Functional Hierarchical Nano/Micro-Architectures from Liquid-Polymer-Particle Aggregation Induced by Phase Separation

Control over multi-scale structural features, including precise nanoparticle arrangement and the embedded meso- and macropores are of paramount importance for electrodes used in mass-transfer limited devices such as batteries, fuel cells and carbon capture systems. To meet the demand for application-tailored electrode architectures, we have developed a facile, scalable, and bottom-up approach, termed Hybrid Inorganic Phase Inversion (HIPI). HIPI enables us to create monolithic materials with controlled hierarchical structures of nano- and micro-particles with channel-like micron-scale pores and tunable nanoporosity by exploiting the driving forces of liquid-polymer phase separation, gelation, and aggregation. HIPI is a material-agnostic self-assembly process which reaches across all four classes of materials, resulting in free-standing hierarchically porous ceramics, metals, polymers and composites.<br/><br/>Despite HIPI being a fast non-equilibrium aggregation process, we have developed rational design criteria to gain precise control over the multi-scale porosity and architecture. To this end, we tune the density of the nucleating phase of the particle-polymer-liquid suspension using the thermodynamics of phase separation to control and tailor the pore density on the micron scale. Further, by adjusting the relative kinetics of solidification and phase separation we control the shape of the micron scale pores from cylindrical to graded to conical. Lastly, exploiting transient gel states allows us to dial in the degree of nanoporosity. The range of multi-scale architectural features both accessible and tunable put HIPI at the forefront of fabrication concepts to enable scalable designer electrodes.