Abstract
In this study, we chose maleimide-based additives which are isomer for each other (the maleimide substituent on the benzene are para-, meta-, and ortho- position) to investigate the structural effect in SEI and the battery performance. First, the cyclic voltammetry (CV) measurement showed that the reduction potential of maleimide-based additive was prior to other components. Then, the structure of maleimide product was further found retaining the same connected sites to benzene and keeping C=C configuration after reduction based on the results of nuclear magnetic resonance (NMR). The possible product structure for different maleimide-based additive was proposed in this study. In the analysis of impedance spectra, the resistance of SEI was influenced by steric hindrance of the additive. The X-ray photoelectron spectroscopy (XPS) demonstrated the content of a specific inorganic compound, LiF, was decreased due to the existence of maleimide-based additive in the electrolyte. Finally, in the battery performance test, the structural effect of additive showed remarkable divergence in discharge capacity loss in the initial 1C/1C cycle test. As the cycle proceeded, the discharge capacity of batteries with maleimide additives reached a steady state and did not reduce anymore. Besides, the performance of the additive with large steric hindrance even excelled the one without any additive.