Week 1 Understanding Different Battery Chemistry

Q.1] Prepare a table that includes materials & chemical reactions occurring at the anode and cathode of LCO, LMO, NCA, NMC, LFP, and LTO-type of lithium-ion cells.

Battery:

* A Battery is a device consisting of one or more electrochemical cells with external connections for powering electrical appliances such as Flashlights, mobile phones, and electric cars.

* When a battery is supplying electric power, its positive terminal is the cathode and its negative terminal is the anode.

* The terminal marked negative is the source of electrons that will flow through an external electric circuit to the positive terminal.

* When a battery is connected to an external electric load, a Redox reaction converts high-energy reactants to lower-energy products. The free energy difference is delivered to the external circuit as electrical energy.

* There are two types of batteries,

1. Primary cell - These batteries are one-time use batteries and they cannot be recharged for further usage.

2. Secondary cell - These batteries can be recharged and can be used multiple times.

Lithium-ion Cell:

* Lithium-ion batteries are the second type of battery that can be recharged for further usage.

* The Lithium-ion cells have four main components in it and they are,

(i) Cathode

(ii) Anode

(iii) Electrolyte

(iv) Separator

(i) Cathode:

* They are the positive electrodes of the cell.

* The cathode electrode is usually made up of,

1. Layered Transition metal oxides - Has high Capacity but high in cost and poor in safety.

2. Spinels - High power Density but poor conductivity and stability.

3. Olivines - Lees capacity but has a long life and are high in safety.

(ii) Anode:

* They are the negative electrodes of the cell.

* The anode electrode is usually made up of,

1. Graphite

2. Hard Carbon, these anodes are less in cost and high in stability and specific capacity.

(iii) Electrolyte:

* An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent.

* The dissolved electrolyte separates into cations and anions, which disperse uniformly through the solvent.

* Generally Lithium-ion cells have electrolytes of Organic solvents such as Ethylene carbonate, dimethyl carbonate, propylene carbonate, and lithium salt as solutes.

(iv) Separator:

* Battery separators provide a barrier between the anode (negative) and the cathode (positive) while enabling the exchange of lithium ions from one side to the other.

* They are materials that conduct ions but do not conduct the electrons through them.

* Li-ion cells use polyolefin as a separator. This material has excellent mechanical properties, good chemical stability, and is low-cost.

• Lithium-ion batteries can be designed for optimal capacity with the drawback of limited loading, slow charging, and reduced longevity. An industrial battery may have a moderate ampere rating but the focus is on durability. Specific energy only provides part of battery performance.
• Before looking into the materials and chemical reactions of different types of lithium-ion batteries. A battery is made up of an anode, cathode, separator, electrolyte, and two current collectors (Positive and negative). The anode and cathode store the lithium.
• The electrolyte carries positively charged lithium ions from the anode to the cathode and vice versa through the separator. The movement of the lithium ions creates free electrons in the anode which creates a charge at the positive current collector. The electrical current then flows from the current collector through a device being powered to the negative current collector. The separator blocks the flow of electrons inside the battery.

PARTS OF LITHIUM-ION BATTERY :

While the battery is discharging and providing an electric current, the anode releases lithium ions to the cathode, generating a flow of electrons from one side to the other. When plugging in the device the opposite will happen the lithium ions are released by the cathode and received by the anode. The charging and discharging processes are shown.

Working of Lithium-ion cell:

* The battery is made up of an anode, cathode, separator, electrolyte, and two current collectors (positive and negative), the anode and cathode store the lithium.

* The electrolyte carries positively charged lithium ions from the anode to the cathode and vice versa through the separator.

* The movement of the lithium ions creates free electrons in the anode which creates a charge at the positive current collector.

* The electrical current then flows from the current collector through a powered device (cell phone, computer, Electric motor, etc.) to the negative current collector. The separator blocks the flow of electrons inside the battery.

While the battery discharges and provides an electric current, the anode releases lithium ions to the cathode, generating a flow of electrons from one side to the other.

* When charging, the opposite happens, where Lithium ions are released by the cathode and received by the anode.

* This is the working principle of a lithium-ion battery.

The 6 commonly used lithium-ion batteries are listed below.

• Lithium cobalt oxide (LiCoO2) - LCO.
• Lithium Manganese Oxide (LiMn2O4) - LMO.
• Lithium Nickel Manganese cobalt oxide (liNiMnCoO2) - NMC.
• Lithium Iron Phosphate (LiFePO4) - LFP.
• Lithium Nickel Cobalt Aluminium Oxide (LiNiCoAlO2) - NCA.
• Lithium Titanate (Li2TiO3) - LTO.

Each Lithium-ion battery provides different characteristics and is used in different applications accordingly.

1. Lithium cobalt oxide - LiCoO2 (LCO)

* Also known as lithium cobaltate or lithium-ion cobalt batteries, lithium cobalt oxide batteries are made from lithium carbonate and cobalt.

* They have a cobalt oxide cathode and use graphite carbon as their anode material; during discharge, lithium ions move from anode to cathode, with the flow reversing when the battery is charging.

This type of battery has some drawbacks, including relatively short battery life and limited specific power. additionally, these batteries are not as safe as other types.

2. Lithium Manganese Oxide - LiMn2O4 (LMO)

* The first commercial lithium-ion cells made with lithium manganese oxide as a cathode material were produced in 1996 by Moli Energy.

* Lithium manganese oxide batteries are notable for their high-temperature stability and are also safer than other lithium-ion battery types.

* For this reason, they are often used in medical equipment and devices, but they may also be used in power tools, electric bikes, and more.

* It is also possible to use lithium manganese oxide batteries to power laptops and electric powertrain cars.

MnO2 + Li + +e--->LiMnO4

3. Lithium Nickel Cobalt Aluminium Oxide - LiNiCoAlO2 (NCA)

* Lithium nickel cobalt aluminum oxide batteries are also called NCA batteries and are becoming increasingly important in electric powertrains and in grid storage.

* NCA batteries are not common in the consumer industry, but are promising for the automotive industry.

* NCA batteries provide a high-energy option with a good lifespan, but they are not as safe as they could be compared to other lithium-ion battery types and are quite costly.

4. Lithium Nickel Manganese Cobalt Oxide - LiNiMnCoO2 (NMC)

* Also known as lithium manganese cobalt oxide or NMC batteries, include a cathode made of a combination of nickel, manganese, and cobalt.

* Like other lithium-ion battery varieties, NMC batteries can have either a high specific energy density or a high specific power. They cannot, however, have both properties.

* This battery type is most common in power tools and in powertrains for vehicles.

* The cathode combination ratio is usually 60 percent nickel, 20 percent manganese, and 20 percent cobalt. This means that the raw material cost is lower than it is for other lithium-ion battery options, as cobalt can be quite expensive.

* These batteries may come down in price further in the future, as some battery makers are planning to switch their battery chemistry to a higher % of Nickel so that they can use less cobalt.

* This battery type is commonly preferred for electric vehicles due to its very low self-heating rate.

5. Lithium Iron Phosphate - LiFePo4 (LFP)

* Lithium iron phosphate batteries, also known as li-phosphate batteries, use phosphate as a cathode. They benefit from low resistance properties, which enhance their safety and thermal stability.

Other benefits include durability and a long lifecycle — fully charged batteries can be stored with little change to the total lifespan of the battery’s charge.

* Li-phosphate batteries are often the most cost-effective option as well when their long battery life is taken into consideration. However, the lower voltage of the li-phosphate battery means that it has less energy than other types of lithium batteries.

* Accordingly, these batteries are often used in electric motorcycles as well as other applications that need a long lifecycle and significant safety.

6. Lithium Titanium Oxide - LiTiO2 (LTO)

* Finally, lithium titanate, also known as li-titanate, is a class of battery that allows for ever-increasing applications. The main advantage of the li-titanate battery is its remarkably fast recharge time.

* Currently, manufacturers of electric vehicles and bikes use li-titanate batteries, and there is potential for this type of battery to be used in electric buses for public transportation.

* However, these batteries have lower inherent voltage, or lower energy density, than other lithium-ion battery varieties, which can present issues with powering vehicles efficiently. Even so, the density of lithium titanate batteries is still higher than other non-lithium-ion batteries, which is a plus.

Q.2) Compare the differences between each type of Li+ion battery based on their characteristics

The Major 6 types of lithium-ion batteries were discussed early, Now the major differences in the characteristics can be found when choosing a battery. The major things that can be differentiated from one another.

• 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 when taking place for a single time make a cycle. The higher the cycles can take place, the higher the cycles can take place then lifespan is higher.
• Thermal runaway: The thermal runway begins when the heat generated within a battery exceeds the amount of heat that is dissipated to its surroundings. Internal battery temperature will continue to rise, causing the battery current to rise to create a domino effect. The rise in temperature in a single battery will begin to affect other batteries nearby and the pattern will continue.
• Specific energy: It is the amount of energy stored per unit mass (Wh/Kg). This is a very important deciding factor that decides how much energy or power from different batteries with the same amount of weight.

Specific energy of different types of lithium-based batteries :

The main differences between lithium-ion batteries can be differentiated by their characteristics.

• Nominal Voltage: Most of the batteries are very close when it comes to characteristics. LMO (3.7) has the highest range and LTO (2.4) has the lowest range in volts.
• Cycle life: They differ by a significant amount from each other. LTO battery has the longest life cycle so they can last a longer period of time and it is exactly the opposite of LMO-type batteries.
• Charge current rate: Higher the charge current, the less time the battery will take to get fully charged. LTO and LTP are the highest NCA that comes close to its contenders.
• Discharge current rate: If we need higher discharge rates and faster charging times we should choose a high-rated battery instead. LTO has a discharge rate 10 times higher than the others and it is one of the safest batteries.
• Thermal runaway: A thermal runaway occurs in situations where an increase in temperature changes the conditions in a way that causes an increase in temperature often leading to a destructive result. LTO has the highest temperature rating in this and NCA and LCP have the lowest.
• Specific energy: The specific energy density can be calculated by integrating from 0 to t_cutoff. We can obtain the specific energy density in Wh Kg^-1. Lithium ions with cobalt cathodes offer the highest energy densities. These types of applications are cell phones, laptops, and digital cameras. Power density indicates how much power a battery can deliver on demand.

For ease of choosing a battery from a layman's perspective, the 6 key features are given a value within the 0-5 range for all of them and are given with the same parameters which are considered in the case of 5 points hexagonal analysis of the batteries. They are

1. Specific energy.
2. Specific power.
3. Safety.
4. Performance.
5. Life span.
6. Cost.

LCO :

Li-cobalt excels on high specific energy but offers only moderate performance-specific power, safety, and life span.

LMO :

Although moderate in overall performance, newer designs of Li-manganese offer improvements in specific power, safety, and life span.

NMC :

NMC has good overall performance and excels in specific energy. This battery is the preferred candidate for the electric vehicle and has the lowest self-heating rate.

LFP :

Li-phosphate has excellent safety and a long life span but moderate specific energy and elevated self-discharge.

NCA :

High energy and power densities as well as a good life span make NCA a candidate for EV powertrains. High cost and marginal safety are negative.

LTO :

Li-titanate excels in safety, low-temperature performance, and life span. Efforts are being made to improve the specific energy and lower the cost.

• These types of lithium-ion batteries are some of the most popular. As technology is continuously seeing more development, new lithium technologies are always being developed and those which exist are being developed.

Comparison Table:

Li-ion cell Type	Cathode	Anode	Electrolyte	Separator	Overall Reaction at Cathode & Anode	Application
LCO	Graphite	Lithium Cobalt Oxide	Ethylene Carbonate + Li salt	Polyolefin	Li1-xCoO2(s) + x Li+ + x e- → LiCoO2(s)	Mobile phones, laptops and digital cameras
LMO	lithium manganese oxide	Graphite carbon	Methyl carbonate + Li salt	Polyolefin	Mn2+ + 2 LiC6 → Mn + 2 Li++ graphite	Power tools, medical devices, electric powertrains
NCA	Comprised Nickel cobalt & Aluminium	Graphite carbon	Propylene carbonate + Li salt	Polyolefin	Li(1−x)NiO2 → (2 − x)Li(1−x)/(2−x)Ni1/(2−x)O + x/2O2	Medical devices, industrial, electric powertrain (Tesla)
NMC	Comprised Nickel cobalt & Manganese	Lithium metal Graphite	Methyl carbonate + Li salt	Polyolefin	Li(x)MO2(s) → Li+(org) + Li(x-1)MO2(s) + e-.	E-bikes, medical devices, EVs, industrial
LFP	Comprised Lithium, Iron & Phosphate	Graphite Carbon	Propylene carbonate + Li salt	Polyolefin		Portable and stationary needing high load currents and endurance
LTO	Comprised Nickel cobalt & Manganese	Lithium–titanium oxide	Propylene carbonate + Li salt	Polyolefin	Li4Ti5O12 + 3Li+ + 3e → 4 Li7Ti5O12	UPS, electric powertrain (Mitsubishi i-MiEV, Honda Fit EV), solar-powered street lighting