Air Force

Solid electrolyte rechargeable lithium battery

Prototype solid electrolyte rechargeable lithium battery with high energy capacity that improves safety over liquid electrolyte lithium battery systems

Energy
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Figure 1: Initial discharge profile of an all solid-state cell based on this new material

The U.S. Air Force Research Laboratory Aerospace Systems Directorate (AFRL RQ) has developed and patented a new class of solid-state electrolyte (SSE) for secondary lithium batteries. The goal of this research is to achieve higher capacity, safer battery technology.

Recently the Air Force fabricated and tested its first fully functional cell, analogous to a coin cell, based on this material – whose backbone is a large unsaturated aromatic molecule. Further testing and characterization are underway. The initial testing strongly indicates that the new materials are capable of delivering and maintaining high energy storage capacity over multiple charge/discharge cycles. Additional patentable discoveries have been made and more are anticipated as battery performance is further optimized.

Preliminary testing coupled with theoretical calculations show that a specific capacity in excess of 1000 mAh/g is possible with a simple cell configuration comprised of a lithium metal anode and other cell components based on this new family of materials. Figure 1 shows the initial discharge profile of an all-solid-state cell at 100º C using a constant current of 50 µA/cm2.

With a formulation that is far from optimized, the specific capacity to this initial test is a respectable ~ 126 mAh/g based on the active weight of the prototype cathode; it is very encouraging that the cell is robust, stable, and currently being cycled at 100º C. The new technology will eliminate safety concerns posed by liquid electrolyte lithium cells. The batteries do not contain corrosive liquids reducing concerns about battery puncture or rupture. Also, thermal runaway is not possible with this solid-state cell configuration and the key compositions are free of oxygen, thereby eliminating combustion due to overheating conditions.

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