Phase Heterojunction by Constructing Built-In Electric Field toward Sodium-Rich Cathode Material

Abstract

An artificial built-in electric field from phase heterojunction is constructed within sodium-rich manganese-based layer-structured oxide O3-Na[Ni0.3Mn0.55Cu0.1Ti0.05]O2@Na2MoO4 through shared oxygen atoms. The spinel Na2MoO4 phase behaves as a p-type semiconductor, while the O3-Na[Ni0.3Mn0.55Cu0.1Ti0.05]O2 phase functions as an n-type semiconductor. It can efficiently reduce the diffusion barrier and enhance electron transport, which can adequately promote the interfacial desolvation ability and reduce bulk lattice strains. The formed spinel heterostructure with crystal structure stability can also enhance the interface Na+ diffusion and protect the electrode against moisture and carbon dioxide corrosion. Besides, the molybdenum introduction within the lattice bulk can enhance the bond covalency, fortifying lattice oxygen stability and restraining structural distortion effectively. The obtained cathode demonstrates a high up to 224.61 mAh g−1 discharge specific capacity at 0.1 C and a long cycle stability with a 60.44% capacity retention after 265 cycles at 0.5 C. This study illuminates the potential of Na-rich Mn-based oxide cathodes for high-energy-density sodium battery utilizations.