Week 1 Understanding Different Battery Chemistry

Q. (a) PREPARE A THABLE WHICH INCLUDES MATERIALS & CHEMICAL REACTIONS OCCURING AT THE ANODE AND CATHODE OF LCO,LMO,NCA,NMC,LFP AND LTO TYPE OF LITHIUM ION CELLS. GIVE YOUR DETAILED EXPLANATION ON IT.

(b) COMPARE THE DIFFERENCES BETWEEN EACH TYPE OF LI-ION BATTERIES BASED ON THERI CHARACTERISTICS.

SOLUTION:-

Battery

A battery is a device that stores chemical energy and converts it to electrical energy.

It consists of one or more electrochemical cells with external connections for powering electrical devices such as flashlights, mobile phones, and electric cars.

The chemical reactions in a battery involve the flow of electrons from one material (electrode) to another, through an external circuit. The flow of electrons provides an electric current that can be used to do work.

Types of Battery

Battery cells are mainly divided into 2 types :

1) Primary cells – Non chargeable cells

2) Secondary cells – chargeable cells –

Primary cells are Non chargeable cells which are used in appliances such as wrist watch, calculator & radio e.g. Dry cell, Li battery

Secondary cells are chargeable cells which can undergo Reversible chemical process i.e., Electrical energy to chemical energy.

E.g. Lead cell, Ni-cd cell, metal air, Ni metal Hydride, Li ion Battery cells

The reason for using Li ion Battery in many application is because of High energy density.

Energy Density:  The energy density is the total amount of energy that can be stored per unit mass or volume. This determines how long your device stays on before it needs a recharge.

 

Fig.1.2.

Battery cells are usually made up of three main components:

1. The Anode (Negative Electrode)
2. The Cathode (Positive Electrode)
3. The electrolytes

During Discharge, The anode is a negative electrode that produces electrons to the external circuit to which the battery is connected. When batteries are connected, an electron build up is initiated at the anode which causes a potential difference between the two electrodes. The electrons naturally then try to redistribute themselves, this is prevented by the electrolyte, so when an electrical circuit is connected, it provides a clear path for the electrons to move from the anode to the cathode thereby powering the circuit to which it is connected.

During charging, the Li ions move back from cathode to Anode as shown in Fig.1.3.

 How does Li-ion Battery work?

 

Fig.1.3.

In a lithium-ion battery, lithium atoms at the anode (-ve) split. This makes electrons and lithium ions (lithium atoms with a positive charge). The lithium ions move within the battery to the cathode (+ve) through an electrolyte. Electrons generally can’t pass through this material. So the electrons take a different path to the cathode through an external circuit. That creates an electric current that can power a device. At the cathode, the electrons meet up with the lithium ions for another chemical reaction.

To charge a battery, this process runs in reverse. The ions and electrons journey back to the anode. In a lithium-ion battery, that anode usually is graphite. The lithium ions tuck between the atom-thin layers of the graphite. The cathode can be one of several lithium-containing materials.

Types of Li-ion Battery

1) Lithium Cobalt Oxide (LiCoO2) — LCO

2) Lithium Manganese Oxide (LiMn2O4) — LMO

3) Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2) - NMC

4) Lithium Iron Phosphate (LiFePO4) — LFP

5) Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2) — NCA

6) Lithium Titanate (Li2TiO3) — LTO

Below is the Table created to compare different Li-ion battery :

Chemical reactions in different Battery :

1) Lithium Cobalt Oxide (LiCoO2) — LCO

2) Lithium Manganese Oxide (LiMn2O4) — LMO

Reaction at anode : Li -> Li+ + e- 

Reaction at cathode : Mno2 + Li+ + e- -> MnOOLi

3) Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2) - NMC

4) Lithium Iron Phosphate (LiFePO4) — LFP

 

5) Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2) — NCA

(b) Comparisons of different types of Li-ion batteries used in EVs from the following perspectives:

1. Specific energy (capacity): This defines the battery capacity in weight (Wh/kg). The capacity relates to the runtime. Products requiring long runtimes at moderate load are optimized for high specific energy.
2. Specific power: It's the ability to deliver high current and indicates loading capability. Batteries for power tools are made for high specific power and come with a reduced specific energy.
3. Safety: This relates to factors such as the thermal stability of the materials used in the batteries. The materials should have the ability to sustain high temperatures before becoming unstable. Instability can lead to thermal runaway in which flaming gases are vented. Fully charging the battery and keeping it beyond the designated age reduces safety.
4. Performance: This measures how well the battery works over a wide range of temperature. Most batteries are sensitive to heat and cold and require climate control. Heat reduces life, and cold lowers the performance temporarily.
5. Life span: This reflects cycle life and longevity and is related to factors such as temperature, depth of discharge and load. Hot climates accelerate capacity loss. Cobalt blended lithium ion also usually have a graphite anode that limits the cycle life.
6. Cost: Demand for electric vehicles has generally been lower than anticipated and this is mainly due to the cost of lithium-ion batteries. Hence cost is a huge factor when selecting the type of lithium-ion battery.

                              

                                                           Fig. Characteristics of different types of Lithium-ion battery

Lithium-ion battery types	Specific Power	Specific Energy	Safety	Lifespan	Cost	Performance
Lithium Cobalt oxide	Low	High	Low	Low	Low	Medium
Lithium Manganese Oxide	Medium	Medium	Medium	Low	Low	Low
Lithium Nickel Manganese Cobalt Oxide	Medium	High	Medium	Medium	Low	Medium
Lithium Iron Phosphate	High	Low	High	High	Low	Medium
Lithium Nickel Cobalt Aluminum Oxide	Medium	High	Low	Medium	Medium	Medium
Lithium Titanate	Medium	Low	High	High	High	High

Lithium Nickel Manganese Cobalt Oxide (NMC), Lithium Iron Phosphate (LiFePO4) and Lithium Manganese Oxide stand out as being superior among these six candidates.