The influence of S[sbnd]O anion groups of organic/inorganic additives in rechargeability of zinc-air batteries

Abstract

A number of difficulties on the zinc surface, including dendrites, passivation, shape change, and corrosion, result in insufficient electrochemical performance. Additives having an SO anion group incorporated into organic/inorganic atoms offer varied charge distributions of molecules that may be effective in resolving problems. Four additives containing the SO anion group, such as 4-Morpholinepropanesulfonic acid (MOPS, organic) and Na2S2O3, Na2SO3, and Na2SO4 (inorganic), reveal that 0.33 % (v/v) 1 M Na2SO4/6 M KOH is the most effective electrolyte due to its good Zn-deposition/dissolution. The maximal specific capacity of 818 mAhg−1 at 50 mAcm−2 (material utilization of 99.8 % based on the value of 820 mAhg−1) is compared to 806 mAhg−1 for the electrolyte-free additive. The galvanostatic charge-discharge cycles demonstrate excellent and stable performance without any fluctuations with the lower voltage gap (1.07 V) for Na2SO4/KOH at 50 mAcm−2 for >100 h, which is significantly lower than 6 M KOH at around 1.2 V. (1.4 V). DFT analyses demonstrate that Na2SO4 with the minimum energy gap (higher intrinsic conduction) are effective additives. As an organic additive, MOPS/KOH demonstrates an exceptional discharge capacity, but weak Zn-deposition/dissolution was seen due to the greatest energy gap, which resulted in less charge transfer interaction within the molecule.