Study of the Mechanical Properties of Lithium Dendrites

Formation and Risks of Dendrites in Batteries

In lithium-ion batteries, nanostructured formations known as dendrites can develop. These structures are capable of causing short circuits, battery failure, or even spontaneous combustion. Dendrites are thin, needle-like metallic formations that grow inside the battery during charging, sprouting from the anode. Instead of lithium being evenly distributed across the surface of the negative electrode, the metal can accumulate in these structures, gradually penetrating deeper into the battery.

The thin separator between the electrodes is at risk of being damaged by dendrites, which can lead to contact between the anode and cathode, resulting in a short circuit, overheating, and battery damage. In extreme cases, this can cause the battery to break apart or catch fire. Even in less severe scenarios, fragments of dendrites become inactive lithium, which no longer participates in energy storage.

Mechanical Properties of Dendrites

Dendrites are about 100 times thinner than a human hair. After they form, a solid electrolyte interphase (SEI) layer develops around them, making them rigid and capable of piercing battery components. Under stress, these structures can break, turning into so-called "dead lithium," which reduces the battery's capacity.

It was previously believed that lithium in large quantities is plastic and soft, and that dendrites would have similar properties. However, experiments have shown that dendrites behave differently: they can be brittle and break like dry spaghetti.

New Research Methods

An international team of researchers from Singapore and several US universities, including the New Jersey Institute of Technology, has developed special platforms for collecting dendrites from working batteries and studying their mechanical characteristics. To achieve this, hermetically sealed environments were created to prevent chemical changes in lithium upon contact with oxygen, and high-resolution electron microscopy was used.

Multiscale modeling has helped explain why lithium dendrites exhibit unusual mechanical properties. It was found that their brittleness is linked to constraints from the solid electrolyte interface and strengthening at the nanoscale.

Prospects for Preventing Dendrite Growth

Understanding the physics behind dendrite formation opens new avenues for preventing their destructive effects on batteries. Researchers are exploring ways to block the formation of the SEI layer that strengthens dendrites, as well as using lithium alloy anodes to reduce their tendency to become brittle and break.

The results provide alternative mechanisms for dendrite penetration and the formation of "dead lithium," along with recommendations for designing lithium-metal batteries. These discoveries represent an important step toward developing methods to prevent the damaging impact of dendrites on batteries.