All-solid-state lithium batteries have become a new upsurge in the field of material science and engineering

All-solid lithium batteries have become a new boom in material science and engineering, because traditional lithium-ion batteries can no longer meet the standards of advanced technologies, such as electric vehicle —— electric vehicles need to meet conditions such as high energy density, fast charging and long cycle life.All-solid-state batteries use a solid electrolyte instead of the liquid electrolyte in traditional batteries, which not only meets the above standards, but also is relatively safer and more convenient.

However, solid electrolytes also have problems that are difficult to overcome.It turns out that a large resistance occurs between the positive electrode and the solid electrolyte, and the origin is less clear.Furthermore, when the electrode surface is exposed to air, the resistance increases and the battery capacity and performance decrease.While some attempts have been made to reduce the resistance, no one was able to reduce it to 10 Ω cm2 —— to the value of resistance when not exposed to air.

Now, in a recently published study in ACS Applied Materials and Interface, a research team led by Professor Taro Hitosugi from Tokyo University of Technology, Japan, and Shigeru Kobayashi, a PhD student at Tokyo University of Technology, has finally addressed the problem.

First, the team prepared a thin-film battery composed of a lithium anode, a lithium cobalt acid cathode, and 3PO4 of a solid electrolyte.The team exposed the lithium cobalt acid surfaces to air, nitrogen, oxygen, carbon dioxide, hydrogen, and water vapor for 30 minutes before completing the battery manufacturing.

To their surprise, they found that batteries exposed to most of the gas did not reduce battery performance when compared to unexposed batteries.Only water vapor increases the battery resistance value sharply, more than 10 times higher than the unexposed resistance value.

The team then conducted a process known as " annealing (Annealing), in which the sample battery was heat-treated for an hour at 150°C.Surprisingly, the process reduced the resistance to 10.3 Ω cm2, comparable to the unexposed battery resistance.

By performing numerical simulations and measurements, the team subsequently found that this reduction was attributable to the spontaneous removal of protons from the LiO 2 structure during annealing.The scientists said: " Our study shows that the protons in the lithium-cobalt acid structures play an important role in reducing the resistance.We hope that the elucidation of these microscopic processes will help to broaden the application potential of all-solid-state batteries.