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Atomistic level aqueous dissolution dynamics of NASICON-type Li1+xAlxTi2−x(PO4)3 (LATP)

Evidence and attribution

Authority of statements

Prose sections below (Summary, Methods, Findings, etc.) are curated summaries of the publication identified by doi, title, and pdf_path in the front matter above. They are not new primary claims by this wiki.

For definitive numerical values, reaction schemes, and interpretations, use the peer-reviewed article (and optional records under normalized/papers/ when present)—not this page alone.

Summary

NASICON-type Li\(_{1+x}\)Al\(_x\)Ti\(_{2-x}\)(PO\(_4\))\(_3\) (LATP) is a fast Li-ion conductor, yet moisture during cold sintering or slurry processing can trigger incongruent dissolution that leaves porosity, impurities, or interphase layers that harm solid electrolyte cells. Sengul et al. combine ReaxFF molecular dynamics of the LATP / liquid water interface with experimental characterization of cold-sintered ceramics to follow ion release, framework degradation, and secondary-phase nucleation in sequence. Adri C. T. van Duin co-authors the reactive modeling effort alongside Randall-group processing expertise, situating the study in PCCP as a Communication-length mechanistic report.

Methods

Experiments (cold-sintered LATP + characterization)

  • Samples: Densified LATP ceramics from cold sintering at 130 °C in the presence of water (details of powders, binders, and thermal history in the article Methods).
  • Microscopy / spectroscopy: SEM/EDS on initial powder; HAADF-STEM with EDS mapping on cold-sintered ceramics to track Ti vs Al segregation and homogeneous P distribution (figure set referenced in the Communication).
  • Coupling to computation: Experimental microstructure motivates the incongruent dissolution picture compared against trajectories.

ReaxFF molecular dynamics (B)

  • Interaction model: ReaxFF for LATP–water interfaces with Li–Al–Ti–P–O chemistry consistent with NASICON-family parameterizations cited from prior training literature.
  • Setup: Slab (or equivalent) LATP surface in contact with liquid water; evolution of the interface is tracked as dissolution proceeds.
  • Analysis: Li release into solution, phosphate connectivity changes, AlO\(_x\) / PO\(_4\)-related polymerization, Ti–Ti radial distribution evolution, and segregation patterns compared to STEM-EDS (simulation snapshots in the paper).
  • Electrostatics / charge: ReaxFF charge equilibration (QEq) conventions follow the standard ReaxFF treatment in the authors’ software setup; exact cutoffs, timestep, and thermostat are specified in the article/SI—not duplicated here.

Integrated interpretation

Iterative comparison of experimental elemental redistribution with simulation morphology (e.g. Ti/Al segregation during dissolution) supports the proposed sequential mechanism.

MD application (LATP / water)

Engine / code: LAMMPS-style ReaxFF integration (as in PCCP). Slab/interface of LATP with liquid water: 3D PBC supercell size, T and P (if NPT), timestep, ps/ns stages, thermostat/barostat where used, and Coulomb / QEq settings for Li–Al–Ti–P–O with H\(_2\)O are specified in the article; this wiki defers to that text. N/A — open-circuit water exposure, no galvanostatic bias or static interfacial electric field in the MD protocol as summarized. N/A — no metadynamics or replica sampling beyond the reported MD unless the SI adds them.

Findings

Staged dissolution sequence

Dissolution is sequential and incongruent (dissolved stoichiometry ≠ bulk stoichiometry): rapid Li leaching—common for NASICON-type materials—is followed by phosphate-linked rearrangements that destabilize the framework and promote Ti-rich secondary-phase formation, rather than uniform surface recession.

Rate control and polymerization

After initial Li loss, the dissolution rate is tied to polymerization of AlO\(_6\) and PO\(_4\)-derived species (as summarized in the abstract and Fig. 1 schematic), which in turn triggers secondary phases.

Processing implications

Brief water contact during cold sintering or slurry steps can leave interfacial chemical signatures even when bulk X-ray patterns look unchanged, motivating care in solution-based processing of NASICON electrolytes.

Scope relative to devices

Open-circuit water exposure omits applied bias and pH control of real battery interfaces; mapping to operating cells requires extending the model (as the authors note directionally).

Limitations

Specific surface orientation, pH, and electrochemical bias in real devices extend beyond a single interface model; quantitative dissolution rates require careful calibration to experiment and thermodynamic databases.

Relevance to group

Direct ReaxFF + ceramic electrolyte interface work tied to PSU materials collaborations and broader battery processing themes in the corpus.

Citations and evidence anchors

https://doi.org/10.1039/D1CP05360D — Communication (~pp. 1–2) states sequential mechanism and Li/PO\(_4\) arguments.