CuFeO₂-NiFe₂O₄ hybrid electrode for lithium-ion batteries with ultra-stable electrochemical performance

Stable electrode materials with guaranteed long-term cyclability are indispensable for advanced lithium-ion batteries. Recently, delafossite CuFeO₂ has received considerable attention, due to its relative structural integrity and cycling stability. Nevertheless, the low conductivity of delafossite and its relatively low theoretical capacity prevent its use as feasible electrodes for next-generation batteries that require higher reversible capacities. In this work, we suggest a simple and straightforward approach to prepare CuFeO₂-NiFe₂O₄ by introducing Ni precursor into Cu and Fe precursor to form NiFe₂O₄, which exhibits higher capacity but suffers from capacity fading, through sol-gel process and subsequent heat treatments. The presence of both NiFe₂O₄ and CuFeO₂ is apparent, and the heterostructure arising from the formation of NiFe₂O₄ within CuFeO₂ renders some synergistic effects between the two active materials. As a result, the CuFeO₂-NiFe₂O₄ hybrid sample exhibits excellent cycling stability and improved rate capability, and can deliver stable electrochemical performance for 800 cycles at a current density of 5.0 A g^-1. This work is an early report on introducing a foreign element into the sol-gel process to fabricate heterostructures as electrodes for batteries, which open up various research opportunities in the near future.