Stable sodium-metal batteries with a hierarchical structured electrode toward reversible confinement of Na dendrites

Sodium metal is a promising candidate for the future of rechargeable batteries. However, a significant problem, that is, the growth of sodium dendrites, which are uncontrolled microscopic structures that reduce battery performance and stability, remains unaddressed. To resolve this issue, the development of three-dimensional (3D) nanostructured hosts to prevent dendrite growth and cease the buildup of inactive sodium has been proposed. However, research on developing an uncomplicated process to design these 3D hosts is currently lacking. In this study, we used the ice-templating method to form a self-supporting 3D hierarchical porous structure using a graphene oxide dispersion. This approach offers significant benefits in terms of scalability and cost-effectiveness. The resulting porous design offers numerous nucleation sites, which in turn reduce the intensity of local electric fields around dendrites and lower the current density. Consequently, sodium ions are deposited more evenly, which helps inhibit dendrite growth. Our test results indicated stable cycling performance, with 250, 200, and 150 cycles achieved for deposition volumes of 0.25, 0.5, and 1.0 mAh cm−2, respectively, at a constant current density of 0.25 mA cm−2. By utilizing in situ optical cell analysis, we observed the effective suppression of dendrite growth. Furthermore, ex situ examination confirmed the absence of dendrite formation, even at a high deposition capacity of 5.0 mAh cm−2. These results underline the potential of using a 3D hierarchical porous structure to effectively improve the performance and longevity of sodium-metal batteries.