Unraveling the Mystery of Dendrite Growth in Lithium Metal Batteries

In recent years, lithium metal batteries have gained significant attention due to their higher energy density compared to traditional lithium-ion batteries. However, their widespread adoption has been hindered by a major concern - the growth of dendrites and whiskers within the battery's structure. These tiny, rigid tree-like structures can cause catastrophic damage to the battery by piercing the separator and accelerating unwanted chemical reactions.

To better understand this phenomenon, researchers at the Pacific Northwest National Laboratory (PNNL) have employed advanced microscopy techniques to visualize the growth process. Using an atomic force microscope (AFM) integrated with an environmental transmission electron microscope (ETEM), scientists were able to measure the tiny forces involved in whisker growth and capture high-resolution videos of the process.

The team's findings revealed that the energy dynamics on the surface of the solid-electrolyte interphase (SEI) play a crucial role in pushing lithium ions into the growing column. This slow and steady process is reminiscent of stalagmite formation in caves, where minerals precipitate over time to form towering columns.

Interestingly, the PNNL team discovered that ethylene carbonate, a common solvent used to enhance battery performance, can leave batteries vulnerable to damage. The researchers pinpointed this culprit by studying the growth of whiskers within specially designed nanosized lithium metal batteries.

The origin of dendrites and whiskers lies in the SEI, where the solid lithium surface meets the liquid electrolyte. This film acts as a boundary layer, influencing the flow of ions and electrons during battery operation. By understanding the mechanisms that drive whisker growth, researchers hope to develop new strategies for preventing their formation.

The PNNL team's discovery is a significant breakthrough in the quest to overcome the limitations imposed by dendrite growth. With this knowledge, scientists can explore novel approaches to manipulate electrolyte composition and design more robust battery architectures. Ultimately, these advancements could pave the way for the widespread adoption of lithium metal batteries, unlocking their full potential as high-performance energy storage devices.

Reference: Wang et al., 'In situ observation of lithium dendrite growth in a lithium metal battery' Nature Nanotechnology 14, (2020).

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