Enabling Stable and Rapid Lithium/Sodium Storage by Anchoring Bimetallic Selenides with a Heterogeneous Interface on Reduced Graphene Oxide

Transition metal selenides have emerged as attractive negative electrode candidates for rechargeable lithium-/sodium-ion batteries (LIBs/SIBs) thanks to their superior theoretical energy storage capability. Unfortunately, their practical application faces significant challenges due to low conductivity, structural degradation from volume changes, and sluggish ion diffusion kinetics. Herein, a nitrogen-doped carbon (NC) coated Cu₂Se-CoSe₂ heterostructure, which is embedded in reduced graphene oxide (rGO) sheets (Cu₂Se-CoSe₂@NC@rGO), is synthesized. Cu₂Se-CoSe₂@NC@rGO nanospheres possess a high specific surface area of 207.02 m² g^-1, which provides ample active sites for ion reactions. The heterojunction between Cu₂Se and CoSe₂ creates a built-in electric field, which is conducive to ion and electron transport. Additionally, NC shell and rGO matrix work synergistically to suppress volume expansion and enhance structural stability. In LIBs, it has a considerable specific capacity (1161.6 mA h g^-1 after 200 cycles at 0.2 A g^-1) and good cycling stability (1261.1 mA h g^-1 after 500 cycles at 1 A g^-1). In SIBs, it maintains 422.4 mA h g^-1 under 0.1 A g^-1 after 200 cycles. These advancements demonstrate the promise of Cu₂Se-CoSe₂@NC@rGO as a promising anode in LIBs and SIBs.