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 [VO_n] 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.

Keywords: Aqueous zinc-ion batteries; Extreme environments; K+ and C3N4 co-intercalation; Reaction kinetics; Synergistic effect.

Fig. 1

a XRD pattern of NVO, KNVO, NVO-C₃N₄, and KNVO-C₃N₄, respectively. b FTIR spectra of NVO, KNVO, NVO-C₃N₄, and KNVO-C₃N₄, respectively. c-e SEM, TEM, and HRTEM images of KNVO-C₃N₄. f HAADF-STEM image of KNVO-C₃N₄ and the elemental distribution of C, N, O, V and K. g, h XPS spectra of V 2p and O 1s. i EPR spectra of NVO, KNVO, NVO-C₃N₄, and KNVO-C₃N₄, respectively

Fig. 2

a The initial three CV curves of the KNVO-C₃N₄ electrode were recorded at 0.2 mV s⁻¹. b CV curves of NVO and KNVO-C₃N₄ after the fifth cycle at 0.2 mV s⁻¹. c Rate performances of NVO, KNVO, NVO-C₃N₄, and KNVO-C₃N₄. d Rate performance of KNVO-C₃N₄ cathode compared with the literatures. e Ragone plot of KNVO-C₃N₄ cathode compared with literatures. f, g Cycling performances of NVO, KNVO, NVO-C₃N₄, and KNVO-C₃N₄ at 2 and 10 A g⁻¹, respectively

Fig. 3

a Self-discharge based on the NVO, KNVO, NVO-C₃N₄, and KNVO-C₃N₄ cathodes. b CV curves of KNVO-C₃N₄ electrode with capacitive- and diffusion-controlled contributions at 1.0 mV s⁻¹. c Ratio of capacitive contribution of NVO, KNVO, NVO-C₃N₄, and KNVO-C₃N₄ electrodes at 1.0 mV s⁻¹. d, e Zn²⁺ diffusion coefficients versus different discharge/charge states. f, g Nyquist plots for KNVO-C₃N₄ electrode during the discharge and charge process. h R_ct for KNVO-C₃N₄ electrode during the discharge and charge process

Fig. 4

a, b Differential charge density with Zn²⁺ intercalation in NVO and KNVO-C₃N₄. c Calculated Zn²⁺ diffusion barriers in NVO, KNVO, NVO-C₃N₄, and KNVO-C₃N₄. d, e The schematic of the structure after insertion of Zn²⁺ into NVO and KNVO-C₃N₄. f Calculated Zn²⁺ insertion formation energy in NVO, KNVO, NVO-C₃N₄, and KNVO-C₃N₄. g, h MD simulation structures of ion diffusion through NVO and KNVO-C₃N₄ nanochannels. i Number evolution of Zn.²⁺ in the samples with different content of C₃N₄

Fig. 5

a Ex situ XRD patterns of the KNVO-C₃N₄ electrode at different voltage states during the first cycle of charge/discharge processes at 0.5 A g⁻¹. b Ex situ Raman spectra of the KNVO-C₃N₄ electrode at different voltage states during the first cycle of charge/discharge processes at 0.5 A g⁻¹. c-e The corresponding ex situ XPS spectra of Zn 2p, V 2p, and O 1s. f-i SEM, TEM, and HRTEM of the KNVO-C₃N₄ electrode at different states. j Schematic illustration of the reaction mechanism

Fig. 6

a The cycling performance of the pouch cell at the current density of 1 A g⁻¹ under multiple bending at room temperature (The illustrations are schematic diagrams of the pouch cell and the thermometer working at different bending angles, respectively.) b Global temperature distribution on Dec. 1, 2024 (Image from Climate Reanalyzer, Climate Change Institute, University of Maine, USA). c, d Rate performance and long-term cycling stability of pouch cell at 60 °C. e, f Rate performance and long-term cycling stability of pouch cell at − 20 °C. g Comparison of the capacity of pouch cells and other reported batteries at low temperatures