Electric field effect in a Co3O4/TiO2 p–n junction for superior lithium-ion storage

Abstract

Constructing heterojunctions holds huge potential for tuning material properties owing to the built-in charge transfer driving force, which is beneficial for the migration behavior of Li-ions. While both the electrochemistry and heterojunctions of alloying-type anodes have been studied, the role of heterojunctions in improving the Li-ion storage performance of conversion-type anodes is unclear. In this work, porous Co₃O₄/TiO₂ nanosheets (P-Co₃O₄/TiO₂ NSs) were fabricated to successfully construct a p–n junction by coating n-type TiO₂ on p-type Co₃O₄ NSs. The formation of the built-in electric field in the p–n junction significantly facilitates the charge transfer kinetics and the amorphous TiO₂ layer accommodates the volume change of the Co₃O₄ NSs, manifesting the superiority of applying the p–n junction in a conversion-type anode for the first time. When evaluated as lithium-ion battery (LIB) anodes, the P-Co₃O₄/TiO₂ NSs deliver high specific capacity, long-term cycling stability and remarkable rate capability (801 mA h g⁻¹ after 1600 cycles at a current density of 2 A g⁻¹).