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

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 Zn0.5Ge0.5P 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 Zn0.5Ge0.5P 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, beta-Li2ZnGe, and alpha-Li2ZnGe intermediates that provide suitable transport channels for fast diffusion of lithium ions. During delithiation, LiZn, Li15Ge4, and Li3P nanoparticles reassemble into Zn0.5Ge0.5P. A Zn0.5Ge0.5P-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.

Automated summary

Designing novel anode materials to improve the limited capacity and poor lithium-ion conductivity of lithium-ion batteries remains challenging. In this study, a higher crystal symmetric, cation-disordered zinc blende Zn0.5Ge0.5P anode material was developed with superior electron and lithium-ion transport compared to the parent allotrope chalcopyrite ZnGeP2. The proposed amorphization-conversion-alloying reaction mechanism provides suitable transport channels for fast diffusion of lithium ions during lithiation, leading to a high specific capacity and initial Coulombic efficiency. Additionally, a Zn0.5Ge0.5P-TiC-C composite exhibited promising performance with enhanced electronic conductivity and capacity retention after cycling.