Analysis of porosity on the discharge of silicon-air batteries
S.B. Gani (TU Delft - Electrical Engineering, Mathematics and Computer Science)
Rene Van van Swaaij – Mentor (TU Delft - Photovoltaic Materials and Devices)
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Abstract
Energy storage is a critical component in decreasing the unpredictability of
renewable energy. Silicon-air battery is a type of storage technology that potentially has a higher energy density than lithium-ion battery. The silicon-air
battery, on the other hand, must overcome corrosion and passivation reactions in order to discharge continuously. One method of reducing the passivation reaction is by increasing the dissolution rate of the discharged product higher than its generation rate. This is possible by increasing the surface area of silicon anode by making it porous. The objective of this research is to evaluate the effect of porosity on the discharge of a silicon-air battery. In this work amorphous silicon (a-Si:H) based anodes made by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique are used. The deposition power and deposition pressure are altered to obtain a-Si:H anodes of different porosities. The influence of these deposition conditions on porosity and conductivity is studied. In order to find the porosity, the refractive index of the deposited a-Si:H layer was obtained from optical characterization. Bruggeman’s Effective Medium approach is followed to calculate porosity. The deposition power has the greatest impact on the refractive index, porosity, and conductivity of the a-Si:H layer. Increasing the deposition power raises the porosity and the conductivity. This thesis also looks into the effect of varying the fraction of dopant gas in the gas mixture on porosity and
conductivity. The experiments show that both porosity and conductivity increase with higher fraction of dopant gas. The deposited a-Si:H layer and c-Si wafer were used as anode in the discharge of silicon-air battery.