Our moto

The global energy landscape is at crossroads. The world has inexhaustible supply of renewable energy. But energy storage and conversion is the bottleneck of shifting from non-renewable to renewable energy based economy. Our motto lies in contributing to the development of cheaper, safer and environmentally benign energy storage-conversion systems so that world can shrug off the too heavy reliance on fossil fuel. To surcease the energy crisis, we are working on various critical problems of rechargeable batteries and supercapacitors (both aqueous and non-aqueous systems). Our approach includes the synthesis of superior electrode (both cathode and anode) materials, in-depth studies of electrochemical properties, examining feasibility of novel electrochemical systems, addressing scale-up issues from laboratory to industry level and recycling wastes to useful energy materials. This highly interdisciplinary field incorporates applied electrochemistry, inorganic materials, solid-state chemistry and some engineering aspects. We synthesize different types of materials via various nano and micro synthesis routes. Then structural characterisation through PXRD, BET, IR, Raman, XPS, DTA, TGA, DSC, ICP-MS, XAS, etc. and morphological characterization via SEM, TEM, EDAX, etc. is performed. Thereafter, Electrochemical testing like Voltammetric studies (CV, LSV), galvanostatic cycling (C-rate, charge-discharge), impedance measurement etc. are carried out.

Lithium ion battery

Lithium ion batteries (LIB) have dominated the portable electronics sector since its commercialisation in 1991 by SONY, which led to 2019 Nobel Prize in Chemistry to three pioneers of the field – John B. Goodenough (University of Texas, Austin, USA), M. Stanley Whittingham (Binghamton University, SUNY, USA) and Akira Yoshino (Meijo University, Nagoya, Japan). Commercial LIB prototypes mainly consist of graphite as anode and lithiated transition metal oxide or phosphate as cathode. Reversible rocking back and forth motion of Li+ and electron through inner and outer circuit respectively, is at the heart of the interconversion between chemical and electrical energy during charge and discharge. LIB is considered as potential candidate for electric mobility applications across the globe. However, problems like fast charging, C-rate performance (high power density), long cycle life and safety issues generated from inherent material drawbacks still remain as liming factors. To overcome these challenges, we have set following targets –

(1) Development of Li-rich oxide materials to reach cathode capacity beyond 250 mAh/g. (2) Improving reversible cycling of high voltage silicate cathodes.(3) Synthesis of Co-free cheaper cathodes with desirable electrochemical performance.(4) Optimization of novel fabrication strategies to stabilise LIB system up to 5 V. (5) Investigating the feasibility of conversion anodes.

Sodium ion battery

Non-uniform geological distribution of Lithium demands a shift in the focus of rechargeable battery research towards establishing an alternative of LIB for large scale stationary energy storage. Sodium, the immediate analogue of lithium in the periodic table opens up the door with enormous possibilities. Along with even geological distribution of sodium metal, seawater represents an infinite reservoir of Sodium. Although Sodium ion battery (SIB) shares similar basic electrochemical principles with LIB, some inherent problems of Na+, such as larger ionic size, higher atomic weight and lower voltage with respect to Li+ limit its application to the fields where gravimetric energy density is of minor importance. Research on SIB initiated around early 1980s and currently, it is on the verge on commercialisation. However, a lot of criticalities are yet to be solved before SIB gains widespread popularity in commercial market. Our aims regarding commercialisation of SIB include:

(1) Development of robust oxide and polyanion type cathode matrix for reversible sodium storage.(2) Novel strategy to synthesize conversion-type metal oxide and sulphide anodes.(3) Conversion of waste biomass to hard carbon anodes. (4) Coating-doping strategy to improve several electrochemical issues simultaneously. (5) Feasibility study of high energy multi-stacked pouch/prismatic full SIB.

Potassium ion Battery

The search for best ‘next generation LIB alternative’ is ongoing. Researchers are diving deep into periodic table to find a system that can match or surpass current LIB standards. SIBs suffer from its own disadvantages like slow kinetics, lower output voltage and consequently lesser energy density than LIBs. Therefore, similar ‘Rocking Chair electrochemistry model’ like LIBs has been extended to potassium. The advantages of Potassium ion batteries (KIBs) are – cell potential closer to LIBs, fast diffusion as ionic radius of solvated K+ is smaller than Li+, higher abundance and most importantly, ability of potassium to alloy with graphite which sodium cannot. However, KIB model is still in developing state and struggling with long-term cyclability. Our plans to push KIB progress include:

1) Developing 2D layered electrode frameworks for achieving high cyclability. (2) Extending our investigation to organic materials for reversible potassium storage.

Lithium-Sulfur Battery

Lithium-sulfur (Li-S) battery is an emerging technology in rechargeable system with superior energy density (2500 Wh kg-1), high specific capacity (1675 mAh g-1) and also sulfur is cheap, environmentally benign active material. Generally, it consists of lithium as anode and sulfur (S8) as cathode. During discharge, Li+ from anode, migrate to cathode via the electrolyte medium, and form lithium sulfide (Li2S). The reduction of sulfur to Li2S proceeds through several intermediate polysulfide (Li2Sn, 2≤n≤8) formation. The main challenges of Li-S battery are poor conductivity of sulfur (10-30 S cm-1), large volume change (80%), solid Li2S deposition and polysulfide dissolution to electrolyte, which results capacity fading and poor cycle-life of Li-S battery. Our research is aimed towards:

1) Fabrication of porous carbonaceous nanocomposite with sulfur to enhance the conductivity. (2) Modification of electrolyte with introducing different additives to eliminate “shuttling effect” and polysulfide diffusion to anode.

Lead – Acid Battery

The lead-acid batteries (LABs) is one of the most successful aqueous electrochemical systems ever developed with more than 99% recyclability. Since its inception by Gaston Planté in 1859, no other battery is yet able to compete with it on cost grounds, although several batteries based on other chemistries are rapidly catching up recently. There are three types of lead-acid batteries in common use: (a) batteries with flooded or excess electrolyte, (b) low-maintenance lead-acid batteries with a large excess of electrolyte, and (c) batteries with immobilized electrolyte and a pressure-sensitive valve usually referred to as absorptive glass-microfibre (AGM) valve-regulated lead acid (VRLA) batteries.

Aqueous supercapacitors

Unlike batteries, supercapacitors (Electrochemical Capacitors) are known for its high power density. It consists of two electrodes ionically connected through electrolyte and separated via an ion-permeable membrane. When external voltage is applied, ions in the electrolyte are attracted by oppositely charged electrodes and forms Electric Double Layer (EDL) at electrode-electrolyte interface, thus storing energy. Supercapacitors are broadly classified into three types, namely: Electrical Double-Layer Capacitors (EDLC’s), Pseudocapacitors, and Hybrid Capacitors. EDLC’s are based on different types of carbon materials serving as electrodes, pseudocapacitors employ metal oxides or polymers while hybrid capacitors are a mixture of both EDLC’s and Pseudocapacitors. Major limiting factors of supercapacitors include low specific capacitance (device), poor energy density in comparison to batteries, and lower accessible potential window. Given the above challenges, the goals of our present work are as follows:

1) Use of metal oxides/sulfides as electrode materials to improve the overall specific capacitance resulting from the inherent faradaic reactions of the materials involved. (2) Widening the potential window by employing different electroactive metal oxides as the positive and negative electrodes. (3) Enhancement of energy density and stability by the incorporation of redox-active electrolytes and carbon-metal oxide composite electrode materials

Lead-Carbon Hybrid Ultra-Capacitors

Lead-Carbon hybrid ultra-capacitors (Pb-C HUCs) are emerging as an alternative to a lead-acid battery, owing to the absence of sulfation, thereby enhancing cycle life and C-rate performances. It delivers more power density (> 10 kW kg-1) and long cycle life (>1,00,000 cycles) compared to lead acid batteries, which enables them to find potential applications in the high surge currents and rapid charge-discharge cycling requirements such as start-stop of electric vehicles, grids, etc.

The main focus of our research is to develop cost-effective anode materials and suitable cathode materials having novel architectures and engineering of the system, which will pave the way to enhance the energy density and power density simultaneously. We are also focussing on fabricating industry level prototype and finding out the shortcomings behind scale-up.

Li/Na ion non-aqueous capacitors

Hybrid Li/Na Ion Capacitors (HICs) bridge the advantages of high-energy LIBs or SIBs along with high-power Electrochemical Capacitors (ECs) by using one highly reversible battery-type electrode (Graphite, Graphene, Transition Metal oxides, etc.) and another high surface area supercapacitor-type electrode (Activated Carbon) in a single unit cell. In order to improve the performance of the HICs, the energy density and cyclability needs to be improved. Our research is focused mostly on two approaches. The 1st approach incorporates modifying both the electrodes i.e. by introducing highly conductive and reversible nanomaterials as anode and high surface area and highly porous materials as cathode through which high energy HICs can be achieved. The 2nd approach involves studying the suitability of ionic liquids as electrolytes which can enhance the voltage window of HICs.

Li-ion Battery Recycling

Over past few decades, LIBs have become a multi-billion-dollar business due to its excessive use in portable electronics devices like smart phones, laptops, personal computers (PCs), cameras and in electric vehicles (EVs). The rapid technological evolution and skyrocket increase in consumer demand result a huge number of discarded LIBs every year. The casual disposal of spent LIBs, burning in air generating poisonous gases (i.e. HF, CO, CO2) and improper storing without precaution impose a serious threat to environment and cloud the possibility of fire mishap. Moreover, geopolitical conflicts around cobalt and lithium mining (the two main metals in commercial LIB electrode) caused a discontinuity in metal supply chain. It may result in unprecedented upsurge in market price of raw metals in near future. Therefore, recycling of LIB is the need-of-the-hour from both economic and environmental point of concern. Our waste-to-wealth approach includes following steps –

1) Development of an eco-friendly route to recover the components of LIB (i.e. cathode, anode, separator, current collector etc.) by hydrometallurgy and chemical route. (2) To fabricate a fresh Li-ion cell using the recovered electrode materials and test the electrochemical performance. (3) Further improvement of electrochemical performance through modification of recovered electrode materials by post-treatment (Chemical and Physical).

Dual-ion Battery

Conventional Lithium-ion battery (LIBs) functions on rocking-chair mechanism. Li-ions rock back and forth between cathode and anode during charge-discharge process. On the other hand, cations and anions originating from the ionic dissociation of electrolyte, intercalate in anode and cathode, respectively during charge and comes back to electrolyte during discharge in case of dual-ion batteries. The dual-ion stoing mechanism yields a high voltage of > 4.5V vs. Li+/Li, utilises carbon as active material at both electrodes, contains no transition metals, and can be considered as one of the sustainable and low-cost alternatives of conventional LIBs. However, isssues like Lithium shortage, electrode surface instability at high voltage, electrolyte decomposition are yet to be mitigated. Our targets are -

1) Investigating the practical viability of large format pouch cells, 2) Improving anion-storing capacity of carbon cathodes, 3) applying protective coating to improve surface instability, 4) finding high voltage electrolyte additives

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