Battery Technology Lecture Notes

A comprehensive set of vocabulary flashcards covering basic battery principles, primary and secondary classifications, performance metrics, and specific chemistries like lead-acid, lithium-ion, and emerging technologies.

Primary batteries

Galvanic cells that produce electricity from chemicals sealed inside; they are non-rechargeable (irreversible) because the cell reaction cannot be reversed efficiently, such as dry cells or Lithium copper sulfide cells.

Secondary batteries

Also known as rechargeable cells, storage cells, or accumulators; these can be recharged by passing an external current through them to reverse the spontaneous cell reaction and restore reactants.

Anode (Discharging)

The electrode at which the oxidation reaction occurs, where electrons are produced and anions migrate towards; in a galvanic cell, it has a negative sign.

Cathode (Discharging)

The electrode at which the reduction reaction occurs, where electrons are consumed and cations migrate towards; in a galvanic cell, it has a positive sign.

Electrochemical cell

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

Salt bridge

A tube containing a concentrated electrolyte solution in agar jelly that completes the electrical circuit and enables a cell to function by allowing ion exchange between electrolyte compartments.

Galvanic Cell

An electrochemical cell that produces electricity as a result of a spontaneous redox reaction occurring inside it, converting stored chemical energy directly into electrical energy.

Electrolytic Cell

An electrochemical cell in which a non-spontaneous reaction is driven by an external source of current, converting electrical energy into chemical energy.

Electromotive force (e.m.f.)

Also called cell potential ($E_{cell}$), it is the potential difference that causes a current to flow from an electrode at a higher potential to an electrode at a lower potential, expressed in volts ($V$).

Standard e.m.f. ($E^0_{cell}$)

The emf of a cell when the reactants and products of the cell reaction are at unit concentration/activity, measured at $298\,K$ and $1\,\text{atmospheric pressure}$.

Nernst equation

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

Capacity (C)

The total charge in ampere-hours ($A\,h$) that can be obtained from a battery, determined by the Faraday relation: $C = \frac{m \times n \times F}{M}$.

Cycle Life

The number of charge-discharge cycles a secondary battery can undergo before failure occurs, influenced by chemical composition and morphological changes.

Shelf Life

The period of storage under specified conditions during which a battery retains its performance level, primarily affected by self-discharge.

Energy Density

The ratio of available energy from a battery to its mass ($Wh/kg$) or volume ($Wh/L$).

Lead-Acid Battery

A secondary wet cell battery consisting of lead grids, where the anode is spongy lead ($Pb$) and the cathode is lead dioxide ($PbO_{2}$), both submerged in a sulfuric acid ($H_2SO_4$) electrolyte.

Sulfation

A condition where relatively large $PbSO_4$ crystals grow on lead-acid battery electrodes when left unused in a partially charged state, making them difficult to reduce or oxidize during charging.

Nickel-Metal Hydride (NiMH) battery

A rechargeable battery developed using nickel oxyhydroxide for the positive electrode and a hydrogen-absorbing alloy for the negative electrode.

Lithium-Ion Battery

A rechargeable battery using lithium-carbide intercalate ($Li_xC_6$) as the anode and a transition metal oxide like cobalt dioxide ($CoO_2$) as the cathode.

Thermal Runaway

A catastrophic safety hazard in lithium-ion batteries where internal shorts or overcharging lead to rapid heating, flammable gas emission, and potential fire or explosion.

Sodium-ion batteries (SIBs)

An emerging technology using abundant sodium ($Na$) instead of lithium ($Li$), though performance is challenged because $Na^+$ ions are larger ($1.00\,\text{\AA}$) than $Li^+$ ions ($0.76\,\text{\AA}$).

Lithium-Sulfur (Li-S) Battery

A battery with a very high theoretical energy density ($\sim 2600\,Wh\,kg^{-1}$) using sulfur ($S_8$) as the cathode and lithium metal as the anode.

Polysulfide shuttle effect

A major challenge in Li-S batteries where intermediate lithium polysulfides dissolve in the electrolyte and migrate between electrodes, causing capacity fading.

Redox Flow Battery

An electrochemical system where energy is stored in liquid electrolytes containing dissolved redox-active species, typically stored in external tanks and pumped through the cell.

Vanadium Redox Flow Battery (VRFB)

A type of flow battery that uses vanadium ions in different oxidation states ($V^{2+}, V^{3+}, V^{4+}, V^{5+}$) in both the positive and negative electrolytes.

Fuel Cell

A special galvanic cell in which chemical energy from a fuel-oxidant system (like $H_2-O_2$) is converted directly and continuously into electrical energy.

PEMFC (Proton Exchange Membrane Fuel Cell)

A fuel cell using a solid polymer membrane (like Nafion) as an electrolyte to transport protons ($H^+$) from the anode to the cathode at relatively low temperatures ($\sim 80\,^{\circ}C$).