Week 1 Understanding Different Battery Chemistry

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

Solution:

Lithium Cobalt Oxide(LiCoO 2 ) — 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 drawback of Li-cobalt is a relatively short life span, low thermal stability and limited load capabilities (specific power). Like other cobalt-blended Li-ion, Li-cobalt has a graphite anode that limits the cycle life by a changing solid electrolyte interface (SEI), thickening on the anode and lithium plating while fast charging and charging at low temperature.Li-cobalt should not be charged and discharged at a current higher than its C-rating.

Lithium Manganese Oxide (LiMn 2 O 4 ) — 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 cathode crystalline formation of lithium manganese oxide has a three-dimensional framework
structure that appears after initial formation. Spinel provides low resistance but has a more moderate specific energy than cobalt.

Most Li-manganese batteries blend with lithium nickel manganese cobalt oxide (NMC) to improve the specific energy and prolong the life span. This combination brings out the best in each system, and the LMO (NMC) is chosen for most electric vehicles, such as the Nissan Leaf, Chevy Volt and BMW i3. The LMO part of the battery, which can be about 30 percent, provides high current boost on acceleration; the NMC part gives the long driving range.

Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO 2 ) — 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. 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.

NMC is the battery of choice for power tools, e-bikes and other electric powertrains. The cathode
combination is typically one-third nickel, one-third manganese and one-third cobalt, also known as 1-1-

1. This offers a unique blend that also lowers the raw material cost due to reduced cobalt content.
Another successful combination is NCM with 5 parts nickel, 3 parts cobalt and 2 parts manganese (5-3-

2). Other combinations using various amounts of cathode materials are possible.

Battery manufacturers move away from cobalt systems toward nickel cathodes because of the high cost of cobalt. Nickel-based systems have higher energy density, lower cost, and longer cycle life than the cobalt-based cells but they have a slightly lower voltage.

Lithium Iron Phosphate(LiFePO 4 ) — 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. The key benefits are high current rating and long cycle life, besides good thermal stability, enhanced safety and tolerance if abused.

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. 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. Topping charge is applied to maintain full charge level and prevent sulfation on lead acid batteries.

Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO 2 ) — 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. Less flattering are safety and cost. Figure summarizes the six key characteristics. NCA is a further development of lithium nickel oxide; adding aluminum gives the chemistry greater stability.

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 Li4Ti 5 O 12 ) 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, rivalling that of NiCd. Li-titanate charges to 2.80V/cell, and the end of discharge is 1.80V/cell.

>Chemical reactions:

Type of Lithium Cells	Chemical Name	Material Used at Cathode	Material Used at Anode	Anode	Cathode	Overall Reaction
LCO	Lithium Cobalt Oxide LiCoO2	Lithium cobalt Oxide	Graphite	LiC6 → C6 + Li+ + e-	CoO2 + Li+ + e- → LiCoO2	LiC6 + CoO2 ⇄ C6 + LiCoO2
LMO	Lithium Manganese Oxide LiMn2O4	Lithium Manga nese Oxide	Graphite	LiC6 → C6 + Li+ + e-	MnO2 + Li+ + e- → LiMnO2	LiC6+Mn2O4⇄C6+LiMn2O4
NCA	Lithium Nickel Cobalt Aluminum Oxide LiNiCoAl O2	Nickel Cobalt Alumin um Oxide	Graphite	LiC6 → C6 + Li+ + e-	NiCoAlO2+ Li+ +e- →LiNiCoAl O2	LiC6+NiCoAlO2⇄C6 + LiNiCoAlO2
NCM	Lithium Nickel Manganese Cobalt Oxide LiNiMnC oO2	Nickel Manga nese Cobalt Oxide	Graphite	LiC6 → C6 + Li+ + e-	NiMnCoO2 +Li+ + e- →LiNiMnC oO2	LiC6+NiMnCoO2⇄C6+LiNiMn CoO2
LFP	Lithium Iron Phosphate LiFePO4	nano- scale phosphate	Graphite	LiC6 → C6 + Li+ + e-	FePO4+Li+ + e- → LiFePo4	LiC6+FePO4⇄C6+LiFePo4
LTO	Lithium Titanate Li2TiO3	lithium manga nese oxide	Li4Ti5 O12 (titanate) anode	Li4Ti5O12→Ti5O12 +4li+ + 4e-	4Mn2O4+4 Li+ 4e- → 4LiMn2O4	4Mn2O4+Li4Ti5O12⇄4 LiMn2O4+Ti5O12

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

Solution:

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

Figure compares the specific energy of lead-, nickel- and lithium-based systems. While Li-aluminum (NCA) is the clear winner by storing more capacity than other systems, this only applies to specific energy. In terms of specific power and thermal stability, Li-manganese (LMO) and Li-phosphate (LFP) are uperior. Li-titanate (LTO) may have low capacity but this chemistry outlives most other batteries in terms of life span and also has the best cold temperature performance. Moving towards the electric powertrain, safety and cycle life will gain dominance over capacity. (LCO stands for Li-cobalt, the original Li-ion.)

• SP stands for specific power
• SE stands for specific energy
• SF stands for safety
• LS stands for lifespan
• CS stands for cost
• PF stands for performance
• L stands for low
• M stands for moderate
• H stands for high