Key Takeaways & Executive Findings
- •• • The optimized GLSHC-HNO3 anode delivers an ultrahigh reversible capacity of 446.1 mAh g−1 at 50 mA g−1 and retains 237.3 mAh g−1 at 2 A g−1, demonstrating superior rate capability for high-power sodium-ion storage. • • The full sodium-ion capacitor achieves an energy density of 114.4 Wh kg−1 at 290 W kg−1 and 43.1 Wh kg−1 at 1450 W kg−1, with a maximum power density of 5800 W kg−1, outperforming many reported SICs. • • Long-term cycling stability is exceptional: 84.3% capacity retention after 5000 cycles at 2.0 A g−1 with nearly 100% Coulombic efficiency, indicating robust electrode durability for practical applications. • • The synthesis integrates hydrothermal pretreatment, low-temperature carbonization, and acid-mediated functionalization to create hierarchical porosity and multi-element co-doping, offering a scalable and sustainable route for biomass-derived carbon anodes.
Abstract
Sodium-ion capacitors (SICs) are attractive for low-cost and safe energy storage, but their practical development is limited by sluggish Na+ storage kinetics and structural instability of anodes. Control of both bulk structure and surface chemistry can address these limitations. We report a heteroatom-rich porous carbon (HRPC) derived from spores via hydrothermal pretreatment, low-temperature carbonization, and acid-mediated functionalization. The optimized GLSHC-HNO3 anode exhibits hierarchical porosity and multi-element co-doping, enabling rapid ion/electron transport, improved electrolyte wettability, and abundant Na+ adsorption sites. Density functional theory calculations reveal distinct contributions of different heteroatom configurations to sodium adsorption. The HRPC anode delivers an ultrahigh reversible capacity of 446.1 mAh g−1 at 50 mA g−1, retains 237.3 mAh g−1 at 2 A g−1, and shows excellent cycling stability. A full SIC with a polyaniline-derived porous carbon cathode achieves an energy density of 114.4 Wh kg−1 at 290 W kg−1, 43.1 Wh kg−1 at 1450 W kg−1, and a maximum power density of 5800 W kg−1, with 84.3% capacity retention after 5000 cycles and nearly 100% Coulombic efficiency. This work establishes a scalable, sustainable route for converting biomass into high-value carbon anodes, providing a new pathway for high-performance sodium-ion energy storage.
1. Introduction
The global energy landscape demands high-performance, cost-effective storage solutions. Lithium-ion capacitors, while promising, are constrained by the scarcity and high cost of lithium, limiting large-scale deployment. Sodium-ion capacitors (SICs) emerge as a viable alternative due to sodium's natural abundance and low cost, yet their anodes suffer from sluggish Na+ kinetics and structural instability, hindering practical application.
This work addresses these bottlenecks by engineering both the bulk pore structure and surface chemistry of spore-derived carbon. Through a combination of hydrothermal pretreatment, low-temperature carbonization, and acid-mediated functionalization, the resulting heteroatom-rich porous carbon (HRPC) achieves rapid ion/electron transport, enhanced electrolyte wettability, and abundant Na+ adsorption sites. The optimized GLSHC-HNO3 anode demonstrates exceptional capacity and cycling stability, and the full SIC device delivers high energy and power densities, establishing a scalable, sustainable route for high-performance sodium-ion storage.
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Wang Yiming, Qiu Kerou, Yu Haidong, Hou Zhiqiang, Chen Haotian, Cheng Jiahao, Zhang Yabin, Zhu Jinliang, Zou Bingsuo (2026). Spore-derived porous carbon with tailored heteroatom doping for anode of sodium-ion capacitors. New Carbon Materials. https://doi.org/10.1016/S1872-5805(26)61100-6
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Frequently Asked Questions
What specific acid treatment conditions (e.g., acid type, concentration, temperature, duration) were used to synthesize GLSHC-HNO3, and how do they influence the heteroatom doping levels and pore structure?
The paper does not specify exact acid treatment parameters, but it indicates that GLSHC-HNO3 was prepared via acid-mediated functionalization, likely using nitric acid. The resulting material exhibited hierarchical porosity and multi-element co-doping, which contributed to its superior performance. For precise conditions, refer to the full experimental section in the original publication.
How does the GLSHC-HNO3 anode's performance compare to state-of-the-art carbon anodes in sodium-ion capacitors in terms of capacity retention at high current densities (e.g., 2 A g−1) and long-term cycling?
The GLSHC-HNO3 anode retains 237.3 mAh g−1 at 2 A g−1, which is competitive with or superior to many reported carbon anodes. In full-cell configuration, it achieves 84.3% capacity retention after 5000 cycles at 2.0 A g−1, demonstrating excellent long-term stability. These metrics position it among the top-performing biomass-derived carbon anodes for SICs.
What is the practical energy density and power density of the full SIC device, and how does it translate to potential applications?
The full SIC delivers an energy density of 114.4 Wh kg−1 at a power density of 290 W kg−1, and 43.1 Wh kg−1 at 1450 W kg−1, with a maximum power density of 5800 W kg−1. This performance bridges the gap between batteries and supercapacitors, making it suitable for applications requiring both high energy and high power, such as regenerative braking systems and grid frequency regulation.
What are the main degradation mechanisms observed during long-term cycling, and how does the electrode design mitigate them?
The paper reports 84.3% capacity retention after 5000 cycles, indicating minimal degradation. The hierarchical porous structure accommodates volume changes during Na+ insertion/extraction, while heteroatom doping enhances pseudocapacitive contributions and surface wettability, reducing charge transfer resistance. These factors collectively contribute to the excellent cycling stability.
What is the scalability potential of the spore-derived carbon synthesis process in terms of cost, raw material availability, and environmental impact?
Spores are a renewable biomass resource, and the synthesis involves hydrothermal pretreatment, low-temperature carbonization, and acid functionalization—processes that are relatively low-cost and scalable. The use of biomass and mild conditions aligns with green chemistry principles, making the route sustainable and potentially industrially viable. However, detailed cost analysis and scale-up studies are not provided in the abstract.
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