Relaxation of Stress Propagation in Alloying-Type Sn Anodes for K-Ion Batteries

Abstract

Alloying-type metallic tin is perceived as a potential anode material for K-ion batteries owing to its high theoretical capacity and reasonable working potential. However, pure Sn still face intractable issues of inferior K+ storage capability owing to the mechanical degradation of electrode against large volume changes and formation of intermediary insulating phases K4Sn9 and KSn during alloying reaction. Herein, the TiC/C-carbon nanotubes (CNTs) is prepared as an effective buffer matrix and composited with Sn particles (Sn-TiC/C-CNTs) through the high-energy ball-milling method. Owing to the conductive and rigid properties, the TiC/C-CNTs matrix enhances the electrical conductivity as well as mechanical integrity of Sn in the composite material and thus ultimately contributes to performance supremacy in terms of electrochemical K+ storage properties. During potassiation process, the TiC/C-CNTs matrix not only dissipates the internal stress toward random radial orientations within the Sn particle but also provides electrical pathways for the intermediate insulating phases; this tends to reduce microcracking and prevent considerable electrode degradation. The introduction of TiC/C-carbon nanotubes (CNTs) matrix improves the electrical conductivity and mechanical integrity of Sn in the composite anode. During potassiation process, the matrix provides critical functions that inhibits the propagation of microcracks within the Sn grains by suppressing huge volume change as well as providing an electrical pathway, thereby, preventing electrode degradation and improving the reversible electrochemical K-ion storage process.image