This week’s Essential Science column looks at some new research into batteries from University of Texas at Dallas. The research promises to cut battery production costs as well as offering performance improvements. The direction taken is away from lithium-ion technology.
Lithium-ion batteries
A lithium-ion battery is a type of rechargeable battery. The basis of the chemistry is that lithium ions move from a negative electrode to a positive electrode during discharge; and in the opposite direction when charging. The electrodes of a lithium-ion battery are made of lightweight lithium (for the cathode) and carbon (graphite, for the anode). When a lithium battery is charged and discharged once, it is called a cycle. Lithium battery capacity degrades as the cycle number increases.
Lithium-ion batteries are common in most home electronics. While they have reasonable energy density and low self-discharge they cause frustrations for consumers due to the regular need to recharge. They are also limited by not being flexible (something which hampers developments in the wearables market). These batteries are also, occasionally, associated with accidents like catching fire.
The new approach from The University of Texas at Dallas is to look at manganese and sodium-ion-based materials. In terms of future application, the manganese and sodium-ion-based materials could prove useful might as an ecofriendly option for various next-generation devices plus, on a larger scale, electric cars.
Electric cars present some of the biggest challenges as they are set to be one of the biggest technological growth areas. Based on a recent report by the International Energy Agency, there could be upward of 20 million electric cars worldwide by 2020.
The university has worked with the new materials in collaboration with Seoul National University. As well as performance a key consideration is with lowering production costs. The reason why costs would decrease is because sodium is more abundant than lithium.
A further concern is with the ability of lithium production to keep up with the increasing demand for materials for batteries. This becomes harder as some applications become bigger, such as electric cars. Lithium ion batteries used for electric vehicles are affected by high temperatures; overcharging or high voltage; deep discharges or low voltage; and high discharges or charge current. Each one of these factors leads to a shortening of the battery life.
However, not all is straightforward since sodium use brings with it other issues. Dr. Kyeongjae Cho, who led the investigation into the sodium alternative told Controlled Environments: “Unfortunately, although sodium-ion batteries might be less expensive than those using lithium, sodium tends to provide 20 percent lower energy density than lithium.” The energy density, or energy storage capacity, of a battery determines the run time of a device.
Nevertheless a new design is proving effective in trials. With the design, sodium replaces most of the lithium in the cathode. This construct has proved to be more stable; the good news is that the battery maintains the high energy capacity of lithium. The next step is to reproduce this on a larger scale.
Scale-up will first be computer modeled, using computer simulations to determine the configuration of atoms that appear to work best. The research to date has been published in the journal Advanced Materials. The research paper is titled “Rational Design of Na(Li1/3Mn2/3)O2 Operated by Anionic Redox Reactions for Advanced Sodium-Ion Batteries.”
Essential Science
This article is part of Digital Journal’s regular Essential Science columns. Each week Tim Sandle explores a topical and important scientific issue. Last week we looked at why space researchers are spending so much time and resources studying and identifying microbes onboard the International Space Station. The week before we looked at the remarkable ability of pythons to regenerate their organs and inquired whether this could aid human artificial organ development.
