Tailoring nanostructured Na4Fe3(PO4)2P2O7 cathode with high phase purity for ultrahigh-rate and long-life sodium-ion batteries

Nanoscale Na₄Fe₃(PO₄)₂P₂O₇ (NFPP) with enhanced high-rate and cyclic performances positioning it as a prospective cathode material for fast rechargeable sodium-ion batteries (SIBs). However, the previously proposed methods for preparing nanoscale NFPP materials exhibit drawbacks such as prolonged synthetic period, as well as inevitable formations of electrochemically inactive impurities that compromise the practical sodium-storage performance of NFPP. Herein, we achieve a short-time preparation of pure-phase NFPP nanoparticles decorated with carbon nanotubes scaffold (denoted as NFPP@C@MCNTs) using high-boiling organic solvents assisted colloidal synthesis (HOS-CS) technique followed by calcination. High purity of active phase and conductive carbon network of NFPP@C@MCNTs endows it with an impressive long-term stability (81 % of capacity retention over 4500 cycles at 20 C) and a remarkable rate capability (66.6 mAh g⁻¹ at 30 C). Further, in a full-cell device pairing the NFPP@C@MCNTs cathode with a commercial hard carbon (HC) anode, it delivers a reversible capacity of up to 87.8 mAh g⁻¹ at an ultrahigh rate of 10 C, ranking among the superior-performing NFPP-based full batteries reported currently. This study provides a highly pure-phase NFPP nanostructured cathode with excellent fast-charging capability, offering a significant pathway towards accelerating commercialization of SIBs.