The nonexistence of a paddlewheel effect in superionic conductors

Jun, KyujungLee, ByungjuKam, Ronald L.Ceder, Gerbrand
Issue Date
National Academy of Sciences
Proceedings of the National Academy of Sciences of the United States of America, v.121, no.18
Since the 1980s, the paddlewheel effect has been suggested as a mechanism to boost lithium- ion diffusion in inorganic materials via the rotation of rotor- like anion groups. However, it remains unclear whether the paddlewheel effect, defined as large- angle anion group rotations assisting Li hopping, indeed exists; furthermore, the physical mechanism by which the anion- group dynamics affect lithium- ion diffusion has not yet been established. In this work, we differentiate various types of rotational motions of anion groups and develop quaternion- based algorithms to detect, quantify, and relate them to lithium- ion motion in ab initio molecular dynamics simulations. Our analysis demonstrates that, in fact, the paddlewheel effect, where an anion group makes a large angle rotation to assist a lithium- ion hop, does not exist and thus is not responsible for the fast lithium- ion diffusion in superionic conductors, as historically claimed. Instead, we find that materials with topologically isolated anion groups can enhance lithium- ion diffusivity via a more classic nondynamic soft- cradle mechanism, where the anion groups tilt to provide optimal coordination to a lithium ion throughout the hopping process to lower the migration barrier. This anion- group disorder is static in nature, rather than dynamic and can explain most of the experimental observations. Our work substantiates the nonexistence of the long- debated paddlewheel effect and clarifies any correlation that may exist between anion- group rotations and fast ionic diffusion in inorganic materials.
WHEEL MECHANISM; SOLID-ELECTROLYTE; ELECTRICAL-CONDUCTIVITY; IONIC-CONDUCTIVITY; LITHIUM; SULFATE; TEMPERATURE; DIFFUSION; NEUTRON; PHASES; superionic conductors; diffusion; ab initio molecular dynamics; correlated motion; solid electrolyte
Appears in Collections:
KIST Article > 2024
Files in This Item:
There are no files associated with this item.
RIS (EndNote)
XLS (Excel)


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.