## 1 Introduction  
In recent years, the use of electric vehicles (EVs) has spread widely due to the fewer pollutants they send into the environment. However, there are still some obstacles on the way of their further adoption, including the higher cost in comparison to internal combustion engine vehicles (ICEVs), lower energy density than ICEVs, and their problem in providing the high-power demand during sudden acceleration. To overcome the pricing issue, many Governments encourage car manufacturers and buyers by providing subsidies for further research and development and to reduce the manufacturing cost. Apart from the pricing, a good energy storage system (ESS) capable of providing enough energy for better mileage and enough power for acceleration still needs to be improved in the future. Many analyses in the literature show that the average power demand in vehicular applications is much lower than the peak power demand so that the peak to average power ratio is between 4 and 7 [1]. This requirement raises the need for a special type of EES for EVs. Among the different energy storage systems presented in the market, lithium-ion batteries (LiBs) attract a great deal of attention for their high energy density, however, their low power specification (peak to average ratio between 0.5 and 2 [1]) makes them unfavorable for acceleration purposes [2]. Moreover, high charging/discharging rates when they are used in urban driving cycles has a negative effect on their performance by affecting the efficiency, lifetime, and internal resistance value [3]. Among the different type of LiBs available in the market, lithium iron phosphate (LFP) batteries have shown a significant potential for sudden power consumption and a better cyclability in comparison to the other types of LiBs, but, their lifespan and reliability need to be studied more. Super-capacitors (SCs) are another candidate which can be used as ESS in EVs. They have a higher power density in comparison to the LiBs, as well as a higher cyclability and reliability, nevertheless, they have a lower energy density in the range of 4-7 Wh/kg. As mentioned before, the ESS should be able to fulfill both the power and energy demand for the EVs. One possible solution is to overdesign either of them, which creates an expensive, voluminous, and heavy ESS. Another possibility is to externally combine LiBs as a high-energy system with SCs as a high-power storage system. With this combination, the energy and power density of the entire system can be improved. However, these energy storage systems have different charge and discharge behaviors as LiBs are non-linear devices and SC are rather linear. Moreover, having a lower voltage level than batteries, SCs need to be connected to the DC link through a DC/DC converter, which increases the cost and complexity of the system. SCs can also be replaced by a hybrid super-capacitor (HSC). HSC is an emerging technology which has attracted a great deal of attention in recent years. Many studies have been presented in the literature aiming to make HSC environmentally friendly and cost effective in comparison to competing technologies while keeping the surface area as high as possible [4; 5]. HSC, also known as a lithium-ion capacitor (LiC), is an internal hybrid energy storage device where its structure consolidates SC and LiB technologies. Its basic structure includes a positive electrode with activated carbon, as in super-capacitors, and a negative electrode based on Li-Ion-doped carbon similar to the LiBs [6]. The application of LiCs is increasing quickly due to advantages that they have compared to the SCs, including a high power capability around 10 kW/kg, a higher maximum voltage (3.8 V) and a higher energy density (up to 14 Wh/kg) [7]. However, having a higher voltage level does not necessarily eliminate their need for DC/DC convertor for hybrid application, but it decreases the cost and loss of the convertor significantly since a part of hybridization is done internally in the LiC cells.