Ammonium Folate‐Reinforced Self‐Assembly of Gelatin into N/B/O‐Enriched Hierarchical Porous Carbons with Loosely Layered Structure for Anti‐Freezing Flexible Supercapacitors

Abstract Heteroatom‐doped layered porous carbons are recently regarded as promising electrode materials for high energy density supercapacitors because they can integrate high‐level heteroatom‐doping and layered nano‐space together to provide huge pseudocapacitive reaction areas and accelerate ion diffusion/transport. Herein, an innovative strategy is reported to prepare N/B/O co‐doped layered porous carbons via ammonium folate‐reinforced self‐assembly of gelatin and boric acid followed by carbonization. Biomass‐derived ammonium folate not only acts as an N‐riched precursor but also can fasten in the process of self‐assembly via boric acid‐assisted electrostatic adsorption and hydrogen bonding to promote the formation of stable 3D cross‐linked networks, resulting in the obtained N/B/O co‐doped layered porous carbon (BNLC‐850) has a large specific surface area (1822 m 2 g −1 ), hierarchical porous structure and super‐high heteroatom contents (N, 12.65; B, 5.67; and O, 13.84 at.%). The BNLC‐850 achieves an ultrahigh specific capacitance of 525.2 F g −1 in the alkaline electrolyte at 0.5 A g −1 , meanwhile, DFT calculations reveal that the high‐level N/B/O‐doping can effectively weaken the adsorption barriers of K‐ions. Moreover, the BNLC‐850 assembles anti‐freezing flexible solid‐state supercapacitors in MPEI‐TF‐IL gel polymer electrolyte deliver a high energy density of 41.2 Wh kg −1 , excellent flexibility, and long cycle‐life at −20 °C.