Tin recharged

2019-08-23T10:48:23+00:00 August 23rd, 2019|Mining in Focus|

Tin mining projects in the DRC and Namibia will benefit from new research by an engineering company in Australia, writes Syl Kacapyr.

The development of next-generation rechargeable batteries that store more energy and last longer has been stifled by an electrochemical challenge. Australian engineering company, Cornell engineers, has come up with a simple but clever solution to the problem.

Lithium-ion batteries, like those used in cellphones and electric vehicles, are limited in their electric-charge capacity because of their graphite anodes. Researchers have sought anodes made from alkali metals such as lithium and sodium because they allow for greater capacity, but alkali metals are highly reactive with traditional battery electrolytes. This can lead to the formation of dendrites – pointy metallic structures that make the battery susceptible to a shorter lifetime and potentially dangerous short-circuiting.

Tin as an interface

A team of engineers working in the lab of Lynden Archer, professor of chemical and biomolecular engineering, and director of the Cornell Energy Systems Institute, has demonstrated a cost-effective way to stabilise lithium and sodium anodes using tin as a protective interface between the anode and the battery’s electrolytes.

The research is detailed in a paper titled, ‘Fast ion transport at solid-solid interfaces in hybrid battery anodes’, published in Nature Energy in March this year. By dropping tin into a battery’s carbonate-based electrolyte, the research team found that an artificial interface instantly forms on the alkali-metal anode, creating a nanometer-thick barrier that protects the anode like a shield, while keeping it electrochemically active.

 AfriTin’s project in Uis has started producing. Image credit: Leon Louw

AfriTin’s project in Uis has started producing. Image credit: Leon Louw

Cryo-microscopy performed in the lab of Lena Kourkoutis, assistant professor of applied and engineering physics, revealed that the technique produced dendrite-free batteries. Zhengyuan Tu, a doctoral student who led the research, says the interface offers several advantages beyond simply stabilising the battery.

“The target was to find a facile process to not only protect the pristine anodes, but to also be able to store additional energy,” says Tu. “Tin and other elements have long been exciting candidates for energy storage by readily forming alloys with lithium, so this led us to the concept that a tin interface on lithium would not only offer protection, but added electrochemical activity.”

Prolonging battery life

Unlike other artificial interface materials, tin is easier to apply during the manufacturing process because it requires a minimal amount of specialised equipment and processing, according to Tu.

Testing of the tin interface on a lithium anode revealed a battery life cycle of more than 500 hours at a current density of 3 milliamperes per square centimeter. The test was repeated without the protective interface and the battery lasted just 55 hours.

Alphamin’s Bisie tin project in the DRC is coming online later this year. Image credit: Leon Louw

Alphamin’s Bisie tin project in the DRC is coming online later this year. Image credit: Leon Louw

The research team reported that the source of the improvements was the ability of lithium to rapidly alloy with tin, which facilitated more uniform lithium deposition when the anode was recharged. Dendrite-free performance was observed in a variety of other experiments, including the use of a high-loading cathode material with the battery. The tin interface was also evaluated using a sodium anode, notorious for its high reactivity and propensity to form dendrites.

An enhancement in lifetime from less than 10 hours to more than 1 700 hours was observed at moderate current density.

“Lots of effort has been devoted to developing sodium-ion batteries because sodium is cheaper than lithium,” says Tu. “Although sodium-related battery technology is still in the early stage, it is a part of the metal-based battery family and is recognised to be promising.”

The research team plans to examine their hybrid anode concept to understand the design rules for using electrochemically active metals as artificial interfaces for high-energy alkali metal anodes. They have also begun efforts to optimise their anode design to facilitate larger-scale deployment.

The research was supported by the US Department of Energy’s Advanced Research Projects Agency – Energy, and by the National Science Foundation.

Syl Kacapyr is public relations and content manager for the College of Engineering.