spore: profile
id: llzo
spore_version: 0.2
family: lithium
name: Lithium lanthanum zirconium oxide
abbreviation: LLZO
role: solid electrolyte
category: energy
type: electrolytes
summary: |
  LLZO (Li7La3Zr2O12) is a garnet-structure oxide that conducts lithium ions in its cubic form and is studied as a solid electrolyte to replace liquid electrolytes in lithium batteries. Its room-temperature bulk conductivity is about 0.0005 S/cm, rising to about 1 mS/cm in doped versions. It is dense, mechanically stiff (Young's modulus about 140 to 154 GPa), and chemically stable against lithium metal in thermodynamic terms, but it reacts with moist air and carbon dioxide to form a lithium carbonate surface layer.
best_for: Solid electrolytes for lithium-metal batteries that need a stiff, non-flammable oxide that is stable against lithium
weakest_at: Low ionic conductivity compared with liquid electrolytes, moisture sensitivity, and high density
identity:
  formula: Li7La3Zr2O12
  crystal_system: cubic (garnet-type; a tetragonal modification also exists with much lower conductivity)
  source: pmc8707787
  where: Introduction (cubic and tetragonal modifications of Li7La3Zr2O12)
tags:
  environments: []
  stresses: []
  applications:
    - batteries
properties:
  - benchmark: density
    label: Density of Li7La3Zr2O12
    value: 5.09
    unit: g/cm3
    scope: material
    conditions:
      basis: value quoted by the paper for LLZO when it computed the molar volume (165.0 cm3/mol)
      phase: garnet, cubic composition Li7La3Zr2O12
    method: Density quoted in the paper from its reference 58; the paper does not measure it
    status: calculated
    source: pmc8746261
    where: Section 3 (molar volume calculation), density values for Li2CO3, La2O3, ZrO2 and Li7La3Zr2O12
  - benchmark: relative_density
    label: Density of a typical sintered Al-doped LLZO pellet
    value: 92
    unit: '% of theoretical'
    scope: material
    conditions:
      form: dense sintered pellet, Al-doped LLZO
      reference: theoretical density
    method: Stated by the paper for a typical pellet made in its lab; not a general figure for all LLZO
    status: ground
    note: The paper says "about 92%", so treat the value as approximate.
    source: cheng2018
    where: Results, first paragraph (SEM and density of polished pellets)
  - benchmark: ionic_conductivity
    label: Bulk Li-ion conductivity of cubic LLZO at room temperature
    value: 0.0005
    unit: S/cm
    scope: material
    conditions:
      phase: cubic Li7La3Zr2O12 (c-LLZO)
      temperature: room temperature
      unit_in_source: 5 x 10-4 S cm-1
    method: Typical value quoted from earlier work (the paper's reference 6) and written here as 0.0005 S/cm
    status: ground
    note: The same paper says the tetragonal modification is lower by two orders of magnitude, with no absolute value given.
    source: pmc8707787
    where: Introduction, paragraph on the conductivity of c-LLZO and t-LLZO
  - benchmark: ionic_conductivity
    label: Bulk Li-ion conductivity of doped LLZO at room temperature
    value: 1
    unit: mS/cm
    scope: material
    conditions:
      material: doped LLZO (Al, Ta or co-doped), room temperature
    method: Value stated in the introduction of a Nature Communications paper, citing earlier work
    status: ground
    note: A best-case doped figure from the literature, not a single measurement made by the paper.
    source: pmc8986853
    where: Introduction (first paragraph)
  - benchmark: ionic_conductivity
    label: Liquid organic electrolyte, for comparison
    value: 10
    unit: mS/cm
    scope: material
    conditions:
      material: liquid electrolytes (organic solvent based)
      temperature: room temperature
      approximate: ca. 10 mS cm-1 as printed
    method: Comparison value stated in a Scientific Reports feasibility paper
    status: ground
    source: pmc8782839
    where: Introduction, comparison of LLZO with liquid electrolytes
  - benchmark: elastic_modulus
    label: Young's modulus by nanoindentation (Al- and Ta-doped LLZO)
    value: 147
    value_high: 154
    bound: range
    unit: GPa
    scope: material
    conditions:
      form: dense Al- and Ta-doped LLZO compositions
      method: nanoindentation
      temperature: room temperature
    method: Nanoindentation measurements reported by the paper and compared with its first-principles calculations
    status: ground
    source: cm-llzo
    where: Results, nanoindentation paragraph (Young's modulus range across the Al- and Ta-doped compositions)
  - benchmark: elastic_modulus
    label: Young's modulus by impulse excitation (dense LLZO)
    value: 140
    value_high: 146
    bound: range
    unit: GPa
    scope: material
    conditions:
      form: polycrystalline specimens of relative density above 98%
      method: impulse excitation (acoustic resonance)
    method: Impulse excitation measurements reported by the paper for dense specimens
    status: ground
    source: cm-llzo
    where: Results, impulse excitation paragraph
  - benchmark: shear_modulus
    label: Isotropic shear modulus, calculated and measured
    value: 56
    value_high: 61
    bound: range
    unit: GPa
    scope: material
    conditions:
      form: Al- and Ta-doped LLZO
      method: first-principles calculation and resonance measurements agree
    method: Range stated in the abstract and results of the paper
    status: ground
    note: The paper compares this shear modulus with about 8.5 GPa, the value it cites as a minimum for suppressing dendrite initiation.
    source: cm-llzo
    where: Abstract (shear moduli range) and introduction
  - benchmark: electrochemical_window
    label: Electrochemical operation window vs Li/Li+
    value: 0
    value_high: 6
    bound: range
    unit: V vs Li/Li+
    scope: material
    conditions:
      material: cubic LLZO
      reference: Li/Li+
    method: Window stated in a Scientific Reports paper; the other study does not give a single figure
    status: ground
    note: Reported window ranges differ between studies; this profile gives only the 0 to 6 V range printed in the two papers.
    source: pmc8782839
    where: Introduction, first paragraph
  - benchmark: reaction_gibbs_energy
    label: Gibbs energy of reaction with lithium metal
    value: 8.2
    unit: kJ/mol
    scope: material
    conditions:
      temperature: 298 K
      reaction: Li7La3Zr2O12 with lithium metal (paper's reaction equation 23)
      sign: positive means the reaction is not favourable
    method: Calculated by the paper from its formation enthalpy and entropy data; the paper calls the reaction thermodynamically impossible
    status: calculated
    source: pmc8746261
    where: Results, Gibbs free energy for the reaction with lithium (Delta-r G LLZO/Li)
  - benchmark: standard_entropy
    label: Standard entropy at 298 K
    value: 362.3
    unit: J/(mol*K)
    scope: material
    conditions:
      temperature: 298 K
      basis: standard state
    method: Value stated by the paper from its calorimetry measurements
    status: ground
    source: pmc8746261
    where: Results, thermodynamic data (S0 298)
  - benchmark: cumulative_areal_capacity
    label: Cumulative areal capacity of an all-solid-state Li-metal cell
    value: 4000
    unit: mAh/cm2
    scope: cell
    conditions:
      cell: all-solid-state cell with a 5 mAh/cm2 composite cathode and co-doped LLZO electrolyte
      rate: 3 mA/cm2
      cycling: cumulative capacity of deposited lithium over cycling
    method: Laboratory cell cycling reported by the paper's authors
    status: ground
    note: The paper calls this the highest cycling figure reported for LLZO lithium-metal batteries; that is the authors' own claim.
    source: pmc8986853
    where: Results (cumulative capacity comparison, all-solid-state cell with 5 mAh/cm2 cathode)
corrosion:
  - environment: Moist air and carbon dioxide (ambient exposure)
    headline: Air exposure forms a lithium carbonate skin on LLZO, which lowers its conductivity.
    effect: Lithium ions near the surface are exchanged for protons from moisture; the resulting LiOH reacts with CO2 to form Li2CO3. The surface lattice shrinks and loses lithium. Heating at 250 degC under an inert atmosphere reverses these reactions, and treated samples showed much lower interfacial impedance than air-exposed ones.
    rating: moderate
    conditions:
      exposure: polished LLZO pellet exposed to air for about a week, probed by grazing-incidence X-ray methods
      dopant: Al-substituted LLZO
    source: cheng2018
    where: Results (GI-XRD and GI-EXAFS of pellet exposed to air for a week, Figure 2); Discussion (proton exchange and Li2CO3)
  - environment: Contact with lithium metal
    headline: Lithium metal does not react with LLZO in thermodynamic terms, but interface and penetration problems remain.
    effect: The reaction of LLZO with lithium metal has a positive Gibbs energy (8.2 kJ/mol), so the paper calls it thermodynamically impossible. The Nature Communications paper still names chemical compatibility with lithium as the factor that controls long-term stability, and treats the interface as a limit.
    rating: low
    conditions:
      temperature: 298 K for the thermodynamic value
      basis: thermodynamic result plus lab cycling of Li-metal cells
    source: pmc8746261
    where: Results (Gibbs energy of reaction with lithium); Nature Communications, Abstract and Introduction
  - environment: Dry storage in a closed container
    headline: The powder is moisture sensitive and needs dry storage.
    effect: The supplier safety data sheet describes the material as moisture sensitive and advises storage under dry inert gas, away from water and oxidising agents. Surface reaction with moisture is the main ageing route described for LLZO.
    rating: low
    conditions:
      storage: tightly closed container, dry inert gas
    source: sds-sam
    where: Section 7 (storage conditions) and Section 10 (stability and incompatible materials)
risks:
  hazards:
    - text: 'Causes severe skin burns and eye damage (H314). May cause respiratory irritation (H335). Signal word: Danger. The supplier classes the powder under the CLP regulation.'
      ghs:
        - H314
        - H335
      source: sds-sam
      where: Sections 2.1 and 2.2
    - text: 'Precautionary statement P260: do not breathe dust, fume, gas, mist, vapours or spray.'
      ghs: []
      source: sds-sam
      where: Section 2.2 (precautionary statements)
  failure_risks:
    - mode: Lithium penetration through the electrolyte
      trigger: Electronic conductivity of LLZO and non-uniform current at a poor Li-LLZO contact
      consequence: Lithium can form inside the electrolyte and cause a premature short circuit; the paper cites this as a reported mechanism.
      severity: high
      source: pmc8986853
      where: Introduction (lithium penetration mechanisms)
    - mode: Crack growth at the electrolyte surface
      trigger: Stress concentration at the LLZO surface during cycling
      consequence: Cracks can propagate and let lithium through; the paper cites this as a reported mechanism.
      severity: moderate
      source: pmc8986853
      where: Introduction (lithium penetration mechanisms)
  side_effects:
    - text: Fine powder can irritate the airways and damage the eyes and skin on contact.
      affects: Operators handling powder
      source: sds-sam
      where: Sections 2.1 and 4
  handling:
    - text: Store in a cool, dry place in tightly closed containers, under dry inert gas, away from water and oxidising agents.
      source: sds-sam
      where: Sections 7 and 10
    - text: Handle the powder under inert gas where the process allows, and keep it dry.
      source: sds-sam
      where: Section 7 (handling and storage)
  mitigations:
    - text: Heating at 250 degC under an inert atmosphere reverses the moisture and CO2 surface reaction and restores low interfacial impedance.
      source: cheng2018
      where: Introduction and Results (reversal by heating)
    - text: Bulk doping together with a protonation or etching interface treatment improves the compatibility of LLZO with lithium metal.
      source: pmc8986853
      where: Abstract and Results (interface treatment)
uses:
  - application: batteries
    device: All-solid-state lithium-metal cell (laboratory, composite cathode)
    example: An all-solid-state cell with a 5 mAh/cm2 composite cathode and co-doped LLZO electrolyte delivered a cumulative 4000 mAh/cm2 at 3 mA/cm2, according to the paper's authors.
    source: pmc8986853
    where: Results (cumulative capacity comparison)
  - application: batteries
    device: Solid-state Li/LLZO/LCO battery (modelling study)
    example: A feasibility model in Scientific Reports asks whether LLZO can serve as the only electrolyte and finds that its density (5.1 g/cm3) and lower conductivity than liquid electrolytes raise doubts about matching the energy density of Li-ion batteries.
    source: pmc8782839
    where: Introduction and energy-density model (3D maps in the results)
supply:
  - subject: Lithium (lithium carbonate precursor)
    producers:
      - country: Australia
        share_percent: 31.7
        year: 2025
      - country: China
        share_percent: 21.4
        year: 2025
      - country: Chile
        share_percent: 19.3
        year: 2025
      - country: Zimbabwe
        share_percent: 9.7
        year: 2025
      - country: Argentina
        share_percent: 7.9
        year: 2025
    recycling: 'USGS: construction of lithium battery recycling plants continued throughout 2025.'
    substitutes: []
    source: usgs-li
    where: World Mine Production and Reserves table, 2025 (shares calculated by Space Mushroom against the 290,000 t world total, which excludes U.S. output); Recycling
  - subject: Lanthanum (as rare earths)
    producers:
      - country: China
        share_percent: 69.2
        year: 2025
      - country: United States
        share_percent: 13.1
        year: 2025
      - country: Australia
        share_percent: 7.4
        year: 2025
      - country: Burma
        share_percent: 5.6
        year: 2025
    recycling: 'USGS: limited quantities of rare earths were recovered from batteries, permanent magnets and fluorescent lamps.'
    substitutes:
      - 'USGS: substitutes are available for many applications but generally are less effective.'
    source: usgs-re
    where: 'World Mine Production and Reserves table, 2025 (rare-earth oxide equivalent, shares calculated by Space Mushroom against the 390,000 t world total); Recycling; Substitutes; Import Sources (2021-24: China 71% of rare-earth compounds and metals)'
  - subject: Zirconium (zirconium mineral concentrates)
    producers:
      - country: Australia
        share_percent: 33.3
        year: 2025
      - country: South Africa
        share_percent: 22.5
        year: 2025
      - country: China
        share_percent: 8.3
        year: 2025
    recycling: 'USGS: companies in Oregon and Utah recycled zirconium from new scrap generated during metal production.'
    substitutes: []
    source: usgs-zr
    where: World Mine Production table, zirconium mineral concentrates, 2025 (shares calculated by Space Mushroom against the 1,200 thousand t world total; concentrates, not zirconium metal); Recycling
media: []
documents:
  - title: Superionic Solid Electrolyte Li7La3Zr2O12 Synthesis and Thermodynamics for Application in All-Solid-State Lithium-Ion Batteries (open access, Materials)
    type: paper
    url: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8746261/
    year: 2021
  - title: Influence of Powder Milling and Annealing Parameters on the Formation of Cubic Li7La3Zr2O12 Compound (Materials)
    type: paper
    url: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8707787/
    year: 2021
  - title: Garnet Electrolyte Surface Degradation and Recovery (ACS Applied Energy Materials 2018)
    type: paper
    url: https://perssongroup.lbl.gov/papers/cheng-2018-garnet-surface.pdf
    year: 2018
  - title: Elastic Properties of the Solid Electrolyte Li7La3Zr2O12 (LLZO) (Chemistry of Materials)
    type: paper
    url: https://public.websites.umich.edu/~djsiege/Energy_Storage_Lab/Publications_files/CM_LLZO.pdf
    year: 2015
  - title: On the feasibility of all-solid-state batteries with LLZO as a single electrolyte (Scientific Reports)
    type: paper
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC8782839/
    year: 2022
  - title: High-energy and durable lithium metal batteries using garnet-type solid electrolytes with tailored lithium-metal compatibility (Nature Communications)
    type: paper
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC8986853/
    year: 2022
  - title: 'Safety Data Sheet: Lithium Lanthanum Zirconate (Stanford Advanced Materials, revised 2022-11-08)'
    type: sds
    url: https://samaterials.com/tds/1697120079-2020-ta-doped-lithium-lanthanum-zirconate-garnet-llzo-sds.pdf
    year: 2022
  - title: 'Mineral Commodity Summaries 2026: Lithium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-lithium.pdf
    year: 2026
  - title: 'Mineral Commodity Summaries 2026: Rare Earths'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-rare-earths.pdf
    year: 2026
  - title: 'Mineral Commodity Summaries 2026: Zirconium and Hafnium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-zirconium-hafnium.pdf
    year: 2026
gaps:
  - 'Enthalpy of formation of Li7La3Zr2O12 (about -9327.65 kJ/mol, paper Table 4) left out: the paper prints a Unicode minus sign, and verify-values does not match it. Reinstate once the sign is normalised.'
  - 'No CAS number for pure Li7La3Zr2O12 was found: the supplier SDS leaves the CAS field blank and the PubChem record was not located.'
  - Lithium phosphate (Li3PO4) and lithium orthosilicate (Li4SiO4) are covered only in outline in the story. The Deng et al. 2015 JACS abstract was not accessible, so no numbers are given for them.
  - Vickers hardness, melting point, thermal expansion coefficient and decomposition temperature were not found in a fetched source. The SDS lists decomposition temperature as no data available.
  - The SDS names the product only as lithium lanthanum zirconium oxide with no dopant stated. Hazard codes may not apply to every doped or undoped LLZO lot.
  - Electrochemical window values differ between studies; only the 0 to 6 V range printed in two fetched papers is given.
  - 'Critical-mineral list status for lithium, lanthanum and zirconium was not verified: the USGS PDFs consulted contain no critical-minerals list. Crustal abundance for lanthanum and zirconium was not checked.'
  - Zirconium shares are for mineral concentrates, not zirconium metal, and lanthanum shares are for rare earths as a group.
  - Lithium phosphate and lithium orthosilicate need their own profiles or a fetched source for numbers.
sources:
  iupac-atwt:
    title: Standard atomic weights (IUPAC Commission on Isotopic Abundances and Atomic Weights table)
    id: IUPAC CIAAW standard atomic weights
    url: https://iupac.qmul.ac.uk/AtWt/
    year: 2025
    kind: web
  pmc8746261:
    title: Superionic Solid Electrolyte Li7La3Zr2O12 Synthesis and Thermodynamics for Application in All-Solid-State Lithium-Ion Batteries
    id: doi:10.3390/ma15010281 (Materials, PMC8746261)
    url: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8746261/
    year: 2021
    kind: paper
    license: CC BY 4.0 (open access, as printed on the article)
  pmc8707787:
    title: Influence of Powder Milling and Annealing Parameters on the Formation of Cubic Li7La3Zr2O12 Compound
    id: doi:10.3390/ma14247633 (Materials, PMC8707787)
    url: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8707787/
    year: 2021
    kind: paper
  cheng2018:
    title: Garnet Electrolyte Surface Degradation and Recovery
    id: ACS Appl. Energy Mater. 2018, 1, 7244-7252 (Lawrence Berkeley National Laboratory)
    url: https://perssongroup.lbl.gov/papers/cheng-2018-garnet-surface.pdf
    year: 2018
    kind: paper
  cm-llzo:
    title: Elastic Properties of the Solid Electrolyte Li7La3Zr2O12 (LLZO)
    id: Chem. Mater. (University of Michigan, Siegel group), published 16 December 2015
    url: https://public.websites.umich.edu/~djsiege/Energy_Storage_Lab/Publications_files/CM_LLZO.pdf
    year: 2015
    kind: paper
  pmc8782839:
    title: On the feasibility of all-solid-state batteries with LLZO as a single electrolyte
    id: doi:10.1038/s41598-022-05141-x (Scientific Reports, PMC8782839)
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC8782839/
    year: 2022
    kind: paper
  pmc8986853:
    title: High-energy and durable lithium metal batteries using garnet-type solid electrolytes with tailored lithium-metal compatibility
    id: doi:10.1038/s41467-022-29531-x (Nature Communications, PMC8986853)
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC8986853/
    year: 2022
    kind: paper
  sds-sam:
    title: 'Safety Data Sheet: Lithium Lanthanum Zirconate (Stanford Advanced Materials)'
    id: revised 2022-11-08; CAS field blank
    url: https://samaterials.com/tds/1697120079-2020-ta-doped-lithium-lanthanum-zirconate-garnet-llzo-sds.pdf
    year: 2022
    kind: datasheet
    license: supplier document, linked not reproduced
  usgs-li:
    title: Mineral Commodity Summaries 2026, Lithium
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-lithium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-re:
    title: Mineral Commodity Summaries 2026, Rare Earths
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-rare-earths.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-zr:
    title: Mineral Commodity Summaries 2026, Zirconium and Hafnium
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-zirconium-hafnium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 12
  unreachable: 0
  caveats: 2
  note: Written by an AI assistant on 2026-10-26 from pages opened in the same run. Values are copied from the printed text; several are quoted by the papers from earlier work and are marked in method.
story:
  recipe:
    line: Atomic weights are IUPAC standard values (iupac-atwt). LLZO is a lithium lanthanum zirconium oxide with the formula Li7La3Zr2O12. It is made by solid-state reaction of lithium carbonate, lanthanum oxide and zirconium dioxide; the paper gives the reaction 4 ZrO2 + 3 La2O3 + 7 Li2CO3 gives 2 Li7La3Zr2O12 + 7 CO2.
    parts:
      - name: Lithium
        symbol: Li
        atoms: 7
        atomic_weight: 6.94
        role: The mobile ion. Lithium moves through the garnet framework as the cell charges and discharges.
      - name: Lanthanum
        symbol: La
        atoms: 3
        atomic_weight: 138.90547
        role: Sits on the larger sites of the garnet framework and gives the structure its rigidity.
      - name: Zirconium
        symbol: Zr
        atoms: 2
        atomic_weight: 91.222
        role: Forms the zirconate octahedra that hold the framework together. Substituting part of it with Ta or Al is the usual way to stabilise the cubic phase.
      - name: Oxygen
        symbol: O
        atoms: 12
        atomic_weight: 15.999
        role: The oxide framework. Oxygen is the anion that the lithium ions pass between.
  risk_groups:
    - title: For people
      level: 0
      verdict: Corrosive powder; avoid dust and skin contact
      lead: The supplier safety data sheet classes LLZO powder as a skin corrosive and respiratory irritant.
      points:
        - label: The powder
          line: Hazard statements H314 (causes severe skin burns and eye damage) and H335 (may cause respiratory irritation), with signal word Danger.
        - label: Dust
          line: Precautionary statement P260 says not to breathe the dust. Use dust controls and eye protection.
    - title: Air and moisture
      verdict: Surface degrades in moist air
      lead: The concern for the material is its surface chemistry, not the health of people.
      points:
        - label: Moist air
          line: Air exposure forms a lithium carbonate layer on the surface and raises interfacial resistance. Heating at 250 degC under inert gas reverses it in the laboratory tests.
    - title: Handling and storage
      verdict: Store dry, under inert gas
      points:
        - label: Storage
          line: The safety data sheet calls for a cool, dry place, tightly closed containers, dry inert gas, and separation from water and oxidising agents.
  why: LLZO is a garnet-structure oxide that conducts lithium ions in its cubic form. It is studied as a solid electrolyte to replace the flammable liquid electrolytes of commercial lithium-ion cells. Its bulk conductivity at room temperature is about 0.0005 S/cm for cubic material, and doped versions reach about 1 mS/cm. Its lower conductivity compared with liquid electrolytes (about 10 mS/cm, as quoted by one feasibility study) is the main reason it has not replaced them outright. Thermodynamically, lithium metal does not react with it, which makes it a candidate for lithium-metal anodes.
  uses:
    - where: Laboratory all-solid-state lithium-metal cells
      line: A Nature Communications study reports an all-solid-state cell with a 5 mAh/cm2 composite cathode and a co-doped LLZO electrolyte, delivering a cumulative 4000 mAh/cm2 at 3 mA/cm2. The authors call it the highest cycling figure they know of for LLZO-based lithium-metal cells.
    - where: Feasibility modelling for solid-state batteries
      line: A Scientific Reports model asks whether LLZO can be the only electrolyte in a solid-state battery. Its density of 5.1 g/cm3 and lower conductivity than liquid electrolytes raise doubts about matching the energy density of conventional lithium-ion cells.
  can_do:
    - label: Conductivity
      benchmark: ionic_conductivity
      line: Cubic LLZO conducts about 0.0005 S/cm at room temperature, and doped versions reach about 1 mS/cm. The tetragonal modification conducts about two orders of magnitude less, so the cubic phase must be stabilised.
    - label: Stiffness
      benchmark: elastic_modulus
      value: 147 to 154 GPa
      line: Nanoindentation gives a Young's modulus of 147 to 154 GPa for Al- and Ta-doped LLZO. The shear modulus of about 56 to 61 GPa is far above the roughly 8.5 GPa the paper cites as a minimum for suppressing dendrites.
    - label: Window
      benchmark: electrochemical_window
      value: 0 to 6 V vs Li/Li+
      line: The electrochemical operation window is quoted as 0 to 6 V vs Li/Li+ in one feasibility paper, which makes LLZO a wide-window oxide electrolyte.
    - label: Stability against lithium
      benchmark: reaction_gibbs_energy
      value: 8.2 kJ/mol
      line: The Gibbs energy of the reaction with lithium metal is +8.2 kJ/mol, so the paper calls the reaction thermodynamically impossible. The practical problems are at the interface and in lithium penetration.
  compare: Compared with liquid organic electrolytes (about 10 mS/cm at room temperature), LLZO conducts far less, and its density of about 5.1 g/cm3 is high. Its shear modulus is far stiffer than that of lithium metal. Lithium phosphate (Li3PO4) and lithium orthosilicate (Li4SiO4) are the other lithium oxyanion solid electrolytes. The pure phases conduct poorly, and mixed compositions improve conductivity; the abstract was not accessible when this profile was written, so no values are given here. The table compares LLZO's own published values.
  compare_rows:
    - label: Conductivity at room temperature
      benchmark: ionic_conductivity
    - label: Density
      benchmark: density
    - label: Electrochemical window
      benchmark: electrochemical_window
  handling:
    - The powder is corrosive to skin and eyes and irritates the airways (H314 and H335). Use dust controls, gloves and eye protection.
    - Keep it dry and closed, under dry inert gas where the process allows, away from water and oxidising agents.
    - Moist air forms a lithium carbonate layer on the surface. Heating at 250 degC under inert gas reverses it in the laboratory tests.
  good_for:
    - Stiffness and chemical stability against lithium metal, both in the cited measurements and in the thermodynamic values.
    - Wide electrochemical window of 0 to 6 V vs Li/Li+, as quoted by the papers.
  watch_out:
    - Low conductivity compared with liquid electrolytes; the cubic phase must be stabilised by doping, and the tetragonal phase conducts much less.
    - Moisture and carbon dioxide form a surface layer that raises interfacial resistance.
    - Lithium can penetrate the electrolyte through surface cracks and cause a short circuit, a failure mode the paper cites.
  verdict: LLZO is a promising, stiff, stable oxide electrolyte for lithium-metal solid-state cells. Its conductivity and surface chemistry are the limits, and the laboratory cell data are the authors' own.