Constructing Built-In Electric Field in NiCo 2 O 4 -CeO 2 Heterostructures to Regulate Li 2 O 2 Formation Routes at High Current Densities.

Developing catalysts with suitable adsorption energy for oxygen-containing intermediates and elucidating their internal structure-performance relationships are essential for the commercialization of Li-O 2 batteries (LOBs), especially under high current densities. Herein, NiCo 2 O 4 -CeO 2 heterostructure with a spontaneous built-in electric field (BIEF) is designed and utilized as a cathode catalyst for LOBs at high current density. The driving mechanism of electron pumping/accumulation at heterointerface is studied via experiments and density functional theory (DFT) calculations, elucidating the growth mechanism of discharge products. The results show that BIEF induced by work function difference optimizes the affinity for LiO 2 and promotes the formation of nano-flocculent Li 2 O 2 , thus improving LOBs performance at high current density. Specifically, NiCo 2 O 4 -CeO 2 cathode exhibits a large discharge capacity (9546 mAh g -1 at 4000 mA g -1 ) and high stability (>430 cycles at 4000 mA g -1 ), which are better than the majority of previously reported metal-based catalysts. This work provides a new method for tuning the nucleation and decomposition of Li 2 O 2 and inspires the design of ideal catalysts for LOBs to operate at high current density.