Tuning Inactive Phases in Si–Ti–B Ternary Alloy Anodes to Achieve Stable Cycling for High-Energy-Density Lithium-Ion Batteries

Cycle stability improvement of a high-capacity Si anode is a challenge for its wide application in high-energy-density lithium-ion batteries. Active amorphous/nanosized Si embedded in an inactive matrix is a strategy to improve the cycle stability of Si anodes. Ternary Si100–x–yTixBy (5 ≤ y ≤ x ≤ 20) alloys are designed and prepared by ball milling using elemental Si, Ti, and B as starting materials. The formation sequence of inactive phases during mechanical alloying is predicted by an effective heat-of-formation model and verified by microstructural characterization. The local-fine distribution of free amorphous and nanocrystalline Si in the Si100–x–yTixBy is analyzed by confocal μ-Raman spectroscopy. When used as lithium-ion anodes, the capacity and voltage affected by Si and inactive compounds in the Si100–x–yTixBy are concerned to assess their high energy density. Furthermore, the impact of free active Si, the inactive phase, and amorphous Si on the cyclability of Si100–x–yTixBy is studied. The results show that the Si100–x–yTixBy material is a potential anode for high-energy-density Li-ion batteries and could be used to guide the design of multi-component Si-alloy anodes.