NAPANODE · Molecular Foundation of Structural and Dynamic Transformations in Novel Sodium-Ion Battery Materials

Molecular Foundation of Structural and Dynamic Transformations in Novel Sodium-Ion Battery Materials

The future of widespread clean energy relies heavily on understanding, developing, and optimizing materials for electrochemical energy storage. The influence of short-range structure on macroscopic device properties during operation has hindered implementation of promising technologies such as Na-ion batteries. Na-ion batteries offer a more sustainable solution for energy storage compared to their Li-ion counterparts because Na is cheaper, more abundant, and more widespread in the Earth’s crust. Efforts to develop Na-ion batteries have led to the discovery of cathode materials for Na-ion batteries, but the identification of suitable anode materials has been more arduous. Many intercalation and alloying anode materials that work well in Li-ion batteries fail in Na-ion chemistries, such as graphite or Si. Phosphorus (P) is an exceptionally promising anode material for Na-ion batteries because it offers the highest theoretical capacity of any known anode material, with the end member composition Na3P corresponding to a capacity of 2596 mA h g-1. Unfortunately, P-based anodes suffer from performance degradation issues such as low conductivity and poor capacity retention over multiple cycles. Correlating changes in material structure with specific electrochemical signatures in the charge-discharge profiles allows us to understand which processes immediately precede and follow degradation in anodes for Na-ion batteries. Here, we used solid-state NMR in combination with powder X-ray diffraction (XRD) and theoretical calculations to monitor the evolution of NaxP phases that form on (de)sodiation in black P anodes in Na-ion batteries. We identified key structural units in the amorphous intermediates (P helices) as well as provided the first assignment of the final discharge product of the crystalline architecture, Na3P, in Na-ion batteries.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз