Progress in surface and interlayer distance modulated 2D Ti3C2 MXenes for potential flexible supercapacitors: A review

Over the past decade, rapid advancements in the approach of morphological evolution of two-dimensional (2D) Ti3C2 MXenes (multilayer, few-layer, monolayer, nanoparticles, and quantum dots) allowed for the development of energy storage devices. Specifically, multilayer Ti3C2 MXene is shown as an excellent electrode for practical application in flexible supercapacitors. But, critical restacking of nanosheets deteriorates the ion/electron diffusion and exposure of active surface sites during the device performance. Aiming to alleviate the restacking behavior, researchers adopted various intelligences of nanostructures (0D, 1D, and 2D), conductive polymers, and metal ions intercalation into Ti3C2 nanosheets, which establish the concept of activated energy storage and ion/electron diffusion. Thus, we systematically evaluate the recent advancements in rich functionalities of intercalation effect to extend the energy storage device performance of Ti3C2 MXene. On the other hand, we emphasize the sustainability of 2D Ti3C2 MXene nanosheets as one-dimensional (1D) fibers even for meters long formation without experiencing any morphological damage after bent, twist, and knot conditions. These modeling features can integrate into textiles. Thus, this review suggests the extensive role of 2D Ti3C2 MXene nanosheets in next-generation flexible energy storage devices under intrinsic mechanical and electrochemical stability. In conclusion, successive intercalation and enlarged interlayer space establish recommendations for stimulation of surface-active sites and quick ion/electron transfer during the charge/discharge process to improve the flexible energy storage device performance. We provide future perspectives that boost the performance of flexible supercapacitor.