Potassium-Ion Hybrid Capacitor Technology

Potassium-ion hybrid capacitors (PIHCs) merge the high energy density of battery-type electrodes with the rapid power delivery of supercapacitor-type electrodes. In a typical PIHC, a negative electrode exploits potassium-ion insertion into host materials, while a positive electrode relies on surface adsorption or electrical double-layer capacitance. The large ionic radius of potassium ions presents both opportunities and challenges: enhanced electrode kinetics and competitive cost contrast with slower diffusion and potential structural strain. Advances in electrode design, including heteroatom-doped carbons, transition-metal compounds and nanoheterostructures, have substantially improved specific capacity, rate capability and cycle life. Electrolyte engineering and binder-free cell architectures further enhance operational voltage windows and interfacial stability. As a result, state-of-the-art PIHCs can achieve energy densities comparable to lithium-ion batteries while delivering power densities on the order of kilowatts per kilogram and retaining over 80 percent capacity after thousands of cycles. These features position PIHCs as promising candidates for grid stabilisation, fast-charging electric vehicles and portable electronics.

Research from Nature Portfolio

Recent studies have demonstrated an ampere-hour-scale soft-package PIHC that achieves both rapid charging and high energy. By pairing a defect-rich, high-surface-area nitrogen-doped carbon nanotube positive electrode with a manganese-oxide quantum-dot-inlaid, expanded-spacing carbon nanotube negative electrode, and employing a non-aqueous carbonate electrolyte in a binder-free, current-collector-free design, a full cell delivers up to 4.8 V and 140 Wh kg–1 at the device level. This 1 Ah capacitor charges in six minutes and retains 88 percent capacity after 200 cycles at 10 C, with voltage retention near 99 percent under standard conditions. The work underscores the critical interplay of electrode architecture, electrolyte choice and cell configuration in achieving extreme fast-charging PIHCs.

Potassium-Ion Hybrid Capacitor Technology publication trend

The graph below shows the total number of articles in potassium-ion hybrid capacitor technology across all publications each year (not limited to Nature Index journals).

Technical terms

Hybrid capacitor: An energy device combining battery-type and capacitor-type electrodes to balance energy and power performance.

Intercalation: Reversible insertion of ions into the crystal lattice of an electrode material.

Capacitive storage: Charge storage via electrostatic adsorption at the electrode–electrolyte interface.

Energy density: Amount of energy stored per unit mass, expressed in watt-hours per kilogram (Wh kg–1).

Power density: Rate at which energy can be delivered per unit mass, expressed in watts per kilogram (W kg–1).

Specific capacity: Electrical charge stored per unit mass of electrode, expressed in milliampere-hours per gram (mAh g–1).

References

1. Ampere-hour-scale soft-package potassium-ion hybrid capacitors enabling 6-minute fast-charging. Nature Communications (2023).
2. Novel Bilayer-Shelled N, O-Doped Hollow Porous Carbon Microspheres as High Performance Anode for Potassium-Ion Hybrid Capacitors. Nano-Micro Letters (2023).
3. Direct Structure–Performance Comparison of All‐Carbon Potassium and Sodium Ion Capacitors. Advanced Science (2019).
4. Interfacial Engineered Vanadium Oxide Nanoheterostructures Synchronizing High-Energy and Long-Term Potassium-Ion Storage. ACS Nano (2022).