A team of scientists at Yokohama National University in Japan has developed a new type of positive electrode material with “unprecedented stability” in solid-state batteries (SSBs). The material the research team focused on was Li8/7Ti2/7V4/7O2, a binary system composed of optimized portions of lithium titanate (Li2TiO3) and lithium vanadium dioxide (LiVO2). When ball-milled down to an appropriate particle size in the order of nanometers, this material offers high capacity thanks to its large quantity of lithium ions that can be reversibly inserted and extracted during the charge/discharge process, the researchers say.
Unlike other positive electrode materials, Li8/7Ti2/7V4/7O2 has a special property that makes it stand out: it has nearly the same volume when fully charged and fully discharged. The researchers say they analyzed the origin of this property and concluded that it is the result of a fine balance between two independent phenomena that occur when lithium ions are inserted or extracted from the crystal.
The research team tested this new positive electrode material in an all-solid-state cell by combining it with an appropriate solid electrolyte and a negative electrode. This cell exhibited a capacity of 300 mA.h/g with no degradation over 400 charge/discharge cycles. By further refining dimensionally invariant electrode materials, the team says it may soon be possible to manufacture batteries that are good enough for electric vehicles in terms of price, safety, capacity, charging speed, and lifespan.
