Japan develops safer and more efficient solid-state lithium batteries

Although lithium batteries using solid electrolytes are safer and more energy dense than lithium batteries using liquid electrolytes, they suffer from problems such as low conductivity and insufficient electrode contact. Japan has newly developed a stable, highly conductive solid electrolyte that is expected to solve the shortcomings of all-solid lithium batteries and replace the use of liquid electrolyte lithium batteries.

A lithium battery containing "sulfide-based solid electrolyte (LGPS)" developed by scientists has high room temperature conductivity comparable to liquid electrolyte (LOE) lithium batteries, making this all-solid-state battery (ASSB) widely studied.

This kind of lithium battery has safety advantages such as being non-flammable, non-explosive and resistant to high temperatures. However, the sulfide in it easily reacts with moisture in the air to form toxic hydrogen sulfide (H2S). Although the ASSB battery subsequently developed by scientists has partially improved the problem of hydrogen sulfide, it still has the problem of insufficient conductivity. Therefore, the mainstream lithium batteries in the market are still dominated by liquid electrolytes.

At present, a team from Tokyo University of Science (TUS) in Japan, which has a history of more than 140 years, has discovered that a new type of "pyrochlore-type oxyfluoride" can be used as a lithium conductor to improve the cycle performance and high-speed charge and discharge of ASSB batteries. Capability and stability are expected to pave the way for the development of safe and advanced ASSB.

This pyrochlore-type oxyfluoride is an octahedral polycrystalline material composed of lithium (Li), lanthanum (La), niobium (Nb) or tantalum (Ta), oxygen (O) and fluorine (F). . It remains stable even in air and performs better at room temperature (25°C) than any previous oxidized solid electrolyte specifically designed for lithium batteries.

Experimenters used the above elements to make three types of pyrochlore-type oxyfluoride, and conducted a series of instrumental analyzes and experimental comparisons on them.

They found that lithium batteries made of this material do not have the risk of electrolyte leakage due to damage like existing lithium batteries, nor do they have the risk of producing toxic gases like sulfide-based batteries. It can be said to be a stable lithium battery. Therefore, it is very suitable for use in aircraft, electric vehicles and other places with high safety requirements.

Lithium batteries made of this material have an operating temperature of -10°C to 100°C, which is much wider than the operating temperature of traditional lithium batteries of 0°C to 45°C. It is considered a promising battery and may be used in the future. Household appliances, medical equipment and other miniaturized equipment.

Professor Kenjiro Fujimoto of Tokyo University of Science told the school’s newsroom, “Making better all-solid-state secondary (rechargeable) lithium batteries has been a long-standing dream of many battery researchers. This time we found this A pyrochlore-type oxyfluoride solid electrolyte, which is a key component of current all-solid-state secondary lithium batteries.”

He continued, "This solid-state lithium battery has high energy density and high stability, can be said to be very safe, and has higher ionic conductivity than previous oxide solid electrolytes. I believe that this solid electrolyte is expected to be developed into A revolutionary battery that should meet the current battery needs of electric vehicles.”