High Entropy Helps Na4Fe3(PO4)2P2O7 Improve Its Sodium Storage Performance

Abstract

Recently, a high-entropy strategy has attracted extensive attention and is applied to the preparation of electrode materials for energy storage batteries, aiming to improve electrochemical performance. It is found that adjusting the conformational entropy of the material can significantly enhance ion and electron transport efficiency, as well as improve the structural stability of the host material. However, there still remains a lack of deep understanding into the high-entropy strategy, specifically regarding how this approach can alter the intrinsic properties of the material. In this work, the Na₄Fe₃(PO₄)₂P₂O₇ is designed and prepared as a model material with higher entropy, and ultimately, an optimized sample of Na_3.9Fe_2.6V_0.1Mn_0.1Cu_0.1Mg_0.1(PO₄)₂(P₂O₇) is achieved. The results indicate that increasing the entropy value of the material notably enhances its crystal structure, diffusion kinetics, and interfacial stability. Consequently, this optimized sample demonstrates deep insertion/extraction of 2.8 Na⁺, yielding an impressively high capacity of 122.3 mAh g⁻¹ at 0.1C, alongside an ultra-high rate capability of 100C. Remarkably, it also sustains performance over 14 000 cycles at 50C. This study underscores a method for fabricating high-performance electrode materials through the implementation of the entropy strategy.