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Stanford University's next-gen lithium batteries could triple smartphone battery life

Researchers at Stanford University are working on a new lithium battery technology, which makes use of a nanoscopic carbon anode shield to improve battery life.
July 28, 2014

I’m sure the odds are pretty high that improved battery life is one of the, if not the, top feature that you would like to see in your next smartphone. If so, here’s a piece of prospective good news, researchers at Stanford University have come up with a lithium battery design that should last two to three times as long as current smartphone batteries.

The new battery design aims to solve efficiency problems of current li-ion cells, by replacing the anode barrier with a new nanoscopic carbon shield that allows for a higher battery capacity, which means that your handset will last longer. The carbon nanosphere wall applied at the battery’s anode is just 20 nanometers thick. For a sense of scale, you would need to stack 5,000 layers atop one another to reach the width of single human hair.

“The ideal protective layer for a lithium metal anode needs to be chemically stable to protect against the chemical reactions with the electrolyte, and mechanically strong to withstand the expansion of the lithium during charge” – Steven Chu, Stanford University

If you are in need of a more technical explanation – ideally batteries would make use of a pure lithium anode, as this would result in very high levels of efficiency. However, in reality this isn’t practical for use in a battery, as lithium ions expand as they gather on the anode during charging, leading to clusters or growths of lithium ions on the anode, which eventually short circuits the battery. There are also problems with excessive heat and short battery life spans.

Instead, a barrier is required over the anode to improve stability, but this ends up wasting some of the battery’s energy. Researchers have previously attempted to use lithium metal, silicon and tin as anodes, and sulphur and oxygen as cathodes, in search of superior energy storage densities, but they all have their trade-offs. Engineers are still attempting to reach the ideal lithium anode scenario, but without the fire and explosions.

Li-ion carbon nano layer
The carbon layer (bottom) prevents the build up of escaped lithium ions, preserving the battery’s life-cycle whilst improving anode efficiency.

Research conducted at Stanford has demonstrated that by coating a lithium metal anode with a monolayer of interconnected amorphous hollow carbon nanospheres, the lithium metal depositions can be isolated, which in turn leads to a more stable battery, whilst retaining most of the high capacity benefits of a lithium metal anode.

However, as is always the case with these emerging technologies, it is not quite ready for commercial use. The team is not quite at the 99.9 percent coulombic efficiency required of a commercial battery, but Steven Chu is positive that, after a bit more work, this technology could power the next generation of rechargeable batteries.