Two‐step dealloying approach to synthesize hierarchically porous nickel‐tin alloy towards long‐life lithium ion batteries

Due to the high theoretical specific capacity and low cost of Sn, developing Sn-based anode materials with long life is the key to their practical applications in lithium-ion batteries. Herein, novel hierarchically porous NiSn alloys with interconnected ligament-channel networks are synthesized via a two-step dealloying strategy, involving corrosion of an Al97.5Ni2Sn0.5 precursor in NaOH, followed by partially etching Ni in HNO3. The architecture of the obtained NiSn-3 h alloy contains the ligaments with the scale of about 115.2 nm and nanowalls with a thickness of several nanometers on the ligament surface, which can enhance the electron/ion transport kinetics and improve the tolerance to volume variation. The NiSn-3h electrode exhibits superior Li storage performance in terms of satisfactory rate performance and excellent cycling stability with a reversible capacity of 213.9 mAh g(-1) at 1 A g(-1) after 1000 cycles. More importantly, the Li storage mechanism of NiSn-3h is unveiled by operando X-Ray diffraction, revealing the formation of lithiation products with low crystallinity at the end of discharge. In addition, on-line differential electrochemical mass spectroscopy is used to detect the gas evolution of the NiSn-3h electrode during the discharge-charge processes.