Week 1 Understanding Different Battery Chemistry
1. The objective is to Prepare a table that includes materials & chemical reactions occurring at the anode and cathode of LCO, LMO, NCA, NMC, LFP, and LTO type of lithium-ion cells and explain each of them.
A lithium-ion battery or Li-ion battery is a type of rechargeable battery. Lithium-ion batteries are commonly used for portable electronics and electric vehicles and are growing in popularity for military and aerospace applications.
In the batteries, lithium ions move from the negative electrode through an electrolyte to the positive electrode during discharge, and back when charging. Li-ion batteries use an intercalated lithium compound as the material at the positive electrode and typically graphite at the negative electrode. The batteries have a high energy density and a low self-discharge. They can however be a safety hazard since they contain flammable electrolytes, and if damaged or incorrectly charged can lead to explosions and fires.
Chemistry, performance, cost, and safety characteristics vary across types of lithium-ion batteries. Research areas for lithium-ion batteries include extending lifetime, increasing energy density, improving safety, reducing cost, and increasing charging speed, among others.
There are various types of Li-ion Battery namely,
LITHIUM COBALT OXIDE (LiCoO2)
The most common lithium-ion cells have an anode of carbon (C) and a cathode of lithium cobalt oxide (LiCoO2). The cobalt and oxygen bond together to form layers of octahedral cobalt oxide structures, separated by sheets of lithium. This structure must allow the cobalt ions to change their valence states between Co+3 and Co+4 (lose and gain a negatively charged electron) when charging and discharging.
Of all the various lithium-ion batteries, these guys have the greatest energy density, which is why they’re currently the batteries found in our phones, digital cameras, and laptops. Their drawback is their thermal instability. Their anodes can overheat and, at high temperatures, the cobalt oxide cathode can decompose, producing oxygen. If you combine oxygen and heat, you’ve got a pretty good chance of starting a fire and, as the chemicals sometimes used in the electrolyte solution, such as diethyl carbonate, are flammable, there can be some safety issues with this battery.
Lithium-ion batteries have in-built protection to prevent overheating and prevent the complete discharge of the battery, which can also be damaging. Additionally, these protection circuits can sometimes be used to prevent the over-charging of lithium-ion batteries, which can have serious consequences. Lithium-ion batteries come in a wide variety of shapes and sizes, and some contain in-built protection devices, such as venting caps, to improve safety.
LITHIUM IRON PHOSPHATE (LiFePO4)
This cell has a high discharge rate and, because phosphate (PO4) can cope with high temperatures, the battery has good thermal stability, improving its safety. This makes it a good choice for electric vehicles and power tools and storing energy at power stations. It also has a long cycle life, meaning it can be discharged and charged many times. However, it has a lower energy density than a lithium cobalt oxide cell and a higher self-discharge rate.
A lithium iron phosphate battery cell is similar to the lithium cobalt oxide cell. The anode is still graphite and the electrolyte is also much the same. The difference is that the lithium cobalt dioxide cathode has been replaced with the more stable lithium iron phosphate. In fact, no lithium or iron ions remain in the iron phosphate (FePO4) cathode of a fully charged cell. The lithium ions can intercalate into or out of the cathode material through well-defined tunnels in its structure without significantly altering the iron phosphate framework.
The cathode of this type of cell is made of negatively charged phosphate anions, bonded with positively charged iron cations in a structure that is capable of storing lithium ions within the iron phosphate molecules. The bonding arrangement in this structure means that the oxygen atoms are tightly bonded into the structure, which gives the cathode its chemical stability.
LITHIUM MANGANESE OXIDE (LiMn2O4)
This type of lithium battery uses a cathode made from lithium-manganese spinel (Li+Mn3+Mn4+O4). Spinel is a type of mineral with a distinctive AB2O4 structure. The spinel structure has very good thermal stability, improving the battery’s safety. It also promotes ion flow within the electrolyte and lowers the internal resistance that contributes to the loss of a battery’s power over time.
While this type of lithium battery offers high discharge and recharge rates (also due to the spinel structure of the cathode) it has a lower capacity and shorter lifetime.
LITHIUM NICKEL MANGANESE COBALT OXIDE (LiNiMnCoO2 or NMC)
Adding nickel and cobalt back into the mix changes things slightly again. Nickel provides high specific energy and, when added to the stable structure of the manganese spinel, also results in a battery with the benefits of the manganese spinel structure (low internal resistance, high charging rate, good stability, and safety).
These batteries are generally made with a cathode with one-third nickel, one-third manganese, and one-third cobalt, but the ratio can vary according to manufacturers’ secret formulas. These batteries are used in power tools, electric vehicles, and medical devices.
Lithium manganese batteries are often coupled with a lithium nickel manganese cobalt oxide battery, producing a combination that is used in many electric vehicles. High bursts of energy (for rapid acceleration) are provided by the lithium-manganese component, and a long driving range is provided by the lithium nickel manganese cobalt oxide component.
LITHIUM NICKEL COBALT ALUMINIUM ION (LiNiCoAlO2 or NCA)
The lithium nickel cobalt aluminum oxides (NCA) are a group of substances comprising metal oxides. Some of them are important due to their application in lithium-ion batteries. NCAs are used as active material on the positive pole (which is the cathode when the battery is discharged). NCAs are mixed oxides comprising the cations of the chemical elements lithium, nickel, cobalt, and aluminum. The voltage of those batteries is between 3.6 V and 4.0 V.
The disadvantage is that the nickel content increases, the risk of thermal breakdown and premature aging of the battery also increases. When a typical NCA battery is heated to 180 °C, it will thermally run away. If the battery was previously overcharged, thermal runaway can occur even at 65 °C. The aluminum ions in NCA increase stability and safety, but they reduce capacity because they do not participate in oxidation and reduction themselves.
LITHIUM TITANATE OXIDE BATTERY Li2TiO3
A lithium-titanate battery is a modified lithium-ion battery that uses lithium-titanate nanocrystals, instead of carbon, on the surface of its anode. This gives the anode a surface area of about 100 square meters per gram, compared with 3 square meters per gram for carbon, allowing electrons to enter and leave the anode quickly. This makes fast recharging possible and provides high currents when needed. Lithium-titanate cells also last for 3000 to 7000 charge cycles.
A disadvantage of lithium-titanate batteries is that they have a lower inherent voltage (2.4 V), which leads to lower specific energy than conventional lithium-ion battery technologies, which have an inherent voltage of 3.7 V although some lithium-titanate batteries are reported to have an energy density of up to 177 Wh/L. The lithium-titanate-oxide (LTO) battery is a type of rechargeable battery that has the advantage of being faster to charge than other lithium-ion batteries, but the disadvantage of having a much lower energy density.
2. The objective is to compare the differences between each type of Li+ion battery based on their characteristics.
- A Lithium-ion battery is the storehouse of energy. To harness the enormous amount of solar, wind, tidal energy – batteries are the only option available to us.
- Advancement in battery tech has enabled the development of newer methods to store energy. The promise of clean and noiseless energy makes this field our first step into the future.
- Lithium is the lightest material known to us, with a density (0.534 g/cm3), it is almost half as dense as water (1 g/cm3). It belongs to Group 1 (called Alkali) of the periodic table with one free electron in its outer shell which makes them highly reactive.
This metal is abundant in the Earth’s surface and can be mined and hence is cheap, making it an ideal choice for batteries.
There are a few specific chemistries, within the broad Lithium-ion battery category that possess unique advantages that helps battery pack makers select the ideal Lithium-ion battery chemistry for various applications.
Important Parameters which distinguishes each type of Li+ion batteries
- Nominal Voltage: It is the system voltage at which the device is designed to operate. The rated voltage is usually higher than the nominal voltage to ensure the safe operation of the device.
- Cycle: The charge and discharge make a Cycle
- The current rate (C): This is used to determine the fast charging capability of a battery.
- Thermal Runaway: It is a condition where an increase in temperature changes the conditions which increase the temperature further, often leading to disaster.
- Specific Energy: It is the amount of energy stored per unit mass (Wh/Kg).
1. Lithium Cobalt Oxide (LiCoO2) — LCO
It has high specific energy but low specific power which means that charging and discharging with Current Rate (C) above rated values shorten the battery’s life. It has a cobalt Oxide Cathode and Graphite anode. The cathode is layered.
During discharge, the Li-ions move from anode to cathode. The flow reverses during charging. The graphite anode limits its cycle life hence it has a short life span. It has low thermal stability. Its main applications are mobile phones, laptops, cameras, etc.
2. Lithium Manganese Oxide (LiMn2O4) — LMO
The Manganese Oxide forms a 3D-spinel structure that improves the ion flow on the electrode. This results in lower internal resistance, which enables fast charging and high-current discharging. Adding to these, the spinel structure also packs extra thermal stability. Making it safer compared to LCO. The LMO has a lower cycle life.
Most Li-manganese batteries blend with lithium nickel manganese cobalt oxide (NMC) to enhance precise energy and prolong battery life. These three active metals, as well as silicon enhancement, can enhance specific energy (capacity), specific power (load capability), or longevity.
Li-manganese has high power and less capacity. It is used for power tools, medical devices as well as in electric vehicle powertrains.
3. Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2) — NMC
The cathodic combination of Nickel Manganese Cobalt is successful as it can be tailored to be either Energy cells or Power Cells. NMC has a good performance and excels in specific energy. This Lithium-ion battery can deliver a continuous discharge current.
The advantage of Nickel is its high specific energy but it has poor stability. Whereas Manganese achieves low internal resistance by forming a spinal structure. Unlike Nickel, Manganese offers low specific energy.
Their combination enhances each other’s performances. New electrolytes can boost capacity. It has the lowest self-heating rate and improved cycle life. This is a battery of choice for electric powertrains and industrial applications.
4. Lithium Iron Phosphate (LiFePO4) — LFP
In this type, Li- Phosphate is used as the cathode since it has good electrochemical performance with low resistance. This is because of the nano-scale phosphate cathode material.
Various advantages of this Lithium-ion battery chemistry include – long lifecycle, good thermal stability, high current rating, enhanced safety, and tolerance in case of abuse.
Li-Phosphate is often used to replace lead-acid batteries as it has moderate specific energy and has a very low tolerance for moisture, which reduces its cycle life drastically.
Other characteristics include a very flat voltage discharge curve but low capacity. LFP is one of the safest Li-ions in the market.
5. Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2) — NCA
NCA batteries are gaining importance in electric powertrains and grid storage. They are not common in the consumer industry but are promising for the automotive Sector. Tesla, the US-based EV manufacturer researches this technology and uses this Lithium-ion battery chemistry.
NCA has the highest Specific Energy, good Specific Power, and a long life span. High cost and marginal safety are the negatives.
6. Lithium Titanate (Li2TiO3) — LTO
In this technology, 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 can be fast-charged and delivers a high discharge current 10 times the rated capacity. The cycle count is higher than the regular Li-ion batteries.
Li-titanate excels in safety and has excellent low-temperature discharge characteristics and life span. The applications of this lithium-ion battery chemistry power include electric powertrains, UPS, and solar-powered street lighting.