Usage Of Electrolyte Research Articles

Amorphous bimetallic-organic framework enable accelerated redox kinetics and polysulfide trapping for lithium-sulfur batteries

Severe polysulfide dissolution and shuttling during charging and discharging are the main challenges hindering the practical application of lithium-sulfur (Li-S) batteries. Constructing functional separators is considered as an economical and convenient way to suppress the shuttle effect and improve the kinetics of Li-S chemistry. In this work, partially ligand-deficient amorphous bimetallic MOF material (aFeNi-MOF) is designed via a ligand competition strategy and employed as a separator modifier. The aFeNi-MOF not only promotes the rapid transportation of ions, but also enhances the chemisorption and catalytic capability on sulfur species, enabling accelerated redox kinetics and polysulfide trapping in Li-S batteries. Consequently, the assembled coin cell using aFeNi-MOF-modified separator delivered a high reversible capacity of 931.1 mAh/g at 1C, a long cycle life of more than 500 cycles and a low capacity decay of 0.084 % per cycle. Meanwhile, the areal capacity of 3.70 mAh cm−2 can be achieved under a high sulfur loading of 4.5 mg cm−2 and low electrolyte usage, meeting the requirement of areal capacity for commercial applications of Li-S batteries.

An Electrolyte Engineered Homonuclear Copper Complex as Homogeneous Catalyst for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries suffer from severe polysulfide shuttle, retarded sulfur conversion kinetics and notorious lithium dendrites, which has curtailed the discharge capacity, cycling lifespan and safety. Engineered catalysts act as a feasible strategy to synchronously manipulate the evolution behaviors of sulfur and lithium species. Herein, a chlorine bridge-enabled binuclear copper complex (Cu-2-T) is in situ synthesized in electrolyte as homogeneous catalyst for rationalizing the Li-S redox reactions. The well-designed Cu-2-T provides completely active sites and sufficient contact for homogeneously guiding the Li2S nucleation/decomposition reactions, and stabilizing the lithium working interface according to the synchrotron radiation X-ray 3D nano-computed tomography, small angle neutron scattering and COMSOL results. Moreover, Cu-2-T with the content of 0.25wt% approaching saturated concentration in electrolyte further boosts the homogeneous optimization function in really operated Li-S batteries. Accordingly, the capacity retention of the Li-S battery is elevated from 51.4% to 86.3% at 0.2 C, and reaches 77.0% at 1.0 C over 400 cycles. Furthermore, the sulfur cathode with the assistance of Cu-2-T realizes the stable cycling under the practical scenarios of soft-packaged pouch cell and high sulfur loading (6.5mg cm-2 with the electrolyte usage of 4.5µL mgS -1).

Hybrid laser-ECM processing of advanced materials in neutral electrolyte without aggressive reagents: Machining performance, removal characteristics and sustainability aspects

The growing need for more energy efficient systems has led to advent of hard and corrosion resistant materials which are difficult to machine with both conventional and non-conventional machining techniques. Although ECM offers athermal and force-free dissolution, the workpiece surface integrity in multicomponent materials is limited with ECM due to several multi-physical phenomena occurring on the surface like selective phase dissolution, passivation, pitting, particle breakout, etc. To tackle these challenges, aggressive acidic and basic reagents are added to the electrolytes. Although these reagents improve the machining performance, they are not sustainable for the environment and human life as they generate harmful waste which is difficult to dispose and recycle. Furthermore, the handling of these aggressive electrolytes requires specialized coatings, resins, filters, catalysts, etc. to protect the machine tools and equipment from damage.Hybrid laser-ECM (LECM) is a relatively novel drill-mill processing technique to process these advanced materials while using neutral electrolytes, thereby potentially reducing the negative impact of using acidic/basic reagents in electrolytes. Under controlled conditions and proper laser alignment, LECM can simultaneously apply laser and EC process energies in the same machining zone to provide synergistic benefits manifesting in terms of dominance of kinetics and thermodynamics over pure electrodynamics in ECM. This provides multi-fold benefits in improving passivation weakening and homogenize multiphase dissolution. Therefore, this study investigates for the first time the machining performance, removal behaviour, reaction products and power/resource consumption of LECM in neutral electrolyte in comparison to ECM in various neutral and basic electrolytes. The NbC–Ni cermet was used as the workpiece material, which is a cobalt-free alternative to conventional WC-Co. The results revealed that LECM in neutral NaNO3 compared to ECM with NaOH addition not only provided better Sa (2.02 μm, 24% ↓), M.R.R. (153 μg/s, 31% ↑), aspect ratio (0.048, 14% ↑) and similar passivation weakening capability while maintaining a nearly neutral pH (8) of the reaction products, but also reduced electrolyte usage by 23.6% with a 16.4% increase in power consumption. These aspects make LECM a sustainable and cost-effective candidate for processing modern passivating multiphase materials like newer cermets, super alloys, high entropy alloys, etc. with nearly same performance as achieved by using ECM with acidic/basic electrolytes. Further fundamental and applied research is needed in LECM to meet the industrial specifications.

Efficient solid dielectric electrochemical polishing with minimal electrolyte consumption and reusable conductive media

Electrochemical polishing finds wide application across various industries, including manufacturing, biomedicine, and semiconductors. However, this technology requires substantial water usage and results in environmental pollution due to the generation of waste electrolytes containing highly corrosive acids and heavy metal ions. Herein, we propose an electrochemical polishing method (SDEP) that employs solid dielectrics consisting of macroreticular ion exchange resin (MIER) solid particles and phosphoric acid electrolyte as an alternative to traditional liquid conductive media. Maintaining a polishing current of 0.4–0.5 A requires only an electrolyte consumption of 10–20 mL/h, leading to a more than 65% reduction in electrolyte usage compared to liquid electrochemical polishing. Meanwhile, this method can be applied to polish additively manufactured metal parts with an initial roughness Ra>10 μm. The achievable surface finish features Ra = 0.778 ± 0.078 μm, Rq = 0.960 ± 0.121 μm, and Rz = 4.175 ± 1.111 μm after 1-h polishing, with a material removal rate of 0.15–0.19 mm3/min. The improvement of Ra, Rq, and Rz are 92.3%, 92.1%, and 92.0%, respectively. With the EDS and XPS analysis, rod-shaped by-products adhering to the surface of MIER particles generated during the SDEP process are confirmed as Fe3+, PO43−, and PO3−. Furthermore, the MIER particles can be reused after cleaning, exhibiting polishing performance comparable to fresh MIER. This method reduces the use of electrolytes at the source of electropolishing, and MIER particles can be recycled, pointing towards the development of eco-friendly electrochemical polishing.

Advancing Post‐Secondary Batteries under Lean Electrolyte Conditions through Interfacial Modification Strategies

AbstractIn response to the growing global demand for portable electronics and electric vehicles, there is an escalating interest in developing advanced battery technologies with superior energy density. Research efforts are focused on unveiling post‐lithium‐ion batteries (LIBs) that outperform the performance of current LIBs through the use of innovative active electrode materials. Yet, these technological advancements face significant hurdles, primarily due to intricate interfacial issues within battery components. In laboratory‐scale studies, these challenges often lead to the utilization of excess electrolytes, which complicates the precise evaluation of battery performance. This review emphasizes the significance of designing future batteries that operate effectively under lean electrolyte usage conditions. It discusses essential principles, obstacles, and diverse strategies for interfacial modification, including in situ growth, coating of supportive layers, and embedding of active substances in pre‐structured templates. Furthermore, it compiles and examines data on the lean electrolyte conditions achieved in various battery systems, contrasting their energy densities with those of commercially established batteries. Ultimately, the potential of future batteries to achieve or even exceed the energy densities of existing commercial batteries is assessed, thereby offering a strategic roadmap for the progression of next‐generation battery technologies.

Evaluation of Electropolishing Characteristics of 316L Stainless Steel Tube in Contaminated Electrolyte

In the electropolishing process, the polishing quality of the metal surface varies according to the contamination of the electrolyte. In this study, the electrolyte was evaluated according to the usage time, and the effect of each factor on electropolishing was investigated. As the electrolyte is contaminated, the concentration of metal ions in the electrolyte increases and the ion conductivity decreases. In addition, the pH and specific gravity of the electrolyte increase due to the metal sludge formed as the metal ion concentration increases. When the electrolyte usage time was more than 5 days, many scratches remained on the surface of 316L stainless steel, and relatively high surface roughness was measured. The surface roughness improvement rate compared to the initial specimen was 30% for the unused electrolyte, 26% on the 3rd day, 19% on the 5th day, and 17.5% on the 13th day. Since the low current density due to electrolyte contamination causes a decrease in polishing efficiency, initial scratches on the metal surface still exist on the polished surface. Therefore, it is necessary to manage the electrolyte to maintain the quality of electropolishing.

Tailoring molecular structures for enhanced anchoring of polysulfides in lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries, with promising potential for high energy density, remain compelling candidates for next-generation energy storage systems. However, they still suffer from huge challenges such as severe shuttle effects and sluggish redox kinetics. A strategic approach involves the meticulous design of host materials at the molecular level, emphasizing the construction of efficient sulfiphilic organic molecules as anchoring sites for lithium polysulfides (LiPS). In this study, a series of benzamides (benzamide, 2-fluorobenzamide, and 2,6-difluorobenzamide) are introduced onto carboxylic multiwalled carbon nanotubes (C-CNT) to graft sulfur hosting materials with tailored functional interfaces for Li–S batteries. Through a comparative study, we identify the semi-ionic C−F bond and carbonyl functional group as active centers, presenting a synergistic strategy via Li···O and Li···F bonds for anchoring LiPS. The optimized cathode material of sulfur-based carbon nanotubes grafted with 2-fluorobenzamide exhibits outstanding electrochemical activity, achieving a high reversible capacity of 944.8 mAh/g under a high sulfur loading (5.5 mg cm−2) and low electrolyte usage (8 µL mg−1). Our study underscores the potential of tailoring the molecular structure of host materials to effectively immobilize LiPS for high-performance Li–S batteries.

Progress on critical cell fabrication parameters and designs for advanced lithium-sulfur batteries.

Since 1990, commercial lithium-ion batteries have made significant strides, approaching their theoretical performance limits, albeit with escalating costs. To address these challenges, attention has shifted toward lithium-sulfur batteries, which offer higher theoretical energy densities and cost-effectiveness. However, lithium-sulfur cells face challenges such as active-material loss, excessive electrolyte usage, and rapid degradation of lithium-metal anodes. To overcome these issues, research has focused on optimizing cell configurations and fabrication parameters while exploring novel electrolytes and electrode materials. This feature article delves into the intrinsic material challenges and extrinsic engineering issues in current lithium-sulfur research and explores the development of advanced lithium-sulfur cells with crucial progress on high-loading sulfur cathodes, lean-electrolyte cells, and solid-state electrolytes. Moreover, it outlines the fundamental principles, structures, performances, and developmental trajectories indicated in research articles published after 2020, highlighting future research directions aimed at resolving key challenges for the practical application of lithium-sulfur cells.

Cathode Design and Evaluation for the High-Sulfur-Loading, Lean-Electrolyte Lithium–Sulfur Battery

Sulfur is a promising active material for the lithium rechargeable batteries because of its high theoretical capacity, a relatively low cost, and an environmentally friendly nature. Lithium–sulfur battery with a high-energy-density is regarded as a third-generation rechargeable battery with high potential for commercialization. The well charged and discharged lithium–sulfur battery can generate specific energy density of up to 600 W∙h kg−1. However, the charging product, sulfur, and the discharging product, lithium sulfide, both have low conductivity, which lead to low active material utilization and excessive addition of conductive materials, lowering the active material content and performance in the cathode region. The liquid active material, polysulfides, formed in the middle of the cycling reaction will dissolve in the electrolyte, causing leakage to the lithium anode to form a non-reactive lithium sulfide layer, causing severe capacity fading. Furthermore, the repeated transformation of sulfur (solid-state), polysulfides (liquid-state), and lithium sulfur (solid-state) active materials led to the sluggish battery reaction and irreversible electrolyte consumption. All and all, the chemical and physical properties of the sulfur and the combination with lithium resulted in low active material utilization, low cycling ability, low capacity-retention rate, and shortened cycle life.To fully realize the potential of the high-energy-density lithium–sulfur battery, the cathode material, configuration, and fabrication must be carefully considered. Herein, a sulfur cathode fabricated by a hot-pressing method and the evaluation of different porous substrate was also conducted. Porous conductive network is a common cathode material, which provides a large surface area and great polysulfides absorbability. However, as a result of high-sulfur-loading and lean-electrolyte cathode batteries, a low specific capacity and short cycle life are discovered, which is affected by the high electrolyte consumption. Accordingly, a carbon electrospun substrate with a non-nanoporous structure was introduced as the conductive network to achieve the high-energy-density battery design. To fabricate the free-standing sulfur cathode, sulfur powder was loaded between two porous carbon electrospun substrate by a hot-pressing technique. The cathode consists of three layers: carbon current collector, melt-in sulfur layer, and carbon interlayer, forming a sandwich-like cathode.With this design, we can accommodate high areal loading of sulfur (8 mg cm−2) in the cathode area while lessening the conductive additive (sulfur content of 73 wt%). The hot-pressed electrospun cathode, conducted under low electrolyte usage (i.e., the low electrolyte-to-sulfur ratio of 7 µL mg−1) can achieve excellent energy density (11.8 mW∙h cm−2) with a stable areal capacity up to 5.9 mA∙h cm− 2 let alone with an extended cycle life over 200 cycles. Furthermore, this devised cathode can also retain excellent cycling ability with lower ratios of electrolyte to sulfur (6–4 µL mg−1) and great rate dependent performance up to C/2 cycling rate. Figure 1

Challenges and Solutions for Lithium–Sulfur Batteries with Lean Electrolyte

AbstractLithium–sulfur (Li–S) batteries have high theoretical energy density and are regarded as next‐generation batteries. However, their practical energy density is much lower than the theoretical value. In previous studies, the increase of the areal capacity of the cathode and the decrease of the negative/positive ratio can be well achieved, yet the energy density shows no corresponding increase. The main reason is the difficulty in decreasing electrolyte dosage because lean electrolyte inevitably causes the deterioration of reaction kinetics and sulfur utilization. Thus, the electrolyte/active material ratio in the reported works is usually higher than 10 µL mg−1, much higher than that in Li‐ion batteries (usually lower than ≈0.3 µL mg−1 for cathode). Although many works have focused on this topic, a systematic discussion is still rare. This review systematically discusses the key challenges and solutions for assembling high‐performance lean‐electrolyte Li–S batteries. First, the key challenges arising from lean‐electrolyte conditions are discussed in detail. Then, the approaches and the recent progress to reduce electrolyte usage, including optimization of electrode porosity and ion conduction, the introduction of electrocatalysis, exploration of new active materials, electrolyte regulation, and Li metal protection are reviewed. Finally, future research directions in lean‐electrolyte Li–S batteries are proposed.

In English

Anodic porous alumina has been studied and used as nanoscale structure, coating, template in different applications. The porous anodic alumina oxide could be described as numerous hexagonal cells and looks like cellular structure. In this work we report about results of study anodizing of aluminum with usage of electrolyte: “oxalic acid electrolyte-matter with carbon nanodots”. It was received anodic aluminum oxide-membrane with aluminum supporting; calcination was used as post treatment. The aluminum substrate allows one to fix the membrane in the cells. Methods: processes of anodizing was provided in 0.3M oxalic acid with addition of colloid system of carbon nanodots, temperature of process was controlled at range of 10 degree Celsius, aluminum foil (anode) and platinum plate (cathode) were used; thickness of aluminum foil was 0.1 µm; morphology and structure of anodic aluminum oxide-membrane were determined with usage of electron scanning microscope; the contact angle between the surface of anodic aluminum oxide-membrane and deionized water was measured with “drop” methodology. Calcium content was monitored with a conductometer. The content of proteins was determined with photometry (micro Lowry’s method). It was found that contact angle of the surface of anodic aluminum oxide-membrane obtained in electrolyte “oxalic acid-matter with carbon nanodots” and deionized water is 38 degrees. Adding colloidal system of carbon nanodots to the acid electrolyte acts as a hydrophilizer, changes the size of the porous surface: as a result, it is possible to control the porosity of the films. Calcination of anodic aluminum oxide-membrane at 500 degree Celsius lead to expansion and thinning of pore walls. Anodic aluminum oxide-membrane was tested for dialysis process for milk whey separation. The membrane obtained in electrolyte: “oxalic acid-matter with carbon nanodots” showed a greater degree of rejection of protein particles in comparison with a similar membrane obtained in electrolyte of oxalic acid. The advantage of using carbon nanodots in acid electrolyte is the simplicity and environmental friendliness of the synthesis. The approach, which involves the addition of a colloidal system with carbon nanomaterial, allows one to avoid using a strongly acidic electrolyte for obtaining membranes with smaller pores. One of the ways for using of anodic oxide aluminum-membrane is the dialysis of biological fluids, for example, milk whey.

Material, configuration, and fabrication designs for lean-electrolyte lithium–sulfur cell with a high-loading sulfur cathode

The lithium–sulfur battery is considered a promising candidate for third-generation commercial rechargeable batteries because of the high theoretical capacity of sulfur (1675 mA h g−1). However, the insulating solid-state active material causes low sulfur loading and content, challenging the increase of the energy density. The complex conversion reaction between solid-state and liquid-state active materials during charging/discharging process leads to high electrolyte usage and short cycle life. These issues affecting the evaluation of the electrochemical characteristics and performance of lithium–sulfur batteries are important for the commercialization of this technology. Herein, we propose a design of cathode material, configuration, and fabrication. This design realizes a porous carbon electrospun substrate built up with nonwoven carbon nanofibers having low nanoporosity. The carbon electrospun substrate is used as a porous electrode substrate to encapsulate insulating sulfur using a hot-pressing method, forming a hot-pressed electrospun cathode. The carbon electrospun substrate has a conductive, low-weight network to accommodate and exploit a high amount of sulfur (8 mg cm−2 and 73 wt%) at low electrolyte-to-sulfur ratios (7–4 μL mg−1), which achieves high charge-storage capacity (740 mA h g−1), large energy density (11.8 mW h cm−2), excellent rate performance (C/20–C/2 rates), and a prolonged cycle life (200 cycles).

Computational fluid dynamics simulation of bubble hydrodynamics in water splitting: Effect of electrolyte inflow velocity and electrode morphology on cell performance

Efficient management of oxygen gas bubbles evolving at the photoanode is important for a good overall performance of a photoelectrochemical (PEC) cell. The process of formation, detachment, coalescence and rise affects the bubble residence time at or near the photoanode. A reduced bubble residence time promotes easier electrolyte access to the photoanode surface, thereby enhancing the oxygen evolution reaction (OER) kinetics. In this work, computational fluid dynamics (CFD) simulations using laminar flow and phase-field model in COMSOL Multiphysics are conducted to study the gas bubble hydrodynamics for different bubble configurations, sizes, and bubble gaps. CFD results predict enhanced bubble rise in the presence of forced convection, i.e., some electrolyte inflow velocity (u≠0m.s−1). Experimental results using hematite as the model electrode also show a higher photocurrent density (ca. 4.33 mA.cm−2 at 2 V vs. RHE) for u = 0.1 m.s−1, compared to that without flow (3.5 mA.cm−2 at 2 V vs. RHE). This indicates improved access of electrolyte at the electrode surface and faster OER. Further, CFD simulations for electrode morphology effects show a reduced bubble adhesion for hydrophilic hematite nanorod arrays compared to planar photoanode, due to capillary wicking. The continuous contact film detaches and results in a reduced blockage of active sites at the bubble base, thereby enhancing the PEC performance for the nanorod arrayed morphology. Here too, experimental results show a four-fold increase in photocurrent density (ca. 0.1 mA.cm−2 at 1.5 V vs. RHE) and a 210 mV cathodic shift in onset potential for nanorods, compared to planar electrodes (0.025 mA.cm−2 at 1.5 V vs. RHE). A significant reduction in charge transfer resistance is observed for the former, implying better OER kinetics. The results obtained help in the understanding of transient processes involving O2 bubble hydrodynamics and electrolyte usage efficiency in a PEC reactor.

Nitrogen Balance on Ni-N-C Promotor for High-Energy Lithium-Sulfur Pouch Cells.

The viability of lithium-sulfur (Li-S)batteries toward real implementation directly correlates with unlocking lithium polysulfide (LiPS) evolution reactions. Along this line, designing promotors with the function of synchronously relieving LiPS shuttle and promoting sulfur conversion is critical. Herein, the nitrogen evolution on hierarchical and atomistic Ni-N-C electrocatalyst, mainly pertaining to the essential subtraction, reservation and coordination of nitrogen atoms, is manipulated to attain favorable Li-S pouch cell performances. Such rational evolution behavior realizes the "nitrogen balance" in simultaneously regulating the Ni-N coordination environment, Ni single atom loading, abundant vacancy defects, active nitrogen and electron conductivity, and maximizing the electrocatalytic activity elevation of Ni-N-C system. With such merit, the cathode harvests favorable performances in a soft-packaged pouch cell prototype even under high sulfur mass loading and lean electrolyte usage. A specific energy density up to 405.1Wh kg-1 is harvested by the 0.5-Ah-level pouch cell.

Demystifying Activity Origin of M–N–C Single‐Atomic Mediators Toward Expedited Rate‐Determining Step in Li–S Electrochemistry

Sluggish sulfur reduction reaction (SRR) kinetics remains a formidable challenge in Li–S electrochemistry. In this sense, the rational design of single‐atom species has become a burgeoning practice to expedite sulfur redox, where the underlying catalytic mechanism otherwise remains elusive. Herein, a class of metal single‐atom modified porous carbon nanofiber films (MSA PCNFs, M = Fe, Co, or Ni), fabricated via a generic synthetic strategy, as mediators to boost SRR kinetics is reported. Throughout electrokinetic measurement and operando instrumental probing, NiSA PCNF is evidenced to harness the catalytic superiority toward the rate‐determining step (i.e., liquid–solid conversion) of the SRR process. Density functional theory (DFT) simulations further reveal that the catalytic features of M–N–C moieties in catalyzing the Li2S precipitation rely heavily upon the coordination environments of adjacent carbon atoms and d‐orbital configurations of metal centers. In response, the thus‐derived S/NiSA PCNF cathode realizes an encouraging areal capacity of 14.12 mAh cm−2 under elevated sulfur loading (10.2 mg cm−2) and lean electrolyte usage (E/S ratio ≈ 5.5 μL mg−1). This work offers insight into the identification of exact catalytic moieties for different transition metal M–N–C single‐atom SRR mediators, showcasing a meaningful guidance and potential impact on Li–S catalysis.

Minimizing Carbon Content with Three‐in‐One Functionalized Nano Conductive Ceramics: Toward More Practical and Safer S Cathodes of Li‐S Cells

Using porous carbon hosts in cathodes of Li‐S cells can disperse S actives and offset their poor electrical conductivity. However, such reservoirs would in turn absorb excess electrolyte solvents to S‐unfilled regions, causing the electrolyte overconsumption, specific energy decline, and even safety hazards for battery devices. To build better cathodes, we propose to substitute carbons by In‐doped SnO2 (ITO) nano ceramics that own three‐in‐one functionalities: 1) using conductive ITO enables minimizing the total carbon content to an extremely low mass ratio (~3%) in cathodes, elevating the electrode tap density and averting the electrolyte overuse; 2) polar ITO nanoclusters can serve as robust anchors toward Li polysulfide (LiPS) by electrostatic adsorption or chemical bond interactions; 3) they offer catalysis centers for liquid–solid phase conversions of S‐based actives. Also, such ceramics are intrinsically nonflammable, preventing S cathodes away from thermal runaway or explosion. These merits entail our configured cathodes with high tap density (1.54 g cm−3), less electrolyte usage, good security for flame retardance, and decent Li‐storage behaviors. With lean and LiNO3‐free electrolyte, packed full cells exhibit excellent redox kinetics, suppressed LiPS shuttling, and excellent cyclability. This may trigger great research enthusiasm in rational design of low‐carbon and safer S cathodes.

Nickel–Platinum Alloy Nanocrystallites with High‐Index Facets as Highly Effective Core Catalyst for Lithium–Sulfur Batteries

AbstractElemental sulfur possesses an ultra‐high theoretical specific capacity, while the practical application of sulfur in lithium–sulfur (Li–S) batteries is seriously hindered by the sluggish redox kinetics and serious shuttle effect. Enhancing the catalytic activity of the sulfur host by a rational structural design is the key to address these issues. Herein, for the first time, concave‐nanocubic (CNC) nickel–platinum (Ni–Pt) alloys bounded by high‐index facets (HIFs) are introduced as the core catalyst of sulfur for Li–S batteries. It is demonstrated that the CNC Ni–Pt alloy crystallites dispersed uniformly on graphene exhibit a high electrochemical activity to drive the conversion from intermediate lithium polysulfides to solid discharged products. Benefiting from the accelerated redox kinetics by HIFs, the cathode delivers a low capacity damping of 0.025% per cycle for 1000 cycles at 1 C rate. In particular, a high reversible capacity of 664.9 mAh g−1‐cathode with cathode as active material can be achieved with high sulfur loading (8.8 mg cm−2) and low electrolyte usage (5 µL mgs−1). This study focuses on improving the catalytic activity of sulfur hosts by modulating the exposed facets of core catalyst and provides a new path for the structure optimizing of host materials in Li–S batteries.

Manipulating electrocatalytic activity of carbon architecture by supercritical carbon dioxide foaming and defect engineering for Li–S chemistry

Lithium–sulfur batteries (LSBs) have engendered extensive investigation interests owing to their remarkable theoretical capacity and energy density. Nevertheless, LSBs suffer from issues of fatal polysulfide (PS) shuttle and retarded sulfur redox reaction kinetics, impeding their real implementation. In this work, we report a delicate design of melamine formaldehyde resin-derived carbon architecture (CA) with manipulated electrocatalytic activity for Li–S chemistry by synergizing a versatile supercritical carbon dioxide (sc CO 2 ) foaming technique and tailored defect engineering. The superior redox reaction kinetics for PSs afforded by the as-designed active CA resulting from the comprehensive management of hierarchical pore structure, surface area, nitrogen content and vacancy defect degree are demonstrated by our systematic electrochemical measurements and synchrotron X-ray three-dimensional nano-computed tomography (X-ray 3D nano-CT) results. As expected, the cathode shows a low decay of 0.06% per cycle at 1.0 C for 800 cycles. Impressively, even at a high sulfur loading of 9.3 mg cm −2 and a low electrolyte usage of 4.0 μL mg S −1 , the cathode still delivers a remarkable specific capacity of 913.9 mA h g −1 as well as an outstanding retention of 86.3% at 0.1 C after 50 cycles. • Manipulating activity by supercritical CO 2 foaming technique and defect engineering. • Deciphering electrocatalytic mechanism of carbon architecture for Li–S chemistry. • Attaining advanced Li–S batteries toward practically viable application.

Simultaneously achieving fast sulfur redox kinetics and high-loading in lithium–sulfur batteries

For lithium-sulfur batteries (LSBs), searching for highly efficient host that allows for high sulfur loading and excellent lithium polysulfides (LiPSs) trapping capability is extremely important. Herein, a systematical study with regard to both experimental and theoretical of N/S heteroatoms co-doped polar surface (denoted as NSHC) is conducted to demonstrate the significance of rational structure design as well as rapid sulfur related redox kinetics for high loading cathode. With prominent merits in both heteroatoms doping and hierarchical structure, the as-fabricated NSHC/S cathode guarantees extraordinary sulfur storage, which enables fast sulfur electrochemistry under the conditions of high sulfur loading (6.72 mg cm−2), high sulfur content (80 wt%) and lean electrolyte usage (electrolyte/sulfur ratio: 7.5 μL mg−1). Of particular emphasis is the compact and high utilization of the host structure that ensures the assembled LSB with long and stable durability (606 mAh·g−1 after 100 cycles at 0.1 C and sulfur loading of 6.72 mg cm−2) and superior rate performance (689 mAh·g−1 at 5.0 C and sulfur loading of 2 mg cm−2).

LiPAA with Short‐chain Anion Facilitating Li2Sx (x ≤ 4) Reduction in Lean‐electrolyte Lithium–sulfur Battery

Lean electrolyte usage in lithium–sulfur battery (LSB) meets the demand of the high energy density. However, lean condition makes the electrolyte‐related interface discrete, leading to retardation of ion transfer that depends on interfaces. Consequently, electrochemical reactions face restraint. Herein, lithium polyacrylate acid (LiPAA) with short‐chain anions (molecular weight of 2000) is introduced into the cathode. Because of the polysulfide (PS)‐philic instinct of the short‐chain PAA anions, short‐chain PS is captured inside of the cathode. In addition, LiPAA supplies Li+ to the short‐chain PS captured. The strong interaction between Li2S4 and LiPAA effectively decreases Li2S4 migration to the anode during discharging. In a sense, the ion mass transfer pattern is thus changed comparing to traditional long‐way mode between cathode and anode. Galvanostatic intermittent titration technique (GITT) proves that the interfacial reaction resistance is greatly decreased in the region where Li2Sx (x ≤ 4) reduction contributes most. In the same time, the reversibility of electrochemical reduction/oxidation is improved. Owing to the accelerated Li2Sx (x ≤ 4) reduction, Li implanting of only 0.3 wt.% plus O introduction up to 1.4 wt.% enables the LSB perform well even with 1/4 of regular electrolyte dosage (5 μL mg−1) and high‐sulfur loading (4.2 mg cm−2), increasing its rate capacity C0.8/0.5 from 52.6% (without the LiPAA) to 92.3% (with the LiPAA) as well as a capacity of 518.7 mAh g−1 after 400 cycles at 0.8 mA cm−2.