Deciphering the Purification Additive Chemistries for Ultra-Stable High-Voltage Lithium-Ion Batteries.

Abstract

Hydrogen fluoride (HF)-induced degradation of electrode materials and interphases presents a significant challenge for high-voltage Li-ion batteries. However, progress in developing advanced HF-scavenging additives is hindered by a limited understanding of HF-elimination reactions and the absence of a robust design principle. Herein, it is proposed to analyze the energy decomposition analysis of 24 additives to elucidate the underlying HF-scavenging mechanism and identify key factors influencing HF-additives reactions. The findings reveal that orbital contribution ratio (OCR) is a critical determinant of chemical bonding in HF-additive reactions. Specifically, an 80% OCR for H⁺ and a 53% OCR for F^- are essential for completing HF elimination. Based on these insights, a general principle for designing effective HF-elimination additives is proposed and heptamethyldisilazane as a particularly well-suited candidate, exhibiting optimal OCR for both H⁺ and F^- ions is identified. Remarkably, the addition of just 1 wt.% HMDS significantly eliminats HF, inhibiting cathode-to-anode crosstalk behaviors and limiting electrode and interphase degradation. This guardian endows graphite/LiNi_0.8Co_0.1Mn_0.1O₂ pouch cells with a significant performance improvement, achieving 80% capacity retention over 2528 cycles, a substantial improvement compared to the 1139 cycles observed without HF-elimination additive. The study provides valuable insights for the design of advanced electrolyte additives for high-performance Li-ion batteries.