New process can be used to build faster, safer solid-state electrolytes for batteries in portable devices, cars and airplanes
UCF researchers have developed a low-cost method for processing two-dimensional (2-D) covalent organic frameworks (COFs) that can safely be used as electrolytes in solid-state, rechargeable lithium-ion (Li-ion) batteries. The new method offers a better alternative to producing liquid electrolyte-based Li-ion batteries (that can combust upon battery failure) and to ceramic materials that require costly production methods.
COFs usually crystallize as insoluble powders, and their processing for devices, such as batteries, has been thought to be limited. Yet, the 2-D variants of COFs exhibit several desirable and unique features. For example, the length and relative orientation of their linking groups determine a lattice structure, in contrast to the unpredictable packing of traditional organic semiconductors. Also, their permanent porosity provides a continuous, high surface-area interface for added functionality. Moreover, 2-D COFs contain pores with cylindrical and unidirectional shape that can be decorated with functional groups that are chemically attached to the building blocks before the COF synthesis.
With the new method, 2-D COF powders are impregnated with lithium salts and then mechanically pressed along a uniaxial direction into shaped objects, such as pellets. The result produces materials that are crystallographically aligned with a high degree of anisotropic ordering, enabling fast Li-ion conductivity and dynamics within the COFs and exceptional electrochemical stability to lithium. The method can be applied to different COFs with diverse functionalities (for example, boronate, boroxine, β-ketoenamine and triazine) and different symmetries (such as hexagonal, trigonal, tetragonal or monoclinic symmetry).
- Enables safer, cheaper production of solid-state electrolytes in batteries
- Lithium batteries in portable devices, cars and airplanes
- Energy and gas storage, adsorption, optoelectricity, catalysis, chemical and gas separation
- Photovoltaic and electrochemical devices