Electrochimica Acta 107 (2013) 85–92 Contents lists available at ScienceDirect Electrochimica Acta jo u r n al hom ep age: www.elsevier.com/locate/electacta High-performance Sn@carbon nanocomposite anode for lithium-ion batteries: Lithium storage processes characterization and low-temperature behavior F. Nobili a,∗ , I. Meschini b , M. Mancini a , R. Tossici a , R. Marassi a , F. Croce b,∗∗ a Scuola di Scienze e Tecnologie, Sezione Chimica, Università di Camerino, Via S. Agostino 1, I-62032 Camerino, Italy b Dipartimento di Farmacia, Università “G. D’Annunzio” Chieti-Pescara, Via dei Vestini 31, I-66100 Chieti, Italy a r t i c l e i n f o Article history: Received 4 May 2013 Received in revised form 27 May 2013 Accepted 30 May 2013 Available online 18 June 2013 Keywords: Li-ion battery Sn–C anode material Nanocomposite electrode Electrospinning a b s t r a c t The electrochemical behavior of a composite anode for Li-ion batteries, based on nanosize tin particles embedded in electrically conducting porous multichannel carbon microtubes (Sn–PMCMT), synthesized by co-electrospinning, is here evaluated. An activation protocol aimed at maximizing anode mechanical stability and capacity retention upon cycling is presented. The results are compared with those obtained with an anode using pristine PMCMT carbon as active material. The Li uptake and release processes by Sn and C are evaluated by galvanostatic charge/discharge cycles, in order to differentiate the two contributions to the overall anode capacity. Electrochemical impedance spectroscopy (EIS) analysis is utilized in order to evaluate possible improvements to charge- transfer kinetics due to the nanosize Sn particles dispersion. Finally, the performances of the composite Sn–PMCMT anode are characterized at different charge/discharge currents and temperatures. The anode can deliver a capacity of 500 mAh g -1 for more than 300 cycles, most of them at 1C or higher charge/discharge rate, which confirms its very high, stable cycling performances. Moreover, this tailored nanostructured anode retains a relevant amount of capacity even in very demanding cycling conditions, as the case for very low temperatures. These results make the proposed Sn–PMCMT an ideal candidate anode for high-performance Li-ion batteries able to operate in a wide array of operating conditions. © 2013 Elsevier Ltd. All rights reserved. 1. Introduction Nowadays, modern society is facing challenging energy and environment issues, which, undoubtedly, will require the sub- stitution of fossil fuels with greener energy sources for electric energy generation and ground transportation. Renewable energy sources are the most suited option to this purpose, provided effi- cient devices for electric energy storage and delivery are developed. At the moment, due to their versatility and scalability, lithium-ion batteries represent the best powering opportunity both for portable electronics and for transportation. In fact, the alternative fuel cell based technology, at the moment, is not sufficiently mature as power source for electric vehicles, mainly due to operational factors related to electro-catalysis and to gas feeding and storage [1]. ∗ Corresponding author. Tel.: +39 0737 402210; fax: +39 0737 402296. ∗∗ Corresponding author. Tel.: +39 0871 3554480; fax: +39 0871 355 4483. E-mail addresses: francesco.nobili@unicam.it (F. Nobili), fausto.croce@unich.it (F. Croce). In order to satisfy the high power and energy densities require- ments mandatory for ground transportation applications, new chemistries other than ‘conventional’ anode and cathode materials, currently based on graphite and lithium oxides, are necessary [2,3]. In this context, great expectations are posed on high-capacity anode materials that rely on alloying reactions. Tin is the element that has attracted great attention, as it can be reversibly lithiated up to the end compound Li 4.4 Sn with a theoretical reversible capacity of 994 mAh g -1 . Despite its very high capacity, the practical use of Sn anodes has been hindered by the dramatic large volume expansion of the unit cell – which reaches 300% of its initial value – associ- ated with the reversible lithium alloying and de-alloying during the battery operation. As a consequence, the active material particles are subject to a severe mechanical stress that is the main cause of electrode failure upon cycling. Another drawback often associ- ated with alloying anodes is the high irreversible capacity exhibited during the initial cell cyclations caused by lithium-sequestration irreversible processes such as SEI formation on tin and carbon par- ticles [4–9], being these latter always present in the composite electrode formulation in order to guarantee a sufficient electronic conductivity above the electron percolation threshold [10]. To such 0013-4686/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.electacta.2013.05.150