Synthesis, Lithium Insertion and Thermal Stability of Si–Mo Alloys

Abstract

Li insertion was investigated in SixMo100−x (90 ≥ x ≥ 70, Δx = 10) alloys prepared by mechanical ball milling. X-ray diffraction (XRD) and quantitative phase analysis were used to analyze phase compositions of these Si–Mo alloys, and how these phase compositions changed with milling times. The results of quantitative phase analysis showed that cr-Si converted into a-Si within 1 h during milling, and the Si–Mo reactions were nearly complete after only 4-h milling. During electrochemical cycling, the Si–Mo samples with high initial Mo contents and long milling times displayed good crystalline Li15Si4 suppression and stable cycling performance. In addition, thermal stability of some selected Si–Mo alloys was studied. The Si80Mo20 16 h alloy combines good thermal stability and a high volumetric capacity of about 1300–1400 Ah L−1 after heat treatment at 600 °C or 800 °C, which may allow the alloy to be further improved by carbon coating at high temperature.

Beyond Thin Films: Clarifying the Impact of c-Li15Si4 Formation in Thin Film, Nanoparticle, and Porous Si Electrodes

“…17,36,50−53 The hypothesis that alloying induces stress, thereby improving capacity retention by suppressing c-Li 15 Si 4 , has been applied to nano-and micronsized silicon particle electrodes as well as thin films. 50,54,55 However, most, if not all previous studies that find a correlation between the suppression of c-Li 15 Si 4 formation and capacity retention, achieve this suppression through material changes that are convoluted with other beneficial effects. For instance, a capping layer on top of a Si film can induce clamping, thereby preventing c-Li 15 Si 4 by aforementioned stress−voltage coupling, while also minimizing reactivity with the electrolyte.…”

“…For instance, a capping layer on top of a Si film can induce clamping, thereby preventing c-Li 15 Si 4 by aforementioned stress−voltage coupling, while also minimizing reactivity with the electrolyte. 26,56−58 Prolonged ball-milling of Si with Mo and W, for instance, increases the proportion of silicide intermetallic and allegedly induces stress, but this processing also reduces the grain size of Si, 54,55 rendering its distribution more homogeneous. Rather than suppressing c-Li 15 Si 4 formation by changing the electrode material, a test of the intrinsic effects of c-Li 15 Si 4 on capacity retention would, ideally, involve inducing or preventing its formation by adjusting only the experimental conditions while keeping the electrode material constant.…”

“…The stress–voltage coupling effect has been effectively harnessed to suppress the c -Li 15 Si 4 phase through the application of adhesive layers on thin films and capping layers on a variety of silicon morphologies, ,,,,, as well as alloying silicon with inactive transition metals. ,,− The hypothesis that alloying induces stress, thereby improving capacity retention by suppressing c -Li 15 Si 4 , has been applied to nano- and micron-sized silicon particle electrodes as well as thin films. ,, However, most, if not all previous studies that find a correlation between the suppression of c -Li 15 Si 4 formation and capacity retention, achieve this suppression through material changes that are convoluted with other beneficial effects. For instance, a capping layer on top of a Si film can induce clamping, thereby preventing c -Li 15 Si 4 by aforementioned stress–voltage coupling, while also minimizing reactivity with the electrolyte. ,− Prolonged ball-milling of Si with Mo and W, for instance, increases the proportion of silicide intermetallic and allegedly induces stress, but this processing also reduces the grain size of Si, , rendering its distribution more homogeneous. Rather than suppressing c -Li 15 Si 4 formation by changing the electrode material, a test of the intrinsic effects of c -Li 15 Si 4 on capacity retention would, ideally, involve inducing or preventing its formation by adjusting only the experimental conditions while keeping the electrode material constant.…”

Si-based Composite Anode for Li-ion Batteries with Enhanced Cycle Stability via Doping Cu3Si Phase Achieved by Modified Coating of PDA

“…The introduced element(s) can function as stabilizing the structure of Si anode as well as decreasing its polarization by improving the electronic conductivity. For example, Obrovac's research group did many deep and systematic investigation into this area and they have proved that the composite of Si-M (M = Ni 11 , Cu 12 , Fe 13 , Ti 14 , Mn 15 , Mo 16 and W 17,18 ) can possess good cycle performance and high coulombic efficiency. In addition, some metal oxides can be also considered as promising candidates.…”

Si-based Composite Anode for Li-ion Batteries with Enhanced Cycle Stability via Doping Cu3Si Phase Achieved by Modified Coating of PDA

“…The introduced element(s) can function as stabilizing the structure of Si anode as well as improving its electronic conductivity. For example, Obrovac's research group did many deep and systematic investigations and has proved that the composite of Si-M (M = Ni 11 , Cu 12 , Fe 13 , Ti 14 , Mn 15 , Mo 16 and W 17,18 ) could possess good cycle performance and high coulombic efficiency. In addition, some metal oxides can be also considered as promising candidates.…”