A high-performing flexible chitosan-based gel electrolyte with poly­(vinyl alcohol) (PVA) additive was prepared and swelled in varying concentrations of potassium hydroxide (KOH) solutions. A highest ionic conductivity of 457 mS/cm was recorded for the sample with a 2.1 swelling ratio, obtained by soaking in a 5 M KOH solution for 45 min. Stability test results demonstrated the prepared electrolyte to be strong and ductile along with stability under 50 °C and 2 V. Zn-EMD batteries were constructed with the prepared electrolyte using an optimized assembly technique employed to achieve good interfacial contact between the layers. Continuous charge–discharge tests were performed on the batteries at a current density of 0.1 A/g in specific limited and extended potential regions (low: 0.4–1.2 V and high: 0.4–1.6 V) to explore their performance and reversibility. Results indicated that the batteries cycled in the low region had higher capacity retention due to lower δ-MnO2 formations when compared to those in the high region cycling. To fully understand its performance capability, the battery was further tested extensively. Results indicated a good rate and initial bending performance of the battery with a maximum specific capacity of 310 mAh/g at 0.1 A/g. Additionally, the battery tested at 0.5 A/g showed an average specific capacity of 175 mAh/g over 300 cycles with a 96.5% Coulombic efficiency. Attaining energy densities between 150.4 and 252.4 Wh/kg (w.r.t. active cathode mass) is possible for these batteries, thus encouraging their use in varied applications. Utilizing chitosan gel electrolyte and limited voltage window testing, the prepared Zn-EMD alkaline batteries are among the first reported polymer-based alkaline electrolyte Zn rechargeable batteries with no cathode additives.

A cost-effective and sustainable approach was used to enhance the thermoelectric performance of printable thermoelectric composite films. Using this approach, we are trying to get rid of the highly energy-intensive (high temperature and long duration) and time-consuming process of manufacturing thermoelectric generators. This study presents a unique approach of using an environmental-friendly and naturally occurring binder, a heterogeneous particle size distribution and applied mechanical pressure to fabricate n-type thermoelectric composite films. Recently spotlighted biomaterial, chitosan, was employed as a binder and it provided enough binding strength to the composite thermoelectric films. Bi 2 Te 2.7 Se 0.3 is an attractive n-type thermoelectric material because of its high thermoelectric performance. In this work, we are using two different (100-mesh and 325-mesh) n-type Bi 2 Te 2.7 Se 0.3 thermoelectric conductive particles for thermoelectric composite films to understand the role of wide-range particle distribution on thermoelectric composite films. In addition, two different weight ratios (1:2000 and 1:5000) of binders to Bi 2 Te 2.7 Se 0.3 particle and two different applied pressures (150 MPa and 200 MPa) were used for this study. The application of pressure and the use of a heterogenous particle distribution improves the packing density which leads to well-aggregated and coalesced polycrystal bulk-like structure in chitosan 100-mesh (heterogeneous particle distribution) Bi 2 Te 2.7 Se 0.3 thermoelectric composite films and hence improves the overall electrical conductivity and power factor. The best performing composite film was made with an ink of a 1:2000 weight ratio of binder to100-mesh Bi 2 Te 2.7 Se 0.3 and the applied pressure was 200 MPa. The electrical conductivity was 200 ± 7 S cm À1 , the Seebeck coefficient was À201 ± 6 lV K À1 , the power factor was 808 ± 69.7 lW m À1 K À2 , the thermal conductivity was 0.6 W m À1 K À1 , and the figure of merit was 0.4 at room temperature. Using energy efficient, sustainable, and cost effective method we achieved ZT of 0.40 for n-type thermoelectric composite films which is comparable to other printed n-type TE composite films. A 2-leg n-type Bi 2 Te 2.7 Se 0.3 device was fabricated with a power output of 0.48 lW at a closed circuit voltage of 2.1 mV and DT of 12 K.

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