IMPROVING BATTERIES THROUGH SELF-HEALING SILICON ANODES
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IMPROVING BATTERIES THROUGH SELF-HEALING SILICON ANODES
Raul Casas RAC198, Andrew Buonanno APB57, Josh Briggs JMB431
Abstract—Constructing more efficient batteries has emerged CURRENT LITHIUM-ION BATTERY
as a crucial prerequisite in the process of making new TECHNOLOGY
technologies viable, such as electric cars. When considering
how to improve upon current batteries, factors like energy-
density, cost, and safety are key. This means manufacturers Lithium-ion batteries are the current standard for battery
can increase energy output from each battery, resulting in technology. Lithium is lightweight and has massive
increased driving range and fewer batteries necessary. For electrochemical potential, which leads to higher possible
consumers, this means a more viable alternative to gas or voltages than previous batteries using nickel [1]. There are
hybrid vehicles. other options for batteries, but they are outdated or flawed.
Replacing the widely-used carbon graphite anode with a The closest competitor for lithium-ion batteries is the
silicon based self-healing anode is a possible solution. This Nickel Metal-Hydride (NiMH) battery, but in application the
paper will discuss how this switch could improve energy- lithium-ion battery is by far the most effective option in
density by a factor of ten; however, during the charging and electric vehicles, a growing market. The future of the electric
discharging cycle, silicon expands over four times its initial vehicles market is heavily reliant on improving batteries to
size, which leads to detachment from surrounding electrical yield better driving range and reduce cost. When compared to
connections and pulverization of the silicon anode. Over time, NiMH batteries, there are several key advantages of lithium-
this decreases efficiency, lifespan, and charge capacity. ion batteries. Although they have similar energy storage,
Currently, silicon is used in small amounts with the carbon NiMH batteries are much heavier and have shorter lifespans,
graphite anode to improve energy-density, but it is difficult to usually caused by the memory effect, which limits the
add more silicon without managing the anode’s expansion. battery’s future charge capacity when recharged before the
This paper will evaluate possible methods to incorporate existing charge is completely used [2]. The memory effect has
more silicon into battery anodes. The primary focus will be consequences, especially in electric vehicles. If the battery is
on the use of various self-healing polymers to create a binder not drained of all charge before recharging repeatedly,
or casing that restricts the silicon’s expansion. During crystals begin to form and reduce the NiMH battery’s charge
experimental trials, batteries using self-healing binders have capacity [3]. When an electric vehicle is charged after each
shown the potential to endure many charge and discharge use without a periodic complete discharge, the crystallization
cycles, while taking advantage of silicon’s charge capacity occurs. This effect also occurs if the battery is overcharged.
advantage over graphite. Other methods to make silicon This phenomenon is known as the memory effect because it
anodes a possibility will also be considered. This paper will is the result of the battery remembering previous energy
focus on comparing methods of integrating more silicon into output and not delivering more than that on subsequent uses.
anodes with the results compared to carbon graphite anodes NiMH batteries have a specific energy of 50-64 Wh/Kg,
and will evaluate the impact of silicon anodes with a focus on but lithium-ion batteries have a specific energy of around 90
the application for electric vehicles. Wh/Kg. Lithium-ion batteries have a specific power twice
that of the NiMH battery. Predictions by Aditya Prabhakar, a
Key words- carbon graphite anode, electric cars, lithium-ion graduate student at Missouri University of Science and
battery, silicon anode, self-healing polymer Technology, and Mehdi Ferdowsi, a professor researching
plug-in hybrid electric vehicles at Missouri University of
Science and Technology, state that the switch from NiMH to
lithium-ion batteries provides a 40-50% weight reduction, a
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20-30% battery volume reduction, and an increase to graphite’s charge capacity of 372 mAh g-1. The result is a
efficiency [4]. battery that can store much more charge.
Additionally, lithium-ion batteries may eventually be
the cheaper option over time. In 2007, the NiMH battery was LIMITATIONS OF SILICON ANODES
cheaper, but the price of nickel has been rising since 1958.
Rising nickel price combined with an increasingly efficient The problem with using a pure silicon anode is that
mass production of lithium-ion batteries in gigafactories during the charging and discharging cycle, the anode expands
could result in a turning point in pricing [5]. Cost is a massive over four times its initial size. This is due to an improved
consideration for electric vehicles. It is estimated that the lithiation ability over graphite. For every one silicon atom, 4.4
battery cost for Tesla Model 3 is around 37% of the vehicle lithium atoms can be bound to form Li22Si5 [9]. For every one
cost. Taking advantage of economies of scale for production carbon atom, .17 lithium atoms can be bound to form LiC 6.
while nickel prices continue to rise is important. Lithium-ion The difference in ratios is the main cause of silicon’s immense
batteries also have a longer lifespan with a typical life of 500- expansion compared to carbon. This expansion can cause
1,000 cycles, rather than 300-500 cycles for NiMH batteries reduced contact with the electrode and other connectors,
[2]. In this case, the lifespan is defined as the number of which reduces efficiency, and damages the silicon in the
charging cycles before dropping below 80% of the initial anode, which shortens the lifespan and reduces charge
capacity. NiMH batteries also experience up to 30% self- capacity. This also causes an unstable solid electrode interface
discharge per month, while lithium-ion batteries experience (SEI) layer to form on the anode [10]. This occurs primarily
10% self-discharge per month. Since electric vehicles may sit during the first charging cycle but continues to affect the
between charges, this is an important metric. battery through subsequent cycles. The formation of an SEI
In application, such as electric vehicles, these effects are greatly reduces the charge capacity. This creates internal
amplified due to the scale of the batteries required for electric resistance. Reducing the SEI formations is an important
cars. Because of this, lithium is essential in current batteries. consideration for developing a silicon anode. This is a
Attempts at improving batteries further would require total manageable problem, though. Fluoroethylene carbonate is a
changes in either composition, such as solid state batteries, or common additive to the electrolyte of a battery. Its presence
utilizing different chemistries. These ideas are far from being creates a thinner SEI formation on the anode with a lesser
cost-effective and require more research. Thus, when impact on the battery’s efficiency. Thus, being able to control
improving batteries, the next logical step is to look at the the silicon’s expansion or minimize the effects becomes the
anode. focus for further analysis.
Graphite anodes are currently the most popular choice
for the lithium-ion anode. These anodes are low-cost, long- SELF-HEALING POLYMERS
lasting, and utilize a relatively high reversible capacity of 372
mAh g-1 [6]. So, further improving the graphite anode could One method of restricting silicon’s expansion during the
be crucial for technological advancements. charging and discharging cycle is by using self-healing
polymers as a binder to limit the expansion [8]. Self-healing
NEW ANODE TECHNOLOGY materials are defined as having the ability to heal damages
automatically and autonomously, or without human
One current procedure for improving batteries is adding intervention [11]. Further, there are intrinsic self-healing
small amounts of silicon to improve performance. George polymers that require a stimulus to be activated [12]. Their
Crabtree, director of the Joint Center for Energy Storage counterpart, extrinsic self-healing polymers, utilize a healing
Research, estimates that upwards of 10% of current lithium- agent that is encapsulated and embedded into the polymer
ion anodes are silicon [7]. In 2015, Elon Musk stated that the during the manufacturing stage. Intrinsic and extrinsic
Tesla Model S would use silicon in batteries to improve the systems are both currently in use as self-healing polymers for
driving range by six percent. Small improvements to current anodes.
technology by using silicon have already shown immense The process of self-healing, regardless of the type,
potential impact when applied to electric vehicles. occurs in three stages [13]. First, a triggering must occur that
Based on current lithium-ion batteries, developing begins the process. This stage is a direct effect of the damage
methods to increase the amount of silicon in the anode is a incurred. The second stage is the transport of materials to the
clear pathway toward an improved battery capable of damaged site. The final stage is the resulting chemical
sustaining technological growth. Compared to the current reaction that heals the damage. This final stage is where the
graphite carbon anodes, pure silicon anodes could various types of self-healing polymers vary. The process of
theoretically increase charge capacity by a factor of ten [8]. capsule-based self-healing is extrinsic and limited to one use
Silicon has a charge capacity of 4,200 mAh g-1, compared to in theory. Capsules are embedded in the material, so a damage
to the material ruptures the local capsules and releases a
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healing agent. Additionally, vascular self-healing materials
rely on a network of capillaries that allow the healing agent to
flow throughout the material in an extrinsic system. This
concept can have multiple uses, and it also has the benefit of
being able to inject more healing agent to the system. Last,
an intrinsic system may use intermolecular forces, such as
hydrogen bonding in organic compounds. Because many of
these intrinsic systems use reversible reactions, the self-
healing capabilities are not limited to one use. Intrinsic
systems are the most popular option for creating a binder that
serves to contain the expansion of the silicon anode because
cracking occurs everywhere on the binder.
Figure 1 [14]
HOW SELF-HEALING POLYMERS WORK Benefit of a self-healing binder surrounding a
WITH SILICON ANODES silicon anode
Figure 1 shows the benefit of the self-healing polymer
Since there are clear, quantitative benefits to using a
used in the study compared to traditional polymer binders,
silicon anode, the next step is to evaluate various methods to
such as polyvindylidene fluoride (PVDF), sodium
make the silicon anode viable, and to balance the benefits of
carboxymethyl cellulose (CMC), and alginate binders, each
improved charge capacity with charge retention. For intrinsic
common in graphite anodes. These do not need to expand as
systems, the self-healing polymers each rely on different
much due to graphite not experiencing expansion to the same
intermolecular forces and dynamic bonding between silicon
extent as silicon. They can only be stretched to 10%, 4%, and
nanoparticles and the organic binder. They all have similar
2%, respectively. This means that none of them are a
healing capabilities, so comparisons based mainly on
reasonable option for use with silicon anodes. Wang’s
quantitative data are fair.
composite polymer can be subjected to 100% stretching. The
anode used in trials has a charge capacity of 2,617 mAh g-1.
Analysis of Hydrogen Bonding
This is six times larger than the theoretical capacity of
graphite. After 20, 50, and 90 cycles, the anode coated in
Wang et al. describes a silicon microparticle (SiMP)
Wang’s composite experienced 100%, 95%, and 80%
anode with self-healing properties that is readily available,
capacity retention, respectively. PVDF, CMC, and alginate-
low-cost, has a life cycle ten times longer than state-of-art
coated anodes had 14%, 27%, and 47% capacity retention,
anodes made from SiMPs, and retain a capacity upwards of
respectively, after just 20 cycles. This research lays the
3,000 mAh g-1 [14]. The self-healing binder relies on
groundwork for self-healing polymers providing significant
hydrogen bonding in this case. The anode in this experiment
improvements in lifespans for batteries. Based on the
is 50% silicon by weight, which is an immense improvement
improved life cycle of this composite over binders used with
over the projected 10% silicon by weight currently in lithium-
graphite anodes, it will now become the benchmark for future
ion batteries. The self-healing coating uses a stretchable layer
comparison.
of self-healing polymer with dynamic bonding and
conductive carbon black nanoparticles. This creates a
Analysis of Ionic Bonding
repeatable and autonomous healing process with conductive
properties. The researchers use a synthesized, randomly-
Kang et al. takes a different approach to the development
branched hydrogen-bonding polymer. The hydrogen bonds
of the self-healing binder [8]. Kang references various studies
are dynamic in this case. Figure 1 depicts the intrinsic self-
where dynamic ionic bonding has shown usefulness in self-
healing system compared to traditional binders used with
healing materials. Kang and his team developed a polymer
graphite anodes. The self-healing binder keeps the silicon
made with amine functionalized silicon (Si-NH2), carbon
interlocked to preserve lithiation ability and conductivity.
black as a conductive filler particle, and poly(acrylic acid)
Through this process, the anode is healed and maintains its
(PAA). These are mixed with water and stirred. Once the
charge capacity over longer durations.
mixture is dried, the electrode is formed. Kang proves the
ionic bonding of ammonium carboxylate salt at the boundary
between silicon nanoparticles and PAA. The created Si-
NH2/PAA anode relies heavily on this ionic bonding, which
can be increased by a heavier coating of amine groups.
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The initial Coulombic efficiency of the Si-NH2/PAA that is injected into the silicon anode [15]. This is an extrinsic
anode is 75%. For CMC and PAA binders without the amine system with vascular characteristics. Although more
functional group, the initial Coulombic efficiencies are 70% restrictive on charge capacity than the binders, the proposed
and 76%, respectively. Last, the researchers used a control of anodes are still an improvement over graphite anodes. The
silicon nanoparticles functionalized with surface methyl claimed benefits are increased life span due to the alloy
groups and a PAA binder. The addition of methyl groups possessing self-healing properties, reduced stress on the
limits the intermolecular forces to being weak van der Waal anode due to the injection being liquid, and improved
interactions. For the control, the initial Coulombic efficiency conductivity compared to the self-healing polymer binders.
is only 58%. The theory is that nanostructures have inactive elements that
Next, the researchers cycled the different batteries at a contribute extra weight, extra volume, and unnecessary
current density of 2.1 A g-1. The Si-NH2/PAA results show a reactions with the electrolyte. To support the claim of a longer
capacity retention of 80% at 400 cycles. The discharge life span, Wu states that there is no obvious decay over 1,000
capacity was 1,177 mAh g-1 at the end of 400 cycles. For the cycles. Although this anode is only 33% silicon by weight, it
CMC and PAA binders, where only hydrogen bonding is is impressive to control the expansion to achieve such a
possible with the silicon, the capacity retention is only 35% reduction in capacity fade over many more cycles than studied
after 400 cycles. Last, the control group shows capacity with Kang’s anode. The liquid metal, a silicon-gallium alloy,
retention of 5% after 400 cycles. The resulting conclusion is is more conductive than carbon materials or organic
that stronger intermolecular forces between the silicon polymers. Adding silicon to a more conductive liquid metal
nanoparticles and the binder yield improved capacity material than graphite yields better charge capacity and adds
retention due to the ability of the binder to interact when the healing effects. To compare to Kang’s study, however, when
silicon fractures. Thus, ionic bonding yields the best healing used at 2 A g-1, the battery has a charge capacity of only 670
effects on the anode. mAh g-1. Being greater than the theoretical capacity for pure
In addition, the Si-NH2/PAA contained 10% graphite anodes, this is an option to consider due to its
fluoroethylene carbonate by weight to control the SEI longevity; however, from a charge capacity perspective, the
formation. This reacts with the amine functional groups in the anode in Si-NH2/PAA anode is a much better option. Over
Si-NH2/PAA binder. The SEI is stable, and the resistance due 1,000 cycles, the Coulombic efficiency is 99.3%. The
to the SEI is consistently around 40 ohms. Without the amine minimal capacity fade over a long period of use is vital to
functional group and the resulting ionic bonding, the being useful in application.
resistance peaks at roughly 180 ohms. Since much of the Wu ran another trial with 66% silicon by weight. This
capacity fade from SEI occurs in the first cycle, the Si- resulted in an initial capacity of roughly 2,000 mAh g-1, but
NH2/PAA binder has minimal initial fade compared to its after just 300 cycles, the charge capacity dropped to 584 mAh
counterparts without the amine functional group. This is g-1. Since Wu’s 66% silicon by weight is similar to Kang’s
important for longevity and consistency in the battery. 60% silicon by weight anode, a direct comparison is fair. The
Comparing this to Wang’s the aforementioned study liquid metal has significant capacity fade. After 400 cycles,
shows the importance of the Si-NH2/PAA binder. First, Kang’s battery had over twice the charge capacity as Wu’s
Wang’s composite was studied with a .4 A g-1 current density battery did after 100 fewer cycles.
[14]. This is much lower than the current density used by In this sense, Kang’s Si-NH2/PAA anode is the better
Kang (2.1 A g-1). The lower current density reduces the option for electric vehicle application in terms of driving
silicon’s expansion and the deleterious effects resulting from range, but Wu’s battery with 33% silicon by weight may be
prolonged use. Therefore, maintaining 80% capacity retention overall better in application for electric vehicles due to the
with the Si-NH2/PAA binder after 400 cycles at the higher minimal capacity fade after 1,000 cycles. Increased longevity
current density is much more impressive than 80% after 90 means less maintenance is necessary regarding the vehicle’s
cycles for the first composite at the lower current density. batteries, but driving range is sacrificed.
Furthermore, the anode in Wang’s study was 50% silicon by
weight; the anode in Kang’s study was 60% by weight. With CONSIDERING SILICON ANODES
more silicon in the anode, resulting in more fracturing, but
overall improved longevity, Kang’s Si-NH2/PAA binder is a
WITHOUT A POLYMER BINDER
clear improvement on composites utilizing hydrogen
bonding. Because silicon anodes pulverize or show signs of
damage after the first cycle, finding data to compare for a
Liquid Metal: An Alternative to Polymers benchmark is difficult. However, Dose et al. discusses this in
“Capacity Fade in High Energy Silicon-Graphite Electrodes
Wu et al. describes another type of self-healing silicon for Lithium-Ion Batteries.” They use approximations to
anode that uses liquid metal, an alloy of gallium and silicon, isolate the silicon’s decay. In a 15% silicon by weight graphite
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anode with an initial charge capacity of roughly 860 mAh g - charge densities, and typically require little to no
1
, the capacity retention after 100 cycles is around 75% [16]. maintenance.
Over a test of 1,000 cycles, the capacity retention is down to However, as previously examined, most current lithium-
around 41%. From the battery used in the study, Dose ion batteries use graphite anodes. These batteries need to be
assumes that the graphite components had “little fade,” so the improved in order to be more efficient and cost-effective for
silicon components are assumed to account for the decline the mass market. In reference to an article by the Royal
from 61% capacity retention after 400 cycles to 46% capacity Society of Chemistry titled “Lithium-ion Batteries: A Look
retention after 1,000 cycles. into the Future,” to ensure a driving range of 150 km with a
Isolating the data from 400 cycles and comparing to the single charge for a common sub-compact passenger car, the
battery with a polymer binder yields interesting results. The battery would have to weigh over 160 kg based on the current
unrestricted silicon’s 61% capacity retention, observed by average lithium-ion energy density [19]. This is impractical
Dose, compared to 80% capacity retention, observed by when options exist to make the batteries more efficient. A
Kang, if a self-healing binder is used appears to be an battery with a much higher energy density would be the ideal
insignificant change. It is important to note, though, that as solution. Researchers have found that replacing the graphite
the silicon becomes less efficient in the anode at lithiation, anode with a silicon anode can increase the battery’s capacity
there is reduced volume expansion, which leads to less by more than ten-fold and, thus, greatly increase the energy
cracking and a steadier charge capacity over time [8]. Even density, which allows for weight reduction of the battery
more impressive, the anode used in Kang’s study was 60% pack. However, a silicon anode on its own is not the perfect
silicon by weight, rather than 15%. The battery used in Dose’s solution. Testing has found that during the lithiation
study is similar, albeit slightly improved in terms of silicon electrochemical process, the anode expands and contracts
percentage by weight, to current lithium-ion batteries. which causes cracks, pulverization, and eventually the battery
Maintaining a higher charge capacity, despite increasing the is no longer reliable to function.
silicon composition in the anode, shows a massive In an interview with Elon Musk, the founder of Tesla,
improvement resulting from the binder. When compared to he proposed that by the year 2035, electric vehicles will
the liquid metal alternative, the results are also similar. The dominate our roads [20]. Society will likely see these changes
liquid metal battery has a charge capacity to Dose’s battery come to fruition, but researchers must first improve on
and much less capacity fade. Compared to traditional graphite making electric cars more practical and affordable to
anodes with trace amounts of silicon possible, these methods consumers. At the moment, affordable, yet advanced, electric
of incorporating silicon into anodes are successful. They have cars, such as the Chevy Bolt, take several hours to reach full
improved charge capacity and have proven to be long-lasting charge. The Chevy Bolt still takes around ten hours for it to
in tests. The silicon anode is viable when coupled with the reach full charge [21]. For many people, this is impractical
benefits derived from methods to control and contain its compared to the ease of filling up a gasoline car in just a few
expansion. Although these methods are in the study phase and minutes, especially for long trips. The Bolt’s power comes
likely far from being cost effective, batteries can be improved. from a nickel-rich lithium-ion battery, which weighs around
Therefore, lithium-ion battery-dependent technology, such as 435 kg and boasts a range of 238 miles from a single charge.
electric vehicles, is indirectly improved. As long as the development of silicon-anode lithium-ion
batteries continues, we could soon see more striking
APPLICATION TO ELECTRIC VEHICLES performance from electric cars at more affordable prices.
These improvements could open up a wider variety of electric
cars. Budget cars with similar driving range to today’s electric
Currently, around 95% of vehicles rely on the burning vehicles would appear on the market. This would be
of fossil fuels, and transportation is one of the largest sources accomplished by using the improved silicon anode batteries
of CO2 emissions [17]. In fact, 14% of greenhouse gas to increase efficiency and range, reduce weight of the vehicle,
emissions come directly from transportation. As a result, car and reduce the input costs of production. These savings are
manufacturers and scientists have been developing more compounded by the fact that driving with gas is more
sustainable, energy-efficient, and environmentally-friendly expensive than electricity. One study at the University of
vehicles. The most advanced electric vehicles today, such as Michigan by Michael Sivak and Brandon Schoettle analyzes
Tesla’s Model S, rely on lithium-ion batteries, which appear the average annual cost difference for each state [22]. The
to be the best option moving forward [18]. However, current study considers gas prices on December 23, 2017. Given these
batteries have limitations for this application. As formerly prices for each state, they used average data. They assume that
discussed, lithium-ion batteries are more efficient than other gas vehicles get an average of 25 miles per gallon, electric
types of batteries used in electric cars, such as NiMH vehicles consume 33 kWh per 100 miles, and the average
batteries. Lithium-ion batteries charge faster, have higher annual driving distance is 11,443 miles. For simplicity, this
paper will analyze averages of data across the entire United
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States, rather than individual state considerations. The there is a demonstrated potential to improve the driving range
average annual cost of gas consumption is $1,117, while the in smaller vehicles.
average annual cost of electricity consumption is $485. This
yields an annual savings of $632. Therefore, an improvement POSSIBLE ECONOMIC AND LOGISTICAL
on batteries will not only make purchasing electric vehicles
cheaper, it will have annual savings. This decrease in price
IMPACT OF IMPROVED LITHIUM-ION
will make electric vehicles much more viable. As the price of BATTERY IN ELECTRIC VEHICLES
vehicles decreases due batteries improved with silicon
anodes, the savings from using electricity instead of gasoline Improved lithium-ion batteries are predicted to be higher
will help to entice consumers to switch to electric vehicles. in demand in the near future with their use becoming more
From a perspective with driving range being the most common in electric vehicles, as well as consumer electronics.
important benefit, electric vehicles using all of their potential According to the Market Research Engine, the global lithium-
space could lead to massive improvements of driving range. ion battery market is expected to exceed more than $92 billion
Given that many vehicles have limited space available for at a compound annual growth rate of 16.5% [25]. This shows
batteries, the most efficient way to improve driving range is that the market for better batteries, produced cost-effectively,
improving the batteries. This does not require more space has the potential for profit and is bound to open up thousands
dedicated to batteries. As this becomes a reality, public of job opportunities in the future. The goal for producing cost-
transport and long-range semi-trucks may make a drastic effective batteries is reaching economies of scale. Tesla has
switch to electric power. Currently, there are around 1,600 demonstrated some interest in developing the Gigafactory to
electric buses in the United States [23]. However, the L.A. make every step of the process efficient [18]. Tesla’s target is
Metro, for example, stated that the buses were not reliable past to account for around 60% of the world’s production of
100 miles of driving, and some buses even needed charging lithium-ion batteries. Some of the major forces propelling this
after just 78 miles. Making electric buses more viable is market forward are increasing demand for improved batteries
important because electric buses are estimated to save coming from automobile manufacturers, rapidly-spreading
$130,000 over the bus’s lifetime, along with drastically concerns for the environment, which relates to people looking
reducing emissions. Figure 2 illustrates the potential impact into electric cars instead of standard gasoline cars, and
that results even in a switch from hybrid buses to electric applications of lithium-ion batteries in other consumer
buses. This switch from diesel-hybrid buses to battery electric electronics. With all of this in mind, it appears that the market
busses, as seen on the graph, halves the resulting emissions. production of lithium-ion batteries could grow to a massive
extent in the coming years.
One of the main forces holding back the market for
lithium-ion batteries is the high cost of production. Electric
cars are currently more expensive than gasoline models due
to the high cost of producing batteries. Given the high cost
and the fact that there are only four fully electric vehicles that
can currently surpass ranges of 200 miles from a single
charge, the average consumer is not inclined to purchase an
electric vehicle [5].
The switch to electric vehicles indirectly affects the
market for oil, leading to more economic changes. The
possibility of increased dependence on electric vehicles,
especially in the United States, could lead to decreased
dependence on foreign oil. Just considering electric buses in
China, there was a reduction of 233,000 barrels of oil [23].
Figure 2 [23] Forecasts for the world by Eco Watch show that this reduction
Emissions from buses over their lifetime could increase in magnitude to 7.3 million barrels of oil per
day. Although this is just below 10% of the daily market for
There are already plans for improving the viability of oil, a change of this magnitude would have immense effects
electric vehicles beyond consumer cars. Tesla plans to release on worldwide economic relations. For the United States
semi-trucks with 300 and 500-mile driving ranges [24]. specifically, a continuing dependence on foreign oil increases
Accomplishing this, in turn, shows viability for buses and the deficit. Instead of borrowing to reinvest, around 27% of
other heavy-weight vehicles. By showing the potential for foreign oil is being used for passenger vehicles as of 2017
improved driving range in larger, heavy-weight vehicles, [26]. This is not economically viable because running a deficit
in a country’s current account, used to quantify imports and
University of Pittsburgh, Swanson School of Engineering 6
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exports account, to only increase a temporary standard of SOURCES
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