TESLA battery chemistry driving electric car revolution

HOW BATTERY CHEMISTRY IS DRIVING
TESLA CAR REVOLUTION?
Chemistry of new batteries for electric cars of TESLA
LALIT JAYANTI
R.NO 161200, PRODIGY SR, KOTHRUD BATCH, STANDARD VIII, MILLENNIUM NATIONAL SCHOOL

How battery chemistry is driving TESLA car revolution? 1
Acknowledgements
I take this opportunity to express my profound gratitude and deep regards to my teachers, parents and
friends, for their guidance, valuable information and cordial support which helped me in completing this
project through various stages. There is a wealth of information on the internet by way of description of
the process, analysis and various case studies. I wish to thank all those who have helped me indirectly, in
my project but are too numerous to mention individually. I full heartedly thank the institution for giving
me this opportunity to create this report and thus gain knowledge.

Table of Contents
Acknowledgements.......................................................................................................................................1
Table of Contents..........................................................................................................................................2
Table of Figures.............................................................................................................................................3
Preface ..........................................................................................................................................................4
1. Introduction ..........................................................................................................................................5
A. Aim....................................................................................................................................................5
B. Present Problems..............................................................................................................................5
C. Present Solutions ..............................................................................................................................6
2. Chemistry of Electrochemical Batteries................................................................................................9
A. Basics of Electrochemical Batteries ..................................................................................................9
3. Lithium Ion Cells..................................................................................................................................13
A. Components....................................................................................................................................13
B. Discharge Mechanism.....................................................................................................................13
C. Charging Mechanism ......................................................................................................................14
D. Intercalation....................................................................................................................................14
E. Lithium Ion Cell Chemistries ...........................................................................................................16
4. Summary.............................................................................................................................................20
5. References ..........................................................................................................................................22

Table of Figures
Figure 1 Primary Cell Layout .......................................................................................................................10
Figure 2 Secondary Cell Layout...................................................................................................................11
Figure 3 Energy Density of some Secondary Cells ......................................................................................12
Figure 4 Li-ion Cell: Discharge Mechanism .................................................................................................13
Figure 5Li-ion Cell: Charging Mechanism....................................................................................................14
Figure 6 Forms of Intercalation...................................................................................................................14
Figure 7 Li-ion Cell Chemistries...................................................................................................................16
Figure 8 Expansion of Silicon Electrode ......................................................................................................17
Figure 9 Key Parameters of Different Cell Chemistries...............................................................................21

Preface
Today we use automobiles, vehicles such as cars, scooters, bikes etc. for all our travels and transport and
their numbers are growing day by day. Traditionally they use fossil fuels like petrol and diesel. The
effluents from these vehicles contain Hydrocarbons, Carbon Dioxide, Carbon Monoxide, Sulphur Dioxide,
Nitrogen Oxide, and secondary pollutants of particulate matter. These pollutants increase global warming
by trapping heat and are a health hazard to humans and animals. So, to prevent these problems and
decrease the pollution caused by cars and other appliances, people have come up with many solutions.
They have developed alternative fuels like CNG (compressed natural gas) and biodiesel, on the other hand
people have developed better car components like hybrid engines and completely electrical vehicles. All
these methods are ideally designed to decrease pollution and improve usage of energy efficiently.
Electric cars work purely on energy derived from a set of battery cells fixed in it. In this way, almost no
pollution is caused and many people are developing and improving these technologies. But this solution
as good as it sounds it has its own draw backs like more cost, less range, less payload carrying capacity
and a few other factors. All these factors depend on the cost, weight, amount of energy stored, charge
and discharge times of batteries used to provide energy. What amount of energy a cell can produce and
how fast it can charge or get replenished with energy are solely dependent on the cell’s chemistry. There
are many people and companies trying to alter various elements of these cells to overcome those
problems.
Tesla Motors Inc is a pioneer of such advances and is one of the most successful company in achieving
solutions for those above-mentioned drawbacks.
This study aims to explore and learn about those cells and their various components and interactions.
Along with that we shall see what improvements Tesla has done to those cells to make them work so
efficiently, since their cars which incorporate that newer technologies might replace the traditional ones.

1. Introduction
A. Aim
The project aim is to understand the working of Electrochemical batteries in general and the batteries and
technologies developed by Tesla Motors Inc. in particular.
This will be done by observing them from all perspectives. That is by understanding their chemistry,
efficiency, pros and cons, use in the real life and world (practically and theoretically). A few of these
features will be compared to hydrocarbon fuels, to help in understanding its efficiency and advantages as
well as disadvantages.
But for understanding why the batteries are being developed in certain way we have to understand their
background. That is, we have to know the present problems and present solutions and then we can move
to the new solutions.
B. Present Problems
Today cars and other such vehicles are used a lot and their number is increasing day by day. And cars burn
fuel to generate energy which makes it perform its functions. Cars generally use fossil (hydrocarbon) fuels
when it is burnt it generates electricity but in turn gives out harmful gases like Carbon Monoxide, Sulfur
Dioxide and Nitrogen Dioxide. This causes a lot of pollution and harms the surrounding environment and
can harm animals and humans by causing respiratory problems, eye infections and other such bodily
disorders and can also kill plants as they can’t live in such environment. And also, these cars are also not
so efficient too.
Since normal cars use engines which work on internal combustion systems which incorporate pistons
which rise and fall when the fuel is burnt under them which causes the air to expand thus pushing the
piston up and down. This movement of the piston powers the car. But the fact of matter is that when this
fuel is burnt only 20% of the energy produced is actually helping in moving the car and perform its various
functions. Rest of it is lost in form of heat, light and sound. This only increases the fuel consumption of
the car.
All in all, this is not a very efficient method. However there have been attempts to improve this critical
state. (present solutions) Which we will discuss in short in the next part.

C. Present Solutions
The alternatives that will be discussed are as follows: hybrid engines, alternative fuel (CNG, biodiesel) and
electric cars.
I. Hybrid Engines
This solution is actually an engine which is in short, a mix of a combustion engine and electric batteries. It
uses technology which converts ‘lost’ energy (in form of heat when the car comes to rest and then again
goes to a state of motion) is converted to electricity and is reused to help in working of the car again. This
is sometimes referred to as regenerative braking. This reduces the fuel consumption by about 25%. Also,
this converts almost half of the ‘wasted’ energy to usable energy. Of course, this alternative has its own
problems, that is, it still causes pollution no matter how much energy it saves and also it is extremely
difficult and costly to use it in all vehicles. Also, it does not increase its fuel efficiency to an extent at which
point there is no harm to the environment either. Here is a chart for better understanding.
MODEL CARRYING CAPACITY MAX SPEED MAX RANGE
Toyota Prius 5 adults 180 km/h 946 Km
Honda Accord 5 adults 189 km/h 1219 Km
II. Alternative fuel (CNG: - compressed natural gas)
It is said to be a cleaner fuel as it causes comparatively less pollution. But even though it does less pollution
it is after all a fossil fuel. And it can also get exhausted too. Also, the tanks which contain the gas take up
a lot of space. This reduces the range as you can’t carry enough fuel to get required range. Also, there is
scarcity of this fuel as it is a fossil fuel and is expensive too. Along with that maintenance is also required
frequently. Here is a table of cars/ vehicles for better understanding.
MODEL CARRYING CAPACITY MAX SPEED MAX RANGE
Honda Civic CNG 5 adults 120 km/h 354 km
Ford F 150 4 adults 200 km/h 400 km
Now that we have glanced through this short list of alternatives we see that these methods are not as
effective as they were supposed to be and still cause pollution too.
There have been other advances to this problem and those solutions are not based on improving the
engine or use some other kind of hydrocarbon fuel, instead make the car in such a way that it won’t need
hydrocarbon fuel and it its place they will use electricity from batteries which are fixed in the car itself. It
is said that this technology is very effective in fact more effective than the present solutions. Many
companies are researching and releasing cars using only electricity. Among them one of the pioneers is
Tesla Motors Inc. Working of their new innovative use of electrochemical batteries and its chemistry and
its use in an (electric) car as well as its efficiency and use will be discussed in the next part.

III. Electrical Vehicle
These are vehicles that work solely on energy derived from electric cells which use various principles of
electricity and chemistry also termed as electrochemistry. Here is a list of cars which work on these cells.
LIST OF CARS (EXCLUDING TESLA CARS)
MODEL CARRYING
CAPACITY
CHARGING TIME MAX SPEED MAX RANGE
Chevrolet Bolt EV 5 adults 30 min to 2 hours 150 km/h 132 Km
Mahindra e2o 4 adults 1 to 5 hours 82 km/h 80 to 120 Km
Ford Focus Electric 5 adults 3 to 20 hours 135 km/h 122 Km
Mercedes-Benz B-Class
Electric Drive
5 adults 9 to 4 hours 160 km/h 200 Km
Nissan Leaf 5 adults 30 min to 20 hours 150 km/h 121 to 200 Km
In the chart, it is clearly seen that compared to other vehicles these have less range, less speed, less
carrying capacity and also on top of that these cars take a lot of time to charge so to overcome these
problems Tesla has come up with improved cells which use better components like Silicon, Lithium Nickel
Manganese Cobalt Oxide and so on to make cells more efficient.
TESLA CARS (based on supercharging)
MODEL CARRYING
CAPACITY
CHARGING TIME MAX
SPEED
MAX
RANGE
Tesla Model S P85 kW·h 5 adults + 2 kids battery swap in 1.5
minutes. Or 40 min
214 km/h 426 km to
480 km
Tesla Model S 85 kW·h 5 adults + 2 kids battery swap in 1.5
minutes. Or 40 min
225 km/h 426 km to
480 km
Tesla Model S 60 kW·h 5 adults + 2 kids battery swap in 1.5
minutes. Or 40 min
193 km/h 335 km to
470 km
Tesla Model X P90 kW·h 7 adults 40 min 249 km/h 402 Km
Tesla Model X 90 kW·h 7 adults 40 min 249 km/h 414 km to
499 km
After looking at this table it is seen that TESLA cars have a higher range as well as low charging time, more
carrying capacity and higher speed too. Also, these cars seem more efficient in almost all factors.
What makes this possible? What is so special about these TESLA cars?
All of this is possible due its ingenious design of car, its battery, and its proper use. Along with this it does
extremely low or negligible pollution when driving it.
We shall see this in the next part and understand the chemistry of this battery and how it is compatible
with this new technology of supercharging (as it is observed in the table that it takes less time to charge
than other cars. The method that is used to charge the cars is called supercharging.) and also its use in an
electric car. A graph is given after this to help clear the concept

Type Diesel Petrol CNG Hybrid Electric
Consumption
(Equiv Liters of Crude /Year)
1781 1447 16 1050 32
Emission (gram/Km) 478 446 351 288 46
Cost – Price (Rs Lakh) 16.5 11.0 18.3 16.9 25.5
Cost – Fuel/Year (Rs) 119000 154000 77350 77000 38500
Efficiency (KMPL equiv) 14 15 13 21 48
Range (Km/charge or fill) 397 359 154 479 120
Pickup (0-100 KMPH in sec) 8 8.7 10.7 9.8 10.2

2. Chemistry of Electrochemical Batteries
Here we will be studying a basic electrochemical cell (the galvanic cell, the first cell of its kind), then we
will move on to newer models like Lithium-ion battery and other such batteries and then we will study
the alterations made by Tesla. Inc to the traditional cells to obtain a very efficient cell.
A. Basics of Electrochemical Batteries
It is a device which derives electricity from chemical reactions (REDOX reactions) inside the cell. It is also
termed Voltaic cell or Galvanic cell, after its inventors Alessandro Volta and Luigi Galvani, from which the
first one who was an Italian scientist who studied the fields of physics and chemistry, and he also
discovered methane, volt and voltmeter. And the latter was a physicist and also a philosopher.
I. Components of an electrochemical cell
To understand the cell, we will need to understand its components and their job.
Electrodes: these are conductors of electricity through which electricity enters or leaves. Basically, there
are two types of electrodes, the cathode and the anode. The cathode is referred to that terminal where
oxidizing takes place and the anode where reducing takes place. Here the cathode is taken to be the
positive terminal and the anode to be the negative terminal.
Electrolyte: it is the medium where the redox reactions take place and where the ions that is cations and
anions separate. Cations carry the relative opposite charge of the cathode and are attracted towards it
and it is same for the anions but they are attracted to the anode.
Oxidizing agent: it refers to a substance which gets reduced and oxidizes substances in it or in contact with
it. (in cells, it consists of the salt of the metal used in cathode- which disassociates into positive species of
metal and negative species of the other counterpart) e.g. CuSo4  Cu+2
+ SO4
-2
Reducing agent: it refers to a substance which gets oxidized and reduces substances in it or in contact
with it. (in cells, it consists of the salt of the metal used in anode- which disassociates into positive species
of metal and negative species of the other counterpart) e.g. ZnSo4  Zn+2
+ SO4
-2
Porous disk/Salt bridge: since cells are separated into half- cells the anions which form in the oxidizing
agent (one of the electrolytes) need to get to its negative counterpart present in the anode which is in the
other half-cell a medium is required this medium is the porous disk or in some cases a salt bridge which is
filled with a gel which allows ion transfer from one half cell to the other half cell.

II. Electrochemical cells
There are two types of cells Primary and Secondary cells.
1. Primary cells
A primary cell is a battery that is designed to be used once and discarded, and not recharged with
electricity and reused. In general, the electrochemical reaction occurring in the cell is not reversible,
rendering the cell un - rechargeable.
In this cell the disassociated species of metal present in the Oxidizing agent having affinity for electrons
will attract electrons from the anode and turning an atom in the anode into an ion and this thus dissolves
in the solution of the reducing agent meanwhile the electrons will pass through the wire generating
electricity and then go through the cathode and then gets passed to the metal ions in the solution and
then they become atoms and then settle on the cathode in a solid state. As this process continues on the
electricity is generated but now the oxidizing agent gains a negative charge due to lack of cations of copper
and the reducing agent solution gains a positive charge as there is an excess of metal ions there compared
to the salt counterpart. Because of this the cell can’t function as it can’t afford to lose more electrons. So,
a salt bridge used which helps in retaining the neutrality of the solution and the process continues until
the anode itself is dissolved into the solution. ( salt bridge has a neutral salt which disassociates into anions
and cations which travel towards opposite charges and maintain neutrality.)
E.g. Zn Cu cell. Half reactions are
Anode: Zn – 2e-
 Zn+2
Cathode: Cu+2
+ 2e-
 Cu
But since we can’t recharge these cells as these reactions are irreversible we have to discard these after
use people have developed new and better cells which can be recharged called Secondary cells.
Figure 1 Primary Cell Layout

2. Secondary cells
These cells also work similarly to the primary cells but instead these cells have a separator or porous disk
in between the half cells instead of the salt bridge. The porous disk allows anion exchange from the
oxidizing agent into the reducing agent so this balances the charge a the oppositely charged particles will
attract the ions and maintain neutrality. And this is extremely useful as we don’t introduce any new ions
(salt ions of salt bridge) we can reverse this reaction by applying external charge.
Well the main idea of the recharging is that a device is connected to the electrodes from which electricity
is passed to give the negative terminal a positive charge this will then produce an oxidizing reaction in the
electrolyte with the negative electrode and turn the accumulated metal on the electrode into ions as they
get oxidized and lose electrons and dissolve into the electrolyte. And the exact opposite happens in the
half cell with the positive electrode instead there is a reducing reaction which causes the metal ions in the
solution to turn into a solid metal which reforms the electrode and both the electrolytes turn into a neutral
state. And the cell can be used again. (here the places of anode and cathode are inverted).
There are many types of secondary cells. Some of these are shown below for characteristics and usage.
a. Lead acid
This is one of the most economical option for larger power applications where weight is of little concern.
The lead acid battery is the preferred choice for hospital equipment, wheelchairs, emergency
lighting and UPS systems.
b. Nickle cadmium (Ni-Cd)
Nickle cadmium cell is a mature and well understood cell but relatively low in energy density. The Ni-Cd
cell is used where long life, high discharge rate and economical price are important. Main applications are
two-way radios, biomedical equipment, professional video cameras and power tools. The Ni-Cd contains
toxic metals and is not environmentally friendly.
c. Nickle metal hydride (NiMH)
The nickel metal hydride cell has a higher energy density compared to the Ni-Cd at the expense of reduced
cycle life. NiMH contains no toxic metals. Applications include mobile phones and laptop computers.
d. Lithium ion (Li-ion)
This is one of the fastest growing battery system. Li-ion is used where high-energy
density and light weight is of prime importance. The Li-ion is more expensive than other
systems and must follow strict guidelines to assure safety. Applications include notebook
computers and cellular phones, cars (EV) etc.
Figure 2 Secondary Cell Layout

e. Lithium phosphate
Lithium polymer cell is a variation of the Lithium ion cell. It incorporates Lithium Phosphate in olivine
structure as electrode. This results in a good energy density and cell life. Applications include power tools
and cars.
f. Lithium polymer (Li-po)
Lithium polymer cells are potentially lower cost version of the Li-ion. This chemistry is similar to the Li-ion
in terms of energy density. This cell uses a polymer electrolyte, where a salt (sodium chloride) and a
polymer (Poly-Ethelene Oxide) are used to make salt complexes and used as an electrolyte. This enables
the cells to have a very slim geometry and allows simplified packaging. Main applications are mobile
phones.
A comparison of energy densities of different secondary cells is shown below. It can be seen that Lithium
based secondary cells have higher energy density.
Figure 3 Energy Density of some Secondary Cells
In the next chapter, we shall study the Lithium-ion based cells which are used in electric vehicles.

3. Lithium Ion Cells
A. Components
Like other Electrochemical Cells, Lithium-ion cells have
Electrodes, Electrolyte and a separator. Usually a Lithium
Metal Oxide is used as Cathode with a Carbon-based
Anode. Electrolytes are usually a Lithium Salt in an
Organic solvent. The characteristics of the cell are
influenced by the choice of these components. We will
first study the mechanisms of charging and discharging
of these Li-ion cells. The half-cell reactions are
Positive Electrode: Li1-xCoO2 + xLi+
+ xe-
⇆ LiCoO2
Negative Electrode: xLiC6 ⇆ xLi+ + xe- + xC6
B. Discharge Mechanism
The electrolyte has Lithium ions (Li+
) and its negative counterpart disassociated in the solution. And it has
Lithium ions stored in the anode using a process that we will understand later (intercalation). And when
we connect the anode to the cathode the metal Oxide having affinity for positive ions will pull the (Li+
)
from the electrolyte through the separator (which prevents short circuit). When the Lithium ions reach
the metal Oxide and get stored there with that the electrolyte suddenly becomes negative as there are
less positive species in it. To maintain stability and neutrality of solution the electrolyte attracts Lithium
atoms from the anode which contains them. This makes the Lithium atom lose one electron but this
electron now having been lost will try to reach an ion and make it stable but since it can’t go through the
separator while the Lithium ion will take the shortest path through the separator. The electron will take
Figure 4 Li-ion Cell: Discharge Mechanism

the longer path that is, it takes the path through the external wire connected and then it gets deposited
in the cathode that is the metal Oxide. This is how electricity is generated in the Lithium ion cell.
C. Charging Mechanism
While charging, exact opposite method to the discharging mechanism takes place. If we interchange the
‘terminals’ of the cell when we place an external source of electricity this results in reducing reaction in
the place of the former anode (now cathode) and thus gains a relative negative charge thus attracting the
(Li+
) from the now anode thus reverses the entire process. And these ions then get stored back into the
graphite through the process of intercalation.
D. Intercalation
Intercalation is the reversible insertion of a molecule (or ion) into compounds with layered structures or
polyanion structure or spinel forms. This plays an important role in the charge and discharge cycles of the
cell. Generally, graphite or metal oxides are used for this processes.
Figure 5Li-ion Cell: Charging Mechanism
Figure 6 Forms of Intercalation

Layered form: The electrode has layers of the electrode material (generally 1 atom thick) over each other
e.g. graphite has many layers of graphene. In between these layers the ions are stored. Examples are
Lithium Cobalt Dioxide.
Spinel form: The electrode here in this case has a crystalline structure with extremely narrow gaps for the
ions to get stored. This is a very efficient method to store more ions and release them when required. This
in turn provides a low resistance but moderate specific energy. Examples are Lithium Manganese Oxides.
Polyanion or olivine form: The electrode here has Nano sheets made of fine crystals which also give out
different anions thus the name polyanion. These store the required ions. Examples are Lithium Ferrous
Oxides.
Now that we know how the Lithium ion cell works, we will now see the variations of these cell chemistries
and also see what Tesla Motors Inc uses from those and why.

E. Lithium Ion Cell Chemistries
Below is given a more detailed chart of various cell chemistries – choices of materials made for electrodes,
electrolyte. These in turn define the charging characteristics, capacity, safety and cost considerations. We
will also study the variations used in Tesla cars (outlined in blue).
Figure 7 Li-ion Cell Chemistries
Varations
Negative
Electrode
Carbon
Graphite Silicon %
Graphene
Lithium Titanate
Cobalt Alloy
Positive
Electrode
Layered Form
Lithium Cobalt
Oxide
Lithium Nickel
Cobalt Aluminum
Oxide
Polyanion
Lithium Iron
Phosphate
Spinel Form
Lithium
Manganese
Oxide
Lithium Nickel
Manganese
Cobalt Oxide
Electrolyte
Lithium Salt
Lithium
Hexafluorophos
phate
Lithium
Hexafluoroarsen
ate
Lithium
Tetrafluorobora
te
Organic Solvent
Ethylene
Carbonate

Now that we have glanced through the variations of various components of the cell we will move to
different types of cells which incorporate these materials in the cells.
I. Variations of negative electrode
a. Carbon
Graphite is used as negative electrode where intercalation of Lithium ions takes place in the graphene
sheets present in the graphite.
b. Silicon
Six Carbon atoms are required to hold together one Lithium ion, but a single Silicon atom can hold 4.4
Lithium ions in place. This enables to have less negative electrode material and helps in storing more of
cathodic material, increasing the voltage, capacity and energy density of the cell. So, less number of cells
are required to run the EV. This reduces the total battery weight of the cars thus enabling it to carry more
pay load. However, as the Lithium ions are intercalated, volume of the Silicon electrode increases by 320%
than the normal 7% increase with only graphite. This poses a problem for the packaging of the batteries.
Also, the repeated expansion and contraction during charging and discharging leads to drastically reduced
cycle life. As the expansion and contraction can damage the surrounding layer and start to break apart.
This also damages the entire cell and can cause reduced energy density and resistance of the cell also
increases as it damages the SEI layer. The SEI layer is what enables the battery to operate in an efficient
and reversible manner. It’s a film composed of electrolyte reduction products that start forming on the
surface of the anode during the initial battery charge. It functions as an ionic conductor that enables
Lithium ions to migrate through the film during charging and discharging. Under typical operating
conditions, it also serves as an electronic insulator that prevents further electrolyte reduction on the
anode. But as Silicon anodes attract the positively charged ions from the dissociation of the metal Oxide,
it forms a layer over the Silicon anode and after repeated contraction and expansion it cracks this layer
and over time this part develops a thick layer of resistive material and damages the cell.
So, Tesla is using very less amounts of this material in their cells and is developing technologies further,
to make the cells more efficient.
Figure 8 Expansion of Silicon Electrode

c. Lithium Titanate (LTO)
The main advantages of using Lithium Titanate (Li2TiO3) electrode in the cell is that it has an extremely
long life, rapid charging, extremely safe. But the disadvantage is that it provides very less voltage and thus
is not suitable to be used by electronic vehicles.
d. Cobalt Alloy
The main advantages of a Cobalt alloy electrode are that it has a very good specific power and moderately
high life. It can give considerable amount of energy but it is not enough for the EVs.
II. Variations of positive electrode
a. Lithium Cobalt Oxide (LCO)
Using Lithium Cobalt Oxide (LiCoO2) as the electrode offers more energy, has a high thermal runaway (thus
safe) but has limited power and also has moderate features.
b. Lithium Nickel Cobalt Aluminum Oxide (NCA)
Using Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2) as electrode offers high specific power, high
voltage but these pros are balanced out by equally dangerous cons of low thermal runaway. This is the
electrode used in Tesla cars with some variations.
c. Lithium Iron Phosphate (LFP)
Using Lithium Iron Phosphate (LiFePo4) has a moderate voltage and considerable life. This electrode has a
high thermal runaway so this makes it very safe too. It is used in security light systems, E-scooters and
other such devices.
d. Lithium Manganese Oxide (LMO)
Using Lithium Manganese Oxide (LiMn2O4) as electrode results in high voltage and also has a high thermal
runaway making it one of the safest cells. But it has a low specific energy and also very less life. It is used
in some Electric Vehicles and E-bikes also.
e. Lithium Nickel Manganese Cobalt Oxide (NMC)
Using Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2) as electrode provides very high specific
energy and high voltage and also has a long life. Also, it has a high thermal runaway making it one of the
safest cells to use. These were also used in Tesla cars.
III. Variations of Electrolyte
Liquid Electrolytes in Lithium-ion batteries consist of Lithium salts in an organic solvent.
Lithium salts typically used are
• Lithium Hexafluoro phosphate (LiPF6)
• Lithium Hexafluoro arsenate (LiAsF6)
• Lithium Tetra fluoroborate (LiBF4)
• Lithium perchlorate (LiClO4)
Organic solvents typically used are
• Ethylene Carbonate (CH2O)2CO
• Diethyl Carbonate OC(OCH2CH3)2
• Dimethyl Carbonate OC(OCH3)2

For the electrolyte to be effective, a high ionic conductivity and low viscosity is needed, but the two
properties are mutually exclusive in a single material. Thus, a combination of Lithium-salts and organic
solvents are used.
A liquid electrolyte acts as a conductive pathway for the movement of cations passing from the negative
to the positive electrodes during discharge. So, a high conductivity at a wide range of temperatures are
required. The liquid electrolyte conductivity is about 10 milli-siemens/cm at room temperature (20°C) and
increasing by 30% at 40°C. Addition of organic solvents improves the conductivity and the range of
working temperature. Tesla is experimenting with different type of electrolytes; current cells use a
combination of above.

4. Summary
Tesla uses the cells that were mentioned above but now they are developing battery technology to
overcome various problems and to overcome the most prominent and critical problem of all pollution and
inefficient fuels. Table below summarizes different properties studied in earlier section.
Chemistry Lithium
Cobalt Oxide
(LCO)
Lithium Manganese
Oxide (LMO)
Lithium Nickel
Manganese Cobalt
Oxide (NMC)
Lithium Iron
Phosphate (LFP)
Lithium Nickel
Cobalt Aluminum
Oxide (NCA)
Lithium Titanate
(LTO)
Short form Li-cobalt Li-manganese NMC Li-phosphate Li-aluminum Li-titanate
Abbreviation LiCoO2 LiMn2O4 LiNiMnCoO2 LiFePo4 LiNiCoAlO2 Li2TiO3
Nominal voltage 3.60V 3.70V (3.80V) 3.60V (3.70V) 3.20, 3.30V 3.60V 2.40V
Full charge 4.20V 4.20V 4.20V (or higher) 3.65V 4.20V 2.85V
Full discharge 3.00V 3.00V 3.00V 2.50V 3.00V 1.80V
Minimal voltage 2.50V 2.50V 2.50V 2.00V 2.50V 1.50V (est.)
Specific Energy 150–200Wh/kg 100–150Wh/kg 150–220Wh/kg 90–120Wh/kg 200-260Wh/kg 70–80Wh/kg
Charge rate 0.7–1C (3h) 0.7–1C (3h) 0.7–1C (3h) 1C (3h) 1C 1C (5C max)
Discharge rate 1C (1h) 1C, 10C possible 1–2C 1C (25C pule) 1C 10C possible
Cycle life (ideal) 500–1000 300–700 1000–2000 1000–2000 500 3,000–7,000
Thermal runaway 150°C (higher
when empty)
250°C (higher when
empty)
210°C (higher when
empty)
270°C (safe at full
charge)
150°C (higher when
empty)
One of safest
Li-ion batteries
History 1991 1996 2008 1996 1999 2008
Applications Mobile phones,
tablets,
laptops,
cameras
Power tools, medical
devices, powertrains
E-bikes, medical
devices, EVs, industrial
security light
systems, E-
scooters
Medical, industrial,
EV (Tesla)
UPS, EV, solar
street lighting
Comments High energy,
limited power.
Market share
has stabilized.
High power, less
capacity; safer than
Li-cobalt; often mixed
with NMC to improve
performance.
High capacity and high
power. Market share is
increasing. Also, NCM,
CMN, MNC, MCN
Flat discharge
voltage, high
power low
capacity, very safe;
elevated self-
discharge,
stationary with high
currents and
endurance
Highest capacity with
moderate power.
Similar to Li-cobalt.
Long life, fast
charge, wide
temperature
range and safe.
Low capacity,
expensive.

Figure 9 Key Parameters of Different Cell Chemistries
This chart represents key characteristics of different cell chemistries for ease of understanding.
The cell chemistry and choices of various elements influence the cell capacity, energy density,
charging/discharging, life span, safety and overall cost. Further advances are being made in increasing
these aspects and eventually replace conventional fuels in an efficient and economical way.

5. References
Books and Articles
• Isidor Buchmann (2004). Batteries in a Portable World Second Edition. Codex Electronics Inc,
• Martin Eberhard and Marc Tarpenning (2006). The 21st Century Electric Car, Tesla Motors Inc.
• D. Sperling and D, Gordon (2010), Electrification of the Transportation System, MIT
Websites
• http://batteryuniversity.com/
• https://chargedevs.com/features/teslas-batteries-past-present-and-future/
• https://en.wikipedia.org/wiki/Lithium-ion_battery
• https://www.technologyreview.com/s/516961/how-tesla-is-driving-electric-car-innovation/
• http://tymkrs.tumblr.com/post/7846476684/Lithium-ion-battery-how-does-it-work
• http://www.epectec.com/batteries/cell-comparison.html
• https://en.wikipedia.org/wiki/Rechargeable_battery
• http://spectrum.ieee.org/nanoclast/semiconductors/materials/potential-of-Silicon-and-graphene-
together-for-liion-electrodes-realized
• https://chargedevs.com/features/tesla-tweaks-its-battery-chemistry-a-closer-look-at-Silicon-anode-
development/

TESLA battery chemistry driving electric car revolution

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