New research sheds light on preventing “dead lithium” accumulation
Lithium electrode growth while charging in a new dilute electrolyte (left). (Right) while charging, lithium deposits on the electrode, causing accumulation of large, crystalline dendrites that nearly completely dissolve on uncharging.
That’s how many phones Samsung had to recall after realizing the lithium-ion batteries used in the phone were prone to spontaneous combustion. Although some have speculated shoddy construction was to blame, Samsung was only one of dozens of companies forced to recall these types of batteries in the past five years due to overheating or fires.
Clearly, there is a problem with lithium-ion batteries.
Just like all batteries, when lithium-ion batteries are charged and uncharged, the electrodes transfer electrons back and forth through the liquid electrolyte. Unlike other batteries however, this electrochemical reaction is not fully reversible, leading “dead” lithium dendrites on both the electrode and floating in the electrolyte. If enough of this metal accumulates, the battery could short circuit causing electrical failure in the best case, or combustion in the worst case. But despite decades of research on improving the efficiency and safety of lithium ion batteries, the buildup of lithium dendrites appears to be inevitable.
But researchers at Pacific Northwest National Lab may have discovered the solution to inhibiting the accumulation of this dead lithium.
In work recently published in Nature Communications, Dr. Layla Mehdi and colleagues used in situ liquid STEM to study the deposition and stripping of lithium in a nanoscale battery as it was charged and uncharged. They used the electrochemistry capabilities of their Poseidon Select system which allow direct electrical measurements to be taken within the TEM. Their insight came while they were watching lithium dendrites grow in different concentrations of electrolyte. They discovered that by adding only 50 ppm of water to the electrolyte, the lithium deposition during charging went from small, spongy particles to large, single lithium grains. As a result, the larger grains more energetically favored complete dissolution during uncharging, causing far less dead lithium to accumulate. This finding solves one of the key problems inhibiting the efficiency of lithium-ion batteries and could pave the way for a new generation of high powered batteries.
Dr. Mehdi is no stranger to the field of battery research, having published dozens of papers in top journals since finishing her Ph.D in 2012. Her work on the “Quantification of Electrochemical Nanoscale Processes in Lithium Batteries by Operando ec-(S)TEM” won her the distinguished 2015 M&M Post-Doctoral Researcher Award from the Microscopy Society of America. Truly a bright young researcher, she will be presenting much of her work in an upcoming webinar hosted by Protochips and Materials Today. Entitled “In Situ TEM – the New Frontier for Liquid Chemistry”, the webinar will also feature research in the field of functional nanomaterials.
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