Exceeding Theoretical Capacity in Exfoliated Ultrathin Manganese Ferrite Nanosheets via Galvanic Replacement‐Derived Self‐Hybridization for Fast Rechargeable Lithium‐Ion Batteries

Abstract Mixed transition metal oxides are promising anodes to meet high‐performance energy storage materials; however, their widespread uses are restrained owing to limited theoretical capacity, restricted synthesis methods and templates, low conductivity, and extreme volume expansion. Here, Mn 3‐x Fe x O 4 nanosheets with interconnected conductive networks are synthesized via a novel self‐hybridization approach of a facile, galvanic replacement‐derived, tetraethyl orthosilicate‐assisted hydrothermal process. An exceptionally high reversible capacity of 1492.9 mAh g −1 at 0.1 A g −1 is achieved by producing Li‐rich phase through combined synergistic effects of amorphous phases with interface modification design for fully utilizing highly spin‐polarized surface capacitance. Furthermore, it is demonstrated that large surface area can effectively facilitate Li‐ion kinetics, and the formation of interconnected conductive networks improves the electrical conductivity and structural stability by alleviating volume expansion. This leads to a high rate capability of 412.3 mAh g −1 even at an extremely high current density of 10 A g −1 and stable cyclic stability with a capacity up to 921.9 mAh g −1 at 2 A g −1 after 500 cycles. This study can help to overcome theoretically limited electrochemical properties of conventional metal oxide materials, providing a new insight into the rational design with surface alteration to boost Li‐ion storage capacity.