Week 1 Understanding Different Battery Chemistry

OBJECTIVE:

1. Prepare a table which includes materials & chemical reactions occurring at the anode and cathode of LCO, LMO, NCA, NMC, LFP and LTO types of lithium-ion cells. Give your detailed explanation of it
2. Compare the differences between each type of Li+ion battery based on their characteristics.

Objective-1:

1. Prepare a table which includes materials & chemical reactions occurring at the anode and cathode of LCO, LMO, NCA, NMC, LFP and LTO types of lithium-ion cells. Give your detailed explanation of it.

lithium-ion (Li-ion) batteries, energy storage and release are provided by the movement of lithium ions from the positive to the negative electrode back and forth via the electrolyte. In this technology, the positive electrode acts as the initial lithium source and the negative electrode as the host for lithium. Several chemistries are gathered under the name of Li-ion batteries, as the result of decades of selection and optimization close to perfection of positive and negative active materials. Lithiated metal oxides or phosphates are the most common material used as present positive materials. Graphite, also graphite/silicon or Lithiated titanium oxides are used as negative materials.

With actual materials and cell designs, li-ion technology is expected to reach an energy limit in the next coming years. Nevertheless, very recent discoveries of new families of disruptive active materials should unlock present limits. These innovative compounds can store more lithium in positive and negative electrodes and will allow for the first time to combine energy and power.

Lithium-ion batteries are used in most aspects of our everyday lives. Most devices like smartphones and laptops cannot operate without these batteries. Lithium-ion batteries have also become very important in the field of electromobility as it is now the battery of choice in most electric vehicles. Its high specific energy gives it an advantage over other batteries.

There are different types of lithium-ion batteries and the main difference between them lies in their cathode materials.

Lithium-ion battery Types:

There are six types of lithium-ion batteries. They are

Lithium Cobalt Oxide (LCO)

Lithium Manganese Oxide (LMO)

Lithium Iron Phosphate (LFP)

Lithium Nickel Manganese Cobalt Oxide (NMC)

Lithium Nickel Cobalt Aluminium Oxide (NCA)

Lithium Titanate (LTO)

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)

Lithium Manganese Oxide (LiMn₂O₄) — LMO:

LMO (Lithium magnesium oxide) was invented in the year 1996. Its anode material is LiaC6, the cathode material is LibMn2O4 and the carrier is Li+. It is used in different applications like power tools and electric cars. LMO batteries have the ability to deliver a lot of energy in a short period of time, which makes them extremely useful for use in power tools like drills. In 1996, lithium manganese oxide was first used as a cathode material. A three-dimensional spinel structure was formed by this structure, this improves the flow of ions between the electrodes. The high flow decreases the internal resistance and increases loading capability. LMO batteries are usually used in medical devices and equipment, power tools, electric bikes and more. Because of their thermal resistance and higher safety. LMO batteries can also be used for laptops and electrical cars.

Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO₂) — NMC

One of the most successful li-ion cathode formulas developed to date is obtained by combining nickel, manganese, and cobalt. Lithium-Nickel-Manganese-Cobalt-Oxide (LiNiMnCoO2), abbreviated as NMC, has become the go-to cathode powder to develop batteries for power tools, e-bikes and other electric powertrains. It delivers strong overall performance, excellent specific energy, and the lowest self-heating rate of all mainstream cathode powders, which makes it the preferred option for automotive batteries.

Lithium Iron Phosphate (LiFePO₄) — LFP

In 1996, the University of Texas (and other contributors) discovered phosphate as a 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, the 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 ageing. 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.

Lithium Nickel Cobalt Aluminium Oxide (LiNiCoAlO₂) — NCA

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 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 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 per cent 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 temperatures 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.

The below table includes materials & chemical reactions occurring at the anode and cathode of LCO, LMO, NCA, NMC, LFP and LTO types of lithium-ion cells.

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

There are different types of lithium-ion batteries and the main difference between them lies in their cathode materials. Different kinds of lithium-ion batteries offer different features, with trade-offs between specific power, specific energy, safety, lifespan, cost, and performance.

The six lithium-ion battery types that we will be comparing are Lithium Cobalt Oxide, Lithium Manganese Oxide, Lithium Nickel Manganese Cobalt Oxide, Lithium Iron Phosphate, and Lithium Nickel Cobalt Aluminium Oxide, and Lithium Titanate. Firstly, understanding the key terms below will allow for a simpler and easier comparison.

Specific energy: This defines the battery capacity in weight (Wh/kg). The capacity relates to the runtime. Products requiring long runtimes at moderate load are optimized for high specific energy.

Specific power: It's the ability to deliver a high current and indicates loading capability. Batteries for power tools are made for high specific power and come with reduced specific energy.

Performance: These measures how well the battery works over a wide range of temperatures. Most batteries are sensitive to heat and cold and require climate control. Heat reduces life, and cold lowers performance temporarily.

Lifespan: This reflects cycle life and longevity and is related to factors such as temperature, depth of discharge, and load. Hot climates accelerate capacity loss. Cobalt blended lithium-ion batteries also usually have a graphite anode that limits the cycle life.

Safety: This relates to factors such as the thermal stability of the materials used in the batteries. The materials should have the ability to sustain high temperatures before becoming unstable. Instability can lead to thermal runaway in which flaming gases are vented. Fully charging the battery and keeping it beyond the designated age reduces safety.

Cost: Demand for electric vehicles has generally been lower than anticipated, mainly due to the cost of lithium-ion batteries. Hence cost is a huge factor when selecting the type of lithium-ion battery.

The below table shows the comparison of the Li-ion battery types.