Interfacial Engineering and a Low-Crystalline Strategy for High-Performance Supercapacitor Negative Electrodes: Fe 2 P 2 O 7 Nanoplates Anchored on N/P Co-doped Graphene Nanotubes.

Developing novel hybrid negative electrode materials with high specific capacity, rate capacitance, and long-term cycle stability is a key factor for pushing large-scale application of supercapacitors. However, construction of robust interfaces and low-crystalline active materials plays a crucial role in realizing the target. In this paper, a one-step phosphorization approach was employed to make low-crystalline Fe 2 P 2 O 7 nanoplates closely bonded to N/P-co-doped graphene nanotubes (N/P-GNTs@b-Fe 2 P 2 O 7 ) through interfacial chemical bonding. The N and P heteroatoms as substitutions for C in GNT skeletons can introduce rich electronic centers, which induces Fe 2 P 2 O 7 to fix the surface of N/P-GNTs through Fe-N and Fe-P bonds as confirmed by the characterizations. Moreover, the low-crystalline active materials own a disordered internal structure and numerous defects, which not only endows with excellent conductivity but also provides many active sites for redox reactions. Benefiting from the synergistic effects, the prepared N/P-GNTs@b-Fe 2 P 2 O 7 can not only deliver a high capacity of 257 mA h g -1 (927 F g -1 ) at 1 A g -1 but also present an excellent rate capability of 184 mA h g -1 (665 F g -1 ) at 50 A g -1 and outstanding cycle stability (∼90.6% capacity retention over 40,000 cycles). Furthermore, an asymmetric supercapacitor was assembled using the obtained N/P-GNTs@b-Fe 2 P 2 O 7 as electrode materials, which can present the energy density as high as 83.3 W h kg -1 at 791 W kg -1 and long-term durability. Therefore, this strategy not only offers an effective pathway for achieving high-performance negative electrode materials but also lays a foundation for further industrialization.