| Summary: | The volume expansion during Li ion insertion/extraction remains an obstacle for the application of Sn-based anode in lithium ion-batteries. Herein, the nanoporous (np) Cu<sub>6</sub>Sn<sub>5</sub> alloy and Cu<sub>6</sub>Sn<sub>5</sub>/Sn composite were applied as a lithium-ion battery anode. The as-dealloyed np-Cu<sub>6</sub>Sn<sub>5</sub> has an ultrafine ligament size of 40 nm and a high BET-specific area of 15.9 m<sup>2</sup> g<sup>−1</sup>. The anode shows an initial discharge capacity as high as 1200 mA h g<sup>−1</sup>, and it remains a capacity of higher than 600 mA h g<sup>−1</sup> for the initial five cycles at 0.1 A g<sup>−1</sup>. After 100 cycles, the anode maintains a stable capacity higher than 200 mA h g<sup>−1</sup> for at least 350 cycles, with outstanding Coulombic efficiency. The ex situ XRD patterns reveal the reverse phase transformation between Cu<sub>6</sub>Sn<sub>5</sub> and Li<sub>2</sub>CuSn. The Cu<sub>6</sub>Sn<sub>5</sub>/Sn composite presents a similar cycling performance with a slightly inferior rate performance compared to np-Cu<sub>6</sub>Sn<sub>5</sub>. The study demonstrates that dealloyed nanoporous Cu<sub>6</sub>Sn<sub>5</sub> alloy could be a promising candidate for lithium-ion batteries.
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