Researchers have shown that carefully tuning sulfidation temperature can guide a nickel, cobalt and iron based electrode through distinct structural phases, revealing a heterojunction composition that delivers enhanced energy storage performance. The findings provide new insight into how phase engineering could be used to design more effective supercapacitor electrodes.
Supercapacitors can charge and discharge rapidly and deliver high power, making them attractive for applications ranging from electronics to renewable energy systems. However, their relatively limited energy density remains a major obstacle to broader use. Ternary transition metal sulfides are promising electrode materials because of their electrical conductivity and electrochemical activity, but how their structures evolve during sulfidation has not been fully understood.
In the new study, Qing Pang, Hao Wu, Tengfei Wang, Boyu Liu and Hongyu Wang investigated the controlled sulfidation of nickel cobalt iron hydroxide, or NiCoFe-OH. By varying the sulfidation temperature from 35 to 115 °C, the researchers tracked how the material changed from an amorphous hydroxide to a crystalline oxide and ultimately to a crystalline sulfide.
"Rather than focusing only on the final sulfide product, we wanted to understand what happens throughout the sulfidation process and how each phase influences electrochemical performance," said corresponding author Hongyu Wang of Qinghai University. "This allowed us to identify a particularly favorable oxide and sulfide heterojunction."
At 95 °C, the material, designated NCF-S95, contained both crystalline ternary transition metal oxide and ternary transition metal sulfide. Microscopy showed that it formed a nanosheet structure, while structural analyses confirmed the coexistence of the two phases. The researchers attribute its strong performance to complementary properties: the oxide contributes structural stability, while the sulfide offers higher conductivity and electrochemical activity. The heterojunction interface may also facilitate electron and ion transport.
NCF-S95 achieved a specific capacity of 171.52 mAh g⁻¹ at 2 mA cm⁻², the highest among the tested electrode materials. It also retained 62.28% of its capacity after 10,000 cycles.
To evaluate practical energy storage potential, the team paired NCF-S95 with activated carbon to construct an asymmetric supercapacitor. The resulting device delivered an energy density of 32.7 Wh kg⁻¹ at a power density of 400 W kg⁻¹ and retained 63.1% of its capacity after 7,000 cycles. Two devices connected in series were able to illuminate an LED bulb for 14 minutes.
The study suggests that controlling intermediate phase formation during sulfidation, rather than simply maximizing sulfur incorporation, can be an effective strategy for optimizing electrode performance. The authors conclude that understanding these structural transitions could support the rational design of next generation supercapacitor materials.
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Journal reference: Pang Q, Wu H, Wang T, Liu B, Wang H. 2026. Controlled sulfidation of ternary transition metal towards high performance electrode materials for supercapacitors. Energy & Environment Nexus 2: e022 doi: 10.48130/een-0026-0015
https://www.maxapress.com/article/doi/10.48130/een-0026-0015
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About Energy & Environment Nexus :
Energy & Environment Nexus (e-ISSN 3070-0582) is an open-access journal publishing high-quality research on the interplay between energy systems and environmental sustainability, including renewable energy, carbon mitigation, and green technologies.
