Three-dimensional Mn-doped Zn2GeO4 nanosheet array hierarchical nanostructures anchored on porous Ni foam as binder-free and carbon-free lithium-ion battery anodes with enhanced electrochemical performance

Abstract

We report on three dimensional Mn-doped Zn₂GeO₄ hierarchical nanosheet arrays anchored on porous Ni foam as binder-free lithium-ion battery (LIB) anodes with enhanced electrochemical performance. Homogeneous Mn doping effectively induces a great microstructure evolution from nanowire arrays of pure Zn₂GeO₄ to nanosheet arrays of Mn-doped Zn₂GeO₄ samples. LIB anodes based on 7% Mn-Zn₂GeO₄ nanosheet array hierarchical nanostructures anchored on Ni foam display significantly improved electrochemical Li storage performance, showing a superior reversible capacity of 1301 mA h g⁻¹ at a current density of 100 mA g⁻¹ after 100 cycles, almost two times higher than that of 660 mA h g⁻¹ of pure Zn₂GeO₄ samples. An extraordinarily excellent rate capability with a capacity of 500 mA h g⁻¹ at a current density of 2 A g⁻¹ can be obtained for LIB anodes based on Mn-doped Zn₂GeO₄ hierarchical nanostructures. The great enhancement of the electrochemical lithium storage performance can be attributed to three-dimensional interconnected conductive channels composed of Ni foam, which not only serves as the current collector but also buffers the volume change of the active material upon cycling. Additionally, Mn doping can greatly improve charge transport kinetics at the interface between the electrode and the electrolyte.