Recent studies show that the SEI on lithium and on LixC6 anodes in liquid nonaqueous solutions consists of many different materials including Li2O , LiF, LiCl, Li2CO3,LiCO2‐R , alkoxides, and nonconducting polymers. The equivalent circuit for such a mosaic‐type SEI electrode is extremely complex. It is shown that near room temperature the grain‐boundary resistance (R gb) for polyparticle solid electrolytes is larger than the bulk ionic resistance. Up to now, all models of SEI electrodes ignored the contribution of R gb to the overall SEI resistance. We show here that this neglect has no justification. On the basis of recent results, we propose here for SEI electrodes equivalent circuits which take into account the contribution of grain‐boundary and other interfacial impedance terms. This model accounts for a variety of different types of Nyquist plots reported for lithium and LixC6 electrodes in liquid nonaqueous and polymer electrolytes.

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This paper presents and discusses fundamental processes taking place at the lithium and LixC6 electrode/electrolyte interphases and models for these interphases. We deal with both nonaqueous and polymer (dry and gel) electrolytes, graphitized and nongraphitized carbonaceous materials as anodes for Li-ion batteries. Each electrode/electrolyte combination has its own unique features and problems but there are some general phenomena common to all of them. Issues to be reviewed include SEI composition, morphology and formation reactions, graphite surface modifications including chemical bonded SEI and micro channels formation, electrode degradation processes, lithium deposition-dissolution and intercalation-deintercalation mechanisms, rate-determining steps (RDS), electrolyte and electrode parameters and conditions affecting the above mentioned processes. Technologyrelated issues are emphasized.

The high areal-energy and power requirements of advanced microelectronic devices favor the choice of a lithium-ion system, since it provides the highest energy density of available battery technologies suitable for a variety of applications. Several attempts have been made to produce primary and secondary thin-film batteries utilizing printing techniques. These technologies are still at an early stage, and most currently-printed batteries exploit printed electrodes sandwiching self-standing commercial polymer membranes, produced by conventional extrusion or papermaking techniques, followed by soaking in non-aqueous liquid electrolytes. In this work, we suggest a novel flexible-battery design and report the initial results of development and characterization of novel 3D printed allsolid-state electrolytes prepared by fused-filament fabrication (FFF). The electrolytes are composed of LiTFSI, polyethylene oxide (PEO), which is a known lithium-ion conductor, and polylactic acid (PLA) for enhanced mechanical properties and high-temperature durability. The 3D printed electrolytes were characterized by means of ESEM imaging, mass spectroscopy, differential scanning calorimetry (DSC) and electrochemical impedance spectroscopy (EIS). TOFSIMS analysis reveals formation of lithium complexes with both polymers. The flexible all-solid LiTFSI-based electrolyte exhibited bulk ionic conductivity of 3 × 10 −5 S/cm at 90°C and 156ohmxcm 2 resistance of the solid electrolyte interphase (SEI). We believe that the coordination mechanism of the lithium cation by the oxygen of the PLA chain is similar to that of PEO and local relaxation motions of PLA chain segments could promote Li-ion hopping between oxygens of adjacent CH-O groups. What is meant by this is that PLA not only improves the mechanical properties of PEO, but also serves as a Li-ion-conducting medium. These results pave the way for a fully printed solid battery, which enables free-form-factor flexible geometries.

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