Does carbon nanotube anode reduce risk?

Well, in lithium-ion batteries.

Lithium batteries are currently a hot topic in the industry, particularly in the electric vehicle (EV) sector. The development and the research work with lithium batteries are outshining the growth, and the focus is mainly on the improvement of the lithium batteries and making them cheaper to reduce the overall cost of their usage.

In Nano Letters, the researchers from Texas A&M claim that,

“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 graduate 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.”

One of the most commonly used anode materials is graphite, where lithium ions are inserted between layers of graphite.

Noh mentioned that the design limits the number of lithium ions to be stored within the anode and also requires major energy for removing the ions from the graphite during charging.

The lithium ions can accumulate on the anode’s surface to form dendrites. The dendrites are eventually growing and piercing through the material, separating the battery’s two compartments, with a breach causing the battery to short circuit and cause a fire.

The batter’s performance is also affected by the dendrites consuming lithium ions, rendering it unavailable for generating a current. 

Another sort of anode design involves the use of pure lithium metal in place of graphite as compared to graphite anodes. The lithium metal offers a much higher energy content per unit mass or energy density, and it can fail in the same catastrophic way due to dendrites.

Highly conductive lightweight carbon nanotubes are used for designing the anodes, with carbon nanotube scaffolds containing pores for lithium ions to enter and deposit, but structures can bind the lithium ions favorably.

Two types of experiments were conducted with carbon nanotube anodes. One of the teams made a type of carbon nanotube anode with a slightly different surface chemistry: one laced with an abundance of molecular groups to bind the lithium ions and another with the same molecular groups but in a smaller quantity. The anodes are also built with batteries to test the propensity to form dendrites.

The researchers also found out that scaffolds can meet with just carbon nanotubes and it is not bind with lithium ions as well, There was almost no dendrite formation, but the battery can produce large currents as it was compromised.

The scaffolds bind with excess molecules forming many dendrites, which can shorten the battery’s lifetime.

The carbon nanotube anodes are designed with an optimum quantity of the same binding molecules preventing the formation of dendrites. In addition, the binding of a vast quantity of lithium ions is possible to spread along the scaffold’s surface, thereby boosting the battery’s ability to produce large, sustained currents.

As Noh said in a statement, “When the binding molecular groups are abundant, lithium metal clusters made from lithium ions end up just clogging the pores on the scaffolds.” “But when we had just the right amount of these binding molecules, we 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.”

The researcher mentioned that the top-performing anodes can handle currents at five times more speed than commercially available lithium batteries. The feature is also useful for large-scale batteries, such as those used in electric cars, requiring quick charging.

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

Source:- The engineer