Sodium-Ion Capacitor Technologies and Performance

Sodium-ion capacitors (SICs) represent a hybrid energy storage technology that bridges the high energy density of batteries with the rapid charge–discharge capability and long cycle life of supercapacitors. By employing sodium rather than lithium, these devices benefit from the earth’s abundant sodium resources and lower material costs, addressing sustainability and large-scale deployment. Central to their performance are electrode architectures that balance capacity and kinetics: negative electrodes typically rely on pseudocapacitive materials or intercalation hosts, while positive electrodes exploit high-surface-area carbons for electrical double-layer capacitance. Advances in nanostructuring, doping and composite design have yielded electrodes with enhanced ion transport pathways, enlarged interlayer spacing and robust structural integrity under repeated cycling. Meanwhile, electrolyte engineering—ranging from optimised organic solvents to ionic liquids—has extended the electrochemical stability window and improved ionic conductivity. Recent efforts focus on tuning electrode–electrolyte interfaces and mitigating the inherent trade-offs between energy density, power density and operational lifetime. As a result, state-of-the-art SICs now achieve energy densities approaching those of sodium-ion batteries at power densities characteristic of supercapacitors, positioning them as promising candidates for grid balancing, electric mobility and portable electronics.

Research from Nature Portfolio

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Research from all publishers

Hierarchically structured niobium-oxide microflowers have been developed as negative electrodes for flexible planar sodium-ion micro-supercapacitors. These microflowers feature ultrathin, porous nanosheets uniformly coated with conductive carbon, which together deliver high reversible capacity and excellent rate performance. When paired with activated carbon positive electrodes, the resulting devices exhibit outstanding areal energy density, wide voltage windows and prolonged cycling stability, demonstrating a viable route to miniaturised, wearable power modules.

A dual-carbon sodium-ion hybrid capacitor has been realised using oxygen- and nitrogen-doped graphitic carbons derived from metal-azolate frameworks. By tailoring pyrolysis conditions, researchers produced cathode materials with record-high surface area and abundant mesopores, and complementary anode carbons with rich nitrogen sites for rapid sodium storage. The assembled cells achieve energy densities surpassing those of conventional sodium-ion batteries, power densities exceeding 20 000 W kg⁻¹ and robust stability over thousands of cycles, illustrating the potential of framework-derived carbons in large-scale energy buffering.

Two-dimensional mesoporous titanium nitride nanosheets have been explored as pseudocapacitive anodes for high-power sodium-ion capacitors. A topochemical synthesis yields TiN with a high surface area and interconnected mesoporosity, promoting rapid surface-redox reactions between Ti⁴⁺ and Ti³⁺ states. The material supports ultrafast sodiation without structural degradation, enabling hybrid capacitors to deliver both high energy density and high power density alongside extended cycle life, highlighting the promise of surface-redox pseudocapacitive strategies.

Sodium-Ion Capacitor Technologies and Performance publication trend

The graph below shows the total number of articles in sodium-ion capacitor technologies and performance across all publications each year (not limited to Nature Index journals).

Technical terms

Sodium-ion capacitor: A hybrid electrochemical device that utilises sodium ions to combine battery-type energy density with supercapacitor-type power density and cycling stability.

Pseudocapacitance: A charge storage mechanism involving fast, reversible surface redox reactions rather than solely electrostatic ion adsorption.

Intercalation: The reversible insertion of sodium ions into the crystal lattice of an electrode material during charge and discharge processes.

Mesoporosity: The presence of pores in the 2–50 nm range within an electrode material, facilitating rapid ion transport and high accessible surface area.

References

1. Hierarchically Structured Nb2O5 Microflowers with Enhanced Capacity and Fast-Charging Capability for Flexible Planar Sodium Ion Micro-Supercapacitors. Nano-Micro Letters (2024).
2. 3D Porous Oxygen‐Doped and Nitrogen‐Doped Graphitic Carbons Derived from Metal Azolate Frameworks as Cathode and Anode Materials for High‐Performance Dual‐Carbon Sodium‐Ion Hybrid Capacitors. Advanced Science (2023).
3. Boosted Surface‐Redox Pseudocapacitance in 2D Mesoporous TiN for High‐Power Sodium‐Ion Capacitors. Small Structures (2023).
4. Electrolyte Technologies for High Performance Sodium-Ion Capacitors. Frontiers in Chemistry (2020).