Direct Growth of Bismuth Film as Anode for Aqueous Rechargeable Batteries in LiOH, NaOH and KOH Electrolytes

As promising candidates for next-generation energy storage devices, aqueous rechargeable batteries are safer and cheaper than organic Li ion batteries. But due to the narrow voltage window of aqueous electrolytes, proper anode materials with low redox potential and high capacity are quite rare. In this work, bismuth electrode film was directly grown by a facile hydrothermal route and tested in LiOH, NaOH and KOH electrolytes. With low redox potential (reduction/oxidation potentials at ca. −0.85/−0.52 V vs. SCE, respectively) and high specific capacity (170 mAh·g⁻¹ at current density of 0.5 A·g⁻¹ in KOH electrolyte), Bi was demonstrated as a suitable anode material for aqueous batteries. Furthermore, by electrochemical impedance spectroscopy (EIS) analysis, we found that with smaller R_s and faster ion diffusion coefficient, Bi electrode film in KOH electrolyte exhibited better electrochemical performance than in LiOH and NaOH electrolytes.

Vanadium Nitride Nanowire Supported SnS2 Nanosheets with High Reversible Capacity as Anode Material for Lithium Ion Batteries

The vulnerable restacking problem of tin disulfide (SnS2) usually leads to poor initial reversible capacity and poor cyclic stability, which hinders its practical application as lithium ion battery anode (LIB). In this work, we demonstrated an effective strategy to improve the first reversible capacity and lithium storage properties of SnS2 by growing SnS2 nanosheets on porous flexible vanadium nitride (VN) substrates. When evaluating lithium-storage properties, the three-dimensional (3D) porous VN coated SnS2 nanosheets (denoted as CC-VN@SnS2) yield a high reversible capacity of 75% with high specific capacity of about 819 mAh g(-1) at a current density of 0.65 A g(-1). Remarkable cyclic stability capacity of 791 mAh g(-1) after 100 cycles with excellent capacity retention of 97% was also achieved. Furthermore, discharge capacity as high as 349 mAh g(-1) is still retained after 70 cycles even at a elevated current density of 13 A g(-1). The excellent performance was due to the conductive flexible VN substrate support, which provides short Li-ion and electron pathways, accommodates large volume variation, contributes to the capacity, and provides mechanical stability, which allows the electrode to maintain its structural stability.

Graphene as an Interfacial Layer for Improving Cycling Performance of Si Nanowires in Lithium-Ion Batteries

Managing interfacial instability is crucial for enhancing cyclability in lithium-ion batteries (LIBs), yet little attention has been devoted to this issue until recently. Here, we introduce graphene as an interfacial layer between the current collector and the anode composed of Si nanowires (SiNWs) to improve the cycling capability of LIBs. The atomically thin graphene lessened the stress accumulated by volumetric mismatch and inhibited interfacial reactions that would accelerate the fatigue of Si anodes. By simply incorporating graphene at the interface, we demonstrated significantly enhanced cycling stability for SiNW-based LIB anodes, with retentions of more than 2400 mAh/g specific charge capacity over 200 cycles, 2.7 times that of SiNWs on a bare current collector.

Silicon-Copper Helical Arrays for New Generation Lithium Ion Batteries

The helical array (with 10 atom % Cu) exhibits 3130 mAh g(-1) with 83% columbic efficiency and retains 83% of its initial discharge capacity after 100th cycle. Homogeneously distributed interspaces between the helical arrays accommodate high volumetric changes upon cycling and copper atoms form a conductive network to buffer the mechanical stress generated in the electrode while minimizing electrochemical agglomeration of Si. Also, ion assistance is believed to enhance the density of the helices at the bottom thus increasing the adhesion.

Hierarchical Graphene-Encapsulated Hollow SnO2@SnS2 Nanostructures with Enhanced Lithium Storage Capability

Complex hierarchical structures have received tremendous attention due to their superior properties over their constitute components. In this study, hierarchical graphene-encapsulated hollow SnO2@SnS2 nanostructures are successfully prepared by in situ sulfuration on the backbones of hollow SnO2 spheres via a simple hydrothermal method followed by a solvothermal surface modification. The as-prepared hierarchical SnO2@SnS2@rGO nanocomposite can be used as anode material in lithium ion batteries, exhibiting excellent cyclability with a capacity of 583 mAh/g after 100 electrochemical cycles at a specific current of 200 mA/g. This material shows a very low capacity fading of only 0.273% per cycle from the second to the 100th cycle, lower than the capacity degradation of bare SnO2 hollow spheres (0.830%) and single SnS2 nanosheets (0.393%). Even after being cycled at a range of specific currents varied from 100 mA/g to 2000 mA/g, hierarchical SnO2@SnS2@rGO nanocomposites maintain a reversible capacity of 664 mAh/g, which is much higher than single SnS2 nanosheets (374 mAh/g) and bare SnO2 hollow spheres (177 mAh/g). Such significantly improved electrochemical performance can be attributed to the unique hierarchical hollow structure, which not only effectively alleviates the stress resulting from the lithiation/delithiation process and maintaining structural stability during cycling but also reduces aggregation and facilitates ion transport. This work thus demonstrates the great potential of hierarchical SnO2@SnS2@rGO nanocomposites for applications as a high-performance anode material in next-generation lithium ion battery technology.

Controllable Synthesis of Copper Oxide/Carbon Core/Shell Nanowire Arrays and Their Application for Electrochemical Energy Storage

Rational design/fabrication of integrated porous metal oxide arrays is critical for the construction of advanced electrochemical devices. Herein, we report self-supported CuO/C core/shell nanowire arrays prepared by the combination of electro-deposition and chemical vapor deposition methods. CuO/C nanowires with diameters of ~400 nm grow quasi-vertically to the substrates forming three-dimensional arrays architecture. A thin carbon shell is uniformly coated on the CuO nanowire cores. As an anode of lithium ion batteries, the resultant CuO/C nanowire arrays are demonstrated to have high specific capacity (672 mAh·g⁻¹ at 0.2 C) and good cycle stability (425 mAh·g⁻¹ at 1 C up to 150 cycles). The core/shell arrays structure plays positive roles in the enhancement of Li ion storage due to fast ion/electron transfer path, good strain accommodation and sufficient contact between electrolyte and active materials.

Hollow Core-Shell SnO2/C Fibers as Highly Stable Anodes for Lithium-Ion Batteries

Given their competitive prospects for energy storage, lithium-ion batteries (LIBs) have attracted ever-intensive research interest. However, the large volume changes during cycling and structural pulverization significantly hinder the cycling stability and high capacity for lithium-alloy electrodes. Herein, novel one-dimensional (1D) hollow core-shell SnO2/C fibers were synthesized by facile coaxial electrospinning. The as-prepared fibers that possess sufficient hollow voids and nanosized SnO2 particles on the inner shell are able to serve as an anode in LIBs. The results suggest a reversible capacity of 1002 mAh g(-1) (for the initial cycle at 100 mA g(-1)), excellent rate capability, and a highly stable cycling performance with a discharge capacity of 833 mAh g(-1) after 500 cycles at 600 mA g(-1). The superior electrochemical performance is attributed to the unique hollow core-shell structure, which offers sufficient voids for alleviating the volume changes of SnO2 nanoparticles during lithiation/delithiation processes. The promising strategies and associated opportunities here demonstrate great potential in the fabrication of advanced anode materials for long-life LIBs.

In Situ Synthesis of MnS Hollow Microspheres on Reduced Graphene Oxide Sheets as High-Capacity and Long-Life Anodes for Li- and Na-Ion Batteries

Uniform MnS hollow microspheres in situ crystallized on reduced graphene oxide (RGO) nanosheets via a facile hydrothermal method. The MnS/RGO composite material was used as the anode for Na-ion batteries for the first time and exhibited excellent cycling performance, superior specific capacity, and great cycle stability and rate capability for both Li- and Na-ion batteries. Compared with nonencapsulated pure MnS hollow microspheres, these MnS/RGO nanocomposites demonstrated excellent charge-discharge stability and long cycle life. Li-ion storage testing revealed that these MnS/RGO nanocomposites deliver high discharge-charge capacities of 640 mAh g(-1) at 1.0 A g(-1) after 400 cycles and 830 mAh g(-1) at 0.5 A g(-1) after 100 cycles. The MnS/RGO nanocomposites even retained a specific capacity of 308 mAh g(-1) at a current density of 0.1 A g(-1) after 125 cycles as the anode for Na-ion batteries. The outstanding electrochemical performance of the MnS/RGO composite attributed to the RGO nanosheets greatly improved the electronic conductivity and efficiently mitigated the stupendous volume expansion during the progress of charge and discharge.

Porous Silicon Nanotube Arrays as Anode Material for Li-Ion Batteries

We report the electrochemical performance of Si nanotube vertical arrays possessing thin porous sidewalls for Li-ion batteries. Porous Si nanotubes were fabricated on stainless steel substrates using a sacrificial ZnO nanowire template method. These porous Si nanotubes are stable at multiple C-rates. A second discharge capacity of 3095 mAh g(-1) with a Coulombic efficiency of 63% is attained at a rate of C/20 and a stable gravimetric capacity of 1670 mAh g(-1) obtained after 30 cycles. The high capacity values are attributed to the large surface area offered by the porosity of the 3D nanostructures, thereby promoting lithium-ion storage according to a pseudocapacitive mechanism.

Vanadium Sulfide on Reduced Graphene Oxide Layer as a Promising Anode for Sodium Ion Battery

As an alternative system of rechargeable lithium ion batteries, sodium ion batteries revitalize researchers' interest due to the low cost, abundant sodium resources, and similar storage mechanism to lithium ion batteries. VS4 has emerged as a promising anode material for SIBs due to low cost and its unique linear chains structure that can offer potential sites for sodium storage. Herein, we present the growth of VS4 on reduced graphene oxide (rGO) as SIBs anode for the first time. The VS4/rGO anode exhibits promising performance in SIBs. It delivers a reversible capacity of 362 mAh g(-1) at 100 mA g(-1) and a good rate performance. We also investigate the sodium storage behavior of the VS4/rGO. Different than most transition metal sulfides, the VS4/rGO composite experiences a three-step separation mechanism during the sodiation process (VS4 to metallic V and Na2S, then the electrochemical mechanism is akin to Na-S). The VS4/rGO composite proves to be a promising material for rechargeable SIBs.

Scalable Production of Si Nanoparticles Directly from Low Grade Sources for Lithium-Ion Battery Anode

Silicon, one of the most promising candidates as lithium-ion battery anode, has attracted much attention due to its high theoretical capacity, abundant existence, and mature infrastructure. Recently, Si nanostructures-based lithium-ion battery anode, with sophisticated structure designs and process development, has made significant progress. However, low cost and scalable processes to produce these Si nanostructures remained as a challenge, which limits the widespread applications. Herein, we demonstrate that Si nanoparticles with controlled size can be massively produced directly from low grade Si sources through a scalable high energy mechanical milling process. In addition, we systematically studied Si nanoparticles produced from two major low grade Si sources, metallurgical silicon (∼99 wt % Si, $1/kg) and ferrosilicon (∼83 wt % Si, $0.6/kg). It is found that nanoparticles produced from ferrosilicon sources contain FeSi2, which can serve as a buffer layer to alleviate the mechanical fractures of volume expansion, whereas nanoparticles from metallurgical Si sources have higher capacity and better kinetic properties because of higher purity and better electronic transport properties. Ferrosilicon nanoparticles and metallurgical Si nanoparticles demonstrate over 100 stable deep cycling after carbon coating with the reversible capacities of 1360 mAh g(-1) and 1205 mAh g(-1), respectively. Therefore, our approach provides a new strategy for cost-effective, energy-efficient, large scale synthesis of functional Si electrode materials.

One-Dimensional Rod-Like Sb₂S₃-Based Anode for High-Performance Sodium-Ion Batteries

Due to the high theoretical capacity of 946 mAh g(-1), Sb2S3 can be employed as promising electrode material for sodium-ion batteries (SIBs). Herein, the sodium storage behaviors of one-dimensional (1D) Sb2S3-based materials (Sb2S3 and Sb2S3@C rods) are successfully studied for the first time, displaying good cyclability and rate capability owing to their unique morphology and structure. Specifically, the Sb2S3@C rods electrode presents greatly enhanced electrochemical properties, resulting from the introduction of thin carbon layers which can effectively alleviate the strain caused by the large volume change and simultaneously improve the conductivity of electrode during cycling. At a current density of 100 mA g(-1), it delivers a high capacity of 699.1 mAh g(-1) after 100 cycles, which corresponds to 95.7% of the initial reversible capacity. Even at a high current density of 3200 mA g(-1), the capacity can still reach 429 mAh g(-1). This achievement may be a significant exploration for develpoing novel 1D Sb-based materials or metal sulfide SIBs anodes.

General Strategy for Fabricating Sandwich-like Graphene-Based Hybrid Films for Highly Reversible Lithium Storage

We report a general strategy for the fabrication of freestanding sandwich-like graphene-based hybrid films by electrostatic adsorption and following reduction reaction. We demonstrate that by rational control of pH value in precursors, graphene oxide (GO) sheets can form three-dimensional (3D) sandwich frameworks with nanoparticles decorated between the layers of graphene. In our proof-of-concept study, we prepared the graphene/Si/graphene (G@Si@G) sandwich-like films. When used as negative electrode materials for lithium-ion batteries, it exhibits superior lithium-ion storage performance (∼1800 mA h g(-1) after 40 cycles at 100 mA g(-1)). Importantly, with this simple and general method, we also successfully synthesized graphene/Fe2O3/graphene and graphene/TiO2/graphene hybrid films, showing improved electrochemical performance. The good electrochemical property results from the enhanced electron transport rate, and the 3D flexible matrix to buffer volume changes during cycling. In addition, the porous sandwich structure consisting of plate-like graphene with high surface area provides effective electrolyte infiltration and promotes diffusion rate of Li(+), leading to an improved rate capability.

Electrochemically Synthesized Sb/Sb2O3 Composites as High-Capacity Anode Materials Utilizing a Reversible Conversion Reaction for Na-Ion Batteries

Sb/Sb2O3 composites are synthesized by a one-step electrodeposition process from an aqueous electrolytic bath containing a potassium antimony tartrate complex. The synthesis process involves the electrodeposition of Sb simultaneously with the chemical deposition of Sb2O3, which allows for the direct deposition of morula-like Sb/Sb2O3 particles on the current collector without using a binder. Structural characterization confirms that the Sb/Sb2O3 composites are composed of approximately 90 mol % metallic Sb and 10 mol % crystalline Sb2O3. The composite exhibits a high reversible capacity (670 mAh g(-1)) that is higher than the theoretical capacity of Sb (660 mAh g(-1)). The high reversible capacity results from the conversion reaction between Na2O and Sb2O3 that occurs additionally to the alloying/dealloying reaction of Sb with Na. Moreover, the Sb/Sb2O3 composite shows excellent cycle performance with 91.8% capacity retention over 100 cycles, and a superior rate capability of 212 mAh g(-1) at a high current density of 3300 mA g(-1). The outstanding cycle performance is attributed to an amorphous Na2O phase generated by the conversion reaction, which inhibits agglomeration of Sb particles and acts as an effective buffer against volume change of Sb during cycling.

Hierarchical Molybdenum Nitride Nanochexes by a Textured Self-Assembly in Gas-Solid Phase for the Enhanced Application in Lithium Ion Batteries

Self-assembly, as one kind of general phenomenon, has often been reported in solution chemistry. However, in gas-solid phase, it seldom has been disclosed. The MoN nanochex exhibits unique geometrical shape. Its body segment is composed of textured single crystal MoN nanowires, while its edges parallel to [1̅22̅] direction are attached by nanowires whose crystal orientation is different from that of the body segment. In this paper, the structure of the MoN nanochex is studied, and accordingly, a possible growth mechanism is proposed. We expect to extend this method to designed synthesis of many other functional materials, such as nitrides, carbides, and borides, and thereby to significantly tailor their resulting properties. Meanwhile, as one promising electrode material for Li-ion batteries (LIBs), MoN nanochex on Ti foil has been applied in the electrochemical energy storage, and stably delivered a specific capacity of 720 mAh/g with a remarkable Coulombic efficiency up to 98.5%, implying an achieved synergic effect derived from both mesoporous structure and the direct contact with the conducting substrate.

High-Performance Zn-TiC-C Nanocomposite Alloy Anode with Exceptional Cycle Life for Lithium-Ion Batteries

A Zn-based nanocomposite has been prepared through a facile, low-cost high-energy mechanochemical process and employed as an anode material for lithium-ion batteries. Structural characterization reveals that the micrometer-sized Zn-TiC-C nanocomposite is composed of Zn nanocrystals uniformly dispersed in a multifunctional TiC and conductive carbon matrix with a tap density of 1.3 g cm(-3). The Zn-TiC-C nanocomposite exhibits high reversible volumetric capacity (468 mA h cm(-3)), excellent cyclability over 800 cycles (79.2% retention), and good rate performance up to 12.5C (75% of its capacity at 0.25C rate). The enhanced electrochemical performance is mainly due to the presence of the well-mixed TiC+C matrix that plays an important role in providing high conductivity as well as mechanical buffer that mitigates the huge volume expansion and contraction during prolonged cycling. In addition, it prevents the particle growth by uniformly dispersing nanosized Zn within itself during cycling, maintaining high utilization (∼100%) and fast reaction kinetics of Zn anode.

Stabilizing Nanosized Si Anodes with the Synergetic Usage of Atomic Layer Deposition and Electrolyte Additives for Li-Ion Batteries

A substantial increase in charging capacity over long cycle periods was made possible by the formation of a flexible weblike network via the combination of Al2O3 atomic layer deposition (ALD) and the electrolyte additive vinylene carbonate (VC). Transmission electron microscopy shows that a weblike network forms after cycling when ALD and VC were used in combination that dramatically increases the cycle stability for the Si composite anode. The ALD-VC combination also showed reduced reactions with the lithium salt, forming a more stable solid electrolyte interface (SEI) absent of fluorinated silicon species, as evidenced by X-ray photoelectron spectroscopy. Although the bare Si composite anode showed only an improvement from a 56% to a 45% loss after 50 cycles, when VC was introduced, the ALD-coated Si anode showed an improvement from a 73% to a 11% capacity loss. Furthermore, the anode with the ALD coating and VC had a capacity of 630 mAh g(-1) after 200 cycles running at 200 mA g(-1), and the bare anode without VC showed a capacity of 400 mAh g(-1) after only 50 cycles. This approach can be extended to other Si systems, and the formation of this SEI is dependent on the thickness of the ALD that affects both capacity and stability.

Surface Passivation of MoO₃ Nanorods by Atomic Layer Deposition toward High Rate Durable Li Ion Battery Anodes

We demonstrate an effective strategy to overcome the degradation of MoO3 nanorod anodes in lithium (Li) ion batteries at high-rate cycling. This is achieved by conformal nanoscale surface passivation of the MoO3 nanorods by HfO2 using atomic layer deposition (ALD). At high current density such as 1500 mA/g, the specific capacity of HfO2-coated MoO3 electrodes is 68% higher than that of bare MoO3 electrodes after 50 charge/discharge cycles. After 50 charge/discharge cycles, HfO2-coated MoO3 electrodes exhibited specific capacity of 657 mAh/g; on the other hand, bare MoO3 showed only 460 mAh/g. Furthermore, we observed that HfO2-coated MoO3 electrodes tend to stabilize faster than bare MoO3 electrodes because nanoscale HfO2 layer prevents structural degradation of MoO3 nanorods. Additionally, the growth temperature of MoO3 nanorods and the effect of HfO2 layer thickness was studied and found to be important parameters for optimum battery performance. The growth temperature defines the microstructural features and HfO2 layer thickness defines the diffusion coefficient of Li-ions through the passivation layer to the active material. Furthermore, ex situ high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction were carried out to explain the capacity retention mechanism after HfO2 coating.

Dual-Phase Lithium Metal Anode Containing a Polysulfide-Induced Solid Electrolyte Interphase and Nanostructured Graphene Framework for Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries, with a theoretical energy density of 2600 Wh kg(-1), are a promising platform for high-energy and cost-effective electrochemical energy storage. However, great challenges such as fast capacity degradation and safety concerns prevent it from widespread application. With the adoption of Li metal as the anode, dendritic and mossy metal depositing on the negative electrode during repeated cycles leads to serious safety concerns and low Coulombic efficiency. Herein, we report a distinctive graphene framework structure coated by an in situ formed solid electrolyte interphase (SEI) with Li depositing in the pores as the anode of Li-S batteries. The graphene-based metal anode demonstated a superior dendrite-inhibition behavior in 70 h of lithiation, while the cell with a Cu foil based metal anode was short-circuited after only 4 h of lithiation at 0.5 mA cm(-2). The graphene-modified Li anode with SEI induced by the polysulfide-containing electrolyte improved the Coulombic efficiency to ∼97% for more than 100 cycles, while the control sample with Cu foil as the current collector exhibited huge fluctuations in Coulombic efficiency. The unblocked ion pathways and high electron conductivities of frameworks in the modified metal anode led to the rapid transfer of Li ions through the SEI and endowed the anode framework with an ion conductivity of 7.81 × 10(-2) mS cm(-1), nearly quintuple that of the Cu foil based Li metal anode. Besides, the polarization in the charge-discharge process was halved to 30 mV. The stable and efficient Li deposition was maintained after 2000 cycles. Our results indicated that nanoscale interfacial electrode engineering could be a promising strategy to tackle the intrinsic problems of lithium metal anodes, thus improving the safety of Li-S cells.

Tissue-like Silicon Nanowires-Based Three-Dimensional Anodes for High-Capacity Lithium Ion Batteries

Here, we report on the scalable synthesis and characterization of novel architecture three-dimensional (3D) high-capacity amorphous silicon nanowires (SiNWs)-based anodes with focus on studying their electrochemical degradation mechanisms. We achieved an unprecedented combination of remarkable performance characteristics, high loadings of 3-15 mAh/cm(2), a very low irreversible capacity (10% for the 3-4 mAh/cm(2) anodes), current efficiency greater than 99.5%, cycle stability (both in half cells and a LiFePO4 battery), a total capacity of 457 mAh/cm(2) over 204 cycles and fast charge-discharge rates (up to 2.7C at 20 mA/cm(2)). These SiNWs-based binder-free 3D anodes have been cycled for over 200 cycles, exhibiting a stable cycle life. Notably, it was found that the growth of the continuous SEI layer thickness, and its concomitant increase in resistivity, represents the major reason for the observed capacity loss of the SiNWs-based anodes. Importantly, these NWs-based anodes of novel architecture meet the requirements of lithium batteries for future portable, and electric-vehicle, applications.

Ultrasmall TiO2 Nanoparticles in Situ Growth on Graphene Hybrid as Superior Anode Material for Sodium/Lithium Ion Batteries

To inhibit the aggregation of TiO2 nanoparticles and to improve the electrochemical kinetics of TiO2 electrode, a hybrid material of ultrasmall TiO2 nanoparticles in situ grown on rGO nanosheets was obtained by ultraphonic and reflux methods. The size of the TiO2 particles was controlled about 10 nm, and these particles were evenly distributed across the rGO nanosheets. When used for the anode of a sodium ion battery, the electrochemical performance of this hybrid TiO2@rGO was much improved. A capacity of 186.6 mAh g(-1) was obtained after 100 cycles at 0.1 A g(-1), and 112.2 mAh g(-1) could be maintained at 1.0 A g(-1), showing a high capacity and good rate capability. On the basis of the analysis of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), the achieved excellent electrochemical performance was mainly attributed to the synergetic effect of well-dispersed ultrasmall TiO2 nanoparticles and conductive graphene network and the improved electrochemical kinetics. The superior electrochemical performance of this hybrid material on lithium storage further confirmed the positive effect of rGO.

Solid-State Fabrication of SnS2/C Nanospheres for High-Performance Sodium Ion Battery Anode

Tin disulfide (SnS2) has emerged as a promising anode material for sodium ion batteries (NIBs) due to its unique layered structure, high theoretical capacity, and low cost. Conventional SnS2 nanomaterials are normally synthesized using hydrothermal method, which is time-consuming and difficult to scale up for mass production. In this study, we develop a simple solid-state reaction method, in which the carbon-coated SnS2 (SnS2/C) anode materials were synthesized by annealing metallic Sn, sulfur powder, and polyacrylonitrile in a sealed vacuum glass tube. The SnS2/C nanospheres with unique layered structure exhibit a high reversible capacity of 660 mAh g(-1) at a current density of 50 mA g(-1) and maintain at 570 mAh g(-1) for 100 cycles with a degradation rate of 0.14% per cycle, demonstrating one of the best cycling performances in all reported SnS2/C anodes for NIBs to date. The superior cycling stability of SnS2/C electrode is attributed to the stable nanosphere morphology and structural integrity during charge/discharge cycles as evidenced by ex situ characterization.

Type I Clathrates as Novel Silicon Anodes: An Electrochemical and Structural Investigation

Silicon clathrates contain cage-like structures that can encapsulate various guest atoms or molecules. An electrochemical evaluation of type I silicon clathrates based on Ba8Al y Si46-y as the anode material for lithium-ion batteries is presented here. Postcycling characterization with nuclear magnetic resonance and X-ray diffraction shows no discernible structural or volume changes even after electrochemical insertion of 44 Li (≈1 Li/Si) into the clathrate structure. The observed properties are in stark contrast with lithiation of other silicon anodes, which become amorphous and suffer from large volume changes. The electrochemical reactions are proposed to occur as single phase reactions at approximately 0.2 and 0.4 V versus Li/Li+ during lithiation and delithiation, respectively, distinct from diamond cubic or amorphous silicon anodes. Reversible capacities as high as 499 mAh g-1 at a 5 mA g-1 rate were observed for silicon clathrate with composition Ba8Al8.54Si37.46, corresponding to ≈1.18 Li/Si. These results show that silicon clathrates could be promising durable anodes for lithium-ion batteries.

Coating lithium titanate with nitrogen-doped carbon by simple refluxing for high-power lithium-ion batteries

Nitrogen-doped carbon is coated on lithium titanate (Li4Ti5O12, LTO) via a simple chemical refluxing process, using ethylenediamine (EDA) as the carbon and nitrogen source. The process incorporates a carbon coating doped with a relatively high amount of nitrogen to form a conducting network on the LTO matrix. The introduction of N dopants in the carbon matrix leads to a higher density of C vacancies, resulting in improved lithium-ion diffusion. The uniform coating of nitrogen-doped carbon on Li4Ti5O12 (CN-LTO) enhances the electronic conductivity of a CN-LTO electrode and the corresponding electrochemical properties of the cell employing the electrode. The results of our study demonstrate that the CN-LTO anode exhibits higher rate capability and cycling performance over 100 cycles. From the electrochemical tests performed, the specific capacity of CN-LTO electrode at higher rates of 20 and 50 C are found to be 140.7 and 82.3 mAh g(-1), respectively. In addition, the CN-Li4Ti5O12 anode attained higher capacity retention of 100% at 1 C rate after 100 cycles and 92.9% at 10 C rate after 300 cycles.

Nitrogen-Enriched Porous Carbon Coating for Manganese Oxide Nanostructures toward High-Performance Lithium-Ion Batteries

Manganese oxides are promising high-capacity anode materials for lithium-ion batteries (LIBs) yet suffer from short cycle life and poor rate capability. Herein, we demonstrate a facile in situ interfacial synthesis of core-shell heterostructures comprising nitrogen-enriched porous carbon (pN-C) nanocoating and manganese oxide (MnOx) nanotubes. When MnOx/pN-C serves as an anode material for LIBs, the pN-C coating plays multiple roles in substantially improving the lithium storage performance. In combination with the nanosized structure and nanotubular architecture, the MnOx/pN-C nanocomposites exhibit an impressive reversible capacity of 1068 mAh g(-1) at 100 mA g(-1), a high-rate delivery of 361 mAh g(-1) at 8 A g(-1), and a stable cycling retention up to 300 cycles. The surface pN-C coating strategy can be extended to design and fabricate various metal oxide nanostructures for high-performance LIBs.