Electrochemical Power Sources

Electrochemical power sources are devices that convert chemical energy into electrical energy through electrochemical reactions. These power sources play a crucial role in various applications, including portable electronics, electric vehicles, and renewable energy storage. There are several types of electrochemical power sources, each with its own set of characteristics and applications. Here are some of the most common ones:

Faraday’s Laws of Electrolysis

These laws describe the quantitative relationship between the amount of material liberated or deposited during electrolysis and the amount of electric charge passed through the electrolyte.

Polarization or Back e.m.f.:

Polarization occurs in electrolytic cells due to the resistance offered by the electrodes and the electrolyte to the flow of current. Back electromotive force (e.m.f.) opposes the applied voltage during electrolysis.

Value of Back e.m.f.:

The value of back e.m.f. depends on the characteristics of the specific electrolytic cell and the materials involved.

Primary and Secondary Batteries:

Primary batteries are non-rechargeable, while secondary batteries are rechargeable.

Classification of Secondary Batteries based on their Use:

Batteries can be classified based on their application, such as automotive, industrial, or consumer electronics.

Classification of Lead Storage Batteries:

Lead-acid batteries are classified based on their construction and application.

Parts of a Lead-Acid Battery:

Parts include positive and negative plates, separators, electrolyte, and the battery case.

Active Materials of Lead-Acid Cells:

The active materials are lead dioxide (positive plate), sponge lead (negative plate), and sulfuric acid (electrolyte).

Chemical Changes:

During discharge, lead sulfate forms on both plates. During charging, lead sulfate converts back to lead dioxide and sponge lead.

Formation of Plates of Lead-Acid Cells:

The plates are formed through specific processes like the Plante process and the Faure process.

Plante Process:

A method for manufacturing lead-acid battery plates.

Structure of Plant Plates:

The plates have a dense structure and are less porous.

Faure Process:

Another method for manufacturing lead-acid battery plates.

Positive Pasted Plates; Negative Pasted Plates:

Plates with active material pastes applied.

Structure of Faure Plates:

These plates have a more porous structure compared to Plante plates.

Comparison: Plante and Faure Plates:

Differences in structure and manufacturing processes.

Internal Resistance and Capacity of a Cell:

Internal resistance affects the efficiency of the cell, and capacity refers to the amount of charge a battery can store.

Two Efficiencies of the Cell:

Coulombic efficiency and voltage efficiency.

Electrical Characteristics of the Lead-Acid Cell:

Including voltage profiles during charging and discharging.

Battery Ratings:

Specifications indicating the performance and capacity of a battery.

Indications of a Fully-Charged Cell:

Parameters like specific gravity and voltage.

Application of Lead-Acid Batteries:

Widely used in automotive and uninterruptible power supply (UPS) systems.

Voltage Regulators:

Devices that maintain a steady voltage output.

End-Cell Control System:

Monitoring and controlling individual cells in a battery.

Number of End-cells:

The final cells in a battery pack.

Charging Systems:

Methods like constant-current, constant-voltage, and trickle charging.

Sulphation-Causes and Cure:

Formation of lead sulfate and methods to mitigate it.

Maintenance of Lead-Acid Cells:

Practices to prolong battery life.

Mains Operated Battery Chargers:

Chargers are powered by the electrical grid.

Car Battery Charger:

Chargers are designed for automotive batteries.

Automobile Battery Charger:

Chargers specifically for vehicle batteries.

Static Uninterruptible Power Systems:

Backup power systems that provide continuous power during outages.

Alkaline Batteries:

Batteries use an alkaline electrolyte.

Nickel-Iron or Edison Batteries:

Rechargeable batteries with nickel and iron electrodes.

Comparison: Lead-acid and Edson Cells:

Differences between these battery types.

Silver-Zinc Batteries:

Batteries utilizing silver and zinc electrodes.

High-Temperature Batteries:

Batteries are designed for use in elevated temperatures.

Secondary Hybrid Cells:

Batteries combining characteristics of different types.

Fuel Cells:

Devices that convert chemical energy directly into electrical energy.

Hydrogen-Oxygen Fuel Cells:

Fuel cells use hydrogen and oxygen as reactants.

Batteries for Aircraft:

Specific batteries are designed for aviation applications.

Batteries for Submarines:

Batteries are used in submarines for underwater propulsion.

Battery

A battery is an electrochemical device that converts stored chemical energy into electrical energy via redox (oxidation-reduction) reactions. At its core, a battery comprises one or more cells; each cell contains two electrodes (a negative anode and a positive cathode) and an electrolyte that facilitates ion movement between them. This process creates a flow of electrons through an external circuit to supply power to devices. Batteries can be divided into two broad categories:

Primary Batteries: Often termed “use-and-throw” batteries, these operate on chemical reactions that are irreversible. Once the reactants are depleted, the battery cannot be recharged.

Secondary Batteries: Also known as rechargeable batteries, these rely on reversible chemical reactions, allowing them to be charged and discharged many times.

This versatility makes batteries indispensable—from powering small consumer electronics to driving electric vehicles to providing backup power in larger systems 

Fuel Cell

A fuel cell is an electrochemical device that continuously converts the chemical energy contained in a fuel (commonly hydrogen) and an oxidizing agent (typically oxygen from air) directly into electricity. Unlike batteries—where all the reactants are pre-stored—fuel cells require a constant supply of fuel and oxidizer. Key characteristics include:

Continuous Operation: As long as fuel and oxygen are provided, a fuel cell can produce electricity steadily, making it ideal for long-duration applications.

Mechanism: At the anode, fuel molecules undergo oxidation, releasing electrons that travel through an external circuit, while ions migrate through the electrolyte to the cathode. There, they recombine with electrons and oxygen to form water (and sometimes heat), completing the reaction.

Applications: Fuel cells are used in space missions, stationary power generation, vehicles (including buses and cars), and various backup power systems because of their high efficiency and low-emission profile .

Supercapacitor

A supercapacitor (or ultracapacitor) is an advanced energy storage device that bridges the gap between conventional capacitors and batteries. Unlike traditional capacitors that store energy solely by charge separation across a dielectric, supercapacitors employ a combination of:

Electrostatic Double-Layer Capacitance (EDLC): This mechanism involves the separation of charge at the interface between a high-surface-area electrode (often made of activated carbon or graphene) and an electrolyte.

Pseudocapacitance: This arises from fast, reversible Faradaic redox reactions at the electrode’s surface, providing additional energy storage capacity.

Due to these dual mechanisms, supercapacitors offer an exceptionally high capacitance—storing 10 to 100 times more energy per unit mass than traditional capacitors—and can charge and discharge much faster than batteries. Their rapid power delivery makes them ideal for applications requiring quick bursts of energy (like regenerative braking systems in vehicles or short-term power backup in electronics), though they typically offer lower energy density than batteries over longer durations