Abstract: Lithium-ion batteries (LIBs) have emerged over the past decade as one of the most promising energy storage and delivery devices because of their high energy densities and high energy efficiencies. Among anode materials investigated for LIBs, silicon has great potential because of its high theoretical capacity (3600 mAh g −1 for fully lithiated Li 15 Si 4 ), which is ten times greater than that of the conventional graphite anode (372 mAh g −1 ). Nevertheless, the application of Si anode to LIBs is still challenging because silicon undergoes severe volume changes (ca. 400%) during the electrochemical reactions, which leads to fracture of silicon particles, resulting in electrical contact loss and capacity fading. In order to address the shortcomings of silicon as an anode, a number of nanoscale structural modifications of silicon itself have been proposed, including nanoparticles, nanowires, nanotubes, hollow and porous structure. These approaches have exhibited the idea that stress/strain in such nanostructures can be relaxed without mechanical fracture so that significant plastic deformation and macroscale failure could be avoided. However, the high surface area of nanostructures promotes excessive SEI formation and other parasitic reactions with the electrolyte that consume Li ions and give unstable electrochemical behaviors. Another way to improve the electrochemical performance of silicon anode is to introduce carbonaceous materials as an electric conductive buffer to accommodate the severe volume changes of silicon. Among the carbonaceous materials, nanocarbons such as graphene and carbon nanotube (CNT) have been widely used to improve the silicon anode materials since their superior high electrical conductivity and ductility characteristics were beneficial for accommodating the severe volume changes of silicon in the composites. Although it is revealed that the introduction of nanocarbon can improve electrochemical performances of silicon anodes to a certain degree, however, compositing with silicon alone does not guarantee good electrochemical performance completely. Rather, the better electrochemical performance is observed when the additional carbon is employed as binding material forming a robust electrical contact between the nanocarbon and silicon. In practice, a number of previous studies have focused on the introduction of additional carbon as a function of improving electrical conductivity and blocking direct contact with electrolytes. However, it is doubtful whether the electric conductive pathways are well maintained during the repeated volume change of silicon in the composite. To date, diverse designs of silicon-based anodes have geared towards releasing the lithiation-induced stress but failed to retain reversible capacity and durability in real battery systems. For the effect of carbonaceous materials introduction, robust contact between silicon and carbon is essential, and the contact should be maintained stable during repeated volume change of silicon in order to be widely adopted as a main anode material for LIBs. Herein, we report on rational design and synthesis of Si/CNT microsphere composite with structural reinforcement using triethoxysilane-derived SiO x (denoted as SiO x -reinforced Si/CNT microsphere) as an adhesive anchor to bind the Si NPs to the CNTs and link the neighboring CNTs together. Triethoxysilane is adopted since the silanol group of triethoxysilane reacts with the hydroxyl groups of ACNT and silicon surfaces and forms a covalent bond. Considering the benefits of SiO x , the combination with carbonaceous materials would be effective for simultaneously boosting electrochemical performance and securing dimensional stability of silicon based materials since the in situ generated Li 2 O and/or Li 4 SiO 4 in the lithiation could be act as stable buffer matrix accommodating the large volume change of silicon. Carbon nanotube microsphere provide not only mechanical support but also efficient electrical pathways during the silicon nanoparticles stores lithium ions due to the CNT’s superior mechanical and electrical properties. Consequently, the Si/CNT/SiO x microsphere composite exhibit better cyclability, and negligible changes of electrodes due to buffer matrix for volume changes, provision of a fast ion conduction pathway, and electrically conductive pathway. For example, the Si/CNT/SiO x microsphere electrode exhibited an initial capacity of 1112 mA h g −1 at 0.5 A g −1 and maintained ∼88% retention of its initial capacity after 100 cycles. Moreover, Si/CNT/SiO x microsphere showed negligible volume change at the electrode level since there is an interconnected pore structure to accommodate the large volume expansion. The very stable electrochemical behavior of the Si/CNT/SiO x microsphere could be attributable to the irreversibly formed lithium silicates buffer layer which are not only tolerate the large volume change of the Si but also act as an adhesive anchor enabling maintain the electrical pathways to silicon. This study provides new insights regarding the introducing of nanocarbon into silicon based anode to apply LIB anode materials with high capacity and cycling stability. More details will be discussed at the meeting.

Abstract: Graphene belongs to an emerging class of ultrathin carbon membrane materials with a high specific surface area, chemical stability, and high electrical and thermal conductivities. Owing to these intrinsic physicochemical characteristics, graphene has been extensively investigated for widespread applications in nanodevices, sensors, catalysis, energy storage systems, and biomedicine as an alternative to porous carbon. In particular, graphene has received increasing attention as an electrode material for electrical double-layer capacitors (EDLCs) due to its high specific surface area and high intrinsic electrical conductivity. Recently, there have been tremendous achievements for improving the gravimetric capacitance of graphene. However, due to the 2D nature of the graphene sheet, graphene can easily restack to form lamellar microstructures on the current collector during the electrode fabrication process. The restacking of the graphene sheets may greatly reduce the utilization of the electrode material and limit the electron and mass transport at the interface of electrode, which as a result leads to decreased capacitor performance. Taking these points into consideration, one strategy for preventing the restacking of graphene sheets is to use CNTs as nanospacers, given their high electrical pathways and large surface area. Recently, several approaches have been reported for fabricating graphene/CNT composites. The most popular approach for fabricating graphene/CNT composites is the preparation of an aqueous solution of GO and CNTs with the use of a surfactant such as sodium dodecylbenzenesulfonate (SDBS) to improve the dispersibility of CNTs, followed by vacuum filtration or a hydrothermal process. Another approach is the use of cationic surfactant polymers such as cetyltrimethylammonium bromide (CTAB) and polyethyleneimine (PEI) to induce electrostatic attraction by introducing a surface charge on CNTs or graphene. However, the use of insulating polymers is not desirable, since it is difficult to completely remove the surfactant polymers, and the amorphous carbon formed after heat treatment of the polymer under an inert atmosphere could deteriorate the electrical conductivity. Furthermore, such composites showed a marginal improvement of electrochemical properties. Another points, to further explore the macroscopic applications of graphene, an essential prerequisite is the controlled large-scale assembly of twodimensional (2D) graphene building blocks and the transfer of their inherent properties into three-dimensional (3D) structures with a high packing density. Furthermore, graphene needs to be assembled into a microsized powder form considering the powder morphology of activated carbon, which is currently used as an electrode material for EDLCs. Despite the recent progress in realizing graphene assemblies using well-established strategies such as vacuum filtration, layer-by-layer assembly, Langmuir–Blodgett assembly, hydrothermal assembly followed by oven drying, and spray drying, the controllable and scalable assembly of such graphene into graphene microsized powders with a high packing density remains a significant challenge In this regards, herein, we report the novel integrated Graphene tube @ Graphene Microsphere by using cobalt acetate and dicyandiamide. Graphene tube @Graphene Microspheres (GT@GMs) show a high gravimetric capacitance of 229.8 F g -1 at 0.1 A g -1 in 1 M TEABF 4 /ACN electrolyte. The GT@GMs exhibited excellent rate capabilities of 94.3 % (gravimetric capacitance at a current density of 2 A g -1 compared with gravimetric capacitance at a current density of 0.1 A g -1 ) with time constants in the range of 0.4 to 0.8 s owing to the favorable formation of pathway by formation of graphene tubes; this allowed the electrolyte to easily penetrate the graphene assembly and facilitated ion transport. Furthermore, all the A-GMs exhibited excellent cycling stability (95.1 % of the initial capacitance retained after 100,000 charge/discharge cycles at a current density of 2 A g –1 ) owing to their low oxygen content as well as structural stability originating from the compact assembly of graphene micropores. This study provides new insights regarding the introducing of 1D carbon into graphene to produce graphene-based electrode materials with both high gravimetric capacitances and rate capabilities. Detailed synthetic procedure, electrochemical properties will be discussed at the meeting.

Abstract: Application of Si anodes is hindered by severe capacity fading due to pulverization of Si particles during the large volume changes of Si during charge/discharge and repeated formation of the solid‐electrolyte interphase. To address these issues, considerable efforts have been devoted to the development of Si composites with conductive carbons (Si/C composites). However, Si/C composites with high C content inevitably show low volumetric capacity because of low electrode density. For practical applications, the volumetric capacity of a Si/C composite electrode is more important than gravimetric capacity, but volumetric capacity in pressed electrodes is rarely reported. Herein, a novel synthesis strategy is demonstrate for a compact Si nanoparticle/graphene microspherical assembly with interfacial stability and mechanical strength achieved by consecutively formed chemical bonds using 3‐aminopropyltriethoxysilane and sucrose. The unpressed electrode (density: 0.71 g cm −3 ) shows a reversible specific capacity of 1470 mAh g −1 with a high initial coulombic efficiency of 83.7% at a current density of 1 C‐rate. The corresponding pressed electrode (density: 1.32 g cm −3 ) exhibits high reversible volumetric capacity of 1405 mAh cm −3 and gravimetric capacity of 1520 mAh g −1 with a high initial coulombic efficiency of 80.4% and excellent cycling stability of 83% over 100 cycles at 1 C‐rate.

Abstract: Flexible all‐solid‐state supercapacitors are actively investigated for their potential applications in flexible and wearable electronic devices. The important challenge in this field is to achieve a long‐term cycling stability under repeated bending and high energy. Herein, the design and synthesis of the following are reported: 1) nanofiber cellulose (NFC)‐incorporated nanomesh graphene–carbon nanotube (CNT) hybrid buckypaper electrodes with an excellent flexibility and a high specific capacitance and 2) an ionic liquid‐based solid polymer electrolyte with an excellent mechanical flexibility to realize the aims. Herein, the NFC is used to increase the packing density of the buckypaper through the hydrophobic interaction with CNTs, thereby improving the mechanical flexibility. As for the solid polymer electrolyte, the crosslinked structure is induced to provide the pathways for ion conduction and mechanical integrity even at a high ionic liquid content by chemically attaching triethoxysilane end groups to poly(ethylene oxide)‐poly(propylene oxide)‐poly(ethylene oxide) triblock copolymer. The sandwich structure of 1) and 2) exhibits an excellent cycling stability over 5000 bending cycles and high areal energy density (247 μWh cm −2 ), which are superior to those previously reported in flexible supercapacitors.

Abstract: Herein, we report the in‐situ synthesis of amorphous GeSe/CNT composite via defective‐carbon‐mediated chemical bonding for ultrastable Na‐ion storage. Structural defects in CNTs play a crucial role in the chemical bonding and bonding strength in GeSe/CNTs composites. Specifically, the bonding strength tends to increase with increasing defect concentrations of CNTs. Remarkably, the strong chemical bonding between GeSe and CNTs significantly weakens Ge−Se bonds and promotes amorphization of GeSe, thus facilitating a reversible conversion reaction and enhancing Na‐ion diffusion. Consequently, GeSe/CNTs composite exhibits outstanding cyclability of 87.9% even after 1000 cycles at 1 A g −1 and a high‐rate capability of 288.3 mA h g −1 at 10 A g −1 . Our work presents a promising approach for the amorphization of electrode materials enabled by the defective‐carbon‐mediated strong chemical bonding for Li‐, Na‐, and K‐ion batteries.

Abstract: Graphene is extensively investigated for various energy storage systems. However, the very low density ( 〈 0.01 g cm −3 ) of graphene nanosheets has hindered its further applications. To solve this issue, a controlled assembly of 2D graphene building blocks should be developed into graphene microspheres with high packing density, and restacking of graphene should be prevented to ensure an electrochemically accessible surface area during the assembly. Furthermore, graphene microspheres should have multiple 1D external conductive architecture to promote contacts with the neighbors. This study reports in situ growth of novel graphene nanostructures in reduced graphene oxide microspherical assembly (denoted as GT/GnS@rGB) with restacking resistance and interparticle contacts, for electrochemical energy storage. The GT/GnS@rGB showed high gravimetric (231.8 F g −1 ) and volumetric (181.5 F cm −3 ) capacitances at 0.2 A g −1 in organic electrolyte with excellent rate capabilities of 94.3% (@ 0.2 vs 10 Ag −1 ). Furthermore, GT/GnS@rGB exhibited excellent cycling stability (96.1% of the initial capacitance after 100 000 charge/discharge cycles at 2 A g −1 ). As demonstrated in the electrochemical evaluation as electrode materials for electrical double‐layer capacitors, unique structural and textural features of the GT/GnS@rGB would be beneficial in the use of graphene assembly for energy storage applications.