The structure of the new all-solid-state Li-ion batteries. Image: ACS Applied Materials & Interfaces.
The structure of the new all-solid-state Li-ion batteries. Image: ACS Applied Materials & Interfaces.

Scientists at Tokyo Institute of Technology in Japan have addressed one of the major disadvantages of all-solid-state batteries by developing batteries with a low resistance at the interface between the electrode and the solid electrolyte. The fabricated batteries showed excellent electrochemical properties that greatly surpass those of conventional lithium (Li)-ion batteries, thereby demonstrating the promise of all-solid-state battery technology and its potential to revolutionize portable electronics. The scientists describe the new batteries in a paper in ACS Applied Materials & Interfaces.

Rechargeable Li-ion batteries are now common in all sorts of electronic devices. Despite their broad use, however, scientists and engineers believe that traditional Li-ion battery technology is already nearing its full potential and new types of batteries are needed.

All-solid-state batteries, which utilize a solid rather than a liquid electrolyte, are a new type of Li-ion battery, and have been shown to be potentially safer and more stable energy-storing devices with higher energy densities. But the use of such batteries is currently limited due to a major disadvantage: their resistance at the electrode/solid electrolyte interface is too high, hindering fast charging and discharging.

Scientists from Tokyo Institute of Technology and Tohoku University in Japan, led by Taro Hitosugi, have now fabricated all-solid-state batteries with an extremely low interface resistance using Li(Ni0.5Mn1.5)O4 (LNMO) as the electrode material. By fabricating and measuring their batteries under ultrahigh vacuum conditions, the scientists were able to ensure that the electrolyte/electrode interfaces were free of impurities.

After fabrication, the electrochemical properties of these batteries were characterized to shed light on Li ion distribution around the interface. This involved using X-ray diffraction and Raman spectroscopy to analyze the crystal structure of the thin films comprising the batteries. Spontaneous migration of Li ions was found to occur from the Li3PO4 solid electrolyte layer to the LNMO layer, converting half the LNMO to L2NMO at the Li3PO4/LNMO interface. The reverse migration occurs during the initial charging process to regenerate LNMO.

The resistance of this interface, verified using electrochemical impedance spectroscopy, was 7.6Ωcm2, which is two orders of magnitude smaller than that of previous LMNO-based all-solid-state batteries and even smaller than that of liquid-electrolyte-based Li-ion batteries using LNMO. These batteries also displayed fast charging and discharging, such that half the battery could charge/discharge within just one second. Moreover, the cyclability of the battery was also excellent, showing no degradation in performance even after 100 charge/discharge cycles.

Li(Ni0.5Mn1.5)O4 is a promising material to increase the energy density of Li-ion batteries, because it provides a higher voltage. The research team hopes that these results will facilitate the development of high-performance all-solid-state batteries, which could revolutionize modern portable electronic devices and electric cars.

This story is adapted from material from the Tokyo Institute of Technology, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.