Study of new electrolytes based on bismuth and phosphate with application in lithium ion solid state batteries

EVANGELINA CARDILLO; S. TERNY; M.A. FRECHERO

Workshop; IWLIME; 2021

Our World demands new alternatives of sources of energy. New ways of production and storage have led the scientific and technological community to develop innovative devices that must be environmentally clean and safe. Those methods have to provide an efficient performance and a renewable use in order to allow a sustainable development. Considering this scenario, Lithium Ion Batteries play a leading role today.We have obtained a new modified lithium-bismuth-phosphate glass by the use of environmentally friendly components which are low cost and which can be eventually recycled. In this work we report some modifications in phosphate-bismuth-phosphate glass which allow huge improvements in their electrical properties because of the changes in the 3D structure making them exceptional candidates for being solid electrolytes in solid lithium ion batteries. We have explored the structural properties of phosphate glasses when a very small proportion of Bi2O3 is incorporated in the phosphate glassy matrix as former-modifier oxide and (MgO + Li2O) as modifier oxides. The fundamental reason for selecting such combination of oxides is the fact that if the appropriate ratio is chosen they modify the phosphate skeleton by reinforcing its connectivity, increasing its electrical conductivity due to the increase in the number of NBOs but, and more important, improving its chemical stability since many times high chemical resistance to a water media is required. On the other hand, the choice of Li2O instead of Na2O is something less explored and provides the chance to obtain a more electrical conductor material considering the new technological opportunities related to different applications of this kind of glasses. A family of glasses with a chemical composition according to the formula: xLi2O- yMgO (4.8 Bi2O3 47.6 P2O5) mol % was obtained by melt quenching technique and their structural features were studied taking into account the density, FTIR and UV?vis spectra. Their electrical properties were studied by impedance spectroscopy.Furthermore, a soft solid conductor material is obtained mixing the ionic glass powder (xLi2O- yMgO (4.8 Bi2O3 47.6 P2O5) with the ionic liquid [BMIM][PF6] in a low proportion (2% and 4%). At microscopic level, the interactions of this ionic liquid with the glassy particle surfaces reveal the formation of new bridging oxygens. Therefore, the material electrical conductivity increases in more than four orders of magnitude. This finding uncovers the essential elements to be considered before incorporating an additional salt to develop a solid electrolyte.