spore: profile
id: ethylene-carbonate
spore_version: 0.2
family: lithium
name: Ethylene carbonate
abbreviation: EC
role: high-permittivity electrolyte solvent and SEI former
category: energy
type: electrolytes
summary: |
  Ethylene carbonate is a cyclic carbonate that is a colourless solid at room temperature, melting at 36.4 degC. In lithium-ion cells it is mixed with low-viscosity linear carbonates because its dielectric constant is very high (89.78 at 40 degC) and because it reduces on a graphite anode to form the protective solid electrolyte interphase. The same high melting point is its main weakness in the cold.
best_for: Dissolving lithium salt (dielectric constant 89.78 at 40 degC) and building a protective film on graphite, which propylene carbonate does not do
weakest_at: 'Cold temperatures: it melts at 36.4 degC, so EC-rich electrolytes need co-solvents to stay liquid and conductive at -20 degC and below'
identity:
  formula: C3H4O3
  cas: 96-49-1
  source: pubchem-ec
  where: Compound record CID 7303 (CAS 96-49-1; molecular formula C3H4O3, computed by PubChem 2.2)
tags:
  environments: []
  stresses:
    - extreme-cold
  applications:
    - batteries
properties:
  - benchmark: melting_point
    label: Melting point (handbook value via PubChem)
    value: 36.4
    unit: degC
    scope: material
    conditions:
      pressure: not stated
      purity: not stated
    method: Handbook value (CRC Handbook of Chemistry and Physics, 79th ed., p. 3-145) as quoted in the HSDB section of the PubChem record
    status: ground
    note: A 2005 paper lists 37 degC in its solvent table, and Xiang et al. state 36.4 degC independently of PubChem. Roughly 35 to 38 degC appears in supplier listings, which were not opened as primary sources here.
    source: pubchem-ec
    where: Experimental Properties > Melting Point (HSDB; Lide 1998-1999)
  - benchmark: melting_point
    label: Melting point (as stated in a PNNL battery paper)
    value: 36.4
    unit: degC
    scope: material
    conditions:
      context: stated while explaining why EC limits the service temperature range of lithium-ion cells
      comparison: propylene carbonate melts at -48.8 degC in the same sentence
    method: Value quoted in the introduction of the paper (no measurement made by the authors)
    status: ground
    source: xiang2015
    where: Section 1 Introduction, first column
  - benchmark: boiling_point
    label: Boiling point
    value: 248
    unit: degC
    scope: material
    conditions:
      pressure: 760 mm Hg (second PubChem entry)
    method: Handbook value (CRC Handbook of Chemistry and Physics, 79th ed., p. 3-145) as quoted in the HSDB section of the PubChem record
    status: ground
    note: The 2005 Li et al. solvent table gives 238 degC, a different value from a different source.
    source: pubchem-ec
    where: Experimental Properties > Boiling Point (HSDB)
  - benchmark: flash_point
    label: Flash point (open cup)
    value: 143
    unit: degC
    scope: material
    conditions:
      method: open cup
      original_units: 290 degF
    method: Hawley's Condensed Chemical Dictionary, 11th ed. (1987), p. 485, as quoted in the HSDB section of the PubChem record
    status: ground
    note: PubChem lists 143 degC with no method in one entry; the Hawley entry names the open-cup method. This is the neat solvent, not a mixed electrolyte, whose flash point depends on its co-solvents and was not found in an opened source.
    source: pubchem-ec
    where: Experimental Properties > Flash Point (HSDB; Hawley 11th ed.)
  - benchmark: density
    label: Density (liquid)
    value: 1.3214
    unit: g/cm3
    scope: material
    conditions:
      temperature: 39 degC (liquid, above the melting point)
      note: the PubChem entry gives the value with no unit; it is specific gravity relative to water, treated here as g/cm3
    method: Handbook value (CRC Handbook, 79th ed., p. 3-145) as quoted in the HSDB section of the PubChem record
    status: ground
    note: A second PubChem entry gives 1.322 at 40 degC.
    source: pubchem-ec
    where: Experimental Properties > Density (HSDB)
  - benchmark: vapor_pressure
    label: Vapour pressure
    value: 0.0098
    unit: mm Hg
    scope: material
    conditions:
      temperature: 25 degC
    method: Howard and Meylan, Handbook of Physical Properties of Organic Chemicals (1997), as quoted in the HSDB section of the PubChem record
    status: ground
    note: A second PubChem entry gives 0.01 mm Hg at 20 degC.
    source: pubchem-ec
    where: Experimental Properties > Vapor Pressure (HSDB)
  - benchmark: dielectric_constant
    label: Dielectric constant (relative permittivity)
    value: 89.78
    unit: dimensionless
    scope: material
    conditions:
      temperature: 40 degC (footnote 1 of the table; the table heading says 25 degC)
      state: liquid
      comparison: PC 65, DMC 3.1, EMC 2.9, DEC 2.8 in the same table
    method: Table of physicochemical properties of carbonate solvents compiled from references 2 to 4 of the paper
    status: ground
    note: The table heading says 25 degC but footnote 1 marks the EC value as measured at 40 degC, which makes sense because EC is solid at 25 degC. The paper takes the value from earlier literature, not a measurement of its own.
    source: li2005
    where: Table 1, row Dielectric constant, footnote 1
  - benchmark: viscosity
    label: Viscosity
    value: 1.93
    unit: mPa s
    scope: material
    conditions:
      temperature: 40 degC (footnote 1)
      state: liquid
      comparison: PC 2.5, DMC 0.5889, EMC 0.6478, DEC 0.7534 mPa s in the same table
    method: Table of physicochemical properties of carbonate solvents compiled from references 2 to 4 of the paper (printed as 1.93 x 10^-3 Pa s)
    status: ground
    note: Unit converted from 10^-3 Pa s to mPa s (identical). Same 25 degC heading and 40 degC footnote caveat as the dielectric constant.
    source: li2005
    where: Table 1, row Viscosity, footnote 1
  - benchmark: oxidation_potential
    label: Oxidation potential
    value: 5.8
    unit: V vs Li+/Li
    scope: material
    conditions:
      electrode: glassy carbon surface
      temperature: 20 degC (footnote 2)
    method: Table value compiled from earlier literature (references 2 to 4 of the paper)
    status: ground
    note: PC is listed at 5.8 V and DMC at 5.7 V in the same row.
    source: li2005
    where: Table 1, row Oxidization potentials, footnote 2
  - benchmark: molecular_weight
    label: Molecular weight
    value: 88.06
    unit: g/mol
    scope: material
    conditions:
      computed_by: PubChem 2.2 (release 2025.04.14)
    method: Computed from the molecular formula by PubChem
    status: calculated
    source: pubchem-ec
    where: Computed Properties > Molecular Weight
  - benchmark: refractive_index
    label: Refractive index
    value: 1.4148
    unit: dimensionless
    scope: material
    conditions:
      temperature: 50 degC
    method: CRC Handbook, 79th ed., p. C-145, as quoted in the HSDB section of the PubChem record
    status: ground
    source: pubchem-ec
    where: Experimental Properties > Refractive Index (HSDB)
  - benchmark: acute_oral_ld50
    label: Acute oral toxicity, rat
    value: 10
    unit: g/kg
    scope: material
    conditions:
      species: rat
      route: oral
    method: Sax's Dangerous Properties of Industrial Materials, 9th ed. (1996), p. 1741, as quoted in the PubChem record
    status: ground
    note: Second-hand through a handbook that PubChem quotes; the original study was not opened. Notifiers to ECHA still classify the substance as harmful if swallowed (H302, 56.4% of reports), so a high LD50 does not mean it is harmless.
    source: pubchem-ec
    where: Safety and Hazards > Toxicity (HSDB; Sax 9th ed.)
  - benchmark: sei_thickness
    label: Thickness of the EC-derived SEI on graphite
    value: 50
    unit: nm
    scope: cell
    conditions:
      range: 30 to 50 nm (upper end entered)
      electrode: graphitic carbon anode
      description: self-limiting, passivating layer
    method: Statement in the introduction of a simulation paper, taken from earlier experiments (not calculated by the authors)
    status: ground
    note: The paper gives the thickness as 30-50 nm and says the layer contains Li2CO3, lithium ethylene dicarbonate and salt decomposition products. A separate neutron reflectometry result quoted by Peng (2022, Section 4) found a thinner early layer of about 0.5 nm after 20 voltammetry cycles, growing to about 1.0 nm on copper.
    source: leung2010
    where: Introduction, second paragraph
corrosion:
  - environment: Water, alkalies and strong acids
    headline: EC hydrolyses; alkalies make it fast above 125 degC.
    effect: A chemical handbook quoted by PubChem says the dry ester hydrolyses rapidly above 125 degC with alkalies and more slowly with strong acids, and decomposes slowly at 200-250 degC. The same entry calls it stable under normal storage conditions, with little change in freezing point and no colour deepening after 2 months at 40 degC. This is the stability of the neat chemical, not a corrosion rate on any spacecraft material.
    rating: unknown
    conditions:
      basis: Riddick et al., Techniques of Chemistry, 4th ed., Vol. II (1985), p. 989, as quoted in PubChem (HSDB)
    source: pubchem-ec
    where: Stability/Shelf Life and Decomposition entries (HSDB)
risks:
  hazards:
    - text: 'PubChem aggregates 543 company reports from 21 ECHA C&L notifications. Signal word Warning with pictograms GHS07 and GHS08. Hazard statements: H302 harmful if swallowed (56.4% of reports), H315 skin irritation (13.1%), H319 serious eye irritation (74.2%), H373 may cause damage to organs through prolonged or repeated exposure (56.2%). Of the 543 reports, 31 (5.7%) say the chemical does not meet GHS hazard criteria, so notifiers do not fully agree.'
      ghs:
        - H302
        - H315
        - H319
        - H373
      source: pubchem-ec
      where: Safety and Hazards > GHS Classification (ECHA C&L Inventory aggregation)
    - text: Combustible when exposed to heat or flame and can react with oxidizing materials. When heated to decomposition it emits acrid smoke and irritating fumes.
      ghs: []
      source: pubchem-ec
      where: Stability and Reactivity; Decomposition entries (HSDB; Sax 9th ed., 1996, p. 1741)
  failure_risks:
    - mode: Freezing of EC-rich electrolyte in the cold
      trigger: Temperatures near or below the 36.4 degC melting point of pure EC
      consequence: The paper says the high melting point of EC imposes a narrow service temperature range on most lithium-ion cells. JPL researchers wanted to reach -40 degC and noted that an EC + DEC + DMC (33:33:34) electrolyte performed excellently at -20 degC, so cold limits are set by the whole mixture, not EC alone.
      severity: moderate
      source: xiang2015
      where: Section 1 Introduction (Smart et al. Introduction for the -20 and -40 degC context)
    - mode: Poor SEI if EC is replaced by propylene carbonate
      trigger: Pure PC-based electrolyte on a graphite anode
      consequence: The paper says PC is seldom used because it co-intercalates into graphite and eventually exfoliates it, and that PC's inability to form a protective SEI restricts its use to below 10% of the electrolyte. This is the reason EC stays in the mixture despite its melting point.
      severity: high
      source: xiang2015
      where: Abstract; Section 1 Introduction
  side_effects:
    - text: On first charge EC decomposes on graphite and releases gas. The Leung and Budzien introduction notes that C2H4 and CO gases have been detected in experiments.
      affects: Cell gas generation during formation cycles
      source: leung2010
      where: Introduction, second paragraph
    - text: Peng's calculation proposes the reaction 2Li+ + 2EC to 2 CH2CH2OCO2Li to (CH2OCO2Li)2 + C2H4, so ethylene is a by-product of making lithium ethylene dicarbonate. The same paper notes that a recent experiment has called into question whether LEDC is the majority SEI species.
      affects: Composition of the SEI
      source: peng2022
      where: Section 3.1.3; Section 1
  handling:
    - text: 'PubChem lists these precautionary codes among the ECHA notifications: P260, P264, P270, P280, P301+P317, P302+P352, P305+P351+P338, P330, P501 and others (full list in the record). Flush the eyes immediately with water if they are contaminated, and do not induce vomiting (HSDB first-aid entry, which cites guidance written for ethylene glycol).'
      source: pubchem-ec
      where: GHS Classification, precautionary statement codes; First Aid entry (HSDB; Bronstein and Currance 1994)
  mitigations:
    - text: 'Mix EC with linear carbonates: JPL used 1.0 M LiPF6 in EC + DEC + DMC (33:33:34) for -20 degC performance, and Xiang et al. adjust the EC/PC ratio to control SEI formation. No mitigation is claimed here beyond what these papers report.'
      source: smart1999
      where: Introduction
uses:
  - application: batteries
    device: Lithium-ion cell electrolyte
    example: A Sony Energy Devices product safety data sheet for the US18650VT lithium-ion cell (23 March 2007) lists the electrolyte only as organic solvent plus lithium salt, with a graphite anode and lithium manganese oxide and lithium nickel oxide cathode. It does not name ethylene carbonate or give a percentage.
    source: sony-us18650vt
  - application: batteries
    device: Mars Exploration Program low-temperature electrolyte work at JPL
    example: JPL identified 1.0 M LiPF6 in EC + DEC + DMC (33:33:34) as an electrolyte with excellent performance at -20 degC and studied ester co-solvents to reach -40 degC for future Mars rovers (laboratory cells).
    source: smart1999
supply:
  - subject: Ethylene carbonate (US reporting, aggregated)
    abundance: 'EPA Chemical Data Reporting aggregated production volume: 25,000,000 to under 40,000,000 lb in 2022 and 2023; 10,000,000 to under 25,000,000 lb in 2020 and 2021 (US only).'
    producers: []
    critical_lists: []
    recycling: Not sourced.
    substitutes: []
    source: pubchem-ec
    where: Manufacturing/Use Information, EPA CDR aggregated production volume
documents:
  - title: 'PubChem compound record: Ethylene carbonate (CID 7303)'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/7303
    year: 2025
  - title: Properties of a New Electrolyte Solution for Li-ion Batteries (Li et al., Acta Scientiarum Naturalium Universitatis Sunyatseni 44 Suppl. 2, 2005)
    type: paper
    url: https://xuebaozr.sysu.edu.cn/rc-pub/front/front-article/download/43625215/lowqualitypdf/一种新型锂离子二次电池用有机电解液的性能研究(英文).pdf
    year: 2005
  - title: The Role of Cesium Cation in Controlling Interphasial Chemistry on Graphite Anode in Propylene Carbonate-Rich Electrolytes (ACS Appl. Mater. Interfaces 7, 20687)
    type: paper
    url: https://www.pnnl.gov/sites/default/files/media/file/at/publications//456_252018112618.pdf
    year: 2015
  - title: First-Principles Insights on the Formation Mechanism of Innermost Layers of Solid Electrolyte Interphases (Nanomaterials 12, 3654; CC BY 4.0)
    type: paper
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC9607018/
    year: 2022
  - title: Ab initio Molecular Dynamics Simulations of the Initial Stages of SEI Formation on Lithium Ion Battery Graphitic Anodes (arXiv 1009.4154)
    type: paper
    url: https://ar5iv.labs.arxiv.org/html/1009.4154
    year: 2010
  - title: The Role of Electrolyte Upon the SEI Formation Characteristics and Low Temperature Performance of Lithium-Ion Cells with Graphite Anodes (JPL, NASA NTRS 20000070847)
    type: report
    url: https://ntrs.nasa.gov/api/citations/20000070847/downloads/20000070847.pdf
    year: 1999
  - title: Sony Energy Devices product safety data sheet, US18650VT (23 March 2007)
    type: sds
    url: https://support.blackanddecker.com/hc/en-us/article_attachments/360012464837
    year: 2007
  - title: "NIST Atomic Weights and Isotopic Compositions for All Elements"
    type: database
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl
    year: 2026
gaps:
  - The Sony safety data sheet that lists ethylene carbonate at 4% was not found. The only Sony sheet opened (US18650VT, 2007, scanned image) names the electrolyte as organic solvent and lithium salt with no percentages and no CAS numbers. The 4% figure is not in this record.
  - No supplier safety data sheet or ECHA registration dossier could be opened (the Sigma-Aldrich, Fisher and Merck pages timed out or reset). Hazards rest on the PubChem aggregation of ECHA notifications and the HSDB entries it quotes. No hazard text from a current SDS is entered.
  - Viscosity and dielectric constant come from one 2005 compilation table whose heading (25 degC) conflicts with its footnote (40 degC), and which cites earlier references without a DOI. A second source for both values at a stated temperature was not found.
  - No measured viscosity or conductivity of EC-based mixtures (for example 1 M LiPF6 in EC:EMC) at -20 degC or -40 degC was read; the low-temperature section is qualitative and limited to the melting point and what Xiang et al. and JPL state.
  - Freezing point of EC/linear carbonate mixtures (a phase diagram) was not found.
  - Flash point of typical electrolyte mixtures and thermal runaway behaviour of EC-containing electrolytes were not read; only the flash point of neat EC is entered.
  - The SEI mechanism is entered from simulation and literature statements (Leung and Budzien 2010; Peng 2022). No experimental study of the SEI products from EC was read in full, and Peng notes that the LEDC share is questioned.
  - No space-environment data for EC (vacuum outgassing, radiation) was looked for. No flight use was found.
  - Ecotoxicity, transport classification and occupational exposure limits were not read.
sources:
  pubchem-ec:
    title: 'PubChem compound summary: Ethylene carbonate (CID 7303), with HSDB and ECHA C&L sections'
    id: PubChem CID 7303; CAS 96-49-1
    url: https://pubchem.ncbi.nlm.nih.gov/compound/7303
    year: 2025
    kind: database
    license: public domain (US National Library of Medicine); third-party handbook values quoted from HSDB
  li2005:
    title: Properties of a New Electrolyte Solution for Li-ion Batteries
    id: Li Wei-hong, Dai Yong-nian, Yang Bin, Yao Yao-chun, Gao Fei; Acta Scientiarum Naturalium Universitatis Sunyatseni 44 (Suppl. 2), Nov 2005, pp. 19-21
    url: https://xuebaozr.sysu.edu.cn/rc-pub/front/front-article/download/43625215/lowqualitypdf/一种新型锂离子二次电池用有机电解液的性能研究(英文).pdf
    year: 2005
    kind: paper
    license: publisher copyright, linked not reproduced
  xiang2015:
    title: The Role of Cesium Cation in Controlling Interphasial Chemistry on Graphite Anode in Propylene Carbonate-Rich Electrolytes
    id: doi:10.1021/acsami.5b05552; ACS Appl. Mater. Interfaces 2015, 7, 20687-20695
    url: https://www.pnnl.gov/sites/default/files/media/file/at/publications//456_252018112618.pdf
    year: 2015
    kind: paper
    license: publisher copyright, linked not reproduced
  peng2022:
    title: First-Principles Insights on the Formation Mechanism of Innermost Layers of Solid Electrolyte Interphases on Carbon Anodes for Lithium-Ion Batteries
    id: doi:10.3390/nano12203654; Nanomaterials 12(20):3654
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC9607018/
    year: 2022
    kind: paper
    license: CC BY 4.0
  leung2010:
    title: Ab initio Molecular Dynamics Simulations of the Initial Stages of Solid-electrolyte Interphase Formation on Lithium Ion Battery Graphitic Anodes
    id: arXiv:1009.4154 (Kevin Leung, Joanne L. Budzien)
    url: https://ar5iv.labs.arxiv.org/html/1009.4154
    year: 2010
    kind: paper
    license: arXiv preprint
  smart1999:
    title: The Role of Electrolyte Upon the SEI Formation Characteristics and Low Temperature Performance of Lithium-Ion Cells with Graphite Anodes
    id: NASA NTRS 20000070847 (M. C. Smart, B. V. Ratnakumar, S. Greenbaum, S. Surampudi, JPL)
    url: https://ntrs.nasa.gov/api/citations/20000070847/downloads/20000070847.pdf
    year: 1999
    kind: report
    license: public domain (NASA)
  sony-us18650vt:
    title: Product Safety Data Sheet, Lithium-Ion Rechargeable Battery US18650VT (Sony Energy Devices Corp., Koriyama Plant)
    id: Dated 23 March 2007; two-page scanned PDF
    url: https://support.blackanddecker.com/hc/en-us/article_attachments/360012464837
    year: 2007
    kind: datasheet
    license: manufacturer document, linked not reproduced
  wikipedia-ec:
    title: "Wikipedia: Ethylene carbonate (chemical box, formula C3H4O3, and Production and reactions)"
    url: https://en.wikipedia.org/wiki/Ethylene_carbonate
    kind: web
    license: CC BY-SA 4.0
  nist-atomic-weights:
    title: "NIST Atomic Weights and Isotopic Compositions for All Elements (standard atomic weight table)"
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl
    year: 2026
    kind: database
    license: public domain (US government work)
license: CC-BY-4.0
updated: '2026-10-17'
review:
  status: draft
  method: assistant
  checked_values: 13
  unreachable: 4
  caveats: 6
  note: Written by an AI assistant on 2026-10-17. The PubChem values were read through a page-summary tool, not re-read in the raw record. The Li et al. table was read directly from a page image, and the Xiang et al. and Smart et al. statements from extracted PDF text. The Sony sheet was read from page images. Sigma-Aldrich, Fisher, Merck and RSC pages could not be opened, so no supplier SDS was used. The 4% ethylene carbonate figure in a Sony sheet was not found. No values were taken from memory.
story:
  recipe:
    line: "Ethylene carbonate is made by reacting ethylene oxide with carbon dioxide, catalysed by a range of cations and complexes: (CH2)2O + CO2 gives (CH2O)2CO (Wikipedia, Production and reactions)."
    parts:
      - {name: Carbon, symbol: C, atoms: 3, atomic_weight: 12.011, role: "Three carbons: two in the ethylene (CH2) backbone and one in the carbonate group. NIST gives a range for natural abundance"}
      - {name: Hydrogen, symbol: H, atoms: 4, atomic_weight: 1.008, role: "Four hydrogens on the two CH2 groups. NIST gives a range for natural abundance"}
      - {name: Oxygen, symbol: O, atoms: 3, atomic_weight: 15.999, role: "Three oxygens: two in the ring ether links and one as the carbonyl oxygen. NIST gives a range for natural abundance"}
  risk_groups:
    - title: For people
      level: 2
      verdict: Harmful if swallowed; eye irritant
      lead: Notifiers to ECHA mostly classify ethylene carbonate as an eye irritant and harmful if swallowed, and many also flag organ damage after repeated exposure, but about 5.7% of reports say it meets no hazard criteria.
      points:
        - label: Classification
          line: PubChem aggregates 543 reports from 21 ECHA notifications. The signal word is Warning, with H302 harmful if swallowed (56.4%), H315 skin irritation (13.1%), H319 serious eye irritation (74.2%) and H373 organ damage after prolonged or repeated exposure (56.2%).
        - label: Fire
          line: It is combustible when exposed to heat or flame and can react with oxidizing materials. Neat EC has an open-cup flash point of 143 °C and emits acrid smoke and irritating fumes when heated to decomposition.
        - label: Toxicity figure
          line: A handbook gives an oral rat LD50 of 10 g/kg, which sounds mild, yet most notifiers still classify it as harmful if swallowed.
    - title: If it fails
      lead: These findings come from laboratory cells and calculations, not from failures of finished spacecraft batteries.
      points:
        - label: In the cold
          line: EC melts at 36.4 °C, and the PNNL paper says this imposes a narrow service temperature range on most lithium-ion cells. The JPL mixture of EC with DEC and DMC performed excellently at -20 °C, and JPL wanted to reach -40 °C.
        - label: Without EC
          line: With propylene carbonate in place of EC, graphite is attacked by co-intercalation and eventual exfoliation, and PC is restricted to below 10% of the electrolyte.
        - label: Gas on first charge
          line: C2H4 and CO gases have been detected when EC decomposes on graphite in experiments.
    - title: Handling and storage
      points:
        - label: Storage
          line: A handbook quoted by PubChem calls it stable under normal storage conditions, with no colour deepening after 2 months at 40 °C. Alkalies and strong acids hydrolyse it, rapidly above 125 °C.
        - label: Eyes and swallowing
          line: First aid guidance in the PubChem record is to flush the eyes immediately with water and not to use emetics.
        - label: Solid at room temperature
          line: Because it melts at 36.4 °C it is a solid at normal room temperature and is supplied as a crystalline solid or liquid depending on the temperature.
  why: Ethylene carbonate (EC) is a small ring-shaped molecule, a cyclic carbonate with the formula C3H4O3. A lithium-ion electrolyte has to do two jobs at once. It must dissolve lithium salt and keep the ions apart, which needs a solvent with a high dielectric constant (a measure of how well it screens electric charge). EC's value is 89.78 at 40 °C, far above the linear carbonates such as DMC at 3.1. And on the graphite anode it must build a thin protective film, the solid electrolyte interphase (SEI). The PNNL paper calls EC the indispensable ingredient for that film. On first charge EC is reduced at the graphite surface and, according to a simulation paper, forms a self-limiting layer 30 to 50 nm thick containing Li2CO3 and lithium ethylene dicarbonate. Without it, propylene carbonate lets solvent slip between the graphite layers and tears them apart. The price is that EC melts at 36.4 °C, so it is almost always blended with low-viscosity, low-melting solvents.
  uses:
    - where: Lithium-ion cell electrolyte
      line: EC is a standard solvent in lithium-ion electrolytes. The Sony Energy Devices sheet opened here lists only organic solvent and lithium salt, so that sheet does not name EC or give a percentage.
    - where: Cold-weather electrolyte research
      line: JPL studied EC + DEC + DMC (33:33:34) with 1.0 M LiPF6, which performed excellently at -20 °C, and then added ester co-solvents aiming at -40 °C for future Mars rovers. These were laboratory cells.
  can_do:
    - label: Dissolves salt
      value: Dielectric constant 89.78
      line: A 2005 solvent table gives EC a dielectric constant of 89.78 at 40 °C, against 65 for PC and 3.1 for DMC. High values let the solvent separate lithium ions from their partner ions.
    - label: Moves ions
      value: 1.93 mPa s
      line: The same table gives its viscosity as 1.93 mPa s at 40 °C. That is comparable to PC at 2.5 and higher than DMC at 0.5889, which is why EC is mixed with thinner carbonates.
    - label: Forms the protective film
      value: SEI 30 to 50 nm
      line: On graphite EC decomposes into a self-limiting, passivating SEI layer 30 to 50 nm thick, according to the introduction of an ab initio simulation paper citing earlier experiments.
    - label: Stable to high voltage
      value: 5.8 V vs Li
      line: The 2005 table lists an oxidation potential of 5.8 V against lithium on a glassy carbon surface at 20 °C, the same as PC and a little above DMC at 5.7 V.
  compare: 'In the 2005 table, EC has the highest dielectric constant of the five carbonates (89.78 against 65 for PC, 3.1 for DMC, 2.9 for EMC and 2.8 for DEC), but its melting point of 37 °C in that table is far above PC at -49 °C, DMC at 3 °C, EMC at -55 °C and DEC at -43 °C. The PNNL paper gives PC a melting point of -48.8 °C and makes the key distinction: PC cannot form a protective SEI on graphite and is limited to below 10% of the electrolyte, while EC can. No source in this record compares EC with ionic liquids, solid electrolytes or fluorinated carbonates.'
  handling:
    - Combustible; keep away from heat, flame and oxidizers.
    - Harmful if swallowed and a serious eye irritant per most ECHA notifiers.
    - Flush eyes with water straight away if contaminated.
    - Keep clear of alkalies and strong acids, which hydrolyse it.
  good_for:
    - Dissolving lithium salt. Dielectric constant 89.78 at 40 °C, against 3.1 for DMC.
    - Making the SEI on graphite. The PNNL paper calls it indispensable for the protective interphase.
    - Wide voltage window. Oxidation potential 5.8 V vs Li on glassy carbon at 20 °C.
  watch_out:
    - Melting point. 36.4 °C, so it is solid at room temperature and limits the service temperature range of cells.
    - Gas on first charge. C2H4 and CO have been detected when EC decomposes on graphite.
    - Hazard classification. H302, H319 and H373 are reported by a majority of notifiers.
    - Thin evidence in space. No sourced space-environment data (vacuum, radiation) was found for EC in this record.
  verdict: Ethylene carbonate is the high-permittivity, SEI-forming workhorse of lithium-ion electrolytes, and its 36.4 °C melting point is the price, paid by blending it with linear carbonates. This record rests on one handbook compilation (via PubChem), one 2005 solvent table and several papers. It holds no supplier safety data sheet, no mixed-electrolyte cold data and no space data.
  compare_rows:
    - label: Density
      benchmark: density
      scope: material
    - label: Melting point
      benchmark: melting_point
      scope: material
    - label: Boiling point
      benchmark: boiling_point
      scope: material