Reaction Behavior of a Silicide Electrode with Lithium in an Ionic-Liquid Electrolyte

Abstract

Silicides are attractive novel active materials for use in the negative-electrodes of next-generation lithium-ion batteries that use certain ionic-liquid electrolytes; however, the reaction mechanism of the above combination is yet to be clarified. Possible reactions at the silicide electrode are as follows: deposition and dissolution of Li metal on the electrode, lithiation and delithiation of Si, which would result from the phase separation of the silicide, and alloying and dealloying of the silicide with Li. Herein, we examined these possibilities using various analysis methods. The results revealed that the lithiation and delithiation of silicide occurred.

Impact of the crystalline phase of binary silicide on its lithiation and delithiation properties

“…, FeSi 2 + y Li + + y e − → Li y Si 2 + Fe and/or FeSi 2 + y Li + + y e − → Li y Si + FeSi) occurs and the silicide itself reacts with Li. 34…”

“…It has been previously reported that the silicide phase does not separate into Si and metal and/or Si-poor silicide phases during charge-discharge processes; the reversible capacity is not obtained by lithiation and delithiation of the Si phase. 34 Fig. 7 and 8 demonstrated that the discharge capacity is not correlated with the amount of Si included in the silicide.…”

“…[28][29][30][31][32] With the objective of overcoming the drawbacks of Si for applications as the negative electrode in LIBs, we synthesize pure binary silicides and investigate their charge and discharge properties as well as their reaction. 33,34 We find that some silicide electrodes exhibit a high discharge capacity and superior cyclability in an ionic liquid electrolyte. The discharge capacity correlates with the charge density of transition metals; when the affinity of the transition metal with Li is high, the capacity is high.…”

“…43 Consequently, it can be concluded that no phase separation of silicide (e.g., FeSi 2 + yLi + + ye À -Li y Si 2 + Fe and/or FeSi 2 + yLi + + ye À -Li y Si + FeSi) occurs and the silicide itself reacts with Li. 34 Fig. 7a shows the dependence of the gravimetric discharge capacity of NiSi x (x = 2, 1, 1/2 or 1/3) electrodes on the cycle number in 1 M LiFSA/Py13-FSA.…”

Metallographic Structure Changes in Lanthanum Silicide/Silicon Nanocomposite Electrodes during Lithiation and Delithiation: Implications for Battery Applications

“…42 min). We did not limit the discharging time and set the cut-off voltage at 2.000 V. Herein, we ignored the capacity of LaSi 2 : silicide- and Si-alone electrodes react with Li, ,,, whereas silicide in the silicide/Si composite electrode should be electrochemically inactive in Li . The current density was set at 0.36 A g­( Si ) −1 (0.1 C ) and 1.44 A g­( Si ) −1 (0.4 C ) during the first cycle and subsequent cycles, respectively.…”