Week 1 Understanding Different Battery Chemistry
Aim - Under stand the different type of Lithium Ion Batteries.
Objective -
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 your detailed explanation on it
2.Compare the differences between each type of Li+ion batteries based on their characteristics
Theory :-
- 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).
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.
2.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.
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.
Figure 2 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.
3. 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. 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. This offers a unique blend that also lowers the raw material cost due to reduced cobalt content. Another successful combination is NCM with 5 parts nickel, 3 parts cobalt and 2 parts manganese (5-3-2). Other combinations using various amounts of cathode materials are possible.
Battery manufacturers move away from cobalt systems toward nickel cathodes because of the high cost of cobalt. Nickel-based systems have higher energy density, lower cost, and longer cycle life than the cobalt-based cells but they have a slightly lower voltage.
New electrolytes and additives enable charging to 4.4V/cell and higher to boost capacity. Figure 3 demonstrates the characteristics of the NMC.
Figure 3: Snapshot of NMC.
NMC has good overall performance and excels on specific energy.
This battery is the preferred candidate for the electric vehicle and has the lowest self-heating rate.
4.Lithium Iron Phosphate(LiFePO4) — LFP
In 1996, the University of Texas (and other contributors) discovered phosphate as 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. (See BU-808: How to Prolong Lithium-based Batteries). 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. Figure 4 summarizes the attributes of Li-phosphate.
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.
Figure 4: Snapshot of a typical Li-phosphate battery.
Li-phosphate has excellent safety and long life span but moderate specific energy and elevated self-discharge.
5.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. Figure 5 summarizes the six key characteristics. NCA is a further development of lithium nickel oxide; adding aluminum gives the chemistry greater stability.
Figure 5: Snapshot of NCA.
High energy and power densities, as well as good life span, make NCA a candidate for EV powertrains. High cost and marginal safety are negatives.
6.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 (–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. Figure 6 illustrates the characteristics of the Li-titanate battery. Typical uses are electric powertrains, UPS and solar-powered street lighting
Figure 6: Snapshot of Li-titanate.
Li-titanate excels in safety, low-temperature performance and life span. Efforts are being made to improve the specific energy and lower cost.
1. 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
| Type of Battery | Chemical Formula | Cathode Material | Chemical Reaction at Cathod during Discharge | Anod Material | Chemical Reaction at anode During Discharge | Over all Reaction |
| Lithium cobalt oxide(LCO) | LibCoO2 | cobalt oxide | Li1−xCoO2+xLi++xe−→LiCoO2 | graphite carbon | LiC6→xLi++xe−+C6 | C6+LiCoO2⟷LixC6+Li1−xCoO2 |
| LITHIUM MANGANESE OXIDE (LMO) | LiMn2O4 | manganese dioxide ( MnO2) | Mno2+Li++e- →LiMno2 | graphite carbon | Li+Li1+e | Li+Mno2 → LiMno2 |
| LITHIUM IRON PHOSPHATE (LFP) | LiFePO4 | lithium iron phosphate | FePO4+Li++e−→LiFePO4 | still graphite | LiC6→Li++e−+C6 | LiFePO4+6C→LiC6+FePO4 |
| Lithium nickel cobalt aluminum oxide(NCA) | LiNiCoAlO2 | Lithium nickel cobalt aluminum oxide | Li++NiCoAlO2+e-→LiNiCoAlO2 | graphite carbon | C6Li →6C+Li++e- | C6+NiCoAlO2⟷LiC6+NiCoAlO2 |
| Lithium Mangnese Cobal Oxide(MNC) | LiNixMnyCozO2 | Lithium Mangnese Oxide |
Li1-xNi0.8Mn0.1Co0.1O2+xLI++xe- →LiNi0.8Mn0.1Co0.1O2 |
graphite carbon | LixC6 →xLi++xe-+C6 | C6+LiNi0.8Mn0.1Co0.1+O2 ⟷ LiC6+Ni0.8Mn0.1Co0.1O2 |
| Lithium Titanium Oxide(LTO) | Li4Ti5O12 | manganese dioxide ( MnO2) | 4Li1-xMn2O4+4Li++4e-→4LiMn2O4 | Titanium Oxide | Li4Ti5O12 →Ti5O12+4Li++4e- | Li4Ti5O12+4Mn2O4 ⟷ 4LiMn2O4+Ti5O12 |
2.Differences between each type of Li+ion batteries based on their characteristics :-
|
Characterstics |
LCO |
LMO |
NCA |
NMC |
LFP |
LTO |
|
Voltages |
3.60V nominal; typical operating range 3.0–4.2V/cell |
3.70V (3.80V) nominal; typical operating range 3.0–4.2V/cell |
3.60V nominal; typical operating range 3.0–4.2V/cell |
3.60V, 3.70V nominal; typical operating range 3.0–4.2V/cell, or higher |
3.20, 3.30V nominal; typical operating range 2.5–3.65V/cell |
2.40V nominal; typical operating range 1.8–2.85V/cell |
|
Specific energy (capacity) |
150–200Wh/kg. Specialty cells provide up to 240Wh/kg. |
100–150Wh/kg |
200-260Wh/kg; 300Wh/kg predictable |
150–220Wh/kg |
90–120Wh/kg |
50–80Wh/kg |
|
Charge (C-rate) |
0.7–1C, charges to 4.20V (most cells); 3h charge typical. Charge current above 1C shortens battery life. |
0.7–1C typical, 3C maximum, charges to 4.20V (most cells) |
0.7C, charges to 4.20V (most cells), 3h charge typical, fast charge possible with some cells |
0.7–1C, charges to 4.20V, some go to 4.30V; 3h charge typical. Charge current above 1C shortens battery life. |
1C typical, charges to 3.65V; 3h charge time typical |
1C typical; 5C maximum, charges to 2.85V |
|
Discharge (C-rate) |
1C; 2.50V cut off. Discharge current above 1C shortens battery life. |
1C; 10C possible with some cells, 30C pulse (5s), 2.50V cut-off |
1C typical; 3.00V cut-off; high discharge rate shortens battery life |
1C; 2C possible on some cells; 2.50V cut-off |
1C, 25C on some cells; 40A pulse (2s); 2.50V cut-off (lower that 2V causes damage) |
10C possible, 30C 5s pulse; 1.80V cut-off on LCO/LTO |
|
Cycle life |
500–1000, related to depth of discharge, load, temperature |
300–700 (related to depth of discharge, temperature) |
500 (related to depth of discharge, temperature) |
1000–2000 (related to depth of discharge, temperature) |
2000 and higher (related to depth of discharge, temperature) |
3,000–7,000 |
|
Thermal runaway |
150°C (302°F). Full charge promotes thermal runaway |
250°C (482°F) typical. High charge promotes thermal runaway |
150°C (302°F) typical, High charge promotes thermal runaway |
210°C (410°F) typical. High charge promotes thermal runaway |
270°C (518°F) Very safe battery even if fully charged |
One of safest Li-ion batteries |
|
Applications |
Mobile phones, tablets, laptops, cameras |
Power tools, medical devices, electric powertrains |
Medical devices, industrial, electric powertrain (Tesla) |
E-bikes, medical devices, EVs, industrial |
Portable and stationary needing high load currents and endurance |
UPS, electric powertrain (Mitsubishi i-MiEV, Honda Fit EV), solar-powered street lighting |
References -
https://en.wikipedia.org/wiki/Lithium_nickel_manganese_cobalt_oxides
https://www.science.org.au/curious/technology-future/lithium-ion-batteries
https://www.neicorporation.com/products/batteries/cathode-anode-powders/lithium-titanate/