Nanoscale silicon film electrodes in Li-ion battery undergo great deformations leading to electrochemical and mechanical failures during repeated charging-discharging cycles. In-situ experimental characterization of the stress/strain in those electrodes still faces big challenges due to remarkable complexity of stress/strain evolution while it is still hard to predict the association between the electrode cycle life and the measurable mechanical parameters. To quantificationally investigate the evolution of the mechanical parameters, we develop a new full field 3D measurement method combining digital image correlation with laser confocal profilometry and propose a strain criterion of the failure based on semi-quantitative analysis via mean strain gradient (MSG). The experimental protocol and results illustrate that the revolution of MSG correlates positively with battery capacity decay, which may inspire future studies in the field of film electrodes.
Silicon-based carbon composites are believed as promising anodes in the near future due to their outstanding specific capacity and relatively lower volume effect compared to pure silicon anodes. Herein, a multilayer spherical core–shell (M-SCS) electrode with a graphite framework prepared with Si@O-MCMB/C nanoparticles is developed, which aims to realize chemically/mechanically stability during the lithiation/delithiation process with high specific capacity. An electrochemical-/mechanical-coupling model for the M-SCS structure is established with various chemical/mechanical boundary conditions. The simulation of finite difference method (FDM) has been conducted based on the proposed coupling model, by which the diffusion-induced stress along both the radial and the circumferential directions is determined. Moreover, factors that influence the diffusion-induced stress of the M-SCS structure have been discussed and analyzed in detail.
The effects of varied contents of Ni (1.2 wt.%, 1.6 wt.%) and Fe (0.6 wt.%, 0.8 wt.%) on the microstructure and high temperature mechanical properties of Al-Si alloy were studied using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and tensile testing machine. The experimental results demonstrate that Ni element plays a crucial role in modifying the Fe-rich phase type, morphology and distribution in the Al-Si alloy. The addition of 1.2 wt.% Ni and 0.6 wt.% Fe could generate a Chinese script Fe-rich strengthening phase in Al-Si alloy. Further increasing to 1.6 wt.% Ni and 0.8 wt.% Fe, the long needle-shape Fe-rich phase was detected. High temperature tensile properties of the alloy were significantly improved, because of the Chinese script Fe-rich strengthening phase in the Al-Si alloy containing 1.2 wt.% Ni and 0.6 wt.% Fe. The ultimate tensile strength (UTS) of Al-Si alloy with 1.2 wt.%Ni-0.6 wt.% Fe is up to 229 MPa, 174 MPa and 139 MPa at 250 °C, 300 °C and 350 °C, respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.