Selective phosphorylation of MOF to construct KTP/KTOP/C heterojunction for high-performance potassium-ion batteries

Abstract

Polyanion compounds are considered as promising electrodes for potassium-ion batteries (PIBs) due to their structural diversity and chemical versatility. However, the cycling performance of previously reported electrodes at high current densities still suffers from their relatively sluggish electron and ion transport kinetics. Here, by combining K2Ti2(PO4)3 (KTP) framework with KTiOPO4 (KTOP) composition, we construct a series of KTP/KTOP/C heterojunctions (denoted as KTP/KTOP/C-n) via selectively phosphorylatiny from metal-organic framework (MOF) precuror, and demonstrate the successful synergistic cooperation of both electron and ion transport kinetics by carefully controlling the structure and composition. Comparative analysis and density functional theoretical calculations confirm the reaction kinetics and pseudocapacitive behaviors can be dramatically promoted by synergistically structural, electronic and ionic modulations. Consequently, the optimized KTP/KTOP/C-2 delivers an impressive specific capacity of 140 mAh/g after 150 cycles at 100 mA g−1 and superior cycling stability with 79 mAh/g for 2000 cycles at a high current of 1000 mA g−1. Furthermore, it displays outstanding rate performance, achieving 87 mAh/g at 2000 mA g−1.