Self‐Regulation of Spin Polarization Density Propelling the Ion Diffusion Kinetics for Flexible Potassium‐Ion Batteries

Abstract Potassium ion batteries (PIBs) have aroused intensive research interest owing to their abundant source, low cost, and suitable working potential. Here, a V 2 C‐VO 2 nanoribbon intertwined nanosheet 3D multi‐heterostructure with rich heterointerface and heterojunction is fabricated via a facile solution‐based method for realizing a highly flexible and robust anode material of PIBs. The co‐existence of V 2 C‐VO 2 in the constituent individual nanoribbon and nanosheet generates rich heterojunctions and heterointerfaces in this hetero‐dimensional and multi‐scale heterostructure, which not only constructs interconnected 3D channels for rapid electron/ion transfer and diffusion, but also greatly enhances the structural durability and mechanical robustness. With experimental results and systematical theoretical studies, it is confirmed that the V 2 C‐VO 2 multi‐heterostructure can self‐regulate the spin polarization density of constituent individual V 2 C and VO 2 , which propels the K + ion diffusion kinetics during charge and discharge processes. Consequently, the multi‐heterostructure‐based electrode can maintain a capacity of ≈ 200 mAh g −1 over repeated 2000 cycles at 1 A g −1 . Practically, the flexible full cells exhibit decent electrochemical property under intensive bending conditions, holding great promise for flexible electronic devices.