Week 1 Understanding Different Battery Chemistry

Q NO 1.

Ans

• Li-ion Batteries

  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. Similar to the lead- and nickel-based architecture, lithium-ion uses a cathode (positive electrode), an anode (negative electrode) and electrolyte as conductor. The cathode is a metal oxide and the anode consists of porous carbon. During discharge, the ions flow from the anode to the cathode through the electrolyte and separator; charge reverses the direction and the ions flow from the cathode to the anode. Figure 1 illustrates the process.

Types of Li-ion Cells

• 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).

  Chemical reaction Involved:

  DURING DISCHARGE

  At the anode, lithium is oxidised. Lithium ions are released from the carbon, along with electrons:

  LiC6→xLi++xe−+C6">LiC6→xLi++xe−+C6LiC6→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">Li1−xCoO2+xLi++xe−→LiCoO2Li1−xCoO2+xLi++xe−→LiCoO2

  The overall reaction is:

  C6+LiCoO2⟷LixC6+Li1−xCoO2">C6+LiCoO2⟷LixC6+Li1−xCoO2

• 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 materrial. 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 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 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 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.

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

  Summary Table

  Lithium Cobalt Oxide: LiCoO2 cathode (~60% Co), graphite anode Short form: LCO or Li-cobalt. Since 1991
  Voltages	3.60V nominal; typical operating range 3.0–4.2V/cell
  Specific energy (capacity)	150–200Wh/kg. Specialty 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 depth of discharge, load, temperature
  Thermal runaway	150°C (302°F). Full charge promotes thermal runaway
  Applications	Mobile phones, tablets, laptops, cameras
  Comments 2019 update:	Very high specific energy, limited specific power. Cobalt is expensive. Serves as Energy Cell. Market share has stabilized. Early version; no longer relevant.

  Lithium Manganese Oxide: LiMn2O4 cathode. graphite anode Short form: LMO or Li-manganese (spinel structure) Since 1996
  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 depth of discharge, temperature)
  Thermal runaway	250°C (482°F) typical. High charge promotes thermal runaway
  Applications	Power tools, medical devices, electric powertrains
  Comments 2019 update:	High power but less capacity; safer than Li-cobalt; commonly mixed with NMC to improve performance. Less relevant now; limited growth potential.

  Summary Table

  Lithium Nickel Manganese Cobalt Oxide: LiNiMnCoO2. cathode, graphite anode Short form: NMC (NCM, CMN, CNM, MNC, MCN similar with different metal combinations) Since 2008
  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 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 2019 update:	Provides high capacity and high power. Serves as Hybrid Cell. Favorite chemistry for many uses; market share is increasing. Leading system; dominant cathode chemistry.

  Lithium Iron Phosphate: LiFePO4 cathode, graphite anode Short form: LFP or Li-phosphate. LIP is also common. Since 1996
  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 that 2V causes damage)
  Cycle life	2000 and higher (related to 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 2019 update:	Very flat voltage discharge curve but low capacity. One of safest Li-ions. Used for special markets. Elevated self-discharge. Used primarily for energy storage, moderate growth.

  Lithium Nickel Cobalt Aluminum Oxide: LiNiCoAlO2 cathode (~9% Co), graphite anode Short form: NCA or Li-aluminum. Since 1999
  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 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 2019 update:	Shares similarities with Li-cobalt. Serves as Energy Cell. Mainly used by Panasonic and Tesla; growth potential.

  Lithium Titanate: Cathode can be lithium manganese oxide or NMC; Li2TiO3 (titanate) anode Short form: LTO or Li-titanate Commercially available since about 2008.
  Voltages	2.40V nominal; typical operating range 1.8–2.85V/cell
  Specific energy (capacity)	50–80Wh/kg
  Charge (C-rate)	1C typical; 5C maximum, charges to 2.85V
  Discharge (C-rate)	10C possible, 30C 5s pulse; 1.80V cut-off on LCO/LTO
  Cycle life	3,000–7,000
  Thermal runaway	One of safest Li-ion batteries
  Cost	~$1,005 per kWh (Source: RWTH, Aachen)
  Applications	UPS, electric powertrain (Mitsubishi i-MiEV, Honda Fit EV), solar-powered street lighting
  Comments 2019 update:	Long life, fast charge, wide temperature range but low specific energy and expensive. Among safest Li-ion batteries. Ability to ultra-fast charge; high cost limits to special application.

  
  
  
  

  Solid-state Li-ion: High specific energy but poor loading and safety.
  Lithium-sulfur: High specific energy but poor cycle life and poor loading
  Lithium-air: High specific energy but poor loading, needs clean air to breath, and has a short life.

  Figure 15 compares the specific energy of lead-, nickel- and lithium-based systems. While Li-aluminum (NCA) is the clear winner by storing more capacity than other systems, this only applies to specific energy. In terms of specific power and thermal stability, Li-manganese (LMO) and Li-phosphate (LFP) are superior. Li-titanate (LTO) may have low capacity but this chemistry outlives most other batteries in terms of life span and also has the best cold temperature performance. Moving towards the electric powertrain, safety, and cycle life will gain dominance over overcapacity. (LCO stands for Li-cobalt, the original Li-ion.)