Trace Multifunctional Additive Enhancing 4.8 V Ultra-High Voltage Performance of Ni-Rich Cathode and SiOx Anode Battery

Abstract

The combination of high-voltage Ni-rich cathodes and high-capacity Si-based anodes can result in high energy density for next-generation batteries. However, the practical capacities accesses are severely hindered by unstable electrode/electrolyte interphases (EEI) and irreversible structural degradation, which necessitates efficient additives in electrolyte for generating stable EEI. Herein, a multifunctional additive, 3-Fluoro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)picolinonitrile (FTDP) is proposed to construct robust interfaces at both cathodic and anodic surface, so as to enhance electrochemical performance. FTDP is preferentially decomposed to form B-contained and cyano (CN) group-rich cathode electrolyte interphase (CEI), as well as LiF-, Li₃N-rich solid electrolyte interphase (SEI), simultaneously, resulting in the integrity and stability of electrodes. Moreover, the FTDP-derived CEI can suppress transition metal ions dissolution, further facilitating battery cyclability. The multifunctionality of FTDP, including quenching free radicals, alleviating the hydrolysis of LiPF₆ and inhibiting HF generation, thus greatly improving interfacial stability. With trace addition of 0.2 wt.%, NCM811/Li cell can be performed at an extreme condition, i.e., ultra-high voltage (4.8 V), high temperature (60 °C) and high rate (10C). 1.6 Ah NCM811/SiO_x pouch cell delivers a high capacity retention of 84.0% after 300 cycles.