Department of Materials Science and Engineering, KAIST, Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS) , Daejeon 305-701, Republic of Korea.
ACS Appl Mater Interfaces. 2015 Jan 28;7(3):1899-906. doi: 10.1021/am507673j. Epub 2015 Jan 13.
Operating voltage enhancement is an effective route for high energy density supercapacitors. Unfortunately, widely used activated carbon electrode generally suffers from poor electrochemical stability over 2.5 V. Here we present atomic layer deposition (ALD) encapsulation of activated carbons for high voltage stable supercapacitors. Two-nanometer-thick Al2O3 dielectric layers are conformally coated at activated carbon surface by ALD, well-maintaining microporous morphology. Resultant electrodes exhibit excellent stability at 3 V operation with 39% energy density enhancement from 2.5 V operation. Because of the protection of surface functional groups and reduction of electrolyte degradation, 74% of initial voltage was maintained 50 h after full charge, and 88% of capacitance was retained after 5000 cycles at 70 °C accelerated test, which correspond to 31 and 17% improvements from bare activated carbon, respectively. This ALD-based surface modification offers a general method to enhance electrochemical stability of carbon materials for diverse energy and environmental applications.
工作电压提升是实现高能量密度超级电容器的有效途径。然而，广泛应用的活性炭电极在 2.5 V 以上通常表现出较差的电化学稳定性。在这里，我们提出了一种原子层沉积（ALD）封装活性炭的方法，用于构建高压稳定超级电容器。ALD 在活性炭表面包覆了 2nm 厚的 Al2O3 介电层，很好地保持了微孔形态。结果表明，在 3 V 下工作时，电极具有优异的稳定性，与在 2.5 V 下工作相比，能量密度提高了 39%。由于表面官能团的保护和电解质降解的减少，在完全充电后 50 小时，仍保持初始电压的 74%，在 70°C 加速测试 5000 次循环后，电容保持率为 88%，分别比裸活性炭提高了 31%和 17%。这种基于 ALD 的表面改性方法为提高碳材料在各种能源和环境应用中的电化学稳定性提供了一种通用方法。
