In the specific case of COF cathodes for LIBs, the amount of carbon black can vary from 10 to 70% in weight, depending on the intrinsic conductivity of the COF. In addition, a commonly used strategy to increase the electronic conductivity is the hybridisation of COFs with carbon nanotubes (CNTs), reduced graphene oxide, or conductive polymers. The COF/CNT composites are usually synthesised by in situ polymerisation, where COF layers are grown on the CNT surface (Fig. ). In general, such COF/CNT composites result in higher utilisation of active sites, high rate performance, and can help to improve cycling stability. For example, the preparation of PT-COF/CNTs composite cathodes for LIBs can increase the active site utilisation from 71% (PT-COF) to 98% (PT-COF composite with 50 wt % of CNTs). However, the PT-COF/CNTs composite shows a lower overall specific capacity (109 mAh g -1 ) than that of PT-COF (128 mAh g -1 ) when considering the mass of the active material and all conductive additives. This proves that the addition of too many inactive conductive additives can significantly reduce the energy density. It is also worth noting that most COF composites still require a large amount of extra conductive additives such as carbon black to achieve a satisfactory performance. Thus, improving the intrinsic conductivity of COFs and developing new strategies to minimise the amount of conductive additives in the electrode remain the main challenges for the design of high performance COF electrodes. Exfoliation of COFs into few-layer nanosheets. High exposure of the active sites and fast ion diffusion are key to achieve high specific capacity and high rate capability. In general, reducing particle size or increasing the specific surface area of organic materials are effective ways to improve the practical capacity. Most bulk COFs present strong π-π interactions between layers, which prevent ions from reaching the buried active sites and makes them inaccessible, limiting the practical capacity. Exfoliation of 2D COFs into few layer nanosheets is a successful strategy to increase the number of accessible redox sites and assist ion diffusion, increasing the performance of COF-based batteries (Fig. ). In general, there are several strategies for the preparation of COF nanosheets, from top-down methods based on different types of exfoliation (including mechanical and chemical exfoliation) to bottom-up approaches based on the preparation of well-ordered nanostructures. In the case of COF nanosheets for batteries, different exfoliation techniques have been employed for their preparation: mechanical (ball milling, ultrasound-assisted exfoliation, grinding, 38 etc.), chemical exfoliation (using external agents such as maleic anhydride , MnO2, acids, thiol-ene reactions, etc.) and self-exfoliation. Regarding bottom-up approaches, an example is the in-situ growth of graphene-supported COF nanosheets that are uniformly dispersed on carbon layers. The relationship between thickness and practical capacity was systematically investigated using a redox-active COF (DAAQ-COF) as anode in sodium batteries. In this case, three different exfoliation techniques were used to obtain different thicknesses: grinding (100-250 nm), ball milling (100-180 nm) and ultrasound-assisted exfoliation in methanesulfonic acid (4-12 nm). The thinnest (4-12 nm) and thickest (100-250 nm) samples showed capacities of 500 and 182 mAh g -1 (at 50 mA g -1 ), respectively. The resistance of the electrode also decreased from 428 Ω to 146 Ω after exfoliation. This study demonstrates that reducing the COF thickness can be an efficient strategy to improve the practical capacity and rate capability. However, the preparation of COF nanosheets still presents some challenges that need to be addressed. First, the thicknesses of the nanosheets are always obtained in a wide size range so precise thickness control remains challenging and can be problematic for reproducibility. On the other hand, the yields obtained for the preparation of nanosheets are usually relatively low and some exfoliation procedures can affect the crystallinity of the material.