| Mar 17, 2026 |
Researchers paired lignin-derived porous carbon electrodes with a fluorinated electrolyte to build a supercapacitor operating at 4.0 volts and 77.4 Wh per kg.
(Nanowerk News) A team of researchers has built a supercapacitor that operates stably at 4.0 volts by matching a lignin-based porous carbon electrode with a purpose-built electrolyte. Published in Carbon Research (“Lignin-derived hierarchical porous carbons enabling high-voltage electrochemical capacitors with low self-discharge”), the work tackles a persistent barrier in supercapacitor design: raising voltage to increase energy storage without triggering electrolyte breakdown. Dr. Feng Gong at Southeast University and Dr. Hualin Ye at Nanjing Normal University led the effort, treating electrode structure and electrolyte chemistry as a single integrated system rather than independent components.
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Key Findings
- The supercapacitor operates at 4.0 volts with minimal self-discharge, well above the typical voltage ceiling of conventional devices.
- The system reaches an energy density of 77.4 Wh kg⁻¹, approaching levels normally associated with rechargeable batteries.
- After 10,000 charge-discharge cycles, the device retained more than 90% of its original capacity.
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Supercapacitors charge rapidly and deliver high bursts of power, but they store relatively little total energy and tend to lose their charge when idle. Higher operating voltage is the most direct route to greater energy density, yet most electrolytes decompose under that added electrical stress. The new work bypasses that limitation through a co-design strategy that engineers the solid electrode and the liquid electrolyte as a matched pair.
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| Lignin-derived hierarchical porous carbons enabling high-voltage electrochemical capacitors with low self-discharge. (Image: Reproduced from DOI:10.1007/s44246-025-00255-z, CC BY)
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The electrode starts as lignin, a polymer found in plant cell walls and generated in large quantities as waste from the paper and biorefining industries. The researchers pyrolyzed this raw material into a hierarchical porous carbon containing sub-nanometer channels. These extremely narrow pores are sized to capture and hold solvated lithium ions with high geometric precision, which directly increases the charge stored per unit mass.
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For the electrolyte, the team prepared a weakly solvating lithium-based solution mixed with a fluorinated diluent. Weak solvation allows lithium ions to shed part of their solvent shell and interact more efficiently with the tight carbon pores. The fluorinated component plays a protective role, suppressing degradation reactions and blocking parasitic chemistry that would otherwise destabilize the system at 4.0 volts.
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Together, the electrode and electrolyte pairing eliminates the rapid self-discharge that typically accompanies high-voltage supercapacitor operation. At 77.4 Wh kg⁻¹, the device’s energy density sits in a performance range between conventional supercapacitors and lithium-ion batteries. The researchers also subjected the device to 10,000 full charge-discharge cycles; it retained over 90% of its starting capacity, confirming long-term chemical and structural stability under repeated electrical stress.
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The project drew on resources from the Key Laboratory of Energy Thermal Conversion and Control at Southeast University and the Jiangsu Key Laboratory of New Power Batteries at Nanjing Normal University. By aligning the geometric properties of a bio-derived carbon with the solvation behavior of a tailored electrolyte, the researchers opened a practical route to high-voltage supercapacitors built from abundant, renewable raw materials.
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