In this paper, the electrochemical properties and performances of all-solid-state lithium polymer batteries (LPBs) using standard PEO-based solid-state polymer electrolytes (SPEs) are reported and discussed. The assembled cell showed stable charge–discharge cycles (>150 cycles) at 30 °C. This is due to desirable solid electrolyte interface (SEI) film formation at the SPE | cathode interface at the first cycle indicated by activation energy measurements for interfacial Li ion exchange reaction. However, sudden capacity fading for prolonged electrochemical cycles was indicated by an accelerated aging test at higher current density (1 C) and temperature conditions (60 °C), accompanied by an increase of electrochemical polarization. This degradation phenomenon may be fatal for practical usage of large-scale batteries which requires extremely long-time durability. Two sequential factors affecting the capacity fading are proposed through the studies of in situ¹⁹F-NMR imaging, real-time monitoring of the total cell thickness, and electrochemical measurements such as AC impedance. One factor is degradation of the cathode sheet or cathode composite assembly, owing to cyclic volumetric change from the two-phase LiFePO₄–FePO₄ reaction. Such degradation leads to uneven electric contact at the electrode | electrolyte interface, thereby enhancing local electrochemical polarization. The second factor, namely, Li salt decomposition, is triggered by this local polarization, giving rise to the continuous capacity fading and the increase of polarization. This degradation scenario can be general enough to include the full range of all-solid-state LPB devices, since the trigger of degradation owes to non-fluidity of solid | solid contact, or solid electrolytes cannot immerse into the cavities caused by pulverization of cathode particles unlike liquid electrolytes. On the basis of these results, we attempted to improve the mechanical properties of the binder materials of cathode sheets, and demonstrated improved cyclic durability.

Novel surface-enhanced Raman scattering (SERS) substrates with high SERS-activity are ideal for novel SERS sensors, detectors to detect illicitly sold narcotics and explosives. The key to the wider application of SERS technique is to develop plasmon resonant structure with novel geometries to enhance Raman signals and to control the periodic ordering of these structures over a large area to obtain reproducible Raman enhancement. In this work, a simple Ar⁺-ion sputtering route has been developed to fabricate silver nanoneedles arrays on silicon substrates for SERS-active substrates to detect trace-level illicitly sold narcotics. These silver nanoneedles possess a very sharp apex with an apex diameter of 15 nm and an apex angle of 20°. The SERS enhancement factor of greater than 10¹⁰ was reproducibly achieved by the well-aligned nanoneedles arrays. Furthermore, ketamine hydrochloride molecules, one kind of illicitly sold narcotics, can be detected down to 27 ppb by using our SERS substrate within 3 s, indicating the sensitivity of our SERS substrates for trace amounts of narcotics and that SERS technology can become an important analytical technique in forensic laboratories because it can provide a rapid and nondestructive method for trace detection.