Revolutionary Technique Promises Longer-Lasting Electric Vehicle Batteries
Imagine driving your electric vehicle (EV) twice as far on a single charge. This could become a reality with the development of lithium-metal anodes, which offer significant advantages over the existing graphite anodes in batteries. However, a persistent challenge has been the formation of dendrites—microscopic spikes that can lead to short circuits.
Researchers have discovered a novel approach to prevent dendrite formation: a simple 20-minute soak of lithium foils in a 1% water etching solution. Jiaxing Huang, a materials scientist at Westlake University, compares this chemical bath to a soothing warm bath for the lithium-metal foil, suggesting it could serve as a straightforward solution for manufacturing lithium-metal batteries.
An untreated lithium-metal foil quickly becomes covered in dendrites after 20 charge cycles, whereas one treated with the etching solution maintains a smooth surface. This difference is critical, as dendrites form due to the polycrystalline nature of lithium films, which consist of tiny crystal grains with varying orientations. As Huang explains, “The different facets have different atomic density and different chemical reactivity,” leading to faster lithium deposition at more reactive sites.
While a single crystal of lithium would experience uniform plating, producing such a form is costly and complex. Instead, Huang’s team has developed a method to convert the polycrystalline surface to a quasicrystalline one, aligning the crystal grains in the same orientation. This approach draws on Huang’s previous work in shaping metal nanocrystals by etching less-stable facets to stabilize them.
The researchers applied this principle to lithium-metal batteries, using water as an etchant. However, since pure water reacts explosively with lithium, they diluted it to 1% in dimethyl sulfoxide, allowing safe immersion of the lithium-foil anode.
The etching solution erodes the less-stable facets, causing the lithium atoms to rearrange into a stable (110) crystal orientation. This rearrangement results in more uniform lithium plating. In experiments, coin-sized lithium iron phosphate batteries with treated anodes maintained functionality over 2,000 charge cycles without dendrite-induced failure.
Younan Xia, a nanomaterials researcher at Johns Hopkins University, praises the technique as “a brilliant idea to effectively address a major issue in lithium-based batteries.” For practical application, Xia notes the method must scale to larger electrode areas and reduce treatment time to cut production costs, suggesting it could soon be adopted in commercial battery manufacturing.
Original Story at cen.acs.org