Overview of batteries and their chemistry

Aim: Overview of batteries and their chemistry.

Batteries:

Batteries are an electrochemical storage device used to store electrical energy in a chemical form.

Types of Battery cells:

Primary cells - These are single time use cells and cannot be recharged once the cell is brought to its discharge position

Secondary cells - These are rechargeable cells and can be recharged for repeated use. These cells can be used for a limited number of charge cycles as specified by the manufacturer. The number of charge cycles depends on the materials, structure, and usage of the cell.

Types of secondary cells:

Lead-acid [ Pb acid ]

Nickel-Cadmium [ Ni-Cd ]

Lithium-ion [ Li-ion ]

Important parts of Battery:

Anode - Electrode where electrons are generated during discharge.

Cathode - Electrode where electrons are accepted during discharge.

Electrolyte - Prevents direct contact between electrodes and the passing of electrons internally. Only allows ions to pass through it.

Separator - Separates cathode and anode and allows ions to pass through it. Forms a path for the transfer of ions between two electrodes.

Current collectors - They transfer electrons from electrodes to the external circuit/

Working Principle for Li-ion batteries:

[SIP Series]

During charging - `Li^+` ions pass from cathode to anode. During charging state anode accepts electrons.

During discharging - `Li^+` ions pass from anode to cathode. During discharging state anode generates electrons.

Li-ion battery types:

Battery type	ELECTRODE MATERIAL	REACTION
		ANODE	CATHODE
LCO	`LiCoO_2`	`Li_xC harr C + xLi^+ + xe^-`	`Li_((1-x))CoO_2 + xLi^+ +xe^(-) harr LiCoO_2`
LMO	`LiMn_2O_4`	`Li_xC harr C + xLi^+ + xe^-`	`Li_((1-x))Mn_(2)O_4 + xLi^+ + xe^-) harr LiMn_2O_4`
NCA	`LiNiCoAlO_2`	`Li_xC harr C + xLi^+ + xe^-`	`Li_((1-a))Ni_xCo_yAl_zO_2 + aLi^+ + ae^-) harrLiNi_xCo_yAl_zO_2` where, x+y+z = 1
NMC	`LiNiMnCoO_2`	`Li_xC harr C + xLi^+ + xe^-`	`Li_((1-a))Ni_xMn_yC0_zO_2 + aLi^+ + ae^-) harr LiNi_xMn_yC0_zO_2` where, x+y+z = 1
LFP	`LiFePO_4`	`Li_xC harr C + xLi^+ + xe^-`	`Li_((1-a))Fe_xP_yO_4 + aLi^+ + ae^-) harr LiFe_xP_yO_4`
LTO	`Li_2TiO_3`	`Li_4Ti_5O_12 + xLi^+ + xe^-) harr Li_((4+x))Ti_5O_12`	`LiMn_2O_4 harrLi_((1-x))Mn_2O_4 + xLi^+ + xe^-)`

Li-ion battery materials

BATTERY TYPE	ANODE MATERIAL	CATHODE MATERIAL
LCO	Carbon	Lithium Cobalt Oxide
LMO	Carbon	Lithium Manganese Oxide
NCA	Carbon	Lithium Nickel Cobalt Aluminium Oxide
NMC	Carbon	Lithium Nickel Manganese Oxide
LFP	Carbon	Lithium Iron Phosphate
LTO	`Li_4Ti_5O_(12)` (LTO)	`LiMn_2O_4` (LMO)

Electrolyte material for Li-ion batteries:

The electrolyte comprises salt, acid, or base dissolved in a solvent. The most common electrolyte in Li-ion battery is `LiPF_6`

Other electrolyte materials include Diethyl carbonate (DEC), Dimethyl carbonate(DMC), ethyl methyl carbonate (EMC), etc.