Department of Materials Science and Engineering, Carnegie Mellon University , 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213-3815, United States.
ACS Appl Mater Interfaces. 2017 Jul 19;9(28):23810-23819. doi: 10.1021/acsami.7b06210. Epub 2017 Jul 3.
In recent years, the demand for emerging electronic devices has driven efforts to develop electrochemical capacitors with high power and energy densities that can preserve capacitance under and after recovery from mechanical deformation. We have developed superelastic pseudocapacitors using ∼1.5 mm thick graphene-coated single-walled carbon nanotube (SWCNT) aerogels decorated with manganese oxide (MnO) as freestanding electrodes that retain high volumetric capacitance and electrochemical stability before, under, and after recovery from 50% compression. Graphene-coated SWCNT aerogels are superelastic and fatigue-resistant with high specific surface area and electrical conductivity. Electrodeposition of MnO onto these aerogels does not alter their superelasticity, with full shape recovery even after 10 000 compression-release cycles to 50% strain. Total (utilized) gravimetric capacitances of these aerogels before compression are similar to those under and after recovery from 50% compression over a wide range of scan rates with capacitances reaching 98 (468), 106 (522), and 128 F/g (626 F/g) at a scan rate of 2 mV/s, respectively. These gravimetric capacitances are preserved even after 10 000 compression-release cycles to 50% strain. Further, 50% compression of these aerogels increases the volumetric capacitance from 1.5 to 3.3 F/cm. Before compression, the lifetime performances of these aerogels remain largely stable, with capacitance degrading by only ∼14% over the first 2000 charge-discharge cycles and remains constant for further 8000 cycles. Under 50% compression, capacitance displays a similar trend over 10 000 charge-discharge cycles. After recovery from 10 000 compression-release cycles to 50% strain, the aerogels show slightly greater capacitance loss of ∼28% over the first 2000 charge-discharge cycles and an additional ∼10% loss over the subsequent 8000 charge-discharge cycles. Finally, substantially higher gravimetric capacitance is achieved through greater MnO deposition, facilitated by the large porosity of these aerogels, albeit at a loss of capacitance retention upon compression. These capacitors display the feasibility of coating graphene-coated SWCNT aerogels with various pseudocapacitive materials to create superelastic energy-storage devices.
近年来，对新兴电子设备的需求推动了人们开发具有高功率和能量密度的电化学电容器，以在机械变形恢复前后保持电容。我们使用厚度约为 1.5 毫米的氧化锰（MnO）修饰的石墨烯包覆单壁碳纳米管（SWCNT）气凝胶作为独立电极，开发了超弹性赝电容器，这些电极在 50%压缩前、中、后仍保留高体积电容和电化学稳定性。石墨烯包覆的 SWCNT 气凝胶具有超弹性和抗疲劳性，比表面积大，导电性好。MnO 电沉积到这些气凝胶上不会改变它们的超弹性，即使在经过 10000 次 50%应变的压缩-释放循环后，也能完全恢复形状。这些气凝胶在压缩前的总（利用）重量比电容与在 50%压缩后的比电容相似，在很宽的扫描速率范围内都能达到 98（468）、106（522）和 128 F/g（626 F/g），扫描速率为 2 mV/s。即使在经过 10000 次 50%应变的压缩-释放循环后，这些重量比电容仍能得到保持。此外，这些气凝胶的 50%压缩使体积电容从 1.5 增加到 3.3 F/cm。在压缩前，这些气凝胶的寿命性能基本保持稳定，在最初的 2000 次充放电循环中电容仅衰减约 14%，随后的 8000 次循环中电容保持不变。在 50%压缩下，在 10000 次充放电循环中电容显示出类似的趋势。在经过 10000 次压缩-释放循环至 50%应变的恢复后，气凝胶在最初的 2000 次充放电循环中表现出略高的约 28%的电容损耗，随后的 8000 次充放电循环中又有额外的约 10%的损耗。最后，通过这些气凝胶的大孔隙度，可以实现更大的 MnO 沉积，从而获得更高的重量比电容，但在压缩时会损失电容保持率。这些电容器展示了在石墨烯包覆的 SWCNT 气凝胶上涂覆各种赝电容材料以制造超弹性储能器件的可行性。
