Synthesis of Silicon Nano-particles for Thin Film Electrodes Preparation
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1245-A09-06
Synthesis of Silicon Nano-particles for Thin Film Electrodes Preparation David Munao1, Jan van Erven1, Mario Valvo1, Vincent Vons1, Alper Evirgen1, Erik Kelder1 1
NanoStructured Materials / Delft ChemE, TUDelft, Julianalaan 136 BL, Delft, Netherlands
ABSTRACT The present work concerns novel approaches to fabricate silicon-based electrodes. In this study silicon nano-particles are synthesized via two aerosol routes: Laser assisted Chemical Vapour Pyrolysis (LaCVP) and Spark Discharge Generation (SDG). These two techniques allow the generation of uniformly sized particles, with a good control over the composition and the range of sizes. Herein, particles with size ranging from 2 to 70 nm were obtained. Starting from these nano-particles, nano-structured porous thin films are produced either by electrospraying a polymeric solution in which LaCVP-produced particles were previously dispersed, or by inertial impacting the SDG-produced particles directly from gas phase onto a substrate. The ElectroSpray (ES) is used to produce composite films for Li-ion battery applications, whereas the Inertial Impaction (II) is used to produce pure silicon films for other purposes (i.e.: sensors). INTRODUCTION During the last decades the interest in Si-based devices has risen significantly due to the large number of applications for this material, especially in its nano-structured form. As new mechanical, optical and electrical properties arise from quantum confinement effects, a whole range of new applications is emerging. These span from optoelectronics to sensors, as well as energy storage and biomedicals [1-3]. The synthesis and the assembly of Si nano-particles are herein carried out via aerosol-based approaches for the production of thin film structures. One of the most promising applications of thin films electrodes is related to energy storage via Li-ion batteries. Silicon-based negative electrodes are considered the best alternative to the commercially used graphite or carbon anodes (i.e. 372 mAhg-1) due to the fact that their theoretical capacity (i.e. 4200 mAhg-1) is roughly ten times higher . However, severe capacity fading still represents a limiting factor for the commercialization of Si-based anodes. The capacity fading is caused by the volume change of the host Si structure upon alloying/de-alloying with lithium. This results in fractures and loss of electrical contact between the various parts of an electrode. In particular, significant fractions of the active material are no longer available for the electrochemical process and the battery rapidly loses its performance. In this work three approaches to increase the mechanical stability of the films are considered: reducing the size of the host particles, nano-structuring the electrode film and using different binders to form a nanocomposite structure. In this way practical shortcomings of silicon are considerably reduced. EXPERIMENTAL DETAILS Silicon nano-particle syntheses Silicon nano-particles were produced via two different aerosol routes: Laser assist
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