Cycling stability. Stability is one of the most important parameters for evaluating organic electrodes in batteries. In general, organic compounds may present solubility problems in electrolyte (especially small molecules) leading to possible undesired side reactions, self-discharge issues and poor cycling stability. Other factors leading to low stability can be the instability of intermediates or volume change. Polymerisation is one of the main strategies to avoid solubility problems, along with salification and electrolyte optimisation (see above). When evaluating the stability of organic electrodes, we can take as a reference the capacity retention of some inorganic electrodes such as LiCoO2 or LiMn2O4 which exceeds 80% after more than 1000 cycles. 9 Some COF-based electrodes show a similar or even higher capacity retention after 1000 cycles, especially those based on β-ketoenamine, (cyano)vinylene , phenazine, 66 imide and piperazine 100,101 linkages (Fig. ), as they lead to the most stable frameworks. Normally COFs based on more reversible reactions such as boronate ester 103 or imine condensations 104 result in poorer stability. The strategy of pre-orientation, based on an initial reversible reaction followed by irreversible locking of the labile bond, can lead to very crystalline and highly stable COFs. Such a strategy has recently been explored to synthesise a thiazole-linked COF that was used as a cathode in lithium-sulphur batteries. We also note that in some cases COFs are hybridised with insoluble conductive substrates such as CNTs, which can help to improve the stability. As mentioned above, the electrolyte optimisation is also crucial to improve the cycling stability of COFs, as it may affect the dissolution or lead to side reactions. Scalability. Although large-scale applications of organic electrodes for metal-ion batteries are still a long way off, the possibility of scalability and production using simple low-cost methods needs to be evaluated. Some organic electrodes have already been scaled up at relatively low cost using high mass loading and pouch cells. Most COFs are synthesised using solvothermal conditions (typically between 120-150 °C), acid and high boiling point organic solvents such as mesitylene, 1,4-dioxane, or N,N-dimethylacetamide. More sustainable and environmentally friendly syntheses have already been proposed by replacing organic solvents with water, 108,109 using supercritical CO2, 110 or solvent-free methods. Microwave-assisted synthesis of COFs has also been extensively explored to considerably reduce reaction times. Recent studies have reported scalable methods to obtain COF nanosheets on a gram scale in a short time and mild conditions. Although most of the COFs used as electrodes in batteries have been obtained via solvothermal reactions, alternative, greener and cost-and time-efficient syntheses should be considered towards large-scale applications in the long term. As for most organic electrodes, the cost of such materials is too difficult to estimate until large-scale commercial scale-up is feasible. 9