When re-charging, lithium + ions go through electrolyte (grey) from + electrode to - electrode (where white electrons store up). The + ions (red dots) stop when they touch a stationary - ion (green). These "dendrites" are roughly fractal trees, resulting from diffusion limited aggregation, forming at the negative electrode when Li battery is charging. When they reach the counter-electrode, they can interact with flammable electrolytes, causing a short circuit, and may make the battery catch fire.
Lithium-based batteries are powerful and lightweight, but potentially explosive. Soon after development of lithium batteries, scientists discovered the lithium ions form dendrites when recharged repeatedly. The dendrites form from the anode (green), short circuiting (shown by flashing), often catching fire. In 2019, a team led by C. Wang discovered an electrolyte solvent prompts the dendrite growth. A similar dendrite pattern is seen in crystal formation, coral, fungi growth, liquid seeping through soil, lightning, or what you see when you drop dye into glue, which is called viscous fingering. A process called diffusion-limited aggregation happens to create the same patterns as seen in viscous fingering, in which a less viscous liquid presses through a more viscous liquid. The finger-like projections result from pressure being somewhat greater at the tips. Red: + electrode (cathode) Green: - electrode (anode) White: electrons Copper color: wire Dark grey: separator Grey: electrolyte Cathode is the positive electrode, where reduction (gain of electrons) occurs. Anode is the negative electrode, where oxidation (loss of electrons) takes place. This is my enhanced version of Dec 2022: https://scratch.mit.edu/projects/779306552/ In 2024 I added the electron flow through wire.
