As the demand for batteries for portable electronics, electric vehicles, and large-scale energy storage continues to increase, improvements in capacity, safety, lifetime, and particularly cost, to the current Li-ion standard are crucial. To address these needs, Na-ion batteries are a promising alternative for long-term energy storage sustainability in terms of both cost and natural abundance. For example, highly competitive layered Na-transition metal phosphate and oxide intercalation cathode materials offer a cost-effective alternative to their Li-ion counterparts. Further, Na-ion systems allow the replacement of expensive Cu current collectors with Al. However, robust candidates for anode materials in Na systems that offer equivalent capacities are lacking. As a result, progress in the development of suitable Na-ion batteries has been substantially stalled. Typical anode materials that are high performing for Li-ion systems, such as Si and graphite, do not reversibly store Na ions or suffer from low capacities, respectively. Otherwise, the high theoretical capacity for the formation of Na<sub>3</sub>P (2596 mAh/g) makes phosphorus-based materials promising candidates for anodes in Na-ion systems. <br/>Indeed, recent reports indicate that combining elemental phosphorus with a conductive layer can produce high capacity (1700-2400 mAh/g) in Na-ion batteries. However, we find that while performance near that of theoretical capacity are reached in the first cycle, the capacity retention in phosphorus anodes is poor. Here, we use nuclear magnetic resonance (NMR) to probe the phase chemistry and structural transformations that occur during electrochemical cycling to understand the species responsible for capacity fade in phosphorus anodes in Na-ion batteries. The insights gained from this work should help to guide the design of electrode materials used in next generation electrochemical energy storage devices.

Molecular origin of capacity fade in sodium ion batteries

254th National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.