Three-dimensional crosslinked nanoarchitectonics of CoP@NC anchored on Ti3C2Tx with high ionic diffusion and enhanced sodium storage performance

Abstract

Transition metal phosphides (CoP, etc.), featuring rich natural abundance and remarkable theoretical capacity, suffer from extremely poor rate capability and severe energy decay for sodium storage due to their huge volume change and low electronic conductivity. Herein, an elaborate hierarchical superstructure, nitrogen-doped carbon wrapped CoP in-situ anchored on Ti3C2Tx MXene (CoP@NC/Ti3C2Tx), was fabricated by crosslinking ZIF-67 on Ti3C2Tx flakes followed by successive carbonization and phosphorization. In principle, the dual modification for CoP nanoparticles through NC coating and Ti3C2Tx support can dramatically accelerate the ionic/electronic transportation and alleviate the structure change upon repeated sodiation/desodiation, thus leading to superior electrode integrity, modified ohmic polarization, and excellent electrochemical reversibility. Consequently, the elaborated hierarchical superstructure delivers impressive sodium storage performances with large capacity (396.06 mA·h/g at 0.1 A/g up to 100 cycles), robust rate performance (237.8 mA·h/g at 2.0 A/g), and satisfied cyclability (capacity retention of 81.3% at 1.0 A/g after 1,200 cycles). In principle, systematic electrochemical and characterizations measurements manifest that the high pseudocapacitive effect to charge storage, enhanced ionic diffusion kinetics, and remarkable electrochemical reversibility contribute to the impressive sodium storage performance of target CoP@NC/Ti3C2Tx. Importantly, the unique modification strategy reported in this study paves a way to fabricate high-performance electrode for SIBs.