A new study published in Nanotechnology journal Nature Publishing Group’s Nature Nanotechnology has found that microscopic boron nitride nanotubes can transport lithium ions at speeds far greater than previously expected. 

These tiny tube-shaped channels were shown to selectively move lithium ions while blocking many other ions, effectively creating a high-speed pathway for lithium transport. The findings suggest that boron nitride nanotubes could serve as a promising platform for next-generation separation technologies. 

Potential applications include clean energy production, including blue energy systems that generate power from the mixing of saltwater and freshwater, as well as more efficient lithium extraction for battery manufacturing.

New ion transport mechanism surpasses theoretical expectations 

According to Sangil Kim, the newly identified transport mechanism enables lithium ions to move through nanotubes at exceptionally high speeds. Kim, an associate professor of chemical engineering at University of Illinois Chicago and co-author of the study, noted that the observed ion transport rates significantly exceeded both theoretical predictions and results reported in existing experimental systems, highlighting the unusual efficiency of the nanotube-based approach.

Efficient ion transport plays a critical role in a wide range of industrial applications. When salts dissolve in water, they split into positively and negatively charged ions that travel through nanochannels at varying speeds. Managing and controlling this ion movement across membranes is essential for advancing technologies such as batteries, desalination systems, critical mineral extraction, and renewable energy generation.

Still, balancing fast ion movement with high selectivity remains a major scientific and engineering challenge. In this study, the researchers developed membranes containing millions of tiny boron nitride nanotubes, which have charged surfaces and unusual transport properties. When placed between solutions with different salt concentrations, the membranes allowed ions to pass through much more quickly than expected. 

Lithium ions stood out in particular, moving about 31 times faster than predicted. The results also showed strong selectivity, with lithium ions traveling through the channels significantly faster than other types of ions.

Electric eel-inspired system turns ion flow into usable energy 

To demonstrate the potential of the system, Kim and his team showed that the small membranes could generate enough energy from salt solutions to power simple electronic devices. Kim noted that they were able to operate a watch and a calculator using this approach. 

The concept of producing electricity from ion movement is not new, and as Kim explained, electric eels use a similar principle in nature, generating electrical bursts by controlling ion flow across specialized cells known as electrocytes.

Electrocytes rely on ion channels to convert chemical gradients into electrical energy, a natural process that has long inspired efforts to replicate similar mechanisms in engineered systems, including the membranes developed in this study.

Going forward, Kim and his team aim to explore additional applications for the technology, with a particular focus on the nanotubes’ ability to separate lithium. He noted that the findings could potentially be used for lithium recovery from waste batteries, with the team also planning to investigate the underlying physics in more detail to better understand what drives the unusually fast ion transport observed in the system.