Week 1 Understanding Different Battery Chemistry

Aims:

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 detailed explanation on it.
2. Compare the differences between each type of Li-ion batteries based on their characteristics.

Theory:

Part 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 detailed explanation on it.

Working of an Li-ion Battery:

A battery is made up of an anode, cathode, separator, electrolyte, and two current collectors (positive and negative). The anode and cathode store the lithium. The electrolyte carries positively charged lithium ions from the anode to the cathode and vice versa through the separator. The movement of the lithium ions creates free electrons in the anode which creates a charge at the positive current collector. The electrical current then flows from the current collector through a device being powered (cell phone, computer, etc.) to the negative current collector. The separator blocks the flow of electrons inside the battery.

Charge/Discharge

While the battery is discharging and providing an electric current, the anode releases lithium ions to the cathode, generating a flow of electrons from one side to the other. When plugging in the device, the opposite happens: Lithium ions are released by the cathode and received by the anode.

Energy Density VS. Power Density

The two most common concepts associated with batteries are energy density and power density. Energy density is measured in watt-hours per kilogram (Wh/kg) and is the amount of energy the battery can store with respect to its mass. Power density is measured in watts per kilogram (W/kg) and is the amount of power that can be generated by the battery with respect to its mass. To draw a clearer picture, think of draining a pool. Energy density is similar to the size of the pool, while power density is comparable to draining the pool as quickly as possible [1].

Depending on materials choices, the voltage, energy density, life, and safety of a lithium-ion battery can change dramatically. Current effort has been exploring the use of novel architectures using nanotechnology have been employed to improve performance. Areas on interest include nano-scale electrode materials and alternative electrode structures.

Pure lithium is highly reactive. It reacts vigorously with water to form lithium hydroxide (LiOH) and hydrogen gas. Thus, a non-aqueous electrolyte is typically used, and a sealed container rigidly excludes moisture from the battery pack.

Lithium-ion batteries are more expensive than NiCd batteries but operate over a wider temperature range with higher energy densities. They require a protective circuit to limit the peak voltage.

The battery pack of a laptop computer, for each lithium-ion cell, will contain

• a temperature sensor
• a voltage regulator circuit
• a voltage tap
• a charge-state monitor
• a mains connector

These components will

• monitor the charge-state and current flow
• record the latest, full-charge capacity
• monitor the temperature

Their design will minimize the risk of short circuits [2].

Li-ion cells (as distinct from entire batteries) are available in various shapes, which can generally be divided into four groups:

• Small cylindrical (solid body without terminals, such as those used in older laptop batteries)
• Large cylindrical (solid body with large threaded terminals)
• Flat or pouch (soft, flat body, such as those used in cell phones and newer laptops; these are lithium-ion polymer batteries.[105]
• Rigid plastic case with large threaded terminals (such as electric vehicle traction packs)

Cells with a cylindrical shape are made in a characteristic "swiss roll" manner (known as a "jelly roll" in the US), which means it is a single long 'sandwich' of the positive electrode, separator, negative electrode, and separator rolled into a single spool. The shape of the jelly roll in cylindrical cells can be approximated by an Archimedean spiral. One advantage of cylindrical cells compared to cells with stacked electrodes is the faster production speed. One disadvantage of cylindrical cells can be a large radial temperature gradient inside the cells developing at high discharge currents [2].

Types of Li-ion Batteries:

• LCO – Lithium Cobalt Oxide (LiCoO2)
• LMO – Lithium Manganese Oxide (LiMn2O4)
• NCA – Lithium Nickel Cobalt Aluminium Oxide (LiNiCoAlO2)
• NMC – Lithium Nickel Cobalt Manganese Oxide (LiNiCoMnO2)
• LFP – Lithium Iron Phosphate (LiFePO4/C)
• LTO – Lithium Titanate (Li2TiO3)

Below shown is the table to compare different types of Li-ion batteries:

Sr.No.	Battery Type			Cathode	Anode	Advantages	Drawbacks	Applications	Structure
1	LCO (LiCoO2)			Li Cobalt Oxide	Graphite carbon	High specific energy.	Short life span, low thermal stability and limited load capabilities (specific power), Cobalt is expensive.	Mobile phones, laptops and digital cameras.
2	LMO (LiMn2O4)			Lithium Manganese Oxide	Graphite carbon	Lower internal resistance and improved current handling, high thermal stability and enhanced safety.	Cycle and calendar life are limited.	Electric vehicles such as the Nissan Leaf, Chevy Volt and BMW i3, Power tools, medical devices, electric powertrains.
3	NMC (LiNiMnCoO2)			Lithium Nickel Manganese Cobalt Oxide	Graphite carbon	Good overall performance and excels on specific energy, lowest self-heating rate.	High cost due to cobalt.	E-bikes, medical devices, EVs, industrial uses.
4	LFP (LiFePO4)			Lithium Iron Phosphate	Graphite carbon	High current rating and long cycle life, besides good thermal stability, enhanced safety and tolerance if abused.	Higher self-discharge, less specific energy.	Portable and stationary needing high load currents and endurance.
5	NCA (LiNiCoAlO2)			Lithium Nickel Cobalt Aluminum Oxide	Graphite carbon	High specific energy, reasonably good specific power, long life span.	High cost and marginal safety.	Medical devices, industrial, electric powertrain (Tesla).
6	LTO (Li2TiO3)			Lithium Manganese Oxide	Li2TiO3 (titanate)	Fast charging, safe, high discharge current of 10C.	Low specific energy.	UPS, electric powertrain (Mitsubishi i-MiEV, Honda Fit EV), solar-powered street lighting.

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

Below are the explanations about all Li-ion types of batteries [3].

1) LCO: Lithium Cobalt Oxide (LiCoO2)

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 below 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.

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. Newer systems include nickel, manganese and/or aluminium to improve longevity, loading capabilities and cost.

Lithium Cobalt Oxide: LiCoO2 cathode (~60% Co), graphite anode Short form: LCO or Li-cobalt. Since 1991
Voltages	3.60V nominal; typical operating range 3.0–4.2V/cell
Specific energy (capacity)	150–200Wh/kg. Specialty cells provide up to 240Wh/kg.
Charge (C-rate)	0.7–1C, charges to 4.20V (most cells); 3h charge typical. Charge current above 1C shortens battery life.
Discharge (C-rate)	1C; 2.50V cut off. Discharge current above 1C shortens battery life.
Cycle life	500–1000, related to depth of discharge, load, temperature
Thermal runaway	150°C (302°F). Full charge promotes thermal runaway
Applications	Mobile phones, tablets, laptops, cameras
Comments	Very high specific energy limited specific power. Cobalt is expensive. Serves as Energy Cell. Market share has stabilized.

2) LMO: Lithium Manganese Oxide (LiMn2O4)

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 build-up. It is also possible to apply one-second load pulses of up to 50A. A continuous high load at this current would cause heat build-up 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.

Figure below illustrates 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.

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.

Li-manganese has a capacity that is roughly one-third lower than Li-cobalt. Design flexibility allows engineers to maximize the battery for either optimal longevity (life span), maximum load current (specific power) or high capacity (specific energy). For example, the long-life version in the 18650 cell has a moderate capacity of only 1,100mAh; the high-capacity version is 1,500mAh.

Lithium Manganese Oxide: LiMn2O4 cathode. graphite anode Short form: LMO or Li-manganese (spinel structure) Since 1996
Voltages	3.70V (3.80V) nominal; typical operating range 3.0–4.2V/cell
Specific energy (capacity)	100–150Wh/kg
Charge (C-rate)	0.7–1C typical, 3C maximum, charges to 4.20V (most cells)
Discharge (C-rate)	1C; 10C possible with some cells, 30C pulse (5s), 2.50V cut-off
Cycle life	300–700 (related to depth of discharge, temperature)
Thermal runaway	250°C (482°F) typical. High charge promotes thermal runaway
Applications	Power tools, medical devices, electric powertrains
Comments	High power but less capacity; safer than Li-cobalt; commonly mixed with NMC to improve performance.

3) NCA: Lithium Nickel Cobalt Aluminium Oxide (LiNiCoAlO2)

Lithium nickel cobalt aluminium 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. NCA is a further development of lithium nickel oxide; adding aluminium gives the chemistry greater stability.

Lithium Nickel Cobalt Aluminium Oxide: LiNiCoAlO2 cathode (~9% Co), graphite anode Short form: NCA or Li-aluminium. Since 1999
Voltages	3.60V nominal; typical operating range 3.0–4.2V/cell
Specific energy (capacity)	200-260Wh/kg; 300Wh/kg predictable
Charge (C-rate)	0.7C, charges to 4.20V (most cells), 3h charge typical, fast charge possible with some cells
Discharge (C-rate)	1C typical; 3.00V cut-off; high discharge rate shortens battery life
Cycle life	500 (related to depth of discharge, temperature)
Thermal runaway	150°C (302°F) typical, High charge promotes thermal runaway
Applications	Medical devices, industrial, electric powertrain (Tesla)
Comments	Shares similarities with Li-cobalt. Serves as Energy Cell.

4) NMC: Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2)

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 Nickel Manganese Cobalt Oxide: LiNiMnCoO2. cathode, graphite anode. Short form: NMC (NCM, CMN, CNM, MNC, MCN similar with different metal combinations) Since 2008
Voltages	3.60V, 3.70V nominal; typical operating range 3.0–4.2V/cell, or higher
Specific energy (capacity)	150–220 Wh/kg
Charge (C-rate)	0.7–1C, charges to 4.20V, some go to 4.30V; 3h charge typical. Charge current above 1C shortens battery life.
Discharge (C-rate)	1C; 2C possible on some cells; 2.50V cut-off
Cycle life	1000–2000 (related to depth of discharge, temperature)
Thermal runaway	210°C (410°F) typical. High charge promotes thermal runaway
Applications	E-bikes, medical devices, EVs, industrial applications
Comments	Provides high capacity and high power. Serves as Hybrid Cell. Favourite chemistry for many uses; market share is increasing.

5) LFP: Lithium Iron Phosphate (LiFePO4)

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.

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 Iron Phosphate: LiFePO4 cathode, graphite anode. Short form: LFP or Li-phosphate. LIP is also common. Since 1996
Voltages	3.20, 3.30V nominal; typical operating range 2.5–3.65V/cell
Specific energy (capacity)	90–120Wh/kg
Charge (C-rate)	1C typical, charges to 3.65V; 3h charge time typical
Discharge (C-rate)	1C, 25C on some cells; 40A pulse (2s); 2.50V cut-off (lower that 2V causes damage)
Cycle life	2000 and higher (related to depth of discharge, temperature)
Thermal runaway	270°C (518°F) Very safe battery even if fully charged
Applications	Portable and stationary needing high load currents and endurance
Comments	Very flat voltage discharge curve but low capacity. One of safest Li-ions. Used for special markets. Elevated self-discharge.

6) LTO: Lithium Titanate (Li2TiO3)

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. Typical uses are electric powertrains, UPS and solar-powered street lighting.

Lithium Titanate: Cathode can be lithium manganese oxide or NMC; Li2TiO3 (titanate) anode Short form: LTO or Li-titanate. Commercially available since 2008.
Voltages	2.40V nominal; typical operating range 1.8–2.85V/cell
Specific energy (capacity)	50–80Wh/kg
Charge (C-rate)	1C typical; 5C maximum, charges to 2.85V
Discharge (C-rate)	10C possible, 30C 5s pulse; 1.80V cut-off on LCO/LTO
Cycle life	3,000–7,000
Thermal runaway	One of safest Li-ion batteries
Applications	UPS, electric powertrain (Mitsubishi i-MiEV, Honda Fit EV), solar-powered street lighting
Comments	Long life, fast charge, wide temperature range but low specific energy and expensive. Among safest Li-ion batteries.

Conclusion:

• It can be concluded that the study on the materials & chemical reactions occurring at the anode and cathode of LCO, LMO, NCA, NMC, LFP and LTO type of lithium ion cells was done and the table was made describing the batteries and the explanation/comparison was carried out for all different types of Li-ion batteries.

References

[1] https://www.energy.gov/eere/articles/how-does-lithium-ion-battery-work

[2] https://en.wikipedia.org/wiki/Lithium-ion_battery

[3] https://batteryuniversity.com/learn/article/types_of_lithium_ion