Pseudocapacitive Li+ storage boosts ultrahigh rate performance of structure-tailored CoFe2O4@Fe2O3 hollow spheres triggered by engineered surface and near-surface reactions

Abstract

Transition metal oxides are regarded as the promising anodes for lithium ion batteries owing to the high theoretical capacities. However, the mechanical and electrochemical degradations severely reduce the electrode lifetime and limit its practical application. Here, for the first time, a novel CoFe2O4@Fe2O3 nanocomposites combing dual Li-ions channels and stabilized hollow sphere architecture is reported. The unique transport routes for lithium ion have been created by the design of surface holes and inner channels, offering extra lithium storage sites and accelerating its transport. Quantitative kinetic analysis reveals that the capacity based on hollow sphere heterostructured NLCFs is governed by pseudocapacitance, especially at high current rates, exhibiting excellent rate performance and high specific capacity. Benefiting from the steady sphere hollow configuration and abundant ions channels, the NLCFs nanocomposites deliver excellent long-term stability (520 and 477 mAh g−1 at 5 and 10 A g−1 for 2000 cycles, respectively) with ultrahigh Coulombic efficiency (more than 99.5%). And the full cell can remain a reversible capacity of 516 mAh g−1 at the current density of 1 A g−1 after 500 cycles. This interesting dual lithium ion channels design opens a new avenue to build high-power LIBs for electrochemical energy applications.