摘要
Ni-rich layered oxide cathodes, such as LiNi0.8Co0.1Mn0.1O2 (NCM811), are promising for high-energy lithiumion batteries due to their high capacity. However, their structural stability under high-voltage operation remains a key challenge. In particular, the H2 <-> H3 phase transition and the resulting transformation from a layered to a rock-salt-like structure cause mechanical stress and interfacial degradation, typically limiting the cutoff voltage of NCM811 cathodes to around 4.3 V. Here, we demonstrate that replacing the conventional liquid electrolyte with a polymer-in-ceramic composite solid electrolyte effectively suppresses these degradation pathways. The solid electrolyte constrains the c-axis lattice contraction and stabilizes the cathode-electrolyte interface, enabling stable cycling up to 5.0 V and significantly extending cycle life. Operando synchrotron X-ray diffraction and high-resolution transmission electron microscopy confirm that although the cathode potential enters the H2 <-> H3 regime, the characteristic lattice contraction and interfacial reconstruction are substantially mitigated in the solid-state system. This leads to reduced volumetric strain, preserved layered structure, and the formation of a thinner, more stable interphase. These findings underscore the critical role of solid electrolytes in enhancing the structural and interfacial stability of Ni-rich cathodes, offering a promising route toward safer and longer-lasting high-voltage lithium-ion batteries.
