P-Hydroxybenzoic acid (HBA) as a functional electrolyte additive to regulate the electrode/electrolyte interfacial films and improve the electrochemical performance of lithium metal batteries

Abstract

From the perspective of intermolecular forces, p-hydroxybenzoic acid (HBA) as a functional additive to regulate the electrode/electrolyte interface films and improve the electrochemical performance of lithium metal batteries (LMBs) with LiFePO4 (LFP) cathode. The results show that the HBA forms intermolecular hydrogen bonds with the solvent and lithium salt, which can reduce the free solvent molecules in the electrolyte, inhibit the decomposition of the solvent, and stabilize the electrolyte system. Compared with the batteries with blank electrolyte, the capacity retentions of Li||LFP batteries with HBA additive increase from about 69.3% to 86.7% after 500 cycles. After cycling, the interface impedance (RSEI) of the batteries with blank electrolyte is also much higher than that with HBA, indicating that HBA can effectively reduce the interface impedance during cycling. And combined with the spectroscopic characterization, it is also indicated that the functional electrolyte can promote the formation of a robust solid-electrolyte interface (SEI), inhibit the growth of lithium dendrites, and deposit lithium evenly and smoothly. Besides the functionalized electrolyte, this work also gives a new strategy to develop functionalized electrolytes for high-performance LMBs.