Challenge

Week 1 Understanding Different Battery Chemistry

SSiddhesh Parab24 Dec 2021

Aim:- Week 1 :- Understanding Different Battery Chemistry

Objective-

1:- Prepare a table which includes materials & chemical reactions occurring at the anode and cathode of LCO, LMO, NCA, NMC, LFP and LTO type of lithium ion cells.Give your detailed explanation on it.

2:- Compare the differences between each type of Li+ion batteries based on their characteristics.

Solution :-

Prepare a table which includes materials & chemical reactions occurring at the anode and cathode of LCO, LMO, NCA, NMC, LFP and LTO type of lithium ion cells.Give your detailed explanation on it

Introduction to batteries:-

The battery is an energy storage device formed by one or more electrochemical cells that can store and delivered electricity by an internal chemical process, more specifically, redox reactions.
The amount of energy stored and delivered by the cell is determined by the active material mass in the electrodes.
Batteries can be divided into two major groups, primary and secondary.
Primary batteries are non-rechargeable systems, due to non-reversibility of the redox reaction.
Secondary batteries differ from the primary by the ability to reverse the redox reaction and therefore be able to have several discharge/charge cycles. Rechargeable batteries are mostly produced in the discharged state thus an initial charge process is needed prior the use.

Lithium-ion battery Chemistry:-

Lithium ion batteries can be designed for optimal capacity with the drawback of limited loading, slow charging and reduced longiveity. An industrial battery may have a moderate amphere 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 seperator. 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 seperator blocks the flow of electrons inside the battery.
Lithium-ion battery consists of reversible redox reactions that take places on the electrode surface facing the electrolyte.
It is defined that the anode (negative electrode) is where the oxidation happens while in the cathode(positive electrode) the reduction, both during the discharge process.
The commonly active materials used for LIB are graphitised carbon (C) in anodes and lithium cobalt oxide (LiCoO2) in cathodes.

Anode reaction:- Ca + bLi+ + be- ↔ LibCa

Cathode reaction:- LiCoO2 ↔ Li(1 - b)CoO2 + bLi+ + be-

Total reaction: Ca + LiCoO2↔ LibCa + Li(1 - b)CoO2
In a LIB, during the discharge, the Li ions released from the anode, de-intercalate in the case of graphite, are solvated by the electrolyte molecules, and transported to the cathode driven by the difference of potential.
As the name suggests, lithium ions (Li ) are involved in the reactions driving the battery.
Both electrodes in a lithium-ion cell are made of materials which can intercalate or ‘absorb’ lithium ions .
Intercalation is when charged ions of an element can be ‘held’ inside the structure of a host material without significantly disturbing it.
In the case of a lithium-ion battery, the lithium ions are ‘tied’ to an electron within the structure of the anode.
When the battery discharges, the intercalated lithium ions are released from the anode, and then travel through the electrolyte solution to be absorbed (intercalated) in the cathode.
A lithium-ion battery starts its life in a state of full discharge:
All its lithium ions are intercalated within the cathode and its chemistry does not yet have the ability to produce any electricity.
Before you can use the battery, you need to charge it.
As the battery is charged, an oxidation reaction occurs at the cathode, meaning that it loses some negatively charged electrons.
To maintain the charge balance in the cathode, an equal number of some of the positively charged intercalated lithium ions are dissolved into the electrolyte solution.
These travel over to the anode, where they are intercalated within the graphite.
This intercalation reaction also deposits electrons into the graphite anode, to ‘tie’ up the lithium ion.

There are three types of crystal structure for the Lithium-ion battery. Crystal structure of the three lithium-insertion compounds in which the Li⁺ ions are mobile through the 2-D (layered), 3-D (spinel), and 1-D (olivine) frameworks.

Types of Li-ion Cells:-

1. Lithium Cobalt Oxide (LCO) :-

The battery consists of a cobalt oxide cathode and a graphite carbon anode.
The cathode has a layered structure and during discharge, lithium ions move from the anode to the cathode. The flow reverses on a charge. Li-cobalt should not be charged and discharged at a current higher than its C-rating.
This means that a 18650 cell with 2,400mAh can only be charged and discharged at 2,400mA. Forcing a fast charge or applying a load higher than 2,400mA causes overheating and undue stress.
Li-cobalt excels on high specific energy but offers only moderate performance specific power, safety, and life span.
Its high specific energy makes Li-cobalt the popular choice for mobile phones, laptops and digital cameras.

2. Lithium Manganese Oxide (LMO) :-

Li-ion with manganese spinel was first published in the Materials Research Bulletin in 1983. Moli Energy commercialized a Li-ion cell with lithium manganese oxide as cathode material. Li-manganese can be discharged at currents of 20–30A with moderate heat buildup.
It is also possible to apply one-second load pulses of up to 50A. A continuous high load at this current would cause heat buildup and the cell temperature cannot exceed 80°C (176°F).
Although moderate in overall performance, newer designs of Li-manganese offer improvements in specific power, safety, and life span.
The architecture forms a three-dimensional spinel structure that improves ion flow on the electrode, which results in lower internal resistance and improved current handling.
A further advantage of spinel is high thermal stability and enhanced safety, but the cycle and calendar life are limited.

3. Lithium Nickel Manganese Cobalt Oxide (NMC) :-

One of the most successful Li-ion systems is a cathode combination of nickel-manganese-cobalt (NMC). Similar to Li-manganese, these systems can be tailored to serve as Energy cells or power Cells. The secret of NMC lies in combining nickel and manganese.An analogy of this is table salt in which the main ingredients, sodium and chloride, are toxic on their own but mixing them serves as seasoning salt and food preserver.
NMC in a 18650 cell for moderate load condition has a capacity of about 2,800mAh and can deliver 4A to 5A; NMC in the same cell optimized for specific power has a capacity of only about 2,000mAh but delivers a continuous discharge current of 20A.
Nickel is known for its high specific energy but poor stability.Manganese has the benefit of forming a spinel structure to achieve low internal resistance but offers a low specific energy.
A silicon-based anode will go to 4,000mAh and higher but at reduced loading capability and shorter cycle life. Silicon added to graphite has the drawback that the anode grows and shrinks with charge and discharge, making the cell mechanically unstable.
The secret of NMC lies in combining nickel and manganese.NMC has good overall performance and excels on specific energy. This battery is the preferred candidate for the electric vehicle and has the lowest self-heating rate.

4. Lithium Iron Phosphate (LFP) :-

In 1996, the University of Texas (and other contributors) discovered phosphate as cathode material for rechargeable lithium batteries. Li-phosphate offers good electrochemical performance with low resistance.This is made possible with nano-scale phosphate cathode material.
Li-phosphate has a higher self-discharge than other Li-ion batteries, which can cause balancing issues with aging.
Four cells in series produce 12.80V, a similar voltage to six 2V lead-acid cells in series. Vehicles charge lead-acid to 14.40V (2.40V/cell) and maintain a topping charge.
Li-phosphate has excellent safety and long life span but moderate specific energy and elevated self-discharge.
Li-phosphate is more tolerant to full charge conditions and is less stressed than other lithium-ion systems if kept at high voltage for a prolonged time.
Li-phosphate is often used to replace the lead acid starter battery.

5. Lithium Nickel Cobalt Aluminium Oxide (NCA) :-

Lithium nickel cobalt aluminum oxide battery, or NCA, has been around since 1999 for special applications. NCA is a further development of lithium nickel oxide. Adding aluminum gives the chemistry greater stability.
It shares similarities with NMC by offering high specific energy, reasonably good specific power, and a long life span. Less flattering are safety and cost.
High cost and marginal safety are negatives.
High energy and power densities, as well as a good life span, make NCA a candidate for EV powertrains.

6. Lithium Titanate Oxide (LTO) :-

Batteries with lithium titanate anodes have been known since the 1980s.
Li-titanate replaces the graphite in the anode of a typical lithium-ion battery and the material forms into a spinel structure.The cathode can be lithium manganese oxide or NMC.
LTO has advantages over the conventional cobalt-blended Li-ion with graphite anode by attaining zero-strain property, no SEI film formation, and no lithium plating when fast charging and charging at low temperature.
Thermal stability under high temperature is also better than other Li-ion systems; however, the battery is expensive. At only 65Wh/kg, the specific energy is low, rivaling that of NiCd. Li-titanate charges to 2.80V/cell and the end of discharge is 1.80V/cell.
Li-titanate excels in safety, low-temperature performance, and life span. Efforts are being made to improve the specific energy and lower cost.

Chemical Reaction:

The chemical reaction taking place at the Anode and Cathode of all the material is;

1) Lithium Cobalt Oxide (LCO) :-

At Anode :-

`Li_xC_6 rarr xLi^+ + xe^- )+ 6C`

At Cathode :-

`Li_(1-x)CoO_2 + xLi^+ + xe^- ) rarr LiCoO_2`

Overall Reaction :-

`C_6 + LiCoO_2 harr Li_xC_6 + Li_(1-x)CoO_2`

2. Lithium Manganese Oxide (LMO):-

At Anode:-

`Li_xC_6 rarr xLi^+ + xe^- )+ 6C`

At Cathode:-

`Li_(1-x)MnO_2 + xLi^+ + xe^- ) rarr LiMnO_2`

Overall Reaction:-

`C_6 + LiMnO_2 harr Li_xC_6 + Li_(1-x)MnO_2`

3. Lithium Nickel Manganese Cobalt Oxide (NMC):-

At Anode:-

`Li_xC_6 rarr xLi^+ + xe^- )+ 6C`

At Cathode:-

`Li_(1-x)Ni_(1-x-y)Mn_xCo_yO_2 + xLi^+ + xe^- ) rarr LiNiMnCoO_2`

Overall Reaction:-

`Li_xC_6 + Li_(1-x)Ni_(1-x-y)Mn_xCo_yO_2 harr LiNiMnCoO_2 +6C`

4. Lithium Iron Phosphate Oxide (`LiFePo_4`):-

At Anode:-

`Li_xC_6 rarr xLi^+ + xe^- )+ 6C`

At Cathode:-

`LiFe(III)PO_4 +xLi^+ + xe^- )rarr LiFe(II)PO_4`

`FePO_4 + Li^+e^- )rarr LiFePO_4`

Overall Reaction:-

`C_6 + LiFePO_4 harr FePO_4 + LiC_6`

5. Lithium Nickel Cobalt Aluminium Oxide (NCA):-

At Anode:-

`Li_xC_6 rarr xLi^+ + xe^- )+ 6C`

At Cathode:-

`NiCoAlO_2 + xLi^+ + xe^- )rarr NiCoAlO_2`

Overall Reaction:-

`C_6 + NiCoAlO_2 harr Li_xC_6 + Li_(1-x)NiCoAlO_2`

6. Lithium Titanate Oxide (LTO) :-

At Anode:-

`Li_7Ti_5O_12 rarr Li_4Ti_5O_12 +3Li^+ +3e^-`

At Cathode:-

`3MnO_2 + 3Li^+ +3e^- )rarr 3LiMnO_2`

Overall Reaction:-

`Li_7Ti_5O_12 + 3MnO_2 harr Li_4Ti_5O_12 + 3LiMnO_2`

The following table summarizes the property of the above material.

*Type of* *Lithium-ion* *Battery*	Lithium Cobalt Oxide (LCO)	Lithium Manganese Oxide (LMO)	Lithium Nickel Manganese Cobalt Oxide (NMC)	Lithium Iron Phosphate (LFP)	Lithium Nickel Cobalt Aluminium Oxide (NCA)	Lithium Titanate Oxide (LTO)
*Chemical Symbol*	`LiCoO_2`	`LiMn_2O_4`	`LiNiMnCoO_2`	`LiFePO_4`	`LiNiCoAlO_2`	`Li_2TiO_3`
*Structure*
*Structure Type*	Layered	Spinel	Layered	Olivine	Layered	Spinel
Cathode Material	Lithium Cobalt Oxide	Lithium Manganese Oxide	Nickel Manganese Nickel Cobalt Oxide	Lithium Iron Phosphate	Lithium Nickel Cobalt Aluminium Oxide	Lithium Manganese Oxide
Anode Material	Graphite Carbon	Graphite Carbon	Graphite Carbon	Graphite Carbon	Graphite Carbon	Lithium Titanate
Electrolyte (Solute + Solvent)	`LiPF_6` + (EC or DMC or PC or EMC or DEC)	`LiPF_6` + (EC or DMC or PC or EMC or DEC)	`LiPF_6` + (EC or DMC or PC or EMC or DEC)	`LiPF_6` + (EC or DMC or PC or EMC or DEC)	`LiPF_6` + (EC or DMC or PC or EMC or DEC)	`LiPF_6` + (EC or DMC or PC or EMC or DEC)
Separator	Polyethylene	Polyethylene	Polyethylene	Polyethylene	Polyethylene	Polyethylene
*Characteristics*
*Specific Energy*	150–200 Wh/kg	100–150 Wh/kg	150 - 220 Wh/kg	90 - 120 Wh/kg	200 - 260 Wh/kg	50–80 Wh/kg
*Application*	Mobile phone, tablets, laptop, camera.	Power tools, medical devices, electric powertrains.	E-bikes, medical devices, EVs.	Portable and stationary needing high load currents.	Medical devices, industrial, electric powertrain.	UPS, electric powertrain, solar-powered street lighting.

Notations done in the above table are as under;

EC: Ethylene Carbonate

PC: Propylene Carbonate

DMC: Dimethyl Carbonate

EMC: Ethyl Methyl Carbonate

DEC: Diethyl carbonate

`LiPF_6` : Lithium Hexafluorophosphate

Electrolyte:-

The electrolyte is the media that conducts ions between electrodes. It comprises either a salt, an acid, or a base that is dissolved in a solvent. Since lithium reacts violently with water, the electrolyte in a lithium-ion cell is composed of nonaqueous organic solvents plus a lithium salt and acts purely as an ionic conducting medium, not taking part in the chemical reaction.
The most commonly used salt is lithium hexafluorophosphate `LiPF_6`which disassociates in the solvent into `Li^+` and `PF^-6`, but other candidates include `LiBF_4` and `LiClO_4`.
Common solvents include ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC).

2:- Compare the differences between each type of Li+ion batteries based on their characteristics.

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Types of Lithium ion batteries:

There are different types of lithium-ion batteries and the main difference between them lies in their cathode materials.
Different kinds of lithium-ion batteries offer different features, with trade-offs between specific power, specific energy, safety, lifespan, cost, and performance.
The six lithium-ion battery types that we will be comparing are Lithium Cobalt Oxide (LCO), Lithium Manganese Oxide (LMO), Lithium Nickel Manganese Cobalt Oxide(NMC), Lithium Iron Phosphate(LFP), Lithium Nickel Cobalt Aluminium Oxide(NCA), and Lithium Titanate Oxide (LTO).

Before choosing the type of battery there are some important points to be considered which affects the battery performance.

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 disaster.

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.

The following differences between each type of Li+ion batteries based on their characteristics are given below:

Types of Li-ion Batteries	Characteristics	Specific Power	Specific Energy	Safety	Lifespan	Cost	Perfomance	Voltage	Application
Lithium Cobalt Oxide (LCO)		Low	High	Low	Low	Low	Medium	3.60V nominal; typical operating range 3.0-4.2V/cell	Cell Phone, Camera & Laptops
Lithium Manganese Oxide (LMO)		Medium	Medium	Medium	Low	Low	Low	3.70,3.80V nominal; typical operating range 3.0-4.2V/cell	Power tools, Medical, Electric Vehicles.
Lithium Nickel Manganese Cobalt Oxide (NMC)		Medium	High	Medium	Medium	Low	Medium	3.60/3.70V nominal; typical operating range 3.0-4.2V/cell or higher	Power tools, Medical, Electric Vehicles.
Lithium Iron Phosphate (LFP)		High	Low	High	High	Low	Medium	3.20,3.30V nominal; typical operating range 2.5-3.65V/cell	Power tools, Medical, Electric Vehicles.
Lithium Nickel Cobalt Aluminium Oxide (NCA)		Medium	High	Low	Medium	Medium	Medium	3.60V nominal; typical operating range 3-4.2V/cell	Grid storage and Electric vehicles
Lithium Titanate (LTO)		Medium	Low	High	High	High	High	2.40V nominal; typical operating range 1.8-2.85V/cell	Grid storage and Electric vehicles

The table above compares the voltages and typical applications of the six basic lithium battery chemistries. Other characteristics of these batteries include:

Lithium Cobalt Oxide (LCO)– 200Wh/kg, deliver a high power, but with the tradeoff of relatively short lives, low power ratings, and low thermal stability.
Lithium Iron Phosphate (LFP)– 120Wh/kg, have long cycle lives and stability at high operating temperatures.
Lithium Manganese Oxide (LMO)– 140Wh/kg, cathodes are based on manganese-oxide components that are abundant, inexpensive, non-toxic, and provide good thermal stability.
Lithium Nickel Cobalt Aluminium Oxide (NCA)– 250Wh/kg, offers high specific energy and long cycle lives.
Lithium Nickel Manganese Cobalt Oxide (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.
Lithium Titanate (LTO)– 80Wh/kg, lowest specific energy, but can be fast charged, discharged at up to 10-times its rated capacity, and is safe.

Conclusion :-

`LiMn_2O_4, LiNiMnCoO_2,LiNiCoAlO_2,LiFePO_4,Li_4Ti_5O_12` batteries have been adopted in EVs successfully with their specific features.
`LiMn_2O_4` battery has low resistance due to the spinel structure, this allows `LiMn_2O_4` battery to offer an excellent performance at high current rate in applications. The extremely low cost makes it highly favoured by the market. Poor performance at high temperature and limited cyclability are the downsides.
`LiNiMnCoO_2`battery has a satisfactory overall performance especially for the high specific energy. A variety of derivatives of `LiNiMnCoO_2` enable this type lithium-ion battery to face different applications. The extremely high specific energy and moderate life span allows `LiNiCoAlO_2` to be a good candidate for EVs. High cost and low level of safety are the negatives.
The key benefits of `LiFePO_4`battery are the long life span and low cost. It has good thermal stability when it operates at high temperature but the capacity is greatly attenuated at low temperature. Low specific energy and elevated self-discharge are the main disadvantages.
`Li_4Ti_5O_12` battery has the best thermal stability, cyclability and safety performance among these five lithium-ion batteries. No lithium plating at high current rate supports `Li_4Ti_5O_12`battery for fast charging. However, the low specific energy and extremely high cost are the major disadvantages.

References :-

Week 1 Understanding Different Battery Chemistry

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