High-performance Lithium-sulfur Batteries Research Articles

Surface-Phosphided Metal Oxide Microspheres as Catalytic Host of Sulfur to Enhance the Performance of Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are one of the most promising high-energy density secondary batteries due to their high theoretical energy density of 2600 Wh kg-1. However, the sluggish kinetics and severe "shuttle effect" of polysulfides are the well-known barriers that hinder their practical applications. A carefully designed catalytic host of sulfur may be an effective strategy that not only accelerates the conversion of polysulfides but also limit their dissolution to mitigate the "shuttle effect." Herein, in situ surface-phosphided Ni0.96Co0.03Mn0.01O (p-NCMO) oxide microspheres are prepared via gas-phase phosphidation as a catalytic host of sulfur. The as-prepared unique heterostructured microspheres, with enriched surface-coated metal phosphide, exhibit superior synergistic effect of catalytic conversion and absorption of the otherwise soluble intermediate polysulfides. Correspondingly, the sulfur cathode exhibits excellent electrochemical performance, including a high initial discharge capacity (1162 mAh gs-1 at 0.1C), long cycling stability (491 mAh gs-1 after 1000 cycles at 1C), and excellent rate performance (565 mAh gs-1 at 5C). Importantly, the newly prepared sulfur cathode shows a high areal capacity of 4.0 mAh cm-2 and long cycle stability under harsh conditions (high sulfur loading of 5.3 mg cm-2 and lean electrolyte/sulfur ratio of 5.8 μL mg-1). This work proposes an effective strategy to develop the catalytic hosts of sulfur for achieving high-performance Li-S batteries via surface phosphidation.

ZIF-67-Derived Flexible Sulfur Cathode with Improved Redox Kinetics for High-Performance Li-S Batteries.

Lithium-sulfur (Li-S) batteries have received much attention due to their high energy density and low price. In recent years, alleviating the volume expansion and suppressing the shuttle effect during the charge and discharge processes of Li-S batteries have been widely addressed. However, the slow conversion kinetics from polysulfide (LiPSs) to Li2S2/Li2S still limits the application of Li-S batteries. Therefore, we designed a ZIF-67 grown on cellulose (named ZIF-67@CL) as an electrocatalyst to improve the interconversion kinetics from LiPSs to Li2S2/Li2S for Li-S batteries. Based on the results of adsorption experiments of LiPSs, ZIF-67@CL and CL hosts were immersed in Li2S4 solution to adsorb LiPSs, and the UV-Vis test was conducted on the supernatant after adsorption. The results showed that the ZIF-67@CL had a stronger adsorption for LiPSs compared with the cellulose (CL). Furthermore, in the Li2S nucleation tests, the fabricated cells were galvanostatically discharged to 2.06 V at 0.112 mA and then potentiostatically discharged at 2.05 V. Based on the results of Li2S nucleation tests, the catalytic effect of ZIF-67 was further verified. As a result, the sulfur cathode used a ZIF-67 catalyst (named S/ZIF-67@CL) and delivered an initial capacity of 1346 mAh g-1 at a current density of 0.2 C. Even at a high current density of 2 C, it exhibited a high-capacity performance of 1087 mAh g-1 on the first cycle and maintained a capacity output of 462 mAh g-1 after 150 cycles, with a Coulombic efficiency of over 99.82%.

Layered double Hydroxides-MXene heterointerfaces with abundant anion vacancies expediting sulfur redox kinetics for High‑Performance Lithium–Sulfur batteries

Lithium-sulfur batteries (LSBs) are increasingly seen as advanced battery systems of great promise, owing to their exceptional energy density and cost-effectiveness. Yet, designing efficient electrocatalysts that can both effectively mitigate the diffusion of soluble lithium polysulfides (LiPSs) and enhance redox kinetics still remains a significant challenge, particularly at high sulfur loadings and lean electrolyte conditions. In this work, we develop NiCo-layered double hydroxides (NiCo-LDHs) nanosheets featuring abundant oxygen vacancies (Vo), anchored on Ti3C2-MXene nanosheets (denoted as Vo-LDHs-MXenes), tailored specifically for high-performance LSBs. The heterointerfaces between MXenes and Vo-LDHs modify the electronic structure and enhance the catalytic activity of the LDHs and MXenes, yielding multifunctional synergistic effects. Our theoretical and electrochemical analyses indicate that the Vo-LDHs-MXenes heterostructures exhibit enhanced affinity for LiPSs and superior catalytic performances compared to individual LDHs. This improvement facilitates the efficient adsorption and conversion of LiPSs, as well as the nucleation and decomposition of Li2S. Consequently, the cell with the Vo-LDHs-MXenes modified separator delivers stable cycling performances with a high initial specific capacity of 938.9 mAh/g over 300cycles at 1.0C and good rate capabilities. Notably, it still achieves a high initial areal capacity of 6.09 mAh cm−2 under a high sulfur loading of 6.7 mg cm−2 and low electrolyte/sulfur (E/S) ratio of 6.0 μL mg−1 over 50cycles.

Multifunctional Vanadium Nitride-Modified Separator for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are recognized as among the best potential alternative battery systems to lithium-ion batteries and have been widely investigated. However, the shuttle effect has severely restricted the advancement in their practical applications. Here, we prepare vanadium nitride (VN) nanoparticles grown in situ on a nitrogen-doped carbon skeleton (denoted as VN@NC) derived from the MAX phase and use it as separator modification materials for LSBs to suppress the shuttle effect and optimize electrochemical performance. Thanks to the outstanding catalytic performance of VN and the superior electrical conductivity of carbon skeleton derived from MAX, the synergistic effect between the two accelerates the kinetics of both lithium polysulfides (LiPSs) to Li2S and the reverse reaction, effectively suppresses the shuttle effect, and increases cathode sulfur availability, significantly enhancing the electrochemical performance of LSBs. LSBs constructed with VN@NC-modified separators achieve outstanding rate performance and cycle stability. With a capacity of 560 mAh g-1 at 4 C, it exhibits enhanced structural and chemical stability. At 1 C, the device has an incipient capacity of 1052.4 mAh g-1, and the degradation rate averaged only 0.085% over 400cycles. Meanwhile, the LSBs also show larger capacities and good cycling stability at a low electrolyte/sulfur ratio and high surface-loaded sulfur conditions. Thus, a facile and efficient way of preparing modified materials for separators is provided to realize high-performance LSBs.

MXene-Bimetallic Hybrids via Mixed Molten Salts Etching for Kinetics-Enhanced and Dendrite-Free Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries with high theoretical energy density (2600Whkg-1) are considered to be one of the most promising secondary batteries. However, the practical application of Li-S batteries is limited by the polysulfides shuttling and unstable lithium metal anodes. Herein, an asymmetric separator (CACNM@PP), composed of Co-Ni/MXene (CNM) on the cathode and Cu-Ag/MXene (CAM) on the anode for high-performance Li-S batteries is reported. For the cathode, CNM provides a synergistic effect by integrating Co, Ni, and MXene, resulting in strong chemical interactions and fast conversion kinetics for polysulfides. For the anode, CAM with abundant lithiophilicity active sites can lower the nucleation barrier of Li. Moreover, LiCl/LiF layers are generated in situ as an ion conductor layer during charging and discharging, inducing a uniform deposition of Li. Therefore, the assembled cells with the CACNM@PP separators harvest excellent electrochemical performance. This work provides novel insights into the development of commercially available high-energy density Li-S batteries with asymmetric separators.

N doped carbon supported cobalt/tungsten nitride Mott−Schottky heterojunction as an efficient electrocatalyst to enhance adsorption and conversion of lithium polysulfides for high-performance lithium–sulfur batteries

Lithium–sulfur batteries (LSBs) suffer from the dissolution of lithium polysulfides (LiPSs) which leading to capacity degradation and poor cycling stability. Hence, weʼve developed the Co/W3N4@NC Mott–Schottky heterostructures with built in electric field (BIF) are prepared as catalyst model to generate a built-in electric field to enhance the electrocatalytic effect on sulfur electrochemistry. Theoretical and experimental results have jointly demonstrated that the redistribution of charge and the presence of a built-in electric field at the Co/W3N4@NC heterointerface can promote the redox reaction within lithium sulfur battery during the discharge and charge processes, respectively. Experimental tests have confirmed its outstanding reversibility, achieving a capacity of 793.2 mAh·g−1 over 500 cycles at 1 C. It also shows excellent cycling performance with only 0.05 % attenuation per cycle over 800 cycles at 2 C for LSBs. Furthermore, even with a high sulfur loading of 5.5 mg·cm−2, the S@ Co/W3N4@NC cathode maintains favorable sulfur-related electrochemistry and delivers a high areal capacity of 3.61 mAh·cm−2 as well as maintaining considerable stability. This synthetic Mott–Schottky heterostructure not only amplifies the electrocatalytic effect in LSBs, but also advances the design of catalysts for advanced high-energy-density batteries.

Nanorod In2O3@C Modified Separator with Improved Adsorption and Catalytic Conversion of Soluble Polysulfides for High-Performance Lithium-Sulfur Batteries.

The shuttle effect of soluble lithium polysulfides (LiPSs) poses a crucial challenge for commercializing lithium-sulfur batteries. The functionalization of the separator is an effective strategy for enhancing the cell lifespan through the capture and reuse of LiPSs. Herein, a novel In2O3 nanorod with an ultrathin carbon layer (In2O3@C) was coated on a polypropylene separator. The results demonstrate the adsorption and catalysis of In2O3 on polysulfides, effectively inhibiting the shuttle effect and improving the redox kinetics of LiPSs. Besides, the ultrathin carbon layer increases the reaction sites and accelerates the electrochemical reaction rate. The cell with the In2O3@C interlayer displays excellent reversibility and stability with a 0.029% capacity decay each cycle in 2000 cycles at 2C. In addition, the In2O3@C interlayer significantly improves the cell performance under high current (888.2 mA h g-1 at 2C and room temperature) and low temperature (1007.8 mA h g-1 at 0.1C and -20 °C) conditions.

Eco-friendly aqueous binder derived from waste ramie for high-performance Li-S battery

Even the sulfur cathode in lithium-sulfur (Li-S) battery has the advantages of high theoretical energy density, wide source of raw materials, no pollution to the environment, and so on. It still suffers the sore points of easy electrode collapse due to large volume expansion during charge and discharge and low active materials utilization caused by the severe shuttle effect of lithium polysulfides (LiPSs). Therefore, in this work, ramie gum (RG) was extracted from ramie fiber degumming liquid and used as the functional binder to address the above problems and improve the Li-S battery's performance for the first time. Surprisingly, the sulfur cathode using RG binder illustrates a high initial capacity of 1152.2 mAh/g, and a reversible capacity of 644.6 mAh/g after 500 cycles at 0.5 C, far better than the sulfur cathode using polyvinylidene fluoride (PVDF) and sodium carboxymethyl cellulose (CMC) binder. More importantly, even if the active materials loading increased to as high as 4.30 mg/cm2, the area capacity is still around 3.1 mAh/cm2 after 200 cycles. Such excellent performances could be attributed to the abundant oxygen- and nitrogen-containing functional groups of RG that can effectively inhibit the shuttle effect of LiPSs, as well as the excellent viscosity and mechanical properties that can maintain electrode integrity during long-term charging/discharging. This work verifies the feasibility of RG as an eco-friendly and high-performance Li-S battery binder and provides a new idea for the utilization of agricultural biomass resources.

A highly efficient absorptive and catalytic self-supporting Fe2O3/CC host for high performance Li-S batteries

The lithium-sulfur (Li-S) battery is a promising energy storage system because of its high energy density and low cost. However, the shuttling of lithium polysulfides (LiPSs) and low conductivity of the S cathode are barriers to its practical application. Fe2O3 nanorods were grown on a carbon cloth (Fe2O3/CC) by a solvothermal reaction and calcination to obtain a cathode for the battery. The mesoporous structure of the Fe2O3 and the CC conducting network facilitates lithium-ion and electron transport. Meanwhile, the nanorod arrangement results in the exposure of more Fe2O3 active sites, which improves the adsorption and rapid conversion of LiPSs. As a result, a Li–S cell using a Fe2O3/CC cathode has a high capacity of 1 250 mAh g−1 at 0.1 C with an excellent life of over 100 cycles with a capacity retention of 67%. It also has a 70% capacity retention after 1 000 cycles at 0.2 C. The excellent electrochemical performance of the Fe2O3/CC cathode indicates its potential applications in Li-S batteries.

3D hierarchical mesoporous carbon with P and N dual-doped as electrocatalyst host for high-performance Li-S batteries

Lithium-sulfur (Li-S) batteries are thought to be the most likely to replace traditional intercalation-based lithium-ion batteries for energy storage devices because of its high theoretical mass energy density. However, the poor cycling stability resulting from dissolution of polysulfide intermediates (Li2Sx, 3≤ x ≤8) greatly hampers the commercial applications. Herein, a 3D hierarchical mesoporous carbon with P/N dual-doped (3D-PNMC) as a catalytic host for sulfur electrode is successfully prepared. The as-prepared Li-S batteries with S@3D-PNMC cathode deliver a specific capacity of 1326 mAh g−1 at 0.1 C and the corresponding area capacity of up to 5.57 mAh cm−2. And also, the calculative capacity decay rate of S@3D-PNMC cathode is only 0.05% per cycle, which significantly lower than that of S@C electrode (0.21%). The satisfactory electrochemical performance can be ascribed to the 3D host not only provides space for the active sulfur loading, but also accelerates the electron transfer inside the electrode. Especially, electroactive sites created by phosphorus and nitrogen doping can effectively improve the electrochemical reaction kinetics to achieving long cycling stability.

Synergistic Pyridinic N/Pyrrolic N configurations in rGO/CNT composite sulfur hosts for high-performance lithium-sulfur batteries

Significant progress has been made in the field of nitrogen-doped carbon sulfur host materials to address the shuttle effect, expansion effect, and conductivity issues of lithium-sulfur (Li-S) battery cathode materials. However, there has been limited study on the synergistic effects of different nitrogen configurations. In this work, ammonia and hydrazine hydrate were used as nitrogen source precursors to prepare three kinds of rGO and CNT composite sulfur hosts with different nitrogen configurations. Ammonia is conducive to the formation of Pyrrolic N, while hydrazine hydrate is conducive to the formation of Pyridinic N. Lithium-sulfur batteries assembled with 3NG/CNT/S which has similar Pyridinic N and Pyrrolic N contents, have a specific initial discharge capacity of 1345 mAh/g at 0.2 C. The initial discharge specific capacity at 2 C was 819 mAh/g, and after 400 cycles, the remaining capacity is 667 mAh/g. The synergistic impact mechanism of Pyridinic N/Pyrrolic N configurations was further revealed by first principles calculations. The results indicate that Pyridinic N/Pyrrolic N configurations enhance electronic non-locality, significantly improve the reactivity of carbon materials, reduce the Gibbs free energy during polysulfide reactions, and accelerate the reaction rate.

Rational design of bidirectional sandwich structure with etched aluminum and carbon cloth for high-performance lithium-sulfur batteries

Lithium-sulfur (Li–S) batteries are promising energy storage systems with low-cost, high-energy density and environment-friendly characteristics. Nevertheless, there are still some issues that need to be settled in practical applications, such as the migration and shuttle effect of polysulfides, the poor conductivity of sulfur, and serious volume expansions in the cycling process. To overcome these challenges, we herein assemble a bidirectional 3D sandwich structured Li–S battery with an etched porous Al current collector and a conductive carbon cloth (CC) interlayer. The sandwich structure endows the Li–S battery with a high reversible capacity, low-capacity decay, good coulombic efficiency. In addition, the battery presents a competitive energy density of 1000 Wh kg−1-S and 200 Wh kg−1-cathode with a mass loading of 1.0 mg cm−2 at 1 C. Due to the remarkable electrochemical performance, the sandwich structure provides a potential for large-scale industrial production of Li–S batteries.

Defect engineering enables an advanced separator modification for high-performance lithium-sulfur batteries

High-energy–density lithium-sulfur batteries have been rated as a promising, yet challenging, next-generation battery technology. Typically, the serious shuttle of polysulfide intermediates and sluggish solid–solid reaction kinetics often result in irreversibly sulfur loss, low Coulombic efficiency, and limited lifespan. Herein, we propose a facile and efficient separator modification strategy using a rationally designed sulfiphilic and lithiophilic mediator, i.e. in-situ confinement growth of oxygen-deficient TiO2-x nanoparticles within nitrogen-doped mesoporous carbon matrix to modulate the sulfur electrochemistry. The nanoscale defective catalyst within open mesoporous host affords favorable adsorption of polysulfides and catalytic conversion ability. Moreover, the versatile composite improves the electrolyte wettability and Li+ transfer kinetics and alleviates self-discharge behavior. Resultantly, the Li-S batteries using modified separator achieves significantly improved cycling stability with a low capacity decay of only 0.067% per cycle after 500 cycles at 2C. The defect engineering together with separator modification strategies enable efficient and durable Li-S batteries.

Active sites-rich zeolitic imidazolate framework/MXene heterostructure modified separator with improved Li+ transport for high-performance Li-S batteries

The inevitable shuttling of lithium polysulfides (LiPSs) and poor redox kinetics restrict real-world applications of lithium-sulfur (Li-S) batteries, although they have been paid plentiful attention. Herein, a thin and multifunctional heterostructure (ZIF-L/MXene), consisting of leaf-like zeolitic imidazolate framework sheets (ZIF-L) and two-dimensional layered Ti3C2Tx MXene nanosheets, is developed for modification of polyolefin-based separators. A good combination of the merits of the ZIF-L and MXene can hinder the restacking of MXene nanosheets and achieve a large specific surface area, thus exposing plentiful active sites for adsorption and catalytic reaction of LiPSs. Taking these obviously synergistic effects, the ZIF-L/MXene heterostructure modified separators not only alleviate the shuttling of LiPSs but also promote their kinetics conversion. Furthermore, with an improved electrolyte affinity, the ZIF-L/MXene modified separators can accelerate the transport of Li+. Thus, the modified separator endows a Li-S cell with an admirable discharge capacity of 1371.7 mAh g-1 at 0.2 C and favorable cycling stability, with a slow capacity decay ratio of 0.075% per cycle during 500 cycles. Even under a sulfur loading of ~ 4.1 mg cm-2, the Li-S battery can achieve an excellent capacity of 990.6 mAh g-1 at 0.1 C and maintain an excellent cycling performance. The novel ZIF-L/MXene heterostructure modified separator in this work can provide an alternative strategy for designing thin and light separators for high-performance Li-S batteries, via the enhancement of redox kinetics and reduction of shuttling of the LiPSs.

Insights into the aspect ratio effects of ordered mesoporous carbon on the electrochemical performance of sulfur cathode in lithium-sulfur batteries

Tailoring porous host materials, as an effective strategy for storing sulfur and restraining the shuttling of soluble polysulfides in electrolyte, is crucial in the design of high-performance lithium-sulfur (Li-S) batteries. However, for the widely studied conductive hosts such as mesoporous carbon, how the aspect ratio affects the confining ability to polysulfides, ion diffusion as well as the performances of Li-S batteries has been rarely studied. Herein, ordered mesoporous carbon (OMC) is chosen as a proof-of-concept prototype of sulfur host, and its aspect ratio is tuned from over ∼ 2 down to below ∼ 1.2 by using ordered mesoporous silica hard templates with variable length/width scales. The correlation between the aspect ratio of OMCs and the electrochemical performances of the corresponding sulfur-carbon cathodes are systematically studied with combined electrochemical measurements and microscopic characterizations. Moreover, the evolution of sulfur species in OMCs at different discharge states is scrutinized by small-angle X-ray scattering. This study gives insight into the aspect ratio effects of mesoporous host on battery performances of sulfur cathodes, providing guidelines for designing porous host materials for high-energy sulfur cathodes.

Porous FeNi Prussian blue cubes derived carbon-based phosphides as superior sulfur hosts for high-performance lithium–sulfur batteries

In contrast to lithium-ion batteries, lithium–sulfur batteries have higher theoretical energy density and lower cost, so they would become competitive in the practical application. However, the shuttle effect of polysulfides and slow oxidation–reduction kinetics can degrade their electrochemical performance and cycle life. In this work, we have first developed the porous FeNi Prussian blue cubes as precursors. The calcination in different atmospheres was employed to make precursors convert into common pyrolysis products or novel carbon-based phosphides, and sulfides, labeled as FeNiP/A-C, FeNiP/A-P, and FeNiP/A-S. When these products serve as host materials in the sulfur cathode, the electrochemical performance of lithium–sulfur batteries is in the order of S@FeNiP/A-P > S@FeNiP/A-S > S@FeNiP/A-C. Specifically, the initial discharge capacity of S@FeNiP/A-P can reach 679.1 mAh g−1 at 1 C, and the capacity would maintain 594.6 mAh g−1 after 300 cycles. That is because the combination of carbon-based porous structure and numerous well-dispersed Ni2P/Fe2P active sites contribute FeNiP/A-P to obtain larger lithium-ion diffusion, lower resistance, stronger chemisorption, and more excellent catalytic effect than other samples. This work may deliver that metal–organic framework-derived carbon-based phosphides are more suitable to serve as sulfur hosts than carbon-based sulfides or common pyrolysis products for enhancing Li–S batteries’ performance.

Ribosome-inspired electrocatalysts inducing preferential nucleation and growth of three-dimensional lithium sulfide for high-performance lithium-sulfur batteries

Nucleation of lithium sulfide (Li2S) induced by electrocatalysts plays a crucial role in mitigating the shuttle effect. However, short-chain polysulfides on electrocatalysts surfaces tend to re-dissolve into electrolytes, delaying Li2S supersaturation and its nucleation. In this study, we draw inspiration from the ribosome-driven protein synthesis process in cells to prepare ultrasmall nitrogen-doped MoS2 nanocrystals anchored on porous nitrogen-doped carbon networks (N-MoS2-NC) electrocatalysts. Excitedly, the ex-situ SEM demonstrates that ribosome-inspired N-MoS2-NC electrocatalysts induce early nucleation and rapid growth of three-dimensional Li2S during discharge. Theoretical calculations reveal that the Li-S bond length in N-MoS2-Li2S(100) is shorter, and the corresponding interfacial formation energy is lower than in MoS2-Li2S(100). This accelerated conversion of lithium polysulfides to Li2S can enhance the utilization of active substances and inhibit the shuttle effect. This study highlights the potential of ribosome-inspired N-MoS2-NC in improving the electrochemical stability of Li-S batteries, providing valuable insights for future electrocatalyst design.

Nitrogen-doped carbon nanorods embedded with cobalt nanoparticles as separator coatings for high-performance lithium-sulfur batteries

Nitrogen-doped carbon nanorods embedded with cobalt nanoparticles as separator coatings for high-performance lithium-sulfur batteries

The ferrocene-bonding NH2-UIO-66 as an ion sieve to intercept polysulfides and screen Li+ for upgrading performance of lithium-sulfur batteries

Intercepting polysulfides and screening Li+ is one of the most effective methods to achieve high-performance lithium-sulfur (Li-S) batteries. This study focuses on the covalent anchoring of ferrocene into NH2-UIO-66 for the modification of polypropylene (PP) separator. The introduction of ferrocene enables the reduction of the pore size of NH2-UIO-66 from 5.1 Å to 3.9 Å, thereby blocking polysulfides anions and penetrating lithium cations at the molecular level, resulting in significant inhibition in the shuttle effect of polysulfides. The cell with this functional separator exhibits a high initial specific capacity of 1490 mA h g−1 with a capacity decay of 0.018 % after 1000 cycles at 2C. This work provides an effective method of separator modification for high-performance energy storage systems.

Inhibiting shuttle effect of lithium polysulfides by double metal selenides for high-performance lithium–sulfur batteries

Inhibiting shuttle effect of lithium polysulfides by double metal selenides for high-performance lithium–sulfur batteries