Blue phosphorus-like layered GeTe for high rate and long cycle Li-ion batteries

The blue phosphorus with unique layered structure and high reactivity shows great potential for advanced energy storage and conversion, while it can't be synthesized and stabilized at normal pressure & temperature on thermodynamics thus fail in battery application. Herein, a stand-in of blue P, e.g., blue phosphorus-like layered GeTe, is interestingly found to possess similar rhombohedral structural characteristics and properties like blue P. Furthermore, other germanium-based sulfides, e.g., GeS and GeSe, which account for the orthorhombic layered structure like black phosphorus, are also synthesized and investigated the lithiated-behavior for comparison. Different from the "armchair" edge feature of black phosphorus-like GeS & GeSe, this blue phosphorus-like GeTe exhibits a unique "zigzag" arrangement toward smaller band gap (0.56 eV) and thus higher conductivity (4.3 x 101 S m-1). Benefitted from above structural advantages, this blue phosphorus-like atomic arrangement of GeTe enables an obvious lithiated-conversion plateau, higher Li-diffusivity (6.02 x 10-11 cm2 s-1), larger faradaic pseudo-capacitive contribution (79.2 %) and thereby, better rate capability (851 mAh g-1 and 78 % retention at 2000 mA g-1) and cyclability (948 mAh g-1 and 93 % retention after 300 cycles) can be obtained. The above investigation of GeTe for Li-ion batteries may give a better understanding of electrochemical behaviors of blue phosphorus-like layered materials toward advanced energy storage.