MicroGrid® Electrode Materials for Advanced Batteries
The lithium ion battery is a widely used rechargeable battery, popular due to its high energy density, high cell voltage, low self-discharge rate and lack of memory issues. The lithium ion battery, however, is also noted for poor cycle life, increased internal resistance with cycles and aging, and safety issues resulting from overheating during charging. Currently, lithium ion batteries, as depicted in Figure 1, are constructed using copper and aluminum foils for current collectors at the cathode and anode in thicknesses on the order of 7-25 microns. Expanded metal mesh used in place of the solid foils provides greater surface area per unit weight of metal in the battery. This results in better adhesion of the electrode layers and higher ion transport rate, thus greater energy density capability. Risk of overheating may also be reduced due to the increased surface area.
Dexmet has developed machines that can expand aluminum and copper foils down to 25 microns (.001") providing an opportunity for battery developers to utilize expanded products in their battery designs and realize the performance enhancements an open area product can provide. By incorporating MicroGrid materials, battery developers can overcome some of the limitations and disadvantages current lithium ion cells including:
- Poor cycle life, especially under high current applications
- Increased internal resistance with cycling and age
- Safety issues if overheated or overcharged
- Battery capacity insufficient for some applications
The development and utilization of expanded metal electrodes in the lithium ion battery can improve the ion transfer rate through the cell. This improved ion transfer rate can lower internal resistance and improve heat transfer thus resulting in lower internal operating temperature and improved charge and discharge rates.