Electrochemical activation of a diatom-derived SiO2/C composite anode and its implementation in a lithium ion battery

Influence of Oxygen Content on the Structural Evolution of SiOx Thin-Film Electrodes with Subsequent Lithiation/Delithiation Cycles

“…It is likely that Si–O bonds are initially electrochemically inactive, and that Si–Si bonds established after lithiation can be reversibly cycled. This process, known as “electrochemical activation” of silica, is generally observed after additional cycling of SiO 2 , resulting in an increase in ionic conductivity and capacity. − This activation of near-fully saturated films is observed in the current study. The CV curve in Figure b shows that the Li–Si peaks (peaks 1 and 2) start to emerge with subsequent cycling.…”

“…Two likely mechanisms that result in these similar states are described above: (1) some oxygen is incorporated from the liquid electrolyte in the SiO 0.3 and SiO films, possibly via reactions with the SEI, and (2) disproportionation/reduction converts the oxygen-rich material into various lithium silicate species and disproportionated Si. 26,27 This hypothesis is strongly supported by the experiments with the lower oxygen content films (SiO 0.3 and SiO), whereas there are some quantitative differences between these data sets and the lithium silicate content for the SiO 2 material. This may indicate that the higher oxygen content alters the silicate formation kinetics; however, the similar reversible capacities after 100 cycles still suggest that all of the materials are approaching a similar state.…”

“…As shown in the Si 2p spectra in Figure c (up to the 10th cycle), the film consists of largely SiO 2 with minimal growth of Li 2 SiO 3 /Li 4 SiO 4 species. However, as activation begins around the 20th cycle, where bond-breaking and establishments of Si–Si bonds and are expected to occur, − the film undergoes significant structural rearrangement. This is seen in Figures c and c, where there is a significant reduction in the SiO 2 peak after the 25th cycle and a large growth of Li x SiO y species.…”

Templated Synthesis of SiO2 Nanotubes for Lithium-Ion Battery Applications: An In Situ (Scanning) Transmission Electron Microscopy Study

“…The significant reduction of the total cell resistance (and conversely, increase in ionic conductivity) from the initial EIS to the EIS carried out after 100 and 200 cycles seen in Figure E indicates “electrochemical activation” of the electrode by cycling. , Impedance fit calculated using equivalent circuit shown in Figure S8 shows a decrease of the total resistance ( ∑ 1 4 R n ) from 344.5 to 63.21 Ω (where R 1 is the equivalent series resistance for the electrolyte, current collectors, and electrode materials, R 2 is the interfacial resistance between the CNTs and SiO 2 nanorods, R 3 is the SEI resistance, and R 4 is the charge-transfer resistance at the interface between the electrolyte and active materials) . This is believed to be due to initial lithiation cycles reconstructing the electrode material to allow for easier Li + -ion migration within the hollow nanorods, enhancing the degree of electrochemical utilization . Loss of Li + -ions from the electrolyte to the anode material over cycles can form an amorphous Li 2 O–SiO 2 glass from the reduction of SiO 2 in the presence of Li.…”

“…This configurability is one of the benefits of this particular synthesis method as the dimensions of the material (such as the SiO 2 wall thickness and the ZnO nanorod size by the reaction time) can be readily and easily tuned to optimize the electrochemical performance. The results presented are comparable to some of the state-of-the-art previously reported. − …”