Effects of the phase constitution and microstructure on the electrochemical properties of melt-spun Al_88−X Si₁₂Mn _X anode materials for lithium-ion batteries

Abstract

The phase constitution, microstructure, electrochemical properties, and lithiation mechanism of the melt-spun Al_88−X Si₁₂Mn _X (X = 1, 3, 5, 7, 10, 13, 15, mol%) ribbons were investigated as anode materials for lithium-ion batteries. When X = 1 and 3, the alloys were composed of coarse supersaturated α-Al grains and fine α-Si grains spread along the boundaries, and performed high initial capacities but fast capacity fade. As X was increased to 5 and 7, the constitution of alloys was characterized by nanoscaled α-Al and amorphous regions, and they exhibited capacities of 924 and 764 mAh g⁻¹ initially, 733 and 578 mAh g⁻¹ at the second cycle and then maintained 391 and 351 mAh g⁻¹ after 50 cycles, respectively. When the Mn content was more than 10 %, an intermetallic compound Al_4.01MnSi_0.74 co-existed with α-Al and it evolved into the predominated constitution. The initial specific capacities were very high, but faded rapidly only experiencing few cycles. After lithiation, any compound with Li could not be detected in the Al₈₅Si₁₂Mn₃ and Al₈₃Si₁₂Mn₅ anodes, while the AlLi intermetallic compound could be detected when the Mn content was increased to 13 %. It could be considered that the appropriate phase constitution and microstructure in the Al₈₃Si₁₂Mn₅ and Al₈₁Si₁₂Mn₇ anodes were very beneficial to mitigating structure evolution, improving structure stability, and obtaining favorable electrochemical properties. The Al_4.01MnSi_0.74 compound was an active phase for Li storage in the present system, but it was responsible for serious structure evolution, poor cyclability, and pulverization.