Researchers at the University of California, Riverside have developed a low-cost chemical process for making nanosilicon anodes for high-performance lithium-ion batteries from waste glass bottles. The researchers say that the batteries have been found to have four times the capacity of conventional batteries with graphite anodes.

It has been known for a long time that silicon anodes can store up to 10 times more energy than conventional graphite anodes, but expansion and shrinkage during charge and discharge make them unstable. Downsizing silicon to the nanoscale has been shown to reduce this problem. The researchers used the relatively pure form of silicon dioxide in glass bottles to make the anodes for lithium-ion half-cell batteries.

The anodes were made by crushing and grinding the glass bottles down to a fine powder. The silicon dioxide in the glass was then transformed into nanostructured silicon using hot magnesium. The silicon nanoparticles were coated with carbon to improve their stability and energy storage properties.

Coin cell batteries made using the glass bottle-based silicon anodes greatly outperformed traditional batteries in laboratory tests.

When tested over 400 cycles, the bottle-based silicon anodes demonstrated a capacity of about 1,420 milliamp hours per gram – graphite anodes, which typically manage about 350 milliamp hours per gram.