Licentiate Seminar in Engineering Physics with Ali Abo Hamad
Welcome to the licentiate seminar with Ali Abo Hamad. He will present his thesis "Green thermochemical modification of silicon microparticles for next-generation lithium-ion battery anodes".
Licentiate thesis: Green thermochemical modification of silicon microparticles for next-generation lithium-ion battery anodes
Date: 28 November at 09.00
Room: C312 Mid Sweden University, campus Sundsvall
Supervisor: Associate Professor Jonas Örtegren, Mid Sweden University
Assistant supervisor: Researcher Manisha Phadatare, Mid Sweden University
Opponent: Associate Professor Fredrik Björefors, Uppsala University
Abstract
Silicon (Si) is a promising anode material for the next generation of lithium-ion batteries (LIBs) due to its very high theoretical capacity. However, its practical use is limited by sharp changes in volume during cycling, leading to cracking, unstable interfaces and rapid loss of capacity. In addition, many methods for producing porous silicon rely on hydrogen fluoride acid (HF), which poses environmental and safety concerns.
In this thesis, a green and scalable thermochemical method for producing porous silicon microparticles using urea-based etching is presented. The process combines chemical reactivity and mechanical stress from urease phase transitions at elevated temperature, producing mesoporous structures while preserving crystallinity. Under favorable conditions, surfaces of up to ~27 m2 g-1 were achieved, and analyses showed stabilizing Si–O, and Si–N bonds at the surface. Porous silicon was incorporated into graphite composites for electrochemical tests. Electrodes with 10-20% silicon by weight showed stable capacities of 630-880 mAh g-1 after 100 cycles at 0.1C, with coulombic efficiencies above 98%. This is more than twice as much as untreated silicon and almost three times as much as pure graphite. Higher silicon levels, on the other hand, led to reduced stability. In speed tests, 65-74% of capacity was retained at 2C, which shows good power, and cycling performance.
The work shows that urea-based porosification is a sustainable method for producing functional silicon anodes. Future studies will focus on optimizing porous silicon as a stand-alone active material as well as conducting post-mortem analyses to understand degradation mechanisms and the importance of porosity.