A silica/carbon composite as anode for lithium-ion batteries with a large rate capability: Experiment and theoretical considerations G. Lener a, * , A.A. Garcia-Blanco b , O. Furlong b , M. Nazzarro b , K. Sapag b , D.E. Barraco c , E.P.M. Leiva a, ** a INFIQC-Conicet, Facultad de Ciencias Químicas, Departamento de Química Te orica y Computacional, Universidad Nacional de C ordoba, Argentina b INFAP-Conicet, Facultad de Ciencias Físico-Matem aticas, Universidad Nacional de San Luis, Argentina c IFEG-Conicet, Facultad de Matem atica Astronomía y Física, Universidad Nacional de C ordoba, Argentina article info Article history: Received 22 December 2017 Received in revised form 13 April 2018 Accepted 5 May 2018 Available online 8 May 2018 Keywords: SiO 2 /C Mesoporous structures Silica-carbon composite High rate capability Lithium-ion battery Thermodynamic analysis abstract New generations of materials are necessary to provide practical and economical solutions for electrode fabrication in lithium ion batteries. To this end, in the present work we propose a negative electrode based on a SiO 2 /C interconnected composite able to charge/discharge at high current regimes while maintaining a very good capacity. In order to have a better understanding of the phenomena that occur in the charge/discharge process, we combined experimental techniques (XPS, DRX, EIS, etc.) with theoretical calculations based on DFT to obtain the thermodynamics of the formation of the reaction products as a function of the cell potential. These results were combined with our experiments and results from the literature to demonstrate the different reactions that could occur. The present material provides a superior performance compared with analogous materials from the literature and may thus be an important tool for obtaining practical solutions in both stationary and mobile electrical devices. © 2018 Elsevier Ltd. All rights reserved. 1. Introduction Lithium-ion batteries (LIBs) represent a major advance in the storage of renewable energy because they allow energy to be stored with large efficiency and power, which can be used when required. Currently LIBs batteries are utilized for electronic devices, electric vehicles, and for energy storage from various renewable resources, such as photovoltaics and wind, among others. Moreover, energy may be stored and become available as demand varies. Current research is often focused on obtaining high capacity anodes based on silicon, due to its large theoretical capacity of 3579 mAh g 1 being significantly higher than that of graphite (372 mAh g 1 ), which is usually used in anodes [1]. However, it is well known that silicon undergoes a huge expansion process, which provokes the pulverization and disconnection of the electric contact, with the electrode losing most of its capacity in the first cycles [2]. In fact, anodes based on metallic silicon suffer a 300% expansion, due to alloy formation (Li x Si y) , while graphite dilates only 7% as a consequence of the intercalation mechanism of Li þ into graphite layers [3]. In the former, the negative effect of expansion has been partially resolved by using different strategies, as described in extensive reviews from the literature [2e6]. To prevent particle fracture, some of these strategies include the use of including Si nanoparticles, Si nanowires, nanotubes, Si thin flakes, Si nanopillars, Si nanospheres, nanostructured spheres, combina- tions of nanoparticles and nanowires [2]. In other approaches, Si nanoparticles are coated, encapsulated, or nanodispersed, in hybrid Si/C nanostructures, to avoid direct contact with the electrolyte [6]. Thin films and alloys with different active elements (H, Mg, Ca, Ag, Zn, B, Al, C, Sn) have also been tested as alternatives [2]. A different approach has been that of using SiO and SiO 2 based electrodes. SiO 2 has been used as starting point to get Si based anodes by the reduction of SiO 2 /C pre-synthesized composites using magnesio- thermic reduction [7 ,8]. Nevertheless, the main drawback of these synthesis strategies resides in the high cost of these processes, as both involve at some stage SiO 2 reduction to silicon, which is a highly activated and therefore expensive procedure [9]. The volu- metric expansion of silicon particles is a bigger problem at the in- dustrial scale [10], and in addition, it is necessary to improve the * Corresponding author. ** Corresponding author. E-mail addresses: germanlener@gmail.com (G. Lener), eze_leiva@yahoo.com.ar (E.P.M. Leiva). Contents lists available at ScienceDirect Electrochimica Acta journal homepage: www.elsevier.com/locate/electacta https://doi.org/10.1016/j.electacta.2018.05.050 0013-4686/© 2018 Elsevier Ltd. All rights reserved. Electrochimica Acta 279 (2018) 289e300