Combinatorial Study of Sn[sub 1−x]Co[sub x] (0<x<0.6) and [Sn[sub 0.55]Co[sub 0.45]][sub 1−y]C[sub y] (0<y<0.5) Alloy Negative Electrode Materials for Li-Ion Batteries

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Abstract
Using combinatorial and high-throughput materials science methods, we have studied thin-film libraries of Sn1−xCox(0<x<0.6)Sn1−xCox(0[Sn0.55Co0.45]1−yCy(0<y<0.5)[Sn0.55Co0.45]1−yCy(0Sn1−xCoxSn1−xCox system is found to be amorphous for 0.28<x<0.430.280.43<x<0.60.43Co3Sn2Co3Sn2 . Amorphous materials with x=0.4x=0.4 show a specific capacity of 650mAh∕g650mAh∕g , but differential capacity, dQ∕dVdQ∕dV , vs potential is not stable vs cycling indicating irreversible atomic-scale changes in the alloy, most likely due to tin aggregation. Adding carbon to this system, for example in the [Sn0.55Co0.45]1−yCy(0<y<0.5)[Sn0.55Co0.45]1−yCy(00.05<y<0.50.05670±15mAh∕g670±15mAh∕g for y=0.05to700±15mAh∕gy=0.05to700±15mAh∕g for y=0.4y=0.4 . Third, compositions with y≅0.4y≅0.4 show differential capacity vs potential curves that do not change during charge-discharge cycling, indicating that such alloys are stable on the atomic scale and hence are extremely good candidates for long cycle life. Stability increases with carbon content up to y=0.4y=0.4 .