The resurgence of the lithium metal battery requires innovations in technology, including the use of non-conventional liquid electrolytes. The inherent electrochemical potential of lithium metal (-3.04 V vs. SHE) inevitably limits its use in many solvents, such as acetonitrile, which could provide electrolytes with increased conductivity. The aim of this work is to produce an artificial passivation layer at the lithium metal/electrolyte interface that is electrochemically stable in acetonitrile-based electrolytes. To produce such a stable interface, the lithium metal was immersed in fluoroethylene carbonate (FEC) to generate a passivation layer via the spontaneous decomposition of the solvent. With this passivation layer, the chemical stability of lithium metal is shown for the first time in 1 m LiPF in acetonitrile.
h i g h l i g h t s < Free-standing PEDOTeLiFePO 4 composites for lithium ion batteries by dynamic three phase interline electropolymerization. < PEDOTeLiFePO 4 serves as current collector, binder and carbon filler free functional electrodes. < LiFePO 4 mass fraction of 33.5 wt.% in the composite film confirmed by TGA analysis. < The cathode discharge capacity of the PEDOTeLiFePO 4 composite film is 75 mAh g À1 at C/10.
a b s t r a c tFree-standing poly(3,4-ethylenedioxythiophene) (PEDOT)eLiFePO 4 composite films were successfully prepared by dynamic three phase interline electropolymerization (D3PIE). These films were used without further modification as the positive electrode in standard lithium ion batteries. As such, this new process eliminates all electrochemically inactive materials (carbon, polymer binder and current collector) used in conventional composite cathodes. The PEDOTeLiFePO 4 composite film offers a discharge capacity of 75 mAh g À1 at the C/10 rate and high capacity retention at the C/2 rate. When reporting this value to the relative amount of LiFePO 4 in the PEDOT-LiFePO 4 composite film, the discharge capacity reached 160 mAh g À1 , close to the theoretical maximum value (170 mAh g À1 ). As such, this approach yield highly functional hybrid free-standing conductive polymer/active material composite cathode with controllable size and structure.
Sodium ion batteries represent an interesting alternative to lithium ion batteries for large scale energy storage, due to the inexpensive and massive sources of sodium. Moreover, the incertitude related to lithium resources and their suppliers could become a major problem in the coming years. In this study, synthesis and electrochemical analyses were performed to examine TiO2 (B) and Na2Ti6O13's potential as negative electrode materials in sodium ion batteries. These materials were selected due to their well-known small cation insertion redox reactions.
Understanding the kinetics of the charging and discharging processes in battery materials is important to improving high power performance. As such, we here investigate the kinetics of LiFePO 4 relithiation by reduction with lithium iodide. Unlike standard electrochemical kinetic analysis, which yields a convoluted response of all the components of the composite electrode, this approach probes only the kinetics of the electroactive material particles. The kinetic data was compared to the Avrami solid state reaction model and a statistical model by Bai and Tian, Electrochim. Acta, 2013, 89, 644. Different from chemical delithiation, the lithiation reaction does not fit a solid solution one-dimensional diffusion model, rather it follows the Avrami equation (Avrami exponent 0.6) with an activation energy of 50 kJ mol −1 . The obtained reaction rate information is central to the development of physically accurate quantitative battery models.
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