Recent studies on the correlation between surface chemistry, morphology, three-dimensional structures and performance of Li and Li-C intercalation anodes in several important electrolyte systems

This paper reviews some advances in the comparative study of lithium and graphite electrodes in a large matrix of solvents, salts and additives. The major purpose of this work was to support R&D of lithium metal and Li-ion batteries by understanding the correlation between the anode's performance, its morphology and three-dimensional structure upon cycling, interfacial electronic properties and the surface chemistry. The emphasis was on the use of the most sophisticated novel spectroscopic tools in conjunction with standard electrochemical techniques. These included in situ and ex situ Fourier-transform infrared spectroscopy (FT-IR) and X-ray difraction (XRD), impedance spectroscopy and atomic force microscopies (EIS and AFM, respectively), X-ray photospectroscopy (XPS), energy dispersive analysis of X-rays (EDAX) and electrochemical quartz crystal microbalance (EQCM). Major achievements included: (i) analysis of the surface reactions which are taking place on both the lithium and the carbon electrodes which form surface films that control the electrochemical behaviour in many electrolyte systems of interest; (ii) successful and useful application of AFM and EQCM in order to study the surface film formation and Li-deposition processes; (iii) understanding the correlation between the reversibility and stability of graphite electrodes in Li-intercalation processes and their surface chemistry, and (iv) finding an interesting correlation between the three-dimensional structure of graphite electrodes, the diffusion coefficient of Li⁺ and their voltammetric behaviour in Li-intercalation processes.