Week 1 Understanding Different Battery Chemistry

Week 1 Understanding Different Battery Chemistry

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

ANS:

A lithium-ion battery or Li-ion battery is a type of rechargeable battery composed of cells in which lithium ions move from the negative electrode through an electrolyte to the positive electrode during discharge and back when charging. Li-ion cells use an intercalated lithium compound as the material at the positive electrode and typically graphite at the negative electrode. Li-ion batteries have a high energy density, no memory effect (other than LFP cells) and low self-discharge. Cells can be manufactured to prioritize either energy or power density. They can however be a safety hazard since they contain flammable electrolytes and if damaged or incorrectly charged can lead to explosions and fires.

What is a lithium-ion battery used for.

Lithium-ion (Li-ion) batteries are used in many products such as electronics, toys, wireless headphones, handheld power tools, small and large appliances, electric vehicles and electrical energy storage systems

Four Components of Li-ion Battery – Cathode, Anode, Electrolyte,
Separator

Lithium ion batteries consist of largely four main components: cathode, anode, electrolyte, and separator.
Every single component of a Li-ion battery is essential as it cannot function when one of the components is missing.

Cathode determines the capacity and voltage of a Li-ion battery

A Lithium-ion battery generates electricity through chemical reactions of lithium.

This is why, of course, lithium is inserted into the battery and that space for lithium is called “cathode”.

However, since lithium is unstable in the element form, the combination of lithium and oxygen, lithium oxide is used for cathode.

The material that intervenes the electrode reaction of the actual battery just like lithium

oxide is called active material.

In other words, in the cathode of a Lithium ion battery, lithium oxide is used as an active material.

If you take a closer look at the cathode, you willl find a thin aluminum foil used to hold

the frame of the cathode coated

with a compound made up of active material, conductive additive and binder.

The active material contains lithium ions, the conductive additive is added to increase conductivity;

and the binder acts as an adhesive which helps the active material and the conductive

additive to settle well on the aluminum substrate.

Cathode plays an important role in determining the characteristics of the battery

as the battery’s capacity and voltage are determined by active material type used for

cathode.

The higher amount of lithium, bigger the capacity; and the bigger potential difference

between cathode and anode, higher the voltage.

The potential difference is small for anode depending on their type but for cathode, the

potential difference is relatively high in general.

As such, the cathode plays a significant role in determining the voltage of the battery.

Anode sends electrons through a wire

Just like the cathode, the anode substrate is also coated with active material.

The anode’s active material performs the role of enabling electric current to flow through the external circuit

while allowing reversible absorption/emission of lithium ions released from the cathode.

When the battery is being charged, lithium ions are stored in the anode and not the cathode.

At this point, when the conducting wire connects the cathode to the anode

(discharge state),

lithium ions naturally flow back to the cathode through the electrolyte,

and the electrons

(e-) separated from lithium ions move along the wire generating electricity.

For anode graphite which has a stable structure is used, and the anode substrate is coated with active material,

conductive additive and a binder.

Thanks to graphite’s optimal qualities such as structural stability, low electrochemical reactivity,

conditions for storing much lithium ions and price, the material is considered suitable to be used for anode.

Electrolyte allows the movement of ions only

When explaining about cathode and anode, it was mentioned that lithium ions move through the electrolyte

and electrons move through the wire.

This is the key in enabling the use of electricity in a battery.

If ions flow through the electrolyte, not only can’t we use electricity but safety will be

jeopardized.

Electrolyte is the component which plays this important role.

It serves as the medium that enables the movement of only lithium ions between the cathode and anode.

For the electrolyte, materials with high ionic conductivity are mainly used so that lithium ions move back and forth easily.

The electrolyte is composed of salts, solvents and additives.

The salts are the passage for lithium ions to move, the solvents are organic liquids used to dissolve the salts,

and the additives are added in small amounts for specific purposes.

Electrolyte created in this way only allows ions to move to the electrodes and doesn’t let electrons to pass.

In addition, the movement speed of lithium ions depends on the electrolyte type.

Thus, only the electrolytes that meet stringent conditions can be used.

Separator the absolute barrier between cathode and anode

While the cathode and anode determine the basic performance of a battery, electrolyte

and separator determine the safety of a battery.

The separator functions as a physical barrier keeping cathode and anode apart.

It prevents the direct flow of electrons and carefully lets only the ions pass through the internal microscopic hole.

Therefore, it must satisfy all the physical and electrochemical conditions.

Commercialized separators we have today are synthetic resin such as polyethylene (PE) and polypropylene (PP).

Chemical Reactions occurring at Anode and Cathode of LCO, LMO, NCA, NMC , LFP & LTO

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

ANS:

Battery Comparison

The battery can be compared on many different parameters such as nominal voltage, the weight of the battery, specific energy, etc. The chart given below compares data of different chemistry of Li-ion cell. For reference, we have also added NiMh, Ni-cd battery in the table below.

Battery Chemistry	Temp min (℃)	Temp max (℃)	Cell Voltage (volts)	Self-discharge (% / month)	Cycles Times (max)	Weight
NiCd	-20	60	1.2	20	800	Heavy
NiMH	-20	70	1.2	30	500	Middle
Low Self Discharge NiMH	-20	70	1.2	1	2000	Middle
Li-ion (LCO)	-40	70	3.6	10	1000	Light
Li-ion (LFP)	-40	80	3.2	5	12000	Light
LiPo (LCO)	-40	80	3.7	10	1000	Lightest
Li-Ti (LTO)	-40	55	2.4	5	20000	Light
LMO	-	85	3.7	-	700	Heavy

Comparison of Different Li-ion Chemistries

The property of Lithium-ion cell depends completely on the cell chemistry. All the chemistries have their own pros and cons which need to be considered while selecting a battery for a specific usage. The table listed below compares different Li-Ion chemistries.

	Lithium Titanite (Li2TiO3) — LTO	Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2) — NMC	Lithium Iron Phosphate (LiFePO4) — LFP	Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2) — NCA	Lithium Cobalt Oxide (LiCoO2) — LCO
Voltages Nominal (Volt)	2.40V	3.70V	3.30V	3.70V	3.70V
Typical operating range (V/cell)	1.8V–2.85V	3.0V–4.2V	2.5V–3.65V	3.0 V–4.2V	3.0 V–4.2V
Specific energy (Wh/kg)	50–80Wh/kg	150–220Wh/kg	90–120Wh/kg	200-260Wh/kg	150–200Wh/kg.
Charge (C-rate)	1C typical; 5C maximum, charges to 2.85V	0.7–1C, charges to 4.20V	1C typical, charges to 3.65V	0.7C, charges to 4.20V, fast charging possible with some cells	0.7–1C, charges to 4.20V
Discharge (C-rate)	10C possible, 30C 5s pulse	1C, 2C possible on some cells	1C, 25C on some cells	1C	1C
Cycle life	3,000–7,000	1000–2000	5000-7000; up to 12000 possible in some cells	500	500–1000
Thermal runaway	200°C +	210°C (410°F)	270°C (518°F)	150°C (302°F)	150°C (302°F)
Cost (per kWh)	~$1,005	~$420 per	~$580	~$350	-
Application	Electric vehicles, UPS, etc	E-bikes, E-Rikshaw, industrial equipment, etc	E-bikes, E-Rikshaw, Battery Energy storage system for discoms, offices and homes	Medical devices, industrial equipment, electric vehicles	Smart watches, mobile phones, tablets, laptops, cameras