Sulfide Anode Research Articles

Dual-Driven Ion/Electron Migration and Sodium Storage by In Situ Introduction of Copper Ions and a Carbon-Conductive Framework in a Tin-Based Sulfide Anode.

Tin sulfide (SnS) has emerged as a promising anode material for sodium ion batteries (SIBs) due to its high theoretical capacity and large interlayer spacing. However, several challenges, such as severe insufficient electrochemical reactivity, rapid capacity degradation, and poor rate performance, still hinder its application in SIBs. In this study, in situ introduction of copper ions and a carbon conductive framework to form SnS nanocrystals embedded in a Cu2SnS3 lamellar structure heterojunction composite (SnS/Cu2SnS3/RGO) with graphene as the supporting material is proposed to achieve dual-driven sodium ion/electron migration during the continuous electrochemical process. The designed structure facilitates the preferential electrochemical reduction of copper ions into copper nanocrystals during the discharge process and functions as a catalytically active center to promote multivalence tin sodiation reaction. Furthermore, during the charging process, the presence of copper nanocrystals also facilitates efficient desodiation of NaxSn and further activates to form higher valence state sulfides. As a result, the SnS/Cu2SnS3/RGO composite demonstrates high cycling stability with a high reversible capacity of 395 mAh g-1 at 5A g-1 after 500 cycles with a capacity retention of 85.6%. In addition, the assembled Na3V2(PO4)3∥SnS/Cu2SnS3/RGO sodium ion full cell achieves 93.7% capacity retention after 80 cycles at 0.5 A g-1.

Synergistic engineering of heteroatomic N-doping and PPy modification in flower-like vanadium sulfide anode enables stable sodium storage

Vanadium sulfide, an appealing anode candidate for sodium ion batteries (SIBs), still encounters considerable volume fluctuation and sluggish Na+ diffusion kinetics, which inevitably gives rise to unsatisfactory rate capability and severe capacity decay. Herein, we successfully designed and constructed an outstanding sodium-storage feature and exceedingly stable anode for SIBs in the form of three-dimensional flower-like architecture composing of phosphorus doped VS2 wrapped by conductive elastic polypyrrole (PPy) layer (i.e., P-VS2@PPy). Through leveraging the multifunctional synergistic effect of composition and structure, involving enhanced electronic conductivity, reduced volumetric fluctuation, accelerated charge/ion transfer efficiency, and remarkable surface-capacitive behaviors can guarantee significantly enhanced electrochemical sodium-storage ability of P-VS2@PPy composites. As a consequence,such P-VS2@PPy is endowed with desirable rate characteristic accompanied with long-period cyclic lifespan (436.7 mAh/g at 20.0 A/g after 2600 cycles), which far outperform contrastive P-VS2 and pure VS2 samples. Meticulous kinetic analysis combined with theoretical simulations conclude that phosphorus doping and PPy coating have substantial effects on strengthening ionic and electron diffusion kinetics. Thorough examination and analysis of the insertion and conversion mechanisms of P-VS2@PPy was conducted through ex situ tests, revealing superior reversible phase transformation between original VS2, intermediate NaVS2, and final Na2S/V. Additionally, a practical application test demonstrates that sodium ion full-cell and hybrid capacitor based on P-VS2@PPy anode showcase significant capacity contribution and outstanding specific energy output, capable of effortlessly lighting up a LED screen.

Oxygen Self-Doping Bi2S3@C Spheric Successfully Enhanced Long-Term Performance in Lithium-Ion Batteries.

High theoretical capacity of Bi2S3 propels it toward an ideal anode material for lithium-ion batteries (LIBs); however, rapid capacity attenuation and poor long-term stability are major barriers to widespread application. In this work, an oxygen self-doping strategy was utilized to synthesize O-Bi2S3@C, significantly increasing the amount of active sites for lithium-ion storage. Meanwhile, sulfur vacancies were formed to improve the electrical conductivity and ionic transport efficiency, enhance the long-term stability, and accelerate the electrochemical kinetics of Bi2S3@C. O-BSC-S1:3 anode exhibits a reversible capacity of 673.1 mAh g-1 at 0.2 A g-1. It retains a long-term capacity of 596.3 mAh g-1 over 1100 cycles at a high density of 3 A g-1 in LIBs. Moreover, the installed O-Bi2S3@C//LiCoO2 full battery offers exceptional reversible capacity and remarkable cyclability (325.2 mAh g-1 after 200 cycles) at 0.2 A g-1. The combined strategy of oxygen self-doping and sulfur vacancy effectively enhances the reversible capacity and cycling life of Bi2S3, providing an approach for the design of high-performance transition metal sulfide anodes for LIBs.

Rational Construction of Heterostructures with n‐Type Anti‐Barrier Layer for Enhanced Electrochemical Energy Storage

AbstractAs a type of 2D materials, layered double hydroxides (LDHs) have emerged as potential candidates for electrochemical energy storage materials. To address their challenges of limited active sites and sluggish charge transfer kinetics, etc., this work presents an ingenious synchronous topochemical pathway (STP) method that enables the in situ anchoring of numerous nanosized Co9S8 on the rigid layers of LDHs. These n‐type anti‐barrier layers, generated by the ohmic contact between a quasi‐metal (Co9S8) and n‐type semiconductor (LDHs), alter the energy band structure and electron states near the Fermi level, optimizing the intrinsic conductivity and deprotonation reaction barriers of LDH materials. The prepared NiCoAl‐LDHs@Co9S8 (LCS) electrode exhibits remarkable electrochemical capacity (473.2 mAh g−¹ at 1 A g−¹) and operational stability (91.2% capacity retention after 20,000 cycles). Furthermore, an aqueous battery device constructed with LCS cathode and Fe‐Ni sulfide (FNS) anode demonstrates an impressive energy density of 118.5 Wh kg−¹ at a power density of 800 W kg−¹. This generalized structural design strategy achieves multiple enhancements in active sites, charge transfer efficiency, and structural stability of LDH materials, providing insights into the potential relationships between energy band and electrochemical performance in energy storage materials.

In Situ Lattice-Resolution Revelation of the Origins of Unexplored Anisotropic Sodiation Kinetics and Phase Transition in the Niobium Sulfide Anode.

Layered transition metal dichalcogenides (TMDs) have exhibited huge potential as anode materials for sodium-ion batteries. Most of them usually store sodium via an intercalation-conversion mechanism, but niobium sulfide (NbS2) may be an exception. Herein, through in situ transmission electron microscopy, we carefully investigated the insertion behaviors of Na ions in NbS2 and directly visualized anisotropic sodiation kinetics. Lattice-resolution imaging coupled with density functional theory calculations reveals the preferential diffusion of Na ions within layers of NbS2, accompanied by observable interlayer lattice expansion. Impressively, the Na-inserted layers can still withstand in situ mechanical testing. Further in situ observation vertical to the a/b plane of NbS2 tracked the illusive conversion reaction, which could result from interlayer gliding or wrinkling associated with stress accumulation. In situ electron diffraction measurements ruled out the possibility of such a conversion mechanism and identified a phase transition from pristine 3R-NbS2 to 2H-NaNbS2. Therefore, the NbS2 anode stores Na ions via only the intercalation mechanism, which conceptually differs from the well-known intercalation-conversion mechanism of typical TMDs. These findings not only decipher the whole sodiation process of the NbS2 anode but also provide valuable reference for unraveling the precise sodium storage mechanism in other TMDs.

Revealing Na+‐coordination induced Failure Mechanism of Metal Sulfide Anode for Sodium Ion Batteries

AbstractMetal sulfide (MS) is regarded as a promising candidate of the anode materials for sodium‐ion battery (SIB) with ideal capacity and low cost, yet still suffers from the inferior cycling stability and voltage degradation. Herein, the coordination relationship between the discharge product Na2S with the Na+ (NaPF6) in the electrolyte, is revealed as the root cause for the cycling failure of MS. Na+‐coordination effect assistants the dissolution of Na2S, further delocalizing Na2S from the reaction interface under the function of electric field, which leads to the solo oxidation of the discharge product element metal without the participation of Na2S. Besides, the higher highest occupied molecular orbital of Na2S suggest the facilitated Na2S solo oxidation to produce sodium polysulfides (NaPSs). Based on these, lowering the Na+ concentration of the electrolyte is proposed as a potential improvement strategy to change the coordination environment of Na2S, suppressing the side reactions of the solo‐oxidation of element metal and Na2S. Consequently, the enhanced conversion reaction reversibility and prolonged cycle life are achieved. This work renders in‐depth perception of failure mechanism and inspiration for realizing advanced conversion‐type anode.

Revealing Na+-coordination induced Failure Mechanism of Metal Sulfide Anode for Sodium Ion Batteries.

Metal sulfide (MS) is regarded as a promising candidate of the anode materials for sodium-ion battery (SIB) with ideal capacity and low cost, yet still suffers from the inferior cycling stability and voltage degradation. Herein, the coordination relationship between the discharge product Na2S with the Na+ (NaPF6) in the electrolyte, is revealed as the root cause for the cycling failure of MS. Na+-coordination effect assistants the dissolution of Na2S, further delocalizing Na2S from the reaction interface under the function of electric field, which leads to the solo oxidation of the discharge product element metal without the participation of Na2S. Besides, the higher highest occupied molecular orbital of Na2S suggest the facilitated Na2S solo oxidation to produce sodium polysulfides (NaPSs). Based on these, lowering the Na+ concentration of the electrolyte is proposed as a potential improvement strategy to change the coordination environment of Na2S, suppressing the side reactions of the solo-oxidation of element metal and Na2S. Consequently, the enhanced conversion reaction reversibility and prolonged cycle life are achieved. This work renders in-depth perception of failure mechanism and inspiration for realizing advanced conversion-type anode.

Mo4/3B2Tx induced hierarchical structure and rapid reaction dynamics in MoS2 anode for superior sodium storage

Molybdenum sulfide (MoS2) with large layer distance and high theoretical capacity has been identified as one of the most promising anodes for sodium ion batteries, but the poor intrinsic conductivity and severe structural agglomeration restricted its diffusion kinetic and specific capacity. In this work, the synergistic effect of heterogeneous interface and Na2S adsorption/conversion active sites was employed to construct Mo4/3B2Tx-MoS2@C composites using a self-assembly and calcination strategy. Theoretical calculation and experimental results demonstrated that the charge transfer and interface between Mo4/3B2Tx and MoS2 along with the 3D hydrangea-like structure improved the intrinsic conductivity and provided fast ion diffusion channels, boosting the electrochemical kinetics; while the favorable adsorption of Na2S and weakened Na-S bond at Mo4/3B2Tx-Mo interface optimized the recombination energies of Mo-S bond, accelerating the ion diffusion and enhancing the electrochemical reversibility. In addition, the copious sulfur vacancies provided additional active sites for ion storage, ameliorating the electrochemical capacity. As expected, the novel Mo4/3B2Tx-MoS2@C electrode delivered a satisfactory rate capacity (340.6 mAh g−1 at 1 A g−1) and durable cyclic performance (267.2 mAh g−1 after 600 cycles at 2 A g−1). When paring with Na3V2(PO4)3, the Mo4/3B2Tx-MoS2@C||Na3V2(PO4)3 full cell exhibited high energy densities of 234.0 and 131.7 Wh kg−1 at 215.7 W kg−1 and 4.4 kW kg−1, respectively. The proposed synergistic strategy of heterogeneous interface and Na2S adsorption/conversion active sites provided a new guidance for the rational design of transitional metal sulfide anodes for sodium ion batteries.

Liquid metal in prohibiting polysulfides shuttling in metal sulfides anode for sodium-ion batteries

Metal sulfides are a class of promising anode materials for sodium-ion batteries (SIBs) owing to their high theoretical specific capacity. Nevertheless, the reactant products (polysulfides) could dissolve into electrolyte, shuttle across separator, and react with sodium anode, leading to severe capacity loss and safety concerns. Herein, for the first time, gallium (Ga)-based liquid metal (LM) alloy is incorporated with MoS2 nanosheets to work as an anode in SIBs. The electron-rich, ultrahigh electrical conductivity, and self-healing properties of LM endow the heterostructured MoS2-LM with highly improved conductivity and electrode integrity. Moreover, LM is demonstrated to have excellent capability for the adsorption of polysulfides (e.g., Na2S, Na2S6, and S8) and subsequent catalytic conversion of Na2S. Consequently, the MoS2-LM electrode exhibits superior ion diffusion kinetics and long cycling performance in SIBs and even in lithium/potassium-ion battery (LIB/PIB) systems, far better than those electrodes with conventional binders (polyvinylidene difluoride (PVDF) and sodium carboxymethyl cellulose (CMC)). This work provides a unique material design concept based on Ga-based liquid metal alloy for metal sulfide anodes in rechargeable battery systems and beyond.

FeSe2 nanoparticles decorated nitrogen-doped carbon nanocubes for superior lithium-ion batteries

FeSe2 shows superior advantages as anode of lithium-ion batteries (LIBs) with abundant resources, high theoretical specific capacity, and environmentally friendly. However, the FeSe2 anode still faces great challenges balancing specific capacity, capability, and stability. In this work, we employ a self-sacrifice template of Fe-PBA coated with polydopamine to prepare FeSe2@Void@NC cubic nanostructures by one-step pyrolysis and selenization. The experimental results well elucidate the unique hollow cubic architectures with high surface area and abundant pore structure induce rapid adsorption storage, thus improving electrochemical kinetics. Benefiting from the enhanced ion diffusion kinetics and high conductivity through N-doped carbon coating, the FeSe2@Void@NC electrode demonstrates a considerable capability with a high specific capacity of 493.93 mAh g−1 (3 A g−1), and a stable cyclability with a reversible capacity of 498.5 mAh g−1 (1 A g−1) after 750 cycles. The full cells with FeSe2@Void@NC anode and LiFePO4 cathode also exhibit remarkable rate capability and stable cyclability. Our research provides profound insights into the structure engineering of alternative transition metal sulfide anode for LIBs with excellent electrochemical performance.

Engineering sulfur defective Bi2S3@C with remarkably enhanced electrochemical kinetics of lithium-ion batteries

Introducing the appropriate vacancies to augment the active sites and improve the electrochemical kinetics while maintaining high cyclability is a major challenge for its widespread application in electrochemical energy storage. Here, core–shell structured Bi2S3@C with sulfur vacancies was prepared by hydrothermal method and one-step carbonization/sulfuration process, which significantly improves the intrinsic electrical conductivity and ion transport efficiency of Bi2S3. Additionally, the uniform protective carbon layer around surface of composite maintains structural stability and effectively alleviates volume expansion during alloying/dealloying. As a result, the BSC-500 anode exhibits a brilliant reversible capacity of 636 mAh/g at 0.2 A/g and a long-term stable capacity of 524 mAh/g for 500 cycles at a high current density of 3 A/g in lithium-ion batteries. In addition, the assembled Bi2S3@C//LiCoO2 full cell delivered a capacity of 184 mAh/g at 1 A/g and excellent cyclability (125 mAh/g after 1000 cycles). The proposed strategy of combining sulfur vacancies with a core–shell structure to improve the electrochemical kinetics of Bi2S3 in lithium-ion batteries off the prospect for practical applications of transition metal sulfide anodes.

Unraveling high efficiency multi-step sodium storage and bidirectional redox kinetics synergy mechanism of cobalt-doping vanadium disulfide anode

Sodium-based storage devices based on conversion-type metal sulfide anodes have attracted great attention due to their multivalent ion redox reaction ability. However, they also suffer from sodium polysulfides (NaPSs) shuttling problems during the sluggish Na+ redox process, leading to “voltage failure” and rapid capacity decay. Herein, a metal cobalt-doping vanadium disulfide (Co-VS2) is proposed to simultaneously accelerate the electrochemical reaction of VS2 and enhance the bidirectional redox of soluble NaPSs. It is found that the strong adsorption of NaPSs by V-Co alloy nanoparticles formed in situ during the conversion reaction of Co-VS2 can effectively inhibit the dissolution and shuttle of NaPSs, and thermodynamically reduce the formation energy barrier of the reaction path to effectively drive the complete conversion reaction, while the metal transition of Co elements enhances reconversion kinetics to achieve high reversibility. Moreover, Co-VS2 also produce abundant sulfur vacancies and unsaturated sulfur edge defects, significantly improve ionic/electron diffusion kinetics. Therefore, the Co-VS2 anode exhibits ultrahigh rate capability (562 mA h g−1 at 5 A g−1), high initial coulombic efficiency (≈90%) and 12,000 ultralong cycle life with capacity retention of 90% in sodium-ion batteries (SIBs), as well as impressive energy/power density (118 Wh kg−1/31,250 W kg−1) and over 10,000 stable cycles in sodium-ion hybrid capacitors (SIHCs). Moreover, the pouch cell-type SIHC displays a high-energy density of 102 Wh kg−1 and exceed 600 stable cycles. This work deepens the understanding of the electrochemical reaction mechanism of conversion-type metal sulfide anodes and provides a valuable solution to the shuttling of NaPSs in SIBs and SIHCs.

NixSy/N, S-codoped carbon (NSC) hollow microspheres derived from a novel metal organic porous polymer for high performance lithium ion batteries

Addressing the challenges of volume expansion and polysulfide dissolution in transition metal sulfide (MxSy) anodes during the cycling process of lithium-ion batteries (LIBs) is crucial for their practical application. This work utilizes a novel organic ligand containing a thiol group, 5-mercapto-1-phenyl-1H-tetrazole (PTA), to design a series of metal-organic porous polymers, which are then derivatized into N, S co-doped MxSy@carbon encapsing materials. The PTA organic ligand not only serves as a dopants source of N and S but also undergoes in-situ sulfurization with metal to form MxSy nanoparticles coated with carbon. Particularly, the derived NixSy@carbon hollow microspheres feature a unique hollow spherical carbon structure that not only mitigates the volume expansion of nickel sulfide but also shortens the ion diffusion distance while providing a significant number of active sites in LIBs. The research also revealed that variations in crystal structures caused by temperature have a profound influence on the Li+ storage capabilities of the LIBs. When evaluated as anode materials for LIBs, the NiS1.03@NSC600 demonstrates excellent reversible specific capacity and good long-life cycling stability. After 700 charge/discharge cycles, the NiS1.03@NSC600 anode maintains a reversible specific capacity of 480.4 mAh g−1 at 1 A g−1. In addition, we also evaluated CuxSy@NSC and CoxSy@NSC as anode materials, both of which demonstrated excellent electrochemical performance.

Chemical/Electrochemical Dual‐Driven Transition Behavior of Copper Element from Current Collector to Chalcogenide Anode in Sodium‐Ion Batteries

AbstractThe transition phenomenon involving copper replacing the transition metal elements within transition metal chalcogenides (TMCs) is a recent and unique observation in the context of sodium ion batteries (SIBs) where TMCs serve as anodes. Fundamental understanding of the driving forces and kinetics governing this transition is crucial for elucidating the sodium storage mechanism in TMCs anodes. Herein, cobalt disulfide (CoS2) has been chosen as a representative anode. It is revealed that the transition behavior of copper replacing cobalt during the cycling originates from chemical/electrochemical dual‐driving forces. The chemical driving force emanates from the interaction between Cu+ dissolved in the electrolyte and the resulting sodium polysulfide products. The reaction extent is intricately linked to the surface roughness of the copper collector. The electrochemistrical driving force is effectively elucidated through the application of the Hard‐Soft‐Acid‐Base theory. Multiple charaterization techniques, such as Solid‐state nuclear magnetic resonance (ssNMR) have been employed to confirm that cobalt exists as cation instead of metal after transition. This research offers a novel perspective understanding the transition behavior exhibited by CoS2, with potential wider implications for understanding analogous behaviors in other metal sulfide anodes.

Sodium storage performance of a high entropy sulfide anode with reduced volume expansion

The introduction of a high-entropy structure into multi-metal sulfides has successfully mitigated volume expansion during the cycling process of sodium-ion batteries!

3D Fast Sodium Transport Network of MoS2 Endowed by Coupling of Sulfur Vacancies and Sn Doping for Outstanding Sodium Storage.

A sulfur vacancy-rich, Sn-doped as well as carbon-coated MoS2 composite (Vs-SMS@C) is rationally synthesized via a simple hydrothermal method combined with ball-milling reduction, which enhances the sodium storage performance. Benefiting from the 3D fast Na+ transport network composed of the defective carbon coating, Mo─S─C bonds, enlarged interlayer spacing, S-vacancies, and lattice distortion in the composite, the Na+ storage kinetics is significantly accelerated. As expected, Vs-SMS@C releases an ultrahigh reversible capacity of 1089 mAh g-1 at 0.1 A g-1, higher than the theoretical capacity. It delivers a satisfactory capacity of 463 mAh g-1 at a high current density of 10 A g-1, which is the state-of-the-art rate capability compared to other MoS2 based sodium ion battery anodes to the knowledge. Moreover, a super long-term cycle stability is achieved by Vs-SMS@C, which keeps 91.6% of the initial capacity after 3000 cycles under the current density of 5 A g-1 in the voltage of 0.3-3.0V. The sodium storage mechanism of Vs-SMS@C is investigated by employing electrochemical methods and ex situ techniques. The synergistic effect between S-vacancies and doped-Sn is evidenced by DFT calculations. This work opens new ideas for seeking excellent metal sulfide anodes.

NH4 + Pre-Intercalation and Mo Doping VS2 to Regulate Nanostructure and Electronic Properties for High Efficiency Sodium Storage.

Sodium-ion hybrid capacitors (SIHCs) have attracted much attention due to integrating the high energy density of battery and high out power of supercapacitors. However, rapid Na+ diffusion kinetics in cathode is counterbalanced with sluggish anode, hindering the further advancement and commercialization of SIHCs. Here, aiming at conversion-type metal sulfide anode, taking typical VS2 as an example, a comprehensive regulation of nanostructure and electronic properties through NH4 + pre-intercalation and Mo-doping VS2 (Mo-NVS2) is reported. It is demonstrated that NH4 + pre-intercalation can enlarge the interplanar spacing and Mo-doping can induce interlayer defects and sulfur vacancies that are favorable to construct new ion transport channels, thus resulting in significantly enhanced Na+ diffusion kinetics and pseudocapacitance. Density functional theory calculations further reveal that the introduction of NH4 + and Mo-doping enhances the electronic conductivity, lowers the diffusion energy barrier of Na+, and produces stronger d-p hybridization to promote conversion kinetics of Na+ intercalation intermediates. Consequently, Mo-NVS2 delivers a record-high reversible capacity of 453 mAh g-1 at 3 A g-1 and an ultra-stable cycle life of over 20000 cycles. The assembled SIHCs achieve impressive energy density/power density of 98Wh kg-1/11.84kW kg-1, ultralong cycling life of over 15000 cycles, and very low self-discharge rate (0.84mV h-1).

BIMMOF-derived ZnS/Co9S8 heterojunctions decorated hollow carbon nanospheres as advanced anode materials for lithium-ion batteries

Metal-organic frameworks (MOFs) offer significant advantages for constructing bimetallic sulfides as anode materials for lithium-ion batteries. However, the crystal structure of pure MOFs tends to collapse during ion insertion and detachment, resulting in somewhat limited electrochemical performance. Here, the crystal size of the bimetallic organic framework (BIMMOF) is reduced by in situ growth on hollow carbon spheres (HCS) by the solvothermal method. As a result, the well-dispersed BIMMOF-derived ZnS/Co9S8 heterojunction anode material was obtained with hollow carbon spheres as support. Due to the unique structure of ZnS/Co9S8@N-HCS with ultrafine size and the synergistic effect of Zn2+ and Co2+, this anode material has excellent electrochemical performance. Especially, it exhibits a capacity of 1595 mAh g−1 after 100 cycles at 100 mA g−1 and maintains a capacity of 1109 mAh g−1 after 1800 cycles at 2500 mA g−1. The remarkable lithium storage properties demonstrated by the ZnS/Co9S8 heterostructure provide inspiration for the wide adoption of this structural design strategy to improve the electrochemical performance of bimetallic sulfide anodes.

Fast ion/electron transport enabled by MXene confined bimetallic sulfides with heterostructure toward highly effective lithium/sodium storage

Designing and constructing electrochemically reversible and stable anode materials is crucial in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Presently, the unsatisfactory transport kinetics still limits its further commercial applications. Therefore, scientific structural optimization and surface modification are urgently needed to solve this puzzle. Herein, bimetallic sulfides with heterostructure confined in MXene nanosheets (VS4/SnS2@MXene) are successfully synthesized. The distinguished electrochemical properties combined with the theory calculation confirm that the establishment of the heterogeneous interface effectively speeds up the transit of ions and electrons, enhancing the reaction kinetics of the electrode. In addition, the flexible MXene boosts the conductivity of the electrodes while mitigating volume expansion. Surprisingly, LIBs can attain an acceptable capacity of 898 mA h g−1 at 5 A/g. Additionally, a full cell with the VS4/SnS2@MXene anode has a thrilling reversible capacity of 125 mA h g−1 at 0.5 C. Furthermore, it performs better in SIBs (187 mA h g−1 at 5 A/g) as well. An innovative idea for producing metal sulfide anode materials is presented in this paper.

Exposed crystal facet regulation of Cu2S/C hollow nanocube anode for high-performance quasi-solid Ni-Cu battery and supercapacitor

Copper sulfides are promising anode materials for aqueous rechargeable devices. However their wide-spread applications have been greatly limited by the rapid activity loss, insufficient structure stability and poor conductivity. Herein, an innovative crystal-facet engineering method has been firstly proposed to remarkably improve the electrochemical reversibility and activity of the anode. And the establishment of the intimate HKUST-1 derived carbon protective layer and the utilization of the gel electrolyte have been simultaneously adopted to optimize the electrochemical reversibility and conductivity of the copper sulfide anode. With the regulation of the dominant exposed facet, the electrode possesses high specific capacitance of 1261.3 F·g−1. The assembled Ni-Cu battery and the hybrid supercapacitor deliver excellent energy densities (56.7 Wh·kg−1 and 16.7 Wh·kg−1) and admirable cycling stabilities (64.9% capacity retention after 2000 cycles and 68.8% capacity retention after 5000 cycles). In addition, the main reason for the cycling stability decay has been investigated in detail. And the density functional theory (DFT) calculations have also completely demonstrated the dramatically positive effects of the exposed facets and carbon covering layer on the improvement of the affinity between the electrode and electrolyte ions, as well as the electrical conductivity.