly limits the overcharge issues. [ABSTRACT FROM AUTHOR]

A visible-light-induced radical relay cyclization/C-C bond formation of quinoxalin-2(1 H )-ones with allyloxy-tethered aryl iodides using polysulfide anions as a photocatalyst is described. This protocol allows efficient access to a variety of complicated molecules bearing both quinoxalin-2(1 H )-one and 2,3-dihydrobenzofuran motifs in high yields under mild reaction conditions with a broad range of substrates.

The limited discharge capacity of LiCoO2 can be improved by increasing its working potential, but it suffers from Co4+ dissolution and decomposition of the electrolyte. Nitriles have attracted great interest as high-voltage electrolytes due to their wide electrochemical window. However, the cathodic interfacial stability of nitrile electrolytes with a high-voltage LiCoO2 cathode has yet to be explored. Herein, we adopted an SN-based deep eutectic electrolyte with SN as the only solvent and found that Co4+ could be reduced by the SN solvent on the interface of the LiCoO2 electrode, causing a reverse phase change of LiCoO2 and severe self-discharge of the LiCoO2|Li and LiCoO2|Li4Ti5O12 batteries. When LiDFOB was introduced into the electrolyte, the self-discharge behavior of cells could be largely decelerated. The series of characterizations performed in our work revealed that the cathode/electrolyte interface generated from the LiDFOB salt could stabilize the interface of LiCoO2 and suppress the dissolution of the ions of the transition metal Co.

We report a strategy employing a concentrated electrolyte to boost the cycling stability of LiCoO2/graphite cells at 90 °C for the first time. Such a concentrated electrolyte provides the cells with superb cycling stability (97% after 160 cycles) at 90 °C. Further investigations unveil that the concentrated electrolyte participates in the formation of a compact LiF-rich CEI layer, which effectively inhibits the decomposition of electrolyte solvent and the dissolution of Co2+, maintaining the structural integrity of the LiCoO2 cathode.