The quest for a better battery is engaging a lot of scientific minds, but it’s not often three advances are reported at pretty well the same time.
Two from the US address the challenge of making next-gen lithium batteries more commercially viable, while the third, from the UK, uses MRI in a novel way.
In the first study, led by the US Army Research Laboratory, researchers have demonstrated a new electrolyte design for lithium-ion batteries – which soldiers use regularly in the field but often find wanting.
In a paper in the journal Nature Energy, they describe developing a self-healing protective layer in the battery that significantly slows the electrolyte and silicon anode degradation process, while increasing the number of possible cycles from tens to over a hundred.
The design demonstrated a coulombic [the basic unit of electric charge] efficiency of 99.9%, they say, which meant only 0.1% of the energy was lost each cycle.
Conventional designs for lithium-ion batteries with silicon anodes have a 99.5% efficiency, and this seemingly small difference translates to a cycle life more than five times longer, according to Army scientist Oleg Borodin.
In the second paper, published in the journal Joule, researchers from the University of Texas report they have found a way to stabilise one of the most challenging parts of lithium-sulfur batteries.
Creating an artificial layer containing tellurium, inside the battery in-situ, on top of lithium metal, can make it last four times longer, they say. “The layer… allows it to operate without breaking down the electrolyte…” says co-author Amruth Bhargav.
No expensive or complicated pre-treatment or coating procedures are required on the lithium-metal anode, he and his colleagues add, and the method can be applied to other lithium- and sodium-based batteries.
The third paper, in the journal Nature Communications, describes a technique to detect the movement and deposition of sodium metal ions within a sodium battery using magnetic resonance imaging (MRI).
Although sodium appears to have many of the properties required to produce an efficient battery, there are challenges in optimising the performance.
Key among these, says research leader Melanie Britton from the University of Birmingham, is understanding how the sodium behaves inside the battery as it goes through its charging and discharging cycle, enabling the points of failure and degradation mechanisms to be identified.
“Taking the battery apart introduces internal changes that make it hard to see what the original flaw was or where it occurred, but using the MRI technique we’ve developed we can actually see what’s going on inside the battery while it is operational, giving us unprecedented insights into how the sodium behaves,” Britton says.
Developed with colleagues at the University of Nottingham and Imperial College London, the technique also will enable scientists to monitor the growth of dendrites – branch-like structures that can grow inside the battery over time and cause it to fail or even catch fire.