Electrolyte Design for Improving Mechanical Stability of Solid Electrolyte Interphase in Lithium–Sulfur Batteries

Practical lithium–sulfur (Li−S) batteries are severely plagued by the instability of solid electrolyte interphase (SEI) formed in routine ether electrolytes. Herein, an electrolyte with 1,3,5-trioxane (TO) and 1,2-dimethoxyethane (DME) as co-solvents is proposed to construct a high-mechanical-stability SEI by enriching organic components in Li−S batteries. The high-mechanical-stability SEI works compatibly in Li−S batteries. TO with high polymerization capability can preferentially decompose and form organic-rich SEI, strengthening mechanical stability of SEI, which mitigates crack and regeneration of SEI and reduces the consumption rate of active Li, Li polysulfides, and electrolytes. Meanwhile, DME ensures high specific capacity of S cathodes. Accordingly, the lifespan of Li−S batteries increases from 75 cycles in routine ether electrolyte to 216 cycles in TO-based electrolyte. Furthermore, a 417 Wh kg⁻¹ Li−S pouch cell undergoes 20 cycles. This work provides an emerging electrolyte design for practical Li−S batteries.     

Reversible Solid–Solid Conversion of Sulfurized Polyacrylonitrile Cathodes in Lithium–Sulfur Batteries by Weakly Solvating Ether Electrolytes

Despite carbonate electrolytes exhibiting good stability to sulfurized polyacrylonitrile (SPAN), their chemical incompatibility with lithium (Li) metal anode leads to poor electrochemical performance of Li||SPAN full cells. While the SPAN employs conventional ether electrolytes that suffer from the shuttle effect, leading to rapid capacity fading. Here, we tailor a dilute electrolyte based on a low solvating power ether solvent that is both compatible with SPAN and Li metal. Unlike conventional ether electrolytes, the weakly solvating ether electrolyte enables SPAN to undergo reversibly “solid–solid” conversion. It features an anion–rich solvation structure that allows for the formation of a robust cathode electrolyte interphase on the SPAN, effectively blocking the dissolution of polysulfides into the bulk electrolyte and avoiding the shuttle effect. What's more, the unique electrolyte chemistry endowed Li ions with fast electroplating kinetics and induced high reversibility Li deposition/stripping process from 25 °C to −40 °C. Based on tailored electrolyte, Li||SPAN full cells matched with high loading SPAN cathodes (≈3.6 mAh cm⁻²) and 50 μm Li foil can operate stably over a wide range of temperatures. Additionally, Li||SPAN pouch cell under lean electrolyte and 5 % excess Li conditions can continuously operate stably for over a month.     

Revealing the CO2 Conversion at Electrode/Electrolyte Interfaces in Li–CO2 Batteries via Nanoscale Visualization Methods

Lithium–carbon dioxide (Li–CO₂) battery technology presents a promising opportunity for carbon capture and energy storage. Despite tremendous efforts in Li–CO₂ batteries, the complex electrode/electrolyte/CO₂ triple-phase interfacial processes remain poorly understood, in particular at the nanoscale. Here, using in situ atomic force microscopy and laser confocal microscopy-differential interference contrast microscopy, we directly observed the CO₂ conversion processes in Li–CO₂ batteries at the nanoscale, and further revealed a laser-tuned reaction pathway based on the real-time observations. During discharge, a bi-component composite, Li₂CO₃/C, deposits as micron-sized clusters through a 3D progressive growth model, followed by a 3D decomposition pathway during the subsequent recharge. When the cell operates under laser (λ=405 nm) irradiation, densely packed Li₂CO₃/C flakes deposit rapidly during discharge. Upon the recharge, they predominantly decompose at the interfaces of the flake and electrode, detaching themselves from the electrode and causing irreversible capacity degradation. In situ Raman shows that the laser promotes the formation of poorly soluble intermediates, Li₂C₂O₄, which in turn affects growth/decomposition pathways of Li₂CO₃/C and the cell performance. Our findings provide mechanistic insights into interfacial evolution in Li–CO₂ batteries and the laser-tuned CO₂ conversion reactions, which can inspire strategies of monitoring and controlling the multistep and multiphase interfacial reactions in advanced electrochemical devices.     

Porous Carbon Hosts for Lithium–Sulfur Batteries

Lithium–sulfur batteries (LSBs) are considered to be one of the most promising alternatives to the current lithium-ion batteries (LIBs) to meet the increasing demand for energy storage owing to their high energy density, natural abundance, low cost, and environmental friendliness. Despite great success, LSBs still suffer from several problems, including undermined capacity arising from low utilization of sulfur, unsatisfactory rate performance and poor cycling life owing to the shuttle effect of polysulfides, and poor electrical conductivity of sulfur. Under such circumstances, the design/fabrication of porous carbon–sulfur composite cathodes is regarded as an effective solution to overcome the above problems. In this review, different synthetic methods of porous carbon hosts and their corresponding integration into carbon–sulfur cathodes are summarized. The pore formation mechanism of porous carbon hosts is also addressed. The pore size effect on electrochemical performance is highlighted and compared. The enhanced mechanism of the porous carbon host on the sulfur cathode is systematically reviewed and revealed. Finally, the combination of porous carbon hosts and high-profile solid-state electrolytes is demonstrated, and the challenges to realize large-scale commercial application of porous carbon–sulfur cathodes is discussed and future trends are proposed.     

Engineering Bifunctional Host Materials of Sulfur and Lithium-Metal Based on Nitrogen-Enriched Polyacrylonitrile for Li–S Batteries

Lithium–sulfur batteries (LSBs) still suffer from the shuttle effect on the cathode and the lithium dendrite on the anode. Herein, polyacrylonitrile (PAN) is developed into a bifunctional host material to simultaneously address the challenges faced on both the sulfur cathode and lithium anode in LSBs. For the sulfur cathode, PAN is bonded with sulfur to produce sulfurized PAN (SPAN) to avoid the shuttle effect. The SPAN is accommodated into a conductive 3D CNTs-wrapped carbon foam to prepare a self-supporting cathode, which improves the electronic and ionic conductivity, and buffers the volume expansion. Thereby, it delivers reversible capacity, superb rate capability, and outstanding cycling stability. For the Li-metal anode, PAN aerogel is carbonized to give macroporous N-doped cross-linked carbon nanofiber that behaves as a lithiophilic host to regulate Li plating and suppress the growth of Li dendrite. Combining the improvements for both the cathode and anode realizes a remarkable long-term cyclability (765 mAh g⁻¹ after 300 cycles) in a full cell. It provides new opportunity to propel the practical application of advanced LSBs.     

A Dissipative Reaction Network Drives Transient Solid–Liquid and Liquid–Liquid Phase Cycling of Nanoparticles

Transient states maintained by energy dissipation are an essential feature of dynamic systems where structures and functions are regulated by fluxes of energy and matter through chemical reaction networks. Perfected in biology, chemically fueled dissipative networks incorporating nanoscale components allow the unique properties of nanomaterials to be bestowed with spatiotemporal adaptability and chemical responsiveness. We report the transient dispersion of gold nanoparticles in water, powered by dissipation of a chemical fuel. A dispersed state that is generated under non-equilibrium conditions permits fully reversible solid–liquid or liquid–liquid phase transfer. The molecular basis of the out-of-equilibrium process is reversible covalent modification of nanoparticle-bound ligands by a simple inorganic activator. Activator consumption by a coupled dissipative reaction network leads to autonomous cycling between phases. The out-of-equilibrium lifetime is tunable by adjusting the pH value, and reversible phase cycling is reproducible over several cycles.     

A Plastic–Crystal Electrolyte Interphase for All-Solid-State Sodium Batteries

The development of all-solid-state rechargeable batteries is plagued by a large interfacial resistance between a solid cathode and a solid electrolyte that increases with each charge–discharge cycle. The introduction of a plastic–crystal electrolyte interphase between a solid electrolyte and solid cathode particles reduces the interfacial resistance, increases the cycle life, and allows a high rate performance. Comparison of solid-state sodium cells with 1) solid electrolyte Na₃Zr₂(Si₂PO₄) particles versus 2) plastic–crystal electrolyte in the cathode composites shows that the former suffers from a huge irreversible capacity loss on cycling whereas the latter exhibits a dramatically improved electrochemical performance with retention of capacity for over 100 cycles and cycling at 5 C rate. The application of a plastic–crystal electrolyte interphase between a solid electrolyte and a solid cathode may be extended to other all-solid-state battery cells.     

An Organodiselenide Comediator to Facilitate Sulfur Redox Kinetics in Lithium–Sulfur Batteries with Encapsulating Lithium Polysulfide Electrolyte

Lithium–sulfur (Li–S) batteries are regarded as promising high-energy-density energy storage devices. However, the cycling stability of Li–S batteries is restricted by the parasitic reactions between Li metal anodes and soluble lithium polysulfides (LiPSs). Encapsulating LiPS electrolyte (EPSE) can efficiently suppress the parasitic reactions but inevitably sacrifices the cathode sulfur redox kinetics. To address the above dilemma, a redox comediation strategy for EPSE is proposed to realize high-energy-density and long-cycling Li–S batteries. Concretely, dimethyl diselenide (DMDSe) is employed as an efficient redox comediator to facilitate the sulfur redox kinetics in Li–S batteries with EPSE. DMDSe enhances the liquid–liquid and liquid–solid conversion kinetics of LiPS in EPSE while maintains the ability to alleviate the anode parasitic reactions from LiPSs. Consequently, a Li–S pouch cell with a high energy density of 359 Wh kg⁻¹ at cell level and stable 37 cycles is realized. This work provides an effective redox comediation strategy for EPSE to simultaneously achieve high energy density and long cycling stability in Li–S batteries and inspires rational integration of multi-strategies for practical working batteries.     

Electrolyte Regulation towards Stable Lithium-Metal Anodes in Lithium–Sulfur Batteries with Sulfurized Polyacrylonitrile Cathodes

Lithium–sulfur (Li–S) batteries are highly regarded as the next-generation energy-storage devices because of their ultrahigh theoretical energy density of 2600 Wh kg⁻¹. Sulfurized polyacrylonitrile (SPAN) is considered a promising sulfur cathode to substitute carbon/sulfur (C/S) composites to afford higher Coulombic efficiency, improved cycling stability, and potential high-energy-density Li–SPAN batteries. However, the instability of the Li-metal anode threatens the performances of Li–SPAN batteries bringing limited lifespan and safety hazards. Li-metal can react with most kinds of electrolyte to generate a protective solid electrolyte interphase (SEI), electrolyte regulation is a widely accepted strategy to protect Li-metal anodes in rechargeable batteries. Herein, the basic principles and current challenges of Li–SPAN batteries are addressed. Recent advances on electrolyte regulation towards stable Li-metal anodes in Li–SPAN batteries are summarized to suggest design strategies of solvents, lithium salts, additives, and gel electrolyte. Finally, prospects for future electrolyte design and Li anode protection in Li–SPAN batteries are discussed.     

Improvement in the Performance of Composite Cathode via Solid Electrolyte for High Electrochemical Performance of Li–S Battery

Commercialization of Li–S in present scenario is obstructed by poor performance of cathode and its compatibility with electrolyte used. Here in this work, in order to improve the electrochemical performance all solid state Li–S battery, solid electrolyte (SE) formed by composition of lithium sulfide (Li₂S) and phosphorus pentasulfide (P₂S₅) combinedly called LPS is used. The modified carbon in the form of graphene oxide (GO) and reduced graphene oxide (rGO) as additive is used to provide better electron conduction pathway. High conductivity of the order 10⁻⁴ S cm⁻¹ of prepared LPS overcomes the major drawback of insulating nature of sulfur. The coin cells are fabricated by using above mentioned material as a cathode material, LPS as SE, and lithium foil as anode. The prepared nanocomposites are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) to study structural and morphological properties. Energy dispersive X-ray spectroscopy (EDS) images of the cathode surface confirms the uniform spreading of material. The electrochemical performance of coin cell is studied by Galvanostatic charge-discharge plot at 0.1 C to check the compatibility of composite and electrolyte prepared. The cells having additive material GO and rGO with host sulfur show better results as compared to the cell having pristine sulfur.     

Petroleum Coke as the Active Material for Negative Electrodes in Lithium–Sulfur Batteries

Russian Journal of Electrochemistry - The possibility of using carbon materials based on petroleum coke as the cheap and available active material for negative electrodes of lithium–sulfur...     

Few-Layer Boron Nitride with Engineered Nitrogen Vacancies for Promoting Conversion of Polysulfide as a Cathode Matrix for Lithium–Sulfur Batteries

Lithium–sulfur (Li-S) batteries have become one of the most promising candidates as next-generation batteries, owing to their high specific capacity, low cost, and environmental benignity. Although many strategies have been proposed to restrain the shuttle of lithium polysulfides (LiPSs) through physical trapping and chemical binding, the sluggish kinetics of PS conversion still degrade the capacity, rate, and cycling performance of Li-S batteries. Herein, a novel kind of few-layer BN with engineered nitrogen vacancies (v-BN) has been developed as a cathode matrix for Li-S batteries. The positive vacancies in the BN nanosheets not only promote the immobilization and conversion of LiPSs, but also accelerate the lithium ion diffusion in cathode electrodes. Compared with pristine BN, the v-BN cathodes exhibit higher initial capacities from 775 mA h g⁻¹ to 1262 mA h g⁻¹ at 0.1 C and a high average coulombic efficiency of over 98 % during 150 cycles. Upon increasing the current density to 1 C, the cell still preserves a capacity of 406 mA h g⁻¹ after 500 cycles, exhibiting a capacity decay of only 0.084 % per cycle. The new vacancy-engineered material provides a promising method for achieving excellent performance in Li-S batteries.     

Radially Inwardly Aligned Hierarchical Porous Carbon for Ultra-Long-Life Lithium–Sulfur Batteries

Rational design of hollow micro- and/or nano-structured cathodes as sulfur hosts has potential for high-performance lithium-sulfur batteries. However, their further commercial application is hindered because infusing sulfur into hollow hosts is hard to control and the interactions between high loading sulfur and electrolyte are poor. Herein, we designed hierarchical porous hollow carbon nanospheres with radially inwardly aligned supporting ribs to mitigate these problems. Such a structure could aid the sulfur infusion and maximize sulfur utilization owing to the well-ordered pore channels. This highly organized internal carbon skeleton can also enhance the electronic conductivity. The hollow carbon nanospheres with further nitrogen-doping as the sulfur host material exhibit good capacity and excellent cycling performance (0.044 % capacity degradation per each cycle for 1000 cycles).     

Task-Specific Ionic Liquid as Reagent and Reaction Medium for the One-Pot Horner–Wadsworth–Emmons–Type Reaction Under Microwave Irradiation

A task-specific imidazolium-based phosphinite ionic liquid (IL-OPPh₂) was used as the dual solvent–reagent for the synthesis of E-cinamates and coumarin derivatives via the one-pot Horner–Wadsworth–Emmons–type reaction. The ionic liquid containing its corresponding phosphinite moiety was reacted with α-chloro esters and benzaldehyde or salicylaldehyde derivatives in the presence of sodium methoxide under microwave irradiation to produce the related E-cinamates or coumarins, respectively. The satisfactory results were obtained with good yields, short reaction time, and simple experimental procedure.     

Nickel–Ceramic Electrodes with High Nickel Content for Solid Electrolyte Electrochemical Devices

Russian Journal of Applied Chemistry - Composite powders (66 wt % NiO + 34 wt % Zr0.84Y0.16O1.92 were obtained according to the solution combustion synthesis technique by crystallization of nickel...     

Alternating Current Electrolysis for the Electrocatalytic Synthesis of Mixed Disulfide via Sulfur–Sulfur Bond Metathesis towards Dynamic Disulfide Libraries

A novel approach of electrolysis using alternating current was applied in the sulfur–sulfur bond metathesis of symmetrical disulfides towards unsymmetrical disulfides. As initially expected, a statistical distribution in disulfides was obtained. Furthermore, the influence of electrode polarisation by alternating current was investigated on a two-disulfide matrix. The highly dynamic nature of this chemistry resulted in the creation of dynamic disulfide libraries by expansion of the matrices, consisting of up to six symmetrical disulfides. In addition, mixing of matrices and stepwise expanding of a matrix by using alternating current electrolysis were realised.     

High Performance Bifunctional Electrocatalysts Designed Based on Transition-Metal Sulfides for Rechargeable Zn–Air Batteries

Due to the energy crisis by the excessive consumption of fossil fuels, Zinc–air batteries (ZABs) with high theoretical energy density have attracted people‘s attention. The overall performance of ZABs is largely determined by the air cathode catalyst. Therefore, it is necessary to develop high-efficiency and low-cost bifunctional catalysts to replace noble metal catalysts to promote the development of ZABs. Among a variety of cathode catalysts, TMS has become a research hotspot in recent years because of its better electrical conductivity than metal phosphides and metal oxides. In this work, we focus on the means of improving the electrocatalytic performance of transition-metal sulfides (TMS) providing ideas for us to rationally design high-performance catalysts. Furthermore, the performance improvement law between catalyst performance and ZABs is also discussed in this work. Finally, some challenges and opportunities faced in the research of TMS electrocatalysis are briefly proposed, and strategies for improving the performance of ZABs are prospected.     

Recent Progress in Organic–Inorganic Composite Solid Electrolytes for All-Solid-State Lithium Batteries

Conventional lithium-ion batteries, with flammable organic liquid electrolytes, have serious safety problems, which greatly limit their application. All-solid-state batteries (ASSBs) have received extensive attention from large-scale energy-storage fields, such as electric vehicles (EVs) and intelligent power grids, due to their benefits in safety, energy density, and thermostability. As the key component of ASSBs, solid electrolytes determine the properties of ASSBs. In past decades, various kinds of solid electrolytes, such as polymers and inorganic electrolytes, have been explored. Among these candidates, organic–inorganic composite solid electrolytes (CSEs) that integrate the advantages of these two different electrolytes have been regarded as promising electrolytes for high-performance ASSBs, and extensive studies have been carried out. Herein, recent progress in organic–inorganic CSEs is summarized in terms of the inorganic component, electrochemical performance, effects of the inorganic ceramic nanostructure, and ionic conducting mechanism. Finally, the main challenges and perspectives of organic–inorganic CSEs are highlighted for future development.     

Dual Dopamine Derived Polydopamine Coated N-Doped Porous Carbon Spheres as a Sulfur Host for High-Performance Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries are considered to be one of the most promising energy storage systems owing to their high energy density and low cost. However, their wide application is still limited by the rapid capacity fading. Herein, polydopamine (PDA)-coated N-doped hierarchical porous carbon spheres (NPC@PDA) are reported as sulfur hosts for high-performance Li-S batteries. The NPC core with abundant and interconnected pores provides fast electron/ion transport pathways and strong trapping ability towards lithium polysulfide intermediates. The PDA shell could further suppress the loss of lithium polysulfide intermediates through polar–polar interactions. Benefiting from the dual function design, the NPC/S@PDA composite cathode exhibits an initial capacity of 1331 mAh g⁻¹ and remains at 720 mAh g⁻¹ after 200 cycles at 0.5 C. At the pouch cell level with a high sulfur mass loading, the NPC/S@PDA composite cathode still exhibits a high capacity of 1062 mAh g⁻¹ at a current density of 0.4 mA cm⁻².     

Ionic Liquid Electrolyte with Weak Solvating Molecule Regulation for Stable Li Deposition in High-Performance Li−O2 Batteries

Li−O₂ batteries with bis(trifluoromethanesulfonyl)imide-based ionic liquid (TFSI-IL) electrolyte are promising because TFSI-IL can stabilize O₂⁻ to lower charge overpotential. However, slow Li⁺ transport in TFSI-IL electrolyte causes inferior Li deposition. Here we optimize weak solvating molecule (anisole) to generate anisole-doped ionic aggregate in TFSI-IL electrolyte. Such unique solvation environment can realize not only high Li⁺ transport parameters but also anion-derived solid electrolyte interface (SEI). Thus, fast Li⁺ transport is achieved in electrolyte bulk and SEI simultaneously, leading to robust Li deposition with high rate capability (3 mA cm⁻²) and long cycle life (2000 h at 0.2 mA cm⁻²). Moreover, Li−O₂ batteries show good cycling stability (a small overpotential increase of 0.16 V after 120 cycles) and high rate capability (1 A g⁻¹). This work provides an effective electrolyte design principle to realize stable Li deposition and high-performance Li−O₂ batteries.