In situ real-time gravimetric and viscoelastic probing of surface films formation on lithium batteries electrodes

It is generally accepted that solid-electrolyte interphase formed on the surface of lithium-battery electrodes play a key role in controlling their cycling performance. Although a large variety of surface-sensitive spectroscopies and microscopies were used for their characterization, the focus was on surface species nature rather than on the mechanical properties of the surface films. Here we report a highly sensitive method of gravimetric and viscoelastic probing of the formation of surface films on composite Li₄Ti₅O₁₂ electrode coupled with lithium ions intercalation into this electrode. Electrochemical quartz-crystal microbalance with dissipation monitoring measurements were performed with LiTFSI, LiPF₆, and LiPF₆ + 2% vinylene carbonate solutions from which structural parameters of the surface films were returned by fitting to a multilayer viscoelastic model. Only a few fast cycles are required to qualify surface films on Li₄Ti₅O₁₂ anode improving in the sequence LiPF₆ < LiPF₆ + 2% vinylene carbonate << LiTFSI.