Flexible MXene-conjugated polymer nanoarchitectures: Current developments and future frontiers in battery technology

The development of flexible nanomaterials for metal-ion batteries (MIBs) is important for ever-growing electrochemical energy-storage technologies. MXenes are a novel class of conductive two-dimensional nanomaterials with abundant active sites favorable for pseudocapacitive energy storage due to their wide interlayer spacing and active surface functionalities, enabling the easy intercalation of numerous metal ions. However, MXenes face the severe challenges of self-stacking and agglomeration, leading to low electrochemical kinetics and capacity deterioration. On the other hand, conjugated polymers (CPs) play a significant role in MIBs owing to their high structural flexibility, ionic conductivity, lightweight, and exceptional processability. However, they suffer from structural degradation in long-term practical use, hindering the electrochemical operation of MIBs. Therefore, MXene in conjunction with CPs can alleviate the aggregation of MXene, which can provide structural strength to the polymers. Furthermore, owing to their surface functional groups, MXene-conjugate polymer (MX-CP) composites can offer greater control over the physical and chemical characteristics of MXene. The addition of CPs enhances the energy-storage capability of MXene by expanding the interlayer gap, reducing the ion/electron transport distance, and improving surface hydrophilicity. In this review, we discussed recent advances in MX-CP nanoarchitectures developed for MIBs, the synthesis strategies, and the influence of MX-CP structures to enhance electrochemical properties, challenges, scientific solutions, as well as future perspectives. This review can motivate researchers to develop flexible MX-CPs for sustainable electrochemical energy storage (EES).