Researchers in the Cockrell School of Engineering at The University of Texas at Austin have developed a new family of anode materials that can double the charge capacity of lithium-ion battery anodes. The new family of anode materials, which the researchers dubbed the Interdigitated Eutectic Alloy (IdEA) anode, also saves time and materials by producing an anode using only two simple steps instead of the multiple steps traditionally required to mass-produce lithium-ion battery anodes. It is a simple, low-cost approach that can be applied to a broad range of alloy systems with various working ions such as Li, Na, or Mg.
The researchers created an aluminum-tin foil that is one-quarter of the thickness and half of the weight of the graphite and copper anodes used in virtually all lithium-ion batteries today. As a metallic foil, the IdEA anode does not require an external current collector, significantly reducing the fraction of inactive components. The IdEA anode in the study offers a fully realized capacity of 250 mAh g-1 for more than 150 cycles. By comparison, realized capacity in a graphite/copper composite anode is only ~ 150 mAh g-1.
The results suggest that a smaller, lighter rechargeable battery could be made with the new anode in the future. The research was published in the journal ACS Energy Letters.
While alloy anodes offer high charge-storage capacities, the huge volume changes along with high irreversible capacity loss result in catastrophic capacity fade. Attempts to accommodate the volume changes by nanostructuring the material and buffering with inactive components often result in diminished active-material loading and high processing cost. An alternative processing strategy uses an eutectic alloy microstructure to accommodate the volume change. We demonstrate here that the casting and anisotropic cold rolling of a binary eutectic alloy offers a simple, scalable framework for the production of a high-performance, interdigitated eutectic alloy (IdEA) foil anode.
The aluminum-tin IdEA foil anode presented here as an example has nanosized electrochemically active tin domains surrounded by an electrically conductive aluminum network, enabling stable cycling.—Kreder et al.
Recent efforts to improve lithium-ion battery electrodes have focused on building new nanomaterials atom by atom. Professor Arumugam Manthiram, director of the Texas Materials Institute, and his team, which includes postdoctoral fellow Karl Kreder and materials science and engineering graduate student Brian Heligman, developed a new class of anode materials in which eutectic metal alloys are mechanically rolled into nanostructured metal foils.
(An eutectic alloy is a mixture of two or more components in such proportion that their combined melting point is the lowest attainable. Eutectic alloys are fusible: upon cooling they convert from liquids to intimately mixed solids. Earlier post.)
Since the 1990s, the primary anode for mass-produced rechargeable lithium-ion batteries has been a graphite powder coated on a copper foil. The copper adds bulk to an electrode without improving the battery’s power and the anode requires a laborious, fastidious manufacturing process. By omitting the complicated slurry coating process, the manufacturing of the IdEA anode is drastically simplified.
Kreder, who is the lead author on the study, realized that a micrometer-scale alloy anode could be transformed into a nanomaterial using traditional metallurgical alloying processes.
The eutectic microstructure forms naturally because of thermodynamics. Then, you can reduce the microstructure by rolling it, which is an extraordinarily cheap step to convert a microstructure into a nanostructure.—Karl Kreder
The team’s resulting anodes occupy significantly less space, overcoming a critical barrier to commercializing better batteries for use in portable electronic devices like cellphones and medical devices, as well as larger applications like electric cars.
It is exciting to have developed an inexpensive, scalable process for making electrode nanomaterials. Our results show that the material succeeds very well on the performance metrics needed to make a commercially viable advance in lithium-ion batteries.—Professor Arumugam Manthiram
The research was funded by a grant from the US Department of Energy’s Office of Basic Energy Sciences, Division of Materials Sciences and Engineering.
Karl J. Kreder, III, Brian T. Heligman, and Arumugam Manthiram (2017) “Interdigitated Eutectic Alloy Foil Anodes for Rechargeable Batteries” ACS Energy Letters 2 (10), 2422-2423 doi: 10.1021/acsenergylett.7b00844