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Lithium-ion battery performance and longevity depend critically on the conducting salt utilized in the electrolyte. With new avenues for multifunctional integration and optimization of functional properties, conducting salts beyond lithium hexafluorophosphate (LiPF6) need to be studied. Herein we elucidate on viscosity, ionicity, anion self-diffusion and ionic conductivity through variation of the length of the perfluoroalkyl side chain present in the anions of the used lithium imidazole salts. Specifically, we study LiPF6 in comparison with lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI), lithium 4,5-dicyano-2-(pentafluoroethyl)imidazolide (LiPDI), and lithium 4,5-dicyano-2-(n-heptafluoropropyl)imidazolide (LiHDI). We find that the ion mobility of LiPF6 depends the least on viscosity and its ionicity is the highest among the electrolytes investigated here. LiTDI shows the strongest correlation between ion mobility and viscosity and the lowest ionicity. LiPDI and LiHDI range between these two regarding their ionicity and the correlation of mobility with viscosity. The previously rarely studied anion self-diffusion coefficients exhibit a strong correlation with viscosity as it was to be expected. Differences between the LiTDI, LiPDI and LiHDI salts are minute. [ABSTRACT FROM AUTHOR]

The article describes a research on new salts and cathode materials dedicated to sodium cells. Sodium technology is considered to be one of the most promising (for new battery generations) and has been very actively (re)‐developed for more than a decade. The first part of this work is mainly focused on electrochemical studies of the low coordinating Hückel type salt (4,5‐dicyano‐2‐(trifluoromethyl)imidazolate, NaTDI)‐based electrolytes with and without solid electrolyte interface modified additives: fluoroethylene carbonate (FEC). In the second part electrolytes are tested in a half‐cells with layered oxides. Sodium nickel‐manganese‐cobalt oxide (NaNMC) and WI‐NaNMC‐333 and WI‐NaNMC‐622 layered cathode materials are prepared by wet impregnation synthesis (WI) routine. Prussian White is obtained from University of Uppsala group to compare and initial electrochemical properties against electrolyte with NaTDI. Basic physicochemical properties of the obtained powders are also reported in the manuscript. The best properties are recorded for 0.75 m NaTDI in EC:DMC (1:1 v/v) with 3% FEC additive by its conductivity (11.52 mS cm−1 for 20 °C). The same solution also shows promising results during electrochemical tests in half‐cell geometry against WI‐NaNMC‐622 cathode (114.22 mAh g−1 after 1 cycle C/20). NaPF6 salt is used as an electrolyte as a commercially available reference. [ABSTRACT FROM AUTHOR]

Ni-rich layered oxides, i.e., LiNi0.6Mn0.2Co0.2O2 (NMC622) and LiNiO2 (LNO), were prepared using the two-step calcination procedure. The samples obtained at different calcination temperatures (750–950 °C for the NMC622 and 650–850 °C for the LNO cathode materials) were characterized using nitrogen physisorption, PXRD, SEM and DLS methods. The correlation of the calcination temperature, structural properties and electrochemical performance of the studied Ni-rich layered cathode materials was thoroughly investigated and discussed. It was determined that the optimal calcination temperature is dependent on the chemical composition of the cathode materials. With increasing nickel content, the optimal calcination temperature shifts towards lower temperatures. The NMC-900 calcined at 900 °C and the LNO-700 calcined at 700 °C showed the most favorable electrochemical performances. Despite their well-ordered structure, the materials calcined at higher temperatures were characterized by a stronger sintering effect, adverse particle growth, and higher Ni2+/Li+ cation mixing, thus deteriorating their electrochemical properties. The importance of a careful selection of the heat treatment (calcination) temperature for each individual cathode material was emphasized. [ABSTRACT FROM AUTHOR]