Week 1 Understanding Different Battery Chemistry
AIM: 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. Also compare the differences between each type of Li+ion batteries based on their characteristics.
THEORY AND SOLUTION:
A battery is a device consisting of one or more electrochemical cells with external connections for powering electrical devices. When a battery is supplying electric power, its positive terminal is the cathode and its negative terminal is the anode. The terminal marked negative is the source of electrons that will flow through an external electric circuit to the positive terminal. When a battery is connected to an external electric load, a redox reaction converts high-energy reactants to lower-energy products, and the free-energy difference is delivered to the external circuit as electrical energy.
TYPES OF LITHIUM ION BATTERIES:
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:
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.
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.
Lithium Iron Phosphate(LiFePO4) — LFP
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.
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. 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.
The chemical reactions occuring at anode and cathode at each type of battery are shown below:
2) The differences between each type of Li+ion batteries based on their characteristics:
Characteristics of lithium cobalt oxide( LCO)
| Lithium Cobalt Oxide: LiCoO2 cathode (~60% Co), graphite anode Short form: LCO or Li-cobalt. |
|
| Voltages | 3.60V nominal; typical operating range 3.0–4.2V/cell |
| Specific energy (capacity) | 150–200Wh/kg. Speciality 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 the 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. |
Characteristics of Lithium Manganese Oxide( LMO)
| Lithium Manganese Oxide: LiMn2O4 cathode. graphite anode Short form: LMO or Li-manganese (spinel structure) |
|
| 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 the 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. |
Characteristics of Lithium Nickel Cobalt Aluminum Oxide(NCA)
| Lithium Nickel Cobalt Aluminum Oxide: LiNiCoAlO2 cathode (~9% Co), graphite anode Short form: NCA or Li-aluminum. |
|
| 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 the depth of discharge, temperature) |
| Thermal runaway | 150°C (302°F) typical, High charge promotes thermal runaway |
| Cost | ~$350 per kWh (Source: RWTH, Aachen) |
| Applications | Medical devices, industrial, electric powertrain (Tesla) |
| Comments | Shares similarities with Li-cobalt. Serves as Energy Cell. Mainly used by Panasonic and Tesla; growth potential. |
Characteristics of lithium nickel manganese cobalt oxide (NMC)
| Lithium Nickel Manganese Cobalt Oxide: LiNiMnCoO2. cathode, graphite anode Short form: NMC |
|
| Voltages | 3.60V, 3.70V nominal; typical operating range 3.0–4.2V/cell, or higher |
| Specific energy (capacity) | 150–220Wh/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 the depth of discharge, temperature) |
| Thermal runaway | 210°C (410°F) typical. High charge promotes thermal runaway |
| Cost | ~$420 per kWh (Source: RWTH, Aachen) |
| Applications | E-bikes, medical devices, EVs, industrial |
| Comments | Provides high capacity and high power. Serves as Hybrid Cell. Favourite chemistry for many uses; market share is increasing. |
Characteristics of lithium iron phosphate(LFP)
| Lithium Iron Phosphate: LiFePO4 cathode, graphite anode Short form: LFP or Li-phosphate. LIP is also common. |
|
| 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 than 2V causes damage) |
| Cycle life | 2000 and higher (related to the depth of discharge, temperature) |
| Thermal runaway | 270°C (518°F) Very safe battery even if fully charged |
| Cost | ~$580 per kWh (Source: RWTH, Aachen) |
| 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. |