A group of the University of Tokyo Graduate School of Engineering discovered a new category of lithium-ion conductive liquid "normal temperature melt hydrate" based on "water" through joint research with the Science and Technology Agency and the National Institute for Materials Science. ..The research results were published in the electronic version of "Nature Energy".
A storage battery that stores electricity and can be used when needed.In addition to lithium-ion batteries, which are currently considered to be the best, research on next-generation storage batteries such as air batteries and multivalent ion batteries is being actively conducted with the aim of further increasing energy density (smaller and lighter).On the other hand, with the advent of the IoT era where various things such as home appliances and electric vehicles can be controlled via the Internet, the concept of storage batteries is not so much energy density as it is price destruction, super productivity, resources, environment, toxicity, fire, etc. It is shifting toward risk avoidance.
In this trend, the problem is that the organic solvent used for the electrolytic solution in the existing lithium-ion battery is extremely flammable and toxic.Therefore, research on "aqueous lithium-ion batteries" that replace organic solvents with non-combustible, non-toxic, and inexpensive water has been actively conducted in recent years.However, since water is electrolyzed into hydrogen and oxygen even at a low voltage, its performance is inferior to that of a lithium ion battery, and it has not been put into practical use.
In this research group, by mixing water and two specific lithium salts at a fixed ratio, lithium salt dihydrate, which normally becomes a solid, exists as a stable liquid (hydrate melt) at room temperature. discovered.Although this hydrate melt uses water that normally decomposes at a voltage of 2V, it does not decompose even when a high voltage of 1.2V or higher is applied.By applying this hydrate melt as an electrolytic solution, it is the first electrolytic solution using "water" for the reversible operation of an ultra-3V class lithium-ion battery, which was previously possible only with an electrolytic solution using a special organic solvent. Successful.
Replacing the electrolyte of lithium-ion batteries with non-combustible and non-toxic water enables both safe and inexpensive high-performance storage battery device design and production process design.As a result, it is expected to accelerate the development of large storage batteries for electric vehicles and households, which are required to achieve both high safety and low price.
