A Norwegian tech company says its "SiliconX" battery can let you drive over 600 miles or power your smartphone for a week on just a single charge when compared to an equivalent volume of Li-ion cells. Its secret is a proprietary mixture of silicon and graphite that will give up to a five-fold in battery capacity over current Li-ion technology.
https://www.notebookcheck.net/New-silicon-graphite-mixture-promises-over-four-times-the-battery-life-of-traditional-Li-ion-batteries.317688.0.html