Organic Nitrate Additive for High-Rate and Large-Capacity Lithium Metal Anode in Carbonate Electrolyte

Lithium nitrate has been widely used to improve the interfacial stability of Li metal anode in ether electrolyte. However, the low solubility limits its application in carbonate electrolytes for high-voltage Li metal batteries. Herein, nitrated polycaprolactone (PCL-ONO₂ ), which is prepared via the acylation of polycaprolactone diol (PCL-diol) followed by the grafting of nitrate group, has been proposed as an electrolyte additive to introduce high-concentration NO₃ ^- into carbonate electrolytes for the first time. The theoretical calculations and X-ray photoelectron spectroscopy depth profiling demonstrate that the PCL-ONO₂ additive preferentially reacts with Li metal and in situ constructs a stable dual-layered solid electrolyte interphase film, presenting an inner nitride-rich layer and an outer flexible PCL-based layer on the surface of Li metal anode. As a result, the Li metal anode delivers an impressive long-term cycling performance over 1400 h at an elevated area capacity of 10.0 mAh cm^-2 and an ultrahigh current density of 10.0 mA cm^-2 in the Li symmetrical cells. Moreover, the PCL-ONO₂ additive enables the full cells constructed by coupling high-loading LiFePO₄ (20.0 mg cm^-2 ) or LiNi_0.5 Co_0.2 Mn_0.3 (16.5 mg cm^-2 ) cathode and thin Li metal anode (≈50 µm) to demonstrate greatly improved cycling stability and rate capability.