Lithium-ion batteries, which have been installed mainly used in portable electronics, are anticipated to be used for vehicle and grid applications.  Because batteries for these applications are much larger than that for consumer use, safety issues originated from the combustible electrolytes are much more serious.  Nonflammable solid electrolyte is expected to give a fundamental solution to the safety issues.  In order to realize solid-state lithium batteries, solid electrolytes having high ionic conductivities are necessary.  High ionic conductivities have been often found in sulfides, because large sulfide ions leave wide opening for ionic conduction, and their high polarizability makes lithium ions highly mobile.  The highest conductivity has reached 10-2 S cm-1 in Li10GeP2S12. However, sulfide-based solid electrolytes have a drawback.  In spite of the fast ionic conduction in the bulk, high impedance appears at the interface to the cathode.  Noble potential of the cathode tends to decrease lithium-ion concentration on the electrolyte side of the interface.  Moreover, the decrease in the lithium-ion concentration is intense in sulfide-based electrolyte systems to form a lithium-depleted layer and make the interface highly-resistive, because attraction between sulfide and lithium ions is weak. Because the high interfacial resistance results from the noble potential of the cathode, the interfacial resistance will be reduced by shielding the sulfide-based solid electrolyte from the noble potential.  In fact, surface coating onto the cathode material particles, which separates the sulfide-based electrolyte from the cathode material, has successfully reduced the interfacial resistance and enhanced the power density to be high enough for practical use.  In addition, a self-organized core-shell structure found in LiAlyCo1-yO2 particles has the same effect on the reduction of the interfacial resistance.  Such interfacial structures will be presented in the symposium.

Cathode/electrolyte interface in solid-state lithium batteries with sulfide solid electrolytes

247th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.