Abstract Three-dimensional reduced graphene oxide (rGO) based hydrogel or sponges have received increasing attention in recent years. High porosity combined with mechanical durability in graphene based sponges is in high demand in energy storage field. However, pure rGO sponges are generally delicate and fragile, which is hard to handle and process. Moreover, low package density of graphene based material leads to low volumetric energy density, which limits its further commercial application, although it has already achieved high gravimetric energy storage in supercapacitor. Herein, we came up with a method to improve the volumetric capacity by simply pressing fluffy rGO sponge into dense film. Self-assembly of rGO and polymer-assisted cross-linking are cooperated to fabricate the rGO based hydrogel with higher plastic property. Poly acrylic acid (PAA) could enhance the mechanical integrity of the rGO sponges, thus could be pressed into freestanding integral film. In this case, addition of carbon nanotube (CNT) could enhance the conductivity and prevent the sharp decline of surface area by pi-pi interaction between CNT and rGO sheets preventing the restacking problem. Unlike the rGO sponges which cannot be pressed, the compressed rGO-CNT-PAA film still maintains intensive porous structure with the trace of squeezing in microstructure and achieves gravimetric and volumetric capacity of 140 mAh g−1 and 73 mAh cm−3.

中文翻译：

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锂离子电容器用高体积电容塑料三维纳米碳-聚丙烯酸海绵

摘要 近年来，基于三维还原氧化石墨烯 (rGO) 的水凝胶或海绵受到越来越多的关注。石墨烯基海绵的高孔隙率与机械耐久性相结合，在储能领域有很高的需求。然而，纯 rGO 海绵通常脆弱易碎，难以处理和加工。此外，石墨烯基材料的低封装密度导致其体积能量密度低，这限制了其进一步的商业应用，尽管它已经在超级电容器中实现了高重力储能。在这里，我们想出了一种通过简单地将蓬松的 rGO 海绵压成致密薄膜来提高体积容量的方法。rGO 的自组装和聚合物辅助的交联协同制备具有更高塑性的 rGO 基水凝胶。聚丙烯酸 (PAA) 可以增强 rGO 海绵的机械完整性，因此可以压制成独立的整体薄膜。在这种情况下，添加碳纳米管 (CNT) 可以通过 CNT 和 rGO 片之间的 pi-pi 相互作用提高导电性并防止表面积急剧下降，从而防止重新堆叠问题。与无法压制的 rGO 海绵不同，压缩后的 rGO-CNT-PAA 薄膜仍保持密集的多孔结构，在微观结构上有挤压痕迹，并实现了 140 mAh g-1 和 73 mAh cm-3 的重量和体积容量。添加碳纳米管 (CNT) 可以通过 CNT 和 rGO 片之间的 pi-pi 相互作用提高导电性并防止表面积急剧下降，从而防止重新堆叠问题。与无法压制的 rGO 海绵不同，压缩后的 rGO-CNT-PAA 薄膜仍保持密集的多孔结构，在微观结构上有挤压痕迹，并实现了 140 mAh g-1 和 73 mAh cm-3 的重量和体积容量。添加碳纳米管 (CNT) 可以通过 CNT 和 rGO 片之间的 pi-pi 相互作用提高导电性并防止表面积急剧下降，从而防止重新堆叠问题。与无法压制的 rGO 海绵不同，压缩后的 rGO-CNT-PAA 薄膜仍保持密集的多孔结构，在微观结构上有挤压痕迹，并实现了 140 mAh g-1 和 73 mAh cm-3 的重量和体积容量。