Chemist wants to counter fire risk of lithium-ion batteries with silica in electrolytes

Oak Ridge National Laboratory chemist Gabriel Veith argues that silica nanoparticles in the electrolyte can reduce the fire and explosion hazard of lithium-ion batteries. This would partly eliminate an important disadvantage of this type of batteries.

At the summer conference of the American Chemical Society, Veith suggested using silica powder to make the electrolyte in lithium-ion batteries more resistant to fire. Silica, or silicon oxide, is added to the electrolyte. For example, if a battery takes a hard fall, the silica causes the electrolyte to harden. This prevents the positive and negative electrodes from coming into contact with each other. Electrolyte is the liquid that ensures that the ions in a battery can move and that there is a power supply.

To make electrolytes impact-resistant, Veith wants to use perfectly spherical particles of silicon oxide with a homogeneous diameter of 200nm. In essence, that is super fine sand. Because they are so homogeneous and small, these particles can be mixed well with liquid electrolytes used today. According to the chemist, the homogeneity of the particles is crucial, because otherwise the liquid of the electrolyte becomes less viscous. On impact, the silica particles clump together, blocking the movement of ions and the liquid.

According to the chemist, adding silica only requires a minor adjustment to today’s conventional battery manufacturing process. In theory, this makes it a relatively cheap way to produce more fire-safe batteries. He suggests first applying the silica during production and only then adding the electrolyte. When the powder is mixed with the electrolyte, the electrolyte immediately solidifies when it is injected into the battery. Veith has applied for a patent on this manufacturing technology.

There are already other labs that have studied somewhat similar uses with silica; irregularly shaped or rod-shaped silica particles have been used. Veith thinks it might be easier to make his spherical particles. In addition, he thinks that his particles react faster to an impact and therefore have more stopping power. Scientists have also been working on developing solid-state batteries for some time, which do not use liquids. They are therefore safer and also have higher energy capacities, but for the time being it is difficult to produce this type of batteries cheaply and on a large scale.

In theory, there is always a risk of fire with lithium-ion batteries if they are subject to an impact, for example if they are damaged or if they are not properly packaged. If this causes the anode and the cathode to contact each other, a short circuit will occur. The temperature can then rise quickly, causing the electrolyte to catch fire. The temperature then keeps getting higher, after which the battery can even explode because the pressure becomes too high. For example, a design flaw in the batteries of the Samsung Note 7 smartphone led to a relatively large number of phones catching fire.

Veith came up with this idea while playing with cornstarch and water in the kitchen with his kids. This suspension of starch in water is also called oobleck. In a resting state the substance is liquid, but as soon as you give the surface on which the substance lies, it becomes a solid due to the increasing pressure. For example, it can be kneaded into balls very well, but at rest it becomes liquid again.

Ultimately, he wants to further develop his system so that only the damaged part of a battery hardens, while the rest of the battery continues to work. The researcher and his team initially want to apply this battery technology in drones, but eventually they also see opportunities for the car market. Veith also thinks that the addition of silica will enable larger batteries to be made that are so strong that they can serve as bullet-proof vests. According to him, this can significantly reduce the weight that soldiers have to carry around on a mission, because then it is no longer necessary to carry separate, extra batteries.