Energy Storage

Academic Projects, Research
  1. Thermocell (In collaboration with Indian Institute of Science, Bengaluru)

For every 3 J of input primary energy, 1 J is converted to electricity and the remaining 2 J are lost as heat to the surroundings. While electronic thermoelectric materials have been developed to harvest high grade waste heat, harvesting low grade waste heat remains a challenge. Two types of thermo-electrochemical cells viz. (a) based on redox reactions (b) based on Soret effect have been studied recently for harvesting low grade waste heat. We are developing methods to harvest ultra-low grade waste heat at temperatures < 60 °C by developing thermocells that utlilize ionic thermoelectrics based on Soret effect.

  1. Bio-templated 3D porous silicon

One emerging market with great potential is the lithium-ion battery (LIB) with silicon (Si) anode or lithium silicon battery. The lithium silicon battery market is expected to grow globally from USD 10 million in 2022 to USD 247 million by 2030, at a CAGR of 48.4% from 2022 to 2030. This stems from their practically achievable energy density, offering a new avenue toward the mass-market adoption of electric vehicles and renewable energy sources. However, both intrinsic and practical challenges remain that are currently the source of intense research by academia and industry. In this project, we have found how some of these challenges can be overcome through the innovative use of nascent, wood-derived materials. For example, we leveraged the unique combination of surface chemistry, fine dimensions, and rod-like shape of cellulose nanocrystals (CNCs) to template a unique porous Si architecture called Si nano-quill (SiNQ) that provided a high, stable capacity and long life in LIB anodes.

  1. High-temperature Li-ion batteries (funded by VIPR-GS, GVSC):

The commercially available Li-ion batteries use organic flammable electrolytes which restrict their operation to moderate temperatures (< 60 °C). In this project, we are exploring new electrolytes based on ionic liquids and solid-state electrolytes for high-temperature applications (up to 100 °C). In addition, we intend to expand the use of Silicon-based anodes for high-temperature rechargeable batteries. Simultaneously, we are developing multi-scale models to study the performance of these high temperature batteries

  1. Transference number:

Battery electrolytes are good ionic and poor electronic conductors. Ionic flux within the electrolyte is equal to the sum of diffusion flux due to concentration gradient and migration flux due to electric field. Cation transference number is the ratio of migration flux of cation to the total migration flux. Most of today’s batteries store energy via cationic redox reactions. So, to enable fast charging batteries, it is desirable to have electrolytes with high ionic conductivity and high cation transference number (which ensures high cation migration flux). Ionic conductivity and transference number depend on the salt-solvent pair and their relative concentrations. In this project, we aim to explore various salt-solvent pairs with concentrations ranging from very dilute to highly concentrated and establish structure-property relationships to determine optimum electrolyte concentration for a high product of transference number and ionic conductivity.

  1. Sodium-Sulfur batteries

Sodium ion batteries are amongst the most popular next generation batteries which have recently been commercialized in Australia. Moreover, earth-abundant and cheap sulfur is an excellent electrode material due to its high theoretical capacity of 1675 mAh/g. In this project, we are developing better electrolytes for sodium sulfur batteries

  1. Niobium Pentoxide based cathodes for batteries

Niobium Pentoxide is a novel intercalation-pseudocapacitance based cathode material which may enable next generation fast charging batteries. Using our in house developed electrolyte with excellent rate capabilities and Niobium pentoxide-based cathodes, our goal is to develop fast charging batteries.

  1. Self-healing binders for Silicon electrodes

Silicon is in the same group as carbon and hence Si is being considered as a next generation electrode to replace graphite in today’s commercial Li ion batteries. However, large volume expansion (300 %) leads to large stress, cracking and frequent rupture and reformation of solid electrolyte interphase (SEI) which leads electrolyte consumption and rapid capacity deterioration. Frequent Si particle cracking also disturbs the connectivity within the electrode thus affecting its electronic conductivity. In this project, we are exploring self-healing binders which may be able to accommodate Si’s expansion and self-heal even if they crack up and thus enhance Si electrode’s performance.

  1. Modeling of Li insertion/extraction in porous-tubular silicon nanoparticles

Our group has recently developed Si nano-quill (SiNQ), a novel type of porous Si that offers much superior electrochemical performance compared to commercial Si nanoparticles. In this project, we are developing Multiphysics models to understand the reasons for the superior performance of SiNQs.

  1. Machine learning to identify structure-property relationships for Si-based electrodes

As Si is amongst the hot materials expected to replace graphite in next-generation batteries, various types of Si nanomaterials, Si-C composites, SiOx based materials have been tried out in the literature. However, there is a lack of clear understanding regarding structure-property relationships for such materials. We plan to develop Machine learning models to unearth structure-property relationships which will enable the rational design of Si-based electrodes.

  1. Biomass for developing high-performance Si@C-based anodes (funded by United Soybean Board)

To date, various approaches have been reported in the literature to prepare silicon-carbon composites for improving the cycling life of Si-based anodes. However, most reported techniques are neither scalable nor environmentally friendly. In this project, we established a low-cost, green, and scalable technique to create cloud-type carbon protection for Si nanoparticles using soybean products. The Si-embedded carbon cloud is found to be an effective Si@C composite for accommodating the volume changes of Si and forming a stable SEI layer to significantly prolong the cycling life of Si-based anodes.

  1. Commercial paper-based solid-state electrolyte

Paper, a sustainable natural product based on renewable raw materials (mainly wood), has the potential for a wide variety of applications. Following the recent discovery of the potential of cellulose in conducting Li ions, we explore a design strategy for paper-based solid-state ionic conductors. Our approach is based on expanding the intermolecular polymeric structure of cellulose fibers in the paper, which could lead to high ionic conductivity.

  1. Natural wood for high-areal-capacity Li-S batteries

Sulfurized polyacrylonitrile (SPAN) is an alternative sulfur cathode material for practical application in Li–S batteries because of its ability to mitigate the shuttle of Li polysulfides in comparison with elemental S cathodes. Achieving high SPAN areal loading on commercial metallic current collectors (e.g., aluminum foil) without compromising specific capacity and cycling stability is practically unrealistic. As widely abundant biomass, natural wood has a unique hierarchical cellular structure. Inspired by such an efficient transport system with interconnected pathways, we developed a current-collector-free, SPAN-impregnated cathode from natural balsa wood. The environmentally friendly, low-cost solution described in this study opens doors for high-areal-capacity Li-S batteries (>5 mAh cm-2) for practical energy storage applications.