Week 1 Understanding Different Battery Chemistry

Question #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

Solution:

The positive electrodes or cathode in Li-ion batteries are oxides of Li metal and the negative electrodes are commonly carbon/graphite-based. Inside a lithium battery redox (reduction-oxidation) reaction happens at its electrodes. The Li-ions enter the cathode when the battery is discharged and leave when the battery is charging.

The selection of the material of the positive electrode for battery construction is based on factors like specific energy, battery weight, material availability, efficiency, life span, power density, etc.

The cathode materials are broadly classified as:

• Metal Oxides: highest in capacity but cost & safety concerns (NCA, NMC, LCO)
• Spinels: High power density but poor electronic conductivity & structural Stability (LMO, LTO)
• Olivines: Better safety and long life but low capacity & voltage ((LiFePO₄) – LFP).

As mentioned above, Li ions enter and leave the cathode during discharging & charging cycles. The chemical reaction of the cathode can be summarized as [1, 2]:

The anode or negative electrode on the other hand is a graphitic carbon powder where Li-ions leaves and enters during discharging & charging cycle. During charging, the Li-ions leave metal oxide (cathode) and intercalate into the interlayer region of graphite [3]. The chemical reaction can be summarized as [2, 3]:

The overall reaction of the lithium battery can be given as below [1, 3]:

Based on the type of cathode material being used for manufacturing Li-ion batteries, chemical reactions vary. Below is the chemicals reactions happening at the Anode & Cathode of different battery chemistries:

1. Lithium Cobalt Oxide (LCO):

• It’s a Lithium Battery that uses Lithium Cobalt Oxide as the cathode material
  • At the cathode following reaction happens: LiCoO₂ ⇌ CoO₂ + Li⁺ + e^-
  • During charging, Li ions leave the cathode and move to the graphite anode side through the separator.
  • During the discharging cycle, the Li-ion in the anode/graphite side will return to cathode and forms metal oxide again
• Here the Anode is a graphite electrode
  • At the anode: C₆ + Li⁺ + e^- ⇌ LiC₆
  • During the charging cycle, the Li-ions move across the separator via the electrolyte reaches the graphite layer and form LiC
• Combined equation: LiCoO₂ + 6C ⇌ CoO₂ + LiC₆

Note: The explanation for Li-ion movement during the charging & discharging cycle is the same for all the Li-ion battery types. Hence not repeated instead the chemical reactions at the respective electrode are mentioned.

1. Lithium Manganese Oxide (LMO):

A lithium-ion manganese oxide battery (LMO) has Lithium manganese dioxide, LiMnO₂, as the cathode material.

Below reactions are taking place at their electrodes:

• At Cathode: LiMn₂O₄ ⇌ Mn₂O₄ + Li⁺ + e^-
• At Anode: 6C + Li⁺ + e- ⇌ LiC₆
• Combined equation: : LiMn₂O₄ + 6C ⇌ Mn₂O₄ + LiC₆

• NCA – Lithium Nickel Cobalt Aluminium Oxide (LiNiCoAlO₂)
• At Cathode: LiNiCoAlO₂ ⇌ NiCoAlO₂ + Li⁺ + e^-
• At Anode: 6C + Li⁺ + e- ⇌ LiC₆
• Combined equation: : LiNiCoAlO₂ + 6C ⇌ NiCoAlO₂ + LiC₆

1. Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO₂) - NMC

• At Cathode: LiNiMnCoO₂ ⇌ NiMnCoO₂ + Li⁺ + e^-
• At Anode: 6C + Li⁺ + e- ⇌ LiC₆
• Combined equation: : LiNiMnCoO₂ + 6C ⇌ NiMnCoO₂ + LiC₆

1. LFP – Lithium Iron Phosphate (LiFePO₄)

• At Cathode: LiFePO₄ ⇌ FePO₄ + Li⁺ + e^-
• At Anode: 6C + Li⁺ + e- ⇌ LiC₆
• Combined equation: : LiFePO₄ + 6C ⇌ FePO₄ + LiC₆

1. LTO – Lithium Titanate (Li₄Ti₅O₁₂)
   • Replaces the graphite (anode) in the above mentioned Li-ion batteries with Lithium Titanate

Question #2:

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

Solution:

There are different type of Li ion batteries based of the material being used for manufacturing cathode or anode electrode. Below is a table showing a compiled list of various materials that are being used currently:

Cathode (Positive Electrode)	Electrolytes	Anode (Negative Electrode)
§ Lithium Cobalt Oxide (LiCoO2) § Lithium Nickel Oxide (LiNiO2) § Lithium Manganese Oxide (LiMn2O4) - LMO § Lithium Iron Phosphate (LiFePO4) - LFP § Lithium Nickel Manganese Cobalt Oxide (Li(NixMnyCo1-x-y)O2) - NMC § Lithium Nickel Cobalt Aluminum Oxide (Li(NixCoyAl1-x-y)O2) - NCA	§ Aqueous Electrolytes § Organic Liquid Electrolytes § Polymer Electrolytes § Ceramic Electrolytes § Solid Electrolyte Interphase	§ Carbon Based Electrodes § Lithium Titanate (Li4Ti5O12) § Lithium Metal § Alloy Based Electrodes § Silicon Based Electrodes § Conversion Electrodes

Below is a table showing the advantages & disadvantages of each type of Li batteries compared on parameters like: Cost, Life Span, Performance, Safety, Power Density, Energy Density, Specific Power and Specific Energy [2].

Battery type	Advantages	Disadvantages
Lithium Cobalt Oxide (LCO) – LiCoO2	- High in specific energy	- Shorter life span - Limited load capacity - Low on safety
Lithium Manganese Oxide (LMO) - LiMn2O4	- High in specific power - Safety - Higher life span	- Overall performance is moderate
Lithium Iron Phosphate (LFP) - LiFePO4	- Better thermal stability - Higher current rating - Excellent safety - Long life span	- Moderate specific energy - Lower voltage than other Li based batteries - Performances drops with lower temperature
Lithium Nickel Manganese Cobalt Oxide (NMC) – LiNiMnCoO2	- Good overall performance - Excels on specific energy	- High cost
Lithium Nickel Cobalt Aluminium Oxide (NCA) – LiNiCoAlO2	- High power & energy densities - Good life-span	- High cost - marginal safety
Lithium Titanate (LTO) – Li4Ti5O12	- Temperature range of -30 to 55 C - 98% life cycle efficiency - 3000-7000 cycles - High safety and stability - Quick to charge	- Small output cell voltage (2.4V / cell) - Lower energy density - Difficult to manufacture - High cost

References:

[1] Y. Miao, P. Hynan, A. Von Jouanne, and A. Yokochi, "Current li-ion battery technologies in electric vehicles and opportunities for advancements," Energies (Basel), vol. 12, no. 6, p. 1074, 2019, doi: 10.3390/en12061074.

[2] M. A. Hannan, M. M. Hoque, A. Hussain, Y. Yusof, and P. J. Ker, "State-of-the-Art and Energy Management System of Lithium-Ion Batteries in Electric Vehicle Applications: Issues and Recommendations," IEEE Access, vol. 6, pp. 19362-19378, 2018, doi: 10.1109/ACCESS.2018.2817655.

[3] K. Ogura and M. L. Kolhe, "4 - Battery technologies for electric vehicles," in Electric Vehicles: Prospects and Challenges, T. Muneer, M. L. Kolhe, and A. Doyle Eds.: Elsevier, 2017, pp. 139-167.