Dual-enhancement on electrochemical performance with thioacetamide as an electrolyte additive for lithium-sulfur batteries

Advanced Electrolyte Additives for Enhanced Homogeneous Sulfur Fixation in Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are regarded as leading contenders for next-generation energy storage owing to their exceptional theoretical energy density. However, severe sulfur electrode depletion causes rapid capacity fading and compromised cycling stability. Electrolyte engineering effectively enables homogeneous sulfur fixation, improving battery performance. The study investigates the mechanisms behind these homogeneous reactions, focusing on sulfur fixation processes. Sulfur fixation is explored through multiple perspectives, including the inhibition of polysulfide shuttling, mitigation of electrode passivation, and the combined application of both strategies. Regarding polysulfide shuttling inhibition, three distinct mechanisms for sulfur fixation are identified: 1) chemisorption-based sulfur fixation, involving the formation of chemical bonds with polysulfides; 2) redox-mediated sulfur fixation, which accelerates the kinetics of sulfur species; and 3) hybrid sulfur fixation, which combines elements of both approaches. Furthermore, the review analyzes current methods for homogeneous sulfur fixation, focusing on electrolyte designs that enable homogeneous sulfur fixation under limited conditions. It provides insights to optimize electrolytes, advancing Li-S battery performance and commercialization.

Strategy to Simultaneously Manipulate Direct Zn Nucleation and Hydrogen Evolution via Surface Modifier Hydrolysis for High-Performance Zn-Ion Batteries

The demand for safer batteries is growing rapidly due to fire incidents in electronic devices that use Li-ion batteries. Zn-ion batteries are among the most promising candidates to replace Li-ion batteries because they use a water-based electrolyte and are not explosive. However, Zn-ion batteries suffer from persistent corrosion and dendritic crystal formation during the charge-discharge process, which decrease their reversibility and hinder their commercial usage. Extensive research has been conducted to address these issues, but there are significant limitations due to high process and time costs. In this study, the modulation of the Zn-electrolyte interface to overcome these challenges is attempted using acetamide-derived thioacetamide (TAA), a surface modifier used in electroplating. TAA undergoes hydrolysis in an aqueous solution and produces weakly acidic byproducts and sulfide ions. These species are adsorbed onto the Zn metal surface, which induces uniform Zn2+ deposition, facilitates the formation of a stable interfacial layer, and inhibits side reactions due to the reduced water activity. Consequently, the symmetric cell with TAA achieves a low polarization of 50 mV and stable cycling for 700 h at 1 mA cm-2. Additionally, a Zn|V6O13 full cell exhibits electrochemical reversibility, maintaining a capacity retention of 64% over 300 cycles. Therefore, this study offers useful insights into the development of a simple manufacturing process to ensure the competitiveness of Zn-ion batteries for practical applications using functional electrolyte additives.

Catalytic Effect of Ammonium Thiosulfate as a Bifunctional Electrolyte Additive for Regulating Redox Kinetics in Lithium-Sulfur Batteries by Altering the Reaction Pathway

Sluggish sulfur redox kinetics and incessant shuttling of lithium polysulfides (LiPSs) greatly influence the electrochemical properties of lithium-sulfur (Li-S) batteries and their practical applications. For this reason, ammonium thiosulfate (AMTS) with effective redox regulation capability has been proposed as a functional electrolyte additive to promote the bidirectional conversion of sulfur species and inhibit the shuttle effect of soluble LiPSs. During discharging, the S2O32- in AMTS can trigger the rapid reduction of LiPSs from long chains to short chains by a spontaneous chemical reaction with sulfur species, thereby decreasing the accumulation of LiPSs in the electrolyte. During charging, the NH4+ in the AMTS enhances the dissociation/dissolution of Li2S2/Li2S by hydrogen-binding interactions, which alleviates the electrode surface passivation and facilitates the reversible oxidation of short-chain sulfides back to long chains. The enhanced bidirectional redox kinetics brought about by AMTS endows Li-S cells with high reversible capacity, excellent cycle stability, and rate capability even under lean electrolyte conditions. This work not only illustrates an effective redox regulation strategy by an electrolyte additive but also investigates its catalytic reaction mechanism and Li corrosion behavior. The crucial criteria for screening additives that enable bidirectional redox mediation analogous to AMTS are summarized, and its application perspectives/challenges are further discussed.

Thioacetamide Additive Homogenizing Zn Deposition Revealed by In Situ Digital Holography for Advanced Zn Ion Batteries

Zinc ion batteries are considered as potential energy storage devices due to their advantages of low-cost, high-safety, and high theoretical capacity. However, dendrite growth and chemical corrosion occurring on Zn anode limit their commercialization. These problems can be tackled through the optimization of the electrolyte. However, the screening of electrolyte additives using normal electrochemical methods is time-consuming and labor-intensive. Herein, a fast and simple method based on the digital holography is developed. It can realize the in situ monitoring of electrode/electrolyte interface and provide direct information concerning ion concentration evolution of the diffusion layer. It is effective and time-saving in estimating the homogeneity of the deposition layer and predicting the tendency of dendrite growth, thus able to value the applicability of electrolyte additives. The feasibility of this method is further validated by the forecast and evaluation of thioacetamide additive. Based on systematic characterization, it is proved that the introduction of thioacetamide can not only regulate the interficial ion flux to induce dendrite-free Zn deposition, but also construct adsorption molecule layers to inhibit side reactions of Zn anode. Being easy to operate, capable of in situ observation, and able to endure harsh conditions, digital holography method will be a promising approach for the interfacial investigation of other battery systems.

Multi-function hollow nanorod as an efficient sulfur host accelerates sulfur redox reactions for high-performance Li-S batteries

The "shuttle effect" of lithium polysulfides (LiPSs) leads to loss of active materials and the deterioration of cycle stability, which seriously restricts the practical progress of lithium-sulfur (Li-S) batteries. The diffusion of soluble discharge intermediate is the root cause of the above problems. Herein, we synthesized a porous organic framework material (HUT-8) based on triazine network, the polar groups above the hollow structure can not only adsorb LiPSs through electron donating effect, but also anchored cobalt (II) ions provide a large number of binding sites for the in-situ growth of CoS2. This ensured maximized exposure of catalytic centre and improve their interactions with sulfur redox species under the confinement of mesopores, which can catalytically accelerate capture/diffusion of LiPSs and precipitation/decomposition of Li2S. Based on the synergistic effect of the composite materials, the CoS2-HUT-8/S cathode maintained a capacity of 583 mAh g-1 after 500 cycles at 1 C, and a minimum capacity fading rate of 0.046% per cycle. A freestanding CoS2-HUT-8/S cathode with sulfur loading of 5.2 mg cm-2 delivered a high areal capacity of 4.01 mAh cm-2 under a lean electrolyte, which would provide great potential for the practical progress of Li-S batteries.

Sustainable Protein-Based Binder for Lithium-Sulfur Cathodes Processed by a Solvent-Free Dry-Coating Method

In the market for next-generation energy storage, lithium-sulfur (Li-S) technology is one of the most promising candidates due to its high theoretical specific energy and cost-efficient ubiquitous active materials. In this study, this cell system was combined with a cost-efficient sustainable solvent-free electrode dry-coating process (DRYtraec®). So far, this process has been only feasible with polytetrafluoroethylene (PTFE)-based binders. To increase the sustainability of electrode processing and to decrease the undesired fluorine content of Li-S batteries, a renewable, biodegradable, and fluorine-free polypeptide was employed as a binder for solvent-free electrode manufacturing. The yielded sulfur/carbon dry-film cathodes were electrochemically evaluated under lean electrolyte conditions at coin and pouch cell level, using the state-of-the-art 1,2-dimethoxyethane/1,3-dioxolane electrolyte (DME/DOL) as well as the sparingly polysulfide-solvating electrolytes hexylmethylether (HME)/DOL and tetramethylene sulfone/1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TMS/TTE). These results demonstrated that the PTFE binder can be replaced by the biodegradable sericin as the cycle stability and performance of the cathodes was retained.