Mechanically Adaptive Cathode–Electrolyte Interphase via Dynamic Covalent Chemistry for Long-Life Ni-Rich Lithium Batteries

High-nickel LiNi_0.83Co_0.12Mn_0.05O₂ (NCM83) cathodes suffer from interfacial instability resulting from cathode-electrolyte reactions and anisotropic mechanical strain within secondary particles. Herein, we present a mechanically adaptive cathode-electrolyte interphase (CEI) engineered via a dynamic covalent network that features a supramolecular ion-conducting polyurethane ureido-pyrimidinone (SPU-UPy) elastomer. The dynamic network integrates cooperative hydrogen bonds and disulfide bonds and imparts exceptional mechanical resilience and autonomous self-healing capabilities that allow it to accommodate volume fluctuations without compromising structural integrity. The SPU-UPy layer is also designed with strong transition metal ion-O/N coordination bonds that greatly enhance adhesion to the NCM83 surface and mitigate transition metal dissolution in the electrolyte. The polyether backbone facilitates efficient Li-ion transport across the interface and ensures a homogeneous interfacial Li concentration during intercalation/deintercalation. Consequently, the dynamic CEI-coated NCM83 cathodes achieve exceptional long-term cycling stability with a high-capacity retention of 82.2% after 400 cycles at 1 C. This work elucidates the critical role of dynamic covalent chemistry in stabilizing Ni-rich cathode interfaces and establishes a new paradigm for the design of high-energy-density batteries through mechano-adaptive interfacial engineering.