Zinc-air batteries are a promising technology for large-scale electricity storage. However, their practical deployment has been hindered by some issues related to corrosion and passivation of the zinc anode in an alkaline electrolyte. In this work, anionic surfactant sodium dodecyl sulfate (SDS) and nonionic surfactant Pluronic F-127 (P127) are examined their applicability to enhance the battery performances. Pristine zinc granules in 7 M KOH, pristine zinc granules in 0–8 mM SDS/7 M KOH, pristine zinc granules in 0–1000 ppm P127/7 M KOH, and SDS coated zinc granules in 7 M KOH were examined. Cyclic voltammograms, potentiodynamic polarization, and electrochemical impedance spectroscopy confirmed that using 0.2 mM SDS or 100 ppm P127 effectively suppressed the anode corrosion and passivation. Nevertheless, direct coating SDS on the zinc anode showed adverse effects because the thick layer of SDS coating acted as a passivating film and blocked the removal of the anode oxidation product from the zinc surface. Furthermore, the performances of the zinc-air flow batteries were studied. Galvanostatic discharge results indicated that the improvement of discharge capacity and energy density could be sought by the introduction of the surfactants to the KOH electrolyte. The enhancement of specific discharge capacity for 30% and 24% was observed in the electrolyte containing 100 ppm P127 and 0.2 mM SDS, respectively.

In the past few years, there has been a growing level of interest in the research and development of energy storage systems such as batteries. This is a direct consequence of the soaring rise in global energy demand across various commercial and industrial sectors. Lithium ion batteries have set out a feasible horizon for widespread deployment as small-scale energy storage devices due to their high efficiency and cyclability. However, the availability and cost of lithium have limited the commercial deployment of large-scale systems. On the other hand, zinc-air batteries have demonstrated comparable efficiencies and have been reported to be suitable replacements for lithium batteries in large-scale applications. Nevertheless, more research has been undertaken to address the issues associated with the cycling processes of these batteries. Secondary zinc-air batteries are yet to be commercially proven feasible due to the low charge/discharge cycle life of electrodes. The main problems of secondary alkaline zinc-air batteries are dendritic growth resulting in an alternation of morphology and structure, self-dissolution and the consequent occurrence of hydrogen evolution reactions. However, by and large, inefficient electrolytes are the main culprits responsible for the reduced performance of zinc-air batteries. Therefore, a comprehensive review of current advancements in the development of suitable electrolytes to promote zinc-air batteries towards commercial application will provide a perspective for future rechargeable zinc-air batteries. In this in-depth review, the effects of the types of electrolytes and their properties on the electrochemical 2 performance of Zn anode have been discussed. A demonstration of the current research status and challenges set upon the large-scale deployment of zinc-air batteries will facilitate the educated steering of future research directions in this critically important realm.

a b s t r a c tThe cordierite monolith was successfully modified to carbonaceous material termed as carbon coated monolith (CCM). Surface studies showed about 65% of the total pore volume falls in mesopore range with acidic functionality dominating over the surface. Batch adsorption experiments were carried out to study the applicability of CCM for the removal of methyl orange (MO) from aqueous solution. Different parameters such as effect of MO concentration, contact time, initial pH, regeneration and desorption potential of CCM were studied. Optimum adsorption of MO on CCM was observed at pH 6 (27.2 mg/g). The increase in initial MO concentration from 50 to 500 mg/L leads to increase in adsorption capacity from 15.99 to 88.5 mg/g. The observed equilibration time ranged in between 5000 and 5800 min. Linear and non-linear isotherm studies showed better applicability of Freundlich model. Kinetics studies showed better fitting for pseudo-second-order model. The Weber and Morris model showed multi-linearity indicating two or more steps were involved to describe the adsorption process. Desorption studies showed maximum recovery of MO when alkaline NaOH solution was used as an eluent. The regeneration studies showed decrease in adsorption capacity from 47.93 to 23.76 mg/g after three cycles.

The present work describes the effects of dimethyl sulfoxide (DMSO) in KOH aqueous electrolyte on the performance of a zinc-air flow battery. Aqueous electrolytes containing 7 M KOH and (0 to 20)% v/v DMSO were studied revealing a critical role of DMSO on the dissolution and deposition of zinc. The anodic zinc dissolution process was studied via cyclic voltammetry, Tafel polarization and electrochemical impedance spectroscopy (EIS). The presence of DMSO showed improved zinc dissolution performance with the highest peak of zinc dissolution being the electrolyte containing 5% v/v DMSO. Tafel analysis demonstrated a significant decrease in polarization resistance and an increase in corrosion rate due to the introduction of DMSO to the electrolyte. This suggests that DMSO has the ability to suspend zinc oxide in the electrolyte, thus preventing passivation of the zinc surface. EIS results revealed that by adding DMSO to the electrolyte, charge transfer resistance increased. This is attributed to the formation of passive layers having arisen from DMSO adsorption, the formation of zincate ions in the vicinity of the zinc surface, and the deposition of discharged products. A difference in Nyquist plots was observed for 20% v/v DMSO/KOH and 0% v/v DMSO/KOH electrolytes implying non-Debye relaxation behavior taking place due to the surface effects. The electrolytes were implemented in a zinc-air flow battery. Maximum power densities of 130 mW/cm2 (5% v/v DMSO) and 125 mW/cm2 (20% v/v DMSO) were obtained and were observed to be about 43% and 28% higher than that of the DMSO-free electrolyte. Results indicated that when 20% v/v DMSO was added to KOH solution, there was 67% zinc utilization efficiency (550 mAh/g) which provided 20% improvement in discharge capacity. Further, the battery with 20% v/v DMSO demonstrated excellent cyclability. Overall, DMSO shows great promise for enhancement of zinc dissolution/deposition in zinc-air batteries.

Zinc-air flow batteries exhibit high energy density and offer several appealing advantages. However, their low efficiency of zinc utilization resulted from passivation and corrosion of the zinc anodes has limited their broad application. In this work, ethanol, which is considered as an environmentally friendly solvent, is examined as an electrolyte additive to potassium hydroxide (KOH) aqueous electrolyte to improve electrochemical performance of the batteries. Besides, the effects of adding different percentages of ethanol (0–50% v/v) to 8 M KOH aqueous electrolyte were investigated and discussed. Cyclic voltammograms revealed that the presence of 5–10% v/v ethanol is attributed to the enhancement of zinc dissolution and the hindrance of zinc anode passivation. Also, potentiodynamic polarization and electrochemical impedance spectroscopy confirmed that adding 5–10% v/v ethanol could effectively suppress the formation of passivating layers on the active surface of the zinc anodes. Though the addition of ethanol increased solution resistance and hence slightly decreased the discharge potential of the batteries, a significant enhancement of discharge capacity and energy density could be sought. Also, galvanostatic discharge results indicated that the battery using 10% v/v ethanol electrolyte exhibited the highest electrochemical performance with 30% increase in discharge capacity and 16% increase in specific energy over that of KOH electrolyte without ethanol.