Researchers from the Indian Institute of Technology Gandhinagar (IITGN) successfully developed a novel hybrid electrode that enhances the stability and performance of Aluminium-ion hybrid capacitors (AIHCs). Hybrid capacitors are a promising class of advanced energy storage systems that combine the long device function time based on the energy stored and quick energy release features of batteries and supercapacitors, respectively. AIHCs are attracting attention due natural abundance and low cost. However, designing compatible materials with long cycle life and environmental sustainability is a limitation.
The study, recently published in the Journal of Energy Storage, addressed this issue by developing a new cathode material comprising metal-organic frameworks (MOF-5), boron nitride (BN), and carbon nanotubes (CNTs) with a CNT-coated aluminium foil anode. MOFs are crystalline materials with adjustable pores and a large surface area that can benefit energy storage applications. BN can act as a structural support with its properties of thermal stability and mechanical strength. CNTs form interconnected networks that can provide exceptional electrical conductivity and mechanical strength.
“The combination of these components resulted in a hybrid material with superior properties. It is highly competitive, excelling in capacity, energy and power densities, and cycling stability. Its performance can be attributed to features like the hybrid and interconnected porous structure and efficient transport of ions or charged particles within the device,” explained Dr Prashant Dubey, the first author of the study. Dr Dubey completed this project as an Early Career Fellow at IITGN. Currently, he is a Japan Society for the Promotion of Science (JSPS) postdoctoral fellow at Nagoya University, Japan.
According to Dr Atul Bhargav, “An important feature was the use of CNT coatings on aluminium foil. These coatings increase the surface conductivity and cause the aluminium ions to spread evenly during the charge and discharge process. It effectively prevents the corrosion and formation of a thin ‘blocking’ layer on the aluminium surface that is bad at conducting electricity (passivation).” Dr Bhargav is a Professor in the Department of Mechanical Engineering and the Principal Investigator at the Energy Systems Research Laboratory (ESRL). One of his core research interests focuses on building energy and energy use optimisation, which aligns with several Department of Energy and Ministry of New and Renewable Energy initiatives from the Government of India. He is the founder and director of Cellegant Energy Systems, a startup incubated at IIT Gandhinagar Innovation and Entrepreneurship Center. Dr Bhargav is also associated with the Kiran C Patel Centre for Sustainable Development (KPCSD) at IITGN.
The hybrid device significantly outperformed devices that involved individual MOF-5, BN, and CNT. It also stored more than twice as much energy (energy density of 140 Wh/kg) compared to BN-aluminium-based and MOF-5-aluminium-based systems. Further, it maintained a superior energy-releasing capacity (power density of 14.6 kW/kg). Interestingly, the assembled device also retained 92.2% of its initial capacity even after 20,000 charge-discharge cycles. Such long-term stability is essential for practical energy storage applications. Another crucial aspect was the prominent diffusion contribution or the efficient movement of ions or charged particles inside the material, which led to more effective energy storage.
The increasing global demand and the necessity to shift to renewable sources have contributed to advanced energy storage systems. Aligning with this idea, this research integrates different materials based on their unique properties into a single electrode, underscoring its potential for next-generation sustainable and high-performance energy storage technologies. The researchers acknowledged the Central Instrumentation Facility and Early Career Fellowship from IITGN.