  Nanoporous supercapacitors play an important role in modern energy storage
systems, and their modeling is essential to predict and optimize the charging
behaviour. Two classes of models have been developed that consist of finite and
infinitely long pores. Here, we show that although both types of models predict
qualitatively consistent results, there are important differences emerging due
to the finite pore length. In particular, we find that the ion density inside a
finite pore is not constant but increases linearly from the pore entrance to
the pore end, where the ions form a strongly layered structure. This hinders a
direct quantitative comparison between the two models. In addition, we show
that although the ion density between the electrodes changes appreciably with
the applied potential, this change has a minor effect on charging. Our
simulations also reveal a complex charging behaviour, which is
adsorption-driven at high voltages, but it is dominated either by co-ion
desorption or by adsorption of both types of ions at low voltages, depending on
the ion concentration.
