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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.