AbstractUnderstanding the physical picture of Li ion transport in the current ionic conductors is quite essential to further develop lithium superionic conductors for solid-state batteries. The traditional practice of directly extrapolating room temperature ion diffusion properties from the high-temperature (>600 K) ab initio molecular dynamics simulations (AIMD) simulations by the Arrhenius assumption unavoidably cause some deviations. Fortunately, the ultralong-time molecular dynamics simulation based on the machine-learning interatomic potentials (MLMD) is a more suitable tool to probe into ion diffusion events at low temperatures and simultaneously keeps the accuracy at the density functional theory level. Herein, by the low-temperature MLMD simulations, the non-linear Arrhenius behavior of Li ion was found for Li₃ErCl₆, which is the main reason for the traditional AIMD simulation overestimating its ionic conductivity. The 1μs MLMD simulations capture polyanion rotation events in Li₇P₃S₁₁ at room temperature, in which four [PS₄]³⁻ tetrahedra belonging to a part of the longer-chain [P₂S₇]⁴⁻ group are noticed with remarkable rotational motions, while the isolated group [PS₄]³⁻ does not rotate. However, no polyanion rotation is observed in Li₁₀GeP₂S₁₂, β-Li₃PS₄, Li₃ErCl₆, and Li₃YBr₆ at 300 K during 1μs simulation time. Additionally, the ultralong-time MLMD simulations demonstrate that not only there is no paddle-wheel effect in the crystalline Li₇P₃S₁₁ at room temperature, but also the rotational [PS₄]³⁻ polyanion groups have weakly negative impacts on the overall Li ion diffusion. The ultralong-time MLMD simulations deepen our understanding of the relationship between the polyanion rotation and cation diffusion in ionic conductors at room environments.