Researchers at the Idaho National Engineering and Environmental Laboratory are trying to build lithium batteries that can sit for months without recharging.
To do this, they are studying how lithium ions move through the translucent polymer membrane in their rechargeable lithium cells. The flexible membrane lets positively charged lithium ions pass through to create electrical current, but blocks negatively charged electrons. This keeps the battery from running down while it sits on the shelf.
INEEL researchers realized their membrane didn't let through enough lithium ions to produce adequate power. Analysis of the membrane with nuclear magnetic resonance revealed that lithium ions travel along alternating phosphorus and nitrogen molecules, or the "backbone" of the membrane, which has oxygen-laden "ribs" attached to the phosphorus molecules. Further tests showed that lithium ions are most mobile when interacting with nitrogen.
Researchers are developing new membranes to increase lithium-ion flow and are optimistic their design will ultimately change the battery industry. They claim their polymer membrane will prevent battery run down so well that batteries could sit unused up to 500 months between charges. And, because the membrane is a flexible solid, it can be molded into any shape, opening up new applications for batteries. The temperature-tolerant membrane could also solve portable power problems in the frigid cold of space.