Large Volume Variation Research Articles

Gradient selenium-doping regulating interfacial charge transfer in zinc sulfide/carbon anode for stable lithium storage

Metal sulfides have attracted much attentions as anode materials for lithium-ion batteries (LIBs) because of the high theoretical capacity. However, the poor electronic conductivity and large volume variation usually give rise to the rapid capacity decay and undesirable rate performance, severely hampering their practical application. Herein, a gradient selenium-doped hollow sandwich structured zinc sulfide/carbon (ZnS/C) composite (Se-HSZC) is designed and fabricated as long life-span and stable anode material for LIBs. The gradient Se-doping enhances the interfacial charge transfer in Se-HSZC, while the unique double carbon shell sandwich structure further greatly reduces the volume expansion and ensures the electron fast transportation. Consequently, the Se-HSZC anode presents outstanding rate capability (654 mAh g−1 at 2 A g−1) with remarkable reversible capacity (567 mAh g−1 after 1500 cycles at 4 A g−1) for the half battery. In particular, a reversible capacity of 457 mAh g−1 at 0.5 A g−1 is achieved after 50 cycles for the full battery with LiNi0.6Co0.2Mn0.2O2 as cathode. This work offers a promising design route of novel metal sulfides nanostructures for high performance LIBs.

Synergetic Anion Vacancies and Dense Heterointerfaces into Bimetal Chalcogenide Nanosheet Arrays for Boosting Electrocatalysis Sulfur Conversion.

Vacancy and interface engineering are regarded as effective strategies to modulate the electronic structure and enhance the activity of metal chalcogenides. However, the practical application of metal chalcogenides in lithium-sulfur (Li-S) batteries is limited by their low conductivity, rapid decline in catalytic activity, and large volume variation during the discharging/charging process. Herein, bimetal sulfide (CoZn-S) nanosheet arrays with sulfur vacancies and dense heterointerfaces are proposed to accelerate sulfur conversion and improve the performance of Li-S batteries. Systematic investigations reveal that sulfur-vacancy and build-in interfacial field in CoZn-S facilitate the electron transfer and regulate the electronic structure. The well-designed 3D nanosheet array structures shorten the ion-transport pathway and inhibit the volume fluctuation of CoZn-S during the electrocatalysis process. Density functional theory studies confirm that the built-in interfacial field and sulfur vacancy can promote the thermodynamic formation and decomposition of Li2 S, thus improving their intrinsic activity.

Realization of improved electrochemical performance for ZnCo2O4/C nanosheets through Ag coating

Regarded as a special transition metal oxide anode material, ZnCo2O4 can offer a theoretical capacity of 975 mAh g−1, which is derived from the synergistic lithium storage of the conversion reaction and alloying process. Sadly, the large volume variation in repeated charge and discharge processes and poor intrinsic conductivity have obstructed its development and popularization. In this work, a series of Ag-coated ZnCo2O4/C nanosheet composites were synthesized via a facile thermal decomposition strategy. The XRD, SEM, EDS, and XPS results confirm that Ag has covered the surface of ZnCo2O4/C. The obtained Ag-coated ZnCo2O4/C nanosheet composites display better electrochemical performance than ZnCo2O4/C, and the coating amount of Ag plays an important role. When the coating amount of Ag is set as 0.05, it can reveal the best electrochemical performance among all the Ag-coated ZnCo2O4/C nanosheet composites and deliver a capacity of 679.8 mAh g−1 after 300 cycles. The enhancement of electrochemical performance should be attributed to the elevated conductivity caused by the Ag coating.

Facile synthesis of hierarchical g-C3N4@WS2 composite as Lithium-ion battery anode

Transition metal sulfides (TMSs), as highly promising candidate anode materials, are gradually attracting the attention for lithium-ion batteries (LIBs) recently on account of its multiple valence states as well as considerable capacity. Nevertheless, TMSs have relatively low inherent electronic conductivity and large volume variation, which stands in the way of their practical applications. Herein, to ameliorate the drawbacks of TMSs, we report a hierarchical g-C3N4@WS2 composite synthesized by a solvothermal reaction. The as-synthesized g-C3N4@WS2 composite provides abundant reaction active sites for lithium storage and sufficient interspace to buffer the volume variation of WS2 nanoparticles. Moreover, the ultrathin g-C3N4 nanosheets could restraint WS2 nanoparticles from agglomeration, increase the contact chances with electrolyte and facilitate the charge transport and ion diffusion. In consequence, the optimized g-C3N4@WS2 electrode delivers a large discharge capacity (1136.1 mAh g−1 at 0.1C) and superior cycling stability (433.8 mAh g−1 after 1000 cycles). In summary, a simple method for constructing hierarchical transition metal sulfides as anode materials for LIBs is proposed.

Hierarchical Ion/Electron Networks Enable Efficient Red Phosphorus Anode with High Mass Loading for Sodium Ion Batteries

AbstractRed phosphorus (RP), with high theoretical specific capacity and low working potential, has been regarded as one of the most promising anodes for high‐performance sodium‐ion batteries (SIBs). However, the unsatisfactory performance of RP anodes especially under high mass loading conditions severely limited the development for practical applications, due to its large volume variations during cycling processes, and the poor electronic and ionic conductivity. Here, a hierarchical WDC/CNTs@RP electrode with high mass loadings of RP (up to 14.1 mg cm−2) and superior conductivity is rationally designed for both ions and electrons. Such unique hierarchical structures enable an unprecedented rate performance (1.63 mAh cm−2 under 106.6 mA cm−2), long cycling life, and a decent gravimetric capacity of 468.88 mA h g−1 based on the whole electrode and inactive components. This work presents an essential step toward practical applications of RP anode materials for SIBs batteries.

Turning carbon black into hollow carbon nanospheres to encapsulate Fe2O3 as high-performance lithium-ion batteries anode

Fe 2 O 3 are attractive anode materials for lithium-ion batteries because of their large theoretical capacity and low cost. However, due to their low conductivity, large volume variation and unstable solid electrolyte interface (SEI), their cycling stability is poor. Herein, we developed a simple and general strategy to address these issues. The well-designed yolk-shell Fe 2 O 3 @C nanospheres with the inner Fe 2 O 3 nanoparticles are protected by highly-graphitized and interconnected carbon shells prepared by oxidizing commercial acetylene black. The obtained yolk-shell Fe 2 O 3 @C nanospheres provide sufficient interior void to buffer the volumetric variation of the inner Fe 2 O 3 nanoparticles during cycling. Furthermore, the highly-graphitized and perforated mesoporous carbon shells facilitate fast electron transfer and ions transportation during the charge/discharge process. Benefiting from these structural advantages, the yolk-shell Fe 2 O 3 @C nanospheres provide good cyclic stability which still retain 929 mAh g −1 after 200 cycles at the current density of 0.1 A g −1 and elevate Li + diffusion coefficient from 3.867 × 10 −13 to 6.321 × 10 −11 m 2 s −1 . This work provides a new perspective to design the yolk-shell metal oxides@C framework for exploring the high-performance Li-ion batteries. • Acetylene blacks was constructed into hollow carbon nanospheres. • Unique chain structure and high graphitization degree of carbon shell provides an effective conductive network. • The obtained yolk-shell Fe 2 O 3 @C nanospheres provide sufficient interior void to buffer the volumetric variation of the inner Fe 2 O 3 nanoparticles during cycling. • Fe 2 O 3 @C still retain 929 mAh g −1 after 200 cycles and the Li + diffusion coefficient goes from 3.867 × 10 −13 to 6.321 × 10 −11 m 2 s −1 .

Bi nanoparticles in situ encapsulated by carbon film as high-performance anode materials for Li-ion batteries

Bismuth (Bi) has indeed inspired great interests in lithium-ion batteries (LIBs) due to the high capacity, but was still limited by the low electrical conductivity and large volume variation. Herein, a composite material based on Bi nanoparticles in situ encapsulated by carbon film (Bi@CF) is prepared successfully through a facile metal–organic framework (MOF)-engaged approach. As anode materials for LIBs, the Bi@CF composites achieved high reversible capacities of 705 and 538 mAh g−1 at 0.2 and 0.5 A g−1 after 200 cycles, and long cycling performance with a stable capacity of 306 mAh g−1 at 1.0 A g−1 even after 900 cycles. In situ X-ray diffraction (XRD) measurements clearly revealed the conversion between Bi and Li3Bi during the alloying/dealloying process, confirming the good electrochemical reversibility of Bi@CF for Li-storage. The reaction kinetics of this Bi@CF composite was further studied by galvanostatic intermittent titration technique (GITT). This work may provide an inspiration for the elaborate design and facile preparation of alloy-type anode materials for high-performance rechargeable batteries.

Electronic Structure Modulation in MoO2 /MoP Heterostructure to Induce Fast Electronic/Ionic Diffusion Kinetics for Lithium Storage.

Transition metal oxides (TMOs) are considered as the prospective anode materials in lithium‐ion batteries (LIBs). Nevertheless, the disadvantages, including large volume variation and poor electrical conductivity, obstruct these materials to meet the needs of practical application. Well‐designed mesoporous nanostructures and electronic structure modulation can enhance the electron/Li‐ions diffusion kinetics. Herein, a unique mesoporous molybdenum dioxide/molybdenum phosphide heterostructure nanobelts (meso‐MoO2/MoP‐NBs) composed of uniform nanoparticles is obtained by one‐step phosphorization process. The Mott–Schottky tests and density functional theory calculations demonstrated that meso‐MoO2/MoP‐NBs possesses superior electronic conductivity. The detailed lithium storage mechanism (solid solution reaction for MoP and partial conversion for MoO2), small change ratio of crystal structure and fast electronic/ionic diffusion behavior of meso‐MoO2/MoP‐NBs are systematically investigated by operando X‐ray diffraction, ex situ transmission electron microscopy, and kinetic analysis. Benefiting from the synergistic effects, the meso‐MoO2/MoP‐NBs displays a remarkable cycling performance (515 mAh g−1 after 1000 cycles at 1 A g−1) and excellent rate capability (291 mAh g−1 at 8 A g−1). These findings can shed light on the behavior of the electron/ion regulation in heterostructures and provide a potential route to develop high‐performance lithium‐ion storage materials.

Coupling between elastic strains and phase transition in dense pure zirconia polycrystals

A deep understanding of the solid-state phase transition processes of zirconia is a mandatory requirement for the development of new zirconia-based materials useful for many industrial applications. For five decades, the monoclinic $\ensuremath{\Leftrightarrow}$ tetragonal phase transition is described as a martensitic one and it is well known that it is associated with a large unit cell volume variation that promotes the appearance of elastic strains and also microcracking. In the present paper, we study, through in situ high temperature x-ray diffraction experiments, the coupling between strain relaxation and the martensitic phase transition into a pure zirconia bulk polycrystal. Quantitative analysis of the diffraction signal allows us to disentangle, with respect to the temperature variation, the phase transition and the microcracking processes, and we demonstrate that a high temperature postelaboration thermal treatment induces an increase in the stored elastic energy. Finally, we show that in such polycrystals exhibiting a crystal size distribution and in which the crystals are under internal stresses, the tetragonal to monoclinic phase transition process evolves from a first order one to a second order one when the temperature decreases.

Ultrasonication-assisted fabrication of porous ZnO@C nanoplates for lithium-ion batteries

Lithium-ion batteries have made significant commercial and academic progress in recent decades. Zinc oxide (ZnO) has been widely studied as a lithium-ion battery anode due to its high theoretical capacity of 987 mAh g-1, natural abundance, low cost, and environmental friendliness. However, ZnO suffers from poor electronic conductivity and large volume variation during the battery discharge/charge process, leading to capacity deterioration during long-term cycling. Herein, porous ZnO@C nanoplates are developed to offer short ion diffusion pathways and good conduction networks for both Li ions and electrons. The porous nanoplates provide abundant active sites for electrochemical reactions with minimized charge transfer impedance. As a result, the porous ZnO@C nanoplates deliver higher performance for lithium-ion storage compared with a bare ZnO anode. Furthermore, with the introduction of reduced graphene oxide (rGO), the ZnO@C@rGO composite anode achieves a capacity of 229.3 mAh g-1 at a high current density of 2 A g-1.

Insights into the sodium storage mechanism of Bi2Te3 nanosheets as superior anodes for sodium-ion batteries.

Although bismuth-based anode materials for sodium-ion batteries (SIBs) have attracted wide attention, their large volume variation hinders their actual applications, especially in Bi2Te3 systems. In this study, Bi2Te3 nanosheets (BT-Ns) are fabricated by a novel strategy via a solvent reductive reaction. The elements Bi and Te are spontaneously grown into ultrathin nanosheets because the hexagonal crystal of Bi2Te3 has a strong tendency to grow horizontally. The crystal structure of the BT-Ns is well developed and the thickness is about 1.42 nm, which can not only offer more active sites but also promote electrical conductivity and the diffusion of Na ions and electrons. It exhibits excellent rate and long-term cyclic performance, delivering 364.0 mA h g-1 at 5 A g-1 after 1200 cycles. The high rate and long-term cyclic performance of the Bi2Te3 anodes is attributed to the facile design of the 2D nanosheet structure, presenting an effective strategy to construct anodes for SIBs. The sodium storage mechanism of Bi2Te3 follows a three-step crystallographic phase change of Bi2Te3, discovered by an in situ X-ray diffraction analysis. The applicability of BT-N anodes in full cells via pairing with Na3V2(PO4)3 cathodes delivers excellent performance (energy density of 107.2 W h kg-1) and satisfactory practical applied prospects.

Ultrafast and Ultrastable Heteroarchitectured Porous Nanocube Anode Composed of CuS/FeS2 Embedded in Nitrogen-Doped Carbon for Use in Sodium-Ion Batteries.

The enhancement of the structural stability of conversion-based metal sulfides at high current densities remains a major challenge in realizing the practical application of sodium-ion batteries (SIBs). The instability of metal sulfides is caused by the large volume variation and sluggish reaction kinetics upon sodiation/desodiation. To overcome this, herein, a heterostructured nanocube anode composed of CuS/FeS2 embedded in nitrogen-doped carbon (CuS/FeS2 @NC) is synthesized. Size- and shape-controlled porous carbon nanocubes containing metallic nanoparticles are synthesized by the two-step pyrolysis of a bimetallic Prussian blue analog (PBA) precursor. The simple sulfurization-induced formation of highly conductive CuS along with FeS2 facilitates sodium-ion diffusion and enhances the redox reversibility upon cycling. The mesoporous carbon structure provides excellent electrolyte impregnation, efficient charge transport pathways, and good volume expansion buffering. The CuS/FeS2 @NC nanocube anode exhibits excellent sodium storage characteristics including high desodiation capacity (608 mAh g-1 at 0.2 A g-1 ), remarkable long-term cycle life (99.1% capacity retention after 300 cycles at 5 A g-1 ), and good rate capability up to 5 A g-1 . The simple, facile synthetic route combined with the rational design of bimetallic PBA nanostructures can be widely utilized in the development of conversion-based metal sulfides and other high-capacity anode materials for high-performance SIBs.

Pyrite as a Low-Cost Additive in Sulfur Cathode Material for Stable Cycle Performance

Various materials have been reported as an efficient host for sulfur to suppress large volume variation and polysulfide shuttle in lithium-sulfur batteries. Carbon materials are widely used as a matrix for sulfur to improve cycle performance and confine sulfur. Addition of transition metal sulfides into cathode material can improve cycle stability due to high efficiency of chemisorption and suppressing the polysulfide diffusion. In this work, various additions of pyrite to carbon and sulfur in the cathode material were investigated. The results show that the amount of pyrite has an affect on capacity and cycle stability of the electrode. Consequently, the lithium-sulfur batteries with the composite cathodes, containing 10 % of pyrite, exhibits stable discharge capacity of 788 mAh g-1 after 60 cycles at 0.2 C. Pyrite is a promising electrocatalyst in advanced lithium-sulfur batteries in the merits of low-cost, eco-friendliness and high activity towards polysulfides conversion reaction.

Metal-organomecapto complex-derived mesoporous Co1-xS/N,S-codoped carbon composite for superior lithium ion storage

Cobalt sulfide-based electrode materials were believed to have bright future in lithium-ion batteries (LIBs) application for their high theoretical capacity and excellent electrochemical stability. However, their relatively low electronic conductivity and the large volume variation during lithiation/delithiation processes usually result in low rate capability and short cycling life. Herein, a novel mesoporous Co1-xS/N,S-codoped carbon (Co1-xS/N,S–C) composite was prepared by direct pyrolysis of a cobalt-2-mercaptobenzothiazole (CoMBT) complex. High-content (91.14 ​wt%) and ultrafine (∼10 ​nm) Co1-xS nanocrystals were in-situ generated and composited with high conductive N,S-codoped carbon. The Co1-xS/N,S–C demonstrates superior Li+-ion storage performance, delivering high discharge capacities of 1207 ​mAh g−1 at 200 ​mA ​g−1 after 50 cycles and 425 ​mAh g−1 at 5 ​A ​g−1 after 1000 cycles.

Nano‐confining Red Phosphorus in a Carbon Hierarchical Superstructure for Superior Potassium Storage

AbstractHigh‐capacity red phosphorus is a promising candidate for anode material of potassium‐ion batteries while the poor electrical conductivity and large volume variation may cause severe material pulverization and performance deterioration during cycling. Incorporation of red phosphorous with porous carbon substrates is a potential strategy to solve these issues, which can spatially confine the phosphorus particles and promote mass/charge transfer processes. Herein, a hierarchical nitrogen‐doped microporous carbon superstructure derived from nanorod‐assembled metal‐organic framework superstructure was presented to confine red phosphorus (P@NCS) for potassium storage. Remarkably, P@NCS as an anode material demonstrated a high reversible specific capacity of 551 mAh g−1 at 0.1 A g−1 after 100 cycles along with a high initial Coulombic efficiency of 76 %. Control experiments and theoretical calculations verified that the excellent potassium storage performance was attributed to the strong confinement effect of the nitrogen‐doped micropores and the unique nanorod‐assembled superstructure. Furthermore, a potassium‐ion full cell was assembled using P@NCS and 3,4,9,10‐perylenetetracarboxylic dianhydride as anode and cathode material respectively, demonstrating the great potential of P@NCS for practical potassium‐ion batteries.

Polymers in Lithium-Sulfur Batteries.

Lithium–sulfur batteries (LSBs) hold great promise as one of the next‐generation power supplies for portable electronics and electric vehicles due to their ultrahigh energy density, cost effectiveness, and environmental benignity. However, their practical application has been impeded owing to the electronic insulation of sulfur and its intermediates, serious shuttle effect, large volume variation, and uncontrollable formation of lithium dendrites. Over the past decades, many pioneering strategies have been developed to address these issues via improving electrodes, electrolytes, separators and binders. Remarkably, polymers can be readily applied to all these aspects due to their structural designability, functional versatility, superior chemical stability and processability. Moreover, their lightweight and rich resource characteristics enable the production of LSBs with high‐volume energy density at low cost. Surprisingly, there have been few reviews on development of polymers in LSBs. Herein, breakthroughs and future perspectives of emerging polymers in LSBs are scrutinized. Significant attention is centered on recent implementation of polymers in each component of LSBs with an emphasis on intrinsic mechanisms underlying their specific functions. The review offers a comprehensive overview of state‐of‐the‐art polymers for LSBs, provides in‐depth insights into addressing key challenges, and affords important resources for researchers working on electrochemical energy systems.

Cluster‐Bridging‐Coordinated Bimetallic Metal−Organic Framework as High‐Performance Anode Material for Lithium‐Ion Storage

Metal−organic frameworks (MOFs) are potential electrode materials for energy storage owing to abundance of active sites, structural versatility, and well‐organized porous framework. Herein, a cluster‐bridging‐coordinated bimetallic Co4(μ4‐O)[Ir(ppy‐COO)3]2 MOF (Co4‐Ir MOF) with high conductivity and desirable porosity is proposed as promising anode materials for Li+ storage. The Co4‐Ir MOF consists of Co4(μ4‐O) clusters bridge‐coordinated by Ir(ppy‐COOH)3, leading to electrical conductivity four orders of magnitude higher than that of conventional insulating MOFs and Li+ diffusion coefficient two orders of magnitude higher than that of graphite, thus boosting rate capability. The laminated stacking structure and ordered porous framework of Co4‐Ir MOF ensure rapid Li+ transport and storage without large volume variation. As a result, Co4‐Ir MOF anodes deliver high capacity of 1202 mAh g−1, outstanding rate performance (515 mAh g−1 at 3000 mA g−1), and good cycling stability (average capacity decay of 0.041% per cycle for 1000 cycles). Soft‐packed full batteries assembled with Co4‐Ir MOF anodes and LiNi0.5Co0.2Mn0.3O2 cathodes exhibit good stability and flexibility. Moreover, Co4‐Ir MOF anode with fast kinetics is applied in hybrid lithium‐ion capacitor, demonstrating good compatibility with capacitor‐type cathode. This work suggests great potential to rationally design MOF materials with intriguing structures and performances for sustainable energy storage applications.

Sulfurized Polyacrylonitrile as a High-Performance and Low-Volume Change Anode for Robust Potassium Storage.

Potassium-ion batteries (KIBs) are considered as low-cost electrochemical energy storage technologies because of the abundant potassium resources. However, the practical applications of KIBs are mainly hampered by the unsatisfactory electrochemical performance of anode materials which often undergo large volume variations during potassiation-depotassiation, limiting their cycling life. Here, low-cost sulfurized polyacrylonitrile (S-PAN) is reported as an attractive anode candidate for KIBs. It provides a high potassium storage capacity of 569 mAh g(S-PAN)-1 with decent rate capability and cycling stability (no capacity loss after 1500 cycles, running time ∼188 days). Detailed ex situ spectroscopic and in situ microscopic characterizations reveal that the distinguished electrochemical performance of S-PAN is attributed to the high reversibility of its covalent C-S and S-S bonds which undergo repeated cleavage-redimerization during potassiation-depotassiation concomitant with relatively small volume variation (less than 24.2%). Subsequently, a full-cell constructed by pairing high-voltage K2MnFe(CN)6 cathode with high-capacity S-PAN anode demonstrates an attractive energy density (290.9 Wh kg-1) and long-term cycling stability (1200 cycles with 95.4% capacity retention). Given the high performance and low cost of both anode and cathode materials, it is believed that the present full-cell promises it as a competitive energy storage system for the cost-sensitive grid-scale applications.

Matryoshka-type carbon-stabilized hollow Si spheres as an advanced anode material for lithium-ion batteries

Silicon (Si) is regarded as the potential anode for lithium-ion batteries (LIBs), due to the remarkable theoretical specific capacity and low voltage plateau. However, the rapid capacity decay resulting from volume variation and slow electron/ion transportation of Si limit its practical application. Here, matryoshka-type carbon-stabilized hollow silicon spheres (Si/C/Si/C) are synthesized by an aluminothermic reduction and calcination process. The Si/C/Si/C anode materials prepared at 500 °C (Si/C/Si/C-500) exhibit unique structures, in which amorphous region and porous structure are preserved in the Si layers. The anode based on Si/C/Si/C-500 displays an initial specific capacity of 2792 mAh/g at a current density of 100 mA/g. At 1000 mA/g, this anode retains a reversible capacity of 1673 mAh/g, 86.9% of the initial capacity after 200 cycles. Such synthetic strategy can be employed to fabricate other high-capacity anode materials with large volume variation during charge/discharge process

PPy-encapsulated hydrangea-type 1T MoS2 microspheres as catalytic sulfur hosts for long-life and high-rate lithium-sulfur batteries

Lithium-sulfur batteries are regarded as promising candidates for next-generation energy storage applications owing to their high theoretical specific capacity, low cost, and eco-friendliness. However, the poor conductivity, large volume variation of sulfur species during the charging/discharging process, complicated conversion reactions of sulfur species, shuttle effect of lithium polysulfide, and low sulfur loading greatly hinder the practical application of lithium-sulfur batteries. In this study, we propose an efficient approach to design polypyrrole (PPy)-encapsulated 1T-MoS2 microspheres with a hydrangea-like structure as catalytic sulfur hosts for lithium-sulfur batteries. The catalytic effect of 1T-MoS2 and the high conductivity of the PPy layer accelerated the adsorption/conversion of lithium polysulfides. The hydrangea-like structure of the 1T-MoS2 microspheres provided adequate number of active sites and sufficient space for sulfur loading. Meanwhile, the specific inter-porous/outer-coating layer structure could also restrain the expansion of sulfur electrode during the electrochemical reaction process. The obtained 1T-MoS2-S@PPy cathode material exhibited outstanding electrochemical performance with an excellent reversible capacity of 1434 mAh g−1 at 0.1C rate, a considerable capacity of 1023 mAh g−1 at 1C rate, and excellent cycling stability for over 800 cycles with a low cycling decay rate of 0.051% per cycle.