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Layered-MnO2 Nanosheet Grown on Nitrogen-Doped Graphene Template as a Composite Cathode for Flexible Solid-State Asymmetric Supercapacitor

Liu, Yongchuan, Miao, Xiaofei, Fang, Jianhui, Zhang, Xiangxin, Chen, Sujing, Li, Wei, Feng, Wendou, Chen, Yuanqiang, Wang, Wei, Zhang, Yining
ACS applied materials 2016 v.8 no.8 pp. 5251-5260
anodes, capacitance, cathodes, electrolytes, electronics, energy density, gels, graphene, industry, nanosheets
Flexible solid-state supercapacitors provide a promising energy-storage alternative for the rapidly growing flexible and wearable electronic industry. Further improving device energy density and developing a cheap flexible current collector are two major challenges in pushing the technology forward. In this work, we synthesize a nitrogen-doped graphene/MnO₂ nanosheet (NGMn) composite by a simple hydrothermal method. Nitrogen-doped graphene acts as a template to induce the growth of layered δ-MnO₂ and improves the electronic conductivity of the composite. The NGMn composite exhibits a large specific capacitance of about 305 F g–¹ at a scan rate of 5 mV s–¹. We also create a cheap and highly conductive flexible current collector using Scotch tape. Flexible solid-state asymmetric supercapacitors are fabricated with NGMn cathode, activated carbon anode, and PVA–LiCl gel electrolyte. The device can achieve a high operation voltage of 1.8 V and exhibits a maximum energy density of 3.5 mWh cm–³ at a power density of 0.019 W cm–³. Moreover, it retains >90% of its initial capacitance after 1500 cycles. Because of its flexibility, high energy density, and good cycle life, NGMn-based flexible solid state asymmetric supercapacitors have great potential for application in next-generation portable and wearable electronics.