Cheap High Performance Li-ion Batteries

Li-ion batteries (LIBs) are one of the most used batteries that support modern ITC society, including smartphones and EVs. LIBs are repeatedly charged and discharged by Li-ions passing back and forth between the positive and negative electrodes, with the Li-ion electrolyte acting as a passageway for the ions.

Normally, organic electrolytes such as liquid ethylene carbonate (EC) and their gels have been used as the Li-ion electrolyte due to their voltage resistance and ionic conductivity. However, as liquids and gels are flammable, a switch to safer polymeric solid electrolytes is preferable.

Polymeric solid electrolytes such as polyethylene glycol (PEG) have been proposed as impact-resistant Li-ion electrolytes. However, PEG-based polymer electrolytes crystallize near room temperature, resulting in a significant drop in Li-ion conductivity to around 10-6 S/cm at room temperature. To solve this problem, a research group has invented a new type of polymeric solid electrolyte by combining a porous polymer membrane with several micron pores and a photo-cross-linkable polyethylene glycol PEG-based polymer electrolyte.

This polymeric solid electrolyte not only shows high performance as an electrolyte but is also expected to be effective in deterring the formation of Li dendrites (dendritic crystals), which can cause ignition, due to the inclusion of a porous membrane. Through the realization of safe, high-performance LIBs, this achievement will contribute to the realization of a sustainable energy supply, which is the seventh goal of the SDGs.


How To Hide Hot Objects From Infrared Detection

Hiding an object from heat-sensing cameras could be useful for military and technology applications as well as for research. Efforts to develop such a method have been underway for decades with varying degrees of success. Now, researchers report in ACS Nano that they have fabricated an inexpensive, easy-to-produce film that makes objects completely invisible to infrared detectors.

Several prior systems have been developed to mask the difference in temperature between an object and its surroundings. But each of these alternatives has weaknesses, such as difficulty in making the devices, the need for a power supply, the use of rigid materials or the addition of thick and heavy thermal blankets that can lead to heat buildup. Xuetong Zhang and colleagues wanted to find a better way.

A new, flexible infrared stealth cloak is made of a porous film of Kevlar nanofibers impregnated with polyethylene glycol.

The researchers fabricated an aerogel film made of DuPont™ Kevlar® fibers. By itself, the aerogel turned out to be a good thermal insulator, but the researchers enhanced its capabilities by coating its fibers with polyethylene glycol (PEG) and a protective waterproof layer. PEG stores heat when it melts and releases heat when it solidifies. In simulated sunlight, the composite film covering an object soaked up heat from the sun while only slowly increasing in temperature, just like the surroundings, making the object invisible to a thermal camera.

When the light was turned off to simulate night, the coating gradually surrendered its stored heat energy to match the surroundings. Without the coating, the object heated up or cooled off much faster than its environment, making it visible. In a second type of application, a combined structure consisting of aerogel films and the PEG composite film could hide hot targets from a thermal camera. The researchers say their film performs comparably to other stealth films but is simpler and cheaper to make.