Understanding the Role of Imide-Based Salts and Borate-Based Additives for Safe and High-Performance Glyoxal-Based Electrolytes in Ni-Rich NMC811 Cathodes for Li-Ion Batteries.

Herein, the design of novel and safe electrolyte formulations for high-voltage Ni-rich cathodes is reported. The solvent mixture comprising 1,1,2,2-tetraethoxyethane and propylene carbonate not only displays good transport properties, but also greatly enhances the overall safety of the cell thanks to its low flammability. The influence of the conducting salts, that is, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(fluorosulfonyl)imide (LiFSI), and of the additives lithium bis(oxalato)borate (LiBOB) and lithium difluoro(oxalato)borate (LiDFOB) is examined. Molecular dynamics simulations are carried out to gain insights into the local structure of the different electrolytes and the lithium-ion coordination. Furthermore, special emphasis is placed on the film-forming abilities of the salts to suppress the anodic dissolution of the aluminum  current collector and to create a stable cathode electrolyte interphase (CEI). In this regard, the borate-based additives significantly alleviate the intrinsic challenges associated with the use of LiTFSI and LiFSI salts. It is worth remarking that a superior cathode performance is achieved by using the LiFSI/LiDFOB electrolyte, displaying a high specific capacity of 164 mAh g-1 at 6 C and ca. 95% capacity retention after 100 cycles at 1 C. This is attributed to the rich chemistry of the generated CEI layer, as confirmed by ex situ X-ray photoelectron spectroscopy.

MgSc2 Se4 -A Magnesium Solid Ionic Conductor for All-Solid-State Mg Batteries?

Recently, the ternary spinel selenide MgSc2 Se4 was proposed to have high magnesium ion mobility and is therefore an interesting potential candidate as a solid electrolyte in magnesium secondary batteries. To test the properties of the material, a modified solid-state reaction was used to synthesize pure MgSc2 Se4 . Electrochemical characterizations identified detrimental high electronic conductivities, which limit its application as a Mg-conducting solid electrolyte. Two methods were attempted to lower electronic conductivities, including the implementation of Se-rich phases and aliovalent doping, however, with no sufficient improvement. Based on the mixed conducting properties of MgSc2 Se4 , a reversible insertion/extraction of Mg2+ into the spinel structure could be demonstrated.

Electronically Tuned Asymmetric meso-Substituted Porphyrins for p-Type Solar Cells.

A series of electronically tuned asymmetric porphyrins have been synthesized for use in p-type solar cells. The porphyrin derivatives were strategically designed with electron-withdrawing capability and an electronic dipole gradient to aid in electron-harvesting capacity from a nickel oxide cathode. Specifically, the porphyrins were substituted at the meso position with different arrangements of the electron-withdrawing pentafluorobenzene moiety, electron-donating/coordinating 4-pyridyl ligand, and an electron withdrawing/synthetically modifiable 4-cyanophenyl unit. Two distinct free-base porphyrins were synthesized, one of which was further metallated with nickel(II). The porphyrins were fully characterized and their electronic properties explored experimentally by electrochemistry, and both steady state and time-resolved spectroscopy. Finally, the porphyrins were incorporated into a p-type solar cell device utilizing NiO as the cathode, and demonstrating a preliminary maximum performance of η(%)=0.082 and IPCEMAX (%)=26.0 without co-sensitization.