Trace Multifunctional Additive Enhancing 4.8 V Ultra‐High Voltage Performance of Ni‐Rich Cathode and SiO_x 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/SiOx pouch cell delivers a high capacity retention of 84.0% after 300 cycles.