Organic Fillers Regulating the Solvation Structure of Zinc Ions in Aqueous Electrolytes for High-Stability Zn²⁺/Li⁺ Hybrid Batteries

Abstract

The aqueous hybrid ion batteries, due to electrode advantages combined with different battery systems, are promising energy storage systems. The severe side reaction caused by a highly active aqueous electrolyte is the key challenge that restricts its practical application. Exploring the microstructure of the electrolyte is of great significance to improving the electrochemical performance. Herein, the regulation mechanism of acylamide groups in an aqueous electrolyte is deeply investigated. Due to the strong coordination ability and hydrophilicity of the acylamide group, the solvation structure of cations can be regulated, and the activity of water molecules can be weakened by hydrogen bonds. Therefore, the Zn 2+ plating/stripping process on the anode side can be orderly regulated, and the stability of the crystal structure of the cathode also could be significantly improved. Consequently, after adding 5% polyacrylamide into the electrolyte, the zinc anode can withstand long-term plating/stripping over 120 h at 1 mA cm −2 and 0.25 mA h cm −2 . Also, the LiFePO 4 cathode could achieve a capacity resistance of 82% after 350 cycles at 0.5 A g −1 , far higher than the 24% of pure liquid electrolytes. This work provides a helpful guidance for designing the next generation of hybrid ion electrolytes.

Low-Cost Aqueous Electrolyte with MBA Additives for Uniform and Stable Zinc Deposition

“…In contrast, without MBA additives, the symmetric batteries could only cycle for 50 h and show short circuit after 100 h. This suggests that MBA additives can effectively inhibit dendrite formation and improve cycling stability. The cycling stability of Zn symmetric cells are much better than other reports, as shown in Figure S7 and summarized in Table S1. ,,− Impressively, the Zn symmetric cell exhibits better cycling stability at 60% depth of discharge (DOD) over 160 h in the Zn 1 N 20 electrolyte, as shown in Figure S8a. In addition, long cycle stability is achieved at high DOD up to 70% in the Zn 1 N 20 electrolyte, as shown in Figure S8b.…”

“…Fourier transform infrared spectroscopy (FTIR) reveal the stretching vibrations of O–H at 3221 cm –1 shifted to a higher wavenumber after MBA addition, as presented in Figure S3a. This further reveals that the addition of MBA reduces the activity of water in the electrolyte. ,, In addition, Raman spectroscopy shows SO 4 2– tensile vibration with peaks located at 980 cm –1 , as displayed in Figure S3b. , The peak intensity decreases after MBA addition, indicating a weakened hydrated solvation structure. The abovementioned results demonstrate that the addition of MBA is beneficial to inhibiting the occurrence of hydrogen evolution reaction and promoting zinc deposition.…”

“…The polar organic solvents such as N, N -dimethylformamide (DMF), and polypropylene glycol (PPG) can modulate the solvation structure and enhance Zn plating/stripping reversibility. The organic additives containing S 2– , PO 4 3– , and F – groups can decompose and form the stable solid electrolyte interface (SEI) on zinc anode surfaces. , Furthermore, the proton transfer and HER can be suppressed with the polar additives via forming stronger hydrogen bonds. − What is more, the polar functional groups in the organic additives can modulate the aqueous electrolyte through hydrogen bonding . The SO groups of tetramethylene sulfone (TMS) exhibit a more negative charge distribution than the O–H group, which can promote the formation of hydrogen bonds with free water molecules .…”