Quantification and visualization of spatial distribution of dendrites in solid polymer electrolytes

Integrating lithium metal anodes with polymer electrolytes is a promising technology for the next generation high-energy-density rechargeable batteries. As the progress is often hindered by the dendrite growth upon cycling, quantifying three-dimensional (3D) microstructures of dendrites in polymer electrolytes is essential to better understanding of dendrite formation for the development of mitigation strategies. Techniques for 3D quantification and visualization of dendrites, especially those with low Li contents, are rather limited. This study reports quantitative measurements of the spatial distribution of Li dendrites grown in solid polymer electrolytes using 3D tomographic neutron depth profiling (NDP) with improved spatial resolution, compositional range, and data presentation. Data reveal heterogeneous distribution of Li over length scales from tens nanometers to centimeters. While most dendrites grow from the plating toward the stripping electrode with dwindling Li quantities, dendrites apparently grown from the Li-stripping electrode are also observed. The discovery is only possibly due to the unique combination of the high specificity and high sensitivity of the neutron activation analysis of Li isotope.