IEEE Power Electronics Magazine - September 2023 - 56

the recombination of the ions. Consequently, a double layer
with two layers of charges is produced at each electrode.
These layers are coupled with an increase in surface area
and a decrease in the distance between electrodes, allowing
EDLCs to increase capacitance and achieve higher energy
densities [10].
Since this is a non-faradic process with no chemical
reaction, EDLCs have a highly reversible charge storing
ability allowing them to achieve high cycling rates
because of their cycling stability. So, this type of SC is
great for general applications, replacing rechargeable
batteries and also for non-user serviceable areas such as
deep-sea or mountains because of their high cycle rates.
By changing the nature of the electrolytes, the characteristics
of these SCs can be adjusted and the electrolyte
for an EDLC can be selected from either an aqueous or
organic material. Compared to organic material such
as acetonitrile, aqueous electrolytes, non-organics such
as H2SO4 and KOH typically have lower ESR values and
lower minimum pore size requirements. However, they
offer lower breakdown voltages and thus, when selecting
the material for electrolyte, the trade-offs between
capacitance, ESR, and voltage should be considered and
hence the selection of electrolyte mostly depends on the
requirements of the application [10].
Sub-categories of EDLC types are characterized primarily
using carbon as the electrode material as they are
typically having a higher surface area, lower cost, and welldeveloped
fabrication methods than other materials, such
as conducting polymers and metal oxide [10]. Therefore,
the electrodes of EDLCs are made using various forms of
carbon materials and the sub-categories of current EDLCs
which are commercially available can be found as activated
carbons, carbon aerogels, and carbon nanotubes based
EDLCs [10].
Commercially Available Supercapacitors Versus
Li-Battery Performance Comparison
We have collected samples of several different supercapacitors
from Samwha Electric, Korea [11] for comparison.
Based on publicly available construction details from Samwha,
the differences in construction are presented below.
■ Standard type activated carbon EDLC consists of active
carbon electrodes and an organic solvent.
■ High-temperature type activated carbon EDLC consists
of active carbon electrodes and an organic solvent.
■ LMO type asymmetric hybrid utilizes lithium manganese
oxide electrode and an activated carbon electrode.
■ LTO type asymmetric hybrid utilizes lithium titanium
oxide electrode and an activated carbon electrode.
■ High-energy battery type utilizes the negative LTO electrode
and the positive Li transition metal oxide electrode
and offers a high-power density of over 1 kW/kg and a
high energy density of over 110 Wh/L.
■ High-power battery type utilizes the negative LTO electrode
and the positive Li transition metal oxide electrode
and offers a high-power density of over 1.7 kW/kg and a
high energy density of over 65 Wh/L.
Table 3 compares the engineering specifications of these
commercial types of supercapacitors and Li-ion battery.
Table 4 compares the temperature capability, cycle life, and
shelf life, etc., of different types of supercapacitor families.
FIG 8 Categorization of SC families [10].
56 IEEE POWER ELECTRONICS MAGAZINE z September 2023
IEEE Power Electronics Magazine - September 2023

Table of Contents for the Digital Edition of IEEE Power Electronics Magazine - September 2023
