Structural, magnetic, and electrochemical properties of hierarchical microspindle-like Fe_2−xMn_xO₃ composites from thermal decomposition of oxalates

The hierarchical microspindle-like Fe–Mn oxalates were fabricated by solvothermal method. After the following calcination, the as-derived Fe_2−xMn_xO₃ composite oxides still maintain the hierarchical morphology of micro spindle which consisted of nanoparticles as the primary building blocks and secondary layered structure. As the calcination temperature elevated from 400 to 1000 °C, the average size of primary nanoparticles dramatically increased from 5 to 300 nm and the phase composition changed from γ-Fe₂O₃ to FeMnO₃ and α-Fe₂O₃ mixture. Moreover, the magnetic property transformed superparamagnetic into antiferromagnetic nature. The exotic structure displays superior electrochemical performances as Li-ion battery anode materials. The reversible capacity of material calcined at 800 °C is up to 620.0 mAh/g at 2 A/g and coulombic efficiency is maintained around 99.0% besides initial charge–discharge efficiency after 500 cycles. The excellent lithium storage performance emerges from the distinctive hierarchical structure, phase compositions, and highly homogenous distribution of Fe and Mn which endow materials with more Li⁺ insertion/extraction channels, oxygen vacancies, feebly magnetic property, and structural stability.