Recently, there has been a push toward all solid-state batteries to eliminate flammability issues in portable electronics. Several solid conductors exist and broadly fall into two material categories: (1) polymers and (2) ceramics. Polymer ionic conductors are advantageous because they can be manufactured easily into thin films, are mechanically robust, and flexible. However, polymer conductors have lower ionic conductivities when compared with their ceramic counterpart. Ceramic conductors boast outstanding ionic conductivities (>10 mS/cm) but processing the electrolyte into thin films (50-100 micrometer) for efficient device integration still remains a challenge because of the brittle nature of the ceramic. There have been a few studies which have investigated a hybrid approach which combines the polymer and ceramic into a composite electrolyte to achieve both processing and performance requirements. A grand challenge with solid state batteries, independent of ion conductor composition, is transport at interfaces. There are both intrinsic interfaces formed within a material by grain, vacancies, and material junctions (composite). Furthermore, there are extrinsic interfaces formed when integrated with an electrode. There is a significant need to understand how we can tailor these interfaces during processing using state of the art manufacturing techniques.

Slot die coaters are extensively used in roll-to-roll processing industrially[2]. However, some challenges remain that deter realization of the full potential of this technique for scalable manufacturing of functional materials. Some of these challenges are multi-material coating ability, active control and feedback, coating intermittently and enhancing resolution among others[3]. Herein, we study a system of colloidal inks with a custom-made benchtop slot-die system. Initial results have shown that the nano-scale interactions in the ink phase impact the macroscopic ink properties and the coating structure [4,5]. This work focuses on demonstrating functional gradation capabilities in slot-die coating system through a novel multi-layer design and understanding how pathways can be engineered for efficient transport.

[1] Hatzell, Kelsey B., et al. "Understanding inks for porous-electrode formation." Journal of Materials Chemistry A 5.39 (2017): 20527-20533. [2] Department of Energy. Roll to Roll Processing Technology Assessment. Technical report, 2015. [3] Corie L Cobb and Christine C Ho. Additive Manufacturing: Rethinking Battery Design. Interface, 3–6, 2016 [4] Dixit, Marm B., et al. "Catalyst Layer Ink Interactions That Affect Coatability." Journal of The Electrochemical Society165.5 (2018): F264-F271. [5] Dixit, Marm, and Kelsey B. Hatzell. "Understanding Binary Interactions and Aging Effects in Catalyst Layer Inks for Controlled Manufacturing." ECS Transactions 80.8 (2017): 301-307.