Glossary

Terms used across the site, from the anode to the Warburg element. Search or filter by topic.

Search terms

53 terms

Activation energy (Eₐ)Materials: The energy barrier an ion must overcome to hop between sites, usually given in eV or kJ/mol. A lower Eₐ means conductivity drops less in the cold. Arrhenius plot →
AnodeElectrochemistry: In battery usage, the negative electrode: where oxidation happens during discharge (for example graphite or hard carbon). Electrochemists strictly name electrodes by the reaction, so the roles swap on charge. Li-ion mechanism →
ArgyroditeMaterials: Li₆PS₅X (X = Cl, Br, I) sulfide electrolytes with a cubic structure and high room-temperature conductivity.
Arrhenius equationMaterials: σ = σ₀ exp(−Eₐ / k_BT): thermally activated conductivity. Plotted as log σ against 1/T, it gives a straight line whose slope is −Eₐ/k_B. Arrhenius plot →
Bragg's lawCrystallography: nλ = 2d sin θ: X-rays reflect constructively from planes spaced d apart only at angle θ. XRD calculator →
Bravais latticeCrystallography: One of the 14 distinct ways to repeat points in 3D, combining a crystal family with a centring (P, S/C, I, F or R).
C-rateElectrochemistry: Current expressed relative to capacity: 1C fully charges or discharges a cell in one hour, C/10 in ten hours and 10C in six minutes. Voltage curves →
CathodeElectrochemistry: In battery usage, the positive electrode: where reduction happens during discharge (for example LiCoO₂, NMC or LiFePO₄). Electrode materials →
CIFCrystallography: Crystallographic Information File: the standard text format for a crystal structure (cell, symmetry and atomic positions). 3D crystal viewer →
Constant phase element (CPE)Methods: Z = 1/[Q(jω)^α]: a non-ideal capacitor used for rough or porous electrodes; α = 1 is an ideal capacitor.
Coulombic efficiencyElectrochemistry: Charge delivered on discharge divided by charge stored on the preceding charge. Values below 100 % mean charge is lost to side reactions.
Crystal familyCrystallography: One of six classes of lattice symmetry: triclinic, monoclinic, orthorhombic, tetragonal, hexagonal and cubic. The hexagonal family holds the trigonal and hexagonal crystal systems. Crystal families →
Cycle lifeElectrochemistry: How many charge–discharge cycles a cell lasts before its capacity falls to a set fraction, often 80 % of the initial value. Degradation →
d-spacingCrystallography: The distance between neighbouring (hkl) planes, set by the lattice parameters.
DendriteMaterials: A branching, needle-like metal deposit that can grow across the separator and short-circuit the cell. Degradation →
Electrochemical impedance spectroscopy (EIS)Methods: Applying a small AC signal over many frequencies to separate processes such as electrolyte resistance, charge transfer and diffusion. EIS simulator →
ElectrolyteElectrochemistry: The medium that conducts ions but not electrons between the electrodes: a liquid (salt in organic solvents), a polymer or a solid. Solid electrolytes →
Equivalent circuitMethods: A network of resistors, capacitors and other elements whose impedance reproduces a measured spectrum, giving physical parameters such as Rct.
Faraday constantElectrochemistry: The charge of one mole of electrons, F = 96 485.332 12 C/mol. It links charge to amount of substance, for example in Q = nF/(3.6 M).
Garnet (LLZO)Materials: Li₇La₃Zr₂O₁₂ and related oxides; the cubic phase is a fast Li⁺ conductor that is stable against lithium metal.
Gibbs energy (ΔG)Electrochemistry: The maximum useful work a reaction can deliver. For a cell, ΔG = −nFE: a negative ΔG means discharge happens spontaneously. Nernst & ΔG calculator →
Grain boundaryMaterials: The interface between crystallites in a polycrystalline material. In ceramic electrolytes it often adds most of the resistance.
Hard carbonMaterials: A disordered, non-graphitizable carbon that stores sodium between turbostratic layers and in nanopores: the standard Na-ion anode.
Hermann–Mauguin symbolCrystallography: The standard notation for a space group, such as Ia3̄d or P4₂/nmc: the lattice centring followed by the symmetry along key directions.
IntercalationElectrochemistry: Reversible insertion of an ion into a host structure without breaking it, such as Li⁺ sliding between graphene layers to form LiC₆.
Ionic conductivity (σ)Materials: How easily ions move through a material, in S/cm. Liquid Li-ion electrolytes reach about 10⁻² S/cm; about 10⁻³ S/cm is a common target for solid electrolytes. Solid-state chart →
Lattice parametersCrystallography: The six numbers a, b, c, α, β, γ describing the unit cell.
Layered oxideMaterials: Cathodes such as LiCoO₂ and NMC in which lithium layers alternate with transition-metal oxide slabs (α-NaFeO₂ structure, R3̄m).
Lithium platingMaterials: Deposition of metallic lithium on the anode surface instead of intercalation, favoured by fast charging, low temperature and high state of charge. Degradation →
Miller indices (hkl)Crystallography: Three integers naming a family of lattice planes; (hkl) planes cut the cell axes at a/h, b/k and c/l.
NASICONMaterials: “Na Super Ionic CONductor”: a framework of corner-sharing tetrahedra and octahedra with wide channels, used for Na⁺ and Li⁺ conductors and for Na₃V₂(PO₄)₃ cathodes.
Nernst equationElectrochemistry: E = E° − (RT/nF) ln Q: how an electrode or cell potential shifts with the activities of reactants and products. Nernst calculator →
Nyquist plotMethods: Impedance shown as −Z″ against Z′, one point per frequency. A semicircle signals a resistor and capacitor in parallel. EIS simulator →
OlivineMaterials: The orthorhombic structure of LiFePO₄ (Pnma), in which Li⁺ moves along 1D channels.
Open-circuit voltage (OCV)Electrochemistry: The cell voltage when no current flows: the difference in electrochemical potential between the two electrodes at a given state of charge.
OverpotentialElectrochemistry: The extra voltage needed to drive a current, caused by resistance, slow electrode reactions and concentration gradients. It lowers the voltage on discharge and raises it on charge. Voltage curves →
OxidationElectrochemistry: Loss of electrons. In a discharging Li-ion cell, lithium stored in the anode is oxidized to Li⁺.
Prussian blue analogueMaterials: Open cyanide frameworks such as Na₂Fe[Fe(CN)₆] (Prussian white) with large channels for Na⁺, used as cheap Na-ion cathodes.
ReductionElectrochemistry: Gain of electrons. In a discharging cell, the cathode's transition metal is reduced as Li⁺ and electrons re-enter it.
SeparatorElectrochemistry: A porous membrane soaked with electrolyte that keeps the electrodes apart, preventing a short circuit while letting ions pass.
Solid electrolyteMaterials: A solid that conducts ions but not electrons, replacing the flammable liquid in solid-state batteries. Solid-state structures →
Solid electrolyte interphase (SEI)Materials: A thin passivating film formed on the anode by electrolyte reduction. It must conduct Li⁺ but block electrons; its slow growth consumes lithium. Degradation →
Space groupCrystallography: The full symmetry of a crystal structure: lattice translations plus rotations, mirrors, glides and screws. There are 230.
Specific capacityElectrochemistry: Charge stored per unit mass of electrode material, usually in mAh/g. Electrode materials →
Specific energyElectrochemistry: Energy per unit mass (Wh/kg), roughly capacity times average voltage. Energy density usually refers to energy per volume (Wh/L).
SpinelMaterials: A cubic structure (Fd3̄m) with 3D ion pathways, found in LiMn₂O₄ cathodes and Li₄Ti₅O₁₂ anodes.
State of charge (SOC)Electrochemistry: How full a cell is, as a percentage of its available capacity.
Superionic conductorMaterials: A solid whose ionic conductivity approaches that of liquids, thanks to a mobile-ion sublattice with many accessible sites (for example LGPS or argyrodites).
Systematic absencesCrystallography: Reflections that are always missing because of lattice centring or glide and screw symmetry, which is how diffraction reveals the space group.
Theoretical capacityElectrochemistry: The capacity if every available site were used: Q = nF / (3.6 M) in mAh/g, with n electrons per formula unit of molar mass M. Electrode materials →
Unit cellCrystallography: The smallest repeating box of a crystal, defined by three edge lengths a, b, c and three angles α, β, γ. Crystal families →
Warburg elementMethods: The impedance of semi-infinite diffusion, Z = σω^(−½)(1 − j), which appears as a 45° line at low frequency.
X-ray diffraction (XRD)Methods: Measuring the angles and intensities at which a crystal diffracts X-rays to identify phases and refine structures. XRD calculator →