Week 1 Understanding Different Battery Chemistry

LITHIUM ION CELLS

Lithium-ion is named for its active materials. The words are either written in full or shortened by their chemical symbols.

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.

DIFFERENT TYPES OF LITHIUM ION CELLS

1.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).

2.Lithium Manganese Oxide (LiMn₂O₄) — LMO

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.

3. Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO₂) — NCA

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.

4.Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO₂) — NMC

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.

5.Lithium Iron Phosphate(LiFePO₄) — LFP

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.

6.Lithium Titanate (Li₂TiO₃) — LTO

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.

Sl.NO	Battery	Full Form	Cathode	Anode	Electrolyte	Reaction at anode	Reaction at cathode	Redox reaction
1	LCO	Lithium Cobalt Oxide	LiCoO2	LiC6	LiPF6	LixC6→xLi++xe-+C6	Li1-xCoO2+xLi++xe-→LiCoO2	C6+LiCoO2↔ LiC6+CoO2
2	LMO	Lithum Manganese Oxide	LiMn2O4	LiC6	LiPF6	LixC6→xLi++xe-+C6	Li1-xMn2O4+xLi++xe-→LiMn2O4	C6+LiMn2O4↔ LiC6+Mn2O4
3	NCA	Lithium Nickel Cobalt Aluminium Oxide	LiNiCoAlO2	LiC6	LiPF6	LixC6→xLi++xe-+C6	Li1-xNiCoAlO2+xLi++xe-→LiNiCoAlO2	C6+LiNiCoAlO2↔ LiC6+NiCoAlO2
4	NMC	Lithium Nickel Manganese Cobalt Oxide	LiNi0.8Mn0.1Co0.1O2	LiC6	LiPF6	LixC6→xLi++xe-+C6	Li1-xNi0.8Mn0.1Co0.1O2+xLi++xe-→LiNi0.8Mn0.1Co0.1O2	C6+ LiNi0.8Mn0.1Co0.1O2↔ LiC6+Ni0.8Mn0.1Co0.1O2
5	LFP	Lithium Iron Phosphate	LiFePO4	LiC6	LiPF6	LixC6→ xLi++xe-+C6	Li1-xFePO4+xLi++xe-→LiFePO4	C6+LiFePO4↔ LiC6+FePO4
6	LTO	Lithium Titanium Oxide	LiMn2O4	Li4Ti5O12	LiPF6	Li4Ti5O12→Ti5O12+4Li++4e-	4Li1-xMn2O4+4Li++4e-→4LiMn2O4	Li4Ti5O12+4Mn2O4↔ 4LiMn2O4+Ti5O12

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

ANSWER:-

The difference between lithium and lithium-ion batteries is that one is not rechargeable (primary cell) and the other can be recharged (secondary cell). In addition to this, Lithium batteries have a shelf life up to four times longer than lithium-ion batteries and are also much cheaper and easier to make.

Conversely, the items we rely on to hold their charge for extended periods of time are best powered using Lithium batteries. Whether it’s a medical pacemaker or safety features like a smoke alarm, Lithium batteries are preferred as they last for so much longer. And, although we’d like to point out that it’s very rare, Lithium-ion batteries have been known to catch fire and explode, a feature we thankfully don’t see from Lithium batteries.

Lithium Cobalt Oxide, LCO

The Lithium Cobalt Oxide, LiCoO2, battery is a type of lithium ion battery that find uses in many consumer items of electronic equipment. It provides a very high level of specific energy density along with a good level of safety.

The battery consists of a cobalt oxide cathode with a layered structure. The anode is graphite (carbon). During the discharge cycle, lithium ions move from the anode to the cathode, and in the reverse direction during charge.

The graphite anode limits the battery life as the solid electrolyte interface changes and also as a result of anode thickening. Newer batteries may incorporate nickel or manganese to improve the lifetime as well as reducing manufacturing costs.

One of the drawbacks of the LCO battery is that its current capability in both charge and discharge is limited. As a guide, it should not be charged or discharged at a greater rate than its capacity, i.e. a 2400mAh battery should not be charged or discharged with a current greater than 2400mA. Often figures of 0.8 of the charge level are recommended.

The LCO battery is now being supplanted in some applications by Lithium Manganese, as well as NMC and NCA types. This is occurring as a result of the improved performance of these other types as development improves the performance and as a result of cost.

Lithium Iron Phosphate Battery, LFP

The Lithium Iron Phosphate, LFP type of lithium ion battery provides a low internal resistance and high current capability.

In order to provide its high of current capability, this type of li-ion battery uses a nano-scale phosphate cathode material.

In terms of performance this type of lithium ion battery provides a slightly lower terminal voltage and it has a slightly higher self-discharge rate than other forms. However against this it provides a high current rating, and good thermal stability combined with a good level of, and good thermal stability.

Lithium Manganese Oxide, LMO

This type of lithium ion battery uses Lithium Manganese Oxide, LiMn2O4 as its cathode material. This type of lithium ion battery is structured to allow high currents to flow and this enables it to provide very high current levels and also to be fast charged as well.

It generally uses a three-dimensional spinel structure, i.e. one in which the crystal structure in the cubic, isometric, system, with the oxide anions arranged in a cubic close-packed lattice. This structure improves the flow of ions on the electrode, thereby increasing he current capability and lowering the internal resistance of the cell. A typical 1500mAh battery may be able to deliver steady currents of up to 20 A, obviously for a relatively short time because of the overall battery capacity.

The structure of this type of lithium ion battery also has the advantage that it improves the thermal stability and improves the safety of the cell.

However the disadvantage of the cell is the limited number of charge discharge / cycles as well as the limited calendar life, i.e. the degradation over time since manufacture.

Lithium Nickel Cobalt Aluminium Oxide, NCA

The Lithium Nickel Cobalt Aluminium Oxide battery, or NCA, is a li-ion battery type that is rarely seen in consumer applications but is being investigated for the automotive industry. Its main advantage is that it has a good life span and high energy and power density figures.

However these features come at a cost and in view of the safety elements, it must be used with care. Further development is also required to bring it to a state where this type of li-ion battery can be more widely used.

Lithium Nickel Manganese Cobalt Oxide, NMC

The lithium nickel manganese cobalt oxide lithium battery type uses a cathode comprising of a combination of nickel, manganese, and cobalt.

The key to this lithium ion battery type is the combination of nickel and manganese. Nickel is known for its high specific energy, but poor stability whereas manganese provides low internal resistance but at the cost of low specific energy. Combining both in a cell in the correct manner is able to provide the required balance of the properties of both metals.

The cathode combination often consists of a combination of nickel, manganese and cobalt in equal proportions in a combination known as 1-1-1. This combination reduces cost by reducing the cobalt content, whilst still retaining some of the key performance parameters.

Another popular combination consists of 5 parts nickel, 3 parts cobalt & 2 parts manganese (5-3-2).

The NMC type of lithium ion battery can be optimised for either to high specific power or high specific energy. With the high cost of cobalt, manufacturers are trying to move away from its use, often increasing the use of nickel, so this is often a major fact in the choice of composition of the battery.

These types of lithium ion battery are some of the more popular ones available. However as the technology is continually seeing more development, new lithium ion technologies are always being developed and those which exist are being developed. This has arisen from the needs of the equipment manufacturers. Battery technology in general is forcing development forwards and significant amounts are being invested. As a result, this is a particularly fast moving area of technology where improvements are always being seen.