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Interfacial modification is one of the most important technologies to improve the overall electrochemical properties for Ni-rich cathode. Herein, a novel strategy of in-situ planting electrolyte film-forming additive on single...

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Functionalized molecular sieve SBA-15 with trimethylchlorosilane was used as an inorganic filler in a poly(ethyleneoxide) (PEO) polymer matrix to synthesize a composite solid-state polymer electrolyte (CSPE) using LiClO4 as the doping salts, which is designated to be used for rechargeable lithium batteries. The methyl group-functionalized SBA-15 ((f)SBA-15) powder possesses more hydrophobic characters than SBA-15, which improves the miscibility between the (f)SBA-15 filler and the PEO matrix. The interaction between the (f)SBA-15 and PEO polymer matrix was investigated by scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry. Linear sweep voltammetry and electrochemical impedance spectroscopy were employed to study the electrochemical stability windows, ionic conductivity, and interfacial stability of the CSPE. The temperature dependence of the change of the PEO polymer matrix in the CSPE from crystallization to amorphous phase was surveyed, for the first time, at different temperature by Fourier transform infrared emission spectroscopy. It has demonstrated that the addition of the (f)SBA-15 filler has improved significantly the electrochemical compatibility of the CSPE with a lithium metal electrode and enhanced effectively the ion conductivity of the CSPE

Systematic electrochemical impedance spectroscopic (EIS) combining with cyclic voltammograms (CV) and charge/discharge test have been used to investigate the reaction and capacity fade mechanism of LiNi0.5Co0.2Mn0.3O2 electrode with high cutoff voltage 3.0–4.5 V and high working temperature 55°C. It was found that the phase transformation and the Li-Ni site exchange in lattice at high voltage (>4.3 V) acted on charge transfer process were the main reasons of capacity fading with the cutoff voltage of 3.5–4.5 V. The degradation of LiNi0.5Co0.2Mn0.3O2 cathode with high-temperature was mainly associated with the strong catalytic activity of Ni4+ which can cause the side reaction between electrode and electrolyte to form unstable SEI film as well as the acceleration of phase transformation on the surface of electrode with high electrode polarization potential. Furthermore, it was found that improving the performance of SEI film should be one of the most important methods for improving the cycling performance of LiNi0.5Co0.2Mn0.3O2 cathode under high-temperature and we have proved it by systematic discussing the EIS results of the LiNi0.5Co0.2Mn0.3O2 cathode in electrolyte with fluoro-ether as an additive.

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The storage behavior and the first delithiation of LiCoO 2 electrode in 1 mol/L LiPF 6 -EC : DMC : DEC electrolyte were investigated by electrochemical impedance spectroscopy (EIS). It has found that, along with the increase of storage time, the thickness of SEI film increases, and some organic carbonate lithium compounds are formed due to spontaneous reactions occurring between the LiCoO 2 electrode and the electrolyte. When electrode potential is changed from 3.8 to 3.95 V, the reversible breakdown of the resistive SEI film occurs, which is attributed to the reversible dissolution of the SEI film component. With the increase of electrode potential, the thickness of SEI film increases rapidly above 4.2 V, due to overcharge reactions. The inductive loop observed in impedance spectra of the LiCoO 2 electrode in Li/LiCoO 2 cells is attributed to the formation of a Li 1-x CoO 2 /LiCoO 2 concentration cell. Moreover, it has been demonstrated that the lithium-ion insertion-deinsertion in LiCoO 2 hosts can be well described by both Langmuir and Frumkin insertion isotherms, and the symmetry factor of charge transfer has been evaluated at 0.5.Li-ion batteries, LiCoO 2 , EIS, SEI film, inductance