Currently, most portable devices use lithium-ion battery technology, in spite of the fact that a pure lithium battery could offer much more capacity.
The problem is with longevity, as a pure lithium battery may have 300% the capacity of a lithium-ion battery, but it can only be cycled between 50 and 100 times before it begins to degrade and lose capacity. To take advantage of the superior capacity of lithium, current lithium-ion batteries, typically Li-ion NMC (lithium-ion nickel-manganese cobalt oxide) only use lithium in the electrolyte, basically only a third of the battery. The anode and cathode could be made of pure lithium, or an alloy thereof, but the reactivity of lithium doesn’t make this possible. When cycling, the lithium electrodes expand and contract and eventually break down or even break through the battery case.
Either way, a pure lithium battery is short-lived, making it unusable for long-term applications in portable electrical and electronic devices, from smartphones and laptops to electric vehicles and smart buildings. All of these applications could certainly benefit from the higher energy density that a pure lithium battery would offer, but the lifespan needs to be improved. The Li-ion NMC battery pack in the Tesla Model S, for example, can be cycled around 800 times. A lithium-sulfur battery may have up to six times more energy, but can only be cycled about a dozen times. A pure lithium battery, on the other hand, could have up to four times more energy, and nanotechnology could improve the lifespan from 50-100 cycles to over 300 cycles.
Stanford University researchers took existing pure lithium battery technology, that is, with pure lithium electrodes and a lithium-based electrolyte, and added a protective layer of pure carbon nanodomes. The pure carbon nanodomes are just 20 nm thick, allowing for the passage of lithium ions during cycling. At the same time, they allow the lithium electrodes to expand and contract uniformly, greatly improving their lifespan. So far, researchers have gotten the pure lithium battery up to 150 cycles while maintaining 99% capacity, and could go as high as 300 cycles.
An electric vehicle with a pure lithium battery could theoretically cost just $25,000 and have a range of 300 miles, according to Stanford University researcher Guangyuan Zheng.
Image © Stanford University
