Cation-disorder zinc blende Zn0.5Ge0.5P compound and Zn0.5Ge0.5P–TiC–C composite as high-performance anodes for Li-ion batteries

Abstract

Designing a novel anode material with suitable elemental composition and bonding structure for improving the limited capacity and poor lithium-ion conductivity of lithium-ion batteries (LIBs) is still challenging. Here, guided by first-principles calculations, we report a higher crystal symmetric, cation-disordered zinc blende Zn_0.5Ge_0.5P anode material with high-capacity and high-rate capability owing to superior electron and lithium-ion transport compared to the parent allotrope chalcopyrite ZnGeP₂. The Zn_0.5Ge_0.5P anode exhibits a large specific capacity of 1435 mA h g⁻¹ with a high initial Coulombic efficiency of 92%. An amorphization–conversion–alloying reaction mechanism is proposed based on ex situ characterizations including X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. During lithiation, the material phase-changes through Li₃P, LiZnGe, β-Li₂ZnGe, and α-Li₂ZnGe intermediates that provide suitable transport channels for fast diffusion of lithium ions. During delithiation, LiZn, Li₁₅Ge₄, and Li₃P nanoparticles reassemble into Zn_0.5Ge_0.5P. A Zn_0.5Ge_0.5P–TiC–C composite with finer particle size and enhanced electronic conductivity exhibits an initial specific capacity of 1076 mA h g⁻¹ and a capacity retention of 92.6% after 500 cycles.