The United States develops 32700 battery that are collision-proof and fire-proof and can change when used in the presence of external forces

Whether it is a laptop computer spontaneous combustion or a smartphone explosion, these 3C accidents seem to point directly to the failure factors of lithium-ion batteries, causing many people to start worrying about whether their mobile phones have hidden explosion risks. In order to reduce public concerns, many scientists have now invested in battery explosion-proof technology. For example, the Oak Ridge National Laboratory (ORNL) in the United States guarantees that its batteries will not catch fire due to impact. On the contrary, the liquid electrolyte in it will harden and prevent the battery from deforming and exploding.

Lithium-ion batteries are the leader in energy storage technology. They are mainly composed of positive electrodes, negative electrodes, isolation membranes and electrolytes. Lithium ions migrate between the two ends of the electrodes through electrolytes. The main function of the isolation membrane is to isolate the positive and negative electrodes, prevent battery self-discharge and short circuit between the two poles, but as long as they are impacted or hit, they may cause the battery to short-circuit or explode.

At present, scientists have proposed solutions such as solid electrolytes, but solid-state batteries are expensive and less stable, and manufacturers have to greatly change the battery production process. Therefore, the Oak Ridge National Laboratory in the United States has developed a low-cost and practical battery that becomes harder when impacted.

The team was inspired by the children's toy "Oobleck", which at first glance is just a plastic toy filled with corn starch solution, but it hardens if you slap or hit it. If you want to experiment further at home, you can also pour corn starch and water into a basin, stir evenly, and then you can stand directly on the "water surface" or even jump on it without sinking into the water.

Adding powdered silicon dioxide (blue container) to the polymer layer (white sheet) of the electrode in the separated test battery (gold bag) will prevent lithium-ion batteries from catching fire. (Photo from: Gabriel Veith)

This liquid is a "shear thickening fluid" in the category of non-Newtonian fluids. It can remain liquid under normal conditions. When it is impacted or stressed, the liquid structure changes, and the viscosity, hardness and volume will increase, which can greatly reduce the risk of deformation of the battery and electrodes.

However, the team certainly did not add corn starch to the battery. They added silica to the electrolyte to achieve a similar effect. Gabriel Veith, the head of the research, said that the battery electrolyte will solidify when it is hit, which can prevent the electrodes from being damaged in the battery fall and impact. If the electrodes cannot contact each other, the battery will not easily catch fire. And the advantage of this technology is that manufacturers only need to fine-tune some of the battery processes.

The traditional battery process is to inject electrolyte and encapsulate it after the battery is completed, but if shear thickening fluid technology is used, the electrolyte may begin to solidify during the injection, so the research first puts silica particles into the battery and then adds electrolyte.

Veith pointed out that the research used silica particles with a diameter of about 200 nanometers. If these particles are of similar size, they can be evenly distributed in the electrolyte; if the particle sizes are different, the electrolyte will not become sticky when the battery is hit.

In order to make batteries safer and more practical, many teams are developing silica shear thickening fluid batteries in full swing, but Veith believes that the team's new silica particles are better than previous research in terms of ease of manufacturing, resistance, reaction force and other performance.

In the future, the team will continue to improve battery performance, hoping that the battery can continue to operate after being damaged by an impact. At present, the technology will first be applied to drones, and the ultimate goal is to be used in electric vehicles. The team also built bulletproof batteries for American soldiers. Veith said that the average American soldier carries 8 kilograms of batteries and bulletproof vests every day. If the battery can be used for bulletproof, the soldier will be able to reduce the burden of 8 kilograms.

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