Doping of Ni and Zn Elements in MnCO₃ : High-Power Anode Material for Lithium-Ion Batteries

Herein, Ni and Zn elements are doped simultaneously in MnCO₃ and microspheric Mn_x Ni_y Zn_z CO₃ is successfully obtained. Atomic mapping images reveal that the Ni and Zn elements have been successfully doped in MnCO₃ and thus the prepared sample is not a mixture of MnCO₃ , NiCO₃ , and ZnCO₃ . It is the first time that the atomic mapping images of ternary transition metal carbonates have been demonstrated so far. The scanning transmission electron microscopy - annular bright field (STEM-ABF) image successfully confirms the formation of oxygen vacancies in Mn_x Ni_y Zn_z CO₃ , which is beneficial to improve the electrical conductivity. The evolution of the microstructure from crystal to amorphization during cycling process confirmed by the fast Fourier transform patterns effectively lowers the overpotential of the conversion reaction and accelerates the conversion between Mn²⁺ and much higher valence of Mn element, contributing to the superior capacity of Mn_x Ni_y Zn_z CO₃ electrode. As anode material for lithium-ion batteries, the prepared Mn_x Ni_y Zn_z CO₃ exhibits excellent long-term cycling stability and outstanding rate performance, delivering the superior reversible discharge capacities of 1066 mA h g^-1 at 500 mA g^-1 after 500 cycles and 760 mA h g^-1 at 1 A g^-1 after 1000 cycles. It is the first time that Mn_x Ni_y Zn_z CO₃ has been synthesized and used as anode for lithium-ion batteries so far.