Effect of Phosphorus-Doping on Electrochemical Performance of Silicon Negative Electrodes in Lithium-Ion Batteries

Abstract

The effect of phosphorus (P)-doping on the electrochemical performance of Si negative electrodes in lithium-ion batteries was investigated. Field-emission scanning electron microscopy was used to observe changes in surface morphology. Surface crystallinity and the phase transition of Si negative electrodes before and after a charge-discharge cycle were investigated by Raman spectroscopy and X-ray diffraction. Li insertion energy into Si was also calculated based on computational chemistry. The results showed that a low P concentration of 124 ppm has a meaningful influence on the electrochemical properties of a Si negative electrode; the cycle performance is improved by P-doping of Si. P-doping suppresses the changes in the surface morphology of a Si negative electrode and the phase transition during a charge-discharge cycle. Li insertion energy increases with an increase in the P concentration; Li insertion into P-doped Si is energetically unfavorable, which indicates that the crystal lattice of Si shrinks as a result of the replacement of some Si atoms with smaller P atoms, and therefore, it is more difficult to insert Li into P-doped Si. These results reveal that suppression of the phase transition reduces the large change in the volume of Si and prevents a Si negative electrode from disintegrating, which helps to improve the otherwise poor cycle performance of a Si electrode.

Elucidation of the Reaction Behavior of Silicon Negative Electrodes in a Bis(fluorosulfonyl)amide‐Based Ionic Liquid Electrolyte

“…The Si layer in the PC became porous after the 20th cycle, whereas that in the PP1MEM‐FSA was not very porous. A similar phenomenon has been reported for other Si‐based electrodes in PC . Therefore, this phenomenon can be attributed to the electrolyte rather than the electrode.…”

Electrochemical performance of Si anode modified with carbonized gelatin binder

“…6a, while the lithiation process of carbonized gelatin also makes a bit of contribution, which can be confirmed by Fig. 6b and d. In the anodic sweep, two peaks at around 0.3 V and 0.5 V are assigned to the extraction of Li-ions from Li-Si alloys [44,45] and amorphous Si is formed [46]. In the following lithiation process, the amorphous Si, instead of the initial crystalline Si, takes part in the lithiation reaction.…”

Lithiation and Delithiation Reactions of Binary Silicide Electrodes in an Ionic Liquid Electrolyte as Novel Anodes for Lithium‐Ion Batteries

“…Each silicide electrode was prepared by a gas deposition (GD) method, which does not require a binder or conductive agent . The detailed conditions of GD were described in our previous paper . The weight of the deposited active material was 30±2 μg.…”

“…Many research groups have put significant efforts into these issues: coating Si with conductive materials to reduce the electrical resistivity, synthesizing nanostructured Si materials to cushion volume expansion,, doping Si with impurities to increase its electrical conductivity and/or suppress its phase transition from Si to crystalline Li 15 Si 4 phases ,. We have previously reported that a composite electrode that consisted of elemental Si and a binary silicide (M y Si z , M : metal), such as LaSi 2 and Gd−Si, shows a superior electrochemical performance in conventional organic electrolytes compared to the Si‐alone electrode ,.…”