Boosting charge storage in 1D manganese oxide-carbon composite by phosphorus-assisted structural modification for supercapacitor applications

Abstract For electrochemical energy storage, the inevitable oxidation and phase evolution process in many low-valent one-dimensional (1D) transition metal oxides displayed gradually optimized electrochemical characteristics, nevertheless, it is generally sluggish in dynamics. Accelerating this process to achieve efficient energy output remains a significant challenge. Herein, with 1D Mn3O4 as a demo, it was revealed that phosphorus species (P) acted as the active species-like effects, thus robustly accelerating phase evolution process from 1D to two-dimensional (2D) oxides with enhanced charge-storage kinetics. The P-modulated Mn3O4 (P–Mn3O4) presents the optimized surface chemistry properties, unsaturated coordination sites and internal disorders, then the accompanied P leaching in P–Mn3O4 further leads to the formation of low-crystallinity MnO2 with O vacancies and abundant grain boundaries for a highly enhanced capacitive performance. As such, the P–Mn3O4-coupled carbon can reach the areal capacitance of 8743 ​mF ​cm−2 (high mass loading: 44.2 ​mg ​cm−2) at 1 ​mA ​cm−2 after fast phase evolution, together with the high mass and volume capacitances of 198 ​F ​g−1 and 113 ​F ​cm−3, respectively. This P-mediated approach to accelerate phase evolution is universal, evidenced by the extensively studied NiCo-based oxides. This contribution would provide a novel and powerful idea to modulate transition metal hybrids and manipulate active species for efficient energy storage and conversion.