The discovery of the "death zone" in the anode may make high-density silicon batteries a reality!

Introduction: American scientists have successfully simulated the key mechanism that causes the anode performance to drop rapidly when studying the silicon anode of lithium-ion batteries . Scientists say that understanding what causes silicon to expand and then decompose is an important step to prevent this situation and to produce long-lasting, high-capacity batteries .

Of the many improved energy storage technologies currently being researched , replacing graphite with silicon stands out because silicon has the potential to store 10 times more energy than graphite.

In recent years, a lot of progress has been made in the research of silicon anodes, and some companies are moving towards commercialization and large-scale production. However, there are still challenges and a lot of work to be done in the research stage to realize the potential of silicon in energy storage.

The main challenge is that when lithium ions enter the material , the material tends to expand. Eventually, this will cause the anode to crack, peel off, or otherwise fall apart, and it will not be able to recover its original structure. Many solutions proposed for this, such as coatings on the anode and using porous silicon, have shown positive results.

However, so far, few researchers have delved into the workings of the anode during battery cycling, and there is disagreement about what exactly happens at the atomic level. "Many people have imagined what might happen, but no one has really demonstrated it before," said Chongmin Wang, a scientist at Pacific Northwest National Laboratory (PNNL) in the United States.

The research team at the Pacific Northwest National Laboratory in the United States will change this situation. They combined two complex imaging techniques, sensitive element tomography and low-temperature scanning transmission electron microscopy, with an advanced algorithm to observe the operation of this process and found that the lithium anode actually pushes into the silicon structure and then flows back, leaving huge gaps in the structure. These gaps are then filled by the development of solid electrolyte inside the silicon, forming a "death zone" within the anode, which quickly increases to a significant capacity loss.

"This work provides a clear roadmap for developing silicon as anodes for high-capacity batteries," said Chongmin Wang. The most effective way to improve silicon anodes, the team concluded, is to focus on preventing or limiting the penetration of electrolytes into the anode.