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Symmetric Sodium-Ion Capacitor Based on Na0.44MnO2 Nanorods for Low-Cost and High-Performance Energy Storage
- Chen, Zhongxue, Yuan, Tianci, Pu, Xiangjun, Yang, Hanxi, Ai, Xinping, Xia, Yongyao, Cao, Yuliang
- ACS applied materials & interfaces 2018 v.10 no.14 pp. 11689-11698
- batteries, capacitance, cost effectiveness, electric power, electric vehicles, electrochemistry, energy, energy density, nanorods, sodium
- Batteries and electrochemical capacitors play very important roles in the portable electronic devices and electric vehicles and have shown promising potential for large-scale energy storage applications. However, batteries or capacitors alone cannot meet the energy and power density requirements because rechargeable batteries have a poor power property, whereas supercapacitors offer limited capacity. Here, a novel symmetric sodium-ion capacitor (NIC) is developed based on low-cost Na₀.₄₄MnO₂ nanorods. The Na₀.₄₄MnO₂ with unique nanoarchitectures and iso-oriented feature offers shortened diffusion path lengths for both electronic and Na⁺ transport and reduces the stress associated with Na⁺ insertion and extraction. Benefiting from these merits, the symmetric device achieves a high power density of 2432.7 W kg–¹, an improved energy density of 27.9 Wh kg–¹, and a capacitance retention of 85.2% over 5000 cycles. Particularly, the symmetric NIC based on Na₀.₄₄MnO₂ permits repeatedly reverse-polarity characteristics, thus simplifying energy management system and greatly enhancing the safety under abuse condition. This cost-effective, high-safety, and high-performance symmetric NIC can balance the energy and power density between batteries and capacitors and serve as an electric power source for future low-maintenance large-scale energy storage systems.