The area of nanotechnology is one of the most active fields in science today. It is often seen as the area that could lead to substantial progress in terms of finding new materials with new properties. In this respect, silicon nano-particles are found to be greatly attractive because of their significant technological implications. Considering different areas of research, the energy production, conversion and storage processes are definitely among the most important topics to be studied by science. The reason for that lies in the significant and immediate consequences of their related technology on the current society. Silicon has received a great interest in the energy storage field and is, in fact, considered as one the most promising chemical element for energy storage in modern electrochemical devices due to the fact that it can alloy with lithium. In this respect, energy storage based on lithium chemistry is one of the most advanced electrochemical system in terms of specific power and energy density. Accordingly, Li-ion batteries could be significantly improved in terms of volumetric and gravimetric energy density by using silicon as a negative electrode material. The aim of the present thesis is to find a complete pathway for the silicon nano-particles, from their synthesis to their final designed application: a negative electrode for Li-ion batteries. Since no conventional methods to produce silicon nano-particles have been already established, several synthesis routes have been explored: Electrochemical Etching, Spark Discharge Generation and Laser assisted Chemical Vapor Pyrolisys, respectively. In Chapter 2, the anodic dissolution of a p-type silicon wafer in a HF solution is discussed. Despite the fact that the reaction mechanism is rather complicated and involves many different physical parameters, electrochemical etching offers a simple way to produce porous silicon layers, which can be detached and fragmented into small nano-particles by means of sonication. A basic electrochemical cell is developed for this purpose, and the anodic dissolution of a p?doped silicon wafer was performed in a concentrated HF solution. A linear relation between the electrode mass loss and the current density used during the electrochemical etching confirms the reaction mechanism, where two electrons per atom of silicon etched are involved. More- over, with the current experimental conditions, a current density threshold is found. Below this current threshold, which corresponds to 20 mA/cm2, porous silicon is no longer formed. Although the nano-particles production rate provided by the electrochemical etching is definitely not sufficient for batteries application, the morphological and optical properties of both the surface substrate and the nano-particles are considered very interesting for the application in optoelectronic devices. Strong ultra-violet luminescence is observed at room temperature for the resulting nano-particles suspended in ethanol. The position of the photoluminescence peak is found to be independent from the excitation wavelength, as it is determined by the interaction between the surface states and the selected solvent. Its position is evaluated by means of the quantum confinement effect, which is responsible for the energy gap widening between valence and conduction band. From the quantum confinement theory, the estimated size of the nano-particles is approximately 1.2 nm. In Chapter 3 Spark discharge generation (SDG) of silicon nano-particles is discussed. The production rate of silicon nano-particles from intrinsic silicon electrodes by spark discharge is orders of magnitude smaller compared to metals, since less energy goes into a larger area at a lower rate. Replacing intrinsic silicon by boron-doped rods results in a considerable increase in the production rate, namely two orders of magnitude. Generally speaking, it can be concluded that particles can be generated from any semiconductor using spark discharge, as long as the resistance is kept sufficiently low by either n- or p-doping, heating the electrodes, or changing their shape to reduce the current path-length. Transmission electron micrographs revealed a rather narrow size distribution, comparable to SDG-prepared metal particles. By taking stringent measures to reduce the ingress of oxygen and water into the setup, the production of virtually pure, unoxidized silicon particles with a primary particle size of 3-5 nm is possible using doped silicon rods. Here the initial formed particles are used to getter oxygen from any source, before the actual production. A clear correlation between the color of the particles and the degree of oxidation is observed. This continuous technique can be combined with other steps, e.g. surface functionalization or the immediate impaction of freshly prepared nano-particles onto a substrate for several different applications. Whether or not spark discharge generation is suitable for the production of silicon particles depends on the particular application. In the case of battery and hydrogen storage applications, the high elemental Si content of 95-100 % implies more active material, which positively influences the energy content of both batteries and hydrogen storage materials. Since oxides inevitably act as diffusion barriers, their reduction or total elimination also results in higher reaction rates. With careful working and relatively simple measures, the purity can likely be further increased. Moreover, the size of the spark discharge produced nano-particles is also responsible for rapid reaction rates in the above-mentioned applications. Compared to liquid phase methods the production rate is however currently very low; the laboratory scale production rate is only of the order of 0.1 mg/hr. Significant increases in the production rate are thus needed, since battery or hydrogen storage related applications require rather sizable quantities of materials. For this reason, future work will be focused on upscaling the production rate of spark discharge generation. This can be achieved by increasing the energy input per spark, the number of sparks per second and the number of spark gaps. The current production rate is well suitable for sensor applications though, where even the currently still limited laboratory scale production rate can provide sufficient material. The possibility of continuous operation, direct functionalization and application of the particles through impaction, makes spark discharge especially suited for sensor applications. The simplicity of the spark discharge setup is a real advantage, as there is for instance less need for safety measures related to the use of lasers and hazardous gases such as silane. Although of less importance for sensor applications, both laser ablation and laser pyrolysis also lack the good and simple possibilities for mixing as the use of different electrodes in a single spark gap offers. In Chapter 4 the mass production of silicon nano-particles via an im- proved and upscaled Laser assisted Chemical Vapor Pyrolisys reactor is presented. Silicon nano-particles are synthesized from a SiH4 precursor in a N2 atmosphere. The improvement of the setup consists in the design of a new reaction zone, which leads to a homogenous product in terms of size and composition. For these purposes the reaction zone has been studied in relation to the nozzle and the laser beam geometry. In particular, in order to have mono-dispersed nano-particles, it is important to match the laser beam in- tensity profile with the the gas velocity profile. In this way different gas elements have the same probability to absorb the same amount of energy, resulting in a uniform heating along the reaction zone and therefore in a mono-dispersed product. The concept results in a newly built reaction zone, consisting of a rectangular nozzle and a quasi-rectangular laser beam. The reaction zone is built into a new, flexible to use, reactor that is capable to produce highly pure nano-particles with production rates between 1 and 100 g/h. Its flexibility relies not only in the different types of material that can be produced, but also in the modular configuration of the reactor body towards the assembly pieces (i.e.: nozzles, hoods, probes). The new LaCVP set-up consists of a main core, the reaction chamber, extended with the following auxiliary units: gas supply system, CO2 laser and optics, filtration section, pump and exhaust system, safety control unit (PLC). The effect of the laser power on the powder characteristics is analyzed and five different samples are chosen for a more extensive characterization. The products have been characterized via TEM, XRD, TGA and FTIR analyses and compared to a commercially available one (Aldrich). The synthesized products show a narrow size distribution and a small particle size compared to the commercial material. Both the particle size and the particle size distribution are found to be strictly dependent on the laser power used in the synthesis experiments. Silicon nano-particles are pure and chemically stable upon air exposure, due to a thin passivation layer on the particle surface. These three synthesis techniques have been investigated in order to select the most suitable one with respect to the final designated application of the nano-particles. The most promising technique, in terms of purity of the product, size and size distribution of the particles as well as its great capabilities in terms of production rate, it is found to be the LaCVP. Mass production via LaCVP of small silicon nano-particles allows for thin film composite preparation, their characterization and their application in high energy storage devices. Chapter 5 is the bridge between the synthesis step and the final application of the product. For most electronic and electrochemical applications, in fact, silicon nano-particles have to be incorporated in a real electrode assembly. In this chapter, two novel methods for electrode coating are proposed: the Inertial Impaction and the Electro-spray processes. They both rely on aerosol technology and they constitute elegant approaches for printing/coating processes. The resulting structures are characterized in terms of morphology, highlighting promising features for different kinds of applications, ranging from sensors to electrochemical energy storage. Inertial impaction is used in combination with spark discharge generated particles. Particles are accelerated in the ultra-sonic regime through a static nozzle. The acceleration is the result of a large pressure drop set by means of a critical orifice. Inertia is responsible for subsequent collisional events between particle-substrate and particle-particle, which lead to the formation of a highly porous structure. For the experimental parameters used in this study, the typical morphology of the produced layers exhibits a volcano-like shape where a central, compact crater is surrounded by a so-called rim. This area is shown to be highly porous with an internal structure constituted by vertically oriented fibrous agglomerates. Unfortunately, preliminary results on the electronic conductivity of the layers where not reproducible. This fact is attributed to the high sensitivity of the spark discharge generated particles towards oxygen and to the eventual leaks in the setup used for the electrical measurements. Nevertheless, this approach is still suitable to be applied in several areas of interests. Sensor devices could be fabricated, provided that the surface of the silicon particles is passivated with a stable functionalization that could interact with chemical species in a specific and reversible manner. Moreover, by reducing the impaction time and thereby the thickness of the electrodes, it can be envisioned that the resulting thin layers could be implemented for the fabrication of solid-state micro batteries. In this way, the intrinsic shortcoming of having a low particle production rate would be balanced by the limited amount of material needed for the specific application, and the absence of any liquid contaminant could enable for a high purity of the active material involved in the process. Alternatively, Electro-spray is presented as a novel method to standard coating techniques (e.g. doctor blading). It is used to perform direct de- position of mixtures of active/inactive material, dispersed on nano-metric scales. As-produced layers show a constant thickness throughout all the sprayed surfaces, a very good adhesion with the current collector and a high surface area. The thickness of the layer can be controlled according to the deposition time and varies typically between 10 and 20 ?m. High surface to volume ratio is the result of the layer nano-structure, which is achieved by a stable multi-cone jet deposition. Solid aggregates are formed by constitutive spherical units, which size lies in the hundred of nanometer range for the Si-CMC sample. The deposition process takes place at low temperatures, in ambient conditions and, upon the right choice of the polymeric binder, with the use of non-toxic chemicals or solvents. In addition to that, the concrete possibility of upscaling the process with multi-nozzle system and roll-to-roll substrates makes this technique appealing from an industrial point of view, where large scale application demand could be taken into consideration. In this respect, the fabricated Si based nano-composite electrodes, are considered as a promising solution to increase the energy density of lithium ion batteries and they could open new possibilities for the sustainable mobility concept. Chapter 6 describes the electrochemical behavior of the silicon nano- composite electrodes in a half cell configuration (i.e. Si vs. Li). The first part of the chapter is dedicated to the explanation of the failure mechanisms of the silicon-based electrodes, while the second part offers viable solution to the capacity fading issue and the short lifetime of such electrodes. In this respect, a major role is played by the choice of an appropriate polymeric binder, which can accommodate the large volume expansion occurring dur- ing the electrochemical alloying of lithium. The capacity fading mechanism is further investigated and a simple mechanical model is suggested, which is supported by one of the two CMC binding mechanisms already proposed in the literature. Hydrogen-bond formation between the CMC and the surface of the nano-particles and the dynamic nature of this weak interaction are responsible for the self-healing process that occurs at the sub-micron scale, where the electrical contact does not appear to be lost. As no specific interaction between PVdF and the surface of the Si nano-particle is expected, the capacity of such nano- composite electrodes tends to fade much more rapidly. Furthermore, im- proving the electrodes characteristics in terms of composition and layer thickness resulted in interesting performances at C/20, as well as good rate capabilities. Despite the reduced capacity at much higher C-rates, the sys- tem recovers its capacity almost completely when coming back to C/20, hence, indicating that the capacity loss is not due to parasitic reactions. In particular, a preliminary surface treatment significantly reduced the initial irreversible capacity loss and increased the lifetime and the cycleability of the electrodes. Overall, only small morphological changes upon cycling with no electrode fracturing have been observed, thus indicating the validity of the approach here reported for the preparation of an innovative anode material for advanced lithium ion batteries. Concluding with an important remark, it is wort noting that the main goal of this thesis, the synthesis and application of a silicon-based nano-structure in an energy storage device, has been successfully achieved.