Stanford researchers have created a stable pure lithium anode. It’s a huge step towards a dramatic increase in battery capacity.

We currently refer to rechargable batteries in portable devices as being “lithium ion” rather than simply lithium because today’s models only use lithium in the electrolyte and not the anode, which is usually silicon or graphite.

A lithium anode would allow batteries that are far more efficient in terms of volume and weight. The problem is that when charged, lithium expands dramatically. In previous attempt to create a lithium anode that’s led to cracking and short circuits.

Lithium anodes also react with the electrolyte in a way that not only uses up the electrolyte more quickly, but produces a potentially-dangerous increase in heat.

The Stanford researchers tackled this problem by building a carbon honeycomb layer that’s 20 nanometers thick to lay over the lithium anode. The layer is able to physically block the anode-electrolyte reaction, but is flexible enough to cope with the anode expanding and contracting.

The researchers say previous attempts to use this tactic have worked at 96 percent efficiency on first use, meaning 96 percent of the lithium put into the anode during charging can be extracted before the next charge. This dropped to less than 50 percent in 100 cycles.

The new design not only achieved 99 percent efficiency, but maintained it for 150 cycles. It will still need some refining however: to be commercially viable, a battery usually needs at least 99.9 percent efficiency.

One team member, Steven Chu (a former US Energy secretary) speculated that the end result of the process could be cellphones with up to three times the battery life of current models. He also suggested the possibility of an electric car battery with a 300 mile range, albeit at a potential cost of $25,000.