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Abstract Formation cycle is a significant step in battery processing, as it leads to the build-up of stable solid electrolyte interphase layer that affects various parameters of batteries. Although fast formation cycle is more economical way to realize the battery production, it is generally known that fast formation cycle of conventional electrode materials leads to capacity degradation. In this study, we report the high-rate formation cycle step to induce excellent electrochemical performance, in the case of Co 3 O 4 nanoparticle. Surprisingly, Co 3 O 4 nanoparticle that runs in the formation cycle at rather high current density (1.0 A g−1) exhibits superior electrochemical performance compared with Co 3 O 4 nanoparticle that runs in the formation cycle at 0.05 A g−1. Such enhanced electrochemical performance after the high-rate formation cycle for Co 3 O 4 can be mainly attributed to the stabilization of solid electrolyte interphase layer upon cycling and initial partial agglomeration that forms secondary particles. This work firstly paves the possibility of employing high-rate formation cycle to induce improved electrochemical performance, which can also be extended to various alternative electrode materials. Graphical abstract Image 1 Highlights • Detailed in-depth study on the effect of high-rate formation cycle. • The effect of formation cycle was investigated for Co 3 O 4. • High-rate formation cycle leads to enhanced electrochemical performance. • Both interfacial and morphological transitions depend on formation cycle. [ABSTRACT FROM AUTHOR]

Abstract Increasing the specific capacity and cycle life of graphitic carbon anodes is crucial for realizing high-performance lithium ion batteries. Herein, we introduce a new class of graphitic carbon anodes comprising highly ordered three-dimensional nanostructures decorated with SnO 2 nanoparticles. The inch-scale, nanostructured graphitic carbon matrices are prepared by supported pyrolysis of epoxy templates patterned by advanced optical lithography. During the subsequent decoration process, the SnO 2 nanoparticles are densely formed on the matrix without agglomeration since the periodic nanostructured matrix provides a homogeneous site for nucleation and growth. The surface coverage of the decorated SnO 2 nanoparticles and the mass relative to the graphitic carbon are >80% and ∼50 wt%, respectively. The resulting nanostructured C/SnO 2 composite monoliths can be assembled solely into LIB coin cells without the aid of binders and conducting agents. The achieved specific capacity and retention are 692 mAh g−1 and 87.31% (at 70th cycle), respectively, which is superior to those of nanostructured carbon anodes prepared in a similar way. [ABSTRACT FROM AUTHOR]

In the recent times, pseudocapacitive electrode materials have received great attention due to their considerable capability in storing ions at relatively fast charging rates. Among various candidates, niobium (V) pentoxide (Nb 2 O 5 ) has gained much attraction for lithium-ion batteries (LIBs) due to its insertion/extraction reaction with Li, safe redox potential, and considerably good capacity (about 200 mAhg −1 ). Nevertheless, low conductivity of Nb 2 O 5 has so far prevented its use as a viable electrode material for LIBs. In this study, we have successfully coated silver (Ag) nanoparticles (NPs) on the surface of one-dimensional orthorhombic Nb 2 O 5 fiber (1D T-Nb 2 O 5 ) using simple electrospinning processing. Ag NPs coated Nb 2 O 5 fibers (Ag-1D T-Nb 2 O 5 ) provided faster electron pathways, resulting in much improved capacity at a given current density with superior rate capabilities compared with pristine 1D T-Nb 2 O 5 . In addition, 1D T-Nb 2 O 5 was more suitable for coating Ag NPs compared with T-Nb 2 O 5 NPs, where its structural integrity was maintained even after cycling. As a result, effective coating of conductive Ag NPs on the 1D T-Nb 2 O 5 resulted in excellent cycle retention characteristics (179.7 mAhg −1 after 500 cycles at 500 mA g −1 ) as well as superior rate capabilities (103.6 mAhg −1 at a current density of 5000 mA g −1 ). [ABSTRACT FROM AUTHOR]

Structural and electronic modification of titanium oxide (TiO 2 ) nanomaterials induced by the co-introduction of fully disordered glass phase and oxygen vacancies can lead to remarkable advances in the electrode performance in emerging energy storage systems. We report on the effective co-creation of fully amorphous nanofibers (NFs) composed of black TiO 2-x and conductive carbons throughout the NF structure, and evaluate the materials as potential anodes in sodium-ion batteries. The black TiO 2-x nanofiber is successfully fabricated by electrospinning a precursor solution followed by a two-step sequential thermal treatment in an air and reducing atmosphere. The NF electrode could deliver approximately two-fold higher 2nd discharge capacity and an excellent kinetic performance even under high rates compared to that delivered by anatase-structured white TiO 2 NFs used as reference, because of (i) an inherent free volume in the glass phase corresponding to the enlarged Na + sites, (ii) increased electrical conductivity (low bandgap) resulting from the presence of Ti 3+ , (iii) introduction of conductive carbon agents around the TiO 2-x domain, and (iv) one-dimensional NF feature allowing numerous Na + reaction sites at the electrochemical interface. We also elucidate the morphological and structural changes in the nanofibers after discharge and charge by ex-situ characterizations. [ABSTRACT FROM AUTHOR]

Careful modulation of surficial and interfacial properties of electrode materials is a critical factor for determining overall electrochemical characteristics. Recent studies have indicated that metal oxide nanocoating layer (such as titanium (IV) oxide (TiO 2 )) on metal oxide anodes (such as tin (IV) oxide (SnO 2 )) exhibited superior electrochemical properties, but fundamental research on the effect and role of TiO 2 layer thickness has been limited. Here we have successfully conducted in-depth study on how the thickness of TiO 2 overlayer on SnO 2 can have significant influence in the overall parameters of electrochemistry. It is revealed that TiO 2 overlayer with 12 nm shows good cycle retention (75.8%) even after 80 cycles and retains capacity of 438.3 mAh g −1 even at high current density (5000 mA g −1 ). Surprisingly, it was further discovered that TiO 2 layer not only alleviates the volume expansion but also helps to facilitate Li ion transport compared with SnO 2 . The improvements in both ionic and electrical conductivity of TiO 2 layer are main factors in better cycle retention and rate capabilities. Finally, in situ transmission electron microscopy analysis was adopted to observe the growth dynamics of solid electrolyte interphase layer on TiO 2 @SnO 2 , which demonstrates that TiO 2 overlayer results in homogeneous and thinner interphase layer compared with SnO 2 NTs. [ABSTRACT FROM AUTHOR]

• Synthesis of CA-CNF by insulating block electrospinning & carbonization. • Formation of cross-aligned network even after heat treatment. • Faster reaction kinetics and regular electron pathway of CA-CNF. • High-rate cyclability of CA-CNF (259.4 mAh g−1 at 3000 mA g−1). The conventional use of metallic current collector in an electrochemical cell results in decreased loading of active materials and hence limited capacity in consideration of all the inactive current collector components. In response to this trend, a number of conductive, free-standing materials have been proposed as electrodes, which would act as both current collector and active materials. Here, in this study, we have firstly developed the cross-aligned carbon nanofiber (CA-CNF) for efficient Li storage, especially at high current densities. Using the insulating block electrospinning, the nanofibers can be aligned in a certain direction, where it is viable to fabricate cross-aligned nanofibers in a cost-effective and scalable manner. Attributed to faster kinetics and regular electron pathway arising from CA-CNF, it exhibits an excellent high-rate cyclability (259.4 mAh g−1 at a current density of 3000 mA g−1). This work builds up a milestone in suggesting a cross-aligned carbon nanofibrous network as efficient Li storage, which can also be applied to various electrode materials embedded cross-aligned conductive composite materials. [Display omitted] [ABSTRACT FROM AUTHOR]

• Novel top-down synthesis of CNS from aronia fruit powder by carbonization. • Temperature-independent synthesis of CNS. • Gas atmosphere-independent synthesis of CNS. • CNS exhibits high-rate cyclability for Li+ and K+ ion storage. • Structural integrity was well maintained even after cycling for Li+ and K+. Carbon nanosheets (CNSs) have been used in various applications, ranging from energy storage to drug delivery. CNSs are conventionally synthesized by chemical vapor deposition, but their high cost and non-scalability prompted the development of alternative synthesis routes. More scalable methods such as the sol-gel process still suffer from its complicated synthetic steps with delicate conditions. Here, we demonstrate for the first time a unique top-down synthesis of CNSs from aronia fruit powder, which is simple, scalable, and cost-effective. Aronia-derived CNS can be fabricated at various heating temperatures (500, 700, and 900 °C) and under different atmospheres (N 2 /H 2 and NH 3), which can easily tune the overall physicochemical properties of the CNS. We evaluated the electrochemical performance of the CNS for potential applications in Li- and K-ion batteries, in which the CNS showed stable electrochemical performance even at a high current density (1000 mA g−1). Because of the high-throughput nature of this synthetic approach, the aronia-derived CNSs could be very useful in developing novel applications at an industrial scale. [Display omitted] [ABSTRACT FROM AUTHOR]

• Synthesis of MFC from low-grade gum wastes. • The synthesized MFC possesses high tap density (1.4–1.7 g cm−3). • High tap density leads to outstanding volumetric capacity at 3.0 A g−1. • MFC also exhibits ultra-stable high-rate cyclability (0.001881% decrease per cycle). • Structural integrity was well maintained even after cycling. Among various natural wastes, gum wastes pose major issues, as they are unusable and hard to be disposed due to their acidic and sticky nature. Herein, a rational synthetic strategy is employed to transform various kinds of gum wastes into micron-sized carbon, which also exhibit high tap density (1.4–1.7 g cm−3) desirable for practical application in lithium-ion batteries (LIBs). Gum karaya (GK) micron-size functional carbon (GKMFC) exhibits the most outstanding electrochemical performance, with a volumetric capacity of 175.4 mAh cm−3 at a current density of 3000 mA g−1 for 5000 cycles, and possesses ultra-stable high-rate cyclability (a capacity decay of only 0.001881% per cycle). Additional electrochemical analyses reveal that GKMFC exhibits stable structural integrity as well as minimal cell resistance even after cycling, showing its practical application as viable electrode for LIBs. This work sheds light on utilizing high tap density carbon from gum wastes for LIBs, which can also be applicable to other natural wastes and carbon. Image, graphical abstract [ABSTRACT FROM AUTHOR]