xLi₂MnO₃·(1−x)LiMO₂ (LLO)/spinel nanocomposites are of substantial interest as cathodes with high capacity and enhanced conductivity. However, their electrochemical properties are significantly influenced by the complex phase constitutions, and undesired by-products such as rock salt phase could not be efficiently avoided. By ex-/in-situ XRD, we revealed the three phase transitions during the decomposition reaction of spinel phase, namely, Li-rich spinel (S_L) to LLO (L), normal spinel (S_N) to rock salt (R) and rock salt to LLO. Density functional theory calculations suggest that Li migrates from the 8a tetrahedral site to the interstitial 16c octahedral site as oxygen is released from S_L and S_N, forming quasi-Li₂MnO₃ and quasi-rock salt crystals, respectively. The dynamic priority of each reaction determined by experiments and calculations was utilized to design the LLO/spinel composites, and a composite with more spinel phase (7.6%) demonstrated high capacity retention at high rates. Our study sheds light on the mechanism of phase transitions among the spinel-layered-rock salt system and reveal the thermodynamic and dynamic priority of each reaction, facilitating the rational design of LLO/spinel composites.

作为具有高容量和增强的电导率的阴极，x Li ₂ MnO ₃ ·（1- x）LiMO ₂（LLO）/尖晶石纳米复合材料引起了广泛的关注。然而，它们的电化学性质受到复杂相组成的显着影响，并且不能有效地避免不希望的副产物如岩盐相。通过异位/原位X射线衍射，我们发现了尖晶石相分解反应过程中的三个相变，即富锂尖晶石（S _L）到LLO（L），普通尖晶石（S _N）。）制成岩盐（R），然后制成岩盐至LLO。密度泛函理论计算表明，随着氧气从S _L和S _N释放出来，Li从8a四面体位置迁移到间隙16c八面体位置，分别形成准Li ₂ MnO ₃和准岩石盐晶体。通过实验和计算确定的每个反应的动态优先级被用于设计LLO /尖晶石复合材料，具有更多尖晶石相（7.6％）的复合材料在高速率下显示出高容量保留率。我们的研究揭示了尖晶石-层状岩盐体系之间的相变机理，揭示了每个反应的热力学和动力学优先级，从而促进了LLO /尖晶石复合材料的合理设计。