Nanoporous materials for improved performance in electrochemical pseudocapacitors and batteries

Nanoporous materials provide exciting opportunities for improving the performance of electrochem. energy-storage devices such as pseudocapacitors and batteries. By producing materials with controlled porosity and high surface area, systems can be optimized for applications where performance is detd. by elec. connectivity, electrolyte access, and surface redox. Here, we first examine porous pseudocapacitors built from nanocrystal building-blocks. The architecture produces fast redox kinetic with a variety of porous metal-oxides materials. Composite systems are also produced that combine efficient elec. cond. with kinetically accessible redox sites. Moreover, in some materials we find that pore flexibility combined with short diffusion lengths produces a phenomena called intercalation pseudocapacitance, where traditional battery-like intercalation become kinetically facile. For high-capacity anodes, we examine porous silicon produce by redn. of template porous silica. Here, the mech. flexibility of nanoporous materials can produce robust cycling behavior, despite the large vol. increase that occurs in silicon upon alloying with lithium.