Influence of structure and atom sites on Sn-based anode materials for lithium ion batteries: a first-principle study

To understand the influence of structure and atom sites on the electrochemical properties of Sn-based anode materials, the lithium intercalation–deintercalation mechanisms into SnNi₂Cu and SnNiCu₂ phases were studied using the first-principle plane wave pseudo-potential method. Calculation results showed that both SnNi₂Cu and SnNiCu₂ were unsuitable anode materials for lithium ion batteries. The Sn-based anode structure related to the number of interstitial sites, theoretical specific capacity, and volume expansion ratio. Different atom sites led to different forces at interstitial sites, resulting in variations in formation energy, density of states, and hybrid orbital types. In order to validate the calculated model, the SnNi₂Cu alloy anode material was synthesized through a chemical reduction-codeposition approach. Experimental results proved that the theoretical design was reasonable. Consequently, when selecting Sn-based alloy anodes, attention should be paid to maximizing the number of interstitial sites and distributing atoms reasonably to minimize forces at these sites and facilitate the intercalation and deintercalation of lithium ion.