A Passionfruit‐Like Carbon‐Confined Cu₂ZnSnS₄ Anode for Ultralong‐Life Sodium Storage

Abstract The sodium‐ion battery (SIB) is one of the new generation of electrochemical energy storage devices, although its life‐time needs to be improved. To assemble an SIB with an ultralong life‐time, passionfruit‐like Cu₂ZnSnS₄ nanoparticles confined with nitrogen‐doped carbon (CZTS@C) are synthesized. As an alternative anode for an SIB, the CZTS@C anode exhibits a reversible capacity of 461 mA h g⁻¹ at a current density of 50 mA g⁻¹ after 140 charge/discharge cycles and excellent cycling stability (e.g., a capacity of 146 mA h g⁻¹ at 4 A g⁻¹ even after 1000 charge/discharge cycles). Such high performance originates from multiple electrons involved in the electrochemical reactions of the CZTS@C anode, as verified by in situ X‐ray diffraction measurements. As a conductive maskant, the carbon shell enhances the electric conductivity of the CZTS@C anode and further behaves as a blocked layer to maintain the structural integrity of this anode, namely to avoid the loss of active components. Several heterostructures that promote the reaction kinetics of the Na⁺ storage are formed in the subsequent charging process, as proved by ex situ transmission electron microscopy. The remarkable performance based on this low‐cost CZTS anode may pave the way to develop commercial SIBs.