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A facile method is developed to improve the initial reversible capacity of hollow carbon nanofibers (HCNFs), which are manufactured via coaxial electrospinning of core/shell precursor nanofibers and their thermal treatments for stabilization and carbonization. Since the low initial reversible capacity of HCNFs is mainly caused by mesopores in the HCNFs, in our approach, the size of these mesopores is reduced by simply introducing a chemical vapor deposition (CVD) process between the stabilization and carbonization processes, thereby inducing the deposition of carbon atoms in the mesopores. The initial coulombic efficiencies of the HCNFs and the Si-encapsulated HCNFs are significantly increased by employing CVD process. The mechanism behind such improvement is revealed by morphological, microstructural, surface, and electrochemical analyses, confirming that control of the mesopores in HCNFs is an effective means to improve the electrochemical performance of HCNFs. [ABSTRACT FROM AUTHOR]

Abstract: This work reports on hollow carbon nanofibers (HCNFs) as anode materials for Li-ion batteries. Various HCNFs are synthesized using co-axial electrospinning of styrene-co-acrylonitrile (core) and poly(acrylonitrile) (shell) solutions and subsequent thermal treatments. The microstructures of HCNFs are examined using SEM, Raman spectroscopy, WAXD, and HR-TEM. The effect of the carbonization temperature on their turbostratic carbon structures and electrochemical properties is systematically investigated. As the carbonization temperature increases, both crystallite thickness and length significantly increases while the initial irreversible capacity decreases. These predictable microstructure and electrochemical performance of HCNFs provide important insight for the design of novel nanostructured anode materials such as Si or Sn encapsulated HCNFs. [Copyright &y& Elsevier]

Although lithium-ion batteries have already had a considerable impact on making our lives smarter, healthier, and cleaner by powering smartphones, wearable devices, and electric vehicles, demands for significant improvement in battery performance have grown with the continuous development of electronic devices. Developing novel anode materials offers one of the most promising routes to meet these demands and to resolve issues present in existing graphite anodes, such as a low theoretical capacity and poor rate capabilities. Significant improvements over current commercial batteries have been identified using the electrospinning process, owing to a simple processing technique and a wide variety of electrospinnable materials. It is important to understand previous work on nanofiber anode materials to establish strategies that encourage the implementation of current technological developments into commercial lithium-ion battery production, and to advance the design of novel nanofiber anode materials that will be used in the next-generation of batteries. This review identifies previous research into electrospun nanofiber anode materials based on the type of electrochemical reactions present and provides insights that can be used to improve conventional lithium-ion battery performances and to pioneer novel manufacturing routes that can successfully produce the next generation of batteries. [ABSTRACT FROM AUTHOR]

High rate and long lifespan were enabled by the layered oxide cathode active material inspired carbon secondary microsphere. [Display omitted] • Monodisperse secondary carbon microsphere was designed. • Diameters of the secondary particles were highly controllable with the composition. • High rate capability was achieved with the primary particles of ca. 100 nm. • Long lifespan over 500 cycles was achieved with high capacity retention of 83.8%. A new anode material that will provide lithium ion (Li-ion) batteries with high energy and power density is urgently needed. In this work, a layered oxide cathode-inspired secondary hard carbon microsphere (CMS) anode material was designed, and exhibited excellent rate performance and long cyclability. Polyacrylonitrile/poly(styrene- co -acrylonitrile) (PAN/SAN) compositions displaying the meatball-like shape of the PAN precursor were carbonized into CMSs having turbostratic microstructures. The CMS carbonized at 1,000 °C (CMS1000) displayed high specific capacity at the highest current density of 1,000 mA g−1, i.e. , 77.6 % of its average charge capacity at 100 mA g−1, and considerable cycling retention after 500 cycles, i.e. , 83.8 % of the specific capacity at cycle 25. Our work demonstrates that the design of new anode materials is a fruitful route to improve commercial Li-ion batteries. [ABSTRACT FROM AUTHOR]