Microsized Sn supported by NiTi alloy as a high-performance film anode for Li-ion batteries

A novel Sn-NiTi composite thin film has been prepared by directly co-sputtering a mixture of pure Sn and NiTi shape memory alloy and has been used as an anode for an Li-ion battery for the first time. The thin film has a unique microstructure of microsized Sn particles and microsized Sn grooves uniformly dispersed in an amorphous NiTi (a-NiTi) matrix. The a-NiTi matrix covers the Sn phase and effectively accommodates the volume change resulting from Li-Sn reactions. It also protects the surface of the Sn particles, thus ensuring good cycle performance of the Sn-NiTi composite thin film electrode, with excellent high-rate capability and a low initial irreversible capacity. It delivered a stable capacity of 503 mAh g(-1) at 1 C and a high value of 372 mAh g(-1) at 15 C, thus demonstrating a significant improvement of the anode performance through the protection of the Sn by the NiTi alloy matrix.