Battery voltage and capacity in non-equilibrium

Source: TYCORUN Battery Swap

Polarization Effects in Batteries

Polarization effects play a crucial role in the operation of batteries, impacting their efficiency and performance. These effects result in deviations of voltage and capacity from equilibrium values, affecting how a battery can be charged and discharged.

Types of Polarization

Polarization in batteries is caused by resistive drops, kinetic overvoltage, and mass transport overvoltage. Resistive drops occur due to internal resistance in the battery components, affecting the flow of electrons. Kinetic overvoltage relates to the rate at which chemical reactions occur, while mass transport overvoltage concerns the movement of reactants to the electrode.

Effect on Battery Efficiency

During discharging, the battery voltage is lower than in equilibrium, while charging requires a higher voltage. These deviations impact the efficiency of the battery, influencing its capacity and overall performance.

Reaction Rates and Polarization

The rates of chemical reactions within a battery are crucial for its operation. Factors such as mass transport of reactants to the electrode and activation energy for reactions determine the efficiency of the battery.

Mass Transport Overvoltage

At high charge/discharge rates, mass transport overvoltage becomes significant. It occurs when the battery depletes reactants faster than they can diffuse to the electrode, leading to voltage drops during discharge and higher voltages during charging.

Activation Overvoltage

Activation overvoltage should be minimized to enhance battery efficiency. It refers to the additional voltage required for reactions to proceed, impacting the charging and discharging processes.

Resistive Drops in Batteries

Resistive drops contribute to overvoltage in batteries, affecting their performance. Components like electrode resistance and surface characteristics influence how efficiently a battery can be charged and discharged.

Secondary Reactions

Aside from the main redox reactions, batteries may experience secondary reactions that reduce efficiency. Side reactions, such as water electrolysis, can lead to gassing, self-discharge, and electrode corrosion, impacting overall battery performance.

Physical State of the Electrodes

The physical state of electrodes is crucial for battery operation. Large surface areas, achieved through porous materials, facilitate efficient reactions and prevent coverage by reaction products, ensuring optimal battery performance. Changes in electrode morphology and structure during charging/discharging cycles can impact battery capacity and longevity.

Source: Wiley Online Library