In life, we are inseparable from batteries. Batteries also vary in size, ranging from large batteries that can support the driving of electric vehicles to button batteries that can be tucked into watches.
How small have you ever seen the smallest battery?
Recently, a research team from the Chemnitz University of Technology in Germany and the Changchun Institute of Applied Chemistry of the Chinese Academy of Sciences has worked together to develop the smallest micro-battery to date, which is smaller than a grain of salt, can power the world's smallest computer chip for about 10 hours, and can be recharged repeatedly.
The world's smallest miniature battery (Image source: Reference)
How does the battery work?
We can think of a battery as a multilayer sandwich, two electrodes store electrical energy in the form of chemical energy, between the two poles, the electrolyte guides the flow of charge, and then the two metal collectors on the electrode direct the current to the external circuit. The smaller the electrode, the less charge it can hold, and cracks and other defects can prevent the charge from flowing, and the twist channels of ions and electrons in the thick layer of material increase the resistance, causing power loss.
Button cell battery structure (image source: self-translation)
The key to the development of micro batteries is twofold: small and fine. Small, refers to the small size; fine, refers to the battery has sufficient energy density, which is particularly demanding on the production process.
The production technology of micro batteries is very different from the battery manufacturing technology used on a daily basis.
Coin cell batteries with high energy density are manufactured using wet chemistry, the electrode material and additives of the battery are coated on the metal foil, the electrolyte film is sandwiched between the electrodes, and the electrode thickness reaches 100 m. This manufacturing method produces battery electrodes that are too thick, and the allowable electrode thickness of the chip is a few microns, and the amount of charge that can be accommodated is also limited. This poses a huge challenge to the process and performance of miniature batteries.
In order to achieve the goal of small and fine micro batteries, the team adopted the "Swiss roll" process. "Swiss rolls", as the name suggests, roll up the battery layer by layer like a Swiss roll.
Topography of the Swiss volume (Image: Veer Gallery, References)
The "Swiss coil" process creates a layering system with tension through the coating of different films, and this tension is like the energy brought by the spring inside the steel tape, which is released by the film automatically rolling into the Swiss coil structure, so no external force is required to build this spontaneously winding cylindrical miniature battery.
Miniature batteries with a standard "Swiss coil" structure have at least five layers: two collector layers, a cathode membrane, an anode membrane and an electrolyte membrane. Such a complex overlay places extremely high demands on the production process. In addition, the "Swiss coil process" has very high requirements for the toughness of the film, and it is also necessary to avoid problems such as battery short circuits caused by the roll-up process.
Swiss volume (Image source: self-translation)
Micro batteries have great potential and are expected to play a role in the fields of Internet of Things and micro medical implants.
Producer: China Science Expo
Author: Sasha
The article only represents the views of the author and does not represent the position of the China Science Expo
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