Executive Summary : | The depletion of fossil fuels and CO₂ emissions have led to a growing need for electrical energy storage systems, particularly for hybrid electric vehicles and plug-in hybrid electric vehicles. Lithium-ion batteries (LIBs) are the only choice for large-scale energy storage, but lithium scarcity poses a challenge to their widespread use in grid-scale energy storage. The next generation of alternative energy storage systems, sodium-ion batteries (SIBs), is considered due to the natural abundance of sodium and its widespread distribution. SIBs have been explored minimally due to low energy density, low standard electrochemical potential, and the larger ionic radius of Na. This presents challenges in developing good sodium intercalating materials with optimal electrochemical energy storage behavior. While significant progress has been made in developing electrode and electrolyte materials using advanced diagnostic tools, challenges persist in developing high-rate long calendar life SIBs due to slower ion transport and larger volume expansion upon Na insertion and extraction. Tailoring the scale and structure of electrode materials can improve electron transport or ion transport, with dimensional functionality providing unique physical and chemical properties such as high ionic conductivity, good thermal, and outstanding mechanical properties. Two-dimensional materials, such as nanosheets, offer advantages for SIBs, such as good mechanical exibility, short ion diffusion lengths, and a large exposed surface for electrochemical reactions. However, the underlying mechanism of Na ion storage in 2D materials remains unclear. Further study is needed to obtain better electrochemical performance in SIBs. |