Iron–Manganese Dual-Doping Tailors the Electronic Structure of Na3V2(PO4)2F3 for High-Performance Sodium-Ion Batteries

Sep 29, 2026

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Sodium superionic conductor (NASICON)-type materials are promising cathodes for sodium-ion batteries, where Na3V2(PO4)2F3 (NVPF) stands out yet suffers from low electronic conductivity and phase impurities. A Fe and Mn dual-doped NVPF (FM-NVPF) cathode is introduced with improved phase purity, conductivity, and electrochemical activity. Ex-situ analyses and density functional theory show dopant-induced defect levels and an electronic-structure modulation driving a direct-to-indirect bandgap transition, increasing carrier concentration, accelerating transport, and enhancing stability. The FM-NVPF delivers 126.6 mAh g−1 at 0.1 C and 67.6 mAh g−1 at 50 C, with full cells reaching ~175 Wh kg−1 (cathode+anode).

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages15

Reading Time38 min

AccessFree to download

Highlights

Abstract

Keywords

Introduction

Challenges in sodium-ion battery cathodes

Promise and limitations of NVPF

Prior strategies and transition-metal doping

e-ISSN 2150-5551 CN 31-2103/TB ARTICLE [https://doi.org/10.1007/s40820-025-01881-3](https://doi.org/10.1007/s40820-025-01881-3) Cite as Nano-Micro Lett.(2026) 18:176 Received: 28 April 2025 Accepted: 21 July 2025 Published online: 5 January 2026 © The Author(s) 2026 Iron–Manganese Dual‑Doping Tailors the Electronic Structure of Na3V2(PO4)2F3 for High‑Performance Sodium‑Ion Batteries Jien Li 1,4 *, Shuang Luo2, Renjie Li 1, Yingkai Hua 1, Linlong Lyu 1, Xiangjun Pu 1, Jun Fan2, Zheng-Long Xu1,3 * HIGHLIGHTS • Regulation of the electronic structure of Na3V2(PO4)2F3 (NVPF) via iron–manganese dual-doping enhances electrical conductivity and ion diffusion kinetics. • Efficient charge transport and highly reversible Na+ de/intercalation in Fe-Mn dual-doped NVPF (FM-NVPF) enable exceptional rate capability and charge storage capacity. • The full cell with the FM-NVPF cathode and hard carbon anode displays superior rate performance and cycling stability. ABSTRACT Sodium superionic conductor (NASICON)-type materials are promising cathodes for sodium-ion batteries due to their stable multi-channel frameworks and exceptional ionic conductivity. Among them, Na3V2(PO4)2F3 (NVPF) has attracted significant attention. However, the low electronic conductivity and phase impurities limit its sodium storage capability. Herein, we present a Fe and Mn dual-doped NVPF (FM-NVPF) cathode with improved phase purity, electronic conductivity, and electrochemical activities. Detailed ex-situ analyses and density functional theory calculations reveal that Fe and Mn dopants induce defect energy levels and modulate the electronic structure, resulting ina direct-to-indirect bandgap transition in NVPF, which in turn increases carrier concentration and lifetime, accelerates ionic/electronic transport, and improves structural stability. As a result, the FM-NVPF cathode delivers a high capacity of 126.6 mAh g⁻ 1 at 0.1 C (1 C = 128 mAh g⁻ 1) and outstanding high-rate capability of 67.6 mAh g⁻ 1 at 50 C, corresponding to 1.2 min per charge. Furthermore, Na ion full cells assembled with the FM-NVPF cathodes and hard carbon anodes exhibit a high energy density of about 175 Wh kg−1cathode+anode mass and appealing cyclic stability. This work provides an efficient strategy for developing high-purity and high-performance NVPF cathode materials for advanced sodium-ion batteries . KEYWORDS Sodium-ion batteries; Sodium fluorophosphates; Electronic structure; Fe–Mn co-doping Jien Li and Shuang Luo have contributed equally to this work. * Jien Li, [ljen@gxu.edu.cn](ljen@gxu.edu.cn); Zheng-Long Xu, [zhenglong.xu@polyu.edu.hk](zhenglong.xu@polyu.edu.hk) 1 Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong 999077, People’s Republic of China 2 Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong 999077, People’s Republic of China 3 Research Institute for Advanced Manufacturing, The Hong Kong Polytechnic University, Hung Hom, Hong Kong 999077, People’s Republic of China 4 School of Resources, Environment and Materials, Guangxi University, Nanning 530004, People’s Republic of China 1 Introduction With the increasing demand for sustainable energy storage solutions, sodium-ion batteries (SIBs) have emerged as promising alternatives to lithium-ion batteries due to the abundant and low-cost availability of sodium resources [1–3] . However, the development of SIBs remains challenged by the sluggish kinetics and limited cycling stability of available cathode materials [4, 5] . Cathode materials for SIBs mainly include layered transition metal oxides, polyanionic compounds, and Prussian blue analogs, among which polyanionic structures with three-dimensional ion conduction channels and rigid frameworks are specifically promising for long-life SIBs [6] . Na3V2(PO4)2F3 (NVPF) emerges as a particularly promising candidate in this category, featuring a three

FAQs

Why is Na3V2(PO4)2F3 (NVPF) attractive for sodium-ion batteries?

NVPF provides a stable NASICON-type framework with interconnected ion-conduction channels that support rapid Na+ diffusion, along with a high theoretical capacity and robust structural stability.

What problem limits NVPF’s practical performance?

Low electronic conductivity and phase impurity formation during synthesis degrade rate capability and cycling durability.

How does Fe–Mn dual-doping improve NVPF’s electronic structure and performance?

Fe and Mn dopants create defect energy levels and modulate the electronic structure, inducing a direct-to-indirect bandgap transition that increases carrier concentration and carrier lifetime, accelerates ionic/electronic transport, and improves structural stability.

Sep 29, 2026

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