Decorating silicon surface by an electroactive covalent organic framework to develop high-performance lithium-ion batteries

Silicon (Si) anodes are widely considered as promising candidates for high-performance lithium-ion batteries in the future due to their high specific capacity (4200.0 mAh g−1) and low operating potential (0.4 V vs. Li+/Li). However, their excessive volume expansion and continuous interfacial side reactions pose challenges for further applications. In this study, we use an electrochemically active covalent organic framework (COF) material to modify the surface of Si nanoparticles, aiming to simultaneously enhance the stability of both the macroscopic and microscopic structures of Si anodes. The COF decorative layer accelerates lithium ions transportation and reduces the electrode polarization, participates in the formation of a stable and robust solid electrolyte interphase film rich in LiF and LiN, decreases the electrode expansion from 365 % to 173 %, and well maintains the spherical structure of Si nanoparticles and the integrity of the electrode. Under the positive effective of the COF layer, the modified Si anode demonstrates high-rate and long-cycle properties, it achieves a specific capacity of more than 2000.0 mAh g−1 under a high current of 10 C, and maintains 1188.7 mAh g−1 after 500 cycles at 0.5 C. In contrast, the specific capacities of the pure Si electrode can be almost negligible at the same conditions. The advantage of lithium storage performance is also reflected in full cells.