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

Introduction to lithium-ion cell and its types:-

Lithium-ion is named for its active materials; the words are either written in full or shortened by their chemical symbols. A series of letters and numbers strung together can be hard to remember and even harder to pronounce, and battery chemistries are also identified in abbreviated letters.

For example, lithium cobalt oxide, one of the most common Li-ions, has the chemical symbols LiCoO₂ and the abbreviation LCO. For reasons of simplicity, the short form Li-cobalt can also be used for this battery. Cobalt is the main active material that gives this battery character. Other Li-ion chemistries are given similar short-form names. This section lists six of the most common Li-ions. All readings are average estimates at time of writing.

Lithium-ion batteries can be designed for optimal capacity with the drawback of limited loading, slow charging and reduced longevity. An industrial battery may have a moderate Ah rating but the focus in on durability. Specific energy only provides part of battery performance.

Lithium Cobalt Oxide(LiCoO₂) — 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).

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.

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.

Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO₂) — 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.

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. Cobalt is expensive and in limited supply. Battery manufacturers are reducing the cobalt content with some compromise in performance. A successful combination is NCM532 with 5 parts nickel, 3 parts cobalt and 2 parts manganese. Other combinations are NMC622 and NMC811. Cobalt stabilizes nickel, a high energy active material.

Lithium Iron Phosphate(LiFePO₄) — 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. There is no tolerance for moisture, lest the battery will only deliver 50 cycles. Figure 9 summarizes the attributes of Li-phosphate.

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.

With four Li-phosphate cells in series, each cell tops at 3.60V, which is the correct full-charge voltage. At this point, the charge should be disconnected but the topping charge continues while driving. Li-phosphate is tolerant to some overcharge; however, keeping the voltage at 14.40V for a prolonged time, as most vehicles do on a long road trip, could stress Li-phosphate. Time will tell how durable Li-Phosphate will be as a lead acid replacement with a regular vehicle charging system. Cold temperature also reduces performance of Li-ion and this could affect the cranking ability in extreme cases.

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. 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.

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. 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.

Battery type	Materials	Chemical reactions
LCO	Cathode: Lithium Cobalt Oxide (LiCoO2) Anode: Graphite Electrolyte : LiPF6	At anode: LiC6 → Li+ + e- + C6 At cathode: CoO2 + Li+ + e- → LiCO2 Complete: LiC6 + CoO2 → C6 + LiCoO2
LMO	Cathode: Lithium Manganese Oxide (LiMn2O4) Anode: Graphite Electrolyte : LiPF6	At anode: LiC6 → Li+ + e- + C6 At cathode: Mn2O4 + Li+ + e- → LiMn2O4 Complete: LiC6 + Mn2O4 → C6 + LiMn2O4
NCA	Cathode: Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2) Anode: Graphite Electrolyte : LiPF6	At anode: LiC6 → Li+ + e- + C6 At cathode: NiCoAlO2 + Li+ + e- → LiNiCoAlO2 Complete: LiC6 + NiCoAlO2 → C6 + LiNiCoAlO2
NMC	Cathode: Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2) Anode: Graphite Electrolyte : LiPF6	At anode: LiC6 → Li+ + e- + C6 At cathode: NiMnCoO2 + Li+ + e- → LiNiMnCoO2 Complete: LiC6 + NiMnCoO2 → C6 + LiNiMnCoO2
LFP	Cathode: Lithium Iron Phosphate(LiFePO4) Anode: Graphite Electrolyte : LiPF6	At anode: LiC6 → Li+ + e- + C6 At cathode: FePO4 + Li+ + e- → LiFePO4 Complete: LiC6 + FePO4 → C6 + LiFePO4
LTO	Cathode: Lithium Manganese oxide (LiMn2O4) Anode: Lithium Titanate (Li2TiO3) Electrolyte : LiPF6	At anode: Li2TiO3 → TiO3 + 2Li+ + 2e- At cathode: Mn2O4 + 2Li+ + 2e- → LiMn2O4 Complete: Li2TiO3 + 2Mn2O4 → 2LiMn2O4 + TiO3

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

The main 6 types of lithium ion batteries are discussed above now we see the difference in there charcteristics which can be found while chossing a battery

• Nominal voltage : It is the system voltage at which the device is mainly designed to operate
• Here the rated voltage is basically higher than the nominal voltage to ensure the safe operation of a device
• Cycle: It took place when charing and discharging for a single time makes a cycle
• If the higher the cycles can take place the higher the cycles can takes place then life sapn is aslo higher
• Thermal run way: It mainly begins when the heat is generated within the vattery excceds the amount of heat which is dissipated to its sourroundings
• The internal battery temperature will continue to rise which casuing a domino effect
• The rise in temperature in a single battery will start to affect other batteries nearby the pattern will continue
• Specific energy: The amount of energy stored per unit mass (wh/kg)
• It is very important deciding factor which dcides how much energy or power from the differnt batteries with the same amount of weight.

Comparison of different Li-ion batteries on the basis of characteristics:

Battery Type	Voltage	Specific energy	C-rate (Charge)	C-rate (disharge)	Cycle	Thermal runway
LCO	3.60V nominal; typical operating range 3.0–4.2V/cell	150–200Wh/kg. Specialty cells provide up to 240Wh/kg.	0.7–1C, charges to 4.20V (most cells); 3h charge typical. Charge current above 1C shortens battery life.	1C; 2.50V cut off. Discharge current above 1C shortens battery life.	500–1000, related to depth of discharge, load, temperature	150°C (302°F). Full charge promotes thermal runaway
LMO	3.70V (3.80V) nominal; typical operating range 3.0–4.2V/cell	100–150Wh/kg	0.7–1C typical, 3C maximum, charges to 4.20V (most cells)	1C; 10C possible with some cells, 30C pulse (5s), 2.50V cut-off	300–700 (related to depth of discharge, temperature)	250°C (482°F) typical. High charge promotes thermal runaway
NCA	3.60V nominal; typical operating range 3.0–4.2V/cell	200-260Wh/kg; 300Wh/kg predictable	0.7C, charges to 4.20V (most cells), 3h charge typical, fast charge possible with some cells	1C typical; 3.00V cut-off; high discharge rate shortens battery life	500 (related to depth of discharge, temperature)	150°C (302°F) typical, High charge promotes thermal runaway
NMC	3.60V, 3.70V nominal; typical operating range 3.0–4.2V/cell, or higher	150–220Wh/kg	0.7–1C, charges to 4.20V, some go to 4.30V; 3h charge typical. Charge current above 1C shortens battery life.	1C; 2C possible on some cells; 2.50V cut-off	1000–2000 (related to depth of discharge, temperature)	210°C (410°F) typical. High charge promotes thermal runaway
LFP	3.20, 3.30V nominal; typical operating range 2.5–3.65V/cell	90–120Wh/kg	1C typical, charges to 3.65V; 3h charge time typical	1C, 25C on some cells; 40A pulse (2s); 2.50V cut-off (lower that 2V causes damage)	2000 and higher (related to depth of discharge, temperature)	270°C (518°F) Very safe battery even if fully charged
LTO	2.40V nominal; typical operating range 1.8–2.85V/cell	50–80Wh/kg	1C typical; 5C maximum, charges to 2.85V	10C possible, 30C 5s pulse; 1.80V cut-off on LCO/LTO	3,000–7,000	One of safest Li-ion batteries