Week 1 Understanding Different Battery Chemistry

Name	Cathode	Anode	Separator	Electrolyte	Anode Reaction	Cathode Reaction
LCO (Cobalt based)	Lithium Cobalt Oxide	Graphite	Polyolefin	Ethylene Carbonate	LiC6 <--> C6 + Li+ + e-	CoO2 + Li+ + e- <--> LiCoO2
NCA (Cobalt Based)	Nickel Cobalt Aluminium	Graphite	Polyolefin	Ethylene Carbonate	LiC6 <--> C6 + Li+ + e-	NiCoAlO2 + Li+ + e- <--> LiNiCoAlO2
NMC (Cobalt Based)	Nickel Manganese Cobalt	Graphite	Polyolefin	Lithium Salt	LiC6 <--> C6 + Li+ + e-	NiMnCoO2 + Li+ + e- <--> LINiMnCoO2
LMO	Lithium Manganese Oxide	Graphite	Polyolefin	Lithium Halide	LiC6 <--> C6 + Li+ + e-	MnO2 + Li+ + e- <--> LiMnO2
LFP	Lithium Iron Phosphate	Graphite	Polyolefin	Ethylene Carbonate	LiC6 <--> C6 + Li+ + e-	FePO4 + Li+ + e- <--> LiFePO4
LTO	Lithium Titanate Oxide	Graphite	Polyolefin	Lithium Salt	Li4Ti5O12 <--> Ti5O12+4Li++4e-	4Mn2O4 + Li+ + e- <--> 4LiMn2O4

LCO, NCA and NMC batteries are Cobalt based cells. Initially, Sony corporation invented LCO Chemistry, but using it in automotive applications was considered to be more risky and less efficient. So, some ingredients like Manganese, Nickel and Aluminium were added to solve its disadvantages and hence we have cell chemisty like NMC which is used in Tesla Electric cars. LTO chemisties are quite expensive and provides good life compared to other chemistries. The future of Electric vehicles will be mostly based on Li- Air Chemistries which further needs to be explored.

Types of Li-ion cell and the differences based on their characteristics

1. 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).

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 11 summarizes the six key characteristics. NCA is a further development of lithium nickel oxide; adding aluminum gives the chemistry greater stability.

3. 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. For example, NMC in an 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. 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.

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.

5. 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. As a trade-off, its lower nominal voltage of 3.2V/cell reduces the specific energy below that of cobalt-blended lithium-ion. With most batteries, cold temperature reduces performance and elevated storage temperature shortens the service life, and Li-phosphate is no exception. Li-phosphate has a higher self-discharge than other Li-ion batteries, which can cause balancing issues with aging. This can be mitigated by buying high quality cells and/or using sophisticated control electronics, both of which increase the cost of the pack. Cleanliness in manufacturing is of importance for longevity.

6. 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.