Effect of Sn Addition on the Anode Properties of SiO_x for Lithium-Ion Batteries

Abstract

In this study, we have prepared Sn-added SiO_x using a mechanical milling method and investigated the effect of Sn addition on the anode properties of SiO_x for lithium-ion batteries. A charge–discharge cycle test with a charge limit of 1000 mAh g⁻¹ shows that the SiO_x electrode causes a capacity fading loss by 170 cycles. Conversely, it is confirmed that the SiO_x electrodes with the addition of 1 or 3 wt% of Sn maintain a discharge capacity of up to 250 or 360 cycles, respectively, and the charge–discharge cycle life is extended depending on the amount added. Furthermore, the test is conducted by reducing the lithium-insertion amount from 1000 to 750 mAh g⁻¹ to observe the effect of Sn addition. Resultantly, the difference in cycle life is more pronounced, and the discharge capacity of the 3 wt% Sn-added SiO_x is maintained for up to 540 cycles. When the amount of Sn added is as small as 1 wt%, the lithium insertion reaction is locally concentrated because of insufficient electronic conductivity, and Li_3.75Si, with a large volume change, is formed. Resultantly, this electrode causes the disintegration of the electrode and a decrease in capacity. However, in the SiO_x electrode with 3 wt% of Sn, the reactivity of the lithium ions in the SiO₂ matrix is enhanced by the improvement in the electronic conductivity. Thus, the entire active material layer reacts easily and uniformly with the lithium ions. Resultantly, the structure is such that the stress of Si is less likely to concentrate, the damage to the electrodes is reduced, and the electrode disintegration can be suppressed, which is the reason for the enhanced cycle life.