Week 1 Understanding Different Battery Chemistry

Summary:
Lithium-ion batteries are one of the most commonly used batteries in electric vehicles (EVs) due to their specific
characteristics of high energy density, power density, long life and environmental friendliness. With the development of lithium-ion battery technology, various materials have been used in the design of cathodes and anodes to achieve better performance. The LiMn2O4, LiN iMnCoO2,
LiN iCoAlO2, LiF eP O4, and Li4T i5O12 are the five common lithium-ion batteries used in today's commercial electric vehicles. We will review the characteristics of these five lithium-ion batteries and compare them in terms of electrochemical performance and real
applications.

Introduction:

With rising gasoline prices and growing public interest in climate change, battery-powered electric vehicles, hybrid electric vehicles, and plug-in hybrid
electric vehicles have great potential to reduce fuel consumption. Alternative fuel. While deployment is promising, batteries and hybrid electric vehicles also present important technical challenges. High-voltage battery vehicles must meet stringent safety requirements while meeting consumer expectations of range, reliability, and cost goals.
Today's automakers are developing and commercializing fully electric plug-in vehicles with extended range. These BEVs and
PHEVs connect directly to the grid to charge the traction battery. Compared to current commercial hybrid vehicles
, which use a combination of battery and internal combustion engine, BEVs and PHEVs require a significantly improved battery system.
The improved battery system needs 15-50 times more energy storage and should allow more deep discharge of the operating battery. One of the major battery types with the performance characteristics required for BEVs and PHEVs is lithium ion. The performance characteristics of a large battery system are determined by the basic
electrochemical that occurs at the interface of system components at the cell level. The main electrochemical interface of the
cell lies between the anode, electrolyte, and cathode. The choice of anode and cathode determines the voltage, capacitance, and specific energy of the
. The performance requirements of automotive powertrains that utilize lithium-ion batteries determine which specific
embodiment of the battery is required. This section of the report describes the electrochemicals of
lithium-ion batteries available or under development for consideration in lithium-ion battery vehicles. This section also describes candidate materials used for anodes,
cathodes, electrolytes and their electrochemical interactions, as well as the electrical performance, failure modes, and electrochemical levels of the chemical properties of the various cells
. I will explain the dangers in.
"Cells" are the basic components of an electrochemical system.

Cathode: positive electrode; accepts electrons during battery discharge.
Anode: negative electrode; gives up electrons during battery discharge.
Electrolyte: transfers ions between the anode and cathode.
Separator: solid material between the anode and cathode that serves two roles:

Prevents internal short circuiting between the anode and cathode by preventing direct electron flow from the anode to the
cathode.

Provides a path of ionic conduction in the liquid electrolyte within the interconnected porous structure of the separator

For each subcomponent, there are numerous variations in both commercial cells and cells still under investigation. The combination of
each of cathode chemistry, anode chemistry, electrolyte composition and additives, and separator type represents the
's power density, charging scheme, capacity, charge management technology, and range of safety concerns and challenges.

During battery operation (ie charging and discharging), ions travel through the
electrolyte between the cathode and anode, and electrons travel through external circuits. During cell discharge, the anode oxidizes (donates electrons) and the
cathode undergoes reduction (gains electrons). On the other hand, Li + ions move from the
anode to the cathode via the electrolyte. Once loaded, this process is reversed. The electrochemical process that occurs during charging and
discharging is an "intercalation process" in which Li ions become the temporary "guest" of the host electrode without making major structural changes to the electrode. Most of what happens during this process is reversible.

Cathode:
The cathode is a host structure that can reversibly insert and remove lithium ions. In addition to high specific capacitance, high
, and stable voltage for lithium metal, the cathode of the electrochemical cell accepts electrons and ions during cell discharge. The active material of the cathode of the
lithium ion cell consists of a combination of lithium metal oxide or lithium metal phosphate,
polymer binder (polyvinylidene fluoride [PVDF], carboxymethyl cellulose, or styrene / butadiene rubber) and a conductive substance. It has been. Filler (
carbon black). These materials are manufactured using standard inorganic material manufacturing processes. The active material adheres to the metal current collector.

Anode:
The anode of an electrochemical cell emits electrons and ions as the cell discharges. Lithium-ion battery anodes are typically
carbon-based materials. Today, a wide variety of carbons are used as negative electrodes. Common forms include graphene,
graphite, and carbon black. These shapes can be oriented as planes, whiskers, or spheres. Graphite is one of the most commonly used
anode materials. It stores enough lithium in the structure and maintains stability for a long period of time.

Solid Electrolyte Interface (SEI) Layer:

During the first cycle of a
lithium-ion battery, a semi-permanent coating layer called Solid Electrolyte Interface (SEI)
is formed on the anode and cathode. This layer is an important performance feature of lithium-ion technology. This is because the potential of the
graphite electrode is so negative that the Li ions between the carbon layers are expected to react immediately with the solvent of the
electrolyte. SEI is permeable to Li ions, but not electrolytes. Its stability is an important requirement for the long life of the
.



In some cases, lithium titanate is used as the active material for the anode. Since the negative voltage is lower than that of the graphite
anode, Li ions are more stable and less likely to react with the electrolyte. With lithium titanate, no SEI is formed and the
cell is more stable at higher voltages. The table below outlines the anode materials used or under development. The majority of cells use carbon-based anodes, and the other three outlined are primarily in the research phase of development.

Electrolyte:

Electrolyte is a physical medium that allows ion transport between electrodes during cell charging and discharging. The electrolyte for
lithium-ion batteries is either liquid or gel. Lithium batteries use non-aqueous electrolytes because of the reactivity of
lithium with the aqueous electrolytes and the inherent stability of the non-aqueous electrolytes at higher voltages. Liquid electrolyte is a combination of
of solvent and lithium salt and additive solutions that improve cell performance. The liquid electrolyte of the
Li-Ion cell is lithium hexafluorophosphate (LiPF6), which is usually dissolved in a mixture of organic solvents (mainly carbonates) that need to be formulated according to the electrode material used. In gel electrolytes, also known as lithium polymer cells,
monomers are added to the electrolyte and are thermally activated when the cells are assembled. This reaction produces a polyelectrolyte that contains the entire internal shape of the
cell.

Separator:

Separator is a microporous electrical insulation material placed between the anodes. Separator
plays two important roles. First, it prevents an internal short circuit between the anode and cathode by providing a physical non-conductive barrier. Second, it provides a route for ion transport.

What is a Battery?
A battery is a device that stores chemical energy and converts it to electrical energy.
It consists of one or more electrochemical cells with external connections for powering electrical devices such as flashlights, mobile phones, and electric cars.
The chemical reactions in a battery involve the flow of electrons from one material (electrode) to another, through an external circuit.
The flow of electrons provides an electric current that can be used to do work.

Types of Battery
Battery cells are mainly divided into 2 types :
1) Primary cells – Non chargeable cells
2) Secondary cells – chargeable cells –
Primary cells are Non chargeable cells which are used in appliances such as wrist watch, calculator & radio

e.g. Dry cell, Li battery

Secondary cells are chargeable cells which can undergo Reversible chemical process i.e., Electrical energy to chemical energy.
E.g. Lead cell, Ni-cd cell, metal air, Ni metal Hydride, Li ion Battery cells
The reason for using Li ion Battery in many application is because of High energy density.
Energy Density: The energy density is the total amount of energy that can be stored per unit mass or volume. This determines how long your device stays on before it needs a recharge

Battery cells are usually made up of three main components:
1. The Anode (Negative Electrode)
2. The Cathode (Positive Electrode)
3. The electrolytes
During Discharge, The anode is a negative electrode that produces electrons to the external circuit to which the battery is connected.
When batteries are connected, an electron build up is initiated at the anode which causes a potential difference between the two electrodes. The electrons naturally then try to redistribute themselves, this is prevented by the electrolyte, so when an electrical circuit is connected, it provides a clear path for the electrons to move from the anode to the cathode thereby powering the circuit to which it is connected.
During charging, the Li ions move back from cathode to Anode as shown in Fig.1.3.

How does Li-ion Battery work?

Lithium Battery Technologies:

Lithium-ion battery technology is based on intercalation. This is actually adding lithium ions to the host material without significantly changing the structure of the
host. During the discharge cycle, the lithium atom in the anode is ionized and
electrons are removed. Lithium ions travel from the anode across the electrolyte medium, passing through the micropermeable separator between the anode and cathode in
, reaching the cathode, where they recombine with electrons. Lithium
ions are small enough (third after hydrogen and helium), which translates to faster charge / discharge capabilities and a higher charge storage capacity of
per unit mass and volume. The single cell voltage of a Li-ion battery is the energy difference between the Li + ions present in the crystal structure of the two electrodes. In addition to the three key components of the
cathode, anode and electrolyte, an electronic controller that regulates power monitors the discharge current of the
, and battery temperature is also an important and essential part of the lithium-ion battery. The incorporation of this
device means that special safety measures need to be taken to ensure operation.
In a
lithium-ion battery, the lithium atom is split at the anode (-ve). This produces electrons and lithium ions (a positively charged lithium atom). Lithium ions travel through the electrolyte through the electrolyte to the cathode (+ ve). Electrons usually cannot pass through this material. Therefore, the electrons follow different paths to the cathode via an external circuit. This creates a current that can power the device. At the cathode, the electrons meet lithium ions in another chemical reaction. Reverse this process to charge the
battery. Ions and electrons return to the anode.

Specific energy: This defines the battery capacity in weight (Wh/kg). The capacity relates to the runtime. Products requiring long
runtimes at moderate load are optimized for high specific energy.
Specific power: It's the ability to deliver high current and indicates loading capability. Batteries for power tools are made for high
specific power and come with reduced specific energy.
Nominal Voltage: It is the system voltage at which the device is designed to operate. The rated voltage is usually higher than the
nominal voltage to ensure the safe operation of the device.
Cycle: The charge and discharge make a Cycle
The current rate (C): This is used to determine the fast charging capability of a battery.
Thermal Runaway: It is a condition where an increase in temperature changes the conditions which increase the temperature
further, often leading to disaste

Performance: This measures how well the battery works over a wide range of temperature. Most batteries are sensitive to heat
and cold and require climate control. Heat reduces the life, and cold lowers the performance temporarily.

Lifespan: This reflects cycle life and longevity and is related to factors such as temperature, depth of discharge and load. Hot climates accelerate
capacity loss. Cobalt blended lithium ion also usually have a graphite anode that limits the cycle life.
Safety: This relates to factors such as the thermal stability of the materials used in the batteries. The materials should have the
ability to sustain high temperatures before becoming unstable instability can lead to thermal runaway in which flaming gases
are vented. Fully charging the battery and keeping it beyond the designated age reduces safety.
Cost: Demand for electric vehicles has generally been lower than anticipated and this is mainly due to the cost of lithium-ion
batteries. Hence cost is a huge factor when selecting the type of lithium-ion battery.

Types of Li-ion Battery
1) Lithium Cobalt Oxide (LiCoO2) — LCO
2) Lithium Manganese Oxide (LiMn2O4) — LMO
3) Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2) - NMC
4) Lithium Iron Phosphate (LiFePO4) — LFP
5) Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2) — NCA
6) Lithium Titanate (Li2TiO3) — LTO

Below is the Table created to compare different Li-ion battery :

Sl.no.	Li - ion Battery Type			Cathode	Anode	Advantages	Drawbacks	Applications	Structure
1	(LiCoO2) — LCO			Li Cobalt oxide	Graphite carbon	high specific energy	short life span, low thermal stability and limited load capabilities (specific power), Cobalt is expensive	mobile phones, laptops and digital cameras
2	(LiMn2O4) — LMO			lithium manganese oxide	Graphite carbon	lower internal resistance and improved current handling, high thermal stability and enhanced safety	cycle and calendar life are limited	Electric vehicles such as the Nissan Leaf, Chevy Volt and BMW i3, Power tools, medical devices, electric powertrains
3	(LiNiMnCoO2) — NMC			Lithium Nickel Manganese Cobalt Oxide	Graphite carbon	good overall performance and excels on specific energy, lowest self-heating rate	high cost due to cobalt	E-bikes, medical devices, EVs, industrial
4	(LiFePO4) — LFP			Lithium Iron Phosphate	Graphite carbon	high current rating and long cycle life, besides good thermal stability, enhanced safety and tolerance if abused.	higher self-discharge, less specific energy	Portable and stationary needing high load currents and endurance
5	(LiNiCoAlO2) — NCA			Lithium Nickel Cobalt Aluminum Oxide	Graphite carbon	high specific energy, reasonably good specific power, long life span	High cost and marginal safety	Medical devices, industrial, electric powertrain (Tesla)
6	(Li2TiO3) — LTO			lithium manganese oxide or NMC	Li2TiO3 (titanate)	Fast charging, safe, high discharge current of 10C	Low specific energy	UPS, electric powertrain (Mitsubishi i-MiEV, Honda Fit EV), solar-powered street lighting

The table above compares the voltages and typical applications of the six basic lithium battery chemistries. Other characteristics
of these batteries include:
LCO– 200Wh/kg, deliver a high power, but with the tradeoff of relatively short lives, low power ratings, and low thermal stability.
LFP– 120Wh/kg, have long cycle lives and stability at high operating temperatures.
LMO– 140Wh/kg, cathodes are based on manganese-oxide components that are abundant, inexpensive, non-toxic, and provide
good thermal stability.
NCA– 250Wh/kg, offers high specific energy and long cycle lives.
NMC– 200Wh/kg, varying the proportions of the chemical constituents allows the development of batteries optimized as power
or energy cells. Because of its flexibility, it is one of the most successful lithium battery chemical systems.
LTO– 80Wh/kg, lowest specific energy, but can be fast charged, discharged at up to 10-times its rated capacity, and is safe.

Chemical reactions in different Battery :

Conclusion:

1. LiMn2O4, LiN iMnCoO2, LiN iCoAlO2, LiF eP O4, and Li4T i5O12 batteries have been successfully installed in electric vehicles with specific
features.
2. The LiMn2O4 battery has a low resistance due to its spinel construction, and the LiMn2O4 battery can provide excellent
high current performance in the application. It is very popular from the market because of its very low cost. The disadvantages are poor performance at high
temperatures and limited cycleability.
3. The LiN iMnCoO2 battery provides satisfactory overall performance, especially for high specific energies. With various derivatives of LiN
iMnCoO2, this type of lithium-ion battery can accommodate a variety of applications. Due to its extremely high specific energy and moderate
life, LiNiCoAlO2 is suitable for electric vehicles. High cost and low level of security are negative.

4. The main advantages of LiF eP O4 battery are long life and low cost. Working at high temperatures of
has good thermal stability, but at low temperatures the capacity is significantly reduced. Low specific energy and increased self-discharge are the main drawbacks of the
.
5 The Li4T i5O12 battery has the highest thermal stability, cycle life, and safety performance of any of these five lithium-ion batteries. The
high current lithium plating does not support Li4Ti 5O12 batteries for fast charging. However, the main drawbacks are low specific energy and very high cost.