This is a schematic of the structural evolution of titanium disulfide at different stages of intercalation. Interlayers are expanded or distorted as different amounts of pillaring molecules, complex cations and solvents are intercalated into the van der Waals gap of a host material at each stage. Source: The University of Houston, Department of Electrical and Computer Engineering
Researchers at the University of Houston have found a new design for the cathode of magnesium batteries that increases its storage capabilities.
Magnesium batteries are safer than lithium-ion batteries, but up until today, they had limited storage. A better-designed cathode—the electrode from which the current flows—and better electrolytes, the medium that carries the electrical signal from cathode to anode, could make magnesium batteries an alternative to the expensive and dangerous ion-lithium batteries.
According to Yan Yao, an associate professor of electrical and computer engineering at the University of Houston and the leader of the research group, the new design of the cathode allows for the increase in storage capacity of the battery by inserting magnesium monochloride into a titanium disulfide host. This process provides a much faster diffusion than in traditional magnesium batteries. In turn, faster diffusion allows the longer retention of charge.
"We are combining a nanostructured cathode and a new understanding of the magnesium electrolyte," said Yan Yao.
"Magnesium ion is known to be hard to insert into a host," said Hyun Deog Yoo, a post-doctorate student working with Yan Yao. "First of all, it is very difficult to break magnesium-chloride bonds. More than that, magnesium ions produced in that way move extremely slowly in the host. That altogether lowers the battery's efficiency."
The new battery has a storage capacity of 400 mAh/g. Compared with the top capacity of a standard lithium-ion battery of only 200 mAh/g, this makes the new battery really desirable. However, its voltage is relatively small—only about one volt—compared with the three to four volts of the lithium battery. So, there is still work ahead for the researchers.
It is important to understand why magnesium batteries—as well as Cobalt batteries—could be a solution to the problems with lithium batteries. Lithium is very expensive and can develop the so-called dendrite growths (breaches in its internal structure) that cause the battery to catch fire.
The results of the study are published in the journal Nature Communication. An abstract can be found here.
