Electrochemistry and Battery Technology

A complete set of vocabulary flashcards covering the core principles of electrochemistry, including battery technologies, fuel cell mechanics, and metal finishing processes.

Electrochemistry

The study of the behavior of electrolytes in solution and the interconversion of chemical and electrical energies, specifically chemical changes due to electric current flow and vice-versa.

Electronic conductors

Substances like metals and alloys that conduct electricity through a flow of electrons without undergoing physical or chemical changes.

Electrolytic conductors (Electrolytes)

Molten salts or solutions that conduct electricity due to the migration of ions, which typically undergo decomposition or compositional changes during the process.

Electrochemical cell

A single arrangement consisting of two electrodes and one or more electrolytes that converts chemical energy into electrical energy or vice versa.

Salt bridge

A tube containing a concentrated electrolyte like $KCl$, $KNO_3$, or $NH_4NO_3$ in agar jelly that completes the electrical circuit and minimizes liquid junction potential.

Galvanic Cells

Electrochemical cells that produce electricity from spontaneous redox reactions occurring within them.

Electrolytic Cells

Electrochemical cells that use an external source of current to drive non-spontaneous chemical reactions.

Anode

The electrode where oxidation occurs, electrons are produced, and anions migrate towards; it has a negative sign in galvanic cells.

Cathode

The electrode where reduction occurs, electrons are consumed, and cations migrate towards; it has a positive sign in galvanic cells.

Daniel cell

A specific galvanic cell consisting of a zinc rod in $ZnSO_4$ solution and a copper rod in $CuSO_4$ solution.

Liquid junction potential ($E_j$)

The potential established at the junction of two electrolytes caused by the unequal migration speeds of cations and anions across the boundary.

Electromotive force (EMF)

The potential difference that causes current to flow from a higher potential electrode to a lower potential electrode, expressed in volts ($V$).

Standard emf ($E^0_{cell}$)

The EMF of a cell measured at $2980\,K$ and $1$ atmospheric pressure when all reactants and products are at unit concentration.

Poggendorff’s compensation method

The principle used to measure EMF accurately where the unknown cell potential is balanced by an equal and opposite known EMF to reach a null point.

Standard cell

A cell providing a highly reproducible and constant EMF with a negligible temperature coefficient, such as the Weston cadmium cell.

Single electrode potential

The measure of the tendency of a metallic electrode to lose or gain electrons when in contact with a solution of its own salt.

Helmholtz electrical double layer

The thin layer of positive and negative ions formed at the interface between an electrode and the electrolyte at equilibrium.

Standard Hydrogen Electrode (SHE)

A primary reference electrode where the potential is arbitrarily fixed at zero, consisting of platinum in contact with $1\,M\,H^+$ and $H_2$ gas at $1$ atmosphere.

Electrochemical series

A list of elements arranged in increasing order of their standard electrode potentials.

Nernst equation

A mathematical expression relating electrode potential to the concentration of species in solution: $E = E^0 + \frac{2.303RT}{nF} \text{log}[M^{n+}]$.

Calomel electrode

A secondary reference electrode consisting of mercury and mercurous chloride ($Hg_2Cl_2$) in contact with a $KCl$ solution.

Ion-selective electrode

An electrode sensitive to a specific ion whose potential depends on the activity of that ion, such as the glass electrode for $H^+$.

Asymmetry potential ($E_{asym}$)

A small, unpredictable potential in glass electrodes caused by surface strain, mechanical abrasion, or chemical etching.

Primary Cells

Non-rechargeable galvanic cells where chemicals are sealed during manufacture and the reaction cannot be reversed efficiently.

Secondary cells

Rechargeable batteries (accumulators) that can be restored to a non-equilibrium state by passing an external current in the opposite direction.

Lithium-ion battery

A secondary battery using a lithium-graphite intercalation compound ($Li_xC_6$) as the anode and a lithiated metal oxide like $LiCoO_2$ as the cathode.

Fuel cell

A galvanic cell that converts chemical energy from a fuel-oxidant system (constantly supplied from outside) directly into electrical energy.

Proton exchange membrane fuel cell (PEMFC)

A fuel cell using a solid polymer electrolyte and platinum catalysts that operates at low temperatures around $80\,^\text{o}C$.

Metal finishing

The electrodeposition of an adherent metallic film on a substrate to modify surface properties like corrosion resistance using electroplating or electroless plating.

Decomposition potential ($E_D$)

The minimum external voltage required to sustain continuous electrolysis and overcome the back EMF produced by products at the electrodes.

Overvoltage ($\eta$)

The difference between the actual applied EMF required for continuous electrolysis (often due to gas evolution) and the theoretical reversible EMF.

Concentration polarization

A drop in current or a requirement for higher potential occurring when the transport of reactants to the electrode surface is slower than the electrode reaction rate.

Kinetic (Activation) polarization

Polarization caused by slow steps in the electrochemical reaction itself, such as charge transfer or adsorption, requiring activation energy.

Electroless plating

A method of depositing a metal film on a substrate (conductor or non-conductor) from a salt solution using a chemical reducing agent instead of electrical energy.