Lithium-ion batteries have been powering phones and laptops for so long, it's easy to forget that other — potentially more promising — battery technologies exist. 

Reports now say Sony, which played a key part in popularizing Li-ion batteries in the 1990s, is working on new, sulfur-based batteries, which could offer up to 40% better energy density per volume. The report also states that Sony is working on magnesium-sulfur batteries, which are potentially both more efficient and cheaper than today's batteries.