The Need

Conventional electrodes for Li-ion batteries are prepared as thin layers of 70 to 100 microns to meet the power requirements of automotive applications. However, using thin electrodes compromises the energy densities of battery cells due to increasing weight and volume of inactive components such as current collectors and a separator. Increasing electrode thickness beyond 100 microns is challenging due to several factors, and insufficient electrolyte in the bulk of the electrode compromises rate capability. Attention has turned toward developing a method that can control the 3D pore structure of thick electrodes to minimize tortuosity and advance Li-ion electrolyte transport, thereby offering both high power and energy for Li-ion batteries. However, this new electrode design cannot be realized using conventional battery fabrication methods.

The Technology

Researchers at the Ohio State University led by Jung Hyun Kim have developed a technique to create vertical channels and improve the access of electrolytes in bulk of thick electrodes. This technical approach can be realized by producing and controlling the cracks in the electrodes. The size and density of cracks will be designed and controlled. For example, these cracks can run through the entire thickness of the electrode, from the surface to the current collector. As the thickness of the electrode increases, these channels form a pathway for fast ionic transport leading to higher rate capability and homogeneous electrochemical reactions of active materials across the electrodes. By controlling the crack formation and crack density, optimum battery performances can be achieved. We have used a unique combination of binder chemistry, solid loading (amount of dry powders in water), dispersant, types of carbon network, substrate surface modification, and drying temperature and time to control the crack density.

Competitive Advantages

• Crack formation enables easier electrolyte penetration into the bulk of the electrode for enhanced Li ion transport
• Using water as the solvent instead of the NMP solvent being used commercially which is toxic and expensive to dispose
• Binders used are water soluble and do not contain Fluorine
• Electrode thus obtained is stable mechanically, meaning it does not delaminate from the current collector surface

Commercial Applications

• Electric vehicles
• Grid energy storage systems