Week 1 Understanding Different Battery Chemistry
Q1. 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.
Ans:
LCO(Lithium Cobalt Oxide):
Cathode: LiCoO2 (~60% Co)
Anode: Graphite
Chemical Reactions:
During Discharge:
At the anode, lithium is oxidized. Lithium ions are released from the carbon, along with electrons:
LiC6 → xLi+ + xe− + C6
At the cathode, lithium-ions are absorbed by the lithium dioxide, and the electrode is reduced as it also receives the electrons from the circuit:
Li1−xCoO2 + xLi+ + xe− → LiCoO2
The overall reaction is:
C6 + LiCoO2 ⟷ LixC
During Charge: The above reaction is reversed.
LMO(Lithium Manganese Oxide):
Cathode: LiMn2O4
Anode: Graphite
During Charging and Discharging, Overall Chemical reaction:
LixMn2O4 + LiyC6 ↔ Li x+ᵟMn2O4 + Liy-ᵟC6
NCA(Lithium Nickel Cobalt Aluminum Oxide):
Cathode: LiNiCoAlO2 cathode (~9% Co)
Anode: Graphite
The most important representatives have the general formula LiNixCoyAlzO2 with x + y + z = 1
A version of the oxides(cathode material) in use with x=0.84, y=0.12,z=0.04 i.e, LiNi0.84Co0.12Al0.04O2
NMC(Lithium Nickel Manganese Cobalt Oxide):
Cathode: LiNiMnCoO2
Anode: Graphite
General formula of Cathode material: LiNixMnyCo1−x−yO2
LFP(Lithium Iron Phosphate):
Cathode: LiFePO4
Anode: Graphite
During Discharge:
At the anode, lithium is oxidized. Lithium ions are released from the carbon, along with electrons:
LiC6 → Li+ + e− + C6
At the cathode, lithium ions are absorbed by the lithium dioxide, and the electrode is reduced as it also receives the electrons from the circuit:
LiFe(III)PO4 + xLi+ + xe− → LiFe(II)PO4
FePO4 + Li+ + e− → LiFePO4
The overall reaction is:
LiFePO4 + 6C → LiC6 + FePO4
During Charge:
The above Chemical reaction is reversed while charging.
LTO(Lithium Titanate):
Cathode: Cathode can be lithium manganese oxide or NMC.
Anode: Li2TiO3 or LTO (commonly Li4Ti5O12)
Chemical Reactions taking place during charging and dis-charging:
C6 + xLi+ + xe- ↔ LixC6
Li4Ti5O12 + 3Li+ + 3e- ↔ Li7Ti5O12
Q2.Compare the differences between each type of Li+ion batteries based on their characteristics.
Ans.
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Different CELL Chemistry & their Characteristics |
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Chemistry |
LCO (Lithium Cobalt Oxide) |
LMO (Lithium Manganese Oxide) |
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|
Electrode |
Cathode |
LiCoO2(~60%Co) |
LiMn2O4 |
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Anode |
Graphite |
Graphite |
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Commercially Available |
since 1991 |
Since 1996 |
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Voltages |
Nominal |
3.60 V |
3.70V (3.80V) |
|
Typical Operating Range |
3.0-4.2 V |
3.0–4.2 V |
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Specific Energy(Capacity) |
150-200 Wh/Kg |
100–150 Wh/kg |
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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) |
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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 |
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Cycle Life |
500–1000, related to depth of discharge, load, temperature |
300–700 (related to depth of discharge, temperature) |
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Thermal Runaway |
150°C (302°F). Full charge promotes thermal runaway |
250°C (482°F) typical. High charge promotes thermal runaway |
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Applications |
Mobile phones, tablets, laptops, cameras |
Power tools, medical devices, electric powertrains |
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Comments |
Very high specific energy, limited specific power. Cobalt is expensive. Serves as Energy Cell. Market share has stabilized. |
High power but less capacity; safer than Li-cobalt; commonly mixed with NMC to improve performance. |
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Different CELL Chemistry & their Characteristics |
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Chemistry |
LFP (Lithium Iron Phosphate) |
NMC (Lithium Nickel Manganese Cobalt Oxide) |
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Electrode |
Cathode |
LiFePO4 |
LiNiMnCoO2 |
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Anode |
Graphite |
Graphite |
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Commercially Available |
Since 1996 |
Since 2008 |
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Voltages |
Nominal |
3.20, 3.30V |
3.60V, 3.70V |
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Typical Operating Range |
2.5–3.65V |
3.0–4.2V or higher |
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Specific Energy(Capacity) |
90–120Wh/kg |
150–220Wh/kg |
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Charge(C-Rate) |
1C typical, charges to 3.65V; 3h charge time typical |
0.7–1C, charges to 4.20V, some go to 4.30V; 3h charge typical. Charge current above 1C shortens battery life. |
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Discharge(C-Rate) |
1C, 25C on some cells; 40A pulse (2s); 2.50V cut-off (lower that 2V causes damage) |
1C; 2C possible on some cells; 2.50V cut-off |
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Cycle Life |
2000 and higher (related to depth of discharge, temperature) |
1000–2000 (related to depth of discharge, temperature) |
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Thermal Runaway |
270°C (518°F) Very safe battery even if fully charged |
210°C (410°F) typical. High charge promotes thermal runaway |
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Applications |
Portable and stationary needing high load currents and endurance |
E-bikes, medical devices, EVs, industrial |
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Comments |
Very flat voltage discharge curve but low capacity. One of safest Li-ions. Used for special markets. Elevated self-discharge. |
Provides high capacity and high power. Serves as Hybrid Cell. Favorite chemistry for many uses; market share is increasing. |
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Different CELL Chemistry & their Characteristics |
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Chemistry |
NCA (Lithium Nickel Cobalt Aluminum Oxide) |
LTO (Lithium Titanate) |
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Electrode |
Cathode |
LiNiCoAlO2 |
LMO or NMC |
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Anode |
Graphite |
Li2TiO3 |
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|
Commercially Available |
Since 1999 |
Since about 2008 |
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Voltages |
Nominal |
3.60V |
2.40V |
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Typical Operating Range |
3.0–4.2V |
1.8–2.85V |
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Specific Energy(Capacity) |
200-260Wh/kg; 300Wh/kg predictable |
50–80Wh/kg |
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Charge(C-Rate) |
0.7C, charges to 4.20V (most cells), 3h charge typical, fast charge possible with some cells |
1C typical; 5C maximum, charges to 2.85V |
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Discharge(C-Rate) |
1C typical; 3.00V cut-off; high discharge rate shortens battery life |
10C possible, 30C 5s pulse; 1.80V cut-off on LCO/LTO |
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Cycle Life |
500 (related to depth of discharge, temperature) |
3,000–7,000 |
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Thermal Runaway |
150°C (302°F) typical, High charge promotes thermal runaway |
One of safest Li-ion batteries |
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Applications |
Medical devices, industrial, electric powertrain (Tesla) |
UPS, electric powertrain (Mitsubishi i-MiEV, Honda Fit EV),solar-powered street lighting |
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Comments |
Shares similarities with Li-cobalt. Serves as Energy Cell. |
Long life, fast charge, wide temperature range but low specific energy and expensive. Among safest Li-ion batteries. |
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