Kinichi Adachi

Developing stable, low impedance interface between metallic lithium anode and polyacrylonitrile-based polymer gel electrolyte by preliminary voltage cycling

Abstract The metallic lithium anode surface facing to a gel-like polyacrylonitrile polymer electrolyte (gel-SPE) was tried to be stabilized by preliminary voltage cycling. Through voltage cycling from +0.5 to −0.5 V at a scan rate of 10 mV/s at 20°C immediately after assembling a cell having a configuration of Li/gel-SPE/Li, the cell impedance at 100 Hz was kept below 100 Ω for the cells with a gel-SPE containing LiBF 4 over 230 days at 20°C. The cells with a gel-SPE containing LiPF 6 required preliminary voltage cycling at a voltage higher than 0.5 V and at an elevated temperature of 60°C to obtain and keep a lower impedance during storage. The impedance at 10 kHz which represented the bulk resistance of gel-SPE was almost the same for both cells and constant during storage, around 15 Ω. This was confirmed in the cell of Li/gel-SPE/DMcT+polyaniline composite cathode (DMcT=2,5-dimercapto-1,3,4-thiadiazole). The metallic lithium anode surface before and after the voltage cycling was subjected to X-ray photoelectron spectroscopy (XPS) analysis: Li 2 CO 3 disappeared and LiF–LiOH remained in the surface layer after the voltage cycling for the LiBF 4 gel-SPE cell while for the LiPF 6 gel-SPE cell, a dense and thin LiF surface layer was broken into a thicker LiF–LiOH layer. The layer consisting of mainly LiF and LiOH which was formed by preliminary voltage cycling was considered to stabilize the interface.

Progress in materials applications for new-generation secondary batteries

The status of research and development on advanced batteries in Japan is reviewed. The three types of batteries attracting the most interest are: (1) nickel-metal hydride batteries, (2) secondary lithium batteries, and (3) secondary batteries using solid electrolytes. The advances made in the development of these batteries are described from the viewpoint of the application of new materials. The materials used for batteries come from multidisciplinary research. Hydrogen-storage alloys and conducting polymers are examples of materials with interdisciplinary origins. >