Prakhar Verma

PhD Research

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The area of my doctoral research work is 'Computational modelling and experimental study of dendrite growth in electrochemical cell'. The computational modelling part includes developing 1D and 2D models that can predict the morphology of electrodeposition. The non-uniform deposition of ionic species at anode leads to the formation of dendrites-the major challenge in the development of rechargeable metal batteries. The effect of overall dendrite growth on cell operations will be modelled. The safety limit and optimized performance conditions will also be determined. Thus, this research will strive to combine the basic mechanism of dendrite formation and its effect on long-term cycling. Further, the model will be validated by experiments, and finally, a dendrite suppression methodology will be proposed.

1. 1D and 2D Electrochemical Cell Model: A Lead-Acid electrochemical cell was modelled using dilute solution theory. The governing equations used were the material balance equation for the concentration of ionic species and the Nernst-Planck equation for the ionic potential. The coupled partial differential equations (PDEs) were solved for the 1D solid-electrode and electrolyte system. Finite difference and finite volume codes were developed using MATLAB, whereas the finite element method was implemented using COMSOL Multiphysics. The simulations were carried out using all three techniques for charging and discharging. The concentration distribution of ionic species, ionic potential and cell potential were calculated. The results obtained from these methods were studied comparatively. The effect of adaptive grid spacing was also implemented to increase the computational efficiency of the program. The results showed a good convergence and had no significant dependence on the number of node points. This model was later expanded to work with 2D systems.

2. Pseudo 2 Dimensional (P2D) Electrochemical Model: A Lithium Metal Battery (LMB) model was developed using the Doyle Fuller Newman theory (DFN Model). 1D system of Lithium/polymer cell sandwich comprising of Lithium foil as anode, solid polymer electrolyte and composite cathode was considered. The simulation was carried out under galvanostatic conditions with a current density of 10 A/m2. The spatial ionic concentration evolution, electrolyte potential, and Li intercalation were studied. These results were benchmarked with the original Doyle model and were found to be in close agreement.

3. Phase-Field Modelling of Dendrite Growth: Dendrite growth at the electrode-electrolyte interface was studied using a phase-field model. This modelling technique helps in understanding the phase transition and microstructural evolution of electrodeposited crystals. The temporal evolution of these crystals under various conditions such as concentration of ionic species, applied overpotential and morphology of electrode surface is to be modelled. The model to predict the effect of organizer molecules on dendrite growth is under development. This model is based on existing standard phase-field equations along with classical nucleation and growth theory.