1. Field of the Invention
Embodiments of the present invention generally relate to lithium-ion batteries and battery cell components, and more specifically, to a system and method for fabricating such batteries and battery cell components using mechanical and deposition processes that form three-dimensional porous structures.
2. Description of the Related Art
High-capacity energy storage devices, such as lithium-ion (Li-ion) batteries, are used in a growing number of applications, including portable electronics, medical, transportation, grid-connected large energy storage, renewable energy storage, and uninterruptible power supply (UPS).
One method for manufacturing Li-ion battery cell electrodes is principally based on slit coating of viscous powder slurry mixtures of cathodically or anodically active material onto a conductive current collector followed by prolonged heating to form a dried cast sheet and prevent cracking. The thickness of the electrode after drying which evaporates the solvents is finally determined by compression or calendering which adjusts the density and porosity of the final layer. Slit coating of viscous slurries is a highly developed manufacturing technology which is very dependent on the formulation, formation, and homogenization of the slurry. The formed active layer is sensitive to the rate and thermal details of the drying process.
Because the dried cast sheet must adhere well to the metal current collector, the mixture typically includes a binder which promotes adhesion. Binding is further augmented by the compression process which adjusts the density of the active sheet and also embeds some of the bound particles into the metal current collector.
For most energy storage applications, the charge time and energy capacity of energy storage devices are important parameters. In addition, the size, weight, and/or expense of such energy storage devices are significant specifications.
In order to make higher loading batteries, a thicker layer of active material is required, but as the active material layer gets thicker, it becomes more difficult for Li-ions to travel through the film and the overall use of the active material becomes less efficient.
Accordingly, there is a need in the art for faster charging, higher capacity energy storage devices that are smaller, lighter, and can be more cost effectively manufactured at a high production rate.