Double‐Helix Structure in Carrageenan–Metal Hydrogels: A General Approach to Porous Metal Sulfides/Carbon Aerogels with Excellent Sodium‐Ion Storage

Abstract The metal sulfide‐carbon nanocomposite is a new class of anode material for sodium ion batteries, but its development is restricted by its relative poor rate ability and cyclic stability. Herein, we report the use of double‐helix structure of carrageenan–metal hydrogels for the synthesis of 3D metal sulfide (M x S y ) nanostructure/carbon aerogels (CAs) for high‐performance sodium‐ion storage. The method is unique, and can be used to make multiple M x S y /CAs (such as FeS/CA, Co 9 S 8 /CA, Ni 3 S 4 /CA, CuS/CA, ZnS/CA, and CdS/CA) with ultra‐small nanoparticles and hierarchical porous structure by pyrolyzing the carrageenan–metal hydrogels. The as‐prepared FeS/CA exhibits a high reversible capacity and excellent cycling stability (280 mA h −1 at 0.5 A g −1 over 200 cycles) and rate performance (222 mA h −1 at 5 A g −1 ) when used as the anode material for sodium‐ion batteries. The work shows the value of biomass‐derived metal sulfide–carbon heterostuctures in sodium‐ion storage.