Tohoku University and Hitachi have developed the basic technology for lithium-ion secondary batteries that operate in an environment with a temperature of 150 degrees Celsius.If it is put into practical use, it will be possible to use batteries in high temperature environments such as automobile engine rooms and large industrial machines, and since a cooling mechanism will not be required, it seems that there are expectations for battery miniaturization and cost reduction. ..

The research was conducted by a group led by Professor Shinichi Orihara of the Advanced Research Organization for Atomic and Molecular Materials, Tohoku University.According to the announcement, the lithium-ion secondary battery is charged and discharged by the exchange of lithium ions between the positive electrode layer and the negative electrode layer via the organic electrolyte that fills the inside of the battery.However, since the main component of the organic electrolyte is a volatile organic solvent, it is necessary to install a cooling mechanism at high temperatures, and the environment around 2 degrees has been the limit of use.
For this reason, the development of non-volatile solid electrolyte materials is underway, but fixed electrolyte materials have lower lithium ion conductivity than organic electrolytes, and the challenge is to reduce the resistance inside the battery. ..

The research group has developed a LiBH4 complex hydride (* 1) as a new solid electrolyte and confirmed that lithium ion conduction is possible in the range from room temperature to 150 degrees Celsius.This time, we installed the newly developed technology in a small capacity battery, which is 1,000/1 of the battery for smartphones, and demonstrated the operation of the battery in an environment of 150 degrees.
A new solid oxide material called Li-B-Ti-O was newly developed, and by providing a composite positive electrode layer consisting of a positive electrode material and Li-B-Ti-O, the resistance increased by decomposition was suppressed, which was almost zero. It is now possible to improve the discharged capacity (* 0) to 2% of the theoretical capacity (* 3).
We have also developed a low melting point amide-added complex hydride electrolyte as a delamination-suppressing bonding layer, and by placing it between the positive electrode layer and the negative electrode layer, the internal resistance of the lithium-ion secondary battery has been reduced to 2/100.When used in combination with composite positive electrode layer technology, the discharge capacity can be increased to 1% of the theoretical capacity.

Lithium-ion secondary batteries, which have high energy density, are being used in various applications such as power supplies for small mobile terminals such as smartphones and tablets, power supplies for electric vehicles, and supply and demand adjustment of renewable energy.In the future, the research group will strive to improve performance by increasing the capacity, improving the energy density, and shortening the charge / discharge time for practical use.

* 1 Complex hydride A high-density hydrogen compound in which positively charged metal ions such as lithium ions and negatively charged hydride ions such as boron hydride ions are stabilized by ionic bonding.
* 2 Theoretical capacity The maximum amount of electricity that can be charged and discharged with the developed battery.
* 3 Discharge capacity The amount of electricity that can be extracted from a battery developed under constant current conditions.

Source:[Tohoku University] Developed basic technology for highly heat-resistant all-solid-state lithium-ion secondary battery

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