Microdroplet Templating of Uniform Nanostructured Battery Microparticles with Scalable Membrane Emulsification.

Abstract

The manufacture of electrodes with controlled, adjustable nano- to microscale structures can drastically improve the volumetric energy density and transport properties of Li-ion batteries. Assembling microscale secondary particles from nanoparticles is a promising approach, but existing processing methods either result in nonuniform morphologies or have an unfeasibly low throughput. This work leverages controlled emulsification to create uniform battery microparticles from droplet templates. Issues with emulsion stability, drying, and scale-up are addressed, which have previously hindered the implementation of emulsion structuring for battery materials. Here, the templating method is demonstrated using commercial lithium titanate (LTO) nanopowder. Secondary LTO particles with controlled diameter, narrow size distributions, and spherical shape are successfully fabricated. Droplet templated LTO achieved tap-densities twice that of the nanopowder precursor. Microparticle electrodes showed improved electrochemical performance exceeding that of unstructured nanoparticles and of commercial spray-dried microparticles, particularly at high rates. Furthermore, this approach is compositionally flexible, illustrated by coassembling carbon nanotubes and LTO into uniform composite microparticles. LTO/CNT microparticle electrodes achieved >50% higher volumetric energy densities at 0.1C than their unstructured counterparts. Finally, the proposed structuring method is compatible with microfluidic droplet generators, which enable parameter screening, and industrially viable membrane emulsification, which facilitates scaled up microparticle production.