High-Performance Wide-Temperature Zinc-Ion Batteries with K+/C3N4 Co-Intercalated Ammonium Vanadate Cathodes

Abstract

NH4V4O10 (NVO) is considered a promising cathode material for aqueous zinc-ion batteries due to its high theoretical capacity. However, its practical application is limited by irreversible deamination, structural collapse, and sluggish reaction kinetics during cycling. Herein, K+ and C3N4 co-intercalated NVO (KNVO-C3N4) nanosheets with expanded interlayer spacing are synthesized for the first time to achieve high-rate, stable, and wide-temperature cathodes. Molecular dynamics and experimental results confirm that there is an optimal C3N4 content to achieve higher reaction kinetics. The synergistic effect of K+ and C3N4 co-intercalation significantly reduces the electrostatic interaction between Zn2+ and the [VOn] layer, improves the specific capacity and cycling stability. Consequently, the KNVO-C3N4 electrode displays outstanding electrochemical performance at room temperature and under extreme environments. It exhibits excellent rate performance (228.4 mAh g−1 at 20 A g−1), long-term cycling stability (174.2 mAh g−1 after 10,000 cycles at 20 A g−1), and power/energy density (210.0 Wh kg−1 at 14,200 W kg−1) at room temperature. Notably, it shows remarkable storage performance at −20 °C (111.3 mAh g−1 at 20 A g−1) and 60 °C (208.6 mAh g−1 at 20 A g−1). This strategy offers a novel approach to developing high-performance cathodes capable of operating under extreme temperatures.

1. Introduction

Aqueous zinc-ion batteries (AZIBs) have garnered significant interest due to their high safety, low cost, and environmental friendliness, positioning them as promising candidates for the next generation of efficient rechargeable batteries [1–4]. Although the zinc anode possesses a high theoretical specific capacity (820 mAh g−1) and a relatively low electrochemical potential (−0.76 V vs. standard hydrogen electrode) [5–7]. However, the absence of a matching cathode with high capacity, satisfactory cycling stability, and enhanced ion diffusion has severely impeded its practical application [8, 9]. Consequently, the development of an appropriate cathode remains a critical and meaningful challenge.

Recent advancements in cathode material research have made remarkable progress, mainly including vanadium (V)-based oxides, manganese-based oxides, Prussian blue analogs, and conductive metal–organic framework [10–14]. V-based oxides have emerged as a focal point of the current research due to their high theoretical specific capacity, multi-electron transfer capability of V elements, and abundant reserves [15]. Among the various V-based oxides, layered ammonium vanadate (NH4V4O10, NVO) is regarded as a promising candidate owing to several advantages [16, 17]: (i) Its larger interlayer spacing (9.8 Å) facilitates the insertion/extraction of hydrated Zn2+. (ii) It offers higher specific capacity, thereby providing enhanced energy density and power density. (iii) NH4+ forms N–H···O hydrogen bonds with the [VOn] layer, improving the structural stability and electrochemical performance of the cathode electrode. Nonetheless, research indicates that irreversible deammoniation occurs during the charge/discharge process, resulting in significant phase transitions and structural degradation. Additionally, the excess NH4+ between the V–O layers may seriously impede the insertion/extraction of Zn2+ due to strong electrostatic interactions [18].