Electrochemical capacitors (aka supercapacitors, ultracapacitors, or electric double layer capacitor (EDLC)) are important energy storage devices that bridge the gap between batteries (high energy) and electrostatic capacitors (high power). Traditional supercapacitors are most suited for applications that require burst-mode power delivery (i.e., several fast charge-discharge cycles rather than long-term energy storage, for example, uninterrupted power supply (UPS) as backup power sources (such as memories, microcomputers, system boards, and clocks), emergency doors, “stop-start” applications in modern cars, and regenerative braking energy recovery systems in vehicles, metro-rails, elevators, and cranes. In addition to developing and improving traditional supercapacitors, we are also focusing our research attention to the next-generation technology, the ‘structural supercapacitors’ which store (and deliver) electrical energy while at the same time performing structural functions of carrying mechanical loads (which is the dream of any Systems Engineer). Here, we develop new design and microwave-assisted synthesis strategies for nanomaterials to enhance the performance of electrode materials for supercapacitor applications. We specifically focus on nanostructured manganese-based materials (1-D, 2-D and 3-D structures) as well as carbon nanostructures, including nanofibers.
Conventional rechargeable lithium-ion battery technologies have dominated (and will continue to do so for many years ahead) the markets for consumer electronics and electric vehicles. To reduce cost and enhance safety, our research is focussed on Mn-based cathode materials. We specifically focus on developing high-energy spinel, lithium manganese nickel oxide (LMNO), and high-capacity layered oxide materials, the lithium nickel manganese cobalt oxides (NMC). Some of the major challenges that conspire against the performance and widespread utilization of these Mn-based electrode materials include poor initial coulombic efficiency and ‘capacity fading’ (i.e., loss of capacity upon repetitive charge-discharge cycles). We are solving this problem by the adopting a plethora of microwave-assisted synthesis strategies aimed at tuning the redox-chemistry and stabilizing the structure of the materials.
Sodium (Na) is described as the most viable alternative to Li; it is cheap, abundant (4th most abundant element in the earth’s crust) and is uniformly distributed around the world. We investigate sodium-ion batteries (SIB) as they represent the most attractive alternative to LIBs, especially for stationary or home-electricity storage applications (due to weight considerations). Mn-based rechargeable aqueous mobile ion batteries (RAMIB) are being investigated in our group. Apart from Na-ion carrier, we are interested in other ions (such as K+, Zn2+ and Mg2+) and dual carrier systems (such as the Na-Zn hybrid).
Rechargeable lithium-sulfur battery (LiSB) is one the most promising next-generation battery technologies. It is potentially a low-cost energy storage system due to the natural abundance and non-toxicity of elemental sulfur and offers very high theoretical energy density (2500 Wh kg-1). However, the application of LiSB has been hindered by inter-related challenges of poor utilization of the insulating sulfur, and polysulfide shuttling event. We plan to solve these problems by strategic imprisonment of the sulfur and/or the use of high-performing electrocatalysts.
Rechargeable aqueous zinc-air battery (RAZAB) is a next-generation battery for stationary/home electricity storage and portable electronics; it is a low-cost, high theoretical specific capacity (1086 W h/kg) battery that utilizes atmospheric oxygen. The key challenges to commercialization are low cycle life and the inability to find the best-forming bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). We explore various electrode materials as potential bifunctional electrocatalysts for the development of RAZAB.
A fuel cell is an electrochemical reactor that converts chemical energy directly to electricity. The anodic reactions involve hydrogen oxidation reaction (HOR) and alcohol oxidation reaction (AOR) are driven by precious metal nanostructured catalysts while the cathodic reaction involves oxygen reduction reaction (ORR) and can be driven by either precious or non-precious nanostructured electrocatalysts. The key research challenges include reducing the mass loading of the expensive precious metals and improving the electrode kinetics. To tackle these problems, our research is focused on developing Pd- and Pt-based anode bimetallic and ternary catalysts as well as electrode support materials.
Renewable electricity-powered electrocatalytic water-splitting is a promising strategy to produce clean hydrogen and oxygen fuels from abundant water resource, which is crucial for energy security and emission reduction. The development of bifunctional electrocatalysts which are capable of concurrently enhancing the sluggish kinetics of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is critically important to achieving very efficient overall water splitting. Our research is focused on developing low-cost bifunctional electrocatalysts (such as carbon and base metal materials).
Various electrochemical sensors (including immunosensors and gas sensors, focusing on poverty-related diseases such as Tuberculosis, cholera, and alcohol and drugs of abuse) are being developed in our group. Some of the materials we develop for energy storage and conversion systems work well as electrochemical sensor materials. Here, the aim of our research is to meet most (if not all) of the WHO’s ASSURED criteria (Affordable, Sensitive, Specific, User-friendly, Robust and rapid, Equipment-free, and Deliverable to those who need them).
Solid-state electrolytes promise to complement the conventional liquid electrolytes for energy storage and conversion systems; they are safer to use and may allow the commercialisation of high-voltage and high-capacity cathode materials. We are currently studying several materials for potential development of all-solid-state, flexible, wearable energy storage and sensor devices. For example, some of the materials being explored are nanocomposite polymer electrolytes (electrospun nanofibers re-enforced with ceramic materials, including the Garnet-type oxide family, Li7-xLa3Zr2-xMxO12 (LLZM, where M = dopant such as Al).