RESEARCH

Solid-state batteries have received renewed attention in recent years due to the growing demand for high energy density rechargeable batteries. The highest energy density of Li and Na batteries can be reached if thin foils of the active metals can serve as the anodes. Solid state electrolytes may be much more compatible with Li and Na metal anodes than conventional liquid electrolyte solutions. This is a major driving force for developing solid state batteries. There are continuous efforts to increase the possible energy density of rechargeable Li and Na batteries, while maintaining high efficiency, and best safety features.

Solid electrolytes can be divided into three groups. Inorganic electrolytes, organic electrolytes, and composite (polymers + ceramic particles) electrolyte systems:
- Inorganic electrolytes can reach relatively high conductivity at room temperature and a wide electrochemical window, but on the other hand, suffer from poor adhesion to the electrodes and a tendency to break.
- Organic electrolytes are polymers in which salts are dissolved where the cations are alkali metal ions that migrate in the polymer medium. Although the problems of adhesion and brittleness of polymeric electrolytes are almost non-existent, the conductivity of most of polymeric electrolytes at room temperature is poor, requiring operating temperatures above Tm of the polymer electrolyte (about 60 C for many polyethers).
- Composite electrolyte systems combining both ceramic and polymeric systems compensate for the limitations and may show synergistic effects and may allow approaching the performance of liquid-based electrolyte systems.

The most used polymeric electrolytes today are based on polyethylene oxide (PEO), mainly due to the convenience of working with PEO based systems. As stated above, the polymer must dissolve a suitable salt, leading to charge separation and ions mobility under an electrical field, in order to meet the definition of a solid electrolyte.
Regarding composite solid electrolytes, as long as their matrices constitute polymers as the major component, the ceramic materials appear to serve mostly as additives with secondary effects on the specific conductivity even when the ceramic materials are intrinsically ions conductors. Hence, improvement in the conductivity of composite solid electrolytes may be due to additional ions transport paths in the polymer-ceramic interfaces, rather due to bulk ionic conductivity through the ceramic particles mixed with the polymers in the composite matrices. It also seems that some ceramic materials may act as scavengers for products of parasitic reactions when used in battery systems.
Our group work with:
- Active and non-active ceramic filers, different salt type, various ceramic filers shape such as: sphere, nanotubes, and nanowires. Salt-free systems. Surface treatment.
- Symmetric cell with blocking and non-blocking electrodes, as well as full cells.
- Impedance process analysis: monitoring the cells performance (i.e.: bulk conductivity and SEI formation) with time and compering cells performance in static (aging) conditions vs. dynamic (cycling) conditions.
- Compering interface of inorganic electrolytes particles in polymer and inorganic electrolytes pellets with polymer membrane.
- Spectroscopic analysis: NMR, XPS.