Integrated nanocomposite of LiMn₂O₄/graphene/carbon nanotubes with pseudocapacitive properties as superior cathode for aqueous hybrid capacitors

Aqueous rechargeable Li-ion hybrid supercapacitors are attracting increasing attention owing to their intrinsic advantages compared with nonaqueous counterpart and the combination of high energy and power densities in an individual device. However, the lack of satisfactory battery-type cathode materials with fast lithium ion storage limits the overall performance. Herein, we report a composite structure by incorporating LiMn₂O₄ nanoparticles in graphene/carbon nanotubes network (LiMn₂O₄@CNTs@graphene) as superior cathode for aqueous hybrid capacitors. LiMn₂O₄@CNTs@graphene nanocomposite shows high capacitance with ultrafast lithium diffusion, which is mainly boosted by pseudocapacitive behavior, making it a potential candidate for hybrid supercapacitors. Hybrid devices assembled with LiMn₂O₄@CNTs@graphene cathode and N/S co-doped activated carbon anode exhibit an optimized overall performance with a high energy density of 62.77 Wh kg⁻¹ and high power density of 2967.96 W kg⁻¹ as well as good cycling performance with the capacitance retention of 90.8% after 5000 cycles.