A Novel Anion Receptor Additive for −40 °C Sodium Metal Batteries by Anion/Cation Solvation Engineering

Sodium metal batteries, known for their high theoretical specific capacity, abundant reserves, and promising low-temperature performance, have garnered significant attention. However, the large ionic radius of Na⁺ and sluggish transport kinetics across the interfacial structure hinder their practical application. Previous reviews have rarely regulated electrolyte performance from the perspective of anions, as important components of the electrolyte, the regulation mechanism is not well understood. Herein, a novel anion receptor additive, 4-aminophenylboronic acid pinacol ester (ABAPE), is proposed to weaken the coupling between anions and cations and accelerate Na⁺ transport kinetics. The results of theoretical calculations and X-ray photoelectron spectroscopy with deep Ar-ion etching demonstrate that the introduction of this additive alters the solvation structure of Na⁺, reduces the desolvation barrier and forms a stable and dense electrode-electrolyte interface. Moreover, ABAPE forms hydrogen bonds (-NH ⋅ ⋅ ⋅ O/F) with H₂O/HF, effectively preventing the hydrolysis of NaPF₆ and stabilizing acidic species. Consequently, the Na||Na symmetric cell exhibits excellent long-cycle performance of 500 h at 1 mA cm^-2 and 0.5 mAh cm^-2. The Na||Na₃V₂(PO₄)₃ (NVP) cell with the addition of ABAPE maintains a capacity retention of 84.29 % at 1 C after 1200 cycles and presents no capacity decay over 150 cycles at -40 °C.