Constructing Carbon Nanotube-Enhanced Ultra-Thin Organic Compounds with Multi-Redox Sites for "All-Temperature" Potassium-Ion Battery Anode and its Step-Wise K-Storage Mechanism

Organic compounds are regarded as important candidates for potassium-ion batteries (KIBs) due to their light elements, controllable polymerization, and tunable functional groups. However, intrinsic drawbacks largely restrict their application, including possible solubility in electrolytes, poor conductivity, and low diffusion coefficients. To address these issues, an ultrathin layered pyrazine/carbonyl-rich material (CT) is synthesized via an acid-catalyzed solvothermal reaction and homogeneously grown on carbon nanotubes (CNTs), marked as CT@CNT. Such materials have shown good features of exposing functional groups to guest ions and good electron transport paths, exhibiting high reversible capacity and remarkable rate capability over a wide temperature range. Two typical electrolytes are compared, demonstrating that the electrolyte of LX-146 is more suitable to maximize the electrochemical performances of electrodes at different temperatures. A stepwise reaction mechanism of K-chelating with CO and CN functional groups is proposed, verified by in/ex situ spectroscopic techniques and theoretical calculations, illustrating that pyrazines and carbonyls play the main roles in reacting with K+ cations, and CNTs promote conductivity and restrain electrode dissolution. This study provides new insights to understand the K-storage behaviors of organic compounds and their "all-temperature" application. An acid-catalyzed solvothermal reaction is proposed to form ultra-thin layered materials (CT, approximate to 5 nm in thickness) growing on carbon nanotube (CNT), denoted as CT@CNT composite. CNT facilitates to exposure more active sites of CT, shortens the diffusion paths, and construct a conductive network. CT with a pore size of 11.24 angstrom has many active functional groups (CO and CN) and a three-step K-storage mechanism is confirmed by in/ex-situ spectroscopic technique and theoretical calculations. Meanwhile, CT@CNT composite has exhibits impressive electrochemical performance and high possibility for the "all-weather" application (-30-45 degrees C), providing new insights to understand the K-storage behaviors and realizing the "all-climate" application.image