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Abstract To limit the pulverization of tin-based anode materials during lithiation/delithiation, submicron tin oxide/tin particles are fixed on core/sheath carbon nanofiber/spongy carbon via hydrothermal and carbothermal reduction treatment in this work. During carbothermal reduction, SnO 2 nanosheets are converted to spherical Sn submicron particles and simultaneously the hollow spongy carbon is produced and still enwrap on carbon nanofiber. The as-produced flexible film is used for a binder-free anode for lithium ion batteries, without the polymer binder and conductive carbon. At 0.1, 0.5, 1 and 2 A g−1, the composite electrode respectively displays a discharging capacity of 1393.0, 738.2, 583.6 and 382.6 mAh g−1. Moreover, it delivers specific capacity of 726.9 mAh g−1 and coulombic efficiency of 99.45% after 300 cycles at 0.1 A g−1. The comparison sample of carbon nanofiber/SnO x film without the presence of spongy carbon displays much lower rate performance and worse cyclic performance. The integrated structure of carbon nanofiber/SnO x /spongy carbon results in the remarkable Li-storage performance, in which the carbon nanofiber and spongy carbon synergistically provide conductive channel and buffer zone to hinder the pulverization and peeling of SnO x particles during charging-discharging processes. Graphical abstract Image 1 Highlights • Submicron SnO 2 particles fixed on core/sheath carbon nanofibers/spongy carbon. • CNF/SnO x /SC flexible film used as a binder free anode material. • SnO 2 nanoflakes coated by spongy carbon can be reduced to Sn submicron particles. • Integrated CNF/SnO x /SC provides conductive channel and buffers volume change. [ABSTRACT FROM AUTHOR]

Three dimensional networks, herein carbon coated SnO 2 micron-sized particles are fixed in carbon nanofibers (CNF/SnO 2 @C), is fabricated and synthesized by using hydrothermal method and carbonization. The weight ratio of SnO 2 reaches to 50% of CNF/SnO 2 @C, meanwhile, CNF/SnO 2 @C remains its flexibility. CNF/SnO 2 @C film is directly used as a binder-free anode for lithium ion batteries without conductive additive and polymer binder. The discharge capacities of CNF/SnO 2 @C are 1286 mAh g −1 at 0.05 A g −1 and 397 mAh g −1 at 1 A g −1 , respectively. The buffering effect of CNFs is studied by using ex-situ SEM in the cycled electrodes operated at various lithiation states. The particles size of SnO 2 @C sample increase to 4 μm after 20 charge/discharge cycles, and a serious aggregation of particles occurs in the cycled SnO 2 @C electrode which is in coincidence with its rapidly faded capacity. The particles of CNF/SnO 2 @C sample also present the increased size from the original size of 2 μm to the lithiated size of 4 μm but they are still fixed in CNFs network without any aggregation. The improved specific capacity, cyclic stability and rate performance of CNF/SnO 2 @C are attributed to the structural synergy of CNFs and SnO2 particles, because CNFs as flexible substrate provides excellent conductive channel improving the rate capability and effective network buffering the volume change to promote the cyclic performance. [ABSTRACT FROM AUTHOR]

A series of composites manganese oxide/carbon with one-dimensional structure are synthesized using electrospinning. The phase composition, morphology and electrochemical performance of MnO x /carbon are studied, which affected by the manganese concentration in precursor and subsequent carbonization conditions. The manufacture of MnO x /carbon is composed of two steps including thermal stabilization (at 250 °C in air) and carbonization (at 700 °C in nitrogen). The main functional groups of samples are well identified by FT-IR spectra. The sample Mn33_3h with the lowest manganese content presents the construction structure which amorphous and/or nanosized MnO x with smaller crystal size are grown and enwrapped in carbon fiber during carbonization. Mn33_3h presents the initial charge and discharge capacities of 1054.1 and 665.6 mAh g−1, and the discharge capacity at the 50th cycle remains 99.7% of that at the 2nd cycle. Beside the well rate capability at the range of current densities from 20 to 1000 mA g−1, Mn33_3h presents very good recovery ability after high rate cycling at 1000 mA g−1. The advantages of this composite structure as well as its high capacity make manganese oxide a very attractive candidate as an anode material for the next generation of rechargeable lithium ion batteries. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The α-Fe 2 O 3 grains were grafted onto the TiO 2 /CNFs via the vapor-solid reaction. • The TiO 2 /CNFs reserved void space to suppress the disintegration of the Fe 2 O 3. • The 3D network provide interstitial sites and enhanced pathways for Li+ and e−. Abstract α-Fe 2 O 3 grains grafted onto TiO 2 /carbon nanofibers (CNFs) for use as anode materials in lithium-ion batteries have been successfully fabricated by electrospinning and vapor-solid reaction (VSR). Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N 2 adsorption-desorption isotherms reveal that the ultrafine α-Fe 2 O 3 nanoparticles were formed on the TiO 2 /CNFs and have uniform dispersion along the fiber direction. The VSR approach could retard nucleation, thus making TiO 2 /CNFs with small Fe 2 O 3 grains grafting (approximately 5 nm in diameter). The TiO 2 /CNFs are capable of buffering the large volume variation of α-Fe 2 O 3 during cycling and preventing electrode pulverization and aggregation, as well as providing sufficiently large interstitial space within the crystallographic structure to host Li ions. The electrochemical properties of the composite electrodes were tested by galvanostatic cycling at both constant and variable current rates. The composite delivers both good rate capability under an uprated current density of 1000 mA g−1 and especially enhanced cycle stability (∼600 mA h g−1 after 200 cycles at a current density of 1000 mA g−1). The super electrochemical performance is attributed to a synergetic effect between α-Fe 2 O 3 and TiO 2 -CNFs as well as the three- dimensional (3D) network, which contributes to greatly enhanced diffusion kinetics and structural stability for lithium-ion batteries. This VSR approach can be extended to other hierarchical metal oxide nanostructures for favorable applications in electrochemical devices. [ABSTRACT FROM AUTHOR]

A novel heterostructure of NiO/Ni 3 S 2 nanoflake is synthesized and composited with carbon nanofibers (CNF) membrane. NiO/Ni 3 S 2 nanoflakes are homogeneously dispersed in CNF network, herein, NiO/Ni 3 S 2 like leaf and CNF like branch. Carbon nanofibers network efficiently prevents the pulverization and buffers the volume changes of NiO/Ni 3 S 2 , meanwhile, NiO/Ni 3 S 2 nanoflakes through the conductive channels of carbon nanofibers own improved Li + diffusion ability and structural stability. The capacity of NiO/Ni 3 S 2 /CNF reaches to 519.2 mA g −1 after 200 cycles at the current density of 0.5 A g −1 while NiO/Ni 3 S 2 fades to 71 mAh g −1 after 40 cycles. Owing to the synergetic structure, the resultant binder-free electrode NiO/Ni 3 S 2 /carbon nanofibers shows an excellent reversible lithium storage capability. [ABSTRACT FROM AUTHOR]