Porous silicon oxide electrodes promote sustainable energy storage solutions
Lithium-ion batteries (LIBs) are indispensable in modern devices, from smartphones to electric vehicles and sustainable energy systems. Yet challenges such as limited durability and the use of toxic liquid electrolytes necessitate advances in battery technology. To address these issues, researchers have been exploring all-solid-state batteries as a potential alternative for more than a decade.
Despite their promise, silicon-based, all-solid-state batteries have faced significant hurdles. The repeated expansion and contraction of the silicon electrode during charge/discharge cycles generates mechanical stress, causing the electrode to crack and separate from the solid electrolyte, leading to a decrease in performance.
A research team led by Professor Takayuki Doi of Doshisha University has proposed a possible solution. Their recent research, published in *ACS Applied Materials and Interfaces* on October 29, 2024, investigates the introduction of pores into silicon oxide (SiOx) electrodes to reduce these mechanical stresses. In collaboration with Dr. Kohei Marumoto from Doshisha University and Dr. Kiyotaka Nakano of Hitachi High-Tech Corporation, the team examined the performance of porous SiOx electrodes in all-solid-state cells.
The team fabricated the electrodes using radiofrequency sputtering, using Li-La-Zr-Ta-O (LLZTO) as a solid electrolyte. Advanced scanning electron microscopy revealed that porous SiOx electrodes outperformed their non-porous counterparts during repeated charge/discharge cycles.
“Non-porous SiOx partially exfoliated from the LLZTO electrolyte during the 20th cycle, which was consistent with the drastic decrease in capacitance and increase in internal resistance that we observed,” says Dr. Bye. “Although the initially observed pore structure of porous SiOx collapsed due to repeated expansion and contraction, the remaining pores, in contrast, still served as a buffer against the internal and interfacial tensions. This ultimately helped maintain the interfacial connection between the electrode and the electrolyte.”
An important achievement of the research is the possibility of manufacturing thicker SiOx electrodes. While conventional silicon electrodes require a thickness of less than one micrometer to avoid cracking, porous SiOx electrodes achieved stable performance at 5 µm. This improvement results in an energy density 17 times higher than traditional non-porous silicon electrodes, significantly improving space efficiency by enabling greater energy storage per unit volume.
The study highlights the broader implications of this innovation. Porous silicon oxide electrodes could pave the way for more efficient and safer all-solid-state batteries, benefiting applications ranging from electric vehicles to large-scale energy storage. “We expect that the results of our research will make a multifaceted contribution to sustainable development goals, not only in terms of climate change countermeasures based on the reduction of CO2 emissions, but also in terms of economic growth and urban development,” adds Dr. Bye bye. .
The findings also highlight areas for further research, particularly in optimizing the porous structures of SiOx electrodes to achieve peak performance. This progress represents an important step towards a sustainable future powered by advanced energy storage technologies.
Research report:Tailor-made design of a nanoporous structure suitable for thick Si electrodes on a rigid oxide-based solid electrolyte
