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22-32 

22 

 

 

 

Review 

The perspective of energy storage systems 

advancements and challenges for electric vehicle 

applications; metric, mechanism, mode, and 

mitigation framework 
Sadegh Mehranfar1*, Isa Banagar1, Jamshid Moradi1, Amin Mahmoudzadeh Andwari1*,  

Juho Könnö1, Ayat Gharehghani2, Moeed Rabiei2, Emil Kurvinen1 

1Machine and Vehicle Design (MVD), Materials and Mechanical Engineering, Faculty of Technology, University of Oulu,  
FI-90014 Oulu, Finland 
2School of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran 

               A R T I C L E   I N F O 
 

Article history: 
Received 22 September 2024  
Received in revised form 
26 October 2024 
Accepted 04 November 2024 
 
Keywords:  
Battery electric vehicles, Fuel cell electric vehicles, 
Energy storage systems 
 
*Corresponding author 
Email address: 
Sadegh.Mehranfar@oulu.fi 
Amin.m.andwari@oulu.fi    
 
DOI: 10.55670/fpll.fusus.2.4.4 
 

A B S T R A C T 
 

New advancements in the automobile industry require greater demonstration 

of the role of energy storage in EVs. More effective energy production and 

storage require an in-depth look at the recent advancements and challenges of 

energy storage systems (ESS). This paper presents a holistic and hierarchical 

framework of metric, mechanism, mode, and mitigation of ESSs recent 

advancements and challenges, including a) Evaluation metrics for 

advancements, b) Identification of mechanisms and most important challenges, 

c) Mode and effects analysis, d) Mitigation through material 

optimization/system design. A comprehensive review was conducted by 

comparing different batteries, fuel cells, and supercapacitors’ efficiencies, 

performance, advantages, and disadvantages. 

 

1. Introduction 

In the last decade, increased environmental concerns, 

rapid technological advancements, and transmission into 

electrification in the automobile industry have put energy 

storage systems (ESS) at the center of attention. Among 

different ESSs for EVs, batteries, fuel cells, and 

supercapacitors exhibit the potential to shape EV applications 

thanks to each technology's new advancements and 

advantages to address required energy/power density, 

lifetime, cost, and safety [1]. Despite global efforts to enhance 

energy density, improve power capability, and reduce costs, 

challenges remain in ensuring the cyclability and safe 

operation of high-energy-density ESSs. Electrochemical and 

thermal stability, material development, and system design 

remain major concerns, particularly following their mass 

adoption in the coming decades [2]. Figure 1 demonstrates 

the global electric car stock trends in the 2010-2023 

timespan. These trends indicate that battery electric cars 

accounted for 70% of the electric car stock in 2023 [3]. This 

paper aims to review the application of energy storage 

systems (ESS) in EVs with specific attention to battery 

technologies, fuel cells, and Supercapacitors. ESSs have long 

played a pivotal role in improving the system's performance 

in-vehicle applications by delivering energy into the system 

or saving energy produced by the system. Fuel cells, 

supercapacitors, ultra-capacitors (UCs), and various battery 

technologies have been widely adopted in EV applications 

and have shown promising results in terms of improving fuel 

economy [4]. The recovered energy is stored in an ESS 

reservoir for later use when acceleration. Two of the most 

important indicators of total energy and power per unit 

weight are introduced as specific power and specific energy. 

These two parameters are considered the most determinative 

factors in EES systems in transportation applications, for they 

directly influence the travel range and weight of the vehicle.  

Future Sustainability 

Open Access Journal 

https://doi.org/10.55670/fpll.fusus.2.4.4 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

November 2024| Volume 02 | Issue 04 | Pages 22-32  

Journal homepage: https://fupubco.com/fusus 

 
ISSN 2995-0473 

mailto:Sadegh.Mehranfar@oulu.fi
https://doi.org/10.55670/fpll.fusus.2.4.4
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Sadegh Mehranfar et al. /Future Sustainability                                                               November 2024| Volume 02 | Issue 04 | Pages 22-32 

23 

 

 
Figure 1. Global electric car stock trends 2010-2023 [3] 

The result of the specific power and energy comparison 

in different EES technologies is illustrated in Table 1 [5]. 

Supercapacitors, also known as ultra-capacitors, can produce 

considerable energy at low voltage. They stand in an 

advantageous position in ESSs due to their high-power 

density and fast charging and discharging. Nonetheless, UCs 

are only completely well suited for EV applications once low 

energy density is addressed [6]. On the other hand, batteries 

are considered the most promising ESS technology in 

transportation technologies and have been widely accepted 

by manufacturers because they offer substantially higher 

energy storage capabilities. Annual predictions show a steep 

growth in Li-ion battery demands in the upcoming years [3]. 

Nevertheless, Li-ion batteries come with their challenges. 

Safety issues in Li-ion batteries remain a concerning 

challenge. Increased temperature in Li-ion batteries can cause 

a series of chain reactions, leading to battery fire and 

explosion [7]. Complexities in different ESSs can rise from 

different scales, from material development to system 

integration [8]. Developing new nanostructured electrodes 

for increasing the energy density of UCs and designing flow 

fields in PEM flow fields are some trending research that 

targets the current ESS constraints [9]. This paper presents a 

holistic and hierarchical framework of metric, mechanism, 

mode, and mitigation of Ess's recent advancements and 

challenges, including a) Evaluation metrics, b) Identification 

of mechanisms and causes, c) Mode and effects analysis, d) 

Mitigation through material optimization/system design. A 

Brief Comparison of ESS technologies is presented in Table 1 

[5]. 

2. Energy storage systems 

2.1 Batteries 

As one of the most prevalent energy storage and 

propulsion systems in the transportation industry, batteries 

can be a perfect fit for vehicle powertrains due to their high 

energy density, fast response, high efficiency, and zero 

tailpipe emission as a crucial aspect in future mobility. 

Moreover, integrating batteries into the vehicle powertrain 

will bring more flexibility in the electrification of ancillary 

units, system modularity, better regenerative break, and less 

maintenance for less mowing parts into the electric vehicles.  

 

 

Introducing batteries in electrified vehicles will bring 

about zero-tailpipe emission benefits and improve urban air 

quality. While existing hurdles in the way of EV battery 

advancements, such as raw material supply constraints, 

burdensome cost, and safety threats in higher density 

chemistries, are proposing challenges for EV battery 

industries, exceptional advantages of EV batteries call for an 

increase in the number of research in this area since the 

annual global demand for EV batteries would reach 1925 

GWh by 2030 by a 688% increase from 2021. New regulations 

also impose net zero tailpipe emission, facilitating vehicle 

electrification and leading to further market growth. As a 

result, many research institutions and automotive 

manufacturers are investing in the integration of EV batteries 

and the development of batteries for EVs. A group of battery 

cells forms battery modules, and battery packs comprise 

battery modules designed with EVs of the desired capacity. 

Battery pack design complexities bring numerous challenges 

due to the control of cell voltage, state of charge, and thermal 

issues throughout the operation.  

Table 1. Comparison of ESS technologies  

 

  Battery Supercapacitors  Fuel cells 

Specific 
Energy 
(Wh/Kg) 

30-300 0.05-15 100-450 

Specific Power 
(W/Kg) 

<2000 <10000 <200 

Power rating 
MW 

0.005-100 0.0001-0.1 0.005-50 

Energy capital 
cost ($/kWh) 

100-150 300-2000 230-330 

efficiency (%) 70-100  84-97 60-80 

Charge Time 1-5 h 0.3-30 S 3-5 min 

Discharge 
Time 

0.3-3 h 0.3-30 S 0.3-3 h 

Daily self-
discharge (% 
per day) 

<0.03-0.3 Oct-20 - 

Lifetime 
(years) 

2-20  10-12 1-10 



Sadegh Mehranfar et al. /Future Sustainability                                                               November 2024| Volume 02 | Issue 04 | Pages 22-32 

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Battery cells group together and form modules. Several 

modules also group to form battery packs. Battery 

management systems handle the interconnection between 

cells and modules. BMSs monitor and control the batteries 

efficiently and safely through numerous tasks such as 

monitoring, protection, charging and discharging 

management, communication, diagnosis, and data 

management. Critical states of batteries, such as state of 

power, health, charge, energy, power, temperature, and 

safety, are required for effective charging, thermal 

management, and health management. Batteries produce 

heat as a result of electrochemical reactions. Very high and 

low temperatures adversely affect battery performance, life, 

and safety and might impose degradation and even 

overheating if not handled properly. This comes to the 

importance of thermal management. It has been reported that 

higher temperatures can be very problematic for EV batteries. 

Higher temperatures lead to the accumulation of heat and 

trigger chains of exothermic reactions, which lead to 

combustion and even the explosion of batteries. This 

phenomenon is called Thermal runaway (TR) and is more 

extreme in higher energy density materials, owing to more 

chemically active materials. The TR behavior calls for 

additional countermeasures for thermal management for 

safety [7]. The design of BTMS calls for attention, and 

numerous investigations were focused on leveraging heat 

transfer mechanisms for keeping the batteries in the optimal 

range, including active methods (Air cooling and liquid 

cooling), passive methods (Phase change materials and Heat 

pipes) and hybrid methods (Integration of active methods 

with passive methods) [1, 9]. Performance indexes such as 

energy efficiency, maximum temperature, and temperature 

difference are satisfied with BTMS designers as 

the temperature has the most effect on the aging mechanism 

and threads' lifetime of batteries. The importance of BTMS 

comes into play in terms of safety implications as well. This is 

due to the thermal runaway concerns in the accumulation of 

heat and raised temperature, which leads to further exoteric 

chained reactions and finally combustion or even explosion of 

batteries. In the core of battery systems in EVs, there are 

numerous interconnected battery cells. Battery cells 

correspond to more than 75% of battery overall costs and 

determine the characteristics of the system. Energy density, 

power density, cost, safety, and lifetime are the main critical 

factors for EV battery selection [10]. Improvements in the 

energy density of batteries have been greatly focused as one 

of the main critical factors in EV batteries since the shift from 

the ICE market requires batteries to deliver a comparable 

driving range and lower cost, which leads to an exploration of 

new batteries for higher energy densities. Early EV batteries, 

such as Pb-acid batteries, offered competitive prices in the 

market but suffered from low energy density. NiCd batteries 

showed promising lifespan, while destructive materials 

impeded their commercialization. NiMH was also utilized in 

hybrid-electric passenger cars (Toyota Prius) and resolved 

previous challenges, but still was hindered by low storage 

capacity and self-discharging. Li-ion batteries revolutionized 

the EV market owing to their exceptional energy density, 

lifecycle, and low self-discharge, which is highly important in 

transportation applications. Higher energy density expands 

the range as one of the main obstacles to EVs. The reported 80 

Wh kg-1 has seen a steep growth from 1991 to 2020 and 

reached a satisfactory number of 400 Wh kg-1 [7]. Li-ion 

batteries also propose great energy efficiency and boost EV 

performance (Up to 95% compared to 70% and 65% in lead-

acid and NiMH batteries) [11]. Li-ion batteries come in many 

characteristics in terms of chemistries. An overview of battery 

chemistries is provided in the review of Chemali et al. [12]. 

The cell chemistry selection is a great design choice for EV 

battery designers since pure EVs require high energy storage, 

and hybrid electric vehicles call for power [13]. In addition to 

the main two factors of energy and power density, cells 

should operate safely in different loads, overcome complex 

mechanical, electrical, and thermal loads in various working 

conditions, and offer a high life cycle to work for many years. 

Therefore, exploring new chemistries and material 

advancements is the research direction for manufacturing 

high-energy, safe, and affordable EV batteries with increased 

lifespan. A comparison of battery characteristics in EV battery 

evolution is presented in Table 2. The US advanced Battery 

consortium target is also presented in the table to highlight 

the target goals in the battery technology advancements [14]. 

In addition to the promising characteristics of new cell 

chemistries, battery materials correspond to more than 70% 

of battery cell cost. Hence, breakthroughs in cell materials will 

facilitate the market penetration of battery EVs [11]. 

Different battery technologies arise from various types of 
cathodes, anodes, and electrolytes. Currently, lithium cobalt 
oxide (LCO) dominates the market and is the mature cathode 
chemistry. Other cathode technologies such as lithium iron 
phosphate (LFP), lithium nickel manganese cobalt oxide 
(NMC), lithium nickel cobalt aluminum oxide (NCA), and 
lithium manganese oxide (LMO) are advancing and tracking 
the place of LCO in the market by offering more stable crystal 
structures, lower price, and more abundant materials. LFP 
offers fast charging and low volumetric energy density and 
fits better in public transport and heavy-duty applications. 
However, it has reached its theoretical limit (170Wh/kg) and 
cannot satisfy the expectations of the next generation of EV 
batteries. Despite the low energy density and lifetime, LFP 
battery EVs dominate the commercial EV section due to lower 
material cost (50% less material cost than NCA). LMO offers 
high power but low energy density. Battery types can be 
blended to other high energy density chemistries like NMC to 
take advantage of both types (e.g. LMO/NMC composite for 
BMW i3 and Nissan leaf). NMC takes advantage of low internal 
resistance from manganese, high capacity from nickel, and 
low cost from less cobalt by combining Ni, LMO, and LCO). It 
is estimated that NMC will grow its share in the market due to 
higher energy density than LFP, while others (NCA and LMO) 
remain constant. The energy density of the cell level has 
reached 250 Wh/kg, reaching the promising 300 km range 
[10]. A comparison of Li-ion battery technology across 
energy/power density, safety, lifespan, and cost is presented 
in Figure 2. A. Comparison of Li-ion cathode chemistries and 
the effect of chemistries on the characteristics of the cells is 
also elucidated in Figure 2. B, C and D. [1, 10, 11]. 

Anode materials are also under development with the Si 
integration breakthrough. Si offers exceptionally higher 
energy density but comes with thorny issues such as material 
swell and huge volume explanation during lithiation, leading 
to capacity loss (The calendar life of Si-anode batteries is still 
only 20–30 months, against the EV requirement of 100–140 
months [15]).  

 



Sadegh Mehranfar et al. /Future Sustainability                                                               November 2024| Volume 02 | Issue 04 | Pages 22-32 

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Table 2. Comparison of different battery characteristics in EVs 

Battery 

type 

Energy 

density 

(Wh/kg) 

Specific 

power 

(W/kg) 

Life cycle 

Energy 

Efficiency 

(%) 

Production 

cost ($/kWh) 
Advantages Disadvantages 

USAB goal 350 700 1000 
 

100   

Lead acid 

(Pb-acid) 
35 180 1000 

70-90 

60 

+ Low initial cost 

+ Maturity in technology 

+ Good network of 
manufacturing 
infrastructure 

+ Abundant and affordable 
raw materials 

- Low specific energy and 
power 

- Short life cycle 

- Temperature-sensitive 
performance 

- Charging time 

- Safety concerns due to 
gas release and 
hazardous lead 

Nickel-

cadmium 

  (Ni-Cd) 

50-80 200 2000 

60-70 

250-300 

+ Good cycle lives 

+ Wide operating 
temperature range 

+ Good safety 

+ Low charging time 

+ Mature technology 

- Memory effect 

- Reliance on hazardous 
cadmium 

Nickel-

metal 

  hydride 

(Ni-MH) 

70-95 200-300 <3000 

50-80 

200-250 

+ Good specific energy and 
power 

+ Eco-friendly materials 

+ Extensive operating 
temperature range 

+ Good safety 

- High Self discharging 

- Memory effect 

ZEBRA (Na-

NiCL) 
90-120 155 >1200 

80 

230-345 + Low self-discharging and 
no memory effect 

- Extremely high 
temperature range 

- Thermal management 
and safety issues 

Lithium-ion 

(Li-ion) 
118-250 200-430 2000 

70-80 

150 

+ Outstanding specific 
energy and power 

+ Long cycle lives 

+ Satisfactory operating 
temperature ranges 

+ Chemistry diversity 

+ Eco-friendly material 
technologies 

+ Fast charging 

- High initial cost 

- Sophisticated BMS 
technology required 

- Safety concern for 
thermal runaway 

- Material depletion 
concerns 

Lithium-ion 

  polymer 

(LiPo) 

130-225 260-450 >1200 

70 

150 
+ Better packaging 

optimization compared 
to Li-ion 

 

Lithium-
iron 

phosphate 
  (LiFePO4) 

 

120 
2000-

4500 
>2000 

90 

350 

+ High power density than 
Li-ion 

+ Better safety compared 
to Li-ion 

- Lower energy density 
compared to Li-ion 

Zinc-air (Zn-
air) 

 

460 80-140 200 
60 

90-120 + Relatively high energy 
density 

- Low power density 

- Short life cycle 

Lithium-
sulfur (Li-S) 

 

350-650 - 300 
 

100-150 
+ Relatively high energy 

density 

+ Low cost 

- High discharge rate 

- Short life cycle 

Lithium-air 
(Li-air) 

 

1300-

2000 
- 100 

 

- 

+ Exceptionally higher 
energy density 
(Comparable to those of 
ICEs) 

- Short life cycle 

- Sill in prototype stage 

 

 



Sadegh Mehranfar et al. /Future Sustainability                                                               November 2024| Volume 02 | Issue 04 | Pages 22-32 

26 

 

 
 
 
 
 
 
Si-C composition and electrolyte additives for 

stabilization are known as the target solutions. Today, only 
10% Si composition is viable, but Si can offer up to 4200 
mAh/g theoretical capacity. Another breakthrough in anode 
material development is lithium metal, which has a specific 
capacity that is 10 times higher. Li metal development is 
hindered by high reactivity, Lithium deuteride growth, and 
thermal runaway caused by short circuit concerns. The 
abovementioned issues can be handled by applying 
protective layers or embedding Solid-state electrolytes. Solid-
state electrolytes will be the next generation of Li-ion 
batteries and resolve the bottleneck. Li foil anodes unlock the 
energy capacity of graphite anodes, pushing the 280 Wh/kg 
to ≈ 500 Wh/kg. The lithium metal foil supply chain should be 
addressed in the next generation of batteries to meet the 
market demand for SSBs. Figures 2 E and G illustrate the 
integration of Si for high energy density Li-ion anodes and 
compare typical Li-ion batteries with lithium metal cells. It is 
expected that the battery market will heavily rely on 
currently matured technologies such as NCA, NMC, and higher 
energy NMCs. EV battery technology also depends on 
the application. Heavy-duty applications require longer cycle 
lives, and NMC/LFP batteries are more favorable in 
commercial EVs than Ni-rich and lithium metals. SSBs are the 
dominant technology in the long term from 2025 onward, 
with Li dendrite suppression for safety and high-performance 
anode material uptake for high energy density being the main 

 
 
 
 
 
 

 incentives. The cost of the battery is highly dependent on the 
material supply, investment in research and development for 
developing new cell chemistries, cell manufacturing process, 
battery pack design, optimizing the BMSs, and battery second 
life and recycling. Costs have continuously decreased since 
the early introduction of EV batteries. Reports show that Li-
ion EV battery pack cost dropped by approximately 90% in 
the 2010-2021 timespan and will fall below $100/kWh in 
2024 [16]. There are other factors in EV batteries that must 
be focused on in order to achieve market dominance. Capacity 
decay occurs in the battery cells every time it is charged and 
discharged, reducing driving range and service life. The effect 
of aging is greatly dependent on the battery type, reaction 
stage, and operating condition, and battery health monitoring 
and aging diagnostic is one of the main targets of battery 
management systems, along with the investigation of battery 
aging mechanisms and proposing prevention methods. 
Temperature adverse effects are known to have the most 
aggressive effect on battery aging, which further highlights 
the importance of effective battery thermal management 
systems. Fast charging is another technological advancement 
in the EV battery industry that has further assisted the EV's 
competitiveness by addressing the range anxiety in the 
decreased charge time. This also helps the raw material 
extraction limits since a 120kWh battery charged in one hour 
can be replaced by a 60kWh battery with 10 min charge time. 
The fast charging should also be evaluated by the number of 

Figure 2. Overview of Short- and long-term research directions for Li-ion battery developments A) Comparison of the Li-ion battery 

technology across energy/power density, safety, lifespan and cost. B) Comparison of Li-ion cathode chemistries by specific capacity and 

specific energy. C) Comparison of Mn, Co and Ni content in NMC, D) Increased EV battery specific energy density in Ni and Li rich cathodes, 

E) Integration of Si for high energy density Li-ion anodes, G) Comparison of typical Li-ion batteries and lithium metal cell 



Sadegh Mehranfar et al. /Future Sustainability                                                               November 2024| Volume 02 | Issue 04 | Pages 22-32 

27 

 

cycles since it causes degradation and low cycle life is also a 
downside in battery life. The ideal target is set by DOE as 
240 Wh kg−1 acquired energy after a 5 min charge with a 
more than 2,000 cycle lifetime. Different power levels in AC 
charging from 3 to 22 kW, and DC fast chargers from 40 kW 
to 120 kW are now permitted in the EV batteries [17]. 
Embedded fast chargers also bring other design aspects, such 
as redesign of vehicle electronics and thermal management, 
implementation of charging stations, and grid stability 
challenges [18]. Employing the fast-charging methods 
requires more aggressive BTMSs that cannot be handled by 
air cooling or even liquid cooling. Nonetheless, the 
implementation of fast charging station cooling for less 
weather independence, investigation of new BTMS for high 
heat transfer efficiency (Immersion and jet cooling), and cell 
design for lower temperature variation inside the cell due to 
high heat generation are some of the thermal considerations 
that should be addressed in this aspect. Graphite anode 
batteries are the first to unlock the fast-charging potential 
since conventional Li-ion batteries have undergone rapid 
capacity loss and safety hazards in fast charging due to 
heightened lithium plating risks [15]. The development of EV 
batteries calls for a huge value chain improvement. Despite 
the zero-emission tailpipe standards, the production and 
process of materials for manufacturing cells impose 
substantial carbon emissions. Therefore, to alleviate the 
environmental burden of the whole battery lifecycle, the 
lifecycle analysis of battery production and recycling of used 
batteries play a crucial role. The production emissions of 
batteries are mainly caused by battery cell manufacturing and 
mostly by positive electrodes, which further highlights the 
importance of electrode material design.  

 

 

Battery cooling systems, BMS, and packaging constitute 
components and subsystems in the battery system, as 
observed in the life cycle analysis. Safely disposing of 
batteries with less than 80% of their nominal capacity will not 
only minimize the overall carbon footprint but also reduce the 
cost since batteries in EVs account for almost 40% of the total 
cost of vehicles [19]. Figure 3 elucidates the most current 
solutions in EV batteries with their promises and challenges 
based on the main design metrics. 

2.2 Supercapacitor  

Supercapacitors or Ultracapacitors are some of the most 
attractive ESSs that contribute to the growth of low to high-
power applications. UCs can store and recover energy in EV 
applications and improve the overall performance of 
the system in terms of energy efficiency. UCs come into play 
when batteries cannot meet the energy demand in EV 
systems. Moreover, the ever-changing and erratic inherent 
energy consumption with changes during battery charge and 
discharge is very harmful to the electrochemical process of 
the battery. This can be resolved by utilizing UCs as a high-
rate ESS accompanied by the battery to provide the excess 
energy demand of EVs. A fuel reduction of 10% is reported by 
the manufacturers of passenger cars when exploiting UCs to 
store breaking energy [20]. Supercapacitors offer extremely 
higher specific power density (up to 100 times) but suffer 
from lower energy density when compared to batteries. In an 
electric double-layer capacitor (EDLC), a double-layered 
conductor with equal and opposite electric charges allows the 
UCs to store energy by electrostatic charge accumulation. 
EDLC is the most commonly used SC.  

 
 
 

 
 

Figure 3. Recent progress in EV batteries with their mechanism, mode, and mitigation challenges based on the principal design metrics 



Sadegh Mehranfar et al. /Future Sustainability                                                               November 2024| Volume 02 | Issue 04 | Pages 22-32 

28 

 

Phosphoric capacitors (PC) offer higher energy densities 
at the expense of power density and cycling stability by 
storing charge via the faradic process. Hybrid 
supercapacitors (HSC) combine the characteristics of EDLC 
and PC and offer a good combination of power and energy 
density, and cycling stability. Li-ion capacitors are one 
example of HSE [14]. Table 1 illustrates different 
supercapacitor technologies' energy and power density [21]. 
Supercapacitors guarantee a long life due to the lack of 
chemical reaction in the electrodes, which is in contrast to 
batteries, and offer a much faster storage capability, which is 
appealing to mobile machinery. Recent developments in 
electrode materials have been trying to enhance the charge 
stability, cyclability, and energy density of UCs in EV ESSs. 
Compared to aqueous electrolytes, non-aqueous electrolytes 
show a higher energy density due to the high voltage window, 
enabling the use of high-voltage active materials in the 
supercapacitor. Non-aqueous electrolytes also offer better 
stability and longer cycle life. However, challenges such as 
cost, toxicity, and flammability stay ahead of non-aqueous 
electrolytes despite their advantages. Exploring new 
materials for SC electrolytes, such as NASICON-type 
materials, is the future of SC development. The advantages of 
new electrolyte materials, such as high conductivity, good 
cyclic stability, and enhanced energy and power density, will 
play an important role in commercializing SCs in EV 
applications [22]. Figure 4 elucidates the most current 
solutions in EV SCs with their promises and challenges based 
on the main design metrics. 

2.3 Fuel cells 

The advent of fuel cells has been considered a 
technological marvel in energy and transportation systems 
due to their capability to provide zero carbon, efficient, and 
adaptable power sources. Fuel cells have been at the center of 
increased attention in recent decades owing to their well-
competent characteristics and better performance in terms of 
range and efficiency in the automotive industry. Compared to 
the ICEs and BEVs, fuel cells can take advantage of their 
exceptional characteristics by offering higher energy 
efficiency than ICEs, as a matter of direct conversion of 
chemical energy to electricity, and maintain a longer driving 
range than BEVs by cutting out charging time. Fuel cells owe 
these interesting features to the generation of emission-free 
(green) electricity and not to the storage, allowing them to 
enjoy the high range capability of IC engines without 
sacrificing the clean and sustainable power supply of BEVs. 
Implementing FCEVs in the transportation industry offers 
many other advantages, such as modular structure, silent 
operation, and flexible power ratings, turning FCs into an 
appealing choice for vehicles ranging from passenger cars to 
buses and trucks. The attractive lifetime range of FCs (20-25 
years) is another interesting factor in the vehicle industry 
that needs to be considered [23]. Fuel cells are not heat 
engines; hence, their efficiency is not limited by the Carnot 
limit as in the IC engines. Therefore, the FCEVs can enjoy a 
sustainable power supply to run the system if the cells are 
maintained fuel and oxidant. This inherited nature of FCs can 
also extend the BEV capabilities by charging batteries while 
operating. Notwithstanding the wide variety of fuel cells, 
which are classified into six classes, including proton 
exchange membrane fuel cells (PEMFCs), alkaline fuel cells 
(AFCs), phosphoric acid fuel cells (PAFCs), molten carbonate 
fuel cells (MCFCs), solid oxide fuel cells (SOFCs), and direct 
methanol fuel cells (DMFCs), each type of fuel cells can cover 
a specific application depending on their limits and 

advantages. Among all types of different fuel cells, PEMFCs 
can be a perfect fit in EV applications by maintaining a proper 
operating temperature range and high-power density, which 
leads to a fast startup time required in the transportation 
industry and a lightweight load to carry for its smaller size, 
respectively. PEMFCs, by exploiting the zero-carbon and high 
energy density hydrogen gas, can stand out in EV applications 
and are in progress. However, the challenges of 
commercialization in FCEVs are steep [24]. The very first 
challenge of FCEVs is fuel supply. There are currently two 
practical ways of storing hydrogen: high-pressure gas or 
cryogenic tanks. Each of them faces important challenges that 
need to be addressed. Pressurizing hydrogen can be very 
costly or even hazardous. Energy per liter of H2 is equivalent 
to 0.1 liter of gasoline (~1kWh) at the pressure of 350 bar. 
Something in the margin of 25% of its energy should also be 
consumed to compress the gas into that high pressure, let 
alone the weight of such a strong tank to tolerate this 
pressure and safety issues if a dangerous tank is used in 
transportation applications. Liquid hydrogen stored in 
cryogenic tanks also faces important challenges.  

Facilities to keep the low temperature (-259.2 °C) can 
add to the weight of the vehicle, liquefying hydrogen is costly, 
and in case of dropping the temperature and boil-off, the tank 
is susceptible to highly pressured liquid-gas mixture or even 
explosion in a vase of using safety valves [24]. The power 
transmission structure of FCEVs includes an FC stack to 
supply energy, a hydrogen tank, a unidirectional DC-DC 
converter for FC, a motor drive converter, and an electric 
motor. Additionally, different energy storage and/or 
generation units can integrate with fuel cells and hybridize 
FCEVs. Batteries, Supercapacitors, Photovoltaic panels, and 
flywheels are some hybridization units that can offer a variety 
of hybrid FC designs, with FC-battery hybridization being the 
most popular topology. A general schematic of FCEVs and 
hybrid FCEVs power transmission structure is depicted in 
Figure 5. 

There are more than 34,800 FCEVs and 540 hydrogen 
refueling stations worldwide, with passenger cars 
dominating the vehicle market (~75%) [25]. Announced 
targets are also set to reach 10-15 million and 400 million 
FCEVs by 2030 and 2050, respectively. Samsun et al. [26] 
conducted detailed statistical analysis and perspectives on 
the development of FCEVs and hydrogen refueling station 
infrastructure. Even though the fuel supply in FCEVs can be 
problematic and PEMFCs are still expensive, FCEVs interest 
automotive companies and researchers to solve unresolved 
issues and make perfect use of fuel cells in EV applications. 
Expensive catalyst cost, hydrogen purity and production 
challenges, fuel station accessibility, and safe built-in storage 
are some challenging issues in the face of FCEV advancements 
underway to meet transportation needs. Almost 40% of an 
FCEV’s total cost comes from the stack, and 60% of it comes 
from the cell itself. More than 45% of the cost in the cell is the 
catalyst, which shows the importance of reducing Platinum 
loading in the catalyst or utilizing new catalysts [27]. Some 
studies have tried to investigate new catalysts that are much 
more affordable than precious metals. New FCs with efficient 
iron-based catalysts have even exceeded the DOE’s 2025 
target for current density [28, 29]. New investigations are 
also focused on safer and more affordable hydrogen storage 
methods and putting behind conventional compressed gas 
storage systems that have stalled the commercialization of 
the FCEV market. Solid hydrogen storage or metal hydride 
hydrogen storage technology can store the hydrogen for an 
extended period; however, charging time is still a problem.  



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29 

 

 
 
 
 

 
 
 
 
 
 

 
 
 
 

 
 
 
 

 
 

Figure 4. Recent progress in EV UCs with their mechanism, mode, and mitigation challenges based on the principal design metrics 

Figure 5. Recent progress in EV Fuel cells with their mechanism, mode, and mitigation challenges based on the principal design metrics 



Sadegh Mehranfar et al. /Future Sustainability                                                               November 2024| Volume 02 | Issue 04 | Pages 22-32 

30 

 

 
 
 
Recent investigations tackle this issue by designing new 

internal heat exchangers to address the low thermal 
conductivity of hydrogen and reduce the charging time by up 
to 59% [30]. Economically, scale can also unleash the FCEVs' 
market potential. Estimates show that fuel cell prices will 
drop 70 to 80% as production volume scales, according to 
Ballard, one of the biggest FC manufacturers. The ultimate 
DOE cost target is 30 $/kW. Component cost breakdown and 
cost reduction measure analysis are conducted in different 
studies [31, 32]. The cost of passenger light-duty vehicles in 
the US will be cut almost in half from 2030 to 2050, according 
to the International Energy Agency technology roadmap, and 
cost parity with ICEs will be reached by 2040 by the rapid 
ramp-up of fuel cell sales [33]. Also, the WtW emission of 
FCEVs will dramatically decrease by 2050, whereas it is 
currently almost comparable to ICE’s well-to-wheel CO2 
emission. It is expected that the vehicle industry will see a 
surge in FCEVs running on roads. Figure 6 illustrates the 
share of FCEVs and hydrogen refueling stations for different 
countries. 

 
3. Conclusion 

This study presents a holistic and hierarchical 

framework of metric, mechanism, mode, and mitigation of 

ESS recent advancements and challenges for Lithium-ion 

batteries, PEM fuel cells, and supercapacitors as three major 

potent candidates in EV ESS. Complexities in different ESSs 

can rise from different scales, from material development to 

system integration. Nonetheless, each technology poses its 

unique challenges and promises. Li-ion batteries are bound to 

reach higher energy and power densities and extended 

lifetime by advancements in new chemistries, solid-state 

batteries, and methods for suppressing dendrite formation 

for improved cyclability. However, safety concerns in 

Lithium-ion batteries remain a challenge due to increased 

energy density. Still, they can be controlled by investigation of 

more stable cell components and system-level safety 

integration. Furthermore, supercapacitors will continue to 

grow in EV applications by hybridizing materials with battery 

characteristics to improve energy density. PEM fuel cells will 

continue growing as interesting candidates for EV ESS. 

 

 

 

However, the design of flow field channels, improved 

performance, and optimized thermal and mechanical 

properties of the cells for better cyclability will remain 

important research directions for PEM fuel cells.  

Ethical issue 

The authors are aware of and comply with best practices in 
publication ethics, specifically with regard to authorship 
(avoidance of guest authorship), dual submission, 
manipulation of figures, competing interests, and compliance 
with policies on research ethics. The author adheres to 
publication requirements that the submitted work is original 
and has not been published elsewhere. 

Data availability statement 
The manuscript contains all the data. However, more data will 

be available upon request from the corresponding authors. 

Conflict of interest 

The authors declare no potential conflict of interest. 

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