3D interconnected macrostructure based on nano-scale pyroprotein units for energy storage

A porous carbon monolith with a well-defined internal nanostructure consisting of highly redox-active materials has potential as an electrode in energy storage applications. In this study, 3D interconnected pyroprotein macrostructures (3D-IPMs) were fabricated from silk proteins using a simple templated sol-gel method and subsequently heated with potassium hydroxide. The resulting 3D-IPMs, which were further optimized, had high nitrogen concentrations (C/N ratio: 11.4), good electrical conductivities of ∼2.8 S cm⁻¹, and well-developed pore structures. The 3D-IPMs showed reversible storage capacities of ∼680 mA h g⁻¹ at 0.1 A g⁻¹ via a pseudocapacitive Li ion storage mechanism in the anodic potential range. Even when a 300-fold larger current rate was used, a reversible capacity of ∼230 mA h g⁻¹ was maintained. In addition, the 3D-IPMs exhibited remarkable stability over the course of 1,000 cycles. The practicability of 3D-IPM-based energy storage devices was demonstrated by assembling full cells with a well-known cathode material. The full cell devices delivered a specific energy of 142.7 W h kg⁻¹ at 190 W kg⁻¹ and specific power of 23,850 W kg⁻¹ at 48.1 W h kg⁻¹. In addition, their performance remained stable across many cycles.