Processing mechanism synergizing surface and intercalation pseudocapacitance engineering fast-charging Li-based anode materials

Abstract

Pseudocapacitive material can achieve rapid charge and discharge response. In this study, a vanadium-based conductive network hydrate (Na0.13Mg0.02)V2O5·0.98H2O (NMVO) was designed. The Na+ and Mg2+ in NMVO are sandwiched between two layers of vacancy-ordered prisms and monoclinic nanonetwork V3O7 (VO2:V2O5 = 1:1) to form a conductive network with a layer spacing of up to 11.67 Å, this structure facilitates rapid interlayer diffusion of cations and enhanced conductivity. Reduction-NMVO (r-NMVO) with hierarchical heterostructures was prepared via an in-situ electrochemical process to generate interlayer vanadium-based active sites (LiV3O8, LiV2O5, Na3V3O8, MgVO3) with multi-electron reaction, which enhanced the generation of surface redox pseudocapacitance. The interlayer heterostructure is integrated with the core of the precursor V3O7 to form an active site-rich conductive network with strong pulse impact resistance, which promotes the generation of intercalated pseudocapacitance and increases the cycle stability of the electrode. This intercalation-surface redox pseudocapacitive mechanism was confirmed by first-principles, in-situ, and ex-situ characterization analysis. The r-NMVO|Li battery still maintains a capacity of 95.5 % after 65,500 cycles at a current density of 50 A g−1. These results contribute directly to the realization of stable, fast charge and discharge material design.