Master Glossary and Element Data
Every term defined in one place, with the element table the rest of the series argues from — atomic mass, electrode potential, ionic radius, electronegativity, crustal abundance and EV role.
The Periodic Table of the EV · Part 6 — Reference · Chapter 13 · 15 min read
Part 6 — Reference
Glossary and element data
Every term defined in one place, and the table the rest of the series argues from.
A reference chapter rather than an argument. Every term used across the previous twelve chapters is defined here in a sentence or two, followed by the master element table and a one-page summary of the whole case.
~60
Terms defined
23
Elements in the reference table
12
Chapters this covers
1
Page of summary
13.1 — Glossary — A to E
| Term | Definition |
|---|---|
| Activation energy (E_a) | Energy barrier a process must overcome; appears in the Arrhenius equation. |
| Antisite defect | An atom occupying the crystallographic site of a different species — the Ni²⁺-on-Li⁺ problem of chapter 4. |
| Arrhenius equation | D = D₀·exp(−E_a/k_BT); describes the exponential temperature dependence of rate processes. |
| Band structure | The allowed energy ranges for electrons in a solid. |
| BET surface area | Specific surface area in m²/g, measured by gas adsorption. Predicts SEI formation and first-cycle loss. |
| Bragg’s law | nλ = 2d sin θ; relates diffraction angle to lattice spacing. |
| Bruggeman relation | D_eff = D·ε^1.5; corrects transport properties for porous geometry. |
| Butler–Volmer equation | Relates current density to overpotential at an electrode. Current rises exponentially with overpotential. |
| Calendering | Roll-pressing an electrode to set thickness, density and porosity. |
| Catenation | An element’s ability to bond to itself in chains or rings — carbon’s defining property. |
| Charge density (ionic) | Charge per ion volume; drives solvation strength and binding. |
| Charge-transfer resistance (R_ct) | Resistance of the electron-transfer step at the electrode/electrolyte interface, including desolvation. |
| Coercivity (H_c) | The reverse magnetic field required to demagnetise a material. |
| Conversion reaction | An electrode reaction that breaks and reforms the host structure, as opposed to intercalation. |
| Coordination number | The number of nearest-neighbour atoms around a central atom. |
| Crystal field splitting (Δ_o) | Energy separation of d orbitals caused by surrounding ligands. |
| Curie temperature | The temperature above which ferromagnetism vanishes. |
| Degeneracy | Two or more electronic states having the same energy. |
| Desolvation | Stripping solvent molecules from an ion before it enters the electrode. |
| Dielectric constant (ε_r) | The factor by which a medium reduces electrostatic force; screens ion pairing so a salt can dissociate. |
| Donor number (DN) | A measure of a solvent’s electron-donating, cation-solvating strength. |
| Effective nuclear charge (Z_eff) | The net nuclear attraction felt by a valence electron after shielding. |
| Electrochemical stability window (ESW) | The voltage range in which an electrolyte does not decompose. |
| Electronegativity (χ) | The tendency of a bonded atom to attract shared electrons. |
| Exchange current density (i₀) | The intrinsic rate of an electrode reaction at equilibrium. |
13.2 — Glossary — F to M
| Term | Definition |
|---|---|
| Faraday constant (F) | 96,485 C/mol — the charge carried by one mole of electrons. |
| Fermi level | The energy up to which electron states are filled in a solid. |
| Gibbs free energy (ΔG) | Thermodynamic driving force; ΔG = −nFE. |
| Goldschmidt classification | Lithophile / chalcophile / siderophile / atmophile grouping of the elements by Earth differentiation. |
| Gurley number | Air permeability of a separator; a proxy for tortuosity. |
| High-spin / low-spin | Whether d electrons maximise unpaired spins or pair up in the lower orbital set; decided by Δ_o versus pairing energy. |
| HOMO / LUMO | Highest occupied and lowest unoccupied molecular orbital; they set the oxidation and reduction limits of an electrolyte. |
| Hybridisation | Mixing of atomic orbitals (sp, sp², sp³) to form directional bonds. |
| Hydration / solvation enthalpy | Energy released when a gaseous ion is surrounded by solvent molecules; scales roughly as z²/r. |
| Inductive effect | Transmission of electron density through bonds, shifting a distant atom’s redox energy — the LFP mechanism. |
| Intercalation | Reversible insertion of a guest ion into a host lattice’s interstitial sites without destroying the framework. |
| Ionic radius | Effective radius of an ion in a crystal for a given charge and coordination number (Shannon). |
| Ionisation energy (IE) | Energy required to remove an electron from a gaseous atom. |
| Jahn–Teller distortion | Spontaneous geometric distortion that lifts electronic degeneracy — the d⁴ Mn³⁺ problem. |
| MacMullin number (N_M) | Ratio of bulk to effective electrolyte resistivity in a porous medium; τ/ε. |
| Magnetocrystalline anisotropy | Preference of magnetisation for a specific crystal direction; the source of coercivity. |
| Migration barrier | Activation energy for an ion hopping between adjacent lattice sites. |
13.3 — Glossary — N to Z
| Term | Definition |
|---|---|
| Overpotential (η) | Voltage in excess of the thermodynamic requirement, needed to drive a reaction at a given rate. |
| Oxidation state | The notional charge an atom would carry if all its bonds were fully ionic. |
| Passivation | Formation of a protective surface film that halts further reaction. |
| Percolation threshold | The volume fraction of conductive additive at which a connected network first spans the electrode. |
| Polarising power | A cation’s ability to distort neighbouring electron clouds; scales as z/r². |
| Porosity (ε) | Void fraction of an electrode, filled with electrolyte. |
| Redox couple | A pair of oxidation states an element cycles between, e.g. Co³⁺/Co⁴⁺. |
| Scherrer equation | Relates XRD peak broadening to crystallite size; D = Kλ/(β cos θ). |
| SEI (Solid Electrolyte Interphase) | The passivating film formed by electrolyte reduction on the anode; conducts Li⁺, blocks electrons. |
| Shielding (σ) | Reduction of nuclear attraction on valence electrons by inner electrons. |
| Site preference energy | Energetic preference of an ion for one crystallographic site over another. |
| Specific capacity | Charge stored per unit mass in mAh/g; Q = nF/(3.6M). |
| Staging | Ordered, stepwise filling of graphite galleries during lithiation, producing the stepped voltage profile. |
| Standard electrode potential (E°) | Half-cell potential measured against the standard hydrogen electrode. |
| Stokes–Einstein relation | D = k_BT/(6πηr); links diffusion coefficient to solvent viscosity. |
| Tap density | Density of a powder after standardised settling; predicts volumetric energy density. |
| Tortuosity (τ) | Ratio of actual to straight-line ion path length through a porous medium. |
| Transference number (t₊) | Fraction of ionic current carried by the cation; only 0.2–0.4 in conventional electrolytes. |
| Van der Waals force | Weak attraction from induced dipoles; what holds graphite layers together. |
| Warburg impedance | Diffusion-limited contribution to electrochemical impedance; the 45° line at low frequency. |
| Weakly coordinating anion | An anion with delocalised charge that dissociates readily from its cation. |
13.4 — Element reference data
Standard-condition literature values for representative materials. Ionic radii are Shannon values for the species named, at six-coordination.
| Element | Z | Group/Block | M (g/mol) | E° (V vs SHE) | Ionic radius (pm) | χ | Abundance (ppm) | EV role |
|---|---|---|---|---|---|---|---|---|
| H | 1 | 1, s | 1.008 | 0.00 | — | 2.20 | 1,400 | Fuel cells |
| Li | 3 | 1, s | 6.94 | −3.045 | 76 (Li⁺) | 0.98 | 20 | Charge carrier |
| C | 6 | 14, p | 12.01 | — | — | 2.55 | 200 | Anode, additive |
| O | 8 | 16, p | 16.00 | +1.23 | 140 (O²⁻) | 3.44 | 461,000 | Cathode framework |
| F | 9 | 17, p | 19.00 | +2.87 | 133 (F⁻) | 3.98 | 585 | Salt, binder, SEI |
| Na | 11 | 1, s | 22.99 | −2.71 | 102 | 0.93 | 23,600 | Na-ion |
| Mg | 12 | 2, s | 24.31 | −2.37 | 72 | 1.31 | 23,300 | Candidate, alloys |
| Al | 13 | 13, p | 26.98 | −1.66 | 53.5 | 1.61 | 82,300 | Collector, dopant |
| Si | 14 | 14, p | 28.09 | — | 40 (Si⁴⁺) | 1.90 | 282,000 | Anode, electronics |
| P | 15 | 15, p | 30.97 | — | 38 (P⁵⁺) | 2.19 | 1,050 | LFP, salt |
| S | 16 | 16, p | 32.06 | — | 184 (S²⁻) | 2.58 | 350 | Li-S candidate |
| K | 19 | 1, s | 39.10 | −2.93 | 138 | 0.82 | 20,900 | Candidate |
| Ca | 20 | 2, s | 40.08 | −2.87 | 100 | 1.00 | 41,500 | Candidate |
| Ti | 22 | 4, d | 47.87 | −1.63 | 60.5 (Ti⁴⁺) | 1.54 | 5,650 | LTO, dopant |
| Mn | 25 | 7, d | 54.94 | −1.18 | 64.5 (Mn³⁺) | 1.55 | 950 | NMC, LMO |
| Fe | 26 | 8, d | 55.85 | −0.44 | 78 (Fe²⁺) | 1.83 | 56,300 | LFP, steel |
| Co | 27 | 9, d | 58.93 | −0.28 | 54.5 (Co³⁺ LS) | 1.88 | 25 | NMC, NCA |
| Ni | 28 | 10, d | 58.69 | −0.25 | 69 (Ni²⁺) | 1.91 | 84 | NMC, NCA |
| Cu | 29 | 11, d | 63.55 | +0.34 | 73 (Cu²⁺) | 1.90 | 60 | Collector, windings |
| Zn | 30 | 12, d | 65.38 | −0.76 | 74 | 1.65 | 70 | Aqueous batteries |
| Ga | 31 | 13, p | 69.72 | −0.53 | 62 (Ga³⁺) | 1.81 | 19 | GaN electronics |
| Nd | 60 | f | 144.24 | −2.32 | 98.3 (Nd³⁺) | 1.14 | 28 | Magnets |
| Dy | 66 | f | 162.50 | −2.30 | 91.2 (Dy³⁺) | 1.22 | 5.2 | Magnet coercivity |
| Pt | 78 | 10, d | 195.08 | +1.19 | 62.5 (Pt⁴⁺) | 2.28 | 0.005 | Fuel cell catalyst |
13.5 — The one-page summary
13.5.1 — Why lithium
Lithium won because it occupies a unique point in the periodic table: the top-left corner, where an element is simultaneously the lightest metal, the most electropositive element in aqueous conditions, and the source of the only cation small enough to intercalate quickly while carrying only a single charge. Every alternative sacrifices at least one of those three.
13.5.2 — Why the cathode is a transition metal
Only partially filled d orbitals give reversible multi-valent redox at high potential. Nickel supplies electrons, cobalt supplies structure, manganese supplies cheapness with a Jahn–Teller liability, and iron supplies abundance once phosphorus’s inductive effect lifts its voltage into the useful range.
13.5.3 — Why the anode is carbon
sp² hybridisation produces a layered, conductive, van-der-Waals-bonded host that lithium — and essentially only lithium — enters cheaply and reversibly. Silicon stores ten times as much and expands 280 per cent doing it; LTO cannot plate lithium and pays for that twice.
13.5.4 — What the non-metals do
Oxygen makes the ionic lattice that holds metals at high oxidation state. Phosphorus tunes redox energy and locks oxygen in. Fluorine delocalises anion charge to make the electrolyte conduct and to widen its stability window — and generates HF as the price.
13.5.5 — Why the foils are what they are
Copper and aluminium are assigned by standard electrode potential, not by cost. Copper is noble enough to survive at 0.1 V; aluminium passivates well enough to survive at 4.2 V; and neither can do the other’s job.
Important
And beneath all of it sits transport physics — porosity, tortuosity, and the L²/D diffusion time — which decides whether a thermodynamically excellent material is a product or a laboratory curiosity.
LFP is the standing proof: chemically ideal, kinetically hopeless, and rescued entirely by nano-sizing and carbon coating.
Chapter summary
- ✓Lithium’s dominance rests on one unique combination: lightest metal, most electropositive in aqueous conditions, and the only small monovalent cation.
- ✓The d-block supplies reversible redox, the p-block supplies framework and electrolyte, the s-block supplies the carrier, and the f-block supplies the magnets.
- ✓Polarising power (z/r²) is the single number that best predicts whether an ion can work at all — which is why multivalent chemistries stay in laboratories.
- ✓Every cathode is a mixture because no single element provides more than one of the properties a cathode needs.
- ✓Transport physics decides whether good chemistry becomes a product. LFP is the proof in both directions.
Frequently asked questions
What is the one-sentence version of why lithium won?+
Lithium occupies a unique point in the periodic table — the top-left corner, where an element is simultaneously the lightest metal, the most electropositive element in aqueous conditions, and the source of the only cation small enough to intercalate quickly while carrying only a single charge. Every alternative sacrifices at least one of those three.
What is the difference between intercalation and a conversion reaction?+
Intercalation is the reversible insertion of a guest ion into the pre-existing interstitial sites of a host crystal without destroying the framework — graphite taking lithium into its galleries, or a layered oxide taking it between metal-oxide sheets. A conversion reaction breaks and reforms the host structure entirely, as in lithium–sulfur where the whole S₈ ring is consumed. Conversion gives far higher capacity because every atom participates, but reversibility, volume change and dissolution are much harder to control.
Which single number best predicts whether an ion can work in a battery?+
Polarising power, roughly z/r². Taking lithium as 1.00, sodium is 0.55, magnesium 2.23 and aluminium 6.06. It predicts migration barrier, solvation strength and desolvation difficulty simultaneously, which is why multivalent chemistries with excellent theoretical capacity remain laboratory subjects. Ionic radius alone does not predict it — Mg²⁺ at 72 pm is smaller than Li⁺ at 76 pm and still fails.
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The Periodic Table of the EV is an original educational series on the materials science of electric vehicles. All values are standard-condition literature figures for representative materials, not measured data from a specific product, and sources differ on several of them. Always verify against the specific material datasheet in use before making design, purchasing or certification decisions.