Study of Electrochemical Performance of Lithium and Zinc Metal Anodes for Rechargeable Batteries

Metal anode based batteries, considered the ideal upgrade to Lithium ion batteries in terms of energy density, are currently held back by the non-homogeneous deposition phenomenon that leads to the formation of dendrites that short circuit the cell. The solution to this problem is twofold: while it is important to come up with solutions that mitigate/resist dendrite formation, it is more important to fully understand the deposition phenomena in metal anodes through experiments and theoretical analyses. This study aimed to first understand the deposition mechanism in Zinc and Lithium metal anodes, and then study the feasibility of polymer coatings based on Sulfonated Poly Ether Ether Ketone (SPEEK) as a solution to mitigating the dendrites.The electrochemical performance of Zinc in ZnSO4 electrolyte systems was studiedfor a wide range of current densities and for different operating conditions with the help of operando microscopy and ex-situ SEM. Further, the mechanism of initial Zinc deposition was visualized with the help of in-situ TEM. The origins of the different types of morphology observed at these conditions were explained on the basis of competition between the mass transfer and the kinetics for control over the overall process. Further, a proof of concept was established for the use of SPEEK based coatings on Zinc metal, and the electrochemical performance of polymer coated Zinc electrodes was analyzed.In the case of Lithium, the deposition in carbonate based electrolytes was first studied with the help of operando microscopy for Bare Lithium. Operando microscopy was also carried out to study the influence of the SEI, the separator and a standard polymer coating (PVDF) on Lithium deposition. Further, Lithiated SPEEK was used as a polymer coating on Lithium, and itwas observed that a more even Lithium deposition takes place with the Li-SPEEK coating on Lithium. Slight improvements were observed in the Li+ conductivity of the coating with the addition of TiO2 nanofiller to the polymer. However, performance issues were observed with long term cycling, possibly due to the instability of the polymer coating in carbonate electrolytes over long periods.Electrical Engineering | Sustainable Energy Technolog