Researchers discovered a technique for imaging silicon anode degradation, which may lead to better performing batteries.
Lithium-ion battery technology has gained a lot of research attention. The behavior and performance of lithium-ion batteries depend heavily on electrodes. Many research studies have focused on the interface of the electrodes, and electrolytes. Due to repetitive electrochemical reactions, a solid-electrolyte interphase usually forms between the electrodes and the liquid electrolyte. This formation is vital for the electrochemical reaction in batteries and it governs the battery stability.
Researchers from the Pennsylvania State University suggest that using silicon for high-capacity batteries can help resolve the stability and overall performance of the batteries.
“In the last 10 years, silicon has attracted a lot of attention as a high-capacity negative electrode for rechargeable batteries,” said Sulin Zhang, professor of engineering science and mechanics and of bioengineering. “Current commercialized batteries use graphite as an anode material, but the capacity of silicon is about 10 times that of graphite. There are tens of millions, hundreds of millions even, of dollars invested in silicon battery research because of this.”
However, there are issues associated with silicon electrodes. During the charging and discharging cycles, the volume of silicon expands and shrinks, which leads to the silicon material cracking, and the SEI will crumble and regenerate over and over. This is a serious issue as it leads to loss of electrical contact and degradation of capacity, the amount of charge stored by the battery.
“Because the stability of this layer controls the stability of the battery, you don’t want this growing uncontrollably because the creation of this layer will consume electrolyte material as well as active lithium,” Zhang said. “And this may lead to the drying up of electrolytes and loss of active materials, so you have an adverse effect on battery performance.”
The researchers used cryogenic scanning transmission electron microscopy (cryo-STEM), and were able to get a 3D view of the SEI-silicon interaction after various numbers of battery cycling.
“The unique aspect of our method is the cryo-STEM imaging and multiple physical process modeling,” Zhang said. “We can visualize the evolution of the silicon and SEI after the cyclic running of the battery; in parallel we can recapitulate the whole microstructural evolution process during cycling using computational simulations. That’s the novelty of this research.”
The study is published in the journal Nature Technology.