Among these, again HTC-750_1 showed the highest gravimetric capacitance, with a high BET surface area (2062 m 2 g -1 ) and a large ion adsorption capacity (1.3 mmol g -1 ) (Figure ), consistent with the more dramatic activation observed for HTC-750 above (Figure , Table ). However, similar to HTC-750, its volumetric and surface area normalised capacitances were lower than those of HTC-600 and HTC-650 (Figure ), reaffirming that higher surface area does not always translate to better performance for commercial EDLCs. HTC-1000_1, with a Δδ value of larger magnitude, exhibits a more ordered structure and lower capacitance (Figure ), mimicking the behaviour of commercial activated carbons. Finally, HTC-1200_1 shows a much lower capacitance, likely due to pore collapse at such high synthesis temperatures (Figure , Table ), as indicated by the very small ion adsorption capacity of 0.08 mmol g -1 (Figure ). Overall these results suggest that both the sizes of the graphene-like domains and ion adsorption capacities impact the capacitance, which is further explored below. While our carbons with smaller graphene-like domains show enhanced capacitance per unit surface area, they do have some limitations that require further exploration and optimisation. Firstly, carbons synthesised at lower temperatures exhibit slightly poorer conductivity, as indicated by the more resistive voltammogram for HTC-600, which deviated more evidently from the ideal rectangular shape (Figure ). Secondly, the low-temperature synthesised carbons were found to have reduced cycling stability compared to commercial activated carbons (Figure ). Floating tests were conducted to study the cycle lives (See Methods) of the low-temperature synthesised carbons and showed more rapid degradation compared to commercial activated carbons (Figure ). The conductivity and degradation issues can potentially be addressed in the future by incorporating conductive additives, e.g. carbon black, and by electrode mass balancing, respectively, to improve the overall performance of the devices. We propose that the concept of low-temperature activated carbon synthesis can be extended beyond the specific methods used in this study e.g. by using a range of biomass precursors and activation methods.