BATTERIES Carbon nanotube anode reduces risk factors in lithium-based batteries

| Author / Editor: Luke James / Johanna Erbacher

This is the claim of researchers at Texas A&M University who have reportedly developed a carbon nanotube anode for lithium-ion batteries that can reduce the risk of “catastrophic failure” and speed up recharging times.

A schematic illustrating the lithium battery with the team’s new carbon nanotube architecture for the anode.
A schematic illustrating the lithium battery with the team’s new carbon nanotube architecture for the anode.
(Source: Juran Noh, Texas A&M University)

Introducing new materials into the design of today’s lithium-ion batteries could dramatically improve their performance. Consequently, lots of research is currently taking place in this area and we are starting to see more and more promising results being published. Most recently, a research team at Texas A&M University has reportedly incorporated carbon nanotubes into the electrode of a lithium metal battery and produced a battery that is safer and can recharge in a fraction of the time of conventional lithium battery technology.

The research, which was published in the journal Nano Letters earlier this year, focuses on a battery architecture which carries with it huge potential.

Breaking the “energy density bottleneck”

When a conventional lithium-ion battery goes through its charge cycles, the lithium-ions are carried back and forth between the cathode and anode, the latter of which is typically made from a graphite and copper mixture. However, scientists believe that using pure lithium metal instead could be a great alternative because it offers a very high energy density and could lead to batteries that charge a lot faster and offer as much as 10 times more capacity.

“We have designed the next generation of anodes for lithium batteries that are efficient at producing large and sustained currents needed to quickly charge devices,” said Juran Noh, a material sciences grad student at Texas A&M. “Also, this new architecture prevents lithium from accumulating outside the anode, which over time can cause unintended contact between the contents of the battery’s two compartments, which is one of the major causes of device explosions.”

Last year, a study described the use of a lithium anode as being “critical to break the energy density bottleneck of current li-ion chemistry,” so, naturally, there is a huge amount of research interest in making it work.

Tackling dendrite formation

There is a big problem currently standing in the way of research, however - dendrite formation.

Dendrites are tree-like structures that build up on the surface of a battery’s anode when the lithium-ions aren’t evenly deposited. As they grow, they can pierce key components and cause it to short circuit or, even worse, combust and catch fire. Even if neither of these things happens, dendrites still cause the battery to quickly lose its charge.

The Texas A&M team believes that it has found the solution to this problem with ultralight and highly conductive nanotubes. In this research, carbon nanotubes have been used to build three-dimensional porous scaffolds that are then laced with molecules that cause lithium-ions to bind to its surface. After some experimentation, the team found that it had produced a battery anode where dendrites do not grow on its surface.

With the right amount of binding molecules, the team “could ‘unzip’ the carbon nanotube scaffolds at just certain places, allowing lithium-ions to come through and bind on to the entire surface of the scaffolds rather than accumulate on the outer surface of the anode and form dendrites,” explains Noh.

Not only does this make their battery safer but it also enables the battery to produce larger currents to the tune of five times that of conventional batteries. This means that it could possibly be recharged in a fraction of the time of current batteries.

“Building lithium metal anodes that are safe and have long lifetimes has been a scientific challenge for many decades,” Noh said. “The anodes we have developed overcome these hurdles and are an important, initial step toward commercial applications of lithium metal batteries.”