RESUMO
With the development of flexible mobile devices, flexible Li-ion batteries have naturally received much attention. Previously, all reported flexible components have had shortcomings related to power and energy performance. In this research, in order to overcome these problems while maintaining the flexibility, honeycomb-patterned Cu and Al materials were used as current collectors to achieve maximum adhesion in the electrodes. In addition, to increase the energy and power multishelled LiNi0.75Co0.11Mn0.14O2 particles consisting of nanoscale V2O5 and LixV2O5 coating layers and a LiδNi0.75-zCo0.11Mn0.14VzO2 doping layer were used as the cathode-anode composite (denoted as PNG-AES) consisting of amorphous Si nanoparticles (<20 nm) loaded on expanded graphite (10 wt %) and natural graphite (85 wt %). Li-ion cells with these three elements (cathode, anode, and current collector) exhibited excellent power and energy performance along with stable cycling stability up to 200 cycles in an in situ bending test.
RESUMO
The electrode concept of graphite and silicon blending has recently been utilized as the anode in the current lithium-ion batteries (LIBs) industry, accompanying trials of improvement of cycling life in the commercial levels of electrode conditions, such as the areal capacity of approximately 3.3 mAh/cm2 and volumetric capacity of approximately 570 mAh/cm3. However, the blending concept has not been widely explored in the academic reports, which focused mainly on how much volume expansion of electrodes could be mitigated. Moreover, the limitations of the blending electrodes have not been studied in detail. Therefore, herein we investigate the graphite blending electrode with micron-sized SiOx anode material which is one of the most broadly used Si anode materials in the industry, to approach the commercial and practical view. Compared to the silicon micron particle blending electrode, the SiOx blending electrode showed superior cycling performance in the full cell test. To elucidate the cause of the relatively less degradation of the SiOx blending electrode as the cycling progressed in full-cell, the electrode level expansion and the solid electrolyte interphase (SEI) thickening were analyzed with various techniques, such as SEM, TEM, XPS, and STEM-EDS. We believe that this work will reveal the electrochemical insight of practical SiOx-graphite electrodes and offer the key factors to reducing the gap between industry and academic demands for the next anode materials.
RESUMO
Despite the advantage of high capacity, the practical use of the silicon anode is still hindered by large volume expansion during the severe pulverization lithiation process, which results in electrical contact loss and rapid capacity fading. Here, a combined electrochemical and computational study on the factor for accommodating volume expansion of silicon-based anodes is shown. 1D silicon-based nanostructures with different internal spaces to explore the effect of spatial ratio of voids and their distribution degree inside the fibers on structural stability are designed. Notably, lotus-root-type silicon nanowires with locally distributed void spaces can improve capacity retention and structural integrity with minimum silicon pulverization during lithium insertion and extraction. The findings of this study indicate that the distribution of buffer spaces, electrochemical surface area, as well as Li diffusion property significantly influence cycle performance and rate capability of the battery, which can be extended to other silicon-based anodes to overcome large volume expansion.
RESUMO
Amorphous SiO2 coating layers with thicknesses of ca. 2, 7, 10, and 15 nm are introduced into bulk@nanowire core@shell Si particles via direct thermal oxidation at 650-850 °C. Of the coated samples, Si with a coating thickness of ca. 7 nm has the best electrochemical performance. This sample shows an initial discharge capacity of 2279 mA h g(-1) with a Coulombic efficiency of 92% and displays 83% capacity retention after 50 cycles at 0.2C rate.