No abstract

The purpose of this work was to study the performance of a sodium-ion battery based on the sodium vanadium phosphate /sodium titanate in the temperature range from +20 to-45 °C. To achieve this goal the methods of galvanostatic cycling and pulse chronopotentiometry were used. The performance of sodium-ion battery at low temperatures was found to be limited by the functioning of the negative electrode based on sodium titanate, which remains operational only at temperatures not less than-35 °C. The positive electrode based on sodium vanadium phosphate is efficient at temperatures down to-45 °C. The activation energy of sodium diffusion in the sodium vanadium phosphate and the sodium titanate is about 42 and 70 kJ / mol, respectively.

The presence of dimethylacetamide (DMAA) in the composition of electrolytes of a sodium-ion battery destroys the passive film on electrodes and results in a number of reactions not connected with the electrochemical process that must be considered in developing such batteries. Introducing DMAA into the composition of a battery electrolyte greatly improves the conductivity of the polymeric membrane that separates the cathode and anode spaces. However, it is established that in the presence of sodium metal, anhydrous DMAA undergoes Claisen-like self-condensation with subsequent reactions. IR spectroscopy is used to explain the causes of the electrochemical instability of sodium perchlorate solutions in mixed solvents containing DMAA.

Phosphorus-carbon composite was prepared by combined method consisting of grinding a mixture of red phosphorus with Ketjenblack EC300J followed by sublimation-condensation with simplified temperature scenario. The composite was characterized by XRD, EDX, SEM, and Raman-spectroscopy. The electrodes with such a composite were studied by galvanostatic cycling and cyclic voltammetry. The electrodes delivered the discharge capacity of 1870 mAh g −1 at C/20 and 190 mAh g −1 at 10C. The sodium effective diffusion coefficient in the composite was estimated as (3−4)*10 −14 cm 2 s −1 .