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

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, Mn3‐xFexO4 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. In the study reported herein, the rational design of efficient hybrid ultrathin manganese ferrite nanosheets through interfacial modifications can effectively exceed theoretically limited energy storage capacity in form of surface capacitance by amorphous phases with fully utilizing highly spin‐polarized electrons, as well as allow to facilitate both kinetics and structural stability.