Japan realizes the use of 3D printing to manufacture all-solid-state batteries
Tohoku University professor Honma and assistant Kobayashi Hiroaki and others have developed the technology of making all-solid-state batteries with 3D printers. Use materials that can freely change hardness when crafting. Batteries can be made in just a few hours without the high-temperature processes required in the past. The trial-produced battery has withstood various performance tests and has certain performance, which is expected to contribute to the early practical application of all-solid-state batteries.
The electrolyte is one of the important components of the battery and is usually in a liquid state, but the electrolyte of an all-solid-state battery is solid, and the risk of fire accidents is small. Another feature of this type of battery is that it can increase the storage capacity per unit volume by stacking batteries. It is highly anticipated as a next-generation battery that can extend the cruising range of pure electric vehicles (EVs).
The developed electrolyte membrane has the same softness as a soft contact lens (image courtesy of Kitto University, Japan)
The mainstream of all-solid-state batteries is to strongly press the electrodes and electrolyte materials, and heat them to hundreds of degrees Celsius. However, the heating process is costly, and there is a case of thermal cracking. At the same time, there is still a problem. Due to the hardness of the electrolyte, when the positive electrode and the negative electrode repeatedly expand and contract with charging and discharging, the two cannot be closely attached, resulting in poor battery performance.
The research team carried out research on the fabrication of flexible electrolyte membranes for all-solid-state batteries. When a special liquid that facilitates the movement of lithium ions is mixed with silicon oxide, a glass film similar to a soft contact lens can be formed. The softness can be adjusted simply by changing the amount of silica.
This time, the research team halved the amount of silicon oxide contained in the electrolyte membrane, making it gel-like. It is then mixed with a resin that solidifies when exposed to ultraviolet light, and can be shaped using a 3D printer.
Reduce the concentration of silicon oxide in the electrolyte to make the electrolyte gel-like, and manufacture the battery through a 3D printer (image courtesy of Tohoku University, Japan)
Experiments have confirmed that by changing the electrolyte, lithium cobalt oxide for the positive electrode, lithium titanate for the negative electrode, etc. into gel-like materials, the battery can be made by a 3D printer alone. It is said that it can be produced in about two hours.
It can be made by simply coating the material and irradiating it with ultraviolet rays without heating at high temperature, which can greatly reduce the manufacturing cost. The flexible electrolyte is less prone to cracking and fits softly even as the member expands and contracts.
The trial-produced battery can be stably charged and discharged for more than 100 times. Safety has also been confirmed by fire tests, etc. Professor Honma said, "As long as the data is input, the size and shape can be changed at will."
The problem facing practical application is that the ionic conductivity of the electrolyte is not high enough. Since lithium ions cannot move smoothly, it is difficult to release huge amounts of energy in an instant.
The research team will adjust the composition of the material with the goal of improving ionic conductivity. Experiments with the developed battery-powered car have been successful, reaching a top speed of 30 kilometers per hour. The researchers will make iterative improvements to increase the output power and consider installing it on pure electric vehicles. We will also vigorously develop cathode materials with high energy density.
The goal of the first stage is to realize practical application in the power supply of sensors and wearable terminals.
