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Low energy density is the key issue that needs to be addressed for sodium ion batteries. Antimony sulfide (Sb 2 S 3) with high theoretical capacity is considered as an ideal anode, but it suffers from poor electrochemical activity and consequently, low energy density. Simple hollow Sb 2 S 3 structures with high electrochemical activity offer high gravimetric energy density, while large internal voids significantly decrease the volumetric energy density. Here, multi-shell Sb 2 S 3 was synthesized as an anode for sodium ion batteries, exhibiting much higher reversible capacity and gravimetric energy density than the pristine Sb 2 S 3. Moreover, the multi-shell structure presents higher volumetric energy density with enhanced durability than its single-shell counterpart due to the optimized utilization of the inner void. Operando synchrotron-based X-ray powder diffraction (XRPD) was used to verify the enhanced electrochemical activity originated from more complete conversion electrochemical reactions. The multi-shell Sb 2 S 3 design may provide a guide for the development of high-performance hollow structured anodes with preserved high energy density. Image 1 • The synthesis of multi-shell Sb 2 S 3 offers a way to enhance the volumetric energy density of anodes for sodium ion batteries. • Multi-shell hollow structured Sb 2 S 3 exhibits enhanced electrochemical activity and durability simultaneously. • Operando synchrotron-based powder diffraction reveals the origin of high gravimetric energy density of multi-shell sample. [ABSTRACT FROM AUTHOR]

Layered LiNi x Co y Mn z O 2 exhibits high capacity and energy density with low cost for lithium-ion batteries. However, the poor rate capability and strong capacity fading with prolonged cycles, which are mainly attributed to undesired side reactions at the interface between electrode and electrolyte, plague its practical applications. Surface coating is a facile and feasible strategy to address these problems. An ideal coating layer can prohibit these side reactions via acting like a physical protection barrier to avoid the direct contact with reactive electrolyte, leading to suppressed transition metals’ dissolution, oxygen loss, phase transformation and safety issues. The ionic/electronic conductivity, structural and thermal stability can be manipulated by careful selection of coating materials. This work aims to overview the recent studies in surface coating of LiNi x Co y Mn z O 2 from the perspective of improving the electronic or/and ionic conductivity. Also, current critical challenges and insight into future research outlooks are presented in detail. [ABSTRACT FROM AUTHOR]

Graphene has been extensively investigated as anode material for Li and Na ion batteries due to its excellent physical and chemical performance. Herein, we report a new member of ‘graphene family’, a reduced graphene nanowire on three-dimensional graphene foam (3DGNW). The novel graphene nanowires were synthesized via a template strategy involving reduction and assembly process of nanosized graphene oxides (nGO), pyrolysis of polystyrene spheres (PS) template and catalytic reaction between GO and PS decomposition products. When evaluated as anodes material for Li and Na ion batteries, the 3DGNW exhibits relatively low discharge-voltage plateau, excellent reversible capacity, rate capability, and durable tolerance. For anode of Na ion batteries, a reversible capacity of more than 301 mAh g −1 without capacity fading after 1000 cycles at rate of 1 C were achieved. Even at rate of 20 C, a high reversible capacity of 200 mAh g −1 can be retained. The superior electrochemical performance is ascribed to hierarchical multidimensional graphene architecture, high graphene crystallinity, expansile graphene interlayer distance, and extensively lateral exposed edges/pores, which can promote the electron and ion transport. The realization of assembling reduced graphene sheets to graphene nanowire offers new opportunities for energy storage application of graphene based assembly in future. [ABSTRACT FROM AUTHOR]

A high working voltage and fast charging/discharging capability are important to a supercapacitor device in order to achieve decent energy densities with high power. In this work, we report 2.0 V quasi-solid-state symmetric capacitive device based on Fe 2 N-Ti 2 N (FTN) core-shell nanorod array electrodes. Through a surface protection by a thin and ultra-stable Ti 2 N shell, Fe 2 N converted from its oxyhydroxide precursor inhibits the original nanorod structure. Due to advantageous features of these core-shell metal nitride electrodes (e.g., high conductivity, structure stability, direct current path), the symmetric device permits ultrahigh scan rates (up to 50 V s −1 ) and delivers fairly stable capacitance in long-term cycles (~82 F g −1 with ~99% capacitance retention in 20,000 cycles). As a result, the supercapacitor exhibits an impressive energy density of ~48.5 W h kg −1 at the power of 2700 W kg −1 . These results demonstrate the potentialities of metal nitride nanorods array for high energy density capacitive device. [ABSTRACT FROM AUTHOR]

Abstract: The performance of sodium ion batteries (SIBs) is mainly determined by the electrochemical activity and kinetic feature of electrode materials. High performance relies largely on the scrupulous design of nano-architectures and smart hybridization of bespoke active materials. It is fundamentally important for establishing a relationship between the structure/chemistry of these materials and their properties. Herein, we developed a novel synergistic Ni3S2-MoS2 core-shell nanofiber superstructure on 3D Ni/graphene foam by a one-step PVP-assisted hydrothermal reaction. Such hierarchical nanofibers can provide the homogeneous atomic heterointerface with porous hierarchical structure, resulting in the maximization of synergistic interaction. This unique structure results in very high specific capacity and rate capability as well as extremely long-term cycle stability. As anode electrode of SIBs, it exhibits a very high reversible specific capacity of 568 mAh g−1 at a current density of 200 mA g−1 with excellent rate capability (283 mAh g−1 at 5 A g−1), and the specific capacity can be well-maintained to 207 mAh g-1 at 5 A g−1 even after 400 cycles. The strategy developed in our study can open a new way to prepare other layered-material-based hybrid superstructure for next-generation energy storage devices. [ABSTRACT FROM AUTHOR]

We report the fabrication of monolithic quasi-graphene film with porous carbon frameworks (GPF), both nitrogen-doped, by a one-step pyrolysis of commercial filter membrane, and demonstrate its improved performance in Li-ion storage compared to commercial graphite. Several advantageous features (porous framework and its integrity with the quasi-graphene, N doping) of this new electrode are manifested by its high-rate and long-cycling rechargeable Li-ion storage. A high reversible capacity of 493 mA h g −1 is achieved at a rate of 0.1 C. And at a fast charge/discharge rate of 30 C, the GPF electrode delivers a capacity of 220 mA h g −1 , which can last for up to 5000 cycles with nearly no capacity fading. We also demonstrate the GPF as a new type of current collector for active materials with improved mass loading and rate performance. The fabrication is cost effective, highly efficient, and scalable, and thus may pave way to new carbonaceous materials for high-performance energy storage. [ABSTRACT FROM AUTHOR]

A novel flexible and lightweight Fe 2 O 3 -based lithium-ion battery anode has been developed by growing porous α-Fe 2 O 3 nanorods onto carbon nanotubes–graphene foam (CNT–GF). The CNT–GF 3D network provides a highly conductive, high surface areas and lightweight scaffold for the active Fe 2 O 3 nanorods. Such unique electrodes for lithium-ion battery exhibit an 80% initial columbic efficiency, high-rate capabilities, and >1000 mA h/g capacities at 200 mA/g up to 300 cycles without obvious fading. These properties can be attributed to the fast electrochemical reaction kinetics and electron transport rendered by the conductive 3D network. Our structural design protocol can be extended to many other nanostructured metal oxides or sulfides, and thus provides a new strategy for construction of high-performance electrodes for energy storage. [ABSTRACT FROM AUTHOR]

Abstract: While SnO2 is regarded as a good material for Li ion storage because of its high theoretical capacity, its microstructured powder form cannot be directly used as battery electrode because of a drastic pulverization problem and thus poor cyclic performance. Nanostructuring offers opportunities to circumvent this drawback. We report the construction of SnO2 nanoflake branches onto robust TiO2 nanotube stems. This core-branch nanostructured electrode demonstrate evidently improved Li ion storage properties compared to powders, with more stable cycling processes and higher rate capability. In this design, the TiO2 nanotube stems are realized by atomic layer deposition and offer a low-mass scaffold for the SnO2 nanoflakes and also a charge conductive path. [Copyright &y& Elsevier]

Abstract: Considerable irreversible capacity loss of LaNi3.6Co0.7Mn0.4Al0.3 electrode was observed after standing at 100% or 95% depth of discharge (DOD) in open circuit for 2 or 5 days, respectively. The mechanism was systematically studied. Electrochemical impedance spectroscopy (EIS) showed considerably increased charge transfer resistance (R ct) for the electrodes after standing. X-ray diffraction (XRD), open-circuit potential (OCP), scanning electron microscope (SEM), energy disperse X-ray analyzer (EDS) and X-ray photoelectron spectroscopy (XPS) analyses were conducted to investigate the details during standing. The results demonstrated that there were two successive oxidations occurred, which acted as the conjugated reactions for hydrogen evolution reaction (HER), on the alloy surface during the standing process. The first oxidation was attributed to the electrochemical desorption of hydrogen, which was essentially the self-discharge process of electrode and irrelevant to the irreversible capacity decay. The second one corresponded to the oxidation of elemental Ni with flocculent deposits on the alloy surface, which primarily determined the rapid capacity and kinetics deterioration of the alloy electrode. [Copyright &y& Elsevier]

Abstract: In this paper, the microstructures, hydrogen storage and electrochemical properties of LaNi3.8−x Mn x (x =0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) have been studied systematically. The microstructures were identified by X-ray diffraction (XRD) and scanning electronic microscope (SEM). The results showed that all the alloys were mainly composed of two different phases with the same composition, including the hexagonal Pr5Co19-type phase (P63/mmc) and the rhombohedral Ce5Co19-type phase (R-3m), respectively, but minor phases appeared when x ≥0.4. With Mn content increasing, the cell volume increased and the relative abundances of Pr5Co19-type phase and Ce5Co19-type phase were changed, the equilibrium pressure declined gradually and the hydrogen storage capacity increased first and then decreased, and the maximum discharge capacity increased from 209.4mAhg−1 (x =0.0) to 268.8mAhg−1 (x =0.4) and then decreased to 230.3mAhg−1 (x =0.5). Meanwhile, the exchange current density (I 0) and the diffusion coefficient (D) were also improved with the addition of Mn, reaching a maximum at x =0.4. [Copyright &y& Elsevier]

The void introduction for high-energy alloying-type electrode has suffered a dilemma between insufficient void leading to structural collapse and excessive void causing low volumetrical utilization ratio. Herein, a novel tunable void structure of SnO 2 -void-hierarchically vertical graphene (SnO 2 □hVG) nanoarray has been designed via facile C-plasma technique, which facilitates simultaneous encapsulation of protective vertical graphene and moderate void formation. Benefiting from the tunable void and interconnected highly conductive graphene shells and backbones, our all-in-one framework delivers excellent structural integrity and superior Li+ storage capabilities due to the precise volume buffering without collapse of structure and extravagant void. As a result, an imposing capacity of 650 mA h g−1 at 2 A g−1 and negligible capability degradation after 1000 cycles can be achieved. This result opens a new opportunity in tunable void design to enhance the electrochemical performance of alloying-type electrode materials. A facile C-plasma strategy is applied to precisely tune the void space and simultaneously deliver vertical graphene shell without sacrificial agents. ga1 • Carbon plasma serves as a facile and efficient strategy to tune the void volume. • Void space can be controlled to precisely buffer the volumetric change of alloying-type electrode. • No sacrificial agents are introduced for the first time in fabricating tunable void structure. • Hierarchically vertical graphene is simultaneously achieved as a conductive shell. • The binder-free electrode deliver excellent capability and cycling stability. [ABSTRACT FROM AUTHOR]

Ni 3 S 2 nanoarrays directly growing on Ni foam are fabricated via an electrochemical corrosion method and used as freestanding electrode for sodium ion batteries. Based on high electronic conductivity facilitated by the 3D Ni backbone and fast surface redox reactions rendered by the ultrathin thickness of the Ni 3 S 2 nanoarrays, high pseudocapacitive contribution for the charge storage is induced in the Ni 3 S 2 -Ni electrode. Remarkably, the capacitive contribution is self-adaptively enhanced in cycling owing to the gradually reduced and stabilized charge transfer resistance, triggering exceptional electrochemical performance. The Ni 3 S 2 -Ni electrode delivers ultra-stable cycling with charge/discharge capacities of 344.2/350.6 mAh g −1 after 200 cycles at 150 mA g −1 as well as high capacity recovery of 427 mAh g −1 after 70 cycles from 150 to 3000 mA g −1 . Meanwhile, practical application for the Ni 3 S 2 -Ni electrode is also preliminarily assessed. It exhibits promising fast discharge/slow charge (750/150 mA g −1 ) performance with initial discharge/charge capacities of 285.4/275.7 mAh g −1 and 244.8/242.2 mAh g −1 after 300 cycles. When matching with Na 3 V 2 (PO 4 ) 3 cathode, it delivers discharge capacity of 347.8 mAh g −1 after 180 cycles at 200 mA g −1 . [ABSTRACT FROM AUTHOR]

2D Boron is an atomically thin layer of boron with both light weight and metallicity, two kinds of potential structures are proposed, namely, a close-packed triangular B layer(denoted B △ hereafter) and a hexagonal voids or vacancies ( Image 2 ) in B layer(denoted Image 4 hereafter) (Evgeni S. et al. Nano Lett. 2012, 12, 2441–2445). Here, we use first-principles calculations to investigate the potential of borophene as an anode material for sodium-ion batteries. It is found that borophene has an adsorption energy to sodium atoms of −1.448 eV for all boron atoms in the plane ( Image 3 ) and −1.731 eV for B Δ . The fully sodiated phase of borophene is Na 0.083 B and Na 0.1 B for B Δ and Image 3 , respectively, which corresponds to a theoretical specific capacity of 248 mAh g −1 (496 mAh g −1 for two sides) for B Δ and 298 mAh g −1 (596 mAh g −1 for two sides) for Image 3 . The energy barrier along the furrow of corrugated borophene is only 12 meV for B Δ , which suggests that sodium diffusion on borophene can be extremely fast for B Δ . In addition, a strong directional anisotropy is observed for sodium diffusion with a 352.5 meV barrier perpendicular to the furrow of B Δ . Finally, both exhibit metallic characteristics during the entire sodiation process, which indicates that the material has excellent electronic conductivity. The findings in this work suggest that as an anode material for sodium-ion batteries, borophene can drastically boost the energy and power density of batteries. [ABSTRACT FROM AUTHOR]