Insights into electrochemical performances of NiFe2O4 for lithium-ion anode materials

Nano-structured metallic oxides and carbon composites (NiO@C, Fe3O4@C and NiFe2O4@C) are successfully fabricated by the low-temperature calcinations of Ni/Fe precursors in an inert atmosphere. Density functional theory calculations show that atom rearrangements of NiFe2O4@C in unit cells are observed with respect to NiO@C and Fe3O4@C, leading to the altered exposed crystal planes and oxygen atoms redistributions on these exposed planes. Likewise, the metallic electron distributions are also changed within NiFe2O4@C due to bimetallic synergistic effects. In such fabricated scheme with the terephthalic acid template, the unique morphologies and structural characteristics of NiFe2O4@C are obtained with oxygenrich exposed crystal planes, which are conductive to improving the conductivity, accommodating volume changes, providing rapid electron and Li ion transportations. Compared with NiO@C and Fe3O4@C, the fabricated NiFe2O4@C as lithium ion anodes can achieve the extremely high discharge capacity of 1808.8 mAh g-1 at 100 mA g-1, impressive reversible capacity of 1153.6 mAh g-1 after 200 cycles at 500 mA g-1 and average capacity of 647.1 mAh g-1 at 5000 mA g-1. The full battery is also assembled by NiFe2O4@C and LiNi0.8Co0.1Mn0.1O2 as anode and cathode, and shows a superior high specific energy of 432.0 Wh kg-1, which is far higher (1.5 times) than commercial full batteries. (c) 2021 Elsevier B.V. All rights reserved.