Lithium ion batteries adopted in electric vehicles (EVs) and grid energy storage systems require significant increase in energy density (&gt; 750 Wh/L) and reduction of costs to enable widespread commercialization. To address these challenges, R&D efforts have been directed towards (1) testing materials with high energy density and (2) improving electrode design. The latter refers to minimizing the use of inactive materials (e.g., current collectors and separators) and increasing the thickness of electrodes (&gt; 250 µm), which in turn increases energy density and reduces the manufacturing costs. However, performance of the thick electrodes is significantly lower than conventional electrode (i.e., thickness less than 100 µm) because of limited ion and/or electron transports through their porous microstructure. Research groups have demonstrated innovative approaches to control microstructure and enhance ionic transport by forming vertical channels through the thickness of electrode using techniques such as laser-cutting and freeze-casting. But industry adoption of these techniques might be challenging due to their high processing cost based on energy-intensive and time-consuming characteristics. In this study, we use crack formation as a way to create vertical channels in thick LiFePO<sub>4</sub> cathodes through the conventional process. This is achieved by the combination of two water-soluble binders; for example, styrene butadiene rubber (SBR) and polyacrylic acid (PAA) are used for their cracking and binding characteristics respectively. We will present the materials and processing parameters that impacts the physical properties of the thick cathodes, which includes solid loading and surface energy of slurry, binder chemistry, types of carbon networks, and drying conditions. In addition, we will discuss the relationship between cathode microstructures and Li-ion battery cell performances. Although the results discussed are for LiFePO<sub>4</sub> and aqueous systems, this technique can be applicable to different cathode materials and solvent systems by changing the parameters accordingly.

Development of thick cathodes for high-energy lithium-ion batteries

2019 Fall National Meeting

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