Block-Copolymer-Architected Materials in Electrochemical Energy Storage

The multiscale architecture of electrochemical energy storage (EES) materials critically impacts device performance, including energy, power, and durability. The pore space of nano- to macrostructured electrodes determines mass transport within the electrolyte and defines the effective energy density. The dimensions of the active charge-storing materials can increase stability during cycling by accommodating strains from electrochemical-mechanical coupling while also defining surface area that increases capacitive charge storage, decreases charge-transfer resistance, but also leads to low efficiency and degradation from interfacial reactions. Thus, elucidating and developing a fundamental understanding of these correlations requires materials with precisely tunable nanoscale architectures. Herein, approaches that take advantage of the nanoscale control offered by block copolymer (BCP) self-assembly are reviewed and insights gained from associated nanoscale phenomena observed in EES are highlighted. Systematic studies that use custom-tailored BCPs to reveal fundamental nanostructure-property-performance relationships are emphasized. Importantly, most reports of nanostructured materials utilize low loadings and thin electrodes and results represent mass transfer limitations at the particle scale. However, as cell-level performance involves mass transport over 10-100s of micrometers, recently emerging BCP-based processes are further highlighted, leading to hierarchical meso/macroporous materials needed for creating multiscale structure-performance relationships and next-generation energy storage material architectures.