In this manuscript, we report an extensive study of the physico-chemical properties of different samples of O3-NaMnO₂, synthesized by sol–gel and solid state methods. In order to successfully synthesize the materials by sol–gel methods a rigorous control of the synthesis condition has been optimized. The electrochemical performances of the materials as positive electrodes in aprotic sodium-ion batteries have been demonstrated. The effects of different synthesis methods on both structural and electrochemical features of O3-NaMnO${}_2$ have been studied to shed light on the interplay between structure and performance. Noticeably, we obtained a material capable of attaining a reversible capacity exceeding 180 mAhg${}^{-1}$ at 10 mAg${}^{-1}$ with a capacity retention >70% after 20 cycles. The capacity fading mechanism and the structural evolution of O3-NaMnO${}_2$ upon cycling have been extensively studied by performing post-mortem analysis using XRD and Raman spectroscopy. Apparently, the loss of reversible capacity upon cycling originates from irreversible structural degradations.

In this work, the use of N-methyl-N-propylpiperidinium difluoro(oxalato)borate Pip₁₃DFOB ionic liquid (IL), originally synthesized in our laboratory, as an additive for liquid electrolytes in lithium-ion batteries (LIBs), is proposed. The synthesized IL exhibits glass and melting transitions at −70.9 °C and 17.1 °C, respectively, and a thermal decomposition temperature over 230 °C. A mixture based on 1.0 M LiPF₆ in 1:1 v/v ethylene carbonate (EC): dimethyl carbonate (DMC) electrolyte solution (so called LP30) and the IL was prepared and tested in lithium metal cells versus two different commercially available carbonaceous electrodes, i.e., graphite (KS6) and graphene (GnP), and versus a high voltage LiNi_0.5Mn_1.5O₄ (LNMO) cathode. A noticeable improvement was observed for Li|LNMO cells with an IL-added electrolyte, which exhibited a high specific capacity above 120 mAh g⁻¹ with a Coulombic efficiency above 93% throughout 200 cycles, while the efficiency fell below 80% after 80 cycles with the absence of IL. The results confirm that the IL is promising additive for the electrolyte, especially for a longer cycle life of high-voltage cells.

The structural and thermal properties of mixtures formed by choline chloride and hydroxyphenol isomers at various compositions have been investigated to determine the most promising deep eutectic solvent system.

Ionic liquids (ILs) including oxalatoborate anions, like bis(oxalato)borate (BOB) and difluoro(oxalato)borate (DFOB) are extensively used in the battery sector as additives to promote the formation of protective layers on the surface of high-voltage cathode materials. In this work four ILs have been synthesized: N-ethoxyethyl-N-methylpiperidinium bis(oxalato)borate (PIP_1,2O2BOB), N-ethoxyethyl-N-methylpiperidinium difluoro(oxalato)borate (PIP_1,2O2DFOB), N-propyl-N-methylpiperidinium bis(oxalato)borate (PIP_1,3BOB) and N-propyl-N-methylpiperidinium difluoro(oxalato)borate (PIP_1,3DFOB) and their thermal properties have been linked to their structure. The presence of an oxygen atom in the PIP_1,2O2 lateral chain suppresses crystallization of the ILs. Furthermore, PIP_1,2O2DFOB shows a lower glass transition temperature than PIP_1,2O2BOB. These observations have been explained using a combined molecular dynamics and density functional theory approach and an increase in the degree of freedom of the lateral chain of the cation due to the ether oxygen has been found. Comparing PIP_1,2O2DFOB and PIP_1,2O2BOB, a notable interaction between different domains of the anions is observed and is stronger in the DFOB case due to the charge-delocalization induced by the fluorine atoms, which generates a relatively positive charge on the boron atom. This is correlated to the weaker cation-anion attraction which hinders the glass transition of PIP_1,2O2DFOB.