High-voltage stability of LiBF₄ - propylene carbonate solutions in intermediate concentration range is studied by means of cyclic voltammetry, galvanostatic cycling and X-ray photoelectron spectroscopy using LiCoPO₄ and LiNi_0.5Mn_1.5O₄ cathode materials. Coulombic efficiency improves with increasing salt-to-solvent molar ratio from 1:12 to 1:4 (∼0.8 m–2.5 m solutions), reaching 98% at 1C charge/discharge rate for 1:4 electrolyte upon cycling of LiNi_0.5Mn_1.5O₄ up to 5 V vs. Li/Li⁺. The same positive trend is observed for discharge capacities, cycling stability and capacity scattering for both high-voltage cathode materials. X-ray photoelectron spectroscopy of the electrodes studied after cycling in solutions of different concentrations does not reveal any drastic difference in surface composition. Interface pre-formation experiment shows that the presence of the interface layer formed at semi-concentrated 1:4 electrolyte does not have a major impact on the electrochemical properties of the dilute solution. We assume that the enhanced oxidation stability of the concentrated solutions itself is a reason of improving the electrochemical performance rather than the cathode-electrolyte interface properties.

利用LiCoPO ₄和LiNi _0.5 Mn _1.5 O ₄正极材料，通过循环伏安法，恒电流循环和X射线光电子能谱研究了在中等浓度范围内的LiBF _4-碳酸亚丙酯溶液的高压稳定性。当盐与溶剂的摩尔比从1:12增加到1：4（〜0.8 m–2.5 m溶液）时，库仑效率得以提高，当LiNi _0.5 Mn循环时，对于1：4电解质，在1C充放电速率下，库仑效率达到98％_1.5 O _4（最高5 V）vs.Li/Li ⁺。对于两种高压阴极材料，在放电容量，循环稳定性和容量散射方面观察到相同的积极趋势。在不同浓度的溶液中循环后研究的电极的X射线光电子能谱未显示出表面成分的任何显着差异。界面预形成实验表明，在半浓缩的1：4电解质中形成的界面层的存在对稀溶液的电化学性能没有重大影响。我们认为浓缩溶液本身增强的氧化稳定性是改善电化学性能而不是改善阴极-电解质界面性能的原因。