Molybdenum-based materials for sodium-ion batteries

Sodium-ion batteries are considered one of the most promising candidates for affordable and scalable energy storage as required in smart grid and renewable energy. One of the principal challenges sodium-ion batteries being faced is to search suitable anode materials that can accommodate and store large amounts of Na+ ions reversibly and sustainably at reasonable galvanostatic rates. Molybdenum-based materials such as oxides and sulfides might meet this challenge as they afford a capacity much greater than those of the carbonaceous materials and exhibit rich Na-reaction chemistry. However, these materials are facing several technical issues, such as multiple-phase transformation, particle pulverization as the result of volume swelling, and low surface activity during sodiation/desodiation. To tackle these issues, materials design and engineering are of indispensability. In this brief review, we present a state-of-the-art overview of the research progress of molybdenum-based materials for sodium storage, and highlight materials engineering strategies that are capable of addressing the mentioned challenges. We also offer valuable insights into their further development direction and discuss their potentiality in practical batteries.