Adding a small amount of nanodiamonds to the electrolyte solution in lithium batteries can make these popular energy storage devices safer, according to a study (Nat. Commun. 2017, DOI: 10.1038/s41467-017-00519-2).
As lithium batteries are charged, lithium ions in the electrolyte solution migrate from the cathode through a micrometer-thin porous polymer separator and insert themselves in the anode. The anode in lithium-ion batteries is generally a form of graphite. That material is used because it reduces the chance that tiny, needlelike lithium structures—dendrites—will catastrophically short-circuit the battery by growing uncontrollably from the anode, piercing the insulating separator, and contacting the cathode.
If instead of using graphite, the anode were pure lithium metal, the battery’s charge-storage capacity could be almost 10 times as large. But metallic lithium anodes exacerbate the dendrite problem.
A team led by Drexel University’s Yury Gogotsi and Qiang Zhang of Tsinghua University reports that low-cost nanodiamond particles in the electrolyte solution guide lithium during electrochemical deposition to form smooth, dendrite-free films on lithium and other metallic electrodes.
The researchers explain that the nanodiamond surfaces serve as energetically favorable Li-ion adsorption and nucleation sites that enable Li ions to easily diffuse across the surface, coating it uniformly, rather than accumulating in small spots and forming dendrites.