Multifunctional Siloxane Additive Enabling Ultrahigh-Nickel Lithium Battery with Long Cycle Life at 30  and 60 °C

Ultrahigh-nickel layered oxide cathodes (≥90% nickel) possess exceptionally high discharge capacities, which can significantly improve the energy density of lithium-ion batteries and alleviate the driving range anxiety of electric vehicles. However, the high interfacial reactivity of ultrahigh-nickel cathodes, especially the detrimental side reactions with harmful acidic species like HF in the electrolyte, can deteriorate the battery interface and reduce the cycle life, hindering their practical application. In this study, 3-isocyanatopropyltrimethoxysilane (PTTS-NCO) is introduced as the electrolyte additive, which can effectively scavenge the harmful acidic species in the electrolyte and form a protective surface layer at the electrode/electrolyte interface, thereby enhancing the electrochemical performance of the battery (NCM90/Li). Specifically, the most effective battery based on the PTTS-NCO additive can maintain 70.3% of its capacity after 500 cycles at 30 °C. Even under a high cathode loading (3.0 mAh cm^-2), it can retain 86.2% of its capacity after 300 cycles, far exceeding the base battery. Furthermore, it exhibits good performance under the harsh high-temperature environment, maintaining over 70.3% capacity retention in the NCM90/Li battery up to 350 cycles at 60 °C. This work demonstrates the great potential of multifunctional siloxane additive in lithium batteries based on ultrahigh-nickel cathode.