Host For High-performance Lithium-sulfur Batteries Research Articles

Regulating Li2S Deposition and Accelerating Conversion Kinetics through Intracavity ZnS toward Low-Temperature Lithium-Sulfur Batteries.

The uncontrolled deposition behavior and sluggish conversion kinetics of the discharging product (solid Li2S) severely deteriorate the electrochemical performance of lithium-sulfur (Li-S) batteries, especially under high S loading and low-temperature conditions. Herein, a multifunctional S cathode host consisting of ZnS nanoparticles (NPs) confined in hollow porous carbon spheres (ZnS@HPCS) is synthesized via a unique capillary force-driven melting-diffusion strategy. The porous carbon shell of ZnS@HPCS provides a space-confined reservoir for soluble polysulfides and solid Li2S, while the intracavity ZnS NPs trap polysulfides, induce Li2S inside deposition, and accelerate conversion kinetics. Thus, Li-S batteries with ZnS@HPCS-S cathodes exhibit excellent electrochemical performance at both room and low temperatures (-40 °C) and high reversible capacities under high S loading (5.2 mg cm-2). Furthermore, Li2S nucleation/deposition, in situ Raman, and theoretical analyses reveal the underlying mechanism. This work offers fundamental insights into regulating Li2S deposition and designing S hosts for high-performance Li-S batteries.

Insight into the polysulfides conversion kinetics and its activation energy relationship on ultrafine V8C7 in Li-S batteries

Catalytic conversion of lithium polysulfides (LiPSs) is regarded as an effective approach to boosting kinetics and suppressing shuttling effect in lithium-sulfur (Li-S) batteries, but developing efficient catalysts and understanding of its catalytic mechanism still remain challenges. Herein, the ultrafine V8C7 nanocrystals embedded into the porous N-doped carbon frameworks (V8C7/NC) was designed for accelerating the LiPSs catalytic-conversion kinetics toward high-performance Li-S batteries. We propose that the ultrafine V8C7 nanocrystals with abundant unsaturated coordination atoms increase the active sites for catalytic-conversion of LiPSs and also accelerate the corresponding kinetics by reducing its reaction activation energy, meanwhile the interlinked nano-channels of V8C7/NC can effectively confine LiPSs and also promote electron/ion transfer. These attributes enable the Li-S cell equipped with V8C7/NC to deliver a large discharge capacity of 1393.3 mAh g−1 at 0.2 C, excellent rate capability (496.0 mAh g−1 at 10 C), and robust cycling stability (1000 cycles with a negligible capacity decay rate of 0.019 % per cycle even at 5 C). The innovative concept of ultrafine V8C7 nanocrystals embedded into the porous carbon toward improved LiPSs catalytic-conversion kinetics could be extended to develop other electrocatalytic hosts for high-performance Li-S batteries.

Nitrogen-doped 3D carbon hybrids based on modified lignin as sulfur host for high-performance lithium-sulfur batteries

Constructing a sulfur host with strong adsorption and catalytic conversion of polysulfides is significant in improving the electrochemical performance of lithium-sulfur batteries. In this work, we obtained nitrogen-doped 3D carbon hybridized materials (lignin porous carbon/carbon nanotubes, LPC/CNTs) by self-assembly and in situ activation methods. This is the first time to achieve nitrogen-doped carbon hybrids by melamine modification lignin as raw material. The results show that the construction of the nitrogen-doped 3D carbon hybridization network is highly correlated with the modification treatment of lignin. As sulfur host material, it can reach a specific capacity of 1300.18 mAh g−1 at 0.1 C for the first time and still has a specific capacity of 582.84 mAh g−1 at 1 C for 400 cycles. In addition, carbon hybridized materials show excellent rate performance and high current adaptability in the rate performance test compared with the carbon materials prepared from unmodified lignin. The excellent electrochemical performance is mainly attributed to the synergistic effect within the 3D interconnection network, which enhances the physical confinement and chemical adsorption of polysulfides, as well as the catalytic conversion. This work provides new insights into biomass application in the sulfur hosts of lithium-sulfur 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.

Hollow multishelled structural TiN as multi-functional catalytic host for high-performance lithium-sulfur batteries

Hollow multishelled structural TiN as multi-functional catalytic host for high-performance lithium-sulfur batteries

Bioinspired urchin-like murray carbon nanostructure with protection shell for advanced lithium-sulfur batteries

Commercial application of lithium-sulfur (Li-S) batteries is hindered by the insulating nature of sulfur and the dissolution of polysulfides. Here, a bioinspired 3D urchin-like N-doped Murray’s carbon nanostructure (N-MCN) with interconnected micro-meso-macroporous structure and a polydopamine protection shell has been designed as an effective sulfur host for high-performance Li-S batteries. The advanced 3D hierarchically porous framework with the characteristics of the generalized Murray’s law largely improves electrolyte diffusion, facilitates electrons/ions transfer and provides strong chemisorption for active species, leading to the synergistic structural and chemical confinement of polysulfides. As a result, the obtained P@S/N-MCN electrode with high areal sulfur loading demonstrates high capacity at high current densities after long cycles. This work reveals that following the generalized Murray’s law is feasible to design high-performance sulfur cathode materials for potentially practical Li-S battery applications.

Hollow carbon dual-decorated with MnO2 shielding layer and carbon nanotube as a sulfur host for Li-S batteries

The shuttle effect of polysulfides and sluggish reaction kinetics have been the main obstacles for the practical applications of lithium-sulfur (Li-S) batteries. Herein, we report a rationally designed sulfur cathode (DLHC/S@MnO2-ACNT) based on double-layered hollow carbon sphere (DLHC) decorated with manganese dioxide (MnO2) shielding layer and carbon nanotube conductive network (ACNT). The Ultramicrotome technique demonstrates that S and MnO2 nanosheets are mainly located into the interlayer of the DLHC. In the elaborate nanostructured protocol, the interlayer MnO2 nanosheets catalyze the conversion of polysulfides and the surface MnO2 nanosheets effectively adsorb polysulfides to suppress the shuttle effect. Additionally, the ACNT conductive network facilitates electrons/ions transport. Benefiting from the hierarchical confinement, Li-S batteries with DLHC/S@MnO2-ACNT composite cathodes exhibit a high reversible capacity of 1051 mAh g−1 at 0.5 C and a remarkable cycling stability over 500 cycles at 1 C. Even at a high sulfur loading of 4 mg cm−2, the cell delivers a superior areal capacity of 4.47 mAh cm−2. This work provides a new route to the design of hierarchical confinement sulfur hosts for high-performance Li-S batteries.

Cobalt-Carbon nanotubes supported on V2O3 nanorods as sulfur hosts for High-performance Lithium-Sulfur batteries

Exploring advanced sulfur cathode materials with high catalytic activity to accelerate the slow redox reactions of lithium polysulfides (LiPSs) is of great significance for lithium-sulfur batteries (LSBs). In this study, a coral-like hybrid composed of cobalt nanoparticle-embedded N-doped carbon nanotubes supported by Vanadium (III) oxide (V2O3) nanorods (Co-CNTs/C @V2O3) was designed as an efficient sulfur host using a simple annealing process. Characterization combined with electrochemical analysis confirmed that the V2O3 nanorods exhibited enhanced LiPSs adsorption capacity, and the in situ grown short-length Co-CNTs improved electron/mass transport and enhanced the catalytic activity for conversion to LiPSs. Owing to these merits, the S@Co-CNTs/C@V2O3 cathode exhibits effective capacity and cycle lifetime. Its initial capacity was 864 mAh g−1 at 1.0C and remained at 594 mAh g−1 after 800cycles with a decay rate of 0.039%. Furthermore, even at a high sulfur loading (4.5 mg cm−2), S@Co-CNTs/C@V2O3 also shows acceptable initial capacity of 880 mAh g−1 at 0.5C. This study provides new ideas for preparing long-cycle S-hosting cathodes for LSBs.

Rational engineering yolk-shell In2S3@void@carbon hybrid as polysulfide-absorbable sulfur host for high-performance lithium-sulfur batteries.

The slow redox kinetics and shuttling behavior of the intermediate lithium polysulfides constrain the further development of lithium-sulfur (Li-S) electrochemistry. A yolk-shell In2S3@void@carbon hybrid engineered to host the sulfur for Li-S batteries is prepared by using a multi-layered assembly method. The In2S3/electrolyte interface acted as powerful adsorption and activation sites for soluble polysulfides, which is demonstrated using density functional theory (DFT) calculations. Moreover, the carbon shell provides redundancy for volume-changes during the cycles. The results indicate that yolk-shell In2S3@S@C hybrid cathode shows good reversibility and rate capability, which preserves 563.6 mA h g-1 after 500 cycles at 0.5 C, indicating the potential for developing high-performance battery systems.

Shuttle-inhibited 3D sandwich MXene/SnO2QDs sulfur host for high-performance lithium-sulfur batteries

Herein, sandwich-like Ti3C2Tx MXene/SnO2 quantum dots composites were synthesized as sulfur host, aiming to alleviate the shuttle effect of polysulfides present in lithium-sulfur batteries. SnO2 quantum dots (SnO2QDs) were introduced into the interlayer of MXene through a simple electrostatic self-assembly method, and the mass fraction of SnO2QDs was controlled to construct sandwich MXene/SnO2QDs. While SnO2QDs effectively alleviating the stacking tendency of MXene, Ti and Sn co-chemisorb polysulfides and the interlayer structure physically confines polysulfides. Significantly, the synergistic effect between MXene with SnO2QDs effectively alleviates the shuttle effect of polysulfides and buffers the volume expansion. Meanwhile, with the help of the catalysis of SnO2QDs, the liquid-solid reaction kinetics of lithium polysulfides converting to Li2S2/Li2S is accelerated. Electrochemical test results showed that the MXene/SnO2QDs/S cathode has a high initial discharge specific capacity (1147.6 mAh g−1 at 0.1 C, while MXene/S is only 615.4 mAh g−1), as well as excellent rate performance and cycling stability in Li-S batteries.

MOF-derived micro-mesoporous TiO2-based composite as sulfur host for high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) battery is a promising high-energy density device. However, the shuttling of lithium polysulfide (LiPS) and severe volume variation of sulfur has hindered its practical application. Herein, a nitrogen-doped micro-mesoporous Co/NC-TiO2 composite derived from cobalt-doped MIL-125 is prepared as efficient multifunctional sulfur host. In the design of this composite, abundant micro-mesoporous structure is introduced by cobalt ion etching and ammonia treatment, which affords sufficient space for sulfur loading and adapts to large volume variation. Meanwhile, the polar TiO2 endows the composite with high sulfur affinity, and the introduction of cobalt offers strong LiPS adsorption and fast redox reaction kinetics. Accordingly, the Co/NC-TiO2 electrode achieves a specific capacity of 941 mAh g−1 at 1 C and a low capacity decay rate of 0.062% per cycle after 500 cycles. It is also capable of delivering a high capacity of 730 mAh g−1 at 3 C. At sulfur loading of 5.5 mg cm−2, the Co/NC-TiO2 electrode provides a high areal initial capacity of 5.6 mAh cm−2, showing promising application in Li-S batteries.

Rational design of 3DOM porous TiO2 matrix decorated with Co nanoparticles as novel sulfur hosts for high-performance lithium-sulfur batteries

In this work, we devise a hard-templating strategy to realize the controllable synthesis of three-dimensional ordered porous TiO2 matrix decorated with Co nanoparticles as sulfur hosts for Li/S batteries. Specifically, TiO2 matrix with unique 3D ordered porous structure not only can facilitate rapid lithium ion and electron transport, but also provide high affinity for lithium polysulfides. Besides, the Co nanoparticles embedded in TiO2 matrix possesses inherent metallic conductivity and enables boosted kinetics of polysulfide transformation to mitigate the shuttle effect. As expected, the S/3DOM Co-TiO2 perform exceptionally first discharge capacity of 929.6 mAh g−1 at 0.2 C, and improved rate discharge capacity of 517.5 mAh g−1 at 3 C, as well as an enhanced cycling performance.

Multi-functional bilayer carbon structures with micrometer-level physical encapsulation as a flexible cathode host for high-performance lithium-sulfur batteries

With the exceptional merits of high energy density, low cost, and environmental friendliness, lithium-sulfur batteries are considered to be one of the most promising next-generation flexible rechargeable batteries. However, the notorious “shuttle effect” has seriously hindered their practical applications. Herein, a strategy for designing multi-functional bilayer carbon structures is proposed, specifically, by employing a micrometer-thick graphene nanoflowers (GF) layer to encapsulate a micrometer-scale hybrid network skeleton composed of metallic Co and carbon nanotubes (CNT) as a flexible sulfur cathode host (Co/CNT@GF). Beneficial from the merits of chemical adsorption, electrocatalysis and volume expansion mitigation from the internal skeleton as well as the micrometer-level physical domain confinement by the external GF layer, the developed host could chemically trap, electrochemically catalyze, physically block and storage the lithium polysulfides. Due to the synergistic effect of these functions, the Co/CNT@GF-S delivers a superior discharge capacity of 799 mAh g−1 with a decay rate as low as 0.08 % per cycle after 400 cycles at 1 C. Even at a high sulfur loading of 8.16 mg cm−2, the average discharge capacity is as high as 5.05 mAh cm−2 in 100 cycles. This work does not only contribute to the rational design of multi-functional bilayer structures but also offers a novel design method for the commercialization of flexible lithium-sulfur batteries with high-energy–density.

Novel nitrogen-doped bamboo-structure carbon nanotubes as superior sulfur host for high-performance lithium-sulfur batteries

In this work, nitrogen-doped bamboo-structure carbon nanotubes (BCNTs) with large diameters (ranging from 50 nm to 300 nm), high specific surface area (437.41 m2·g−1) and thin tube wall (less than 8 carbon layers) were prepared as sulfur host for lithium-sulfur (Li-S) batteries. Sulfur nanoparticles (NPs) with diameters of 20–30 nm were in-situ synthesized on the surface of BCNTs by a facile ultrasonic treatment, which can enhance the binding ability between sulfur and carbon, and then improve the utilization of sulfur. It is found that the in-situ synthesized S@BCNTs composite cathode with a high sulfur content of 62.2 wt% exhibits an initial specific capacity of 1008.4 mAh·g−1 at a current density of 0.1 C, and can still maintain a capacity of 383.9 mAh·g−1 after 500 cycles. Careful composition and microstructure analyses reveal that these excellent electrochemical performance can be ascribed to the synergistic effect of conductive nitrogen doping (especially pyridinic-N and pyrrolic-N) and homogeneous sulfur coating on the surface of BCNTs, which contributes to accelerating electron transport, adsorbing polysulfides and alleviating the shuttle effect. As a result, the as-prepared nitrogen-doped BCNTs can be pretty promising cathode materials for Li-S batteries. This work can open up a new possibility for the design of stable Li-S cathodes for high-performance batteries.

Nickel nanoparticles embedded N-doped mesoporous graphitized carbon nanoflake as multifunctional sulfur host for high-performance lithium-sulfur batteries

The practical application of lithium-sulfur (Li-S) batteries has long been obstructed by the critical problems of the lithium polysulfides shuttle effect and the intrinsically sluggish sulfur redox kinetics. In this study, nickel nanoparticles were embedded in N-doped mesoporous graphitized carbon nanoflakes (Ni-NMC) through the pyrolysis of polydopamine-coated nickel flakes followed by an acidic etching process. Homogeneous mesopores and highly graphitized carbon are formed by the thermal aggregation and catalytic effect of the nickel nanoparticles during the high-temperature pyrolysis. The nickel nanoparticles remain embedded in the substrate after the acidic etching process due to the protection provided by the carbon layer. The obtained Ni-NMC consists of ca. 3-nm thickness nanoflake, with a high specific surface area of 812.2 m2 g–1, a pore volume of 1.59 cm3 g–1, and a pore size distribution of 6–8 nm. When used as a multifunctional sulfur host, the as-synthesized Ni-NMC, due to its mesoporous and thin-flake architecture, high conductivity, and catalytic effect, is simultaneously able to confine sulfur species within the carbon host and bidirectionally promote the conversion of sulfur to the final lithium sulfide. As a result, a high-performance Li-S battery with a reversible capacity of 869 mA h g–1 at 0.2 C after 100 cycles and a remarkable specific capacity of 705 mA h g–1 at 1.0 C after 200 cycles with a decay rate of 0.05 % per cycle, was realized.

Subnanometer MoP clusters confined in mesoporous carbon (CMK-3) as superior electrocatalytic sulfur hosts for high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are promising high-energy–density storage devices but severe shuttling of lithium polysulfides (LPSs), low sulfur utilization and sluggish reaction kinetics impede the practical applications. Herein, we report MoP clusters embedded in CMK-3 (cMoP-CMK-3) as a lightweight, conductive, and catalytic cathodic host with large sulfur mass loading for high energy Li-S batteries. The electronically conductive CMK-3 with ordered mesoporous channels could accommodate high loading and expansion of the active sulfur material and facilitate fast ionic/electronic transportation. The strong interaction between cMoP and CMK-3 results in concentrated Li ions inside the channels due to enhanced local electric field, significantly eliminating dead sulfur and improving sulfur utilization to over 90% due to confined catalytic effect. Moreover, the cMoP embedded into channels provide rich adsorptive and catalytic sites to effectively trap LPSs, and catalytically accelerate reaction kinetics. The resulting S@cMoP-CMK-3 cathode shows a large capacity of 1100 mAh g−1 at 0.5C (1C = 1675 mA g−1) based on the total mass of cathode, high-rate capacity of 767.8 mAh g−1 at 5C, and excellent cycle stability with 0.02% capacity fade per cycle over 500 cycles at 2C. This work demonstrates a confined catalytic strategy to improve the sulfur utilization for high-energy Li-S batteries.

Preparation of g-C3N4/CNTs composite by dissolution-precipitation method as sulfur host for high-performance lithium-sulfur batteries

For suppressing the shuttle effect of lithium polysulfides (LiPS), the sulfur carrier with the dual function of physics and chemistry has become a research hotspot. Here, we propose a new method to prepare g-C3N4 (pCN)/CNTs sulfur host by dissolution-precipitation. Protonated g-C3N4 (pCN) was uniformly dispersed in H2SO4 and electrostatically self-assembled with CNTs. The uniformly dispersed pCN nanosheets provide a strong chemical adsorption capacity for further anchoring LiPS. By adjusting the ratio of pCN/CNTs, it is proved that pCN/CNTs composite with the best ratio of pCN/CNTs at 1:1 (termed as CC1:1) has excellent electrochemical performance, when compared with other pCN/CNTs composites and pristine g-C3N4. After cycling for 500 cycles, the final discharge specific capacity of CC1:1/S cathode is 711.9 mAh g−1 at 1 C, and each cycle has a low decay rate of 0.08%.

Realizing fast polysulfides conversion within yolk-shelled NiO@HCSs nanoreactor as cathode host for high-performance lithium-sulfur batteries

A rechargeable lithium–sulfur (Li–S) battery has been considered a promising candidate due to its superior theoretical capacity and energy density.

Co,N-co-doped graphene sheet as a sulfur host for high-performance lithium-sulfur batteries.

To improve the performance of lithium-sulfur (Li–S) batteries, herein, based on the idea of designing a material that can adsorb polysulfides and improve the reaction kinetics, a Co,N-co-doped graphene composite (Co–N–G) was prepared. According to the characterization of Co–N–G, there was a homogeneous and dispersed distribution of N and Co active sites embedded in the Co–N–G sample. The 2D sheet-like microstructure and Co, N with a strong binding energy provided significant physical and chemical adsorption functions, which are conducive to the bonding S and suppression of LiPSs. Moreover, the dispersed Co and N as catalysts promoted the reaction kinetics in Li–S batteries via the reutilization of LiPSs and reduced the electrochemical resistance. Thus, the discharge specific capacity in the first cycle for the Co–N–G/S battery reached 1255.7 mA h g−1 at 0.2C. After 100 cycles, it could still reach 803.0 mA h g−1, with a retention rate of about 64%. This phenomenon proves that this type of Co–N–G composite with Co and N catalysts plays an effective role in improving the performance of batteries and can be further studied in Li–S batteries.