A team of researchers from Stanford University and the SLAC National Accelerator Laboratory has published a research paper detailing a novel design for Lithium-Ion batteries. The team used nanoparticles arranged in a manner similar to the seeds of the pomegranate fruit.
The research team arranged silicon nanoparticles encased in a carbon "rind" to get past the limitations of current silicon-based Lithium-Ion battery designs. With this new type of electrode, the researchers say that their findings may bring forth more compact and more powerful batteries for a wide variety of applications.
"While a couple of challenges remain, this design brings us closer to using silicon anodes in smaller, lighter and more powerful batteries for products like cell phones, tablets and electric cars," said Stanford associate professor Yi Cui, who led the team.
The team published its findings in the online journal Nature Nanotechnology. Unlike current Lithium-Ion batteries, the pomegranate-inspired electrode will also be able to last more charging cycles. The current generation of batteries often suffers from a considerable drop in efficiency after a certain number of charging cycles.
"Experiments showed our pomegranate-inspired anode operates at 97 percent capacity even after 1,000 cycles of charging and discharging, which puts it well within the desired range for commercial operation," Cui added.
When charging a battery, all the energy is stored in the negative cathode. Most types of batteries currently available use graphite anodes. However, silicon-based anodes have the capacity to store 10 times more energy than a graphite-based anode. Unfortunately, there are a number of limitations when it comes to using silicon for manufacturing battery anodes. When silicon comes into contact with the electrolyte used in batteries, an unwanted reaction occurs. This reaction creates a by-product that can coat the anode. When this happens, the efficiency of the battery drops. Moreover, silicon can also swell and disintegrate during charging cycles.
To get around the current limitations of silicon-based anodes, the research team used silicon nanowires to create a new type of electrode. Since these nanowires are already too small to break down into smaller parts during charging cycles, silicon disintegration can be avoided. The team also encased the nanoparticles in a carbon shell, making sure to give the silicon nanoparticles enough room to swell. Each carbon shell was then gathered and encased into a larger carbon "rind" that holds the small clusters together. This gives the electrode its distinctive pomegranate appearance.
"To me it's very exciting to see how much progress we've made in the last seven or eight years and how we have solved the problems one by one," said Cui.
While the research shows promise, there are still a number of problems that need to be solved before the design can be mass produced. First of all, a more cost-effective source of silicon nanoparticles must be found. Secondly, the process must be simplified to bring down production costs.