A high-density 3D sintered cathode is proposed to increase the energy density of microbattery for wearable devices. The 3D electrode geometry is designed using high-speed simulation consisting of 2D model transformation. In this paper, we present 2D transformed modeling from 3D geometry approximating a 3D unit cell. The objectives of simulation is to find an optimal structure by analyzing the relationship between electrode structure and rate capability for high energy density microbattery.
The structure of 3D sintered cathode features vertical holes, horizontal channels, and plates. Vertical holes are placed like a honeycomb using laser drilling. Horizontal channels are thin and low-density active material layer to help transporting lithium-ions in liquid electrolytes. Plates are thick and high-density active material layer placed between horizontal channels. The active material in this study is Lithium Cobalt Oxide (LiCoO₂), and the low-density and high-density active material layers are produced by using different composite green sheets through a sintering process.
Model validation is performed by comparing the results of charge and discharge voltage profiles obtained from experiments and simulations. The lithium-ion diffusion coefficient according to x of Li_xCoO₂ is adjusted to make a similar voltage profile in both results. After validation, simulation is performed to analyze the rate capability by changing the structure of the 3D sintered cathode such as hole pitch, thickness of plate and channel, etc. The simulation results show the relationship between rate capability and the 3D structure of the sintered cathode.
In this design methodology, we found the optimal structure of a 3D sintered cathode, which has an energy density of 150% higher than that of a conventional jelly-roll type battery. At the same time, the rate capability is more than 90%, defined as the ratio of discharging capacity at 1.0C to discharging capacity at 0.2C. Finally, the feasibility of the proposed design methodology shows that the experimental results of rate capability and energy density are almost consistent with the simulation results.

Jin S. Heo

Principal Researcher, Samsung Electronics, SAIT

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