Week 1 Understanding Different Battery Chemistry

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

During discharge, the lithium ions are de-intercalated from the anode and travel back through the electrolyte to the cathode. This also releases the electrons that were tying them to the anode, and these flow through an external wire, providing the electric current that we used to do work. It’s the connection of the external wire that enables the reaction to proceed—when the electrons are free to travel, so are the positively charged lithium ions that will balance the movement of their negative charge.

When the cathode becomes full of lithium ions, the reaction stops and the battery is flat. Then we recharge our lithium-ion batteries again, and the external electric charge that we apply pushes the lithium ions back into the anode from the cathode.

From the above figure ,we can see the discharge of the ions while charging &discharging now discuss types of the lithium ion batteries.

Lithium cobalt oxide (Lico2)-LCO:

Its high specific energy makes Li-cobalt the popular choice for mobile phones, laptops and digital cameras. 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 charge. The drawback of Li-cobalt is a relatively short life span, low thermal stability and limited load capabilities (specific power). Figure 1 illustrates the structure

The cathode has a layered structure. During discharge the lithium ions move from the anode to the cathode; on charge the flow is from cathode to anode

Reaction of LITHIUM COBALT OXIDE BATTERIES:

While discharging-----At the anode, lithium is oxidized. Lithium ions are released from the carbon, along with electrons:

LiC6 ==> xLi+ + xe- + C6

At the cathode, lithium-ions are absorbed by the lithium dioxide, and the electrode is reduced as it also receives the electrons from the circuit:

Li1-xCoO2 + xLi+ + xe- ==> LiCoO2

The overall reaction is=== C6 + LiCoO2 <==> LixC6 + Li1-xCoO2

Lithium manganese oxide (LiMn2O4)—LMO:-

Li-ion with manganese spinel was first published in the Materials Research Bulletin in 1983. In 1996, Moli Energy commercialized a Li-ion cell with lithium manganese oxide as cathode material. 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.

Low internal cell resistance enables fast charging and high-current discharging. In an 18650 package, 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). Li-manganese is used for power tools, medical instruments, as well as hybrid and electric vehicles.

The formation of a three-dimensional crystalline framework on the cathode of a Li-manganese battery. This spinel structure, which is usually composed of diamond shapes connected into a lattice, appears after initial formation

Reaction process:

During Discharge

At the anode, lithium is oxidized. Lithium ions are released from the carbon, along with electrons

LiC6 ==> xLi+ + xe- + C6

At the cathode, lithium-ions are absorbed by the lithium dioxide, and the electrode is reduced as it also receives the electrons from the circuit

Li1-xMn2O4 + xLi+ + xe- ==> LiMnO2

The overall reaction is == LiC6 + Mn2O4 <==>C6 + LiMnO2

Lithium Nickel Manganese Cobalt Oxide (Linimnco02) —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 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. 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. Combining the metals enhances each other strengths.

Reaction of the nmo:

At the anode, lithium is oxidised. Lithium ions are released from the carbon, along with electrons

LiC6 ==> xLi+ + xe- + C6

At the cathode, lithium-ions are absorbed by the lithium dioxide, and the electrode is reduced as it also receives the electrons from the circuit Li1-xMO2 + xLi+ + xe- ==> LiMO2

The overall reaction is ===Li1-xMO2 + LiC6 <==> Li1-xMO2 + C

Lithium iron phosphate(lifepo4)—LFP:-

This cell has a high discharge rate and, because phosphate (PO ) can cope with high temperatures, the battery has good thermal stability, improving its safety. This makes it a good choice for things like electric vehicles and power tools, and for storing energy at power stations. It also has a long cycle life, meaning it can be discharged and charged many times. However, it has a lower energy density than a lithium cobalt oxide cell, and a higher self-discharge rate.

A lithium iron phosphate battery cell is similar to the lithium cobalt oxide cell. The anode is still graphite and the electrolyte is also much the same. The difference is that the lithium cobalt dioxide cathode has been replaced with the more stable lithium iron phosphate. In fact, no lithium or iron ions remain in the iron phosphate (FePO4) cathode of a fully charged cell. The lithium ions can intercalate into or out of the cathode material through well-defined tunnels in its structure without significantly altering the iron phosphate framework.

Reaction of the nfp:

during Discharge

At the anode, lithium is oxidised. Lithium ions are released from the carbon, along with electrons

LiC6 ==> xLi+ + xe- + C6

At the cathode, lithium-ions are absorbed by the lithium dioxide, and the electrode is reduced as it also receives the electrons from the circuit:

LiFe(III)PO4 + xLi+ + xe- ==> LiFe(II)PO4

FePO4 + Li+ + e- ==> LiFePO4

The overall reaction is == LiFePO4 + 6C ==> LiC6 + FePO4

LITHIUM NICKEL COBALT ALUMINUM OXIDE(LINICOALO2)—NCA:-

Lithium nickel cobalt aluminum oxide battery, or NCA, has been around since 1999 for special applications. It shares similarities with NMC by offering high specific energy, reasonably good specific power and a long life span.

During Discharge ,At the anode, lithium is oxidised.Lithium ions are released from the carbon, along with electrons:

LiC6 ==> xLi+ + xe- + C6

At the cathode, lithium-ions are absorbed by the lithium dioxide, and the electrode is reduced as it also receives the electrons from the circuit:

Li1-xMO2 + xLi+ + xe- ==> LiMO2

The overall reaction is ====Li1-xMO2 + LiC6 <==> Li1-xMO2 + C6

LITHIUM TITANATE (LI2TIO3)—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. Li-titanate has a nominal cell voltage of 2.40V, can be fast charged and delivers a high discharge current of 10C, or 10 times the rated capacity. The cycle count is said to be higher than that of a regular Li-ion. Li-titanate is safe, has excellent low temperature discharge characteristics and obtains a capacity of 80 percent at –30°C (–22°F).

LTO (commonly Li4Ti5O12) 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.

Reaction:

During Discharge

At the anode, lithium is oxidised. Lithium ions are released from the carbon, along with electrons

Li4Ti5O12 ==> Ti5O12 + 4Li+ + 4e-

At the cathode, lithium-ions are absorbed by the lithium dioxide, and the electrode is reduced as it also receives the electrons from the circuit

4Mn2O4 + 4Li+ + 4e- ==> 4LiMn2O4

The overall reaction is ===Li4Ti5O12 + 4Mn2O4 <==> 4LiMn2O4 + Ti5O12

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

li-ion types	LCO	LMO	NMC	LFP	NCA	LTO
Chemical name	Lico02	Limn2o4	Linimnco02	Lifepo4	Linicoalo2	Li2tio3
Full form	Lithium cobalt oxide	Lithium manganese oxide	Lithium nickel manganese cobalt oxide	Lithium iron phosphate oxide	Lithium nickel cobalt aluminum oxide	Lithium titanate
Anode	Graphite	Graphite	Graphite	Graphite	Graphite	Titanate
Cathode	Lico02	Limn204	Linimnco02	Lifepo4	Linicoalo2	Li2tio3 (or) NMC
Anode reaction (discharge)	LiC6 ==> xLi+ + xe- + C6	LiC6 ==> xLi+ + xe- + C6	LiC6 ==> xLi+ + xe- + C6	LiC6 ==> xLi+ + xe- + C6	LiC6 ==> xLi+ + xe- + C6	LiC6 ==> xLi+ + xe- + C6
Cathode reaction (discharge)	Li1-xCoO2 + xLi+ + xe- ==> LiCoO2	Li1-xMn2O4 + xLi+ + xe- ==> LiMnO2	Li1-xMO2 + xLi+ + xe- ==> LiMO2	LiFe(III)PO4 + xLi+ + xe- ==> LiFe(II)PO4 FePO4 + Li+ + e- ==> LiFePO4	Li1-xMO2 + xLi+ + xe- ==> LiMO2	4Mn2O4 + 4Li+ + 4e- ==> 4LiMn2O4
Overall reaction	C6 + LiCoO2 <==> LixC6 + Li1-xCoO2	LiC6 + Mn2O4 <==>C6 + LiMnO2	Li1-xMO2 + LiC6 <==> Li1-xMO2 + C	LiFePO4 + 6C ==> LiC6 + FePO4	Li1-xMO2 + LiC6 <==> Li1-xMO2 + C6	Li4Ti5O12 + 4Mn2O4 <==> 4LiMn2O4 + Ti5O12
Electrolyte	Ethylene carbonate	Lithium halide	Lithium salt	Ethylene carbonate	Ethylene carbonate	Lithium salt
separator	polyolefin	polyolefin	polyolefin	polyolefin	polyolefin	polyolefin
Nominal & operational voltage	3.6V & 3.0-4.2V/CELL	3.7V & 3.0-4.2V/CELL	3.6V,3.7V & 3.0-4.2V/CELL	3.2V,3.3 & 3.0-4.2V/CELL	3.6V & 3.0-4.2V/CELL	2.1V &1.85 -2.85V/CELL
ENERGY CAPACITY	150-200 wh/kg & 240wh/kg	100-150 wh/kg	150-220 wh/kg	90-120wh/kg	200-260wh/kg	50-80 wh/kg
LIFE CYCLE(FORCES)	500-1000	300-700	1000-2000	2000&>	500	3000-7000
Charge (c-rate)	0.7–1C, charges to 4.20V (most cells); 3h charge typical. Charge current above 1C shortens battery life.	0.7–1C, charges to 4.20V, some go to 4.30V; 3h charge typical. Charge current above 1C shortens battery life.	1C typical, charges to 3.65V; 3h charge time typical 0.7C, charges to 4.20V	0.7C, charges to 4.20V	0.7–1C typical, 3C maximum, charges to 4.20V (most cells)	1c typical 5c maximum2.85v
Discharge (c-rate)	1c;2.50v cutoff >1c shortens battery	1c;10c possible with some cells ,2.50 cutoff	1c;2c possible on cells	1c,25c on some cells 40a pulse ;2.50cutoff	1c typical 3v cutoff ;high rate discharge	10c possible 30c 5s pulse;1.80 v cutoff
Applications	Mobile, tablets ,laptops Cameras	Power tools Medical devices Electric powertrains	e-bikes evs industrial	Portable&stationary high load currents	Medical devices,industrail	Ups,powerelectric Solarpower
comments	Very high specific energy cobalt is expenxsive markeyt share has stabilized	High power but less capcity safer than li-ion cobalt	Provides high capacity &high power serve as hybrid cell;market share>	Very flat voltage discharge curve but low capacity ;self discharge	Shares similarty li-cobalt battery	Long life wide temp but specific energy and expensive

1. Lithium Cobalt Oxide (LiCoO2) batteries:

• High energy density
• Low internal resistance
• High specific power
• Limited cycle life (usually around 500 cycles)
• Prone to thermal runaway and safety hazards

2. Lithium Manganese Oxide (LiMn2O4) batteries:

• Safer than LiCoO2 batteries
• Good balance of energy density and power
• Moderate cycle life (usually around 1,000 cycles)
• Lower specific energy than LiCoO2 batteries

3. Lithium Iron Phosphate (LiFePO4) batteries:

• Very safe and stable
• Long cycle life (usually over 2,000 cycles)
• Lower energy density than LiCoO2 batteries
• Lower specific power than LiCoO2 and LiMn2O4 batteries

4. Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2) batteries:

• Good balance of energy density, power, and safety
• Moderate cycle life (usually around 1,000 cycles)
• Higher cost than other Li-ion batteries

5. Lithium Titanate Oxide (Li4Ti5O12) batteries:

• Extremely safe and stable
• Very long cycle life (usually over 10,000 cycles)
• Lower energy density than other Li-ion batteries
• Higher specific power than LiFePO4 batteries

Overall, the choice of Li-ion battery type depends on the specific requirements of the application, such as energy density, power, cycle life, safety, and cost.

The figure shows the improvement in battery