Supercapacitors for a sustainable energy future: from materials design to multifunctional energy systems

Chandra Sekhar Rout

Professor Chandra Sekhar Rout is a full professor at the Centre for Nano & Material Sciences (CNMS), Jain University. Before joining CNMS, he was a DST-Ramanujan Fellow at IIT Bhubaneswar, India (2013–2017). He obtained his PhD from JNCASR, Bangalore (2008) under the supervision of Prof. C. N. R. Rao followed by postdoctoral research at NUS, Purdue University, and UNIST. His research is focused on applications of 2D layered materials for different devices. He has authored more than 250 research papers and 10 books. His h-index is 72 with total citations of ∼20,000. He was ranked in the top 2% of scientists by the Stanford study in 2020–2025.

Yusuke Yamauchi

Professor Yusuke Yamauchi is an internationally distinguished researcher in inorganic materials chemistry and nanotechnology. He is particularly renowned for his pioneering contributions to the development of conductive porous materials, a new class of porous materials that differs fundamentally from conventional porous systems such as zeolites, mesoporous silica, and metal–organic frameworks (MOFs). He holds a professorship at the Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland (UQ), Australia, and also serves as a Distinguished Professor at Nagoya University, Japan. He was selected as an Australian Laureate Fellow and has received numerous prestigious awards and honors worldwide, including recognition as a Highly Cited Researcher, awards from the Chemical Society of Japan, and the Commendation for Science and Technology by MEXT, Japan.

Subrata Kundu

Dr Subrata Kundu received his PhD from the Indian Institute of Technology (IIT), Kharagpur, India, in 2005 and did his post doc at the University of Nebraska, Lincoln and Texas A&M University, Texas, USA from 2005 to 2010. He is currently working as a Scientist F (Professor, AcSIR) at CSIR-CECRI, Karaikudi, India. Kundu became a fellow of the Royal Society of Chemistry (FRSC) in 2023 and has worked as an associate editor on JMC A and Materials Advances since 2022 and Nature's Scientific Reports since 2015. He also serves on the editorial advisory boards of ACS Applied Materials & Interfaces and Inorganic Chemistry Frontiers. His h-index is 78 with Google Scholar citations of ∼27600. Kundu's group works at the forefront of materials science, with an emphasis on energy, environment and catalysis.

The advent of renewable energy sources and portable devices has created a significant demand for high-performance energy storage systems. Supercapacitors, also known as electrochemical capacitors, offer an attractive solution because of their high power density, excellent rate capability, long cycle life, and inherent safety, thereby combining some of the advantages of conventional capacitors and batteries. However, their relatively low energy density remains a major limitation, necessitating further investigation into charge-storage mechanisms and the development of new materials with high capacitance and electrical conductivity. According to their charge-storage mechanisms, supercapacitors can be classified into electric double-layer capacitors, pseudocapacitors, and hybrid devices. Considerable progress in this field has been achieved through the use of carbon materials, metal oxides, and conducting polymers. At the same time, the application of in situ and operando techniques has provided deeper insight into the processes occurring at the electrode/electrolyte interface, thereby facilitating the rational design of advanced materials.

Recent progress in two-dimensional materials has led to a dramatic improvement in supercapacitor performance, particularly through the development of MXenes. As reported by Chinnalagu et al., MXenes represent a revolutionary class of materials that have been advanced through rational approaches such as defect engineering, heteroatom doping, and structural engineering. Moreover, machine learning combined with experimental techniques and density functional theory has emerged as an efficient tool for predicting novel electrode materials.¹ In addition, Jinagi et al. emphasized the importance of moving from conventional ex situ characterization methods to in situ or operando techniques, which enable real-time analysis of electrochemical reactions and provide new insights into kinetics, charge-storage mechanisms, and interfacial interactions.²

In another study, Sahoo et al. identified carbon materials as essential building blocks for next-generation supercapacitors because of their tunable porosity, high electrical conductivity, and structural diversity. They also highlighted the importance of rational synthesis strategies and machine learning methods for optimizing these complex systems. Taken together, these studies illustrate the growing integration of advanced materials design, in situ characterization techniques, and data-driven approaches. Nevertheless, key challenges such as scalability, long-term performance, and incomplete mechanistic understanding remain unresolved.³ Beyond material selection, defect engineering and compositional tuning have emerged as powerful strategies for improving the electrochemical performance of supercapacitors. In their recent work, Karmakar et al. demonstrated that intentional heteroatom doping and the introduction of vacancy defects can enhance electrical conductivity and increase the number of electrochemically active sites within electrode materials. As a result, ion accessibility and charge-transfer rates are significantly improved, leading to higher capacitance.⁴ Similarly, K. K. Sahoo et al. highlighted the importance of doping in tailoring the composition of transition-metal-based electrode materials. In this context, doping modifies the electronic structure by regulating electron-transport pathways, thereby optimizing redox behavior and charge-storage efficiency. Collectively, these studies confirm that atomic engineering should not be regarded merely as a complementary strategy, but rather as a central principle in the design of next-generation supercapacitors.⁵

The importance of defect, interfacial and structural engineering in improving the performance of emerging energy-storage devices has become increasingly evident. In this regard, Dutta et al. demonstrated oxygen-deficient bimetallic oxide M_0.11W_0.89O_3–x for flexible energy storage and electrochromic applications, highlighting the role of defect-rich oxide design in charge storage and optical modulation.⁶ In addition, Shaikh et al. reported hierarchically structured Sb₂O₃–Bi₂O₃ nano-leaves that combine high supercapacitor energy density with efficient HER and OER catalysis, demonstrating the potential of multifunctional electrode architectures.⁷ Likewise, Vikraman et al. showed that surface engineering of molybdenum-integrated cobalt telluride electrodes can enhance battery-type charge-storage behavior.⁸ Taken together, these studies underscore the importance of rational defect, surface and hierarchical structural design for maximizing active-site utilization and maintaining efficient charge transport in supercapacitors.

In recent years, substantial progress has also been made in multifunctional supercapacitors, driven by the need to integrate energy storage with additional functionalities within a single device. One notable example is the electrochromic supercapacitor reported by Samtham et al., which combines energy-storage capability with optical functionality, enabling visualization of the charging/discharging process and opening opportunities for applications in smart windows and display technologies.⁹ Similarly, Cho et al. demonstrated fluorinated ionogels for low-temperature micro-supercapacitors, showing that electrolyte and ion-transport engineering can maintain device performance under demanding operating conditions.¹⁰ These examples clearly demonstrate the ongoing transition from conventional energy-storage systems to multifunctional devices in which optical functionality, electrolyte design, operating-temperature tolerance and electrochemical performance are important design considerations.

Nanoscale structuring and morphology control remain important approaches for enhancing electrochemical performance by improving ion accessibility and facilitating efficient charge transport. For example, Nagarani et al. demonstrated activated carbon microtube electrodes incorporating cement and fly ash for enhanced supercapacitor performance, illustrating how low-cost carbon frameworks can improve charge storage.¹¹ Likewise, Murugesan et al. described B-site-engineered medium-entropy perovskites as dual-purpose materials for piezoelectric energy harvesting and supercapacitor electrodes; non-equimolar B-site engineering improved conductivity and ion diffusion, supporting enhanced energy-storage performance.¹² These modifications also help mitigate the degradation associated with repeated charge/discharge cycles. Overall, these examples show that not only chemical composition but also rational nanostructuring and morphology tuning are crucial for achieving high electrochemical performance.

In addition to electrode materials, separators and porous-carbon architectures have also been explored as strategies for improving overall device performance. In this context, Patra et al. reported nanodiamond-based TiO₂ nanocomposite separators for flexible paper-based supercapacitors, where TiO₂–nanodiamond interfacial coupling reduces charge-transfer resistance and improves capacitance and cycling stability.¹³ Similarly, Du et al. demonstrated metalion-mediated mesopore engineering in hierarchical porous carbons for enhanced high-rate volumetric capacitance.¹⁴ These studies indicate that, beyond optimizing individual active materials, careful engineering of separators, pore architectures and device components is essential for achieving highperformance energy-storage systems.

The rapid progress of supercapacitors reflects a broader paradigm shift in electrochemical energy storage. With the emergence of heteroatom-doped carbons, nanostructured materials, and advanced electrolytes, the development of supercapacitors capable of delivering high power density, high energy density, and long-term durability is becoming increasingly feasible. At the same time, a deeper fundamental understanding of these devices, together with increasingly sophisticated characterization techniques, is enabling the more rational design of electrode materials and device architectures. Multifunctional supercapacitors are also opening new opportunities in flexible electronics and other advanced technologies. Ultimately, the future of this field lies in the development of supercapacitors that can be seamlessly integrated into large-scale energy systems, hybrid energy-storage platforms, and smart electronic networks.

References

1. D. K. Chinnalagu, S. Arumugam Thirumalai, S. Sahoo and B. Chakraborty, J. Mater. Chem. A, 2026, 14, 17003–17061,  10.1039/D6TA00255B.
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