Development of rechargeable high-energy hybrid zinc-iodine aqueous batteries exploiting reversible chlorine-based redox reaction

Abstract

The chlorine-based redox reaction (ClRR) could be exploited to produce secondary high-energy aqueous batteries. However, efficient and reversible ClRR is challenging, and it is affected by parasitic reactions such as Cl2 gas evolution and electrolyte decomposition. Here, to circumvent these issues, we use iodine as positive electrode active material in a battery system comprising a Zn metal negative electrode and a concentrated (e.g., 30 molal) ZnCl2 aqueous electrolyte solution. During cell discharge, the iodine at the positive electrode interacts with the chloride ions from the electrolyte to enable interhalogen coordinating chemistry and forming ICl3-. In this way, the redox-active halogen atoms allow a reversible three-electrons transfer reaction which, at the lab-scale cell level, translates into an initial specific discharge capacity of 612.5 mAh gI2−1 at 0.5 A gI2−1 and 25 °C (corresponding to a calculated specific energy of 905 Wh kgI2−1). We also report the assembly and testing of a Zn | |Cl-I pouch cell prototype demonstrating a discharge capacity retention of about 74% after 300 cycles at 200 mA and 25 °C (final discharge capacity of about 92 mAh).

Low‐cost and Non‐flammable Eutectic Electrolytes for Advanced Zn‐I2 Batteries

“…The pouch cell also has a high capacity of � 78.5 mAh and excellent cycling stability with capacity retention of 96.7 % after 500 cycles (Figure 6g). The capacity decay is only 6.6 × 10 À 5 per cycle, which is also superior to that reported for Zn-I 2 , [42][43][44][45][46] Zn-V 2 O 5 , [47,48] and Zn-MnO 2 pouch cells [49,50] (Figure 6h). To assess the efficacy of the Zn-I 2 pouch cell, a large-size toy car ( � 25 cm in length and � 10 cm in height) was tested by using our designed batteries (Figure S20a and Figure 6i).…”

Low‐cost and Non‐flammable Eutectic Electrolytes for Advanced Zn‐I2 Batteries

“…The pouch cell also has a high capacity of � 78.5 mAh and excellent cycling stability with capacity retention of 96.7 % after 500 cycles (Figure 6g). The capacity decay is only 6.6×10 À 5 per cycle, which is also superior to that reported for Zn-I 2 , [42][43][44][45][46] Zn-V 2 O 5 , [47,48] and Zn-MnO 2 pouch cells [49,50] (Figure 6h). To assess the efficacy of the Zn-I 2 pouch cell, a large-size toy car ( � 25 cm in length and � 10 cm in height) was tested by using our designed batteries (Figure S20a and Figure 6i).…”

Chaotropic Electrolyte Enabling Wide-Temperature Metal-Free Battery

“…Similarly, the UV–vis spectrum of the electrolyte emerging with the cycled I 2 @CC electrode has a peak at 342 nm, which is indicative of [ICl x ] 1– x interhalogen formation (Figure c and Figure S23). The existence of [ICl x ] 1– x interhalogen is also confirmed by Raman spectra (Figure S24a), which together indicate the I + /I 0 conversion reaction at the cathode.…”