High Voltage Asymmetric Supercapacitors Developed by Engineering Electrode Work Functions,ACS Energy Letters

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High Voltage Asymmetric Supercapacitors Developed by Engineering Electrode Work Functions
ACS Energy Letters ( IF 19.3 ) Pub Date : 2021-09-16 , DOI: 10.1021/acsenergylett.1c01484
Kowsik Sambath Kumar _{1,

2} , Deepak Pandey _{1,

2} , Jayan Thomas _{1,

2,

3}

Affiliation

Currently, a major constraint in employing supercapacitors as a solitary energy storage device in applications like electric vehicles is their low energy density. In aqueous asymmetric supercapacitors, the energy density is limited by the voltage window, which is governed by the electrode’s work functions. Here, the preinsertion of different metal cations such as Li⁺, Na⁺, and K⁺ ions into manganese dioxide (MnO₂) to tune the electrode’s work function is demonstrated. Sodium-doped MnO₂ (NaMnO₂) exhibited a lower work function than Li⁺ and K⁺ preinserted electrodes. This lowering of the work function leads to a higher voltage window. The work function tuned NaMnO₂ is coupled with a high-work-function negative electrode material, molybdenum oxide (MoO₂), to fabricate a 2.5 V aqueous asymmetric supercapacitor. The supercapacitor delivered a maximum energy density of 78 Wh kg^–1, a power density of 4.6 kW kg^–1, and capacitance retention of 98.6% after 5000 cycles. This work brings new insights into the engineering of electrode’s work function for developing high-voltage and high-energy supercapacitors.

中文翻译：

通过工程电极功函数开发的高压非对称超级电容器

目前，在电动汽车等应用中采用超级电容器作为单独储能装置的主要限制是它们的低能量密度。在水性非对称超级电容器中，能量密度受电压窗口的限制，而电压窗口由电极的功函数控制。在这里，演示了将不同的金属阳离子（如 Li ⁺、Na ⁺和 K ⁺离子）预插入到二氧化锰 (MnO ₂ ) 中以调整电极的功函数。钠掺杂的 MnO ₂ (NaMnO ₂ ) 表现出低于 Li ⁺和 K ^{+ 的}功函数预插入电极。功函数的这种降低导致更高的电压窗口。功函数调谐的 NaMnO ₂与高功函数负极材料氧化钼 (MoO ₂ ) 相结合，以制造 2.5 V 水性非对称超级电容器。超级电容器的最大能量密度为 78 Wh kg ^–1，功率密度为 4.6 kW kg ^–1，5000 次循环后电容保持率为 98.6%。这项工作为开发高电压和高能量超级电容器的电极功函数工程带来了新的见解。

更新日期：2021-10-08

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