Printing of Electrochemical Energy Storage Device Components

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Mypati, Sreemannarayana
Materials printing , Electrochemistry , Graphene nanoplatelets , Dispersion stability , Hydrogel electrolytes
Materials printing is a versatile technology used in a wide range of industrial-scale manufacturing processes that require high-precision transfer of materials on different substrates. Despite the numerous studies available for contact/non-contact printing, processing of the printed structures, and development of novel inks, there is still a lack of understanding. In this work, we report on the systematic development of printing and processing techniques and the formulation of stable conductive inks to fabricate the components of energy storage systems. First, we investigate the printing and sintering schemes for multi-layer inkjet printed films on a glass substrate to achieve the desired conductivity and thickness. A semi-empirical model is developed by modifying the well-known Fuchs-Sondheimer Mayadas-Shatzkes model to predict the resistivity of multi-layer nanoparticle metal films. Second, we study different aspects of direct writing of Newtonian liquids, such as jet stability, jet curvature, and equilibrium profile of a printed line on a substrate. This study allows us to determine the distance between the nozzle and substrate and control the print resolution on a substrate. Third, we prepare the stable graphene nanoplatelets (GNP) dispersion in water using a minimal amount of graphene oxide as a dispersant. The stability mechanism, sheet interactions, and the influence of dispersion pH are studied by employing the extended Derjaguin-Landau-Verwey- Overbeek (XDLVO) theory. The rheology of the dispersions is examined and different liquid crystal phases are identified. A dispersion is printed on a flexible substrate and the printed films showed favorable conductivity and adhesion even under bending conditions. Finally, we introduce a novel Zn-Cu battery with and without the use of a separator. The half-cell electrolytes are prepared using polymer hydrogels. The performance of the device is evaluated using electrochemical methods, including cyclic voltammetry, galvanostatic charge-discharge cycles, and electrochemical impedance spectroscopy. We also fabricate and test a printed separator-less battery where the copper electrode and current collectors are prepared using the directwrite printing. Its unique performance without a separator, low-cost materials, and hydrogel electrolytes make it potentially a suitable choice for a wide range of applications as a portable and flexible power source.
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