Rust anode lithium-ion battery boosts storage, hits full capacity after 300 cycles
The battery’s energy capacity rises as iron gradually converts into iron oxide.
Scientists have built a new a lithium-ion (Li-ion) battery anode that incorporates iron oxide, the main component of rust, into microscopic, porous hollow carbon structures, and can improve battery performance.
Researchers at Germany’s Saarland University and Austria’s University of Salzburg have teamed up to develop more environmentally friendly battery alternatives, as conventional lithium-ion batteries rely on materials such as nickel and cobalt.
While crucial to the performance of Li-ion batteries, especially for electric vehicles (EVs), these two critical transition metals come with several significant drawbacks, including toxicity issues, high costs and severe fire risks.
To tackle the challenge, the German team incorporated finely dispersed iron oxide (Fe2O3) into tiny, highly porous hollow carbon spheres. These were developed by Michael Elsaesser, PhD, an associate professor at the University of Salzburg.
Sustainable battery design
To develop the carbon spheres, Elsaesser and his research team drew inspiration from Mozartkugeln, the iconic Austrian confections made of pistachio, marzipan, and nougat and coated in dark chocolate.
The Saarland University team then applied this innovative concept to lithium-ion battery research, integrating finely dispersed iron into the structures. The carbon spherogels, are reportedly nanometer-sized materials.
Stefanie Arnold, PhD, a materials scientist at Saarland University, pointed out,
The challenge for us is to use chemical synthesis to fill the cavity inside these spheres with suitable metal oxides,
Each unit is around 250 nanometers (nm) in diameter and boasts a large surface area, as well as strong electrochemical capacity. Using a scalable synthesis based on iron lactate, the team introduced metallic iron nanoparticles into the carbon framework of the hollow spheres.
Arnold explained,
Iron has a number of advantages: it is abundant worldwide, it offers – in theory at least – a high storage capacity, and it’s easy to recycle,
The experiment produced a robust porous network with evenly distributed iron nanoparticles.
She said,
What was particularly interesting was that the storage capacity (i.e., the amount of electric charge that can be reversibly stored and released per gram of active electrode material) continued to increase while the battery was in use,
Rust-based battery anodes
According to the materials scientist, the longer the battery was used, the better it performed. She explained this by noting that the elemental metallic iron in the nanoparticles first has to react with oxygen to form iron oxide.
Arnold stated,
This process of electrochemical activation of the iron embedded in the carbon spherogel matrix is not immediate but happens progressively,
“It takes around 300 charge-discharge cycles until all the cavities in the carbon spheres are filled with iron oxide and the maximum storage capacity is reached.”
However, further research is needed before the mechanism can be scaled up. The activation process must be accelerated to reach full capacity sooner. For now, the iron oxide-filled spherogels have only been demonstrated as an anode material.
This ultimately means that a suitable cathode must still be paired with it to create a complete battery cell.
Volker Presser, PhD, professor of energy materials at Saarland University, said,
We are confident that our approach will facilitate the development of environmentally friendly buffer storage systems for renewable energy,
Meanwhile, the novel material will also be tested for sodium-ion batteries, which Chinese automotive producers are already deploying. The same synthesis method could also be adapted to host other functional materials, and open the door to a broader platform for advanced energy storage.
Elsaesser concluded in a press release,
These materials form a versatile technology platform that allows a wide variety of other substances to be integrated in situ into the spherogels in a single synthesis step, opening up opportunities for a wide range of technological applications,
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Rust anode lithium-ion battery boosts storage, hits full capacity after 300 cycles, source
