A few days ago, we talked about vanadium-borate electrodes that can potentially double the battery life of Li-ion units. Well, this time around, researchers at the University of Michigan have arguably made a more pragmatic breakthrough with their Kevlar nanofibers that can prevent Li-ion batteries from catching fire. In a conventional scenario, such fire-catching incidences can only occur when metallic crystals known as dendrites (with their tree-like patterns) form between two electrodes of a battery. The Kevlar in turn has the ability to mitigate such formations by simply blocking the passage of the dendrite tip.
In a more exhaustive explanation, the working scope of a lithium-ion battery entails the passing of the namesake lithium ions between the two electrodes. This passage is generally created from a ultra-thin micro-perforated plastic membrane (with insulation) that shields the electrons from travelling through it. So, these electrons make their way through the circuit, which in turn pertains to causing of an electrical current by the collective process.
However, the predicament with such a setup relates to the propensity of the lithium ions to form dendrites (basically, crystal growth) after a number of charge/discharge cycles; and these crystals generally expand on the surface of an electrode. And in case, the pores of the aforementioned plastic membrane gets too big, the dendrites make their way into the other electrode, thus creating a path for the electrons to travel. This in turn causes a short circuit which leads to the internal heating up of the battery.
Now, the solution in question here encompasses the use of Kevlar nanofibers for the insulated plastic membrane. Such a design consideration allows for far smaller pores in the separator, within a range of just 15 to 20 nm (as compared to regular pores that extend beyond hundred nanometers). Still the perforations remain small enough to ‘filter’ the lithium ions, while feasibly obstructing the over-20 nm thick dendrite tips. In essence, the membranes can be manufactured with thinner cross-sections – thus ultimately translating to slimmer batteries with higher energy densities. Moreover, Kevlar is known to be both insulative and heat resistant – advantageous qualities that might play their safety-oriented roles in case of fires breaking out inside the battery.
Lastly, coming the commercial side of affairs, the team at University of Michigan has already formed a spin-off startup named Elegus Technologies, and they expect to start mass-scale production of the tech by end of 2016.
Image Credits: Joseph Xu, Michigan Engineering, Communications & Marketing