Safer flexible lithium polymer batteries with freezing

August 11, 2017 // By Bill Schweber
A new "ice templating" technique allows formation of a solid, ceramic-based, polymer lithium electrolyte for batteries with straight channels for improved conductivity, energy density, and flexibility.

The dangers associated with lithium-based batteries are well-known to designers. Any inconsistencies in the manufacturing process, mismanagement during charging/discharging cycles, or improperly managed thermal issues can cause fire and even explosion. It comes as no surprise, then, that the search for a safer way to build these high-density, lightweight, electrochemical energy-storage components has attracted significant attention.

 

A four-person team at Columbia University’s Fu Foundation School of Engineering and Applied Science developed a technique that may offer a viable approach to a better electrolyte and, by extension, batteries. (Refs 1 & 2) By controlling the structure of the solid lithium electrolyte, they developed a solid electrolyte that’s safer, non-flammable, and non-toxic, thus avoiding the concerns associated with liquid electrolytes. At the same time, this process may result in a battery that’s bendable to more easily fit the available enclosed space—and one with a longer lifecycle.

Figure 1. In ice templating, a thermoelectric plate is used to cool the solution to an icy state. Then, a vacuum is applied that induces sublimation with a direct phase transition to gaseous state, while the desired ceramic electrolyte material remains. (Source: ACS Publications)

 

Creation of the electrolyte is based on lithium-aluminum-titanium-phosphate Li 1+xAlxTi2-x(PO4)3 nanoparticles (LATP NPs), which are processed with other chemicals to form a ceramic precipitate. Normally, the high conductivity of ceramic fillers is compromised to a large extent by the low conductivity of the resultant matrix, especially when nanoparticles are used. Here, an ice-templating process is employed (Figure 1), in which an aqueous solution with the ceramic particles is cooled from the bottom up (starting at the top of a thermoelectric plate). The cooling rate is controlled by a LabView program.

 

Next, a vacuum is applied to the ice, forcing its direct transition to a gas state (sublimation), while leaving a vertically aligned structure; going directly without an intervening liquid phase minimizes