LITHIUM-SULFUR AND SODIUM-SULFUR BATTERY CATHODES

Unmet Need
Rechargeable lithium batteries are found in many devices on the market today such as electric vehicles (Nissan Leaf, Tesla cars), Tesla Powerpacks for home electricity storage, and most laptops and cell phones. However, as portable electronics get smaller, the batteries fueling these devices also need to get smaller while still supplying the same or better lifetime per charge. Alternatively, as electric vehicles become more mainstream, they will have to improve upon the range they can travel on a full battery charge (currently ~240 miles). Lithium batteries come in two flavors (lithium polymer and lithium ion) based on their electrolyte and have an energy density of about 150-250 Wh/kg. Lithium-sulfur batteries have a much higher theoretical energy density (up to 2600 Wh/kg), however the technology is not mature. The highest energy density for an available lithium-sulfur battery is at most 500 Wh/kg. One downside of lithium-sulfur batteries is a low cycle life, meaning that they lose their capacity after only a few charge/discharge cycles, due to dissolution of polysulfide intermediates in the electrolyte. While there are many alternative battery technologies to lithium batteries, they each come with their set of pros and cons. Thus, there is need in art for battery technology with higher energy density, lighter weight and better cycle life.
 
Technology Overview
Johns Hopkins researchers have incorporated metal-organic frameworks with defects into the electrode of the battery. These defects help retain the sulfur molecules in the electrode which retains the capacity of the battery. These defects have also been functionalized to further improve the capacity of the battery. These batteries have been shown to have an energy density over 3x the current lithium-sulfur batteries on the market, and ~5-6x better than other lithium batteries currently on the market. These batteries also display a 33% higher energy density than the equivalent battery with defect free metal-organic frameworks.


 
Stage of Development
The inventors have made and tested these batteries as coin cell batteries, which are about the size of a nickel. These batteries have been tested up to 20 cycles and show a retention in capacity compared to other lithium-sulfur batteries.
 
 
Publications
None at this time.

 

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