All-solid-state polyvinyl-alcohol-based Li-ion battery fabricated in air and its charge/discharge measurements

A Li-ion battery consists of two active materials, namely positive and negative electrodes, and an electrolyte in contact with both. Because they use both liquid and solid electrolytes, all-solid-state Li-ion batteries, which are composed entirely of solids, are expected to outperform electrolyte-based batteries in terms of safety, lifetime, and power output. In this paper, we propose an experimental material that enables students to fabricate an all-solid-state Li-ion battery in air and evaluate its charge/discharge characteristics using a direct-current (DC) voltage and current source/monitor. Sheets of polyvinyl alcohol (PVA) with 30 wt% Li nitrate (30%LiNO3-PVA) were used as the Li electrolyte. Li cobaltate (LiCoO2) and acetylene carbon black C were used as the anode and cathode, respectively. All-solid-state Li-ion batteries were constructed using 30%LiNO3-PVA sheets and C-30%LiNO3-PVA anodes and LiCoO2-C-30%LiNO3-PVA cathodes placed on either side of the sheets. Using a DC voltage and current source/monitor, good charge/discharge characteristics were obtained after constant-current charging and discharging. A constant-current charge of 5.7 mA cm-2 was applied at room temperature in air for 10 min, achieving a voltage of 3.6 V. During the constant-current discharge of 57 μA cm-2, the voltage was 1.4 V at the start of discharge, and a voltage drop of 2.2 V was observed. Thereafter, stable discharge continued until a voltage of 1.1 V was obtained after 20 min. Thus, a low-cost, safe, and effective all-solid-state Li-ion battery for student experiments was realized.