Improvement of the Anode Properties of Lithium-Ion Batteries for SiO_x with a Third Element

Abstract

Silicon oxide (SiO x ) has been placed into practical use as an anode active material for next-generation Li-ion batteries because it has a higher theoretical capacity than graphite anodes. However, the synthesis method is typically vapor deposition, which is expensive, and the poor electron conductivity of SiO x restricts high performance. In this study, we prepared M /SiO x active materials consisting of SiO x and a third element ( M = Al, B, Sn) using a low-cost mechanical milling (MM) method and investigated their electrode properties as Li-ion battery anodes. Also, the authors added a third element to improve the conductivity of the SiO 2 matrix. Al, B, and Sn were selected as elements that do not form a compound with Si, exist as a simple substance, and can be dispersed in SiO 2 . As a result, we confirmed that SiO x has a nanostructure of nanocrystalline Si dispersed in an amorphous-like SiO 2 matrix and that the third element M exists not in the nanocrystalline Si but in the SiO 2 matrix. The electron conductivity of SiO x was improved by the addition of B and Sn. However, it was not improved by the addition of Al. This is because Al 2 O 3 was formed in the insulator due to the oxidization of Al. The charge–discharge cycle tests revealed that the cycle life was improved from 170 cycles to 330 or 360 cycles with the addition of B or Sn, respectively. The improvement in electron conductivity is assumed to make it possible for SiO 2 to react with Li ions more uniformly and form a structure that can avoid the concentration of stress due to the volume changes of Si, thereby suppressing the electrode disintegration.

Effect of Sn Addition on the Anode Properties of SiO<i>_x</i> for Lithium-Ion Batteries

“…Detailed conditions were presented in a previous report. 32 To prepare SiO x powder, first, the gas-atomized Si powder and commercially available SiO 2 powder (Kojundo Chemical Lab. Co., Ltd., purity 99.9 %) were weighed at a ratio of 54 : 46 wt%.…”

“…Specific measurement methods and conditions have been described in past papers. 32 Electrochemistry, 90 (6), 067001 (2022)…”

“…The charge-discharge properties are evaluated, and the effect of the addition of the third element M on the anode properties is investigated. 32 Resultantly, the cycle life is improved by adding Sn in particular. As shown in Fig.…”

“…The structure is such that stress owing to the volume change of Si is difficult to concentrate, which limits the disintegration of the electrodes. 32 In this study, the authors have investigated the effect of the amount of Sn on the anode properties, particularly for Sn/SiO x materials with improved anode properties, to further improve the cycle life.…”

Interfacially Enhanced Stability and Electrochemical Properties of C/SiOx Nanocomposite Lithium‐Ion Battery Anodes

“…The Sn/SiO x electrode exhibited the longest cycle life than the addition of B and Al. [22] To use graphene enhanced stability for a commercial silicon anode, Chou and Hwang determined the bonding mechanism and Li diffusivity in Li x Si-graphene systems based upon a calculational approach. [23] Substantially higher mobility along the Si/graphene interface was predicted, which could enable high performance anodes with fast charge/discharge rates.…”