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Synergistic Effect on the Improved Electrochemical Performance in the Case of Fe1–xCdxCO3

The large volume change and low electronic conductivity are the two main drawbacks for metal carbonates as promising anode materials of lithium-ion batteries. Metal doping is one of the most effective methods to address these issues. Herein, cadmium-doped ferrous carbonate Fe1–xCdxCO3 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) composites have been synthesized by a simple hydrothermal method for the first time. The morphologies of FeCO3 are evolved from microspheres to the agglomerated nanoparticles and then nanocubes with the increase of Cd doping. Fe0.8Cd0.2CO3 microspheres deliver higher capacity and cycling stability in Fe1–xCdxCO3 composites and better electrochemical performance than the corresponding 0.8FeCO3 + 0.2CdCO3 mixtures owing to an inner synergistic effect between Cd and Fe atoms in Fe1–xCdxCO3. The density functional theory calculation and electrochemical impedance spectroscopy results indicate that Fe0.8Cd0.2CO3 can maintain the similar electronic structure with good electric conductivity to FeCO...