Monoclinic Li₃V₂(PO₄)₃ is a promising cathode material with complex charge–discharge behavior. Previous structural investigation of this compound mainly focuses on local environments; while the reaction kinetics and the driving force of irreversibility of this material remain unclear. To fully understand the above issues, both the equilibrium and the non-equilibrium reaction routes have been systematically investigated in this study. Multiple characterization techniques including X-ray diffraction, variable temperature (spinning rate) and ex/in situ ⁷Li, ³¹P solid state NMR have been employed to provide comprehensive insights into kinetics, dynamics, framework structure evolution and charge ordering, which is essential to better design and application of lithium transition metal phosphate cathodes. Our results suggest that the kinetics process between the non-equilibrium and the quasi-equilibrium delithiation pathways from Li₂V₂(PO₄)₃ to V₂(PO₄)₃ is related with a slow relaxation from two-site to one-site delithiation. More importantly, it has been demonstrated that the irreversibility in this system is not solely affected by cation and/or charge ordering/disordering, but mainly driven by framework structure distortion.

单斜Li ₃ V ₂ (PO ₄ ) ₃是一种具有复杂充放电行为的有前途的正极材料。此前对该化合物的结构研究主要集中在当地环境；而这种材料的反应动力学和不可逆性的驱动力仍不清楚。为了充分理解上述问题，本研究系统地研究了平衡和非平衡反应路线。多种表征技术，包括 X 射线衍射、变温（旋转速率）和外/原位 ⁷ Li, ³¹P 固态 NMR 已被用于提供对动力学、动力学、骨架结构演变和电荷排序的全面见解，这对于更好地设计和应用锂过渡金属磷酸盐正极至关重要。我们的结果表明，从 Li ₂ V ₂ (PO ₄ ) ₃到 V ₂ (PO ₄ ) ₃的非平衡和准平衡脱锂途径之间的动力学过程与从二位点到一位点脱锂的缓慢弛豫有关。更重要的是，已经证明该系统中的不可逆性不仅受阳离子和/或电荷有序/无序的影响，而且主要受框架结构扭曲的影响。