Encapsulating hetero-Cu3Ge/Ge into nitrogen-doped carbon matrix for advanced lithium storage

Abstract

The traditional graphite anode with a specific capacity of 372 mA h g−1 for lithium-ion batteries (LIBs) can’t satisfy the increasing demands of energy density. Germanium (Ge) anode material has been considered as a promising candidate owning to its higher theoretical specific capacity (∼1600 mA h g−1). Unfortunately, lithiation/delithiation process of Ge produces a huge volume variation, resulting in poor electrochemical performances. Herein, we designed and prepared a unique Ge-based composite that immersing hetero-Cu3Ge/Cu into a nitrogen-doped carbon matrix (CG/G@NC). In this delicate architecture, both NC and electrochemically inert Cu3Ge act as conductive additives and volume buffers to improve conductivity and mitigate volume changes, respectively. Also, heterostructure possesses good charge transfer kinetics and offers an additional Li+ diffusion path. As result, the Li+ diffusion in CG/G@NC composite is ∼930 times as fast as commercial Ge and ∼320 times as fast as NC. As expected, the as-prepared CG/G@NC composite exhibits superior outstanding cycle stability (455 mA h g−1 after 500 cycles at a constant current density 1000 mA g−1) and exceptional rate capability. Meaningfully, encapsulating Ge-based heterostructure materials with functional components into the carbon matrix is a promising method to facilitate the practical application of Ge-based anode materials.