Island‐Like Heterogeneous Interface Generating Tandem Toroidal Built‐In Electric Field for Efficient Potassium Ions Diffusion

Abstract For large‐size potassium accommodation, heterostructure usually suffers severe delamination and exfoliation at the interfaces due to different volume expansion of two‐phase during charge/discharge process, resulting in the deconstruction of heterostructures and shortened lifespan of batteries. Here, an innovative strategy is proposed through constructing a microscopic heterostructure system containing copper quantum dots (Cu QDs) highly dispersed in the triphenyl‐substituted triazine graphdiyne (TPTG) substrates (TPTG@CuQDs) to solve this problem. The copper quantum dots are uniformly anchored on TPTG substrates, generating a myriad of island‐like heterogeneous structures, together with tandem toroidal built‐in electric field (BIEF) between every micro heterointerface. The island‐like heterostructure endows both benefits of exposed contact interface and robust architecture. Generated tandem toroidal BIEF provides efficient transport pathways with lower energy barriers, reducing the diffusion resistance and facilitating the reaction kinetics of potassium ions. When used as anode, the TPTG@CuQDs exhibit highly reversible capacity and low‐capacity degradation (≈0.01% over 5560 cycles at 1 A g −1 ). Moreover, the TPTG@CuQDs‐based full cell delivers an outstanding reversible capacity of ≈110 mAh g −1 over 800 cycles at 1 A g −1 . This quantum‐scale heterointerface construction strategy offers a new approach toward stable heterostructure design for the application of metal ion batteries.