Understanding Lithium-Ion Batteries in the EV Domain - part 2

 

The second part of this three-part blog series on Lithium-ion batteries explains the usage of lithium-ion batteries in electronic gadgets such as laptops and mobile phones. Further, it also substantiates the need for precaution and care while opening a battery package. 

 

Types of Batteries

Broadly speaking, batteries can be categorized into two main types:

 

Primary Cells

• Can be used only once
• Must be discarded after use
• These batteries have a single discharge cycle
• Non-rechargeable battery cells
• Used for low power application gadgets such as torches, calculators, watches, and radio
• The electrochemical reaction occurring within the cell is reversible
• These batteries feature in AA and AAA sizes
• Examples: dry cells and lithium batteries

 

Note that lithium batteries are different from li-ion batteries. Lithium batteries are the coin-type batteries that you might find in clocks and wristwatches and can only be used once. Contrastly, lithium-ion batteries are rechargeable and generally found in phones and laptops.

Primary battery types result in left-over waste from battery manufacturing. Factories recycle the remaining scrap from the primary cells.

 

Secondary Cells

• Can be used multiple times
• Rechargeable battery cells
• Have applications in the automotive industry
• These cells have a low energy density
• These batteries work on the reverse chemical process that is when electrical energy gets converted into chemical energy
• Have a complicated structure as compared to primary cells
• Examples: Lead-acid, nickel-cadmium, lithium-ion

Lead-acid cells are considered the king of batteries. However, today, several other variations of secondary batteries are also commonly used. 

 

The Internal Construction of a Battery 

An ideal battery is made up of the following essential elements

• Two Electrodes: Cathode (positive electrode) and anode (negative electrode)
• The positive electrode composes oxide and sulfide
• The negative electrode includes metal or alloy
• An electrolyte is a medium which serves as an intermediate connection between the positive and negative electrodes
• This electrolyte material is a non-conductor of electrons
• There exists a separator or an insulating layer between the two electrodes
• This layer stands permeable to the ions of the electrolyte

 

The internal construction of a sealed VLRA battery will be different from that of a regular battery. Some of the components of the battery's construction are:

 

• Painted sealed post
• Safety valve or flame arrestor
• Thru-partition construction
• Special active material
• Special grid design
• Special separator
• Polypropylene cover and container
• Heat-sealed case to cover

 

Working Process of a Battery

• During battery discharge, the negative terminal anode releases electrons in the electrolyte.
• The above process is referred to as oxidation.
• Next, the positive terminal cathode accepts these electrons and completes the battery circuit.
• This entire procedure creates an equilibrium while converting the chemical energy into useful electrical energy.
• This ionization of the electrolyte creates an electric current.

 

An Automotive Application: Today and Future

Given below are some of the features of conventional ICT based vehicles and hybrid and electric vehicles. Some of their characteristics are mentioned below:

 

Conventional ICT-Based Vehicles 

• These vehicles initiate the engine in order to propel the auxiliary items
• These vehicles require a lot of energy in cranking amperes for their mobility
• Usually, they propel on a low voltage and utilize acid type AGM for their movement
• The dedicated engine driven alternators keep their vehicles charged throughout

 

New Technology-Based Hybrid and Electric Vehicles

• Batteries feature as an energy source for their propulsion.
• These vehicles propel on high energy type lithium-ion battery cells.
• These vehicles can be charged through engines or power grids.

 

Comparison of Lithium-Ion Chemistries 

There are different varieties of lithium-ion batteries. And each of these batteries has varying characteristics. The table below compares and contrasts the different kinds of lithium chemistries:

 

Characteristic	LFP	NMC	LCO	LMO	LTO
Voltage (in PVC)	3.2	3.6	3.7	3.7	2.4
Specific Energy (in Wh/kg)	90-120	150-220	150-200	100-150	50-80
Energy Density (in Wh/l)	333	580	560	420	177
Charge Rate (in C)	1	0.7-1	0.7-1	0.7-1	1
Charge Voltage (in VPC)	3.5-3.65	4.2	4.2	4.2	2.85
Discharge Rate (in C)	1	1	1	1	10
Life Cycle	2000-4000	1000-2000	500-1000	300-700	3000-7000
Thermal Runaway (in Degree Celsius)	270	210	150	250	N.A
Prone to Thermal Runaway	NO	YES	YES	YES	NO
Applications	Motive power	E-bikes, medical devices	Mobile phones, cameras, laptops, and tablets	Power tools, medical equipment, electric power trains	UPS, electric power trains, solar street lighting

 

The Criteria for Battery Selection

When looking at the design for an electronic device, it is necessary to select the right battery type for the best performance as well as user-friendliness. 

While the specifications may vary based on the device, the primary criteria for battery selection are:

• Battery type (primary or secondary batteries)
• Battery voltage (normal or operating voltage)
• Duty cycle (continuous or intermittent)
• Temperature requirements
• Shelf life
• Specific energy
• Specific power
• Cost
• Service life
• Performance
• Safety and reliability
• Environmental conditions (temperature, atmospheric pressure, humidity, vibration, shock, spin, etc.)
• Cost (initial and operating)
• Maintenance

 

Safety Precautions when Handling Li-Ion Batteries

You may have heard of stories where defective li-ion batteries explode or cause fires at random. Lithium-ion batteries contain many materials and chemical elements that can introduce potential health risks and safety hazards to those who don't handle them with care. 

As a student, if you're working on a project that involves li-ion batteries, it is advisable not to open them unless you are in the recommended environmental conditions.  

This is the second part of a three-part series, you can read the first part here and the third part here. 

 

Furthermore, to gain hands-on training about batteries, enrol yourself in Skill-Lync's Introduction to Battery Technology course.