CHALLENGE 1(UNDERSTANDING DIFFERENT BATTERY CHEMISTRY)

1)Understanding various types of Lithium ion cell compositions:

Before moving into the materials and chemical reations takeplace in Li-ion cells we can see the construction of Li-ion cell/battery.

A Li-ion battery is said to be collection of several Li-ion cells in series and parallel connections.

The battery is made up of an anode(-ve terminal),a cathode(+ve terminal),separator,electrolyte,current collectors. The anode and cathode stores the

Li ions.The electrolyte carries the positively charged Li-ions from anode to cathode through the separators. The movement of lithium ions makes free

electrons in anode which creates the charge at positive current collectors makes them discharging and vise versa during charging.The electrons can move

only through external circuits,they cann't move through the electrolyte and seperators. Electrolyte and seperators only allows the ions transfer from anode to

cathode and vise versa.

While the battery is discharging and providing the electric current,the anode releases lithium ions to the chathode generating flow of electrons from anode to

cathode which means current direction is from cathode to anode.

When plugging in the device,the Li-ions are released by cathode and received by anode.That is the electrons flows into the anode makes current direction

from anode to cathode.

The above charging and discharging operations are held at every cells of the battery combaining the output voltage and current to connected load/charging ports.

Here below shown the various components os Li-ion battery as we seen above,

The composition of Li-ions in anode and cathode structure are shown below,

The charging and discharging of the battery can be seen from below animation.The electron flow from anode to cathode during discharge correcponding to Li-ion

tranfer from anode to cathode. During charging the electrons move from cathode to anode corresponding to Li-ion transfer from cathode to anode.

The Li-ion battery chemical compositions varies according to different materials used in it their cathode and anode parts.

Various chemical compositions used in cathode are,

• LCO-Lithium Cobalt Oxide(LiCoO2)
• LFP-Lithium Iron Phosphate(LiFePO4)
• LMO-Lithium Manganese Oxide(LiMn2O4)
• NMC-Litthium Nickel Manganese Cobalt oxide(LiNiMnCoO2)
• NCA-Lithium Nickel Cobalt Aluminium Oxide(LiNiCoAlO2)
• LTO-Lithium Titanium Oxide(LiTiO3)

The anode materials are usually,

• Graphite.
• Hard carbon.
• Lithium Titanate.
• Tin/cobalt alloy.
• Silicon/carbon.

Chemical reactions takes place in anode and cathode:

In these equations the charging denotes from Right to Left and discharging denotes Left to right.

(1)LCO (Lithium Cobalt oxide):

At anode:

LiC₆ → C₆ + Li⁺ + e^-

At cathode:

CoO₂ + Li⁺ +e^- → LicoO₂

Overall relation:

LicoO₂ + C₆ → LiC₆ +CoO₂

(2)LMO (Lithium Manganese Oxide):

At anode:

LiC₆ → C₆ + Li⁺ + e^-

At cathode:

MnO₂ + Li⁺ + e^- → LiMnO₂

Overall relation:

LiMnO₂ + C₆ → LiC₆ + MnO₂

(3)NCA (Lithium Nickel Cobalt Aluminium Oxide):

At anode:

LiC₆ → C₆ + Li⁺ + e^-

At cathode:

NiCoAlO₂ + Li⁺ + e^- → LiNiCoAlO₂

Overall relation:

C₆Li +NiCoAlO₂ →LiCoAlO₂ +C₆

(4)NMC (Lithium Nickel Manganese Cobalt oxide):

At anode:

LiC₆ → C₆ + Li⁺ + e^-

At cathode:

NiMnCoO₂ + Li⁺ + e^- → LiNiMnCoO₂

Overall relation:

LiC₆ + NiMnCoO₂ → LiNiMnCoO₂ + C₆

(5)LFP(Lithium Iron Phosphte):

At anode:

LiC₆ → C₆ + Li⁺ + e^-

At cathode:

FePo₄ + Li⁺ + e^- → LiFePO₄

Overall relation:

LiC₆ + FePo₄ → LiFePO4 + C₆

(6)LTO(Lithium Titanium Oxide)

At anode:

Li₂TiO₃ → TiO₂ +Li⁺ + e^-

At cathode:

Mn₂O₄ + Li + e^- → LiMn₂O₄

Overall relation:

Li₂TiO₃ + 2 Mn₂O₄ → 2LiMn₂O₄ + TiO₃

Table of contents:

Reaction type	LCO	LMO	NCA	NMC	LFP	LTO
Anode	Graphite	Graphite	Graphite	Graphite	Graphite	Lithium Titnium Oxide
Cathode	Lithium cobalt oxide	Lithium Manganese Oxide	Lithium Nickel Cobalt Oxide	Lithium Nickel Manganese Cobalt Oxide	Lithium Iron Phosphate	Manganese Oxide
Electrolyte	Ethylene Carbonate +Li Salt	Methyle Carbonate +Li Salt	Propylene Carbonate +Li Salt	Methyle Carbonate +Li Salt	Propylene Carbonate +Li Salt	Propylene Carbonate +Li Salt
Seperators	Polyolefin	Polyolefin	Polyolefin	Polyolefin	Polyolefin	Polyolefin
Nominal Voltage	3.6V	3.7V	3.6V	3.6V-3.7 V	3.2V-3.3V	2.4V
Applications	Mobiles,Laptops,Cameras	Power tools,Medical devices,Power trains	Electrical power trains,medical devices,Industries	E-bikes,EV's ,Medical devices,industrial uses.	High load current and endurance needed equipments.	Electric Power trains,UPS, Solar power street lights,lighting in industries,etc

2)Characteristics of types of Li-ion Batteries.

LCO(Lithium Cobalt Oxide):

LCO Li battries are having high specific energy makes more popular for mobile phones,laptops,cameras etc..

The battery consist of Cobalt oxide cathode and carbon anode.The cathode having layered structure and during discharge the lithium ions move from anode to cathode.

The flow get reversed while charging.

The drawback of LCO Li-ion batteries are its low life span,low thermal stability,limited low capability.

This shorter life span is due to the usage of graphite as anode with makes SEI(Solid Electrolyte Interface) thickening on anode and lithium plating whilw fast charging

and charging in low twmperature.

Below shown the hexagonal spider graph that shows the characters of LCO batteries.

Nominal voltage:3.6V

Typical operating range: 3.0 - 4.2 V/cell.

Specific energy(Capacity):150-200Wh/Kg. Its seems to be high from above figure.

Specific Power: It is the ability to provide high current,which is operating in moderate level in these types of baatteries.

Charge (C-rate):0.7C-1C rate charge in 3 hrs(typical case).Charge upto 4.2V.Charge current above 1C shorten battery life.

Discharge(C-rate):1C.Cutoff voltage at 2.5V and Discharge current above 1C shorten battery life.

Cycles life:500-1000 cycles.This related to depth of discharge,load and temperature.

Thermal runaway:Full charge promotes thermal runaway codition and its maximum value is 150 deg C.

Cost: Costwise Cobalt is expensive so these batteries are somewhat coastlier.

It has high specific energy capacity but having less specific power, lesser life span makes them less popular over higher load operations.

(LMO)Lithium Manganese Oxide:

Li-manganese having capacity roughly 1/3 of Li-cobalt.

Low internal cell resistance enables fast charging and high current discharging.Li-Manganese batteries discharge current at rate of 20-30A with

moderate heat buildup.

Most Li-manganese batteries blend with NMC for improved specific energy and prolonged life spans.

The spiral graph for this battery type as shown below,

The specific energy and specific power are more or less equal in nature.

Nominal Voltage:3.7V.

Typical operating range:3.0-4.2V/cell.

Specific energy(Capacity):100-150Wh/Kg.

Charge(C-rate):0.7-1C typical,maximum upto 3C. Charge upto 4.2V (Typical level).

Discharge (C-rate):1C.Cutoff Voltage at 2.5V.Discharge possible upto 10C with some cells.

Cycle life:300-700 times related to depth of discharge and temperature.

Thermal runaway:250 deg C at typical condition.High charge promotes thermal runaway.

Higher power but lesser capacity.These battery types are safer than Li-Cobalt batteries.They are commonly mixed with NMC for better performance.

NMC(Lithium Nickel Manganese Cobalt Oxide):

This combination of batteries are one of the most popular among all other Li-ion battery system.

The cathode combination is 1/3 of nickel,1/3 of Manganese,1/3 of Cobalt also known as 1-1-1.This offers a unique blend that also reduce raw material

cost due to reduced cobalt contant.

Battery manufactures move on to Nickel cathods from Cobalt as high cost of cobalt.Nickel based systen having high energy density,low cost,longer

cycle life than the cobalt based batteries but they have lesser amout of voltage.

New electrolytes are used to boost voltages to 4.4V/cell capacity.The spider graph shows the characteristics,

Nominal Voltage:3.6-3.7 V.

Typical voltage range:3.0 -4.2V/cell and higher too.

Specific energy:150-220Wh/Kg.

Charge(C-rate):0.7-1C.Maximum charge upto 4.2V and also to 4.3V.Charge current above 1C shorten the battery life.

Discharge(C-rate):1C-2C.Cutoff voltage as 2.50V.

Cycle life:1000-2000 times(Related to DOD and temperature).

Thermal runaway:210 deg C.High charge promotes thermal runaway.

Cost: Approx.$420/KWh.

These types of batteries provide high capacity and high power.They erves as hybrid cells.Most of the EV manufactures prefers this

battery chemistry.

LFP(Lithium Iron Phosphate):

Li-Phosphate is more tolerant to full charge conditions and is less stressed than other lithium -ion systems if kept at high voltage for

prolonged period of time.

Li-phosphate having higher self discharging than other lithium batteries ,which can cause balancing issues with ageing.This can be mitigated by

buying high quality cells or using sophisticated control electronics which can make increase in cost of pack.

Li-phosphate will be as a leaad acid batteries replacement with a regular vehicle charging system.Cold temperature also reducing the performance

of Li-ions and this could affect the cranking ability in extreme cases.

Below shows the spider chart of these type,

Nominal Voltage:3.20-3.30V.

Typical operating range:2.5-3.65V/cell.

Specific energy:90-120Wh/Kg.

Charge(C-rate):1C typical.Charge upto 3.65V.Charging duration as 3Hr.

Discharge (C-rate):1C-25C on some cells.Cutoff voltage as 2.50V.Less than 2V causses damage.

Cycle life:2000 and higher (Related to depth of discharge and temperature).

Thermal runaway:270 deg C(Fully safe even at full charge)

Cost:Approx. $580/Kwh.

These types of batteries are very flat voltage discharge curve but lower capacity.One of the safest Li-ions .Used for special markets and elevated self discharge.

NCA(Lithium Nickel Cobalt aluminium oxide):

It shares similarities with NMC by offering high specific energy,resonably good specific power and a long life span.

But in order to safety and cost wise they are less flattering.

The spider chart shows the characteristics of these type of batteries,

Nominal Voltage:3.6V

Typical operating range:3.0-4.2V/cell

Specific energy capacity:200-260Wh/kg.Upto 300Wh/Kg.

Charge(C-rate):0.7C,Charge upto 4.2V(most cells),Charge duration as 3Hr(typical case).Fast charge are possible.

Discharge(C-rate):1C typical,Cutoff voltage to 3.0V.High discharge rate shorten the battery life.

Cycle life:500(Related to DOD and temperature)

Thermal runaway:150 deg C(Typical),High charge promotes thermal runaway.

Cost:Approx.$350/KWh.

These types of batteries also used of EV power trains.Tesla makes use of this battery chemistry.

LTO(Lithium Titanium Oxide):

LTO commonly known as Li4Ti5O12 has advantageous over conventional Cobalt blended lithium ion with graphite anode by attaining zero strain

property.

No SEI formation and no Lithium plating when fast charging and at low temperature.Thermal stability is also better under high temperature rather

than other Li-ion batteries.

The spider chart as shown as below,

Nominal Voltage:2.4V.

Typical operating range:1.8-2.85 V/cell.

Specific energy:50-80Wh/Kg.

Charge(C-rate):1C-5C maximum.Charge upto 2.85V.

Discharge(C-rate):10C. Cutoff voltage as 1.80V on LCO/LTO.

Cycle life:3000-7000 times.

Thermal runaway:One of the safest among all Li-ion batteries.

Cost:Approx.$1,005/KWh.

These typee of batteries are long life,fast charge,high temperature range but they are low specific energy and expensive.

They are one of the safest among all Li-ion batteries.

Thank you.

Submitted by,

Praveen Kumar L V,

Date:9/8/2021.